Baseline concentrations of trace metals in grassland topsoils from West Jilin province, Northeast China

摘要

The objective of this study was to determine the baseline concentrations of trace elements in grassland topsoils from 155 soil sampling sites in West Jilin province, Northeast China, to establish the relationships between the trace metal contents and soil physicochemical properties and major oxide contents and among trace metal concentrations themselves, and to identify the possible sources of trace element in soils. The baseline concentrations of trace elements(mg/kg) were: As 3.12-14.18, B 16.17-49.08, Cd 0.037-0.127, Co 0.96-15.28, Cr 18.87-60.83, Cu 10.81-24.75, Hg 0.004-0.035, Mn 171.25-657.87, Mo 0.08-1.15, Ni 6.79-30, Pb 12.58 -26.08, Se 0.03-0.36, and Zn 18.93-61.03. The upper baseline limits of these elements were all less than the Chinese Environmental Quality Standard for Soils, the Dutch Intervention Values for Soils, implying that trace element contents in the studied soils were of the safety levels.Fe_2O_3 and Al_2O_3 had stronger correlations with most trace elements than other oxides, and Co,Cr,Cu,Mn, Ni were highly correlated one another. Three types of geochemical associations were distinguished from this srudy:the first association involving As,Co,Cr,Cu,Mn,Mo,Ni,Pb,Zn,Al2O_3 and Fe_2O_3 was mainly associated with Al,Fe-Mn oxides and/or with the Al-bearing clay minerals, suggesting that the trace elements were mainly derived from lithogenic and pedogenic processes;;the second association including Se, Hg, Cd, CaO and organic carbon was mainly associated with organic matter and calcium oxides, showing that Se,Hg and Cd were mainly contributed by anthropogenic sources;;the third association containing B, Na_2O, K_2O, MgO, pH, and electrical conductivity was mainly associated salinization processes of soils, implying that alkaline pH and high Na contents would enhance B concentration of soils.