[Ecological Risk Assessment and Migration and Accumulation Characteristics of Heavy Metals in Farmland Soil-crop System from Typical Pyrite Mining Area].

To evaluate the ecological risk of heavy metals in the soil-crop system in the superimposed high background and human activities from pyrite mining, the heavy metal contents and chemical speciation in soil and crop samples were analyzed, and these data were used to assess the potential ecological risk and factors affecting the migration ability of heavy metals using bioconcentration factors(BCF), potential ecological risk index(RI), risk assessment code(RAC), and correlation analysis. The results indicate that the average Cd, Cu, Pb, and Zn concentrations exceeded the background values of soils in Zhejiang Province and China. Cd had the greatest potential ecological harm, followed by that of Hg. The bioactive components and potential bioactive components of Cd accounted for 46% and 33%, respectively, indicating relatively high bioavailability. Cu and Pb were mainly in potential bioactive components accounting for 60% and 73%, respectively. The As, Cr, Hg, Ni, and Zn were predominantly residual and accounted for >60%, which indicated low biological activity. The RAC levels were in the following order:Cd>Zn>Cu>Pb>Ni>As>Cr>Hg; soil Cd had the highest ecological risk, mainly with high and extremely high levels, whereas other elements had no risk or low risk. Compared with Cd content in soil, only eight rice samples had Cd contents exceeding the safety limit, and sweet potato samples did not exceed the standard. The migration and enrichment capability of rice in order from strong to weak was s follows:Cd>Zn>Cu>Hg>As>Ni>Cr>Pb; the bioactive component of Cd played a significant role in promoting Cd absorption by rice. Soil OM had a bi-directional effect on Cd bioavailability, whereas soil texture had an indirect effect. This comprehensive study shows that the total amount of heavy metals in soil, chemical speciation, biological activities, absorption, and enrichment of heavy metals by crops should be taken into consideration when assessing the ecological risks in the superimposed areas affected by high background and human activities, such as the pyrite mining area.

[Heavy Metal Concentration Characteristics and Health Risks of Farmland Soils in Typical Pyrite Mining Area of the Central Zhejiang Province, China].

In order to ascertain the impact of pyrite mining on the surrounding farmland soil environment and human health, 42 surface soil samples (from 0-20 cm) were collected around the pyrite mining area in Longyou county. In this study, the concentrations of eight heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) and the pH in the topsoil were analyzed, and the concentration characteristics of heavy metals, source analysis, and human health risks assessment were studied using statistical analysis (SA), geo-accumulation index (Igeo), positive matrix factorization (PMF), and the health risk model. The average of ω(Cd), ω(Cu), ω(Pb), and ω(Zn) concentrations exceeded the background values of soils in Zhejiang province and China. According to the agricultural land pollution risk screening values (GB 15618-2018), Cd, Cu, Pb, and Zn were up to 82%, 49%, 42%, and 31%, respectively. The Igeo shows that the major pollutant element in the soils was Cd, followed by Cu, Pb, and Zn. The PMF analysis indicates that nature sources (As, Cr, and Ni), comprehensive pollution sources caused by high geological background and mining of ore-forming geological bodies (Cd, Cu, Pb, and Zn), and anthropogenic sources (Hg) were the three major sources of heavy metals in the study area, with contributions of 32%, 46%, and 22%, respectively. The results of the health risk assessment indicate that the major non-carcinogenic factor triggering risks was the ingestion of Pb; Cr exposure had carcinogenic risk for adults, and Cr and As exposure had carcinogenic risk for children.

[Selenium Threshold for the Delimitation of Natural Selenium-Enriched Land].

The nationwide Se-enriched threshold plays a key role in identifying China's selenium-enriched land resources and developing characteristic agricultural practices. In this study, we used the cooperative data of 10222 sets of crops and roots in China for the past 10 years with a systematic analysis of the selenium content characteristics of the soil and the status of selenium-enriched agricultural products. The preliminary estimates of the selenium-enriched threshold based on a bulk crop-soil linear model and population selenium-intake are presented. Finally, a collaborative analysis model of soil selenium-enrichment rate and crop selenium-enrichment rate is established, coming up with the nationwide Se-enriched threshold:total selenium ≥ 0.40 µg·g-1 in paddy soil, and total selenium ≥ 0.30 µg·g-1 in dryland soil. The threshold passed the feasibility test in 13 provinces, providing strong support for the China Geological Survey to formulate and promulgate this technical standard for the delimitation of the natural selenium-enriched land.