[Technological Classification of Cadmium Quality in the Rice Producing Areas of South China]

Classifying the quality of agricultural products is an important means of managing the arable land quality and guaranteeing the quality and safety of agricultural products. This work is planned to be completed in 2020. However, there is still no perfect method or technology for classifying the quality of arable lands. The species sensitivity distribution (SSD) has become commonly used for determining ecological safety thresholds since it takes into account differences in species sensitivity, the physical and chemical properties of soils, biological availability, and sources of pollutants. However, it has not yet been applied to the classification of arable land quality. Therefore, based on the routine monitoring data of rice production areas in southern China from the Agro-environmental Monitoring Center of China, this study proposes the use of species sensitivity distributions to classify the environmental quality of cadmium in rice production areas. The scientific rationale of this method was also discussed in order to provide an important reference for the construction and improvement of the classification system for arable land quality in China. The results showed that the pH, soil organic matter, and cation exchange capacity of the physical and chemical properties of soils significantly affected the enrichment of cadmium in rice, and this relationship was used to establish the cadmium transfer equation in the soil-rice system. It was found that there were obvious differences in the cadmium enrichment abilities of different rice varieties, which were mainly caused by the differences in their genotypes. According to the species sensitivity distributions, soil cadmium thresholds were obtained, which yielded a priority protection class of less than 0.26 mg·kg^-1 and strict control class of greater than 1.67 mg·kg^-1, between which are the safe use classes. The results were verified through independent datasets, and it was found that the application of species sensitivity distributions to classify the environmental quality of cadmium in rice producing areas reflected good scientific rationale and operability. This study may provide a foundation for the construction and improvement of the arable land quality classification system in China.