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Impact of monsoon precipitation
on
soil's heavy metal content
acrossdifferent urban land covers
in Karachi
Bilal Aslam Qureshi*,Zahida Karim and Majid Mumtaz
Department of Chemistry, University of Karachi
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The seasonal precipitation can influence the
average concentration and spatial distribution of
the metals in urban soil via:
Facilitating the sinkingof airborne metal and
Elution and relocation via floodwater runoffs
Some studies, such as Kumar and Srikantaswamy
(2012) reported the seasonal heavy metal
concentration of soil in the sequence of
Monsoon < post-monsoon < pre-monsoon
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Urban ecosystem is a complex composite of
both the natural and anthropogenic factors
Natural factors: The local climate, geology
and the geographical characteristics etc.
Anthropogenic factors: Population and
settlement patterns, exploitation of resourcesand behavior of
the human inhabitants
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Dynamics of an urban environ
(Marzluff et al., 2008)
Present study
Land cover pattern,
Seasonal precipitation
associated changes inspatial dist. of
soilsheavy metal
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In Karachi, monsoon occur from
June through September.
The average monsoon rainfall for
2011 was 436.5 mm...
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The land use and land cover (LULC) are two of the
most important attributes of urban ecosystem
Karachi has a highly diverse Land use/ Land cover
(LULC)
Dominant Land covers include soil and impervious
surface
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Soil is a dynamic environmental compartment
Every soil contains some natural amounts of
heavy metals (backgrounds)
Human activities (e.g. soil excavation and land
filling drainage of waste-fluids, power
generation and distribution, transportation etc.
also add metal to soil
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Besides Lead, automobile traffic is an
important anthropogenic source of anothergroup of heavy metals
including Cu and Zn
in urban environment
Engine wear, the wear of tires and the
associated moving parts, leaks and spills
from batteries and radiatorsall contributethese heavy metals to
the immediate
environment
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The effect of rain-water runoff on a metals
concentration in soil is related to its mobility
through soil profile
A greater mobility should be followed by an
elevation in metal concentration in soil afterrain, while low
mobility and more solubility in
water would result in washing away during
rainfall
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Our research question
What will be the effect of rainfall on the heavymetal
concentration of urban soils across
different land uses/ Land covers in Karachi?
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Experimental
Soil samples were collected at depth of 0
10 cm from 30 different sites during July,
2011(PRM) and October, 2011(POM)
Samples were air dried, ground, and sieved
through a 2-mm nylon sieve
Samples were air dried and digested using a
strong acid (HNO3HClO4) pseudo-total
digestion method (Lee et al.2006) and
analyzed by using Flame atomic absorption
spectrometer
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Sampling Sites
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LandSat TM image of Karachi, Dec. 2010
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Estimated Soil Land cover in area of Study
100
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Impervious Land cover in area of Study
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Statistical summary of the metal
content of soil samples
On the basis of paired-t test, it was found that themeans of
concentrations of Cu and Zn did not changesignificantly at = 0.05
by the rain
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0.000
20.000
40.000
60.000
80.000
100.000
1 2 3 6 12 15 17 18 19 20 21 22 23 24 25 26 27 28 29 30 35 38 39
41 42 46 48 49 52 54
Cu/PRM
Cu/POM
0.000
50.000
100.000
150.000
200.000
250.000
1 2 3 6 12 15 17 18 19 20 21 22 23 24 25 26 27 28 29 30 35 38 39
41 42 46 48 49 52 54
Zn/PRM
Zn/POM
Post Monsoon Metal Variation in soil
(x-axis: Location 1,2,3)
Sampling Locations
Sampling Locations
Cumg/kgofsoil
Znmg/kgofsoil
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Correlation among soils Cu and Zn(x-axis; Cu & y-axis;
Zn)
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Spatial Distribution of Cu in soil
in PRM(Left) & POM(Right) Scenarios
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Spatial variation of Cu in soil in PRM to POM transition
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Spatial Patterns of land cover
and variation of Cu in soil
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Spatial Distribution of Zn in soil
in PRM(Left) & POM(Right) Scenarios.
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Spatial variation of Zn in soil in PRM to POM transition
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Spatial Patterns of land cover
and variation of Zn in soil
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Traffic Congestion Points
Mehdi et al. (2011)
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Study Area
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Land cover, seasonal
variation of Cu in soil and
traffic congestion points
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Land cover, seasonal variation
of Zn in soil and traffic
congestion points
C l i
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Conclusion Mean concentration of Cu and Zn do not show
significant
change after rain.
A significant correlation between Cu & Zn metals, showingthe
common source.
Spatial distribution of both metals in soil shows no
apparent association with land use in either season.
The seasonal variation in soils Cu and Zn contents is
evidently influenced by associated land cover.
The increase in the concentrations of the said metals in
POM scenario seemed to be the contribution of road
traffic.
In general, the results inferred the contribution of
meteorological factor, anthropogenic activity and the land
cover on the variation of heavy metals in urban soils.
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Acknowledgments
The authors are grateful for the financial
support by the Dean Faculty of Science,
University of Karachi
Authors are also thankful to the Pakistan Council
of Scientific and Industrial Research(PCSIR),
Karachi, for both their technical and intellectual
assistance in this study
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References
Marzluff JM, Shulenberger E, Endlicher W, Alberti M, Bradley G,
Ryan C,Simon U, Zum Brunnen C, 2008. Urban Ecology- An
International perspectiveon the interaction between human and
nature. Springer Science andBusiness Media, New York.
Lee CS, Li XD, Shi WZ, 2006. Metal contamination in urban,
suburban, andcountry park soils of Hong Kong: A study based on GIS
and multivariatestatistics. Sci. Total Environ,356:45-61.
Mehdi MR, Kim M, Seong JC, Arsalan MH , 2011. Spatio-temporal
patterns ofroad traffic noise pollution in Karachi, Pakistan.
Environment International,37(1): 97-104.
Kumar DS, Srikantaswamy S, 2012. Seasonal variation of heavy
metal inindustrial zone soil of Mysore city, Karnataka, India. Int.
J. Basic Appl. Chem,2(2):33-41.
