Relatively stable metal(loid) levels in surface soils of a semiarid Inner Mongolia steppe under multiple environmental change factors

Global change is increasingly recognized as a possible regulator of metal(loid) biogeochemistry, but it is not well known whether and to what extent multiple environmental change factors alter the metal(loid) levels in surface soils. Here, we analyzed the total concentrations of surface soil metal(loid)s (Ca, Mn, Cr, V, Pb, Ni, Cu, Co, As, and Cd) with 3 years of simulated warming, increased precipitation, nitrogen addition, and elevated CO2, and with 9 years of simulated warming and increased precipitation, both in the Inner Mongolia steppe (northern China). Three relatively mobile fractions of the metal(loids), i.e., exchangeable, carbonate, and organic-bound fractions, were also quantified. Results showed that multiple environmental change factors had antagonistic interactions on only a few number of total or fractional metal(loid) concentrations. The antagonistic interactions between nitrogen addition and elevated CO2 on some metal(loid) concentrations suggest that the significant simple effects of N addition without elevated CO2 treatment reported here or previously may not happen with a future, higher CO2 level. The main effects of all 3- or 9-years of treatments on total or fractional metal(loid) concentrations in surface soils were all no more than 25%. These findings indicate that global environmental change has a relatively weak impact on surface soil metal(loid) pools and the associated ecological risks in the Inner Mongolia steppe at a near-decadal scale.