Hydrochemistry, quality, and integrated health risk assessments of groundwater in the Huaibei Plain, China.

Groundwater is an essential freshwater resource utilized in industry, agriculture, and daily life. In the Huaibei Plain (HBP), where groundwater significantly influences socio-economic development, information about its quality, hydrochemistry, and related health risks remains limited. We conducted a comprehensive groundwater sampling in the HBP and examined its rock characteristics, water quality index (WQI), and potential health risks. The results revealed that the primary factors shaping groundwater hydrochemistry were rock dissolution and weathering, cation exchange, and anthropogenic activities. WQI assessment indicated that only 73% of the groundwaters is potable, as Fe2+, Mn2+, NO3-, and F- contents in the water could pose non-carcinogenic hazards to humans. Children were more susceptible to these health risks through oral ingestion than adults. Uncertainty analysis indicated that the probabilities of non-carcinogenic risk were approximately 57% and 31% for children and adults, respectively. Sensitivity analysis further identified fluoride as the primary factor influencing non-carcinogenic risks, indicating that reducing fluoride contamination should be prioritized in future groundwater management in the HBP.

Influence of biochar produced from negative pressure-induced carbonization on transformation of potentially toxic metal(loid)s concerning plant physiological characteristics in industrially contaminated soil.

Soil contamination and its subsequent impact on the food chain is a pressing challenge in the present day. The application of biochar has demonstrated a significant and positive effect on soil health, thereby enhancing plant growth and development. However, the application of biochar (BC) produced from negative pressure-induced carbonization to mitigate metal(loid) contamination is a new strategy that has been studied in current research. Results depicted that the application of biochar derived from the negative pressure carbonization (vacuum-assisted biochar (VBC) has a significant (p ≤ 0.05) positive impact on plant growth and physiological characteristics by influencing immobilization and speciation of metal(loid) in the soil system. Moreover, the interactive effect of VBC on physiological characteristics (photosynthesis, gas exchange, and chlorophyll contents) and antioxidant activities of maize (Zea mays L.) was significantly (p ≤ 0.05) positive by confining the translocation and movement of metal(loid)s to the aerial part of the maize plant. X-ray diffraction (XRD) provided information on the structural and chemical changes induced by the VBC-500 °C explaining metal(loid) adsorption onto mineral surfaces and complexation that can affect their mobility, availability, and toxicity in the contaminated soil. Fourier transform infrared spectroscopy (FTIR) further provided a more detailed understanding of the metal(loid)s and biochar complexation mechanisms influenced by VBC-based functional groups -OH, C-Hn, -COOH, CO, C-O-C, CC, C-O, C-H, OH, and C-C in the binding process. These results suggest that the application of biochar prepared at 500 °C under negative pressure-induced carbonization conditions to the soil is the most efficient way to reduce the uptake and transfer of metal(loid)s by influencing their mobility and availability in the soil-plant system.

Fine chemical speciation and environmental impact capacity of trace elements with different enrichment levels in coal.

Enriched trace elements in coal are considered to have a high environmental impact, but the extent of the influence of the enrichment level is unclear. To study the chemical speciation and environmental behavior of trace elements in coal at different enrichment levels, representative coal samples from multiple provinces in China were collected, including bituminous coal I-L2 from Inner Mongolia with high concentrations of Be, Y, Zn, Tl, U, Er, and Yb, and 72-9 coal from Anhui enriched with Cu, Cd, Pb, V, and Zn. The chemical speciation of trace elements in coal was analyzed using a variety of techniques, including X-ray Photoelectron Spectroscopy (XPS), Near Edge X-ray Absorption Fine Structure (NEXAFS), and sequential chemical extraction procedures. Cluster analysis was used for grouping the coal samples based on the enrichment coefficients of trace elements. Coal samples with similar genesis and in closer regions were more likely to be grouped. Metal carbonates and metal sulfate were observed in coals through XPS analysis. The main C species in coal were identified as phenolic C, carboxylic C, unsaturated C, and O-alkyl C/carbonyl C through NEXAFS. The amplitude variation of peaks for the fly ash was smaller than that for the feed coal, which showed that the structure of carbon became homogeneous after high-temperature combustion. It was difficult to identify the chemical speciation difference of trace elements with different enrichment degrees in coals through XPS and NEXAFS, but the results of the sequential chemical extraction could compensate. Several enriched trace elements in coal were relatively high in the chemical fractions (exchangeable, carbonates and monosulfides associated, or FeMn oxide bound) that were easy to extract and relatively low in the less insoluble chemical fractions (organic matter-bound, disulfides associated, or silicates associated), indicating that enriched trace elements in coal had higher environmental impact capacity.

Spatial distribution characteristics and prediction of fluorine concentration in groundwater based on driving factors analysis.

Excess fluoride (F-) in groundwater can be hazardous to human health. A total of 360 ground water samples was collected from northern Anhui, China, to study the levels, distribution, and source of F-. And on this basis, predicting the spatial distribution of F- in a wider scale space. The range of F- was 0.1-5.8 mg/L, with a mean value of 1.2 mg/L, and 26.4 % of the samples exceeded the acceptable level of 1.5 mg/L. Moreover, the water-rock interaction (fluorite dissolution) and cation alternate adsorption were considered to be two main driving factors of high F- in groundwater. To further illustrate the spatial effects, the BME-RF model was established by combining the main environmental factors. The spatial distribution of F- was quantitatively predicted, and the response to environmental variables was analyzed. The R2 of BME-RF model reached 0.93, the prediction results showed that the region with 1.0-1.5 mg/L of F- accounts for 47.2 % of the total area. The predicted F- content of nearly 70 % of groundwater in this area has exceeded 1.0 mg/L, which was dominated by Na+ and HCO3- type. The spatial variability of F- in the study area was mainly affected by hydrogeological conditions, and the vertical distribution characteristics were related to the spatial variation of slope, distance from runoff, and hydrochemical types. The results of the study provide new insights into the F- concentration prediction in underground environment, especially in the borehole gap area.

Morphochemical investigation on the enrichment and transformation of hazardous elements in ash from waste incineration plants.

The transformation of heavy metals in ash from waste incineration plants is significant for ash management. The migration behavior of trace elements in ash after combustion, semidry deacidification, fabric filtration, and chelating agent stabilization was investigated from one waste incineration plant. The hazardous elements Zn, Pb, and As were enriched in raw fly ash (ash produced at a combustion temperature of 850-1100 °C) due to their relatively high volatility. Mercury, Cd, and Pb were captured in fly ash2 and processed by activated carbon and fabric filters. The removal rate of As (71%) was the highest among all studied elements due to a large amount of quinquevalent As removed. However, the average removal rate of elements in fly ash was only 13%. In the finally obtained fly ash3 (after chelating agent stabilization), a larger particle size (~100 µm) was found than that of raw ash. Furthermore, fly ash3 contains HgSO4 and trivalent As, which are toxic and likely to be precipitated when the fly ash3 is next utilized or deposited in a landfill, causing environmental risks.