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The presence of heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs) in atmospheric
deposition was investigated for nine sampling sites in Kandy, Sri Lanka, which is a typical city in the
developing world with significant traffic congestion. Deposition samples were analyzed for Al, Cr, Mn,
Fe, Ni, Cu, Zn, Cd, and Pb, which are HMs common to urban environments, following the method of
USEPA 200.8. Crocynia pyxinoides, a lichen species was also analyzed from same sampling sites.
USEPA priority 16 PAHs were analyzed following the method of USEPA 610. Human and ecological
health risks were assessed using risk indexes, while the cancer risk was evaluated based on life time
daily cancer risk. Al and Fe were found in high concentrations (0.007 – 115.4 mg/m2
/day) due to the
presence of natural sources, but may also be re-suspended by vehicular traffic. Relatively high
concentrations of toxic metals such as Cr and Pb were also found (0.5 and 0.65 mg/m2
/day
respectively). High Zn loads can be attributed to vehicular emissions and Zn coated roofing materials.
The metal concentrations among the sampling sites significantly differ (p<0.001) depending on the
traffic conditions. Only five PAHs, namely, Phenanthrene, Anthracene, Fluoranthene, Pyrene, and
Napthalene were found in deposition loads. The changing patterns of HMs were similar in both
lichen and deposition samples as Fe>Al>Zn>Pb>Mn>Cu>Cr>Ni> Cd. Contamination factor and geoaccumulation index showed that Al and Fe are at uncontaminated levels currently and other metals
are in the range of uncontaminated to contaminated levels, but with the potential to become
exacerbated in the long-term. The risk values for children (for Fe, HI-0.58) were higher than that for
adults (for Fe, HI-0.06), indicating that children may be subjected to potentially higher health risks.
Regarding PAHs, all the cancer risk values are above the acceptable levels. The ecological risk levels
on HMs were also higher,with Cd responsible for the highest ecological risk. The study provided
fundamental knowledge to determine appropriate mitigation measures in relation to HM and PAH
pollution in city environments in the developing world, where to-date only very limited research has
been undertaken
