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Soil pollution with special reference to heavy metal toxicity
Bidhan Chandra Krishi ViswavidyalayaMohanpur-741252 District: Nadia West BengalMohanpur-741252 District: Nadia West Bengal
Dr. P.K. ManiLecturer (Res), Sr. Scale
Department of Agricultural Chemistry & Soil ScienceAICRP on Cropping Systems, Kalyani Centre
Winter school presentation
Fig. 1: How healthy soil is linked with healthy people
Rocks in Earth’scrust
Air
Soil
Water
Plants
Birds
Domesticanimals
Fish
Humans
Source: Brady, N. C. The nature and properties of soil, 1994 Sources of heavy metals and their cycling in the soil-water-air organism ecosystem.
Industrial ProductsBurned fuelFertilizersPesticides
It should be noted that the content of metals in tissue generally builds up from left to right, indicating the vulnerability of humans to heavy metal toxicity
Heavy metalHeavy metal
Transition metals
Ia IIaIIIa IVa Va VIa VIIa
Ib IIb
Lanthanides
Actinides
Oxidative stress: Redox active transition metals (e.g. Fe2+, Cu2+) produce free radicals
Replace other essential metals in pigments and enzymes
Some metal ions (Hg2+, Cu2+) react to thiol groups to interfere protein structure and functions
Some metals occur as radioactive isotopes (238U, 137Cs etc.) to pose health risks`
Why metals are toxic to living organisms?Why metals are toxic to living organisms?
Chemical Major uses and sources of soil contamination
Arsenic Pesticides, plant desiccants, animal feed additives, coal and petroleum, mine tailings and detergents
Cadmium Electroplating, pigments for plastics and paints, plastic stabilizers and batteries, fertilizers
Chromium Stainless steel, chrome–plated metals, pigments and refractory brick manufacture
Copper Mine tailings, fly ash, fertilizers, wind blown copper-containing dust
Lead Combustion of oil, gasoline, and coal; iron and steel production
Mercury Pesticides, catalysts for synthetic polymers, metallurgy, thermometers
Nickel Combustion of coal, gasoline, and oil; alloy manufacture, electroplating, batteries
Zinc Galvanized iron and steel, alloys, batteries, brass, rubber manufacture
Source: Moore and Ramamoorthy (1984)
Anthropogenic sources of heavy
metals in soil
TanneryBatteryDistillery
Steel Fly ash
Electroplating Mining
Smelting
Global Emissions of trace Metals into theGlobal Emissions of trace Metals into the Atmosphere, Water and Soil Atmosphere, Water and Soil
ElementAir Water Soil
(in 1000 metric tones/yr)
As 18.8 41.0 82.0Cd 7.6 9.4 22.0Cr 30.0 142.0 896.0Cu 35.0 112.0 954.0Hg 3.6 4.6 8.3Mn 38.0 262.0 1670.0Mo 3.3 11.0 88.0Ni 56.0 113.0 325.0Pb 332.0 138.0 796.0Sb 3.5 18.0 26.0Vd 86.0 12.0 132.0Zn 132.0 226.0 1372.0
Third North Sea Conference( Nriagu,1988)
ElementElement Essential or beneficial toEssential or beneficial to Potential toxicity toPotential toxicity to PlantsPlants AnimalsAnimals PlantsPlants AnimalsAnimalsArsenic (As)Arsenic (As) NoNo YesYes YesYes YesYes
CadmiumCadmium(Cd)(Cd) NoNo NoNo YesYes YesYes
ChromiumChromium(Cr)(Cr) NoNo YesYes YesYes DUDUCobalt (Co)Cobalt (Co) YesYes YesYes YesYes YesYesCopper (Cu)Copper (Cu) YesYes YesYes YesYes YesYesbb
Lead (Pb)Lead (Pb) NoNo NoNo YesYes YesYesMarcury (Hg)Marcury (Hg) NoNo NoNo DUDUaa YesYes
Molyb (Mo)Molyb (Mo) YesYes YesYes DUDU YesYesbb (5-20 ppm) (5-20 ppm)
Nickel (Ni)Nickel (Ni) NoNo YesYes YesYes YesYesSeSe YesYes YesYes YesYes Yes(4ppm)Yes(4ppm)Zinc (Zn)Zinc (Zn) YesYes YesYes DUDU DUDUa DU = Critical data on limits unavailable.b Toxic to ruminants (sheep, cattle).After Adriano 1986.
Sewage sludge –a potential threat to heavy metal pollution in Indian soils
Fly-Ash: A meanace to the environment
Ground water pollution- Nitrate and ArsenicGround water pollution- Nitrate and Arsenic
Nuclear fallout and radioactive hazardsNuclear fallout and radioactive hazards
Inorganic fertilsersInorganic fertilsers
Tanery efflents and Waste waterTanery efflents and Waste water
Some of the potentially adverse Environmental and Health effects Caused by forms of Nitrogen
Effect Causative AgentEnvironmental quality
Eutrophication Nitrogen sources in surface waters
Corrosive damage HNO3 in rainfall (acid rain)
Ozone layer depletion Nitrous oxides from fuels, denitrificationAnd industrial stack emissions
Human Health
Methemoglobinemia Excess NO3– and NO2
– in water and food
In infants, livestock
Respiratory illness PANs and other nitrogen oxides
Cancer Nitrosamines from NO2– and
secondary Amines in food Soils- An Introduction to Soils and Plant Growth, Miller and Donahue
Heavy metal concentrations in soil amendments, expressed in Heavy metal concentrations in soil amendments, expressed in ppmppmon a dry weight basison a dry weight basis
Soil amendment Cd Co Cr Cu Ni Pb Zn
Triple superphosphate 9 5 92 3 36 3 108(0-46-0)
Urea (46-0-0) <0.1 <1 <3 <0.4 <1 <3 <1
Potassium chloride <0.1 2 <3 <0.6 4 3 <1(0-0-60)
Agricultural lime <0.1 <1 <3 <0.2 5 <3 <2
Cow manure 1 6 56 62 29 16 71
Sewage sludgea 5 5 350 660 35 980 800
After Freedman and Hutchinson 1981, except aWebber and Nichols 1995
Contents of some heavy metals in fertilizers and sludges
Source Metal mg/kg dry material
Cd Cr Cu Pb Zn
Ammonim Niitrate (A/N)
1.1 2.5 3.6 5.4 11.7
SSP 16.6 157.0 22.6 20.6 244.0
Compound 8-10-8
4.9 54.3 8.3 3.2 97.5
Sewage Sludge 20.0 500.0 250.0 700.0 3000.0
Source: Pain et al., 1991
Heavy metal composition of sewage sludge from different cities in India
City Cu Zn Cd Cr Ni Pb
mg/kg
Ahmedabad
535 2147 3.5 60.4 32.3 76.8
Delhi 440 1610 5.5 53.5 81.5 34.5
Nagpur 272 832 1.5 49.2 14.8 24.3
Chennai 210 935 8.3 38.5 60.5 16.6
Jaipur 265 1720 7.3 17.6 37.5 66.9
Source : Maity et al (1992).
Reported range (mg/kg dry digested sludge)
Element
Minimum Maximum As 1.1 230 Cd 1.0 3410 Co 11.3 2990 Cu 84.0 17000 Cr 10.0 99000 F 80.1 33500 Hg 0.60 56 Mn 32.0 9870 Pb 13.0 26000 Se 1.70 17.2 Zn 101.0 49000
Concentrations of Trace elements in Municipal Sewage Sludges
Source: Lagon, T.J. (1990) Advances in Soil Science, Vol. 11
Accumulation of Heavy Metals in Soil and Plant (mg/g) Zn Cu Pb Cd Cr
Soils of Dhapa 1038-1256 154-196 79-113 0.38-0.52 9.1-17.0
Spinach 320-340 60-72 60-82 0.8-2.2 6.5-15.8
CauliflowerHead
300-1100 20-30 30-90 Trace 5.2-5.7
Source: S. K. Gupta et al., 1997, Calcutta University Accumulation of Heavy Metals in Rohu fish (1.5 kg) on dry weight Basis (g/g)
Parts Zn Cu Pb Cd Cr
Brain 3.2 trace 2.9 0.4 11.3
Muscle 29.1 3.4 2.4 0.5 0.9
Liver 53.1 79.5 3.3 6.1 3.2
Kidney 62.6 8.9 11.9 12.3 14.9
Source: Dr. R. N. Bhattacharyya, Head, CPCB, Kolkata, 1997
DTPA-extractable heavy metal in soils under different crops irrigated with sewage and underground water
Crop Source of irrigation
water
Zn Fe Cu Mn Cd
mg/kg
Berseem Sewage 13.4 75.3 24.4 33.2 0.119
Underground 4.2 38.0 7.8 28.4 0.074
Spinach Sewage 41.2 65.6 32.2 28.8 0.253
Underground 4.2 59.4 7.0 24.4 0.079
Coriander Sewage 21.1 69.0 49.4 23.0 0.208
Underground 6.6 32.4 9.5 18.4 0.054
Source : Sharma and Kansal (1986).
Some characteristics of waste water from domestic and industrial locations in Ludhiana – An industrial city of Punjab
Location pH BOD Cr Ni CN
mg/kg
ElectroplatingIndustry
6.2-7.2 60-380 0.2-2.5 1.0-3.0 0.42-0.97
Sugar Industry
7.1-7.9 1058-1640
- - -
Paper Industry 7.0-10.1 560-1113 - - -
Household 6.7-7.8 80-460 0.1-0.2 0.2-2.0 0.05-0.07
Max. limits for disposal on agril. land
5.5-9.0 100 0.1 0.005 0.2
Source : Tiwana et al (1987).
Tolerance limits for disposal of tannery effluentsParameters Effluents to be discharged
Into inland surface water
On land for irrigation
pH 6.0-9.0 6.0-9.0
BOD (mg.L-1) 30 100
Suspend solids 100 200
Chloride (as Cl) 1000 200
Cr 2.0 2.0
Sulphides 2.0 -
Na+ - 60
Oil and grease 10 10
Source: Environmental (Protection ) Rules (1986)
Recommended maximum concentrations (ppm) of heavy metals in soils based on their cation exchange capacities (CEC)
CECa Cu Co Hg Cd Cr Zn Pb Ni
CEC>15 50 34 0.14 2.4 120 160 70 60
CEC<15 25 >17 0.07 1.2 0 80 35 30
aMeasured as milliequivalents per 100 grams.Source: Giroux et al. 1992.
“In agriculture CEC is next to photosynthesis ”-C.E .Marshal
Ash (generated from coal combustion) which is fine and carried away with the flue gases is known as FA
Fly ash (FA) is finely divided residue resulting from the combustion of pulverized bituminous coal or lignite
FA is gray in colour, abrasive, acidic, refractory in nature, fineness 4000-8000 sq. cm/g, size 5-120 equivalent diameterFA is essentially an Amorphous ferroaluminosilicate minerals Concentration of heavy metals in sized fractions of Fly-ashParticle size Cr Mn Ni Pb Cd Cu
µg/g (average)>150 67 355 86 86 15 67
150-106 78 368 98 54 16 66106-75 86 425 98 62 15 6475-53 80 445 102 59 13 69<53 87 390 116 56 13 80
Average 80 396 100 57 14 61 Fulekar and Dave, 1986Fulekar and Dave, 1986
Concentration of HM in coal ash generated in power plants of West Bengal
BTPS KTPS STPS DTPS FSTPS
Cr 20-100 40-80 80-200 <10-20 120-180Cu 10-25 20-30 10-15 <10-15 10-20Pb 10-20 10-40 10-35 <10-50 10-45Mn 150-1000 300-2100 150-800 200-1000 400-800Ni 10-35 74 - - -V 15-90 - 15-150 - -Mo - <10 <10 <10 <10Zn - 200 200 200 200Cd - BDL - - -
After: Saha, A. K., CSME, Kolkata
Nitrate concentration in Ground waters amples from Tubewells located in Cultivated areas of Punjab
BlockBlockNo. of No. of samplessamples
Mean NOMean NO3 3
mg/lmg/lN-fert.applicationN-fert.application
kg/ha/yrkg/ha/yr
DehlonDehlon 8484 17.017.0 249.0249.0
LudhianaLudhiana 3333 13.813.8 258.0258.0
SudharSudhar 4343 17.417.4 242.0242.0
KartarpurKartarpur 3434 12.112.1 193.0193.0
JandialaguruJandialaguru 2424 18.318.3 172.0172.0
MalerkotlaMalerkotla 1818 17.817.8 151.0151.0
Bajwa et al. 1992Bajwa et al. 1992
Gary Bañuelos, Soil Scientist with the USDA Agricultural Research Service, inspects the leaves of a transgenic Indian mustardIndian mustard plant used to remove seleniumselenium from contaminated soil. (Photo by Stella Zambrzuski, USDA ARS)
Canola and Kenaf plants do a good job of cleaning up of soil and water contaminated with Selenium
The ultimate solution is to volatilise Se completely from the ecosystem using plants like Indian mustardIndian mustard and pickleweedpickleweed that convert toxic selenateselenate and seleniteselenite into volatile non-toxic Se forms such as dimethyl selenidedimethyl selenide. A recent breakthrough has enabled Prof Terry'Terry's team to genetically engineer Indian mustard to enhance the rate of Se volatilisation. Both Prof Terry and Dr David Salt10 from Purdue University are looking at ways to use plants like Indian mustard11 to clean up cadmium-laden soils.
Arsenic source in groundwater in the Ganga basin
Holocene periodHolocene period
Basalt rock
NArsenic affected districts of West Bengal, India
108 blocks108 blocks
Air As2O5 As2O3 (CH3)3As (CH3)2AsO(OH) Water Oxidation H3AsO4 H3AsO3 (CH3)3As (CH3)2AsH microbes Sediment biomethylation AsO2(OH)2
- AsO(OH) (CH3)2AsO(OH) redn. FeAsO4 As2S3 (CH3)3As
Arsenic speciation in soil, water and air
The Eh -pH diagram for As at 250C,1 atm. with total arsenic 10-5 mol L-1 and total sulfur 10-3 mol L-1 (Ferguson and Gavis,1972)
Eh , V
olts
pH
Source: Arsenic is a new terror; Asit Kumar Roy; Desh
DRAWDOWN
Radius of influence
Cone of Depression
WTVadose zone
Arsenopyrite
Darcy’s Law
Pitticite
Crop Arsenic conc. (mg/kg) at harvest
Leaf Stem Root Eco. ProduceEle-foot-yam 4.30 8.0 - 4.0Green gram 5.10 4.9 4.7 4.3Cowpea 4.91 5.1 5.2 2.1Maize 3.30 6.2 5.2 2.6Rice (boro) 10.2 5.7 5.9 10.0Jute 3.5 8.0 6.8 4.0Potato 3.9 9.3 - 5.9Mustard 7.1 9.8 5.7 3.3Ground nut 2.0 2.0 2.2 4.0Sesame 2.0 2.0 4.0 0.6 Crops were subjected to irrigation with water containing 0.22 mg As / lit of water Soil had an Olsen-extractable arsenic content of 1.23 to 1.37 mg/kg of soil (initial) Source : Prof. S. K. Sanyal Source : Prof. S. K. Sanyal
Arsenic uptake by different plant parts of crops grown in Gotera, Chakdah
Measured total Arsenic content in the various plant parts
Total arsenic is not so fatal-it is only the Total arsenic is not so fatal-it is only the trivalent form which is highly toxic than trivalent form which is highly toxic than other other formsforms So we need speciation of arsenicSo we need speciation of arsenic
Speciation of arsenic can be done by Flame Speciation of arsenic can be done by Flame Ionisation Atomic Spectrometer (FIAS) Ionisation Atomic Spectrometer (FIAS) attachment in AASattachment in AAS
Mechanism of As mobilization in groundwater in Bengal Basin
Hypothesis1 ‘ Pyrite oxidation hypothesis’ Arsenic rich iron bearing minerals like “Arsenopyrite” may be present in the aquifer sediments. Aresenopyrite is being oxidized by atmospheric oxygen which invades the aquifer in response to lowering of groundwater level (Mandal et al. 1996) Hypothesis 2 ‘Oxyhydroxide reduction hypothesis’ ii) The burial of the sediments, rich in organic matter, has led to strongly reducing groundwater conditions. Arsenic may be released when arsenic-rich iron oxyhydroxides, which are efficient arsenic –scavengers, are reduced in anoxic groundwater. Order of toxicity : AsH3 > (CH3)2AsH, > (CH3)3As >As2O3 >H3AsO3 >As2O5 > H3AsO4 Max. Health permissible limit in drinking water : 0.05 ppm (WHO) Biochemical effects
SH O S + As O- As O-
SH O S enzyme
enzyme
Arsenic affected people of Chakdaha blockArsenic affected people of Chakdaha block
Can Arsenicum 30 reduce the toxicity?Can Arsenicum 30 reduce the toxicity?A
R
S
E
N
I
C
O
S
I
S
Then what is the way out???Then what is the way out???
PHYTOREMEDIATION
THE GREEN-CURE TECHNOLOGY
Natural Microbial Bioremediators On March 24, 1989, an oil tanker ( Exxon Valdez) crashed into a reef
Alaska, spilling 11 million gallons of oil . 10 weeks after the spill, the U.S.E.P.A applied P and N fertilizers to 750 oil-soaked sites.
Hudson River in New York with polychlorinated biphenyls (PCBs) by the Company GEC
Buried anaerobic bacteria strip off chlorines. In the water column, aerobic bacteria cleave the two organic rings of the
PCBs. Other microorganisms degrade the dechlorinated, broken rings into
CO2,H2O,Cl . Natural Plant Bioremediators Hyperaccumulators, cope with excess heavy metals in the environment by
taking them in and sequestering them in vacuoles. Chelation : when the plant combines a pollutant with another molecule,
Organic acids often serve this role. Citric acid, detoxifies cadmium, and malic acid does the same for zinc.
phytochelatins -a class of polypeptides can also bind metals and escort them .
metal-lothioneins - metal-binding proteins
Natural phytoremediators. Sebertia acuminata, a tree ( tropical rain forest of New Caledonia, Australia.) Up to 20 percent of the tree's dry weight is Ni If slashed, the bark oozes a bright green. This plant can perhaps be used to clean up nickel-contaminated soil. Soybeans also preferentially take up nickel from soil. Another phytore-mediator is Astragalus, also know as locoweed (accumulates Se)
Genetically Modified Bioremediators
Super bug-Ananda Mohan Chakrabarty (1980) GEC
The four plasmids in the oil eater gave the bacterium the ability to degrade four components of crude oil. Plasmids are rings of DNA that can be transferred from one cell to another
What is phytoremediation?
“Use of green plants to remove pollutants from the environment or render them harmless”
Salt et al. (1998)
This concept has emerged from a broader philosophy of Bioremediation where besides plants, soil microorganisms are also used for amelioration of organic and inorganic contaminants
Phytoextraction Phytodegradation Rhizofiltration Phytostabilization Phytovolatilization
Phytoremediation
D i f f e r e n t a p p r o a c h e s o f p h y t o r e m e d i a t i o n
A c c u m u l a t io n o f m e t a l s i n s h o o t t i s s u e s f o l l o w e d b y h a r v e s t i n g
U s e o f p l a n t s a n d a s s o c i a t e d m i c r o b e s t o d e g r a d e o r g a n i c p o l l u t a n t s
U s e o f p l a n t r o o t s t o a b s o r b a n d a d s o r b m e t a l s f r o m a q u e o u s w a s t e s t r e a m
R e d u c t i o n i n l e a c h i n g , r u n o f f , s o i l e r o s i o n a n d b i o a v a i l a b i l i t yo f t o x i c m e t a l s
U s e o f p l a n t s t o v o l a t i l i z e p o l l u t a n t s
Advantages and disadvantages of PhytoremediationAdvantages and disadvantages of PhytoremediationAdvantages Limitations
Amendable to a variety of organic and inorganic compounds
Restricted to sites with shallow contamination within rooting zone of remediative plants
In Situ/Ex Situ application possible with effluent/soil
May take up several years to remediate a contaminated site
In Situ applications decrease the amount of soil disturbance
Restricted to sites with low contaminant concn.
Reduces the amount of waste to be landfilled(upto 95%), can be further utilized as bio ore of heavy metals
Harvested plant biomass from phytoextraction may be classified as a hazardous waste
In Situ applications decrease spread of contaminant via air and water
Climatic conditions are limiting factor
HYPERACCUMULATOR
INDICATOR
EXCLUDERPLANT
Metal concentration in Soil
Conceptual response strategies of metal concentration in plant tops in relation to increasing total metal concentrations in soil
Possible fates of pollutants during phytoremediation
Hydrophobicity (log Kow)
Henry’s law constant (Hi)
Pteris vittata (Chinese brake) – a reported hyper-accumulator for arsenic
Chelate-assisted phytoremediation is most promising management practice
Salt et al., 1998
After, Ma et al. 2000
Uptake,transport and metabolism in transgenic A. thaliana plants overexpressing two bacterial genes, arsC and Y-ECS(gamma glutamyl cysteine synthatase.
Tolerance mechanisms for inorganic and organic pollutants in plant cells.
Detoxification generally involves conjugation followed by active sequestration in the vacuole and apoplast,where the pollutant can do the least harm
Pollutant(inorg)
Pollutant(organic)
Cell Wall
VacuoleVacuole
SequestrationSequestration
Conjugation
GSH,Glutathion
MT, Metallothioneins
Phytochelatins
Disposal of hyper-accumulator plant refuse
Harvest
Incineration
Controlled disposal of ash to underground – away from root zone and aquifer
Phytomining
Jade green alkaloid from cut stem of Phyllanthus palawanensis contains 88,580 µg Ni g-1 dry weight
Bio-accumulation coefficients of Brassica sp. at maturity stage
Species Zn Cu Ni Pb Yield*
B. juncea 6.83 3.08 3.21 12.86 25.40
B. campestris
12.48 2.59 13.61 2.56 18.66
B. carinata 11.89 1.94 12.30 17.72 37.70
B. napus 9.87 1.14 8.98 9.37 31.70
B. nigra 9.56 2.04 8.66 7.94 31.04
*Above ground biomass yield expressed in g/potBioaccumulation coefficient: Metal content in plant biomass Labile metal content in soil
Novel Finding!
For the first time Brassica carinata is being reported as a possible
hyper-accumulator for Zn, Ni and Pb
Chhonker et al, 2004Chhonker et al, 2004
Defective baby due to radioactivity is known as Down’s syndrome
Radioactivity due to nuclear fall out leads several pollution to soil
Source of radioactive contamination:
Fallout from testing of nuclear weapons Waste products and effluents from nuclear reactors Sr90 , Cs137, I131
Max. permissible limit of absorbing radiation : 0.5 REM
The chemicals to which life is asked to make its adjustment are . . . the synthetic creations of man's inventive mind, brewed in his laboratories, and having no counterparts in nature.
Rachel CarsonSilent Spring
Upon this handful of soil
Our Survival dependsHusband it & it will
growOur food, fiber & fuel& surround us with
beauty,Abuse it, the soil will
degrade& collaspe taking mankind with it
