[Zoning and Safe Utilization Method of Heavy Metal Contaminated Cultivated Land at Block Scale].

The safe use of arable land is one of the important measures to ensure food security and to realize the construction of ecological civilization. In order to solve the problem of blindly selecting technical measures in the process of safe use and restoration of pollution-risk cultivated land, 244 surface soil samples and 100 sets of rice-root soil samples were collected in Echi Town, Qianjiang District, Chongqing. Based on the contents of five heavy metals of Cd, Hg, Pb, As, and Cr, as well as soil oxides, organic matter, and pH and other indicators, a prediction model was established using multiple regression and geostatistical analyses, and the plots were assigned values, combined with the soil and soil in the plots.

[Spatial Distribution Characteristics, Pollution, and Ecological Risk Assessment of Soil Heavy Metals Around Mercury Mining Areas].

To ascertain the impact of mercury mining on the surrounding soil environment and human health, 42 surface soil composite samples were collected around a mercury mining area in Youyang County, Chongqing, and the heavy metals (Cd, Hg, Pb, As, Cr, Cu, Zn, and Ni) contents and pH of the soil, the spatial distribution of heavy metals, pollution degree, and ecological risk were studied. The results show that the surface soil layer in the study area is significantly enriched in heavy metals. According to the soil environmental quality risk control standard for soil contamination of agricultural land (GB15618-2018), soil Cd, Hg, Pb, As, and Zn showed different degrees of excess.

[Characteristics of Cadmium Enrichment and Pollution Evaluation of a Soil-Crop System in a Typical Karst Area].

In order to study the characteristics and factors influencing Cd accumulation in surface soils and crops in karst areas, and to provide a theoretical basis for safe land use, 360 surface soil samples, 7 deep soil samples, and 85 rice samples were collected from central Qianjiang District, Chongqing. The samples and 73 corn samples (corresponding to root-zone soil samples), were analysed to determine the content of Cd, TFe O, Mn, organic matter (C), Se, and pH. Based on geostatistical analyses, the spatial distribution and Cd enrichment of the surface soils were determined and a safety evaluation for the soil and crops was carried out.

[Distribution Characteristics of Selenium in a Soil-Crop System and the Threshold of Selenium-Rich Soils].

In order to determine the distribution characteristics of Se in soil-crop systems, we carried out a study on the Se-rich soil threshold by collecting 8789 surface soils and 155 deep soils in the Qianjiang District of Chongqing City, China, and 141 corn seeds and 159 rice seeds (simultaneously collecting 141 and 159 corresponding root soil samples, respectively). We then analyzed the Se content, organic matter, S, Mn, TFeO, AlO, and KO in soils and crops, and soil pH. We also analyzed the surface layer using geostatistical methods and the distribution characteristics of Se in deep soils using multiple regression analysis to study the factors influencing the bioavailability of Se.