ASSESSING HEAVY METAL CONTAMINATION OF SURFACE WATER BODIES ALONG THE MANALI-LEH HIGHWAY, NORTHERN INDIA

Aquatic resources are being polluted in many parts of the world. Heavy metal ions are potentially dangerous pollutants because of their acute toxicity, carcinogenicity and non-biodegradability. The aim of this study is to assess the heavy metal (Pb, Cu, Co, Cd, Cr, Zn, Ni, V, Be, Se, As and Ag) concentrations and possible contamination of surface water bodies along the Manali-Leh Highway in northwestern India. Eight unfiltered water samples were collected from rivers, streams and lakes from relatively urban and pristine areas along 170 km of the Highway. Samples were collected in plastic bottles that were pre-cleaned and acidified with H₂SO₄ to kill microbes and stabilize the metals in the collected samples. In the laboratory, the pH of the samples was reduced to < 2 using 90-95% concentrated H₂SO_4. Metal concentrations in the samples were measured by ICP-OES. With the exception of one sample, waters did not have high concentrations of metals by EPA standards. The sample with the high metal content appears to be a significant outlier and we have excluded this sample from further analysis. In the remaining samples, Be, Se, Cd and Ag were below detection limit, and the concentrations of Cr, Co, Ni, Cu, Zn and V were very low. These low concentrations may be considered to be background values, derived from geological processes. In two of these samples, the level of As was below that recommended by EPA for drinking purposes (10 ppb) but was considerable nonetheless (4.57 and 6.13 ppb respectively). The source of this As is unknown and needs further investigation. In urban areas, Pb is a metal of great concern. However, the concentration of Pb was either below detection limit or very low (0.42-4.07 ppb) in these samples; the EPA recommended threshold for drinking water being 15 ppb. This suggests that lead contamination due to vehicular pollution is minimal along the highway. Overall, this pilot study suggests the surface water bodies along the Manali-Leh Highway appear to be unpolluted by anthropogenic heavy metals.