Characteristics And Risk Assessment Of Heavy Metal Pollution Of Soil And Crops In Agricultural Land Around Three Kinds Of Solid Waste Dumps

Chongqing is an old industrial city in the southwest of China,and industrial production and mineral development have had an important impact on the ecological environment.In recent years,the problem of soil heavy metal pollution caused by the past rough economic development model and industrial "three wastes" emissions has been improved,but the historical legacy of heavy metal pollution and environment risks still exist.In addition,industrial production,mining and smelting processes produce a large amount of solid waste,which is not treated and utilized in time,and the long-term accumulation will have a great impact on the surrounding arable soil and crops,and further threaten human health through the food chain.Based on this,this study was conducted to investigate the content and enrichment characteristics of eight heavy metals in soil and crops(rice and maize)around three types of solid waste dumps(iron ore slag dumps,red mud dumps and ash dumps)in Chongqing,to evaluate their environmental and health risks,and to identify the environmental and health risks of different solid waste dumps using multivariate statistical methods and absolute factor/multiple linear regression models(APCS-MLR)to identify the pollution sources and contribution rates of heavy metals in soils around different types of solid waste dumps,in order to provide a scientific basis for the prevention and control of heavy metal pollution in arable soils around different types of solid waste dumps and the safety of agricultural products.The main research results are as follows:(1)All three types of soil heavy metals in arable land around solid waste dumps are accumulated,and most of the average values of heavy metals exceed the background values of soils in Chongqing.Some of the soil heavy metals exceeded the risk screening value of the Soil Environment Risk Control Standard for Agricultural Land Pollution(GB 15618-2018),among which 20.6% of soil Cd and 2.94% of soil Hg,Cu and Ni in iron ore slag dumps exceeded the risk screening value;21.7% of soil Cd in red mud dumps exceeded the risk screening value;42.86% and 17.10% of soil Cd in ash dumps exceeded the risk screening value,respectively.The risk screening value and risk control value of soil Cd in ash dumps were exceeded by 42.86% and 17.10%respectively.(2)The evaluation results of the cumulative ground contamination index method showed that the arable soils around the three solid waste dumps were mainly contaminated by Cd and Hg.The evaluation results of the ecological risk index method show that the iron ore slag dumps belong to medium pollution level,with 50%,11.8%and 6% of the points reaching moderate,strong and very strong pollution levels,respectively;the red mud dumps belong to medium pollution level,with 91.3% of the points reaching moderate pollution level;the ash dumps belong to very strong pollution level,with 40%,11.4% and 17.1% of the points reaching moderate,strong and very strong pollution levels.(3)The enrichment ability of crops around the three solid waste dumps has some differences,with the enrichment ability of crops around the iron ore slag dumps being stronger for Zn,Cd and Cu,the enrichment ability of crops around the red mud dumps being stronger for Zn,Ni and Cu,and the enrichment ability of crops around the ash dumps being stronger for Zn,Cd,Ni and Hg.There are non-carcinogenic and carcinogenic risks to the population from consuming crops in the 3 study areas.non-carcinogenic risks to humans from rice As around the 3 dumps;Cd is the main carcinogenic risk factor for crops around iron ore slag dumps;As and Cr are the main carcinogenic risk factors for crops around red mud dumps;Cd and As are the main carcinogenic risk factors for crops around ash dumps.