Prediction and risk assessment of five heavy metals in maize and peanut: A case study of Guangxi, China.

To assess the contamination levels and health risk of cadmium (Cd), copper (Cu), mercury (Hg), lead (Pb), and zinc (Zn) to human beings, the concentrations of these heavy metals in soil were surveyed and the concentrations in maize and peanut grains were estimated by models. The geo-accumulation index (I geo) was calculated, and chronic daily intake (CDI), hazard quotient (HQ) and hazard index (HI) were estimated. Results indicated that the concentrations of Cd, Cu, Hg, Pb, and Zn in the soil samples exceeded the limit set by authorities in China. However, the concentrations in maize and peanut grains were rarely higher than the allowable concentrations suggested by the Ministry of Health of China (MHC). In accordance with geo-accumulation, these heavy metals in soil samples were polluted to different extents. Prediction models were developed to effectively assess the health risk of using TOC, Mn, pH, and CaO to human beings. Therefore, the concentrations of these heavy metals in the grains could be decreased by changing their levels in soil. The CDI, HQ, and HI were estimated by estimating concentrations of Cd, Cu, Pb, and Zn in maize grains, indicating that these metals exhibited a slight health risk to adult residents.

Application of ecogeochemical prediction model to safely exploit seleniferous soil.

Seleniferous soil and crops have recently attracted attention worldwide. Cultivating seleniferous crops in the absence of heavy metals is greatly challenging. This study aimed to develop approaches for the safe exploitation of seleniferous soil. We collected 246 pairs of rice grain samples and their corresponding rhizosphere soil samples and 8542 topsoil samples from Binyang and Xingbin in Guangxi. The Cd, Cu, Hg, Pb, Zn, and Se contents of soil and rice grain samples were tested. Several soil properties, including CaO, Mn, Mo, and S contents; total organic carbon content; and pH were also measured. Soil and rice grain samples that were classified as seleniferous accounted for 85.77% and 88% of all samples, respectively. More than 30% of soil and rice grain samples were potentially polluted by Cd. The percentage of seleniferous rice grain samples increased as soil Se concentration increased. Notably, however, the percentage of Cd-polluted rice grain samples decreased with the increase in soil Cd concentration. Models for the prediction of BAFs of heavy metal and Se were accurately established on the basis of significant partial correlations between log10 (BAFs) and log10 (soil properties). Farmlands with seleniferous soil under preferential protection and with safely exploited seleniferous soil accounted for 82.61% of the total study area. Sites that require remediation or land-use changes accounted for only 14.7% of the total study area and were mainly distributed in the center of the study area.