Mercury contaminations from historic mining to water, soil and vegetation in Lanmuchang, Guizhou, southwestern China

Concentrations of total mercury and methylmercury (MeHg) were measured in soil and vegetation samples collected from a small area with a long history of Hg-mining. Hg distributions were determined in stream-waters during two sampling periods. Total Hg concentrations in soil and vegetation samples were highly elevated ranging from 0.41 to 610 mg kg(-1) and from 0.02 to 55 mg kg(-1), respectively. MeHg concentrations varied from 0.41 to 8.8 microg kg(-1) in soil samples and from 0.65 to 5.5 microg kg(-1) in vegetations. The concentrations of total Hg in stream waters varied from 55.0 to 7020 ng L(-1) in the flood-flow regime and from 24.8 to 679 ng L(-1) in the base-flow regime, respectively. Average dissolved Hg concentration was 15.7 ng L(-1) in the wet season and 21.0 ng L(-1) in the dry season. However, particulate Hg was typically >70% of total Hg in the flood-flow regime. Higher concentrations of particulate Hg primarily originated from summer floods were the major pathway of Hg transportation, which were evidenced by the positive correlation between particulate Hg and total suspended solids (TSS). The contaminated soils and distribution patterns of Hg in the stream-waters may serve as an important source of Hg to the local environment in the study area.