Yinggang Wang

The fate of heavy metals in agricultural soils is governed by organo-mineral–microbial interactions, which predictive models often fail to capture. The competitive sorption mechanisms of Cd(II) and Cu(II) on montmorillonite/kaolinite composites (Mont/Kao) functionalized with humic acid (HA) and Pseudomonas putida (P. p), a model system representative of contaminated agricultural soils, were investigated. Batch experiments, XRD, FTIR, and thermodynamic analysis reveal that metal retention is a non-additive function of competing interfacial processes. Bacterial biomass dominated sorption, accounting for >50% of total metal uptake, with capacity ranked as: P. p > Mont/Kao-P. p > Mont/Kao-HA-P. p > Mont/Kao-HA > Mont/Kao. Humic acid exerts a dual, concentration-dependent role: Low levels enhanced adsorption via mineral dispersion, while high levels induced surface masking, suppressing bacterial binding sites. Competition was highly asymmetric: Cd(II) reduced Cu(II) maximum adsorption capacity by 75.5% in the Mont/Kao-HA system by preferentially occupying montmorillonite interlayer sites, whereas Cu(II) inhibited Cd(II) below pH 6. Single-metal sorption was characterized by positive ΔS° (32.96–58.89 J·mol⁻¹·K⁻¹), indicative of inner-sphere complexation, while negative ΔS° under competitive conditions signals a transition to outer-sphere complexation. This work provides mechanistic insights into site masking, competitive displacement, and ternary cation bridging controlling metal immobilization in organo-mineral assemblages.

Soil contamination is a significant threat to global food security and public health. Accurate apportionment of pollutant sources is a prerequisite for developing science-driven pollution control protocols. This research was undertaken in Huanren Manchu Autonomous County, located in Northeast China. With a resident population of approximately 216,000, the county boasts abundant natural resources including mineral deposits, biodiversity, and water reserves. Data were preprocessed using Principal Component Analysis (PCA) to enhance interpretability for subsequent modeling. Abbreviated Principal Component Score Multilinear Regression (APCS-MLR) and Positive Matrix Factorization (PMF) were cross-validated to ensure robust source attribution, thereby addressing the limitations of single-method uncertainty. This triangulation approach, combined with probabilistic Monte Carlo Simulation and health risk assessment, enabled a multi-dimensional evaluation of contamination pathways and risks. This aspect has been underexplored in heavy metal (HM) studies of mining-impacted agricultural soils. The average concentrations of eight heavy metals were as follows: Cr (74.0 mg/kg), Ni (32.1 mg/kg), Cu (118.9 mg/kg), Zn (541.7 mg/kg), Cd (2.2 mg/kg), Pb (202.0 mg/kg), Hg (0.3 mg/kg), and As (12.0 mg/kg). Quantitative pollution source analysis revealed three primary contributors to soil HMs: industrial point sources (contributing 46.1%), which is the most significant contributor to pollution; agricultural sources (contributing 22.2%) and natural sources (contributing 31.7%). Industrial sources, as the primary local pollution contributors, will effectively guide relevant government departments in formulating targeted management policies and measures. Probabilistic risk evaluation yielded two crucial findings: (1) Non-carcinogenic hazard indices for adults and children remained below 1, indicating acceptable risks from the presence of HMs in agricultural soils, however, (2) Carcinogenic risks surpassed the 1 × 10⁻⁴ cancer risk benchmark for 100% of children and 32.3% of adults. Carcinogenic risks to the human population arising from individual HMs showed the following sequence: Cr > Ni > As > Zn > Cd. This research has not only revealed an alarmingly high risk of cancer in the study region due to HMs accumulation in its agricultural soils but also, by identifying the crucial sources, provided a scientific basis for controlling this harmful pollution.

Dechlorane Plus (DP), an emerging type of persistent organic pollutant (POP), poses potential harmful effects on plants, animals, and humans alike, garnering increasing attention. Urban surface soil is easily accessible to urban residents, and its environmental conditions have a more significant impact on urban residents. However, there are few studies on related DP contamination. In this study, the contamination of DP in surface soil from Shenyang City, Liaoning Province, China, was investigated. Soil samples were collected from 33 different locations in May and June 2023. The total DP (∑DP), anti-DP, and syn-DP were determined by gas chromatography and ranged from not detected (ND) to 77.80 ng/g, from ND to 61.50 ng/g, and from ND to 16.30 ng/g, respectively. The mean values were 33.60 ± 18.93 ng/g, 27.01 ± 14.32 ng/g, and 8.57 ± 4.55 ng/g. The findings indicate that anti-DP is more readily detectable than syn-DP, attributable to the lower proportion of syn-DP in the overall DP production and the distinct physicochemical properties of DP isomers. The fsyn [syn-DP/(anti-DP + syn-DP)] is 0.14–0.40, with a mean value of 0.22. This aligns closely with the values observed in commercial DP formulations, suggesting that the primary sources are derived from commercial DP products. Contour maps show that DP concentrations are influenced by urban land use and DP production. Based on the Tyson polygon method, the DP inventory was calculated at approximately 1.18 tons, with the unit area load exceeding previously reported values. The results also show that the health risks of DP are minimal, but children are more susceptible to the impacts of DP than adults, and oral ingestion is a more critical exposure pathway.

Heavy metals are commonly present in polluted soil in mining areas. In this study, we investigated 10 sites of farmland soil in the heavy metal tailing dam collapse area (TDCA) with the dominant phyla Acidobacteriota, Proteobacteria, Bacteroidetes, and Planctomycetes. The heavy metal dam collapse area is a composite contamination area of multiple heavy metals, with Cd, Pb and Zn being the most severely contaminated, and the levels of Hg and Cu exceeding the screening values at some of the sites. The Shannon, Chao1 and ACE indices revealed high microbial diversity but low relative abundance of microorganisms at the severely polluted TDCA1 and TDCA3 sites. The results of redundancy analysis (RDA) showed that Hg (Max = 4.31 mg/kg) and Cu (Max = 100 mg/kg) were important factors affecting soil microbial community in the TDCA compared to other heavy metals. Correlation analysis of heavy metals with microbial communities showed that RB41 (Acidobacteria) was more resistant to high concentrations of Cd, Pb, and Zn pollution. The genera of UTCFX1 (Chloroflxi) and norank_TRA3-20 had strong tolerance to the heavy metal Hg. Cu was significantly negatively correlated with norank_WD2101_soil_group (P < 0.05). Therefore these can be used as indicators for monitoring potential heavy metal contamination. The results can be used to predict the changes in the ecosystem of the mining area to maintain its ecological balance and health.

Due to potassium persulfate’s excessive reaction speed and severe impact on the soil environment, slowing down the reaction rate and reducing its environmental impact is an important but challenging matter. Hence, microencapsulation technology was taken to modify potassium persulfate, and potassium persulfate microcapsules were used to remediate the PAHs-contaminated soil. The results of XRD and an infrared spectrum identified that the core material (potassium persulfate) exists after being encapsulated by the wall material (stearic acid), and there was no chemical reaction between the core material and wall material. The results of the sustained release effect and kinetic equation showed that the release rate of the potassium persulfate microcapsules was close to 60% after 48 h, and it had a good sustained-release effect compared with previous studies. The results of the radical probe revealed that the free radicals produced from potassium persulfate microcapsules activated by Fe²⁺ were the main reasons for the degradation of PAHs, and SO₄⁻· played the most important major role in the degradation of PAHs, followed by ·OH, and the reducing substances also played an auxiliary role. The results also suggested that potassium persulfate microcapsules not only degraded PAHs in soil (53.6% after 72 h) but also had fewer negative effects on the environment, and they even promoted the growth and development of microorganisms and increased the germination rate of seeds due to the slow-release effect of the microcapsules. This work reveals the degradation mechanism of potassium persulfate microcapsules and provides a new amendment of potassium persulfate in the remediation of PAHs-contaminated soil.