H M D V Herath

H M T G A Pitawala

Jagath Gunathilake

T Y S Dalugoda

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Proceedings to 29th Technical Sessions of Geological Society of Sri Lanka, 2013, 127-130 
Published Online 22nd February 2013 (http://www.gsslweb.org) 
 
 Copyright © 2013  GSSL       127 
Heavy Metal Contamination in Road Deposited 
Sediments in Colombo Urban Area 
H.M.D.V. Herath
1,2*
, H.M.T.G.A. Pitawala
1
, Jagath Gunathilake
1
, T.Y.S. Dalugoda
2
 
(1). Department of Geology, University of Peradeniya 
(2). Postgraduate Institute of Science, University of Peradeniya 
E mail: herathdilmi@yahoo.com 
 
1. Introduction 
Heavy metal pollution is a persistent problem in 
many urban cities in the world. As a result, 
millions of people living in and around urban 
centres are exposed to an unnatural and 
unhealthy environment which may cause a 
serious threat for the human health as well as 
for the environment. With the exception of 
natural and bedrock sources, most of heavy 
metal pollutants are anthropogenic in origin 
(Kim et al., 1998). 
 
Atmospheric pollution is one of the major 
sources of heavy metal contamination of water 
and soil. Heavy metals can accumulate in 
topsoil from atmospheric deposition by 
sedimentation. Top soils and road deposited 
sediments (RDS) are useful probes to 
understand the atmospheric pollution of an 
urban area (Li et al., 2001). Dusts deposited on 
the roads are usually called road dusts, road-
deposited sediments or street dusts (Wei et al., 
2008). These can also acts as a significant 
pollution source, especially when storm water 
runoff removes a large part of the RDS and its 
associated metals causing a pollution threat to 
the surface and sub-surface water resources 
(Singh, 2009).  
 
Population of Sri Lanka is of 19.7 million of 
which more than 15% lives in the urban areas. 
Colombo Metropolitan Region (CMR) covers 
an area of 37.29 km
2
. More than 80% of 
industries of the country operate in close 
proximity to Colombo (Asian Development 
Bank report, 2006). Relative humidity in 
Colombo varies from 75–95 % and receives an 
average annual rainfall of approximately 2,400 
mm. The mean annual temperature in Colombo 
is approximately 25 to 28 
0
C with a small 
variation in the mean monthly temperatures. 
The wind flow in to the city varies depending 
on monsoonal conditions. Wind mainly flows 
from the north western direction and moves 
across the city towards the central parts of the 
country. Lateritic peaty soil cover is 
predominated in the area (Cooray, 1984).  
 
Information on heavy metals in road deposited 
sediments of urban environments of Sri Lanka 
is not available. Hence, there is a need to 
identify the point and non-point sources of 
contaminants and the level of toxic 
contaminations in the urban environment. 
Therefore this study focuses to investigate the 
heavy metal and organic carbon concentrations 
in RDS of three different land use areas in 
CMR. 
 
2. Methodology 
 
2.1. Sampling 
Forty six (46) road deposited sediment samples 
were collected within the CMR. Sample sites 
were selected considering the intensity of 
commercial and industrial activities as well as 
the density of residential.  Industrialised 
Proceedings to 29th Technical Sessions of Geological Society of Sri Lanka, 2013, 127-130 
  Published Online 22nd February 2013 (http://www.gsslweb.org) 
128                                                                                                                                              Copyright © 2013  GSSL 
Rathmalana area, Colombo city centre as being 
commercialised area and residential areas in the 
small cities were also selected for the sampling 
(Figure. 1). Samples were collected by using a 
hand shovel in to polythene bags and 
transported to the laboratory for further 
analyses. 
Figure 1 - Study area in and around Colombo 
Metropolitan Region. 
 
2.2. Laboratory Analysis 
Samples were dried, crushed, sieved (sieve size 
0.63 mm) and the pan fraction was selected. 
Organic matter content of all sediment samples 
was measured by loss on ignition method 
(Robertson and Taylor, 2007). Acid digestion 
of 0.1g of these samples were done by 
microwave digestion method using HNO3, 
HClO4 and HF (HNO3:HClO4: HF = 7:2:1). 
Concentrations of Cu, Zn, Pb, Fe, Mn, in 
digested samples were determined by using 
flame atomic absorption spectrophotometer 
(Varian AA240FS). 
 
 
 
 
 
 
 
 
3. Results and Discussion 
 
3.1. Total Organic Matter Content 
Obtained results show that the total organic 
matter content increases in the order of 
industrial < commercial < residential area 
(Table 1) within a range of 1.4%-17.8%. All 
these values are relatively higher than the 
values observed in the RDS samples from other 
cities of the world such as Manchester, UK 
(Robertson and Taylor, 2007) and in Zhenjiang, 
a city in the eastern China (Zhu et al., 2007).  
Table 1 - Total organic matter content in RDS 
 
 
3.2. Total Heavy Metal Concentration 
The elemental concentrations show variations 
among the three sampling groups. Most 
abundant element is Fe which is in the range of 
25,322 – 97,582ppm (Table. 2) in all areas. The 
average values of samples collected from 
commercial areas have higher concentrations of 
Zn, Cu and Pb (349, 180, 444ppm 
respectively). Manganese (Mn) concentration in 
commercial and industrial areas are nearly 
equal (537 and 544ppm respectively) while 
residential area has a relatively low value 
(207ppm).  
 
Compared to other cities, Colombo city is less 
contaminated in terms of Zn and Pb 
concentrations while Cu concentrations are 
nearly equal (Figure. 2). Although Zn and Pb 
concentrations are lower than other cities, still 
those results are remarkably high when we 
consider the intensity of urbanisation, traffic 
density, population density and industrial 
density of the other cities of the world. 
Area OM % 
Residential 12.4 
Commercial 9.4 
Industrial 6.4 
Proceedings to 29th Technical Sessions of Geological Society of Sri Lanka, 2013, 127-130 
Published Online 22nd February 2013 (http://www.gsslweb.org) 
 
 Copyright © 2013  GSSL       129 
Figure 2 - Comparison of elemental 
concentration in RDS samples collected from 
three different parts of the world with this 
study. 
Table 2 - Elemental concentrations (in 
ppm) of RDS in different land used 
areas. 
 
 
Zinc (Zn), Cu, Mn and Fe contents in the RDS 
samples are significantly higher compared to 
those in the lateritic peaty soil cover in the area 
(Dissanayake, 1986). This indicates that 
contamination of the city by means of heavy 
metals and organic matter is considerably high 
although it has been heavily urbanised very 
recently.  
 
3.3. Elemental Correlation 
Significant correlation of Cu/Pb, Cu/Zn and 
Zn/Pb indicate that these metal pollutants have 
been released from common sources. No such 
significant correlations were observed between 
Mn and Fe (Table. 3). Further Zn, Cu and Pb 
show high positive correlation with the contents 
of organic matter in the samples. 
 
 
 
 
 
 
 
 
 
 
 
 
 
Table 3 - Correlation coefficient of measured 
elements and organic matter (OM) of RDS 
 
Zn Cu Pb Fe Mn OM 
Zn 1.0 
 
 
  
 
Cu 0.7 1.0  
  
 
Pb 0.7 0.9 1.0 
  
 
Cr 0.2 0.4 0.3 
  
 
Fe 0.2 0.4 0.2 1.0 
 
 
Mn 0.2 0.3 0.0 0.6 1.0  
OM 0.7 0.9 1.0 0.2 0.0 1.0 
High percentage of organic matter in sediments 
contributes significantly to the bioavailability 
of heavy metals in sediments (Ongeri et al., 
2010). Organic matter provides binding sites 
for metal ions influencing their bioavailability, 
toxicity and general transport behaviour. Due to 
the higher percentages of organic matter in 
Colombo RDS samples, there is a high 
possibility to increases the content of bio-
available toxic metals. 
 
 
 
 
 
Element Residential Commercial Industrial 
 Mean Range Mean Range Mean Range 
Zn 253 455-53 349 625-135 285 929-73 
Cu 57 98-30 180 1181-29 108 260-50 
Pb N/A N/A 444 5591-b.d. 23 73-b.d. 
Mn 207 298-109 537 675-458 544 1019-300 
Fe 41,645 50,760-26,360 39,697 52,679-29,986 45,373 97,582-25,322 
Proceedings to 29th Technical Sessions of Geological Society of Sri Lanka, 2013, 127-130 
  Published Online 22nd February 2013 (http://www.gsslweb.org) 
130                                                                                                                                              Copyright © 2013  GSSL 
4. Conclusions 
Present results suggest that the organic matter 
content in RDS of Colombo metropolitan 
region is high. Heavy metal concentrations 
show variations among different land used 
areas while metal pollution in the area increases 
in the order of residential < industrial < 
commercial area. When compared with the 
other parts of the world, CMR is less polluted 
with respect to Zn and Pb. However Cu 
pollution is high. Zinc (Zn), Cu and Pb may 
have released from common sources. 
 
 
5. Acknowledgments 
This work was financially supported by the 
National Research Council, Sri Lanka (Grant 
No: NRC-11-142). 
 
 
6. References 
 
Cooray, P.G. (1984). An introduction to the 
geology of Sri Lanka (Ceylon). National 
Museum, Sri Lanka. 
Kim, K.W., Myung, J.H., Ahn, J.S. Chon, H.T. 
(1998). Heavy metal contamination in 
dusts and stream sediments in the Taejon 
area, Korea, Journal of Geochemical 
Exploration, Vol. 64,  p.409–419. 
Li, X., Poon, C., Liu, P.S. (2001). Heavy metal 
contamination of urban soils and street 
dusts in Hong Kong, Applied 
Geochemistry, Vol. 16, p.1361-1368.  
Lu, S.G., Bai, S.Q. (2008). Contamination and 
potential mobility assessment of heavy 
metals in urban soils of Hangzhou, China: 
relationship with different land uses, 
Environ Earth Sci, Vol. 60, p.1481–1490.  
Ongeri, D.M.K., Lalah J.O., Wandiga, S.O. 
(2010). Speciation of Cd, Cu, Zn, Fe and 
Pb in sediments sampled from Lake 
Victoria basin, Kenya, Environmentalist, 
Vol. 30, p.254–259.  
Robertson, D.J., Taylor, K.G. (2007). Temporal 
Variability of Metal Contamination in 
Urban Road-deposited Sediment in 
Manchester, UK: Implications for Urban 
Pollution Monitoring, Water Air Soil 
Pollut., Vol. 186, p. 209–220.  
Singh, A.K. (2009). Elemental chemistry and 
geochemical partitioning of heavy metals 
in road dust from Dhanbad and Bokaro 
regions, India, Environ Earth Sci., Vol. 
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Wei, B., Jiang, F., Li, X., Mu, S. (2008). Heavy 
metal induced ecological risk in the city of 
Urumqi, NW China, Environ Monit 
Assess, Vol. 160, p. 33–45.  
 


Proceedings to 29 th Technical Sessions of Geological Society of Sri Lanka

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