Response of toxic metal distributions and sources to anthropogenic activities and pedogenic processes in the Albic Luvisol profile of northeastern China

Abstract

Intensive agricultural activities generally influence the distribution and sources of toxic metals in the soil profile. This study aimed to investigate the distribution characteristics and mechanisms of toxic metals and mineral matrix elements in the Albic Luvisol of the Sanjiang Plain and assess their anthropogenic effects. Soil cores (0–50 cm depth) were collected at 33 sites in the northeastern agricultural field of the Sanjiang Plain and then sliced into 10 cm slices. The soil pH, organic matter (SOM), and 17 elements were determined. The results showed that SOM content was higher in horizon A, whereas mineral matrix elements Al, Fe, and Mg contents were higher in horizon B. Ca and P contents gradually decreased with soil depth due to the influence of fertilizer. Three types of trace element concentration profiles were identified: (1) decrease with depth for Cd and Hg; (2) highest in horizon B for As, Co, and Pb; and (3) lowest in horizon E the middle layers for Cr, Cu, Ni, Sc, and V. The vertical changes in Cd and Hg concentrations were generally as a result of P fertilizer use and atmospheric deposition, respectively. In addition, Cd and Hg are preferentially associated with SOM. Vertical changes in As, Co, and Pb concentrations were mainly due to their sorption on Fe and Mn oxides, whereas vertical changes in Cr, Cu, Ni, Sc, and V concentrations were mainly derived from soil matrix minerals. The 26% of Cd and 14–16% of As, Co, Hg, and Pb in the 0–40 cm depth soil layer were from anthropogenic sources such as fertilizer use and atmospheric deposition, whereas Cr, Cu, Ni, and V in the soil generally originated from geogenic sources. Therefore, the long-term accumulation of Cd, As, Co, Hg, and Pb in agricultural soils may be a concern in the future and should be monitored regularly.