Advances in Resources and Environmental Science

The wastes discharge from rapidly developing heavy metal-related enterprises resulted in serious soil heavy metal pollution, threatening agricultural production, biodiversity and human health. The response of complex and diverse soil ecosystem to the toxic effects of heavy metal pollution varied variously, which makes it extremely difficult to determine the risk threshold for soil ecological risk assessment, leading to difficulties in effectively implementing soil ecological risk assessment. This paper explored simple and effective methods for ecological risk assessment based on the different reference values. This paper reviewed domestic and foreign literature on soil heavy metal ecotoxicology, 5% hazardous concentration (HC5) and 10% inhibitory effect concentration (EC10) of heavy metals on barley were collected；and 20 soils with different pollution levels around 20 heavy metal-related enterprises in Guangdong were collected. The risk quotient of 20 sampled soils were calculated based on the different risk thresholds respectively including risk screening value of paddy field and non-paddy field in GB15618-2018, HC5 and EC10 values of barley above. At the same time, the potential ecological risk index of 20 sampled soils were calculated with background value and risk screening value in GB15618-2018 respectively. The main results are as follows: The soil ecotoxicological results of some heavy metals and As were reviewed and explored in soil ecological evaluation. The four risk quotients and the two potential ecological risk values of 20 samples showed significant correlation. Using HC5 of heavy metals and EC10 of barley as reference thresholds to calculate their risk quotient and background value and risk screening value as reference ratios to calculate potential risk index, the proportion of extremely high risk in 20 samples was 40%, 35%, 75% and 45%, respectively. In the case of widespread pollution, the potential ecological risk index value calculated by using background value as a reference is high, which greatly increases the scope and cost of ecological risk control of heavy metal pollution. In the case that HC5 of pollutants is difficult to obtain, the soil risk quotient is calculated by using barley EC10 as the reference ratio and multiplied by 4 times. The soil risk quotient of single element is defined as slight risk, medium risk, strong risk and extremely strong risk according to <1, 1-2, 2-4 and >4 respectively, which can be used for relatively more refined ecological risk assessment. This study shows that barley EC10 can be used as a risk threshold for preliminary soil ecological risk assessment and the basis to screen soil priority control pollutants for heavy metal-related enterprises.

Soil ecotoxicology; Heavy metals; Risk threshold; Ecological risk assessment