Soil & Environmental Health最新文献

We investigated the potential of tailings from phosphate mining, consisting of phlogopite, carbonate minerals calcite and dolomite, and residues of apatite, to serve as a stabilizing agent in the remediation of Pb-contaminated soil in situ or on-site. In a 2.5-year field trial, test plots located in a former shooting range area were surface-treated with the tailings and analyzed for tailings-induced changes in Pb solubility and thus potential mobility within the soil profile. The factors and mechanisms controlling tailings-induced changes in Pb solubility in various soil types, and the susceptibility of Pb to leaching down the soil profile following the treatment, were investigated in supplementary laboratory-scale experiments carried out with horizon-specific soil samples collected from the field site. In the tailings-treated soil, the dissolution of the carbonate fraction of the tailings and the subsequent increase in soil pH contributed to the displacement of shot-derived Pb²⁺ ions by the carbonate-derived calcium ions (Ca²⁺) and the adsorption of Pb²⁺ by soil organic matter and Al, Fe, and Mn (hydr)oxide surfaces. Moreover, the apatite fraction of the tailings formed poorly-soluble compounds with Pb, particularly in soils high in exchangeable Pb²⁺ with respect to their cation exchange capacity. Consequently, the Pb solubility in tailings-treated soils substantially decreased. The reduction in Pb solubility was most evident in the organic topsoil high in Pb. Despite the liming effect of the tailings, and the susceptibility of Pb to form organic complexes conducive to solubilization upon an increase in pH, we found no evidence of tailings-induced leaching of Pb down the soil profile.

Reducing the oral bioavailability of metal contaminants including As, Cd, , and Pb in foods can protect human health. Studies showed reduced metal bioavailability with elevated Ca and Fe intake; however, the effectiveness of enhancing food Ca and Fe bioavailability remains unknown. Based on a mouse bioassay and using metal accumulation in mouse tissues (kidneys and liver) as the bioavailability endpoint, this study investigated the roles of casein phosphopeptides (CPP, food nutrition fortifier) in lowering the As, Cd, and Pb bioavailability from consuming a metal-contaminated wheat. The CPP amendment at 0.10–0.50% in wheat promoted its Ca bioavailability, causing 33–62% and 59–80% decreases in the gene expression encoding for duodenal Ca and phosphate transporters in mice. This limited transcellular transport of Cd²⁺ and inorganic arsenate via Ca and phosphate transporters respectively, thus leading to 27% and 34% decreases in Cd and As contents in mouse kidneys fed with wheat at 0.50% CPP amendment. In addition, CPP promoted the colonization of Feacalibaculum and Bifidobacterium in mouse gut, likely promoting As excretion in feces by 81–112%. In contrast to As, and Cd, CPP failed to reduce Pb contents in mouse tissue after consuming CPP-amended wheat, probably by elevating wheat-Pb solubility in the intestinal fluid by 48–136%. However, co-amendment of 0.30% CPP and 500 ​μg ​g⁻¹ Ca as Ca gluconate lowered the As, Cd, and Pb contents in mouse kidneys by 38–71%. The data indicate that fortifying Ca together with CPP in wheat can reduce human exposure to multi-metals via dietary intake.

Soil organic carbon (SOC) is crucial for soil health and quality, and its sequestration has been suggested as a natural solution to climate change. Accurate and cost-efficient determination of SOC and its functional fractions is essential for effective SOC management. Visible near-infrared spectroscopy (vis-NIR) has emerged as a cost-efficient approach. However, its ability to predict whole-profile SOC content and its fractions has rarely been assessed. Here, we measured SOC and its two functional fractions, particulate (POC) and mineral-associated organic carbon (MAOC), down to a depth of 200 ​cm in seven sequential layers across 183 dryland cropping fields in northwest, southwest, and south China. Then, vis-NIR spectra of the soil samples were collected to train a machine learning model (partial least squares regression) to predict SOC, POC, MAOC, and the ratio of MAOC to SOC (MAOC/SOC – an index of carbon vulnerability). We found that the accuracy of the model indicated by the determination coefficient of validation (R_val²) is 0.39, 0.30, 0.49, and 0.48 for SOC, POC, MAOC, and MAOC/SOC, respectively. Incorporating mean annual temperature improved model performance, and R_val² was increased to 0.64, 0.31, 0.63, and 0.51 for the four carbon variables, respectively. Further incorporating SOC into the model increased R_val² to 0.82, 0.64, and 0.59, respectively. These results suggest that combining vis-NIR spectroscopy with readily-available climate data and total SOC measurements enables fast and accurate estimation of whole-profile POC and MAOC across diverse environmental conditions, facilitating reliable prediction of whole-profile SOC dynamics over large spatial extents.

Agroecosystems are the largest source of anthropogenic N₂O fluxes. While cover crops (CC) offer benefits for soil health, their impacts on greenhouse gas fluxes are inconsistent. In the southeastern US, where intensive agriculture and low CC adoption are prevalent, few studies have investigated CC impact on soil N₂O fluxes. Our study explored the effects of CC species and management practices on soil N₂O fluxes during the winter CC growing season in Mississippi, which was conducted in a non-tilled corn cropping system with seven CC treatments. We measured in situ soil N₂O fluxes, along with soil moisture and temperature, throughout the CC growing season from 2022 to 2023. Surface soil samples were also collected to analyze soil mineral nitrogen (N) content and enzyme activity. Over the study period (a total of 188 days), cumulative N₂O fluxes were 0.50–1.03 ​kg N₂O–N ha⁻¹, with the lowest values from the annually-rotated Elbon rye treatment and the highest from the annually-rotated Austrian winter pea. Our results show that both CC treatments and sampling time significantly affected soil N₂O fluxes. There was a strong positive correlation (r ​= ​0.34, p ​< ​0.05) between N₂O fluxes and NO₃–N content, which was lowest under continuous rye and rotated-rye treatments (0.31 and 0.34 ​mg ​kg⁻¹ ). The results suggest that Elbon rye effectively reduced soil N₂O fluxes during this period by lowering the soil NO₃–N content, the primary substrate for denitrification. This study is one of the few studies to examine the impacts of cover crops on soil N₂O fluxes in cropping systems in the southeastern US, offering insights into the cover crop effects on soil N₂O fluxes during their growing season.

It is indisputable that microplastics (MPs) can profoundly alter nitrogen transformation in soil. However, it remains poorly understood how MPs impact soil nitrogen processes. This review systematically analyzed literature published in recent years related to the impact of MPs on nitrogen transformation. After reviewing the environmental behavior of MPs in soil media, the mechanisms of action and key factors of MPs’ effects on soil nitrogen transformation are elucidated. The size, shape, concentration, and type of MPs significantly alter nitrogen transformation. When MPs enter the soil, they can significantly affect the habitat and diversity of soil microorganisms and the transformation of soil nitrogen by adsorbing pollutants, releasing additives, and altering the physicochemical characteristics of the soil. As organic substrates, MPs can directly affect microbial community structure by promoting microbial colonization. Besides, MPs can also be toxic to soil microorganisms by coming into direct contact with cell surfaces. Microorganisms, key enzymes, and functional genes associated with nitrogen transformation respond to the presence of MPs, thereby affecting the nitrogen conversion process. At the last, measures to mitigate soil MPs contamination are suggested. The article highlights the effects of MPs on soil nitrogen transformation factors, leading to valuable insights into microbially-mediated nitrogen transformation processes in MP-contaminated soils. It offers useful information for determining nitrogen regulation and assessing ecological risks in soils contaminated by MPs.

Anthropogenic activities have left a legacy of contaminated vacant land, which disproportionately affects lower income communities and can have detrimental impacts on human health, particularly children. A management solution is needed to address this widespread lead contamination in urban soils of vacant lots. In this study, high-Fe biosolids incinerator ash (BIA) was evaluated for its ability to sequester soil Pb. Five blends were created using BIA and different amount of other products (dredge, biosolids compost, and yard waste compost) to determine the most effective treatment to reduce Pb bioaccessibility in the soil. The sorption capacity of the BIA for Pb was evaluated by mixing the BIA with Pb(NO₃)₂ at 1000 to 100,000 ​mg ​Pb/kg BIA. The contaminated soil from Cleveland, OH was treated with five BIA-based blends at a 1:1 (w/w) ratio, and Pb bioaccessibility was evaluated using USEPA Method 1340 ​at pH 2.5 and the Physiologically Based Extraction Test (PBET) at pH 2.5. BIA was a strong sorbent for Pb, sorbing ∼100% of the Pb from solution at 10,000 ​mg/L with only 41% bioaccessibility based on Method 1340 ​at pH 2.5. The blend containing 4.5%, 10%, or 19% BIA reduced the Pb bioaccessibility by 48% from the control based on both bioaccessibility methods. The bioaccessible Pb determined by PBET was less than that by USEPA Method 1340 ​at pH 2.5. However, similar reductions in bioaccessible Pb between blend-treated soils and the unamended soil were observed for all bioaccessibility methods. Plant growth assays showed the blends to have little to no significant impact on clover growth, mortality, or flower production, with the blend containing 10% BIA showing greater biomass yield. Results showed BIA-based blends were able to reduce bioaccessible Pb in the soil. This remediation approach may improve the urban living environment and protects public health.