Decadal growth of atmospheric heavy metal pollution in Central India: evidence from sediment geochemistry of Upper Lake Bhopal

Sedimentary archives provide long-term records of heavy metal pollution crucial for making an efficient pollution control policy to protect humans and our ecosystem. In this study, we present V, Cr, Ni, Cu, Co, Sn, Zn, Cd, and Pb concentrations measured in a 38 cm long sediment core from the Upper Lake (wetland protected under Ramsar convention 2002) in Bhopal to provide the last century records of heavy metal pollution in Central India. Few riverine sediments and free-fall atmospheric dust samples collected from the lake periphery were also analyzed. Principal component analysis and heavy metal abundance patterns in the lake sediments and the likely endmembers suggest atmospheric deposition as the major cause of heavy metal influx into the lake. The geochemical background upper limits of heavy metals as determined using modal analysis were used to calculate the metal-specific enrichment factor (EF) and the overall heavy metal pollution load index (PLI). The overall metal pollution has remained insignificant (PLI similar to 1) throughout the core history, while minor pollution of Zn, Cd, and Pb (EF > 1-2) emerged in the early-1980s. This study highlights that the emergence of Zn, Cd, and Pb pollution in Central India is contemporaneous to that seen in multiple lacustrine sediment records from China but it does not yet show any modern phasing-out trend as seen in China and elsewhere.