The Spatial Distribution Characteristics of Heavy Metals in River Sediments and Suspended Matter in Small Tributaries of the Abandoned Wanshan Mercury Mines, Guizhou Province

Abstract

BACKGROUND Although abandoned mines are no longer exploited, waste mines, old smelting sites and buried tailings can still pollute downstream areas through rainwater leaching and surface runoff. The study on the distribution and relationship of heavy metals in sediments and suspended particulate matter (SPM) along rivers in abandoned mines has important significance. OBJECTIVES To preliminarily investigate heavy metals in river sediments and SPM in Wanshan Mercury Mines, and provide basic information for monitoring and remediation of contaminated cultivated land. METHODS The contents of Cr, Ni, Cu, Cd, Pb, As, Hg, Zn and Co in sediments and SPM samples were determined by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) and Atomic Fluorescence Spectrometry (AFS) with wet digestion pretreatment. The pollution status and spatial distribution characteristics were identified in order to obtain information of pollutant migration and diffusion downstream. RESULTS The total mercury content (Hg) in sediments ranged from 0.10 to 16.0μg/g (dry weight), averaging 5.79μg/g, which was ten times higher than the Hg limit of the Class Ⅱ soil environmental quality standard of China. The average contents of Ni, Cu and Co were not higher than the standard. The variation coefficients of Hg and Cd were large, indicating the heterogeneously spatial distribution of Hg and Cd. Mercury in sediments reached a high potential ecological risk level. CONCLUSIONS The Hg in sediments and SPM in the study area are related to the hydrodynamic conditions, and the maximum values occurred at the sites with broad river channel and low flow rate. As the mining and smelting of Wanshan Mercury Mine has been stopped for a long time, the weathering and leaching of the abandoned mining area under natural conditions will cause Hg and Cd pollution in the lower reaches of the river.

Keywords

• small tributary
• sediment
• suspended matter
• heavy metals
• wanshan mercury mines