Using pXRF to assess the accumulation, sources, and potential ecological risk of potentially toxic elements in soil under two greenhouse vegetable production systems in North China

Intensive greenhouse vegetable production (GVP) has increased the pollution risk of potentially toxic elements (PTEs) in soils. This study examined the accumulation, sources, and potential ecological risk of six PTEs (Cu, Zn, As, Ni, Pb, and Cr) in soil under two GVP (solar greenhouse (SG) and round-arched plastic greenhouse (RAPG)) systems by portable X-ray fluorescence spectroscopy (pXRF) and conventional laboratory analysis. The results indicated that all PTE concentrations were lower than their corresponding thresholds in GVP soils, presenting a low potential ecological risk in both GVP soils according to risk indices (RI <= 40.67). As, Ni, Pb, and Cr were not significantly accumulated in both GVP soils. Although Cu and Zn accumulated in both GVP soils, their accumulation extents in SG soil were both greater than that in RAPG soil. Cu and Zn were mainly originated from anthropogenic activities based on multivariate statistical analysis, which were greatly associated with excessive manure application. Overall, pXRF can identify the accumulation difference of PTEs between the two GVP soils, which is generally consistent with conventional laboratory analysis. Hence, pXRF can be a promising alternative to conventional laboratory analysis for rapid assessment of PTEs accumulation, sources, and the potential ecological risk in the two GVP soils. Although PTEs had a low ecological risk, Cu and Zn accumulation in SG soil was increased with the planting years. Therefore, rational application of livestock manure containing high levels of Cu and Zn should inspire strategies to mitigate the environmental risk in GVP soils, especially in SG soil.