Mercury and Selected Trace Elements from a Remote (Gosainkunda) and an Urban (Phewa) Lake Waters of Nepal

摘要

Two lakes, one from the remote high altitude on the southern slope of the Himalaya (Lake Gosainkunda) and another from the urban mid-hill area (Lake Phewa) were studied for evaluating anthropogenic inputs of the pollutants, particularly mercury (Hg) and other trace elements (TEs) (such as Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb). A total of 77 water samples, 24 from Lake Gosainkunda and 53 from Lake Phewa were collected from different depth profiles during October/November 2010. Concentrations of Hg were significantly higher in Lake Gosainkunda compared to Lake Phewa probably due to long-range transport of Hg and its deposition on high altitudes of the Himalayas, in addition to the probable natural geological sources. Some of the TEs (such as Al, V, Cr, Mn, Fe, and Co) show crustal origin in Lake Gosainkunda, whereas others such as Ni, Cu, Zn, Cd, and Pb indicate possible anthropogenic origin (enrichment factor (EF)＞4). On the other hand, Al, V, Cr, Ni, and Cu show crustal origin in Lake Phewa and the remaining TEs (Mn, Fe, Co, Zn, Cd, and Pb) showed high EF values relative to the crustal elements suggesting potential anthropogenic inputs of the pollutants. The study further indicates that two studied lakes have different potential sources for Mn, Fe, Co, Ni, and Cu regarding TE pollution. A high enrichment of Cd and Pb in high-altitude lake (with less anthropogenic activities) compared to the low-altitude lake (with high anthropogenic activities) indicates atmospheric long-range transportation of the pollutants in remote areas of the Himalayas which might be possible as air masses pass through the industrial areas and deposit in the high altitudes.