The production of titanium dioxide in China generates substantial waste acid and ferrous sulfate, which are repurposed into polyferric sulfate for industrial wastewater treatment. However, this water purification agent contains heavy metals like Ti, V, Mn, Cr, Co, Cu, Ni, Zn, Ba, and Pb, posing unrecognized environmental risks. This study identified these risks through pollutant screening and the process analysis of a Jiangsu-based titanium dioxide enterprise, evaluating the potential impacts on water quality and worker health. The results show that concentrations of manganese and titanium in the polyferric sulfate reached up to 163 mg/L and 631 mg/L, respectively. Notably, the non-carcinogenic hazard quotients (HQs) for cobalt, vanadium, and manganese were 307, 5.6, and 2.6, all exceeding the safe limit of 1, with cobalt presenting a particularly significant risk due to its low reference dose (RfD) of 0.0003 mg/kg-d. This study concludes that national standards should be revised to include limits for these pollutants to ensure safer practices in industrial wastewater treatment.

During the natural cooling process of magnesium slag stockpiles in the open air, the phase transformation of gamma-dicalcium silicate (γ-C₂S) induces a powdering phenomenon, resulting in the generation of a large amount of PM10 and PM2.5 dust. Based on the dust emission model of stockpiles and the Gaussian dispersion model, combined with the Monte Carlo simulation method, this study conducted a quantitative assessment of the environmental risk of heavy metals (Pb, Cd, Hg, As, Cr(VI)) in dust to the surrounding residential areas. The results show that the enrichment degree of heavy metals in PM2.5 is significantly higher than that in PM10. At a downwind distance of 1000 m, the exceedance multiples of Cr(VI), As, and Cd reach 131.5, 23.6, and 51.8 times, respectively. The total carcinogenic risk (9.2 × 10⁻⁷) and total non-carcinogenic hazard quotient (0.15) in the residential area are below the limits, but the contribution rates of As and Cd are relatively high. Sensitivity analysis further reveals that the moisture content of the stockpile, dust removal rate, and distance are the key control parameters affecting the environmental risk. Based on the research findings, it is recommended to increase sprinkling frequency, install windbreak nets, and promote magnesium slag utilization to effectively control dust risks.

This study assessed heavy metal contamination in industrial solid waste (S1, S2, S3, and S4) from the Yangtze River Delta region, employing nine risk assessment methods including total content indices (e.g., Igeo, CF) and speciation indices (e.g., ICF, GCF). Four types of industrial solid waste not classified as hazardous but containing heavy metals were analyzed. Key findings revealed significant variability in risk assessments based on chemical speciation versus total content. For example, while S1, S3, and S4 exceeded background levels, S4 showed higher mobility of Pb, Cr (VI), Cu, Ni, and As despite lower overall content. Elements like Cd and Cr (VI) exhibited discrepancies between total content and speciation-based assessments due to low background values and high toxicity. Multi-element indices (DC, RI) indicated higher pollution degrees compared to speciation indices (GCF, GRI). These results underscore the need for integrating multiple assessment methods to accurately evaluate environmental risks in judicial practices.

The utilization of iron tailings in road construction poses significant environmental risks due to the complex release mechanisms of pollutants and varying regional conditions. This study integrates an exponential decay model with an instantaneous pollutant transport model, employing Monte Carlo simulations to assess risks and regional characteristics. Results show high Potential Hazard Indices (PHIs) for arsenic, manganese, barium, nickel, and lead, with PHI values between 4.2 and 22.7. Simulations indicate that manganese and nickel concentrations may exceed groundwater standards, particularly in humid areas. The study recommends controlling the iron tailings mixing ratio based on climate, suggesting limits of 35% in humid, 60% in semi-humid, and more lenient ratios in arid and semi-arid regions. It also underscores the need for improved risk assessment methodologies and region-specific management strategies at the national level.

This study assessed the environmental risks and regional variations associated with using titanium gypsum in road construction. It revealed that the conventional HJ/T299-2007 leaching method underestimates heavy metal leaching rates from titanium gypsum by approximately 1%, potentially leading to an underestimation of environmental risks. Further analysis indicated that Pb, Ni, As, Cd, and Zn leach from titanium gypsum road materials to varying extents, while Mn poses a notable exceedance risk with an 11% probability of surpassing limits and a maximum exceedance factor of 1.8. Significant disparities in regulatory thresholds for titanium gypsum pollutants were observed among 11 provinces along the Yangtze River, with the highest threshold (Qinghai) nearly five times greater than the lowest (Jiangxi). Rainfall was identified as a key contributor to these regional differences. The findings suggest that traditional assessment methods underestimate titanium gypsum risks and highlight the need for enhanced national solid waste evaluation frameworks. Additionally, given the substantial regional risk variations, differentiated management strategies are recommended.

This study examines the assessment and management strategies for odor risks during emergency cleanup of VOC-contaminated waste. By analyzing illegally dumped VOC waste, the impact on odor intensity levels and exceedance probabilities in nearby residential areas was evaluated. Utilizing a VOC source emission model, a Gaussian plume dispersion model, and Monte Carlo simulations under various meteorological conditions, the effectiveness of the control measures was assessed. Key pollutants included ethylbenzene, toluene, styrene, and m/p-xylene, which, despite posing minimal short-term health risks (PHI: 0.17–0.64), exhibited significant odor risks (Odor PHI: 127–1156). At 20 m from the source, the probability of the odor intensity exceeding Level 2.5 approached 100%, decreasing to 85% at 50 m and further declining with distance. Atmospheric stability shifts—from very unstable (Class A) to stable (Class F)—increased the odor intensity from 0.5 to 2.5. Under moderately stable conditions (Class E), m/p-xylene had a 44.2% probability of exceeding an odor intensity level of 2.5. Even at 250 m, the odor intensity levels ranged between 1.2 and 1.7, remaining perceptible. Effective mitigation strategies include establishing appropriate buffer distances and using adsorption materials like activated carbon.