[Pollution Risk and Contribution Analysis of Pb, Cd, and As in Soils and Crops Under Different Land Use Types in Longyan City].

A total of 174 soil samples and 87 grain samples were collected in two typical fields in Longyan City. The pollution index method, Hakanson potential ecological risk index method, and EPA human exposure risk assessment model were used to evaluate the pollution status, ecological risk, and health risks of heavy metals Pb, Cd, and As in soil of different land use types. The contributions of Pb, Cd, and As to soil and crop pollution risk were also analyzed. The results indicated that the pollution levels of Pb, Cd, and As in soils and crops of different utilization types in regionⅠwere low. Cd was the main soil pollutant and ecological risk factor, contributing 55.3% to comprehensive soil pollution and 60.2% to comprehensive potential ecological risk, respectively. The pollution levels of Pb, Cd, and As in soils and crops in regionⅡwere high. Pb and Cd were the main soil pollutants and ecological risk factors, contributing 44.2% and 51.6% to comprehensive pollution and 23.7% and 67.3% to comprehensive potential ecological risk, respectively. Pb was the main pollution factor of crops, contributing 60.6% and 51.7% to the comprehensive pollution of coix and rice, respectively. The carcinogenic risks of Cd and As in soil of the two typical regions for adults and children were all within the acceptable range under the oral-soil exposure pathway. The contribution of Pb, Cd, and As to the total non-carcinogenic risk in regionⅠwas Pb (68.1%)>As (30.5%)>Cd (1.38%). There was no carcinogenic risk of Pb in rice in the two typical regions under the oral-rice intake pathway. The contribution of Cd and As to carcinogenic risk in adults and children were As (76.8%)>Cd (22.7%) and Cd (69.1%)>As (30.3%), respectively. Three pollutants in regionⅠand Ⅱ had high non-carcinogenic risk, and As was the most significant contributor (84.0% and 52.0%, respectively), followed by Cd and Pb.

[Ecological and Health Risk Assessments Based on the Total Amount and Speciation of Heavy Metals in Soils Around Mining Areas].

Topsoil and supporting crop samples around a mining area were collected in Longyan City, and the total amounts and speciation of Pb, Cd, and As in the samples were determined. The ecological risk and human health risk assessment of soil heavy metals Pb, Cd, and As were carried out using the Hakanson potential ecological risk assessment method, the ecological risk classification method based on the principle of geochemical statistics, and the health risk assessment method in accordance with the characteristics of human exposure parameters in China. The results indicated that the heavy metal elements in the soil in the study area exceeded the environmental quality standards for Pb and Cd, and the heavy metal contents in cereal grains exceeded the food limit value mainly for Pb. The proportion of the four bioavailable forms except the residue state followed the order of Pb>Cd>As. The ecological risk assessment results based on the total amount of heavy metals and bioavailable forms showed that Cd was the most important ecological risk factor. The single potential ecological risk of Cd and the comprehensive ecological risk of Pb, Cd, and As in the soil based on bioavailable forms were significantly reduced compared with that based on the total amount. The proportion of medium and superior samples decreased from 100% and 50.0% to 17.2% and 7.81%, respectively, and the divided risk zone basically contained all the warning points of exceeding the standard of crops. Oral ingestion was the main carcinogenic and non-carcinogenic exposure route of heavy metals. In terms of carcinogenic risk, the risk of human carcinogenic health exposure to Cd and As was within the acceptable range, regardless of whether bioavailability was considered. Among the non-carcinogenic risks, the non-carcinogenic risk of the heavy metal Cd was negligible. When only the total amount of heavy metals was considered, the non-carcinogenic risk index of Pb and As under the three exposure pathways ranged from 0.14 to 8.65 and from 0.04 to 2.85, respectively. After considering the adjustment of bioavailability, the non-carcinogenic risk of As was greatly reduced and could be considered to no longer have non-carcinogenic risk. Although the non-carcinogenic exposure risk index of Pb was reduced by 84.7%, the maximum value still reached 1.69, which would cause non-carcinogenic harm to the population and was the key to soil remediation in mining areas.

[Geochemical Patterns and Source Analysis of Soil Heavy Metals in an Iron and Manganese Ore Area of Longyan City].

Bedrock and soil samples from different soil profile layers were collected in an iron and manganese ore area of Longyan City and total amounts of Pb, Cd, and As were determined. The geochemical patterns of three heavy metal elements in the soil were studied using ordinary Kriging interpolation and their sources were also analyzed. High concentrations of Pb and As were found near the mining area to the west, at the intersection of two rivers in the middle, and near the waste rock heap in the east of the study area, while the main area of Cd contamination is located near to the mining areas and ore dressing plant. Based on a horizontal section, the content of Pb, Cd, and As in soils from the high-value region of each layer decreased with horizontal distance from the mining area. Vertically, the concentrations of heavy metals in different soil layers were significantly correlated. Near the mining area, Pb, Cd, and As concentrations first increased and then decreased with depth. In other high-value regions, the concentrations of these three heavy metals decreased with soil profile depth. These heavy metals inherit the characteristics of the deposit and bedrock during the weathering process, and the content of Pb and As in the soil at different depths was significantly positively correlated with granite and diorite content. Although As has been artificially influenced by mining, this influence does not appear to be strong; parent rock in the study area shows higher concentrations of heavy metals, while at the same time, the Pb and Cd content of soil is significantly higher than in the rock indicating the influence of human activities including mining, transportation, and agricultural production. Further attention should now be paid to the quality and safety of agricultural products, crop growth, and possible environmental risks in the study area.

[Comparision of Ecological Risk Assessment Based on the Total Amount and Speciation Distribution of Heavy Metals in Soil:A Case Study for Longyan City, Fujian Province].

A total of 110 topsoil samples and 61 crop samples along the Lantian-Yangdong Villages were collected in Shizhong, Longyan City. The total amount and speciation of heavy metals(Pb, Cd, As) in soil and crops were determined. The characteristics of the absorption of heavy metals by specific crops in the study area were analyzed, and a new method of risk assessment based on the heavy metal speciation and its bioavailability was established by statistical analysis. This new method was used to evaluate the soil ecological risk and to compare it with the traditional method of potential ecological risk index (RI). The results indicated that the Lantian-Yangdong Villages were located in an area where Pb, Cd, and As mainly originate from the natural soil parent material with weak human disturbance. There was no significant Pb or As pollution in the whole region. Cd was the main pollutant with low pollution intensity. Four types of biological components except for the residual form followed the order of Cd(53.28%) > Pb(43.28%) > As(30.71%). Correlation and regression analyses of total metal concentrations, heavy metal speciation, and crop uptake in the study area showed that the correlations between the total amount of heavy metals and the ion exchange state, carbonate state, and other active forms were low; the results even showed nonlinear relationships between those variables.The ion exchange state had the greatest effect on the absorption of Pb, Cd, and As by coix seed and rice. From the perspective of bioavailability, the new method based on the heavy metal speciation was more accurate than the traditional method based on the total amount of heavy metals.