[Cadmium Content Characteristics, Health Risk Assessment, and Soil Environmental Benchmarks in Farmland Soil and Agricultural Products in Ningxia].

Abstract

A precise assessment of the health risks posed by cadmium （Cd） contamination in agricultural products from regional farmland is crucial for informed pollution prevention and control decisions. This study collected 740 pairs of soil and agricultural product samples from farmland in Ningxia, focusing on Cd content detection. The evaluation encompassed Cd pollution characteristics in soil and agricultural products and assessed the associated health risk for human ingestion. Additionally, farmland soil environmental benchmark values specific to the study area were established. The results showed that soil pH levels across the study area were consistently alkaline, with values exceeding 7.3. Cd content in the soil fell within a range of 0.020 to 0.472 mg·kg^-1, lower than the pollution risk control value of agricultural soil （pH > 7.5） in China （GB 2762-2017）. Average Cd content in grains and vegetables was relatively high, with values of 0.013 and 0.011 mg·kg^-1, respectively. Conversely, potatoes and fruits exhibited the lowest average Cd content at 0.002 mg·kg^-1 each. The biological accumulation coefficient of Cd in different agricultural products was less than 1, indicating no accumulation effect across all agricultural products. The single non-carcinogenic risk index （HQ） of the soil pathway to the human body was lower than 1, and the single carcinogenic risk index also had no carcinogenic risk （CR < 10^-4）, but the non-carcinogenic and carcinogenic risk indices of Cd intake via soil pathways remained below significant thresholds, yet they were higher in children compared to adults. The intake of Cd through agricultural products posed no discernible health risks to either adults or children. The critical soil Cd thresholds for corn, wheat, fruit, and other grain fields derived from the species sensitivity distribution （SSD） method were 0.503, 0.336, 0.234, and 0.342 mg·kg^-1, respectively, which were lower than the risk screening values of soil environmental quality standards （GB 15618-2018） in China. Therefore, the Cd thresholds for corn, wheat, fruit, and other grain fields derived from this study were stricter than the standards. The critical values for soil Cd in rice and vegetable fields were 1.057 and 0.740 mg·kg^-1, respectively, which were higher than the corresponding risk screening values in the standard. Specifically, critical values for rice and vegetable fields were found to be higher, suggesting a relaxed threshold compared to the standard. Conversely, critical values for soil Cd in potato fields aligned closely with the existing standard. This study underscores the importance of tailoring soil environmental benchmarks to specific agricultural products, advocating for adjustments based on actual content of heavy metals in different agricultural products.