Soil & Environmental Health最新文献

The continuous use of fertilizers and fungicides has triggered copper (Cu) contamination in cacao soils in Ghana, which is a critical issue for the ecological risk and health safety of cacao products. In this study, we investigated Cu pollution, bioavailability, and ecological risk in soil and determined the Cu levels in the cacao nib, shell, and pod husk. Soils were collected at two soil depths (0–15 ​cm and 15–30 ​cm) from 20 cacao farms, under conventional (CCM: chemical-based fertilizers) and organic (OCM: organic-based fertilizers) management practices together with pods. The total Cu concentration ranged from 67.6 to 96.8 ​mg ​kg⁻¹ in OCM and 28.5–33.9 ​mg ​kg⁻¹ in CCM soil, which decreased with soil depth. The enrichment factor revealed minimal Cu enrichment, which was attributed to anthropogenic activity (fungicide and fertilizer applications). The contamination factor and geoaccumulation index values were low for the CCM soils, and moderate for the OCM soils. Both management systems pose a low potential ecological risk to soil biota activity. Bioavailable Cu extracted with CaCl₂, NH₄OAc, and DTPA was dominant in CCM soil and decreased with soil depth. The Cu concentration in cacao plants decreased in the order of shell > pod husk > nib, with nib-Cu being below the threshold (50.0 ​mg ​kg⁻¹) of contamination. The results from the pairwise correlation analysis show that CaCl₂-available Cu is better for evaluating the Cu content in cacao plants. This study reveals the pollution levels associated with cacao management practices, thus providing valuable insights for developing appropriate mitigation strategies.

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.

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.

Phytoremediation of contaminated soil is an environmentally-friendly approach to minimize the impacts of nutrients and heavy metals on an ecosystem. Hence, selecting appropriate plants with phytoextraction potential is paramount to remediatie contaminated soils. This study aimed to investigate the nutrient and metal contents of four natural aquatic plants, including Cyperus rotundus, Eleocharis dulcis, Typha angustifolia, and Schoenoplectus grossus. They were grown in the meadow of a small reservoir in Sri Lanka to assess their phytoextraction ability using plant and soil samples collected at 32 sampling points in the meadow. Their biological concentration (roots/soil), accumulation (shoots/soil), and translocation (shoots/roots) factors were determined to assess element mobility and phytoextraction ability. Total K, Na, Mg, Ca, Zn, Cu, Fe, Mn, As, Pb, and Cd contents of plants and soil samples were measured using an Inductivity Couple Plasma Optical Emission Spectrophotometer. ANCOVA was used as a statistical test to assess the best plant type in terms of nutrient and metal absorption. Plant shoots exhibited significantly greater values for P, Na, Mg, Zn, Cd, and Fe than their roots. Their biological concentration, accumulation and translocation factors were not different among the four plant species. However, these values were >1 for all the species, indicating their potential to be used as hyperaccumulators. T. angustifolia, with its high potential for nutrient and metal accumulation and the highest aesthetic appeal, was selected as the best overall wetland species for phytoremediation purposes.

Gut microbes are crucial for human health, which are usually accumulated in urban wastewater systems. Seven wastewater treatment plants in Australia with distinct population obesity rates between 18% and 33% were selected for wastewater sampling and analysis. Human gut microbiome were detected using metagenomic sequencing to investigate their associations with the community obesity rate. To unravel this complex relationship, a range of algorithm models, including linear discriminant analysis effect size (LEfSe), similarity percentage analysis (SIMPER), statistical analysis of metagenomic profiles (STAMP), linear models for microarray and RNA-Seq data analysis (LIMMA), Relief, ratio approach for identifying differential abundance (RAIDA), least absolute shrinkage and selection operator (LASSO), support vector machine (SVM), Boruta, DESeq2 and analysis of compositions of microbiomes with bias correction (ANCOM-BC), were used to identify potential bacterial biomarkers for obesity in the wastewater microbiome. Among these algorithm models, LEfSe, LIMMA, SIMPER and SVM are effective in identifying multiple microbial biomarkers. Specific human gut microbes, including Ruminococcus_E, Agathobacter, Fusicatenibacter, Anaerobutyricum, Blautia_A and Neisseria, were identified as potential consensus microbial biomarkers for obesity in the population. A high obesity rate is mainly characterized by a high abundance of pathogenic bacteria and microorganisms associated with xenobiotic biodegradation and metabolism, endocrine and metabolic diseases, and transcription pathways. This study underscores the innovative potential of leveraging human gut microbes in wastewater as biomarkers for monitoring obesity levels across communities, offering a novel, cost-effective, and indirect approach to public health surveillance.

Soil fauna including earthworms play a crucial role in various ecosystem functions, thereby contributing to human well-being. The relationships between earthworm populations and environmental factors have frequently been established at regional scales, particularly in urban soils. However, the diversity and community assemblage of earthworms, as well as their influencing mechanism at plot scale, have rarely been studied. Based on the earthworm assemblage from 29 sites in 12 residential communities, the average earthworm abundance, biomass, and species richness were 59.0 individuals/m², 21.7 ​g/m², and 1.59 species, respectively. Based on a generalized linear mixed model, vegetation distribution pattern, vegetative cover type, and surrounding built environment all affected earthworm biomass. However, none of these residential variables significantly affected its community assemblage. Variation partitioning in canonical ordination revealed that edaphic properties, rather than landscapes, played a significant role in explaining the variation in its community assemblage, with an approximate contribution of 23%. The abundance and biomass of earthworms at the plot-scale in this study were consistent with previous studies at regional scales. However, the species richness at plot scale was lower than those at regional scale, suggesting that earthworm biodiversity may not accurately represent that at a larger scale, species-area relationship. The results indicate a shift in the driving factors of earthworm community assemblage from edaphic property variation at the plot scale to edaphic, historical, and biogeographical heterogeneities at the regional scale. Certain species that are sensitive to key edaphic/landscape parameters are potential candidates for monitoring soil ecological health.

Efficient and sustainable sludge management is a significant environmental and health challenge. Sludge-treatment reed beds (STRBs) are widely recognized as a cost-effective, highly efficient, and environmentally friendly solution for sludge treatment and dewatering. This study investigated the bacterial community composition and diversity in pilot-scale STRBs operating at different sludge loading rates (75, 100, and 125 ​kg ​m² year⁻¹). 16S rRNA V4 DNA sequencing was used to assess the diversity of the bacterial communities within the sludge samples. The relative abundance of prokaryotic taxa was affected by all treatments. As the sludge loads increased, the Shannon entropy and evenness diversity also increased for the STRBs and unplanted beds. Interestingly, the presence of reeds resulted in significantly lower Shannon and evenness indices than unplanted beds, regardless of the sludge. Additionally, the correlation network analysis revealed distinct microbial clusters with distinct responses to reeds and sludge loads. Principal component analysis evidenced an association between cluster 5 and organic matter decomposition, primarily at higher sludge doses, while clusters 4 and 6 were related to sludge decomposition at lower doses. Additionally, cluster 4 was associated with nutrient removal. The formation of distinct microbial niches was linked to sludge stabilization and nutrient removal and was influenced by both sludge loading rates and the presence of reeds. Future research can leverage these findings to innovate pollutant removal and ecosystem services for sludge treatment, thus advancing sustainable sludge management and environmental preservation.

Even though the concentrations of the total cadmium (Cd) in paddy soils from different countries have been reported, the exchangeable-Cd (Ex-Cd) concentrations in these soils are unknown despite its importance in agriculture. This study was conducted with a total of 5460 soil samples collected in Sri Lanka, representing six agro-climatic zones, six soil orders, and three irrigation types. The Ex-Cd concentrations in soil samples were extracted using 0.01 ​M CaCl₂ and analyzed using an inductively coupled plasma-mass spectrophotometry. The Ex-Cd concentrations were <0.31–163 ​μg ​kg⁻¹, with mean and median concentrations being 14.1 and 8.98 ​μg ​kg⁻¹, respectively, which was affected by both agro-climatic and soil conditions. Samples from the Wet zone, particularly the Wet zone Low country, had higher Ex-Cd (24.1 ​μg ​kg⁻¹) than those from the Dry zone Low country (11.6 ​μg ​kg⁻¹). Among the soil orders, Histosols (21.3 ​μg ​kg⁻¹) and Inceptisols (19.5 ​μg ​kg⁻¹) had the highest Cd concentration while Vertisols had the lowest (6.3 ​ ​kg⁻¹). The irrigation types only affected Ex-Cd concentrations in Dry zone Low country, but not in other agro-climatic zones. Overall, it is important to consider agro-climatic zones, soil orders, and irrigation types when implementing agronomic strategies to mitigate the risk associated with Cd accumulation in paddy fields.