长江口崇明岛土地利用方式对滨海土壤中重金属和砷的分布和形态特征的影响

The reclamation of tidal flats has been one of the important approaches to replenish the arable lands in the coastal areas; pollution status of reclaimed soils has received wide attention recently, especially for the study of heavy metals due to the relative high pollutant concentrations in wetlands. To understand the impact of land use change on heavy metal and arsenic(As) geochemistry by the reclamation of wetlands for agriculture, surface soils and soil profiles were collected from the agricultural land reclaimed in the 1990 s and the intertidal flat wetland at Dongtan on Chongming Island in the Yangtze River Estuary, China. The soil samples were analyzed for total concentrations and chemical speciation of chromium(Cr), zinc(Zn), copper(Cu), lead(Pb), nickel(Ni), cadmium(Cd) and As using inductively coupled plasma mass spectrometry(ICP-MS). Results showed that soil properties(salinity, total organic carbon and grain-size distribution) and the concentrations of heavy metals and As in the soils differed under the different land use types. The conversion of wetland to forest had caused obvious losses of all the measured heavy metals. In paddy field and dryland with frequent cultivation, the concentrations of Cr, Zn, Cu, Ni and As were higher when compared to forest land which was disturbed rarely by human activities. Speciation analysis showed that Cr, Zn, Cu, Ni and As were predominated by the immobile residual fraction, while Pb and Cd showed relatively higher mobility. In general, metal(except Ni) and As mobility decreased in the following order: wetland dryland ≥ paddy field forest land, which suggested that the reclaimed soils had lower metal and As mobility than the intertidal flat wetland. The results of this study contribute to a better understanding of the effects of land use on heavy metals and As in the reclaimed soils of the study area and other similar coastal areas.

Land use effects on the distribution and speciation of heavy metals and arsenic in coastal soils on Chongming Island in the Yangtze River Estuary, China