Trace metals in the soils of the Sanjiang Plain in the Northeast Asia: Land use influence

Abstract

The Sanjiang Plain is located in the Northeast Asia, where the large areas of farmland and wetland are distributed. The soil cores of 40 to 100 cm depth were collected at 48 sites in the Sanjiang Plain and sectioned into 3-, 5- or 10-cm slices. In total, 451 soil samples were got and were analyzed for trace, minor, and major elements. The concentration ranges of trace and minor metals (mg kg-1) in the soil were 1.08-65.7 for As, 0.03-0.36 for Cd, 5.26-103.8 for Co, 42.6-102.9 for Cr, 12.4-64.4 for Cu, 0.01 to 0.14 for Hg, 139.3-4184.5 for Mn, 13.4 to 58.2 for Ni, 15.3-106.2 for Pb, 0.25-1.67 for Sb, 7.87-23.6 for Sc, 2525-6265 for Ti, 51.7-283.4 for V, and 42.8-184.6 for Zn. The average contents of Al2O3, Fe2O3, MgO, CaO, Na2O, and K2O in the soil were 9.72%, 5.34%, 1.00%, 0.98%, 1.63, and 2.28%, respectively. The soil pH ranged from 5.03 to 6.97, with an average of 5.84. Land uses had important effects on trace metal concentrations in the soil. The average concentrations of As, Co, Mn, and Pb the soil decreased from forest land, to dry farmland, to paddy field, and to wetland. On the other hand, the average concentrations of Cr, Cu, Ni, Sc, and Ti in the soil of wetland and paddy field were higher than those of dry farmland and forest land. However, the average concentrations of Hg and V in the soil of wetland and forest land were higher than those of paddy field and dry farmland. The difference in the concentrations of trace and minor elements among the four types of land use originate from anthropogenic activity, hydrologic conditions, and pristine soil properties. Atmospheric deposition of V and Hg led to higher Hg and V concentrations in the soil of natural wetland and forest land than in the agricultural land (paddy field and dry farmland). Higher leaching of redox sensitive elements such as As, Co, Mn, and Pb led to lower concentrations of As, Co, Mn, and Pb in wetland and paddy field than in forest land and dry farmland. The difference in the concentrations of Cr, Cu, Ni, Sc, and Ti in the soil among the four kinds of land use should be ascribed to the difference in the pristine soil properties.   This study was funded by the National Natural Science Foundation of China (42276233).