Heavy Metal Bioaccumulation in Rice from a High Geological Background Area in Guizhou Province, China

Long-term exposure to high levels of heavy metals can lead to a variety of diseases. In recent years, researchers have paid more attention to mining and smelting areas, industrial areas, and so forth, but they have neglected to report on high geological background areas where heavy metal levels are higher than China’s soil environmental quality standard (GB 15618-2018). In our study, an investigation of heavy metals in paddy soil and rice in the high background area of Guizhou Province was carried out, and the factors affecting the absorption and utilization of heavy metals in rice were discussed. A total of 52 paddy soil and rice samples throughout the high geological background of Guizhou, China, were collected, and concentration(s) of arsenic, cadmium, copper, lead, and zinc were analyzed. The arithmetic mean values of paddy soil heavy metals were 19.7 ± 17.1, 0.577 ± 0.690, 40.5 ± 32.8, 35.5 ± 32.0, and 135 ± 128 mg kg−1 for arsenic, cadmium, copper, lead, and zinc, respectively. Most of the heavy metals’ contents in the soil were above the soil standard value. The highest content of cadmium was 15.5 times that of the soil standard value. The concentration(s) of arsenic, cadmium, copper, lead, and zinc in rice were 0.09 ± 0.03, 0.01 ± 0.01, 1.57 ± 0.69, 0.002 ± 0.003, and 11.56 ± 2.61 mg kg−1, respectively, which are all lower than those specified by Chinese food safety standards (GB 2762-2017). The results and discussion show that the bioavailability, pH, and soil organic matter are important factors that affect the absorption of heavy metals by rice. According to the consumption of rice in Guizhou Province, the risk of eating rice was considered. The results revealed that the hazard quotient is ranked in the order of copper > zinc > cadmium > arsenic > lead, and there is little risk of eating rice in the high geological background area of Guizhou Province. These findings provide impetus for the revision and improvement of this Chinese soil environmental quality standard