Characteristics and Risk Assessment of Soil Heavy Metal Contents in Facility Agriculture of Guangxi

[Objectives] To study the characteristics of soil heavy metal contents in facility agriculture of Guangxi and analyze its risks. [Methods] The heavy metal content of 30 surface soil samples taken from facility agriculture in Guangxi was analyzed. The status of soil heavy metal pollution in facility agriculture of Guangxi was evaluated by the single factor index method, geo-accumulation index method and Hakanson potential ecological risk index method with reference to the soil background value in Guangxi. [Results] Compared with the soil background value in Guangxi, the over-limit rates of heavy metals cadmium, lead, arsenic, chromium, mercury, copper and zinc in soil samples were 56.67%, 56.67%, 16.67%, 30.00%, 50.00%, 60.00% and 80.00%, respectively. Compared with the screening values of the Soil Environmental Quality - Risk Control Standard for Soil Contamination of Agricultural Land (for trial implementation) (GB15618-2018), the over-limit rats of the heavy metals cadmium, arsenic, copper and zinc in the surface soil of agricultural facilities in Guangxi were 56.67%, 10.00%, 16.67% and 23.33%, respectively. Except for the average content of soil cadmium exceeding the screening value, the evaluation content of the other six soil heavy metals did not exceed the screening value. According to the evaluation results of the single factor pollution index method, the surface soil arsenic and chromium of the agricultural facilities in Guangxi belonged to the clean level, lead, mercury, and copper belonged to mild pollution, and cadmium and zinc belonged to moderate pollution. According to the evaluation results of the land accumulation index, the lead, arsenic, chromium and mercury in the surface soil of the agricultural facilities in Guangxi belonged to the pollution-free level, while the cadmium, copper and zinc belonged to the mild-moderate pollution. According to the evaluation results of the potential ecological risk index method, the potential ecological risks of the heavy metals of lead, arsenic, chromium, copper and zinc in the soil of agricultural facilities in Guangxi belonged to low potential ecological risk level, and the potential ecological risks of cadmium and mercury belonged to moderate risk level. The potential ecological risk index (RI) of the seven heavy metals in the soil was 132.46, which belonged to moderate potential ecological risk. The largest contribution of soil heavy metals to the potential ecological risk index was cadmium and mercu