Two-century sedimentary record of heavy metal pollution from Lake Sayram: A deep mountain lake in central Tianshan, China

A short sediment core from Lake Sayram, China, was used to develop a high-resolution record of heavy metal inputs from the Tianshan Mountains and the surrounding region over the last 200 years. We investigated metal inputs to Lake Sayram using the geo-accumulation index (Igeos) and enrichment factors (EFs). Anthropogenic metal fluxes were calculated to quantify the human contribution to heavy metal pollution. Lake Sayram has been polluted by Cd, As, Pb, and Hg since the 1960s, and has had three distinct periods in its pollution history. Prior to 1960, metals in Lake Sayram sediments were mainly from natural sources, with very low values of EFs and Igeos. From the 1960s to 1990s, heavy metal delivery to sediments increased slowly, associated with relatively weak economic development in Xinjiang Province, similar to other areas of China. Thereafter, contamination by heavy metals increased markedly, especially after the 2000s. Lake Sayram was considered to be moderately polluted by Cd, Hg, and Pb, and is moderately to strongly polluted by As at present. Contamination by heavy metals varied with economic development of Xinjiang Province. Between 1990 and 2010, anthropogenic accumulation of Cd, As, Pb and Hg increased from 4.05 to 7.30 ng/cm2/y, 0.27–0.98 μg/cm2/y, 0.21–0.39 μg/cm2/y and 0.61–0.83 ng/cm2/y, respectively. Furthermore, the 206Pb/207Pb ratio demonstrates that coal burning emissions and Pb in vehicle gasoline were major sources of heavy metal pollution in the Tianshan Mountains region.