Abstract: This paper analyzed the mercury (Hg) content in the soils of Doyeuxia augustifolia marsh, corn field, and lowland rice field and in the plants of D. augustifolia, Carex meyeriana, C. lasiocarpa, poplar, and moss in Sanjiang Plain, aimed to approach the sources and distribution characteristics of soil and plant Hg in the Plain as well as the effects of land use change on the soil Hg content. The total Hg content in the soils was in the range of 0.006-0.208 mg·kg^-1, with an average of 0.053 mg·kg^-1, which was higher than the background value of the soils in Heilongjiang Province. From the top layer to the bottom, the Hg content in the soils changed little in D. augustifolia marsh, but varied greatly in corn field and lowland rice field. The Hg content in the plants was in the order of moss > C. meyeriana > D. augustifolia > C. lasiocarpa> poplar, among which, the Hg content in moss was up to 0.132 mg·kg^-1. Correlation analysis suggested there was a significant positive relationship between soil Hg and dissolved organic carbon (r=0.269, P<0.05). Atmospheric dry and wet deposition and the plant uptake of atmospheric Hg could be the main Hg sources for the marsh. After the marshland was reclaimed into cropland, the soil Hg content was decreased by 45.6%, but after the upland field was changed into lowland field, the soil Hg content was increased by 18.3%.

Key words: Soil pollution, Heavy metal, Extractable form, Cultivated soil