Site-specific ecological effect assessment at community level for polymetallic contaminated soil

A critical review of biochar as an environmental functional material in soil ecosystems for migration and transformation mechanisms and ecological risk assessment

At present, biochar has a large application potential in soil amelioration, pollution remediation, carbon sequestration and emission reduction, and research on the effect of biochar on soil ecology and environment has made positive progress. However, under natural and anthropogenic perturbations, biochar may undergo a series of environmental behaviors such as migratory transformation, mineralization and decomposition, and synergistic transport, thus posing certain potential risks. This paper outlines the multi-interfacial migration pathway of biochar in "air-soil-plant-animal-water", and analyzes the migration process and mechanism at different interfaces during the preparation, transportation and application of biochar. The two stages of the biochar mineralization process (mineralization of easily degradable aliphatic carbon components in the early stage and mineralization of relatively stable aromatic carbon components in the later stage) were described, the self-influencing factors and external environmental factors of biochar mineralization were analyzed, and the mineral stabilization mechanism and positive/negative excitation effects of biochar into the soil were elucidated. The proximity between field natural and artificially simulated aging of biochar were analyzed, and the change of its properties showed a trend of biological aging > chemical aging > physical aging > natural aging, and in order to improve the simulation and prediction, the artificially simulated aging party needs to be changed from a qualitative method to a quantitative method. The technical advantages, application scope and potential drawbacks of different biochar modification methods were compared, and biological modification can create new materials with enhanced environmental application. The stability performance of modified biochar was compared, indicating that raw materials, pyrolysis temperature and modification method were the key factors affecting the stability of biochar. The potential risks to the soil environment from different pollutants carried by biochar were summarized, the levels of pollutants released from biochar in the soil environment were highlighted, and a comprehensive selection of ecological risk assessment methods was suggested in terms of evaluation requirements, data acquisition and operation difficulty. Dynamic tracing of migration decomposition behavior, long-term assessment of pollution remediation effects, and directional design of modified composite biochar materials were proposed as scientific issues worthy of focused attention. The results can provide a certain reference basis for the theoretical research and technological development of biochar.

Major influencing factors identification and probabilistic health risk assessment of soil potentially toxic elements pollution in coal and metal mines across China: A systematic review

Deposition of potentially toxic elements (PTEs) in soils due to different types of mining activities has been an increasingly important concern worldwide. Quantitative differences of soil PTEs contamination and related health risk among typical mines remain unclear. Herein, data from 110 coal mines and 168 metal mines across China were analyzed based on 265 published literatures to evaluate pollution characteristics, spatial distribution, and probabilistic health risks of soil PTEs. The results showed that PTE levels in soil from both mine types significantly exceeded background values. The geoaccumulation index (Igeo) revealed metal-mine soil pollution levels exceeded those of coal mines, with average Igeo values for Cd, Hg, As, Pb, Cu, and Zn being 3.02-15.60 times higher. Spearman correlation and redundancy analysis identified natural and anthropogenic factors affecting soil PTE contamination in both mine types. Mining activities posed a significant carcinogenic risk, with metal-mine soils showing a total carcinogenic risk an order of magnitude higher than in coal-mine soils. This study provides policymakers a quantitative foundation for developing differentiated strategies for sustainable remediation and risk-based management of PTEs in typical mining soils.

Comparative study on anthropogenic impacts on soil PAHs: Accumulation and source apportionment in tourist and industrial cities in Hebei Province, China

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous organic contaminants in urban soils. The accumulation and source identifications of PAHs within a city have been frequently studied. However, impacts of urbanization development modes on PAHs accumulation patterns by taking a city as a whole have been seldom reported. Four cities with two development modes in Hebei province, Chengde and Zhangjiakou (tourist cities) and Handan and Tangshan (industrial cities), were selected. The concentrations of 16 priority PAHs in soils in the study areas were investigated. The results showed that the average concentrations of Σ16PAHs in Handan (2517 μg/kg) and Tangshan (2256 μg/kg) were more than twice of those in Chengde (696 μg/kg) and Zhangjiakou (926 μg/kg) approximately. Lines of evidence, provided by a combination of diagnostic ratios, pairwise correlation, and PMF methods, revealed that the dominant sources of PAHs in either city were industrial emission, vehicle emission, and petrogenic/biogenic process but with different proportions. Linear fittings based on Bayesian kernel machine regression analysis (BKMR) were constructed to illustrate the impact of industrialization on PAHs accumulation. The probability of excessing the 10 % (376 μg/kg) and 50 % (1138 μg/kg) of current ∑16PAHs would be higher than 90 % given the gross industrial production per unit area >5.00 × 106 and 20.5 × 106 CNY/km2, respectively. The proposed threshold values of industrialization are of significance for determining industrial structure and proportion in urban management.