[Preparation of Iron-modified Biochar and Its Application in Arsenic Contaminated Soil Remediation].

Biochar has a range of advantages including large porosity, high specific surface area, and strong adsorption capacity. It has been widely used in environmental pollution remediation, soil improvement, and carbon sequestration and emission reduction. Arsenic (As) is a highly toxic pollutant widely distributed throughout the soil. In typical surface soils, the most common forms of As are arsenite (AsO33-) and arsenate (AsO43-). Since most biochar surfaces are negatively charged, the adsorption efficiency of biochar to arsenic is usually low, and the biochar material needs to be modified to enhance its As adsorption performance. Iron-based materials, such as zero valent iron and iron oxide, are excellent As adsorption materials with wide environmental sources. They can be loaded to biochar to form iron-modified biochar via precipitation, pyrolysis, ball-milling, and micro-biological methods. The combined advantages of the iron-modified biochar will expand the application of biochar materials in environmental remediation. Based on a systematic analysis of the literature on iron-modified biochar in recent years, this study reviewed the common preparation methods of iron-modified biochars; analyzed biochar substrates, iron-modified biochar, and their synergistic mechanisms on As adsorption; and briefly expounded the application status of iron-modified biochar in soil pollution remediation. The prospects of the future research direction of iron-modified biochar were put forward as a reference for the large-scale application of biochar materials in the future.

[Heavy Metal Contamination and Health Risk Assessment of Corn Grains from a Pb-Zn Mining Area].

A total of 92 corn grain samples, around the Pb-Zn mining area in Southwest China, were collected to evaluate the contamination and health risk of heavy metals. Heavy metals including Pb, Zn, Cd, Cr, and Ni in samples were analyzed. A single factor pollution index and comprehensive pollution index were calculated to assess the quality of corn grains. The potential health risks to adults and children due to the intake of these heavy metals through consumption of crops were evaluated using the health risk index. The results showed that the average contents of Pb, Zn, Cd, Cr, and Ni in corn grains were 0.30, 23.75, 0.21, 1.33, and 1.15 mg ·kg-1, respectively, Among the metals, the content of Zn, Pb, Cd, Cr, and Ni exceeded the national food hygiene standards. The Nemero index of Pb, Cd, Cr, and Ni ranged from 4.32 to 9.07, indicating an extremely high level, whereas the contamination of Zn reached an alarming level. The assessment results of the comprehensive health risk index for the corn grains indicated that the contamination of heavy metals poses health risks to adults and children by food ingestion; moreover, the children were more sensitive to various heavy metals than the adults. Principle component analysis revealed that the first main component dominated the sources of Pb, Cd, Cr, and Ni, while the second main component, Zn, might have originated from sources different from the other heavy metals. Positive correlations were not observed between the heavy metals in corns and soils.

[Principal Component Analysis and Ecological Risk Assessment of Heavy Metals in Farmland Soils around a Pb-Zn Mine in Southwestern China].

The farmland soil around a Pb-Zn mine in southwestern China was studied. One hundred forty-nine surface soil samples were taken from 0-20 cm depth, and the contents of As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn were tested. The correlations among these heavy metals were studied with multivariate analysis, and the potential sources of the metals were identified. The environmental risk of the metals was evaluated with the Potential Ecological Risk Index method. The results showed that the amounts of Cd, Pb, and Zn were at relatively high level, with average concentrations of 15.56, 419.4, and 933.4mg·kg-1 respectively, indicating the soil was heavily polluted. The average concentrations of Hg and As were 0.13 and 37.3mg·kg-1, suggesting moderate soil pollution. The average concentrations of Cu, Ni, and Cr were lower than Yunnan soil background values. The multivariate analysis suggested that the sources of Cd, Pb, Zn, Hg, and As were similar and came mainly from smelting activities in the mining area. The sources of Cu, Ni, and Cr were similar and can be attributed to natural sources. The comprehensive potential ecological risk index was 2294.8, which suggested a high potential ecological risk. In general, the farmland soils in the research area were polluted seriously by the mining and industrial activities.

[Prediction of PCBs uptake by vegetable in a representative area and evaluation of the human health risk by Trapp model].

Air, soil and vegetable samples were collected from an e-waste disassembly site and analyzed for characteristic contaminants PCBs. Based on the measured PCBs concentrations in soil and air, PCBs concentration in leafy vegetables was predicted by Trapp Model and the sources, composition of PCBs in vegetable and influencing factors were analyzed. By using human health risk assessment model of USEPA, risk to human health from consumption of vegetable that take up PCBs from environment was evaluated. The results showed that the Trapp Model could give good prediction of PCBs concentrations in leafy vegetables based on PCBs concentration in the soil and air. For instance, the measured sum of seven PCBs in vegetable was 51.2 microg x kg(-1) and the predicted value was 39.9 microg x kg(-1). So the predicted value agrees well with the measured value. The gaseous PCBs were the main source of PCBs in leafy vegetables, and the model predicting results indicated that the contribution rate was as high as 98.8%. The uptake pathway, n-octanol/water partition coefficient (K(ow)) and the n-octanol/air partition coefficient (K(oa)) of PCBs determine the concentration and composition of PCBs in vegetables. The duration needed for PCBs uptake to reach equilibrium was in good correlation with lgK(ow) and lgK(oa). Multiple linear regression analysis indicated that lgK(oa) was more important. Carcinogenic risk from consumption of PCBs contaminated vegetables was 10 000 times higher than that of gaseous PCBs, and the no-carcinogenic risk was increased by approximately 200 times. The main reasons are firstly the vegetables take up and accumulate more toxic PCBs with high-chloride substitutes and consequently the oral toxic factors of PCBs increase dramatically. Secondly, an adult takes 71 times more PCBs via consumption of vegetables than via inhalation of air.