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CHAPTER 2
23
"More than half of the forests are dead or dying from acid rains, .and chemicals in the food chain and in human tissue exceed UC..eptoble limits by several orders of: rnagni tude'!
-The Economist, Feb, 17,1990
ACID RAINS
: THEIR FORMATION AND .MEASUREMENTS
: CASE smDY IN STEEL PLANT AREA
: REACTIVITIES WITH
LIMESTONE
DOLOMITE
MARBLE
SLAG
2.1 INTROWCTIOR
Acid rain. better known as acid deposition, hes become a matter of concern in many parts of the world, particularly in
developed countries. Acidic precipitation in the Adirondack mountains of New York State, in Maine in northern Florida, in
eastern Canada, in southern Norway and in south-west Sweden has been associated with acidification of waters in ponds, lakes and streams with resultant disappearance of animal and plant life(1). Acidic precipitation ( rain and snow) is also believed to have the potential to1 (i) leach nutrient elements from sensitive soils (2), (ii) cause direct and indirect injury to
forest, (iii) damage monuments and building made of stone (3),
(iv) corrode metals and cement products (4).
Sulphur and nitrogen oxides are considered to be the main precursors in the formation of acidic precipitation. Emissions of such compoundsinvolved in acidification are attributed chiefly to the combustion of fossil fuels such as coal and oil. Emi-ssions may occur at ground level as frcm automobile exhaust , or from stacks 1000 feet or more in height. Emissions from natural sources are also imvolved. However, in highly industralized areas, emissions from man - made sources markedly exceed those from natural sources (5). The fate of sulphur and nitrogen
dioxide as well as other pollutants emitted into the atmosphere, depends on their dispersion, transport, transformation and depo
sition. Residence time in the atmosphere, therefore, can be brief if the emissions are deposited locally, or may extend to days
or even weeks if long range transport occurs. Long range tran
sport over distances of hundreds or thousands of miles allows
time for many chemical transformation to occur (1).
Sulphates and nitrates are among the products of the chemical transformations of sulphur oxides (especially so2) and nitrogen oxides (6). Ozone and other photochemical oxid~nts are
believed to be involved in the chemical, processes that · form sulphates and nitrates (7-10). When sulphates and nitrates combine
with atmospheric water, dissociated forms of sulphuric (H2so4)
25
and nitric(HN03) acids resultst and when these acids are brou
ght to earth in rain and snow, acidic precipitation occurs.
Because of long range transport, acidic precipitation in part-
icular state or region can be the result of emissions from
sources in states or region many miles away, rather than from
local sources. An artist's view showing the emissions, trans
formations and precipitations has been given in Fig. 2-1.
Acidic precipitation has been arbitrarily defined
as precipitation with a pH less than s.6,because precipitation
formed in a geo- chemical environment would have a pH of
approximately 5.6 due to the combiningof co2 with water to
form carbonic acid. The acidity of precipitation in nort~astern
United States has been reported to range from pH 3.0 to s .• o; in other regions of United States, precipitation episodes with a pH as low as 3.0 have· also been reported ( 1) •
The· pH of precipitation can vary from
event to event, from season to season and from geogr~hical
area to geogrophical area. Other substances in the atmosphere,
besides sulphur-and nitrogen oxides, can cause the pH to shift
by making it more acidic or more basic. For example, dust and
debris swept up in small amounts from the ground into the
atmosphere may become components of precipitation. At some
places soil particles can be more basic while in others
they tend to be acidic (11). Also,in coasta~reas sea spray
strongly influences precipitation chemistry by contributing
potassium, chloride and sulphate ions. In the final analysis,
the pH of precipitation can be taken as a measure of .. the
relative contributions of all these components (1).
Although acidic precipitation (wet deposition) is
usually emphasized, it is not the only process by which acids
or acidifying substances are added to bodies of water or to
the land. Dry deposition also occurs. Dry deposition processes
include gravitational sedimentation of particles, impactionJ
aerosols and the sorption and absorption of gases by objects
at the earth surface or by the soil or water. Fog and frost are
also involved in the deposition processses but these do not
:Emission
ACID RAIN DEVELOPMENT
Hydrocarbons Aldohydos co so. NO,NOz NH3
2G
SOURCE RECEPTOR FIG. 2 1 REPRESENTATION OF ATMOSPHERIC PR.OCtSSES IN ACID DEPOSITION.
'· \
27
strictly fall into the category of wet or dry deposition (1).
Dry deposition processes are not as well understood as wet
deposition. Howeve~. all of the deposition processes contribute
to gradual accumulation of acidic or acidifying substances in
the environment. The impact of acidic precipitation on aquatic
and terrestrial ecosystem is typically not the result of a single or several individual precipitation events, but rather
the result of continued additions of acids or acidifying substances over time (12). Wet deposition of acidic substances on fresh water lakes, streams and natural land areas is only the
part of problem (13). Acidic substances which exist in gases,
aerosols and particulate matter are transferred into lakes,
streams and land areas by dry deposition as well (14). The
disappearance of fish population from fresh water lakes and
streams is usually one of the most readily observable signs of
lake acidification (15- 17). Death of fish in acidified waters
has been attributed to the modification of a number of physiological processes by change in the pH. In some lakes, concentrations of aluminium may be as crucial or more important than the pH levels as factors causing a decline in fish populations
in acidified lakes (18).
An indirect effect of so2 of potential concern to
human health is the possible contamination of edible fish and
water supplies. Studies in Canada and Sweden reveal high mer
cury concentrations in fish from acidified regions. Lead has
also been reported in acidified water (1). Soils may become
gradually acidified from an influx of hydrogen ions. Leaching
of mobilizable forms of mineral n~ients may occur. The capacity
of soils to absorb and retain anions increases as the pH decr
eases, when hydrated oxides of iron and aluminium ar~present.
Sulphur, like nitrogen, is essential for optimum plant growth.
Plants usually obtained sulphur in the form of sulphate from
organic matter during microbial decomoosition. In soils where
sulphur and nitrogen are the limiting nutrients, atmospheric
sulphur may increase growth of some plant species (1).
28 Other harmful effects of acidic precipitations
include damage to monuments and build.l.ngs made from stones {3), corrosion of metallic structures and deterioration of painted surfaces (1).
ACID PRECIPITATION STUDIES J THE INDIAN SCENARIO
The acid precipitation studies in India have gained momentum during the last decade after the adverse effects of this phenomenon as studied in other countries were understood and their implications realised. The effect of atmospheric
acidity on the building stones of Chittorgarh Fort were studied in detail (19,20). Joshi et al. analysed sulphate and
other anions in aerosols in the ambient air around the Taj Mahal at Agra ( 21) • Khemani and others analysed cations par
ticularly Ca(II) and sulphate in rain water samples around
a coal - fired power plant (22). The pH levels of rain water have been studied and reported by several workers (23-32). Varma inferred that the rain water at the particular place possesses all the fundamental characteristics of the nearby
soil. He also prepared iso-pH curves for India on the basis
of the pH values of rain water studied by hlm and other
workers on the basis of data collected during a period of 11 years (11). He found that northwest India experienced high
pH values ranging between 7.0 - 8.5 while the southeast Indian a
c~tal belt represented a region of low pH (5.5) which may
be taken as a potential region of acid rain occurre.nce. Srini vas n
Rao and eoworkers studied the tr~sformation of so2 at Vishakha-
patanam and Nagpur in pre- monsoon and monsoon seasons (33).
Raviprakash et al. studied the rainfall acidity in Talcher area during 1983 - 86 , and also the ecological effects of
the acid precipitation on biological materials (34). Durga
Prased and coworkers found a marked dependence of so2 -
concentrations on relative humidity. He foUnd that hLghex relative hum~dity quickly oxidised the so2 resulting in
decrease in its ooncentration (35).
2D In the work being reported here, the levels of
so2 and NOx in the atmosphere in the vicinity of a steel plant at Bhilai ( M.P ) arising from massive but• · ''g of coals have been determined.
2.2 S02 AND NOx AS CON'l'Rl:BIJTORS OP ACID RAXNS 1 'DIBIR
lii!OI'U:TORIRG XIIIJ A STEEL PLAIIT AREA
:XNTRODUCT.Ia'f
The era of modern iron and steel making began in India
more than 150 years ago when the first blast furnace was setup in Madras in 1830, The installed capacity of inQot steel envisaged in India by 2000 A,D, is 75 million tonnes,
In the work being reported here • the levels of so2,Nox and SPM have been d~termined around a steel plant located at
Bhilai M,P,, India. The production of saleable steel at this plant during 1988 - 89 was more than 2,5 million tonnes.
The production growth of steel at this plant during the period from 84 - 85 to 88 - 89 has been shown in Fig, 2 - 2. The consumption of coal at the plant during the 1988 - 89 has been more than 3,6 million tonnes (36), This massive
burning of coal during the steel making is bound to emit
large quantities of so2, NOx and SPM in addition to co , co2 and hydrocarbon gases. There are four major processes in
steel making which contribute gaseous pollutants to the
atmospheric air 1 coking , sintering , melting and scarfing,
Nearly all the coke used is produced in the byproduct ovens.
The so2 factor in the gaseous pollutants emitted by a steel
plant becomes more important in view of the significant presence of sulphur in Indian coals (37),
The air quality measurements of the Bhilai Steel Plant
30
~ 2600 lfl w z 2500 Z· 0 f-0 2400 z <( lfl ~ 2300 0 :r: 1- 2200 .......
I
/ I I
z 0 2100 -1-u
/ -----v
~ 2000 0 0 a: Q. 1900
I
I I
1800 84-85 85-86 86-87 87-88 88-89
(YEARS) FIG.2-2. GROWTH OF STEEL PRODUCTION
AT BHILAI.
31
area where carrie~ut by setting up four sampling stations, three within a radius of 5 Km and one within a radius of 10 Km in the south , west and north directions with respect to the steel plant as shown in Fig. 2 - 3. Sampling station in the east of the steel plant was not 1etup in view of the wind direction which was unfavourable for the transport of
at each season1
emitted pollutants towards this area. The monitoring ~ampling site was carrieqbut for one month in each ~n december in winter • rtarch in summer and July in rainy
sampler sa~apling
season). For air monitoring, a high volume air (Envirotech Model APM 4120) was operated at each ~ite for eight hours a day following the recommended conditions of operation (38). Whatmana glass microfilter sheets of retention efficiency of 99.99 % ( for 0.6 pm particles) were used with the air sampler. The meteorological data ( temperature • rainfall • humidity , wind direction , wind velocity ) of the area of study for the relevant period have been shown in Table 2 - 1. For so2 and NOx determinations , solutions of tetrachloromercurate (o.1 M) and sodium hydroxide ( 0.1 M ) were placed respectively in impinger- bottles of the sampling machine as absorbing reagents. The concentr• ations of so2 and NOx were determined spectrophotometrically by measuring the absorbance at 560 nm for so2 and 540 11111
for NOx• For NOx determination • the use of 1 - nephthyl• ethylene diamine tetraacetic acid ( NEDA ) solution was made ( 39 , 40 >.
The results obtained have been shown in
Table 2 - 2. The mean values of SPM , so2 , NOx at site in each season have been shown in Table 2-3.
RESULTS AND mscuss:rc.
each
The results obtained ( Tables 2 - 2 & 2 - 3 ) have provided following informations : (1) The SPM concentration~ave shown a decrease with
o'~t.t<S) \c.ov..t.. • • • • •• • • •
"o"" \.. •• • C"r- ""\0 • \\ '-'~"'. <t· • "p. ;' • ·'--~ .• .._, • tl:"-v;J
OPEN LAND
. •,;:-. . ) •-.::' ,s.~'· •
-----.....----- ........... /POPULATED AREA'
I ) \ / ..... _________ .....
I I I \
' .....
32
• MAJOR EMISSION POINT
..._FACTORY PRE:MISES
~AGR,ICUL TURAL LAND
TOWN SHIP
----- -COMMERCIAL
CUM .RESIDENTIAL ARIA
- -----
..... '
/
\ \ \ I I I I
I I
/
FIG. 2-3. THE AIR- MONITORING SITES IN STEEL PLANT AREA.
Tab
le 2
-1
ME'
HO
RO
LOG
ICA
L M
D O
P m
E S
'l'OD
Y A
REA
Mon
th
Tem
per
atu
re
Rain
fall
H
llm
±di
tz
Win
d V
elo
cit
v
Max
M
in
,. M
ax
Min
M
ax
Min
-<
•c)
( •c)
(m
m)
(%)
(%)
(Rm
,lhr)
(I<
rn/h
r)
sep
tem
ber
3
3.6
2
3.4
3
58
.9
100
63
12
.45
3
.66
(1
99
0)
Octo
ber
32
.6
20
.0
17
9.7
10
0 42
9
.19
2
.87
Nov
embe
r 3
2.0
1
8.8
1
2.6
95
48
1
0.9
1
3.2
1
Dec
emb
er
29
.2
14
.6
5.5
95
61
6
.18
3
.03
Ja
nu
ary
3
1.8
1
0.6
2
6.0
10
0 45
1
0.1
3
2.9
9
(19
91
)
Feb
ruary
3
5.2
1
8.8
o.
s 8
4
29
10
.19
3
.65
Mar
ch
40
.0
19
.0
14
.3
90
16
1
0.0
8
4.0
3
Ap
ril
41
.8
23
.2
12
.6
77
1
1
12
.68
4
.26
May
4
3.8
3
0.4
o.
s 58
1
3
12
.12
5
.46
Jun
3
7.4
2
3.8
7
1.8
91
21
1
7.4
9
5.5
0
Ju
ly
36
.0
22
.8
33
3.9
10
0 53
1
9.3
4
4.3
7
Au
gu
st
31
.4
22
.0
29
2.9
10
0 63
1
3.3
6
8.6
0
Win
d D
irecti
on
So
uth
west
erl
y
Irre
gu
lar
No
rth
west
erl
y,n
ort
heast
erl
y
No
rth
west
erl
y,n
ort
h e
ast
erl
y
West
erl
y,n
ort
h w
est
erl
y
So
uth
west
erl
y,n
ort
h w
est
erl
y
So
uth
west
erl
y,n
ort
h w
est
erl
y
No
rth
west
erl
y,s
ou
th w
est
erl
y
Irre
gu
lar
So
uth
west
erl
y
So
uth
west
erl
y,n
ort
h w
est
erl
y
So
uth
west
erl
y,n
ort
h w
est
erl
y
c.;,
c.,
Tab
le
2-2
A
IR M
CIIU
TOR
l:NG
D
ATA
OF
TH
E
ST
EE
L P
LAN
T A
REA
Mo
nth
an
d
Du
rati
on
of
Flo
w ra
tes
Vo
lum
e W
eig
ht
co
ncen
trati
on
s
Day
S
am
pli
ng
F
Or
SPM
F
Or
so2/N
OX
O
f-]>
.ir
of
SPM
SP
M
so2
NO
X S
amp
led
( 19
90
-91
) (M
in.)
(m
3 /min
) (
L /m
in)
{m3)
.
(g)
(p.g
/m3)
()
lg/m
3)
{)lg
/m3)
sam~lin2 S
ite N
o.
1 (P
ow
er H
ou
se A
rea)
Dec
1
47
6
1.1
0
0.2
0
52
3.6
0
.37
7
20
1
00
4
7
3 4
76
1
.10
0
.20
5
23
.6
0.2
0
34
0
60
9
6
5 4
80
1
.10
0
.20
5
28
.0
0.3
3
63
8
90
1
45
7
48
0
1.1
3
0.2
0
54
2.4
0
.31
5
79
1
40
1
30
9
48
0
1.2
1
0.2
0
S8
o.o
0
.24
4
07
6
0
12
1
11
4
80
1
.13
0
.20
5
42
.4
0.2
1
39
0
15
0
90
1
3
47
9
1.1
5
0.2
0
sso
.a
0.2
0
31
0
45
3
3
15
4
80
1
.15
0
.20
5
50
.8
0.2
8
51
0
so
75
Mar
ch
17
4
60
1
.13
0
.20
5
39
.0
0.3
3
62
0
74
5
4
19
4
80
1
.14
0
.30
5
47
.2
0.4
2
77
0
19
5
76
2
1
48
0
1.2
1
0.3
0
58
0.8
0
.46
-7
90
1
09
9
4
23
4
80
1
.12
0
.20
5
37
.6
0.3
2
60
5
13
9
12
4
25
48
0
1.1
3
0.2
0
54
2.4
o
.17
5
20
1
47
1
35
2
7
48
0
1.1
1
0.2
0
53
2.8
0
.30
5
74
1
90
1
70
2
9
47
9
1.1
0
0.3
0
52
8.0
o
.27
5
10
1
30
1
15
JUly
1
48
0
1.1
2
0.1
0
53
7.6
o
.o4
8
0
35
27
3 4
79
1
.13
0
.10
5
41
.3
o.o
4
70
2
9
21
5
47
9
1.1
2
0.2
0
53
6.5
o
.o5
1
00
3
9
33
7
48
0
1.1
1
0.2
0
53
2.8
o
.o5
1
00
1
7
15
9
48
0
1.1
3
0.2
0
54
2.4
0
.06
1
10
2
9
19
1
1
46
0
1.1
3
o.2
0
54
2.4
· o
.o5
9
0
45
3
3
13
4
79
1
.11
0
.20
5
31
.6
0.0
4
70
4
0
31
"" 1
5
48
0
1.1
2
0.2
0
53
7.6
o
.o3
6
0
35
2
9
... C
On
t.
Tab
le
2-2
o
on
td.
Mo
nth
an
d
DU
rati
on
of
Flo
w ra
tes
Vo
lum
e o
f W
eig
ht
co
ncen
trati
on
s
Day
S
am
pli
ng
A
ir s
am
ple
d
of
SPM
>
Fo
r S
PM
F
or
S0
2/NO
X
SPM
so
2 N
Ox
(19
90
-91
) (M
in)
(m3 /m
in)
(.t.
/min
) (m
3)
(g)
(Jlg
/m3
) ()
lg/m
3)
()lg
/m3
)
Sam
pli
ng
Sit
e N
o.
2 (J
ora
tara
i A
rea)
nee
1 4
80
1
.11
0
.20
5
32
.8
o.o
4
78
1
8
18
3
47
9
1.2
5
0.2
0
59
8.7
0
.10
1
69
25
9
5 4
80
1
.25
0
.40
6
00
.0
0.1
8
31
0
49
so
7
48
0
1.1
0
0.2
0
52
8.0
0
.34
6
50
4
5
32
9 4
80
1
.13
0
.20
5
42
.4
0.2
0
36
9
16
1
9
11
4
80
1
.12
. 0
.20
5
37
.6
0.1
2
21
7
15
3
9
13
4
80
1
.11
0
.20
5
32
.8
0.0
6
12
0
14
21
1
5
47
7
1.1
0
0.2
0
52
4.7
o
.o6
1
24
1
9
24
Mar
ch
17
4
77
1
.13
0
.20
5
39
.0
0.3
4
62
9.
29
51
1
9
48
0
1.1
4
0.3
0
54
7.2
0
.23
4
26
1
3
17
2
1
48
0
1.2
1
0.3
0
58
0.8
0
.41
7
11
4
4
39
2
3
48
0
1.1
2
0.2
0
53
7.6
0
.17
3
15
4
2
14
2
5
48
0
1.1
3
0.2
0
54
2.4
o
.o7
1
26
3
6
38
27
4
80
1
.11
0
.20
5
32
.8
0.2
8
41
2
22
2
9
29
4
80
1
.10
0
.30
5
28
.0
0.2
8
52
9
27
2
6
July
1
48
0
1.1
2
0.2
0
53
7.6
o.
os
10
0
15
7
3 4
79
1
.12
0
.10
5
36
.5
o.o
5
90
1
4
16
5
48
0
1.1
3
0.3
0
54
2.4
0
.06
1
20
1
5
4 7
48
0
1.1
3
0.2
0
54
2.4
0
.06
1
10
e
9 9
48
0
1.1
3
0.2
0
54
2.4
0
.04
so
4
2 1
1
47
9
1.1
3
0.2
0
54
1.3
0
.06
1
20
1
2
7 C
o 1
3
48
0
1.1
3
0.2
0
54
2.4
o
.o5
1
00
7
10
en
1
5
48
0
1.1
2
0.2
0
53
7.6
o.
os
10
0
8 6
Tab
le
2-2
co
ntd
.
Mo
nth
an
d
Du
rati
on
o
f
Flo
w r
ate
s
vo
lum
e o
f W
eig
ht
co
ncen
trati
on
s
Day
S
am
pli
ng
A
ir
Sam
ple
d
of
SPM
Fo
r SP
M
Fo
r S
O;/
NO
X
SPM
so
2 N
OX
(19
90
-91
) (M
in)
(m3 /m
1n
) (I
;/m
in)
(m3)
(g
) (p
g/m
3)
(Jlg
/m3
) (p
gfm
3)
Sam
pli
ng
Sit
e
No.
3
(Secto
r 4
, B
hil
ai
Are
a)
Dec
1
48
0
1.1
0
0.2
0
52
8.0
0
.36
6
80
2
9
16
3
48
0
1.1
3
0.1
5
54
2.4
0
.31
5
70
1
2
27
5 4
79
1
.13
0
.20
5
41
.2
0.0
7
12
2
38
1
5
7 4
77
1
.20
0
.20
5
72
.4
0.2
1
36
0
42
so
9
471
1.2
1
0.2
0
56
9.9
0
.44
7
79
1
7
27
1
1
48
0
1.2
2
0.2
0
58
5.5
0
.41
7
10
2
1
10
1
3
-4
80
1
.22
0
.20
5
85
.6
o.1
o
17
0
40
3
8
15
4
79
1
.13
0
.30
5
41
.2
0.1
1
21
0
42
4
9
Mar
ch
17
4
80
1
.10
0
.20
5
28
.0
0.2
1
41
0
35
2
7
19
4
80
1
.10
0
.20
5
37
.6
0.2
2
41
2
46
6
9
21
4
80
1
.10
o
. 20
5
37
.0
0.1
7
31
5
2 1
20
2
3
48
0
1.1
3
0.2
0
54
2.4
0
.13
2
40
2
8
4 2
5
47
9
1.1
2
0.2
0
53
6.4
0
.22
4
12
6
6
61
2
7
48
0
1.1
1
0.3
0
53
2.8
0
.03
6
4
29
2
9
29
4
80
1
.10
0
.20
5
37
.6
0.0
6
71
0
16
2
48
4
JUlY
1
47
7
1.1
1
0.2
0
52
9.5
0
.19
3
60
1
8
15
3
47
7
1.1
2
0.2
0
53
4.2
' 0
.13
2
50
2
5
19
5
47
8
1.1
2
o.2
o
53
5;.
5
o.u
2
70
1
5
9 7
48
0
1.1
2
0.2
0
53
7.6
0
.09
1
70
2
1
12
9
48
0
1.1
1
0.2
0
5!3
2.8
o
.o9
1
80
1
2
8 11
4
80
1
.13
o
.1o
5
42
.4
0.1
0
19
0
14
7
13
4
80
1
.13
o
.2o
5
32
.8
0.1
0
19
0
13
_9
15
4
80
1
.12
0
.20
5
32
.8'
o.o
a
15
0
17
11
C
.:l
c::
con
td.
Tab
le
2-2
co
ntd
.
Mo
nth
an
d
Du
rati
on
of
Flo
w ra
tes
vo
lum
e o
f W
eig
ht
co
ncen
trati
on
s
Day
S
am
pli
ng
A
ir s
am
ple
d
of
SPM
Fo
r SP
M
Fo
r S
02/
NO
x
SPM
so
2 N
OX
(19
90
-91
) (M
in)
(m3 /m
in)
(L /
min
) (m
3)
(g)
(pg
/m3
) 3
(pg
/m
) 3
(pg
/m
)
Sam
pli
ng
sit
e N
o.
4 (H
UD
CO
S
ecto
r)
Dec
1
48
0
1.1
3
0.1
0
54
2.4
0
.15
2
84
N
D
17
3
47
7
1.1
3
0.1
0
53
9.0
0
.20
2
75
4
25
5
48
0
1.1
1
0.1
0
53
2.8
o
.os
90
N
D
12
7
47
0
1.1
0
0.2
0
51
7.0
o
.os
15
0
5 4
5
9 4
80
1
.13
0
.20
5
42
.4
0.2
2
39
8
ND
3
7
11
4
80
1
.13
0
.20
5
42
.4
0.2
7
49
4
7 2
6
13
4
79
1
.13
0
.20
5
41
.2
0.2
2
40
5
ND
1
2
15
4
80
1
.13
. 0
.20
5
42
.4
o.o
6
12
0
4 3
2
Mar
ch 1
7
48
0
1.1
5
0.2
0
55
0.8
0
.06
1
10
N
D
22
1
9
48
0
1.1
0
0.2
0
52
8.0
0
.12
2
40
5
16
21
4
80
1
.15
0
.30
5
28
.0
0.2
0
37
0
7 1
7
23
4
79
1
.15
0
.10
5
50
.8
o.o
s
94
N
D
29
2
5
48
0
1.1
5
0.2
0
55
2.0
0
.22
4
00
8
39
2
7
48
0
1.1
0
0.5
0
55
2.0
0
.23
4
29
N
D
33
2
9
48
0
1.1
2
0.2
0
52
8.0
0
.22
4
15
4
25
Ju
ly
1 4
80
1
.13
0
.10
5
42
.4
o.o
3
60
N
D
8 3
48
0
1.1
1
0.1
0
53
2.8
0
.04
7
0
ND
1
2
5 4
78
1
.11
o
.1o
5
30
.6
O.Q
2
40
N
D
4 7
48
0
1.1
1
o.2
o
53
2.8
0
.02
4
0
ND
7
9 4
80
1
.12
0.
2{1
53
7.6
o
.o5
1
00
N
D
3 1
1
4.79
1
.12
0
.20
5
36
.5
0.0
3
so
ND
N
D
13
4
77
1
.13
0
.20
5
39
.0
o.o1
3
0
ND
N
D
15
4
77
1
.11
0
.20
5
29
.5
0.0
2
40
N
D
ND
C
o;)
~
co
ntd
•
. ,
Table 2-3 COII1CENTRATl:OIII LEVELS OF POLUJTARTS IN '1'HE .AHBXEH'l' AIR OF STEEL PLART
Month of Sampling* Distance Mean Values Sample Site NoS. from Collection steel plant SPM so2 ·NO X
(IQII) (pg/m3) (pg/m3) (Jlg/m3)
nee (1990) 1 3.0 486.75 93.12 29.30 2 3.0 254.62 25.12 26.50 3 5.0 450.12 30.12 29.00 4 10.0 289.50 5.00 25.75
March{1991) 1 3.0 548.62 123.00 96.00
2 3.0 449.71 30.42 30.57
3 5.0 332.12 50.62 102.87
4 10.0 296.00 6.60 24.12
July {1991) 1 3.0 8s.oo 33.60 26.00
2 3.0 102.50 10.37 7.62
3 5.0 220.00 16.87 11.25
4 10.0 53.75 NO 4.25
*(Locations Shown in Fig. 2-3) , ND denotes not delectable
:w
increase in distance from the emission sources. The SPM
values at sampling site nos. 1 • 2 and 3 ( dist<.'nce within 5
Km ) have been found to be larger than t·hose at site no. 4 ( distance about 10 I<m ) du:·ing the enUre period of air
monitoring • It has been found that the SPM concentrations at the four sampling sit•s which all are located at residential areas are higher than the limit ( 200 pg I m3 ) prescribed as per Indian Standards (41). The levels have been found to be within the prescribed limit at site nos 1,
2 and 4~only during the month of July during which a high rainfall ( 333.9 mm ) was recorded. The impact of this steel
industry on the air qual! ty • in terms of 5PM load 1 is thus obvious.
(2) The 502 level in the ambient air has also been found to
be higher at sampling sites situated within 5 Km distance from the steel plant compared to that situated at a distance of 10 Km. During all the three months of air monitoring,the so2 levels have been found to be highest at sampling site no. 1 ( situated in the north direction with respect to the steel plant). This is on account of the northerly trend of the wind direction during all the three months ( Dec.,March and July ) of air monitoring. The 502 levels have been found
to be considerably diminuted during the high rainfall period of July at all of the sampling locations ( Table 2 - 3 ) •
The mean values of 502 at site no. 1 have been found to be
exceeding the prescribed limit during the months of December
and March 1 on the 8 - hourly basis of measurements.At site
no. 3 , the exceeding of the limit has been found to be only
occasional.
(3) The NOx level at site nos. 1 and 3 ( Fig. 2 - 3 ) during
the month of December has been found to be almost equal due
to the northerly trend of wind direction during this month
(Table 2·- 1 ). The westerly trend of the wind direction
during the mo•>th of March has been round to affect site no. 3
40
most significantly on account of its location in the west
of the steel plant 1 and its close proximity with the
emission sources such as coke ovens 1 blast furnaces and
the steel melting shops of the steel,plant {Fig. 2- 3 ). As in the case of SPM and so2 , the concentration of NOx during the high rainy month of July has been found to be
considerably lowered. The mean values of NOx obtained on
eight hourly basis of measurement have been found to exceed the prescribed limit only in the month of March at
site nos. 1 and 3 {41).
2.3 A C :I D R A X N S 1 S T V D :I E S :I II S T E lit L * :IliiDUSTRY AREA
Steel manufacture is considered to be quite significant amongst heavy industries. The world steel productions during the years 1984 and 1985 have been reported to be 709.2 and
719.9 million tonnes respectively. (42). Steel productions
in India during the same years have been reported as 10.5
and 11.1 million tonnes respectivelly (42). A total of 1.4
tonnes of solid materials of inorganic nature is handled
during the production of one tonne of steel (43). Coal
forms an important segment of the raw materials used in
steel making. Block and Dams have reported the presence of
as many as 46 elements in coals (~4). Klein and Russel
have studied the enrichment of heavy metals in land areas
in the vicinity of a major coal burning unit (45). In the
back-ground of the above observations , deviations in the
normal characteristics of rain water , arising from the
effects of the emissions of gases and particulate matter
from the steel plant can reasonably be expected in the
vicinity of the steel manufacturing industry.
* "Rain Water Characteristics in the Vicinity of a steel Plant in India", 1\cid MagAzine , Sweden.(Paper communicated).
41
The area selected for the study of rain water characteristics is Bhilai ( Dist. Durg , M.P. ) where an integrated
steel plant of an annual production capacity of 4.0 million tonnes is located. The environm~ntal impacts of this steel plant have been studied and report~d by earlier workers • The fallout rates of settleable dusts in the vicinity of
I
this plant have been reported to be in the range of 60.63 -836.18 tonnes/km21 month (46). The lead content in the fallout matter was reported to be in the range of
301.60 mg I kg (47). During a surveillance check, 119.3 -
the 3 presence of mercury in the range of 0 - 3 pg I m has been
reported in· the atmospheric air of this area (48). so2 and
NOx have generally been identified as the key gaseous
pollutants to impart acidity to the rain water. The concen-
tration level of these two gases upto a radius of 10 Km around this steel plant have been studied in each season of a year, and the results have been shown in the preceding section. In the work being reported here , some key parameters 1 namely pH , TDS , Chloride , Sulphate , Nitrate , Pb 1 H9 , Na and K in the rain water samples collected in the vicinity of the
above stated steel plant during a twelve~month cycle have
been determined to evaluate the impact of the steel industry
on the rain water in this area.
MATERIALS AND METHOIE
Sample collectiop : Four sampling sites 1 each at a distance
of o.s Km from the steel plant were selected in the four
directions around the steel plant (Fig. 2- 4 ). Precipitation samples were collected in the bottles using polythene
funnels ( dia- 20.0 em) (49). The funnels and the bottles
were thoroughly cleaned with warm dilute nitric acid • and
then rinsed with double-distilled water. The funnel collectors
( 1)
OPEN LAN!J
-- ---- ..... ~~ ... /POPULATED AREA\
I I
' / .... _________ ..,
I I
I \
'
• MAJOR EMISSION POINT
..._FACTORY PRt;:MISE:S
~AGRICULTURAL LAND
TOWN SHIP
------' ' ' \
COMMERCIAL CUM
RESIDENTIAL ARIA
' I
.... ~ - -- -----
I I
I
I I I
FIG. 2-4' THE LOCATIONS OF RAIN - WATER SAMPLING IN STEEL
PLANT AREA
42
were placed about a meter high in open areas
care to avoid any splash contamination, In those
43 taking
cases
where more than one sampling bottle was needed at a parti
cular site , due to excessive rainfall , the contents
of all these bottles were composi ted on equal
volume basis, At the close of each month , the samples were
brought to laboratory for investigations,
Procedure 1 The key parameters in the
were determined as follows 1
collected samples
(1) pH 1- The pH values were measured using a digital pH meter ( Century, Model CP- 901 ), after calibration using
standard buffer solutions (SO)
(2) Conductance 1- The conductance of the samples was
measured using a digital conductivity.meter ( Century Model
CK 710 ), The conductivity cell was rinsed with the sample
water before each measurement (SO).
(3) Total Dissolved Solids ( TDS ) 1- Aliquots of the
samples ( 10 ml each ) were filtered through a glass fibre
disc , 111ashed thrice with distilled water and the filtrates
were evopa~ated to dryness in evaporating dish and then
heated in an oven at 105 °C till constant weights were ob
tained._ (50) •
(4) Sulphate 1 The sulphate was determ~ned turbidimetrically
using a turbidimeter ( Systronics Nephelo - turbidimeter
Model 131 }, Aliqouts ( 100 ml each) of the samples were
taken in a 250 ful Erlenmeyer flask. 5,0 ml of a condition
ing reagent prepared by mixing 50 ml glycerol , 30,0 ml
concentrated HCl 1 300 ml of distilled water , 100 ml 95 %
ethyl alcohol and 75 g NaCl was then added,One spoon full
of BaC12 crystals was then added and magnetically stirred
for one minute. The solution was placed in the absorption
cell of the instrument immediately, and the reading was
recorded after four minutes. A calibration
pared usi~g a standc~d sulphate solution
graph was
prepared
pre
by
dissolving 149.9 mg anhydrous Na2so4 in distilled water and diluting to one litre ( l.oo ml •·100 pg so;-) (50>.
( 5) N:l.trete '- The determinations were made spectrophotometrically usi,!'lg phenoldisulphonic acid. Aliquots ( 20 ml each ) were taken , and nitrites were first removed by heating with ammonium sulphate. The sample solution was eva.porated to dryness in a water bath , 2 ml of phenoldisulphonic acid was addedt0 the dry residue and mixed. This was followed by addition of 10 ml of distilled water and
seven ml of concentrated ammonia solution. The solution was
made up to 100 ml. The absorbance of the solution was measured at 410 nm. The reagent was prepared py dissolving 25 g
of colourless phenol in 75 ml of fuming sulphuric acid and then heating to 100 °C for two hours. The calibration graph
was prepared by dissolving 0.07220 g of dry potassium nitrate in one litre of distilled water ( 1 ml a 0.044 mg No; )(S1l.
(6) Calcium and Magnisium 1- Aliquot ( 50 ml) of the sample was taken in an Erlenmayer flask , 1.0 ml of a buffer solution ( pH 10.0 ) prepared by adding 142.0 ml of concentrated
ammonia solution ( sp. gr. 0.88 - 0.90 )to 17.5 g ammonium chloride and diluting to 250 ml with distilled water was
added. Few drops of Eriochrome Black T indicator prepared by dissolving o. 2 g of the dyestuff in 50 ml of triethanol
amine and s.o ml of absolute alcohol , were added. The
solution was then titrated using a standardized solution ( 0.01 M) of EDTA ( disodium salt l. From the titre value,
2+ 2+ the concentrations of Ca and Mg were calculated • For
determining the concentration of ca2+ , another aliquot (SO
ml ) of the sample was taken , 10 ml of 8 M KOH solution and 1 g of Patton and Reeder's indicator mixture prepared by
mixing together the dyestuff and sodium sulphate in a ratio of 1:100 ( by weight ) were added. The solution was · then
titrated using standardized ( 0.01 M ) EDTA(disodium salt )
solution. From the titre value , the concentration of Ca(II)
in the sample was calculated. The concentration of Mg (II)
in the sample was then found out by taking the difference of the two titre values (52).
( 7) Sodf.u. and PotassiUJD 1 An aliquot ( 50 ml ) of the filtered sample was placed in a beaker and then aspirated into a flame photometer ( Systronics Model Digital FPM 125). The sodium amd potassium filters were used for the respective determinations of these metals. Calibration graphs for
sodium and potassium were prepared by using standard
solutions of their metals prepared by dissolving 2.542 g
and 1.909 g of NaCl and KCl respectively-in one litre of
distilled water.{ 1 ml = 1 mg Na, 1 ml = 1 mg K) (52).
(B) Lead :- An aliquot ( 50 ml ) of the sample was acidified
with concentrated HN0 3 to a· pH of 2.0. The sample was then filtered. 10 ml sodium tartrate solution ( 10 % ) and 5
drops of thymol blue indicator solution ( 0.4 % in water ) were added. Concentrated NH40H was then added to make the
indicator true blue. This was followed by the addition of
10 ml KCN solution ( 10% ). The pH was adjusted to s.s. Lead was then extracted using 5 ml portions of dithizone
solution prepared by dissolving 250 mg dithizone crystals
in 50 ml chloroform. The mixture was shaken well and the
solvent layer transferred to another separatory funnel·.
Successive extractions using 2 ml portions of dithizoEe
solution were made until' the green colour of dithizone
solution persisted for two extractions. The extracts were
transferred to a volumetric flask , and the volume made up
by using chloroform. The absorbance was measured at 520 nm
using chloroform as a reference. A blank was also carried
out and the absorbance of the blank was substracted from
that of the sample reading. A calibration graph was
prepared by dissolving 0.160 g Pb(No3>2 in one litre lead-
4U
free distilled water ( 1 ml • 0.1 mg Pb ) (so>.
( 9) Mercury a- Mercury was determined by anodic striping
voltametery. All glass-wares used in this determination were
soaked with nitric acid ( 111 ) prior to their use in the
mercury determination. The determinations were made using a voltameter ( Chemtronic Model PDV 2000 ) by following the
recommended conditions of operation (52).
All the chemical reagents used were BDH
(AnalaR grade). The water used was doubly distilled and
deionised. The glasswares used were supirior quality boro
silicate.
The results obtained have been shown in
Table 2 - 4. The variations in the values of the selected key parameters ( pH , TDS , Pb and Hg ) in the rain water
collected at the four sampling sites each month from
February to September have been shown in Fig. 2 - s. During
the period from October to January , no rainfall occurred at
the sampling sites in the area of the study.
RESULTS AJID mswssxm
Parameterwise the observations
found to be as follows :
have been
(1) pH 1- The pH values of the rain water within the 20X20
Km stretch of the steel plant area have been found to differ
from site to site ( Fig. 2 - Sa). The pH values of the rain
water at the same site have also been found to differ from
month to month. The pH range of the rain water in the entire lowest . area has been found to be within 5.6 - 8.1 , the value be1ng
A observed at site no. 4 which is susceptible to receive
Tab
le
2-4
!~:TAILS
Cli'
RU
!i
FA
LL
A
HD
A
NA
L=
s ~
OF
R
AL
R W
ATE
R
Mo
nth
o
f
Rain
fall
S
"""P
le
~ring
the
samp~ing
pH
::::
Ond
u-T
DS
so--
NO
-ca
++
M
g++
N
a+
K+
pb
++
H
g+
• C
cll
ec:t
ion
M
on
th
Sit
e
No*
cta
nce
4 3
(Yr
19
91
) (n
mt)
(!
-ti.
OS
) (m
g/1
) (m
g/l
) (m
g/1
) (m
g/1
) (m
g/1
) (m
g/1
) (m
g/1
) C
po
/1)
(,..
Wl)
Feb
x:u
ary
0
.8
1 6
.90
5
3.1
2
7.0
1
.5
o.1
1
2.0
5
.0
2.5
s.o
1
0.0
1
.5
2 7
.70
2
9.2
1
4.7
1
.0
0.2
6
.2
2.1
2
.0
3.0
2
00
.0
2.5
3
7.5
0
so.o
4
0.1
3
.0
0.2
-
21
.5
6.0
5
.0
4.5
5
90
.0
16
.0
4 6
.,0
1
90
.,3
4
5.0
3
.5
o.a
2
5.0
a.o
5
.5
2 ..
::i 7
10
.0
10
.0
Ma
rch
1
4.3
1
6.9
1
61
.0
30
.0
1.5
o
.1
18
.1
6.2
1
.5
2.0
3
0.0
1
.0
2 7
. 71
3
0.0
1
5.8
3
.o
0.2
6
.1
1.9
3
.0
1.5
2
50
.0
B.O
3
7.6
0
89
.1
44
.2
3.0
0
.4
11
.9
6.7
1
5.0
e.o
5
50
.0
14
.0
4 6
.00
8
6.,
7
43
.3
2.5
0
.1
21
.2
7.2
7
.5
9.5
6
50
.0
9.0
Ap
ril
12
.6
1 7
.10
6
0,5
3
0.2
1
.5
0.1
1
1.7
4
.1
7.5
6
.0
60
.0
1.1
2
7.7
0
34
.1
16
.9
2.0
0
.1
5.2
2
.1
3.0
3
.0
30
0.0
9
.0
3 7
.95
8
8.4
4
4.2
3
.5
0.2
H
.1
4.1
1
1.5
1
0.0
8
0o
.o
16
0.0
4
6.0
7
82
.3
40
.1
1.0
o
.1
26
.3
8.7
3
.5
1.5
6
10
.0
3.5
M"Y
o
.a
1 7
.10
7
9.,
1
40
.0
1.5
o
.1
15
.1
14
.9
10
.0
e.5
1
00
.0
2.0
2 7
. 72
34
.2
16
•9
2.0
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LEGEND :
Fig. 2-5
(b)
--o- SITE No. 1 , -Ci- SITE No. 2
r, RAINFALL(rrun)
-< 6: 0.0?.. 5
F '
MO A
Hg
n --()-l-o_l .·~ l
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---6--- SITE No. 3 '
~- SITE No. 4
10()
]()() Ji ,, ·I i.':
!()() (i ;I
VARIATION OF PARAMETERS OF RAIN - WATER OORING
FEBRUARY - SEPTEMBER
(d)
(c)
additional contributions in the form of diesel exhaust gases l on account of the ra~way track passing through the area.The
acidity of the rain water collected at site nos.1 • 2 aad 3 has appeared to be largely neutralized as evident from the pH values which indicated either an alkaline or only a feeble acidic nature. The acidity of the rain water appears to be neutralized by the presence of suspended particulate matter which are continually emitted by the steel plant. According to an earlier report (46),the dust fallout matter collected
from this area indicated an alkaline nature 1 the pH of its 10% slurry in water being found to be 7.35. During the peak
period of monsoon ( July - September ) , an abrupt decrease in
pH values of the rain water at site nos. 2 and 3 has been observed. As found out earlier and reported in the prece~ding section , the SPM levels during the monsoon season have been foUnd to be significantly lowered. The increased acidity in rain water in this season,in absence of sufficient neutraliz-
unders tan dab~. ing speci~s, is thus quite . . ~£he increase in the
pH value of the rain water and also in the TDS value during
the monsoon period at site no. 4 required special attention.
This site is situated far away from the gas emission so~rces of steel plant compared to the site nos. 2 and 3. The wind
direction during this period keeps this sampling site almost
unaffected by the gaseous emissions of the plant. Further ,a
cement plant is situated close to this site compared to site
nos. 2 and 3. The suspended particulate matter at this site
shall thus have a composition different from those at site
no$. 2 and 3. The chemical compositions of the dust par
ticles emitted by the steel plant and the cement plant;both
of which are involved in the studies described ' have been reported by an earlier worker (43). According to his report
Ca and Mg are the two largest components of the dust f~llout
matter from the cement plant , and are present at levels of
96000 and 58020 ppm respe~tively. In the case of emissions
BO
from the steel plant • these levels are 574 and 2858 ppm
respectively (43). The close proximity of the cement plant
and the huge presence of Ca and MQ in the dust emissions
from this plant adequately explains the alkaline nature
of the rain water at this particular sampling site. The
The particulate emissions at a cement plant, containing
oxides of alkali and alkaline earth metals • impart alkali
nity on dissolution. The increase in TDS value and the in-
crease in pH value in t~e rain water during
period is thus understandable.
the rainy
( 2) TDS and Condactance · 1- The TDS and conductance of the
rain water in the area of study have followed almost
identical trends. The values of these two have remained
almost static in the rain water samples during the
premonsoon period and have shown abrupt changes at the
onset of monsoon. At site nos. 2 and 3 • their values were
significantly lowered during the high rainfall period (July
-September). However, at site no. 4 • the' TDS showed
an increase in the high rainfall ped.od. This is on account
of the solubility effect of the particulate matter which
was distinct in nature in this area on account of
contributions from a cement plant located in a nearby area.
The components which were alkaline in nature were suscepti-
ble to interact with the rain water resulting in the
formation of dissolved salts , and the corresponding incre
ase in the conductance values. The alkaline nature of the
rain water at this sampling site has already been reported
and discussed in the preceding paragraph.
(3) Sulphate and nitrate:- No significant trend in the
variation,bf the concentrations of sulphate ·and nitrate
during the period of study has been observed. The concen
tration of sulphate has • however , been found to be higher
compared to that of nitrate in all of the samples.
(4) Calcium and magnisium 1- The concentrations of Ca (II)
and Mg (II) have been found to be higher in almost all samples of the rain water collected at sampling site No. 4.
The reason for the higher presence of Ca (II) and Mg (II)
at t.his site has been found to be the same as stated
earlier 6 i.e. 1 the location of a cement plant near this site. These high values are in agreement with the high TDS
values of the rain water samples found at this sampling
site. Ca (II) and Mg (II) are often quoted as the common
components of the rain water deriving their origin from
soils of the respective area. According to the findings of Verma {11) , the rain water at a particular place possesses
all the fundamental characteristics of the near=by soil. The phenomenon of the calcification of the surface - soils in the vicinity of a cement plant has been studied and
described {53). The impact of the calcified soils on the calcium contents of the aerosols over this sampling location
may also be a probable cause of the high Ca (II)- level of
the rain water.
{S) Sodium and potassium :-These are non- critical metals
and have been found to be present +
here in all the samples
of rain water at low levels ( Na 1.0 • 33.0 1 + . K l.0-15.0
mg I 1 >.The pattern of the variations of the concentra-
tion levels of these two metals has been found to be irre
gular. However , the sodium levels at site no. 4 are higher
in most cases. This is on account of the location of a
cement plant in a nearby area and the consequent entry of
additional sodium through the dusts emitted by this plant.
The sodium and potassium content of the dust fallout matter
of this particular cement plant have been reported to be
IRIIiii~IWfilllm lllmllfillfi T 11531 \153\_
52
2200.0 and 0.45 ppm respectively (43).
(6) Lead ,_The presence of lead in the rain water samples
is of significant environmental concern. Lead has been
found to be present in all samples of the rain water - ~nd '
the range of its concentrations has been found to be 10.0
- soo.o ~g I l. The origin of lead in rain water samples be
shall have to~traced to lead emissions from steel plant.
The lead emission factors for steel industry have been des
cribed as follows : Open - hearth 0.14 lb I ton of steel
produced 1 Blast furnace 4 lbl ton of product (54). Accor
ding to studies carriecput earlier in this area , the lead
concentrations in the steel plant fallout matter have been
found to be in the range of 119.30- 301.60 ppm (47}. The
presence of lead in the rain water collected in the area of
study can thus be taken as a logical consequence of the
lead - contamination of the atmospheric air in this area.
As per tolerance limits for the presence of lead for
drinking water ( with or without treatment } *as per Indian
Standards is 100 pg / 1 {SS). Except at sampling site no.1
which is mostly unaffected by the steel plant emissions 1
all other sites have shownthe lead presence at concentra
tions beyond the permitted limit of lead for drinking water.
It is thus obvious that the presence of lead in the rain
water not only renders it unfit for human consumption but
also contaminates the natural water streams and reserviors
by introducing extraneous lead into them.Th~ighest values
of lead have been found mostly at site no. 3 which is
located closest to the emission sources of the steel plant.
(7) Mercury 1- Mercury presence is closely related to coal
burning and coals with which it is invariably associated
~4, 56). Klein and others (45, 56) have reported the dis
charge of mercury at a rate of o.'l g I min. through a coal-
53
fired power plant. According to a report , coke ovens in USA discharge 7160 Kg of mercury into air each year (57) • The presence of mercury in dust fallout from this steel plant was determined by earlier workers 1 and the mercury level was found to be present in a range of 0.95-1.10 ppm <sa>. Mercury vapour concentrations in the vicinity of the Bhilai Steel Plant and the cement plant located near it have been reported to be between 1 and 3 pg I m3 during a surveillance of air- borne mercury in this area (48).
Mercury in the samples of rain water as determined here has been found to be in the range of 1.0 - 16.0 p.g I l. An exceptionally high value of mercury ( 160 p.g/1) at site no. 3 , during the month of April 1 has been recorded (Table 2 - 4) , the r,easons of which have , however, not been found to be clear , except that this site is situated closest to the emission sources of the steel plant and 1 in general , indicated the highest presence o~ mercury in the rain water. The mercury level in rain water has been found lowered during the period of monsoon ( July - September ) •
This is on account of dilution of mercury by the intense rains during this period. The maximum permissible limit of mercury as per Indian Standards for drinking water is 1.0 pg I 1 (59) • This limit has been found exceeded by the rain water almost at each sampling site. As already reported in
the case of lead , the mercury presenc;::e . in the r,ain water not only renders it unfit for drinking purposes ,but also contaminates natural water streams and reserviors by contributing extraneous mercury to them.
'
51
2.4 A C I D P R E C :I PI '1' AT :I 0 N 1 S T U D Y 0 F
R E A C T I V I T Y W I T H L I: H E S T 0 N,E AN D
* D 0 L 0 HI: T E.
INTRODUCTI:ON
The extent and magnitude of acid rain related research
bears testimony to prediction that. acid precip5. tation would be one of the major environmental problem of this decade (60).
During 1981 1 there was considerable interest in the cause 1
effects , prevention , control and monitoring of acid rains.
New York State 1 Department of Environmental Conservation 1
released a study documenting the envirohmental impact of ·acid
rains occu;ing in upstate New York ponds and lakes (61). Dis-... tribution of rocks and soil. in North Eastern United State were
investigated for the degree to which they influence pH and
alkalinity in surface waters (62). The mechanism by which produced
acid precipitatiort~embryonic deaths in aquatic vertibrates , has also been reported ( 63). The effects of acid rain on
vegetation 1 soils and forest ecosystems were also widely studied (64, 65). Raymahashay has reported the vulnerability
of the plaster , mortar and stone materials of Chittaurgarh
Fort to acid rains.
The bulk of acidity in rain is due to compounds of
sulphur and nitrogen approximately in a ratio of 2 : 1.There
are , however 1 reports of increase of acidity due to nitro
gen in recent years (66 _68) • Pure rain water is
reported to have a pH of 5.6 due to absorption of co2 to form
H2co3• According to the classification of Scribven ,the rain
water having pH between 5.6 - 6.0 has been te~ed as 'neutral
rain water' , that having a pH less than 5.6 as 'acid rain
water' 1 and that with pH greater than 6.0 as 'alkaline rain water'. so2 is a fairly soluble gas and it has been suggested
* "Pe:cvez, s. and Pandey, G.S., "Impact of Acid RC!ins on Lime-stone and Dolomite", Indian J Environmental Protection, 10,
-(8) ( 1990) 604-606.
55
that atmospheric oxidation to H2so4 can i'ICtually take placP. ln clouds (70). Falconer and Kadlecek hdVe dnalysed the
samples of cloud -water collected during an air craft
flight , and have reported the presence of so4- in the range
of 261 - 558 mg 1 1 and N03 in the range of 73 - 240 mg /1~ The pH range was 4.3 - 3.5. It can thus be inferred that H2so4 and HN03 are the ultimate products of so 2 and NOx components which contribute acidity to acid rains.Limestone
and dolomite are of common occurrence as surface rocks in
India. These are widely used in building materi<~ls , <tnd in
the cement and steel manufacture. It will be of j_nterest to
have an appraisal of the vulnerabi 1i ty of these C'"lr·bonate
rocks to acid rains ~ and to know the comparative corrossivities of the acid rains in terms of their H2so4 and HN03 components.
~1adhya Pradesh , in particular , is very rich in limestone and dolomite deposits in the country.The deposits
of these carbonate rocks in different districts of Madhya Pradesh ( 72) have been shown in Table 2 - 5. At several d,,_
posits of these rocks , there is no over-burden to remove
before quarrying the materials. The pits which are develop
ed after the removal of rock materials are generally used
as storage ponds of rain water which are used for irriga
tion and fishery purposes. The studies here . have been s
ca.rrie~ut to know (i) the relative corrosiveness of acid ~
rains , in terms of H2so4 and HN0 3 components , towards
these carbonate rocks (ii) the extent and nature of the
hardness developed by the interaction between acidities af
acid rains and the rock materials , and (iii) the relative
susceptibilities of the limestone and dolomite for mineral
damage through the acid rains.
It is presumed in this laboratory modelling that
no other procel'jses except those of (i) simple dissolution
5G
* Table 2-5 LlMBSTORE AND DOLaa'l'l: DEPOS:I'l'S :IN MADIYA PRADESH
District Locations Grade Estimated preserves (Million tonnes)
LIMESTONE DEPOSITS
Bas tar Kanger Limestone cement 845.0 Bhopal Ginnur fort Intercalations 28.0
Khan pur of shally bands
Durg In 20 localities Cement 21.5 More sara Flux 28.0 Dearjhal Flux s.o
Bilaspur Mohatra to Flux 776.0 Arsameta area Akaltara Flux 116.0 Al<altara cement 100.0
Jabalpur Newra Flux 18.3 Naubasta Flux 21.2 Naubasta Cement 33.6 B<mkuiyan Flux 66.4 Bankuiyan Flux 104.8
Satan a Maihar Flux 25.2 Maihar Cement 15.2 Maihar Blendable 16.0
Cement sejahata Flux 29.0 Sejahata Blendable 8.5
Cement Rarnnagar Flux 29.0 Ramnagar cement 10.0
DOLOMITE DEPOSITS
Bilaspur Chilhati to Arasmeta area 56.5
* Ref. 72.
57
of the rock matter in the aqueous medium , and (ii) simple
salt formation due to the interaction of hydrogen ions with
the reactive materials • are involved.
MATERIALS AND METHODS
Sample collection : Samples of freshly mined limestone and
dolomite ( 10 Kg each ) were collected from Nandini deposits
( District - Durg , M.P •. ) and Hirri mines (District-Bilas
pur , M.P.) respectively.
P:rocedu:r:e I
9?mposi tion studies : The principal components ( CaO and
MgO ) of the rock samples which are vulnerable to acidities
of rain water were determined as follows 1 Representative
samples of the rock materials were ground to a homogeneous
powder form , and then heated in an oven at 11o•c for
three hours. Weighed quantities ( 1 g each ) of the dried
samples were treated with acid mixture of HCl and HN03 (3 J 1) and evaporated to dryness. The residue was treated
with dilute HCl (1:10) and the in~oluble silica was removed
by filtration. The filtrate was treated with NH4Cl ( 1 g )
then with excess of NH40H till ammonical. The solution was
boiled , allm1ed to cool , and the mixed oxides were
removed by filtration. The filtrate was diluted to 250 ml.
Aliquots ( 10 ml each ) of the solution were treated with
2 ml of buffer .solution ( NH40H - NH4Cl , pH 10 ) , 30 mg
Eriochrome Black T / KN0 3 mixture and titrated with stand
ard EDTA solution ( 0.01 M ). The titre value represented
Ca and Mg. For Ca - determination , the same aliquot ( 10
ml) of the solution was treated with KOH solution (8 M ),
50 mg of Patton and Reeder's indicator / Na2so4
mixture
and titrated with standard EDTA solution ( 0.01 M) (52).
The titre value correspond to calcium. The results obtained
from three replicate determinations have been shown in Table
2 - 6.
* Table 2 - 6 CaO AND Mfj:J IN ROCK SAMPLES
Rock samples CaO (%)
Limestone 48.12
Dolomite 29.28
* Mean values of three replicates.
58
MgO (%) .
3.21
18.21
Impact studies : 6 glass tanks { capacity 40 litres each )
were filled with deionised water , and each .was aerated
using a pump to make the water saturate with co 2 • Three
containers were marked for limestone , and the other three
for dolomite. One container in each set was acidified with
H2so4 ( pure grade ) to produce a pH of 4.35 ( this was
equivalent to 123.4 ppm of so 2 ). Another container in each
set was acidified with HN0 3 to produce the same pH ( 4.35 )
(this was equivalent to 173.7 ppm of NO). The third
container in each set was filled with deionised water. Weig
hed quantities { 10 Kg each ) of limestone were lowered into
each of the three tanks marked for limestone studies. Simi
lar!~ same quantities of dolomite were placed in three tanks
marked for this material. Aliquots ( 10 ml each ) of the
water from each tank were drawn at intervals of one day,and
pH , total suspended solids , calcium hardness and magnisium
hardness were determined using standard procedures as follows:
~ :- The pH meter ( Century , Model CP - 901 ) was calibra
ted using standard buffer solutions. The measurements of
the pH of the water samples were then made.
fW
Total suspended solids 1 A well mix.,.<l water s;unpl~ Wl.l5
filt.ered through a disc mambrane filter apparatus 1 dried
in an oven at 103 - 105 °C for one hour 1 cooled in a deslccator and weighed (So).
Calcium hardness 1 Aliquots { 10 ml each ) of the water sample were taken in an Erlenmeyer flask ~ and calcium and
magnesium were determined ti trimetrically using EDTA ( disodiurn salt ) solution ( 0.01 M ) and Eriochrome Black T
indicator solution as described earlier. Calcium was deter
mined using the same titrant but with Patton and Reeder's
indicator as described earlier. 1~e magnesium concentration
was foundbut by taking the difference of the two titre values (52). The measurements were carriegbut at intervals of one
day till nearly constant values { equilibirium values )were obtained.
Results obtained have been shown in Table
2 - 7 • 'rhe relationship between the yariation of pH
with increasing duration ( days ) has been .shown in
Fig. 2 - 6. 'I'he relationship between the generation of hard
ness with duration has been shown in Fig. 2 - 7. The relation
.ship between TSS and duration has been shown in Fig. 2 - 8.
All the chemical reagents used were BDH
(AnalaR grade). The water used was distilled and deionised.
The glasswares used were superior quality borosilicate.
RESULTS AND DISaJSSION
The following conclusions have been found:
(1) The interaction Of HN03 - contaminated water has shown
higher corroiivity for the limestone and dolomite compared "
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.-
- MEDIUM HN03
- MEDIUM HzSOc,
---- MEDIUM WATER
A DOLOMITE
t:, LIMESTONE
7.8 '----~2----'----'-------,~--.L.-.-----' l, 6 8 10 12
DURATION (DAYS)
FIG. 2-6. RELATIVE pH VARIATIONS.
t ..
...
62
110
-- -- --b--- -{j----(r------!J
• 90 ~ ~
' ~ 0 u 0 u
"" E
~ 70~----~~----------~~------------~------------.-----~~----~ z 0 0: <( J: >----~•a.----•---t~
----+----A--- -.A-----4----·--- .... ------ -.A
HN03 medium H2so4 medium
WATER medium
30 A Co-Hardness { Dolomite)
4!1 Mg-Hordness {Dolomite)
!J. Co-Hardness ( Limeston'2)
0 Mg- Hardness (Limestone)
_ __o-- --- --o----
10
oL-----~2~--~3~----~4----~s~----G~----~7~--~e~----~9----~,o~
DURATION {DAYS l FIG 2-7 FORMATION RATES OF WATER HARDNESS IN DIFFERENT MEDIA
63
80
'" .... -·-- 70 -..... .fr-----01 ,.tr- -E ' / /
lf)
0 60 --' 0 lf)
0 /
w 50 / 0 I z I w );)
Q I lf) f ::::> 40 lf) HN03 MED. _..J
<( 4 DOLOMITE f-0 30 _. ----·------ !J. LIMESTONE f-- ----- H 2so4 MED.
---- WATER MEO.
20 2 4 6 8 10
DURATION (DAYS)
FIG. 2-8 RELATIVE RATES OF TURBIDITY FORMATION
G1
to that of H2so4 - contaminate<! water. HN0 3 - contaminated
water 1 in case of limestone 1 has produced 22,7% more of
Ca - hardness compared to H2so4 - contaminated water and
42.1 % more compared to pure water.
(2) The corro{ivity of dolomite ( or dolomitic lim<'!stone )
is smaller than that of the limestone. V\ihile the Hg - hard-
ness produced by the dolomite on interaction with H2so4 contaminated water is nearly the same as produced by the
pure water , its valu.!is 71,4 %more in case of HN03 - con
taminated water.
(3) Kinetically 1 dolomite has been found to be a faster
neutralizer of the H2so4
- contaminated wa1;er 1 followed by
limestone for HN03 - contaminated water,
( 4) The generation of suspended solids ( turbicli ty ) has
been found to be follows : Highest by dolomi·te with I-IN03
-
contaminated water followed by limestone in H2so4 - con
taminated water. The lowest turbidity has been found in case
of dolomite in H2so
4 - contaminated water. The low solubility
of Mg(OH)2
at the equilibirium pH ( 8,35- 8,45 ) compared
to that of Ca(OH)2
is ascribable to the high turbidity and
anc1 low Mg - hardness in case of doloini te.
It has further been found from the observed
data ( Table 2 - 7 ) that one litre acid rain water havin.g
a pH of 4. 35 could distroy upto a maximu~:1 of 188,15 mg of
limestone and 158.26 mg of dolomite mineral~besides contri
buting corresponding hardness to natural water rec;ources.
When the experiment was repeated to study similar effects on
iron ore samples of the nearby Dalli Rajhara mines 1 it was
found that the mineral damage of the iron ore by acid
precipitations having similar pH could cause only an
in=significant damage, Sustained observations over a p~riod
of 12 days showed that one litre volume of acid rain having
a pH 4.35 could solubilize only 1.4 mg of the iron ore. The
insignificant solubilization of the iron ore is on account
of the hydrolysable nature of ferric ions resulting in the
precipitation of Fe (III) as Fe(OH)3 1 unless th'e pH of
the aqueous medium is below 3.o. The acid rains rarely
reach the acidity of pH 3,0. Hence the acid rains can be
taken to pose no significant damage as far as iron - ore
deposits are concerned.
2.,5 RATE EVALUAT:J:ON OF MARB
D A M A G E l!3l Y so2
- A C ~ D J: :1' T
STACK VJLCJ[miiT:IES.
INTROWCT:ION
LE
:U: N
An awareness has been seen in India for the preserva
tion of the monumental marble.. structure of Taj Nahal at
Agra against corrosion damage from atmospheric 502 (21).
The City Hall Building in Schenectady , New York was built
in 1930 of the finest Vermont marble, It is reported to
have fallen victim to distruction by acid rains. It is
also reported that inscriptions in 500 years old marble
monuments at Peking in China which were legible until 40
years ago are unreadable now (3). This
that most of the damage of the marble
clearly indicates
structure has
occurred recently. Increased emissions of 50 2 and NOx by
the industrial and prtvate sectors have resulted in an
increase .in acid rain formation and j_ ts destruct! ve effects
* Pervez, s. and Pandey, G.S., "Rate Evaluation of Marble Damage by so2-Acidi ty in Stack Vicini ties", J Environmental Geochemistry and Health, (England) , (In press).
ou
on marble. so2 and NOx which are emitted from industrial
stacks are converted to suphate and nitrate respectively,
which give rain of acid character. The sulphates then
convert the calcium carbonate , an insoluble component of
marble , into soluble material known as gypsum. The
nitrate converts the calcium carbonate to calcium nitrate,
Sulphur dioxide dissolves readily in
water , and the product is slowly oxi<lised to
acid by the atmospheric oxygen. In the presence
sulphuric
of cataly-
sed impurities such as manganese and iron salts 1 the
conversion of so2 to H2so4 is more rapid (73 1 74). s~
can also react catalytically or photochemically in the
gas phase with other air pollutants to form so 3 ,
and sulphates (75) •
There have been many laboratory investi
gations of reaction - processes involving 50 2 with
sunlight, The reaction was found to be slow ,but enhanced
in presence of hydrocarbons and other pollutants ( 7- 10).
'l'he half-life of 50 2 has been estimated to be three to
five hours, Modern optical and classical techniques to
identify the destructive material have been reported to be
used by Cheng and coworkers (3). They discovered that gyp
sum was always present in samples of deteriorated marble
indicating that sulphates converted the marble to gypsum,
The ratio of nitra~~ and sulphates embedded on the marble
surface was determined by ion - chromatography by the same
workers 1 and it was found that the concentration of sul
phates\m the marble surface was more than 20 times greater
than that of nitrates, The same authors also found that
the loss of the marble immersed in H2so
4 (30 pH)wns almost
three times as much as that lost in HNo3
solution of
67
flimilar strength. In the case of 100 JIM acid solution , the marble loss in sulphuric acid experiment was 13 - 17
times as much as lost in HN03 experiment. The same aut.hors
further found that both flyash and so2 are needed to cause
consideri'ible damage to marble. It was inferred by them
that the metals in flyash 1 such as Fe , V , Cr , Mn and
cu could play a catalytic role in oxidising so2 to sulphates.
The studies carriedbut earlier at the place
of these investigations have provided conclusive evidence
of the presence of metallic oxides of catalytic nature
such as Co I cu , Ni 1 Cr , Fe 1 Mo , Mn and V in the stack
emissions from industries such as phosphatic fertilisers,
iron and steels 1 cements and thermal power (76 - 84). The
reported statement of Cheng et al. (3) with regard to The
presence of catalytic metal oxides along with so2 eml.ssions
from smoke stacks is thus further confirmed.
Based on above evidence 1 a laboratory modell
ing for the e~aluation of rate of marble - damage by so2 acidity in stack vicinities has been attempted. The modell
ing is based on following observed facts : (i1 The so2-
emissions from stacks include the product of coal combus -
tion , and are nearly accompanied by profuse flyash
emissions. (~i) The marbles are mostly carbonate - rocks s
and hence su~eptible to corrosion by acids. (iii) The fly-
ash particulates invariabl~ontain catalytic metallic oxides
with known capabilities to convert so2 to so3 • The photo -
chemical processes· further supplement the formation of so3 •
(iv) The humlidity in the atmosphere provides the finale to
the formation of H2so4 • Thus on the surface of the marble
structure 1 it is the H2so4 in place of original so2 whose
behaviour and capacities to damage the marble material are
to be studied. A limitation in the modelling is that the
68
conversion o~ so2 to H2so4 has been taken on 100 % basis. The inferences derived from this modelling would thus correspond to the maximum limit of damage which the so2 of the ambient air could cause to the marble.
MATERXAI.S AND METHODS
Sample collection 1 Samples of marble blocks having origin from marble mines of Rajasthan ( India ) were collected.
The surface area of each block was found out by measurement of dimensions of each block.
Procedure 1 Five marble blocks of known surface area were placed in separate rectangular jars , and then immersed in one litre of H2so4 - acidified solutions whose stengths were in terms of 100 , 50 , 10 , 5 , 1 mg so2 / litre. The pH of each solution was continuously monitored and held at initial values by fresh addition of dilute H2so4 solution. A blank set containing a ~arble block of kn~wn surface area in distilled water ( 1 litre ) was also run to know the solubility effect of water on marble. All jars were thermostated at 31 °C. Aliquots ( 5ml each ) were drawn after
intervals of 1 day from each jar , and ca and Mg ions concentrations were determined titrimetrically using standardised EDTA solution ( M/100 ) • NH3/NH4cl buffer (pH 10.0) and mriochrome Black T indicator solution (52). The major components of marble samples were also determined and found
as follows 1 Moisture • 0.1 % , Si02 - 1.5 % ,caco3 - 55.~~
Mgeo3 - 39.0 % , Mixed oxides - 4.0 %. The density of marble samples/was also determined and found to be 3.02. ·. _ The data of surface areas of marble blocks , strength of
H2so4 solutions ( as ppm of so2 ) , duration of immersion,
total mass loss per day per unit area have been shown in Table 2 - 8. Durations ( in years ) for-the decay of 1 omthickness of the marble blocks have been calculated using
the density data , and shGwn in the Table 2 - e. Data , on
rlaily - l::>asis • were recorded for each of the so.~- concen-da-c-a
trations. Te illustrate the rate kinetics , the,recorded in
respect of 10 ppm so2 experiment have been :!!hewn in
Table 2 - 9. A relationship between so2 presence and the
calculated durations for the loss ef 1 em - thickness of
marble has been shown in Fig. 2 - 9.
RESULTS AND DISCUSSION
The investigations have shown that the presence of
so 2 - acidity even at 1 ppm level in the environment produces
a corrosion damage to the marble surface at a measurable
rate. The marble which is the costliest of all building
stones has thus been found to be sensitive for the
so2 - acid! ty. _The erection of a marble structure at any
place thus requires to be preceded by determination of the
average level of so2 in the ambient air. The durations
( in years ) for the decay 'Of 1 em - thickness of the
marble block for different values of so2 - acidity under
the conditions of the experiment have been found as
follows : 100 ppm so2 - _4~31 years, 50 ppm so2 ~ 8.19
years ~ 10 ppm so2 - 31.24 years # 5 ppm so2 - 69.02 years,
1 ppm so2 - 83.02 years ~ provided that the acidity is
sustained at the stipulated levels for the calculated
durations. The damage-reaction ( based on the loss of caco3
and 11geo3 as the principal components of marble ) , studied
at 10 ppm so2 - acidity , has been found to follow the
first order rate kinetics.
The modelling is useful in predicting the fate of
marble structures of monumental importance on the basis of
ambient air conditions.
• T
ab
le
2-8
D
EJCA
Y
OF
MA
RB
LE
AT
DIF
FE
RE
NT
so
2-A
CID
ITIE
S(T
EM
?.
31
C
)
Su
!'"
face
e.
rea
S
tren
gth
pH
v
alu
es
D..
lrati
on
s a M
ass
loss
b --
c M
ass
loss in
M
ass
loss
calc
ula
ted
o
f In
a:.-
ble
o
f H
2so4
of
of
in
term
o
f te
rm o
f in
te
rm
du
rati
on
fo
r b
lock
s
so
luti
on
s so
luti
on
s
imm
ers
ion
caco
3 an
d
caco
3 an
d
of
marb
l"
d"c
ay
o
f 1C
B
MgC
03
Mg
cc3
ger
day
per
da¥
th
icic
n.,
ss o
f p
er
ern
area
p
er e
m
area
m
arb
le
(cm
2)
(ppm
so
2)
(Day
s)
(mg)
(m
g)
(mg)
(y
ears
)
( ll
( 2)
(3)
(4)
( 5)
(6)
(7)
:03
.14
D
ist.
w
ate
r 6
.90
1
1.0
9
.1
10
0.5
7
10
0
3.3
0
7.0
1
27
7.6
1
.81
1
,92
96
.12
5
0
3.6
0
7.0
6
49
.2
0.9
5
1.0
1
3.1
9
10
1.9
5
10
4
,05
-7
.0
18
7,0
0
.25
0
,30
3
1.2
4
:i0
6.8
7
5 4
.15
7
.0
85
.2
0.1
1
0.1
2
69
.02
10
3.1
4
1 4
.60
7
.0
56
.8
0.0
7
0.1
0
83
.02
a-T
o all
ow
co
mp
leti
on
of
sig
nif
ican
t in
tera
cti
on
; b
-aft
er
co
rrecti
on
fo
r th
e so
lub
ilit
y lo
ss
in p
ure
w
ate
r;
c-
calc
ula
ted
fr
om
p
erc
en
t co
mp
osi
tio
n o
f m
arb
le;
d-
calc
ula
ted
_fr
om
den
sit
y d
ata
(3.0
2)
of
marb
le.
Th
e v
alu
es
den
ote
th
e d
ura
tio
ns in
w
hic
h ~~e
mas
s lo
ss o
f 3
,02
g
of
marb
le(v
olu
me
1 cc)
may
b
e
cau
sed
at
the sp
ecif
ied
ra
te o
f d
amag
e.
sam
ple
calc
ula
tio
ns:(
l)
Valu
es
of
co
lum
n(6
)=(v
alu
es
of
colu
mn
S
)X
10
0
% C
aC0
3+
%
MgC
0 3
[2) Valu~s
of co1Q~n(7)
=
30
20
(mg)
(Valu
es
of
colu
mn
6)X
3
65
...:I c
~
Tab
le 2
-9
HA
TE
O
F M
AR
BLE
D
AM
AG
E A
T A
LE
VE
L
OF
10
p
pm
so
2-A
CID
ITY
Su
rface are
a
str
en
gth
o
f pH
v
alu
e
Du
rati
on
M
ass
loss
Calc
ula
ted
valu
e
of
marb
le
H2s
o4
so
luti
on
o
f in
te
rm
of
fir
st
ord
er
blo
ck
so
luti
on
o
f ra
te co
nsta
nt
caco
3&
Mgc
o3
K*
(l0
-4 )
(cn
2)
(pp
m
50
2)
{D
ays)
{m
g)
{T
ime-
1)
1 2
6.'
7
1.5
0
2 5
3.4
1
.47
3 8
3.1
1
.50
10
1.9
5
10
4
.05
4
11
0.8
1
.49
'
5 1
33
.5
1.4
9
6 1
60
.3
1.4
8
1 1
87
.0
1.4
9
Fir
st
ord
er
rate
co
nsta
nt
K*
=
2. ~ lo
g .
...!..
.__
t a-x
~
Wh
ere
t-D
ura
tio
n{
day
s);
a-
In
itia
l w
eig
ht
of
MgC
03&
caco
3 ~
17
8.6
91
x
-W
eig
ht
of
Mg
o&
j &
caco
3
dis
so
lved
in
d
ura
tio
n t.
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-I
20 l,O 6 0 80 100
CONCENTRATION OF SOz (ppm)
FIG. 2-9 RELATIONSHIP BETWEEN 50 2 CONCENTRATION AND RATE OF DECAY OF MARBLE.
'72
73
2.6 ACID RAIR ""SLAG IR.'rERACT:ION·S I
STUDY OF HYDROGER SULPHIDE
EVOLUTI.OR
INTRODUCTION
An integrated steel plant as at Bhilai has been found q
to be~source of so2 and NOx emissions which are capable of causing acid precipitations. Slag formation
associated with steel manufacture.
is This
is discharged in massive quantities by
a normal
process
product plants. The rains , particularly in their beginning
waste
steel
periods
have been found to fill the atmosphere with a disagreeable odour ( similar to that of 1-12s ) in areas near the,. slag deposits. The studies described here are aimed at obtaining quantitative informations in regard of slag acidity interactions.
An appraisal of the size of the steel industry in the
country , and the quantum of slag - discharge resulting from the industry is desired before proceeding to take up a study of this nature. Slag productions . :are directly
related to the production of iron and steel.The production
of steel during 1988 - 89 in Bhil*{has been reported to be more than 2.5 million tonnes. The production of steel at
the Bhilai plant during the period from 84 - 85 to 88 - 89 has been shown in Fig. 2- 2.(36). The average rate of
discharge of slag in India is 615 Kg 1 tonne of steel
manufactured (85). The slag results from the neutralization
of materials of acidic and basic natttre , hence corresponds
roughly to salts formed in aqueous solution during chemical
reactions at ordinary temperature (86).Composition·of slags
is rather complex. Up to 30 different elements occur in the
slags mainly in the form of oxides. The principal ones
'~ I I
include 5i02 1 Al 2o 3 1 CaO and MgO. Usually present in
lesser amounts are FeO , MnO , S 1 P2o5 , Tio2 , v2o 5 ,and
others. All the blast furnace. slagscan be divided 1 from
the stand point of their chemical composition , into three
groups, namely acidic 1 basic and neutral (87).
The composition of slags depend on the chemical
composition of raw materials , operation practice and grade
of metal to be produced. The chemical composition of blast
furnace slags in Indian steel industries has been reported
(88) to be in the following ranges s 5io2 33 - 42 % IA12o3 10 - 14 r. ; cao 36 - 45 r. ; MgO 3 - 12 r. r 5-l - 3 r. ; FeO
0.3 - 2% ; MnO 0.2 - 1.5 %.
The average chemical composition of blast furnace
slag of Bhilai Steel Plant to which the work reported here.
is related has been reported as follows (88 , 89) 1 Si02 34.53% ; Al2o3 22.38 % ; Cao 34.75% ; MgO 5.80 1o ; FeO
0.81% ; MnO 0.59 Yo and 5-- 0.74 %.
MATERIALS AND METHODS
Sample collection and preparation :
Slag samples s Three samples of blast furnace slag ( 1 Kg
each ) were collected from different storage points of the
slag yard of the steel plant of Bhilai. Representative
portions ( 50 g each ) of the samples were thoroughly
ground to a fine powder form ( 100 mesh size). These were r
then died in an oven at 110 °C for 3 hours 1 and used for A
compositional studies. The remaining bulk of the samples
were broken into small lumps ( size 1.0 - 1.5 em ) compo
sited and used for the acid rains interaction studies.
75
-Acid ~o samples a 10 - litre volume of the rain water sample which had the highest value of acidity ( pH 5.60 )
and was collected at site no. 3 ( Fig. 2 - 4 ) during the month of JUly 1991 , under the acid rains studies (Section 2.3) was retained in a stoppered polythene can , and used for the interaction studies.,The other two samples of acid rains ( 2.5 litre each ) having pH values of 5.10 and 4.60
were synthetically prepared using H2so4 and and HN03 acids to provide same sulphate -nitrate ratio ( 4a1 ) as existed
in the natural acid rain water having the pH 5.60.
Procedure 1
Compositional studies of slaqs 1 The major components were determined as described below 1
(1) Silica 1 The dried sample ( 1 g ) was treated with an acid mixture of HCl and HN03 ( 3:1 ) • and evQ;p.orated to dryness. The residue was treated with dilute HCl ( 1:10 ),
filtered , washed , dried , ignited in a platinum crucible and weighed. The residue was treated with few drops of
H2so4 and then with HF 1 and ignited to a constant weight.
The loss in weight was recorded as Sia2 (52).
(2) ~ : The dried sample ( 1 g ) was treated with 20 ml
of concentrated hydrochloric acid and 1 ml nitric acid and then evqporated to dryness. It was then treated with 50 ml
dilute Hel { 1:10 ) , heated on a water bath and filtered.
The filtrate was treated with 1 g of NH4Cl and excess of ammonia solution , then boiled and filtered. The precipi~
tate was dissolved in dilute H2so4 and iron was estimated
spectrophotometrically using potassium thiocynate at 450 nm (52).
?U
(3) Aluminium : The dried sample ( o. 2 g ) was treated with 20
ml of concentrated HCl and 1 ml of concentrated HN03 and
evaporated to dryness. It was then treated with 50 ml of
di.lute HCl ( 1:10 ) , heated on a water bath and filtered.
The filtrate was treated with 1 g of ~H4cl and excess . of
NH40H , boiled and filtered. The precipitate was dissolved
in dilute H2so4 and aluminium was estimated spectrophotome
trically using aluminon (90) reagent , measuring absorbance
at 525 nm.
UtJ Calcium and magnesium 1 The dried sample ( 0. 2 g ) was
treated with so ml dilute HCl ( 1;2 ) and 5 ml of concen
trated HN03 , boiled and filtered. The filtrate was treated
with 1 g of NH4Cl and excess of ammonia solution. 'l'he
precipitated hydroxides of Fe , Al etc. were removed by
filtration. The filtrate was made up to 250 ml. An aliquot
of the solution (10 ml) was mixed with 10 ml of NH4Cl/NH40H
buffer and few drops of Eriochrome Black T indicator
solution 1 and titrated with standard EDTA (disoa!um salt)
solution ( M I 100 ). From the titre value, the combined
presence of ca and Mg (52) was calculated. In another
aliquot of the filtrate ( 10 ml ) # 10 ml solution of KOH
( 8 M ) and 1 g mixture of Patton and Reeder's indicator
were added and then titrated with standard EDTA solution.
From the titre value 1 the concentration of ca was
calculated. The corlcentration of Mg was then found out by
difference of the two titre values (52).
(5) Sodi.um and pOtassium 1 1 g of the dried material was
treated with 10 ml concentrated HF and 5 ml perchloric acid
in a Teflon beaker 1 warmed on a hot plate and diluted with
distilled water. Sodium and potassium were estimated flame
photometrically (91). The calibration graph was prepared
using standard solutions of NaCl and KCl.
?'7
M.ng!D!se 1 Weighed quaftti ty of semple ( 200 mg ) was diss
olved in 50 ml HN03 ( 1a3 ) and boiled. 1.0 g ammonium
persulphate was added , and the mixture further boiled for
15 minutes. The solution was diluted to 100 ml , and 10 ml
syrupy phosphoric acid and o.s g KI04 were added , and the
absorbance at 545 nm (52) was measured using a spectro
photometer ( Systronics Model 103 ). The blank was prepared
by decolourising the test solution with sodium sulphite
solution.
(7) carbonates : 1 g of the dried material was treated with
dilute H2so4 solution ( SN ) and the evolved co2
was absorb
ed in KOH bulb after bubling the gas through concentrated
H2so4 to remove moisture. The carbonate containing flask
was heated till the co2
evolution was complete , and the c
KOH bulb aquired a constant weight (52). A
( 8) SUlphide : A weighed quantity ( 1 g ) of dried sample
was placed in a 250 ml conical flask , heated with 100 ml
H2so4 solution ( 5 N ) , and evolved H2s was absorbed in
100 ml of standard iodine solution ( N I 30 ) placed in a
cold water bath. The excess iodine was estimated titri
metrically (52) using a standardised sodium thiosulphate
solution ( N I 30 ).
(9) ~ : A weighed quantity ( 10 g ) of the slag was mixed
with 100 ml of water , and the pH of the slurry was
measured using a digital pH meter ( Century Model CK 710 ).
The results obtained have been shown in Table 2 - 10.
Interaction studies : Having found out the concentration
of sulphide and other acid neutralisers present in the
slag, the capacity of slag to evolve hyarogen sulphide
'18
Table 2-10 CHE'HICAL COKPOS:ITION OF STEEL
PLANT SI.J\.GS (%)
constituents Sample Sample Sample Mean I II III values
5102 30.70 29.80 31.60 30.70 Fe2o3 3.20 3.40 3.00 3.20 Al2o 3 20.80 21.10 20.50 20.80 cao 33.90 34.00 33.80 33.90 MgO 8.43 8.51 a. 35 8.43
503 1.25 1.21 1.29 1.25 s-- 0.66 0.64 0.68 0.66 Mn 0.03 o.o3 0.03 0.03 Na2o 0.60 o.so 0.70 0.60 K2o o.so 0.45 o.ss o.so co;- 1.00 0.90 1.10 1.00
·pH 10.12 10.12 10.12 10.12 ( 10% Slurry)
'iU
gas on interaction with rain water having different ~cidi
ties has been studied. The modelling of the rain wash ·of
the slag matter has been designed here to match the event
of the actual rainfall over a stored mass of the slag
matter. During the rainfall of an acidic nature,t.he stored
slag will receive the rain water mostly at its surface,and
the sulphide of the slag will decompose evolving hydrogen
sulphide gas in proportion to the incident acidity. The
probability of the slag mound getting submerged in the
rain water is rather remote. The laboratory modelling is)
therefore1
based on the measurement of hydrogen sulphide
which is evolved due to washing of the slag mass by the
perpetual fall of water. For this purpose the lower half
portion of a Kipp's apparatus has been used as a reactor
vessel. A thick glass wool.pad was plugged into the neck
between the two lobes of the apparatus. Weighed quantity
( 750 g ) of the analysed sample of the slag was placed in
the upper lobe of the apparatus. The mouth of the lobe was
then con~cted to an aspirator bottle which contained a " measured volume ( 7.5 litres ) of the rain water. The flow
rate of the water was adjusted at 105 ml I hour to enable
the entire volume of the aspirator liquid to continually
wash the slag upto a period of 72 hours.
The effluent from the bottom lobe of the Kipp's
apparatus was drained into the sink after taking care to
maintain a liquid seal in the lobe to prevent any escapage
of the gas. The evolved gas was led into a standard
solution ( 250 ml) of iodine ( M I 100 ). The experiment
was repeated using two more samples of water. At the close
of each 24 hours 1 a known aliquot ( 10 ml ) of the iodine
solution was withdrawn from the vessel and titrated using
a standard solution ( M I 100 ) of sodium thiosulphate and
starch solution as indicator (52). The determinations were
repeated after duration of 48 and 72 hours. The
obtained have been shown in Table ( 2- ll ).
BO
results
All the reagents used were BDH (AnalaR grade ) •
The water used was distilled and deionised. The glasswares
used were superior quality borosilicate.
RESULTS AND DISCUSSION
The results obtained ( Table 2- 11 )have provided
following conclusions!
(1) The steel plant slag has significant contents of
sulphide ( 0.66 %by wt. ) , and in presence of excess of
acidity 1 1 g wt of it could liberate upto a maximum of
4.62 ml of H2s gas ( at NTP ).
(2) The alkaline nature of the slag ( pH of 10 % slurry
10.70 )on account of the presence of oxides of alkali and
alkaline earth metals has a protective importance for the
sulphide , preventing its decomposition into hydrogen sul
phide.
(3) The acidity contained in acid rain water is capable of
neutralising the alkaline nature of the slag on interaction,
and the sulphide is then exposed to react with the acid and
evolve hydrogen sulphide.
(4) The acid rain water of a pH of 5.60 while washing the
surface of slag at a ratio of 10 ml I g of the slag (equi
valent to 1 m3 of rain water I tonne of slag ) was found
to decompose 2.3 %of the slag- sulphide resulting in the
evolution of 14 litres of H2s ( at NTP ) during an inter
action period of 72 hours. At high acidities i.e. , at pH
Tab
le
2-1
1
Wei
gh
t o
f v
olu
me
of
In
itia
l sla
g u
sed
ra
in w
ate
r pH
o
f u
sed
ra
in w
ate
r
( 9
) {1
)
75
0
7.5
5
.60
75
0
7.5
5
.10
* 7
50
7
.5
* 4
.60
* .
syn
thesi
sed
sa
mp
les.
Vol
ume
of
H2s
ev
olv
ed
{
ml,
at
NTP
) aft
er
du
rati
on
of
1 d
ay
2 d
ays
3 d
ays
8.3
1
2.4
1
4.0
11
.1
25
.0
27
.7
16
.6
30
.5
38
.8
• (
Tem
p.
32
+
2 C
)
Perc
en
t d
eco
mp
osi
tio
n
of
sla
g
sulp
hid
e
2.3
0
6.3
7
8.9
0
Est
imate
d v
olu
me
of
H2S
(l at
NT
P)
ev
olv
ed
fra
n
1 m
3 ri
lin
wa
ter
inte
racti
ng
wit
h
1 to
nn
e o
f sla
g.
u.o
o
27
.70
38
.80
CXl
........
B2
'i.lO ann 4.fi0 of t.he rain wat.P.r thP. percentages of s11lphiclP
decomposition were 6.00 and 8.40 respectively , and the
volumes of H2s evolved 27.7 and 3B.fl litres (at NTP) res
pectively 1 dur.ing the same interaction period of 72 hours.
(5) The hydrogen sulphide gas can be detect.ed by its odour
even at a low concentration of 0.02 ppm. The ,findings have
shown that the acid rains and the sla0s both originating
from the same steel industry form a disadvantageous combina
tion from the points of view of public hygiene and environ
mental safety.
2 0 7 A C :I D P R E C :I P I T A T I 0 l!il S : F E W
EXAMPLES OF SELECTED PLACES
(A) snow melt water from Cleveland ( USA ) :
In India 1 snowfall occurs mostly in northern regions.
These regions have little or no industrial activity 1 and
hence are taken to be environmentally clean. The scope and
the necessity to examine the snow melt water of the country
is thus highly limited. It was considered useful to examine
the snow melt water collected from an environmentally cons
cious country such as USA 1 and know the quality of the
atmospheric air in that country. For this purpose I a sample
( about 1 Kg ) of freshly fallen snow was collected from a
residential area in Gilmer Lane at Clevel~bd in March 1991,
and brought to this laboratory for detailed studies. The
important characteristics of the snow melt water were deter-
mined and found to be as follows : pH - 4.85 , TS - 47.2
TDS - 17.2 1 Nitrate - 0.6 mg I 1 and conductance- 34.7
pMhos. It can be seen that the snow melt water showed
distinct acidic nature. In absence of the relevant data ,
I
a
, \
BJ
origin and the cause of this acidity could not be establi
shed. It can , however , be inferred that acid precipita
tions are common in cities like Cleveland in USA , and
the automobile exhaust gases and the emissions from the
industrial units are the unavoidable
happening of this nature.
sources
Acid rain episode of Bilaspur ( India ) 1
for a
An episode of acid rain of hazardous nature which occurred
on June 25 , 1990 , in the city area of Bilaspur ( M.P. )
(India) evoked enormous concern in the local populations.
From a local agency , . which collected the oamples of rain
water on the day o.f the episode , a day before the episode
and the next day of the episode , samples were obtained
and brought to the laboratory for investigations. The key
parameters of the rain water samples were determined and
found as shown in Table 2 - 12.
The results obtained ( Table 2 - 12 ) show
abrupt variations in the characteristics of rain water
samples collectea on three consecutive dates including the
date of the episode. Any natural basis for the excessive
acidity confined only to rain 1vater of a particular date
was not found to be tenable on the basis of the available
data related to the place of incidence. An uncontrolled
release of gases of acidic nature from a sulphuric acid
plant located few Kms away from the site of sample
collection 1 appeared to be the most probable cause for
the acid rain incidence of the place.
Table 2 - 12 CHARACI'ERISTICS OF RAIN WATER SAMPLES
Parameters Rain water ~amples collected on
24.6.90 25 () ** - .6. _,o 26.6.90
pH 7.46 3.00 7.20
TS mg/1 ) 140 00 102.20 50.00
TDS { mg/1 ) 40.00 52.20 30.00
Sulphate { mg/1 } 3.00 20.00 2.00
Nitrate { mg/1 } Nil * 0.90 Nil
Chloride { mg/1 } Nil 10.00 Nil .. Conductance fl mhos ) 82.20 100.20 70.20
* ** Nil denotes undetectable. The day of acid rqin episode.
SOHHARY
Back- ground
their occurrences
data about the formation
at the global levels and
of acid rain 1
their impacts on
men and materials were compiled through a ~iterature survey.
An appraisal qf studies carried out so far on this subject
in India was also made. The steel in1ustry as a promoter of
acid rains was placed in the prime focus of the studies.
The so2 and NOx as common contributors of acid rains were
determined by setting up air monitoring stations at four
locations within 10 Km radius of the steel plant at Bhilai. at
The measurements were carried out on 8 - hourly basis each
sampling site for one month in each season , namely winter,
rainy and summer. The SPM values were also determined. The
meteorological data were also recorded. The SPM levels were
found to exceed the maximum permissible limit at all the
sampling sites during the entire period of the air monito
ring. The geo - environmental impact of the steel industry,
in terms of increased particulate presence on a permanent
basis 1 in the ambient atmosphere upto a distance of 10 Km
around the steel plant was thus established. Similarly, the
so2 - level was found to exceed the prescribed limit at one
site within the 5 - Km radius during the winter and summer
seasons. At two sites within the 5 - Km radius 1 the NOx
level was found to exceed the prescribed limit during the
summer season.
The presence of so2 and NOx at enhancedlevels in the
steel plant area having been confirmed , investigations of
acid rain formation in the area were undertaken. For this
purpose , four sampling sites for the collection of rain
each month for a fUll year period were arrangem.The details
of the total rainfall in particular months. and other
metereological data of the area were also recorded. Key
parilmeters such at' pH 1 conductance 1 'l'DS 1
nitrate 1 ca 1 Mg 1 Na 1 K 1 Pb and Hg were
by standard techniques i)1 all the rain water
pll values of the rain water were found to be
BU
sulphate ' determined
samples. The
in a range
of 5.60 - 8.10. The causes of the variations in the pH
values were identified. The values of the other parameters
were explained in terms of the pollution scenario of the
respective locations and the meteorological data of the Of
area.,.._special concern were the findings related to the
presence of lead and mercury in the rain water samples
which showed 10.0 - 800.0 pg I 1 of lead and 1.0 - 16.0
pg I 1 of mercury. The· rains were thus found to introduce
extreneous amounts of lead and mercury) both of which are known for their toxic nature~to the natural water streams
and surface soils.
Chhattisgarh being a predominant area for the
limestone and dolomite deposits 1 a study for the interac
tion between the acidity of the rain water and these
carbonate rocks was under=taken. It was found that nitric
acid content of the rain water has a higher corrossivity
for these carbonate rocks compared to the acidity of .s
H2so4 • The cerros;ve effect en dolomite was found to be
smaller than that on limestone. Kinetically~dolomite was
found to be a faster neutralizer of H2so4 - acidity. High
est turbidity { TSS ) was noticed during the dolomite
HN03 interaction. It was found that one litre of acid rain
having a pH of 4.35 could destroy upto a maximum of 181.5
mg of limestone and 158.6 mg of dolomite mineralslbesides
contributing corresponding hardnesses to natural water
resources. Similar studies carried out
indicated only a negligible impact.
with iron ore
A detailed study to evaluate the rate of marble
damage by the acidity of this nature was also undertaken.
For this pUrpose 1 a laboratory modelling of the marble -
acidity interaction was carried out. The data obtained •
showed that the presence of 502
even at 1 ppm level caused
a damage to the marble surface at a measurable rate. The
data obtained from the modelling indicated that a
sustained presence of 502 at levels of 100 , 50 , 10 , 5
and 1 ppm would be able to wipe out 1 em thickness of the
marble stones in durations of 4.31 , 8.19 , 31.24 , 69.02
and 83.02 years respectively.
The findings were considered useful in evalua-
ting the life span of marble structures of
importance on exposure to so2 pollution.
monumental
Slags which are discharged from steel plants in
massive amounts have , on chemical analysis , been found
to contain sulphides upto 0.66 % ~ It was considered
useful to examine the effect of the acid rains of steel
plant origin with the slags of the same origin. The
interaction study usi~g an acid rain water ( pH 5.60 )
and the slag showed that 2.3 % of the slag-sulphide
was decomposable by the rain water resulting in
evolution of the hydrogen sulphide gas. rfa volume of
of the rain water washed 1 tonne of the slag matter in a
period of 72 hours 1 a total of 14.o litres of H2s at NTP
would be evolved. Higher acidities of the water were found
to evolve much higher volumes of the H2s gas.
rains have thus been found associated with an
The acid
additional
factor which describes their capabilities to evolve hydro
gen sulphide , a hazardous gaseous pollutant , on coming
in contact with sulphide-bearing materials
Two isolated examples of environmental interest
were also inve~tigated. One of these was related to the examination of ~now melt water brought from Cleveland (USA).
The snow melt water indicated a pH of 4.85 which comes well •
within the range of acid precipi~ation. The conclusion drawn was that acid precipitations are of common occurrence
in th~ industrial townrbf developed countries such as USA. The other example was related to the abruptly high level of acidity ( pH- 3.00 ) noticed in the rain water in the
Bilaspur town of M.P. on comparing with the pH values of rain water samples collected a day before and a day ~fter
the acid rain eYent ~ it was inferred that the acid rain episode was the most probable consequence of the release of gases of acidic nature from a sulphuric acid plant located few Kms away from the site of rain water collection.
----------------~---------
B!J
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