Occurrence, Origin and Risk Assessment of Trace Elements in High Geological Background Impacted Soil-crop Systems in Yunnan, China

Excessive accumulation of trace elements (TEs) in farmland soil-crop systems is a severe threat to food safety impeding the sustainable development of the ecological environment. This study examined the concentration, pollution status, sources, and potential risk of five TEs (As, Cu, Zn, Cd and Cr) in the soil-crop systems of the high geological background area of Lijiang, Yunnan, China. The average TE concentrations (mg·kg−1) in the farmland soils were as follows: Cr (185.3) > Zn (148.1) >Cu (92.4) >As (20.9) >Cd (0.4), exceeding the Chinese limit standards (GB15618-2017) by 29.1, 20.0, 38.2, 16.4, and 60.0%, respectively. The factor matrix analysis (PCA) and source identification study indicated that Cd, Cu, and Cr were the most prominent TEs mainly derived from the soil-forming parent material. However, compared with China's food contaminants limit standard (GB 2762–2017), only Cr exceeded the food safety limit in all edible crops, especially in the leafy vegetable and rhizome crops, except the cereals. In addition, we established a univariate significant correlation model (R2 = 0.53854, P < .01) between soil Cr content and leafy vegetable Cr accumulation, and a trivariate significant correlation model (R2 = 0.528, P < .01) of leafy crop Cr accumulation with soil Cr content, SOM, and pH. These data revealed that the soil TEs cumulative contamination in the high geological background area is a lighter risk to edible crops, and the accumulation of TEs in crops (especially leafy vegetables) is mainly from the soil TEs. Meanwhile, pH and SOM are the key factors that affect the bioavailability state of the soil TEs. Therefore, artificial adjustment of soil physicochemical properties could be a potential strategy for the safe utilization of TEs contaminated farmland soil under high geological background.