The Soil Heavy Metal Information Accurate Collection and Evaluation about Lycium Barbarum Cultivation in Western China

Abstract

We selected two small sections of Lycium Barbarum cropland at Nuomuhong Farm in the Qaidam basin, western China: one had been farmed for only one year (original land), and the other had been farmed for many years (farm land). We tested surface soil samples for their content and distribution of six heavy metals (Cd, Zn, Pb, Cu, As, and Cr). All six heavy metals appeared at medium levels in samples from both sections of cropland. We conducted an interpolation analysis and drew a spatial distribution map based on the inverse distance weight (IDW) method. The distribution graph revealed a relatively consistent distribution of the six heavy metals in soil samples, a different gradation in the original land, and areas of higher values in the farm land. These findings suggest that the soil had been polluted. According to the Pollution-Free Food Standard and the Green Food Standard, we calculated the integrate pollution index using the Nemerow index method to check whether the levels met Pollution-Free food Standard and Green Food Standards. The values were 0.5 and 0.7 (defined as ‘clean’) in samples from the original land, but were 0.6 and 0.9 in samples from the farm land, which may be considered excessive.