Soil & Environmental Health最新文献

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.

Organic fertilizer-derived emerging contaminants, such as antimicrobials and estrogens, could migrate vertically into subsoil and potentially reach shallow groundwater aquifers. This study investigated the vertical distribution of these antimicrobials and estrogens in soil profiles, as well as their potential ecological risks, in the Yellow River Delta of China, a major agricultural zone. A total of 47 emerging contaminants, including 42 antimicrobials, 2 antimicrobial degradation products, and 3 estrogens, along with reference contaminant atrazine, were detected within 7 soil layers that were down to 1 ​m below the surface at 10 farmland sites. The concentrations of individual contaminants varied greatly in these soil layers, ranging from 0.0095 to 1680 ​ng/g. Antimicrobials were ubiquitous (detection frequency up to 85%), while estrogens were only detected occasionally (detection frequency up to 27%). The concentrations of antimicrobials and estrogens in subsoil were generally lower than those in topsoil, e.g., the total concentrations of antimicrobials and estrogens in Level 1 (0–5 ​cm) and Level 7 (70–100 ​cm) at all sampling sites were up to 99.3 and 29.2 ​ng/g, respectively. Nineteen out of the 26 emerging contaminants with relevant toxicity data could pose medium to high ecological risk to potential aquatic organisms, soil microbes, and/or crop plants. The ecological risks posed by the organic fertilizer-derived emerging contaminants were comparable in different soil layers in the soil profiles. These findings demonstrate the pseudo-persistence of these emerging contaminants in soil profiles and their substantial potential ecological risks. The data also indicate the need of controlling the residues of antimicrobials and estrogens in organic fertilizers to protect the quality and health of farmland soils.

Ionic liquids (ILs) are eco-friendly substitutes for volatile organic solvents due to their unique properties, fostering widespread adoption across academic fields and industries. This review critically evaluates their application in soil remediation, comparing their performance and environmental footprint against conventional soil remediating agents. The review provides insights into the interplay of IL characteristics, optimal environmental conditions, and contaminant removal mechanisms, while also exploring strategies for modifying and regenerating ILs. Optimal conditions for contaminant removal involve acidic pH for organic compounds and metals, with high temperatures proving beneficial for metal extraction. ILs remove organic contaminants from soil via electrostatic attraction and π–π interactions. In contrast, heavy metal extraction is facilitated by forming complexes through hydrogen bonding, coordination bonding, and electrostatic interactions. The incorporation of acetone and calcium chloride reduces the viscosity while sodium azide effectively prevents microbial degradation of ILs. Using magnetic ILs, acid elution, ultrasonication, and supercritical CO₂ extraction techniques enhances IL regeneration efficiency and facilitates their reuse, thereby minimizing secondary pollution and reducing cost. Life cycle assessment of common ILs for remediation, such as 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF₄]) and 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF₆]) showed that producing 1 ​kg of [Bmim][BF₄] emits 6.75 ​kg CO₂, whereas manufacturing 1 ​kg of [Bmim][PF₆] releases 5.70 ​kg CO₂, indicating [Bmim][PF₆] has a lower global warming potential due to its environmentally-friendly precursors. The review advocates for continuous improvements in production processes and the development of ILs synthesized from renewable sources to mitigate environmental impacts and enhance their suitability for soil remediation.

Mine lands contaminted with heavy metals pose environmental risks, and thus reclamation is paramount for improving soil, plant, animal, and ecosystem health. A metal-contaminated alluvial mine tailing, devoid of vegetation, received 224 ​Mg ​ha⁻¹ of both lime and biosolids in 1998, and long-term reclamation success was quantified in 2019 with respect to soils, plants, and linkages to animals. Reclamation success was quantified using the Soil Management Assessment Framework (SMAF), in conjunction with bioavailable (0.01 ​M CaCl₂ extractable) and plant-available (Mehlich-3 extractable) soil metal concentrations, X-ray absorption spectroscopy, plant metal concentrations, and plant quality characteristics. Results showed that all soil indicators were improved in successfully-reclaimed areas as compared to on-site degraded areas, including increases in soil aggregate stability, pH, plant-available P and K, soil organic C, potentially-mineralizable N, microbial biomass C and β-glucosidase activity and decreases in soil bulk density and electrical conductivity. Ofindicators, unitless soil health scores were assigned based on the SMAF, with data suggesting that bulk density, wet aggregate stability, potentially- mineralizable N, microbial biomass C, pH, and electrical conductivity should be monitored in the future. The long-term effects of lime and biosolids application have improved soil physical, biological, and overall soil health. Plant metal concentrations have decreased by an order of magnitude since early reclamation, with most plant metal concentrations being tolerable for domestic livestock consumption. From an animal health perspective, feeding grasses from this site during latter parts of a growing season may need supplemental feed to provide greater protein and energy content, and to reduce potentially-harmful Cd concentrations from food chain bioaccumulation. However, a health concern exists based on soil bioavailable Cd and Zn concentrations that exceed ecological soil screening levels. Still, plants have stabilized the soil and acidity remains neutralized, leading to long-term improvements in soil health, with overall improved ecosystem health.

The rhizosphere hosts diverse microbes crucial for plant growth. This is because plant roots secrete organic compounds, thereby enriching the rhizosphere with essential nutrients. Biochar improves soil quality, while nano-biochar shows promise in contaminant adsorption. Its production from biochar is easily achievable through top-down methodologies including hydrothermal synthesis, ball-milling, sonication, and centrifugation. The advantages of employing nano-biochar are evident in several aspects. Nano-biochar exhibits enhanced properties such as greater surface area, increased porosity, and greater reactivity compared to bulk-biochar. This enhanced surface area allows for greater adsorption capacity, enabling nano-biochar to effectively immobilize contaminants in the environment. In this review, detailed interactions and applications of nano-biochar are summarized. Nano-biochar interacts with contaminants in the rhizosphere by electrostatic interaction, cation-π interactions and redox reactions, influencing soil microbial communities and plant resilience. Nano-biochar can adsorb contaminants from the rhizosphere, such as heavy metals and organic pollutants. Thus, it helps alleviate abiotic stresses, improves nutrient availability, and supports plant growth. Furthermore, the mechanistic processes of surface oxidation, mineral dissolution, organic matter release, and mechanical fragmentation in biochar are discussed, culminating in biochar ageing and nano-biochar formation, which creates a conducive environment for microorganisms. This review examines nano-biochar-rhizosphere interactions, highlighting their effects on plant-soil dynamics and resilience. Future research should address synthesis scalability and safety concerns to unlock nano-biochar's potential in sustainable agriculture and environmental management.

Environmental evaluations of metal nanoparticles (NP) rely on seperating the effects of the metal NP from its dissolution products. However, the coordinating or counter anion used in experimental controls may potentially influence biotic indicators used in ecotoxicology and soil health monitoring, thereby compromising the ability to detect real nanoparticle effects and potentially confounding interpretation of metal-NP impacts. Using the example of copper oxide (CuO) NP, we demonstrate for the first time that depending on the anion used in the metal ion control (CuCl₂ versus CuSO₄), different and even opposite conclusions may be drawn for CuO-NP effects. This include a key biological indicator such as enzyme activity in soil samples. Moreover, this effect was specific to environmental conditions and indicator type, raising important methodological and interpretive implications to assess the CuO-NP impacts on soils. Our findings imply that assessments of soil health impacts of metal-NP should consider multiple coordinating anion controls for a given metal, especially when the counterion is known to impact the biological indicator including nutrient ions.