Soil & Environmental Health最新文献

The application of nano-enabled agricultural chemicals introduces metal oxide nanoparticles (NPs) into agricultural soils, with CuO-NPs as one of the most common. Because CuO-NPs can dissolve to release Cu ions, they often display different environmental impacts. As such, it is essential to comprehensively examine the Cu bioavailability of CuO-NPs in soil and its impacts on soil enzyme activities, which are critical for soil health. This research examined how variations in CuO-NP size (10, 40, and 80 ​nm), surface coatings (polyvinylpyrrolidone and polyacrylic acid), and concentrations (100, 250, and 500 ​mg/kg) influenced the extractable Cu in soil and their impacts on selected soil enzymes (acid phosphatase and dehydrogenase). Main indicators were quantified after a 30-day incubation period. The bioactive Cu related to CuO-NPs as determined via CaCl₂ and DTPA extractions indicated that 10 ​nm CuO-NPs had the highest extractable Cu across all incubation times. Besides, polyvinylpyrrolidone and polyacrylic acid coating had little impact on extractable Cu compared to uncoated ones. Unlike CuSO₄, extractable Cu concentrations in CuO-NPs spiked soil increased over time. CuO-NPs dissolution was negatively correlated with soil pH. CuO-NPs after 24 ​h short-term exposure significantly inhibited both enzyme activities across all tested concentrations, with smaller NPs showing greater effect. However, reduced toxicity to enzyme activities was observed after 30 days. A strong negative correlation was observed between CuO dissolution and enzyme activities after 1 and 30 days, indicating Cu ions are the main toxicity source. This study elucidates that CuO-NP size, concentration, surface coating, and exposure duration collectively impact the interactions of CuO-NPs with soil enzymes, providing critical insights into the sustainable use of nanotechnology in agriculture.

Urban agriculture, the cultivation, processing and distribution of plants and animals within urban or suburban boundaries, is becoming an increasingly relevant strategy to enhance food safety for urban residents. With the rapid urbanization in the past decades, three forms of urban agriculture have emerged in China: small-scale, capital-intensive, and tourism-type. Each form presents unique benefits and challenges, and their development has been largely shaped by the local socio-economic context and government policies. The benefits of urban agriculture are numerous including the improvement of community cohesion, promotion of physical health, enhancement of environmental sustainability, and creation of new economic opportunities. However, it also faces many challenges such as land availability, capital shortage, market access, and governmental support. This review summarized the benefits of urban agriculture and its current limitations and challenges, and proposed strategies to overcome these hurdles in China based on successful examples in the Global North. Four specific recommendations were provided to promote urban agriculture in China: integration of urban agriculture into cities, solutions for land and resource use, government support and reactions, as well as planning and regulations. Adoption these recommendations is expected to result in healthier cities and a more robust agricultural system in China.

Arsenic (As) and cadmium (Cd) are prevalent in paddy soils, posing potential threats to food safety and public health. The concentrations of soluble ​As and Cd is sensitive to moisture-driven changes in soil pH and Eh, which is barely described at the critical dry-wet interface. Here, tempo-spatial changes of soluble As and Cd were captured by In-situ Porewater Iterative samplers at the capillary fringe that extended from saturated to unsaturated moisture gradient at the millimeter scale (60 ​mm profile in depth) through two episodic dry-wet cycles (55 days in total). The As and Cd concentrations showed less significant fluctuation in second cycle compared to the initial dry-wet cycle. The study also revealed at the capillary fringe profile (20–40 ​mm), the As concentrations increased from 4.6 μg L⁻¹ in unsaturated soils to 13.5 μg L⁻¹ in saturated soils, while Cd decreased from 3.3 to 0.2 μg L⁻¹. This observed correlation was aligned with the vertical changes in soil Eh (+287 to +381 ​mV) and pH (3.42–6.07). This study found a distinct zone characterized by low As and low Cd concentrations, typically situated approximately 10–30 ​mm beneath the capillary fringe. Upon further analysis, it was determined that soil with an Eh of 249 ​mV and a pH of 4.3 potentially serves as an optimal environment for decreasing As and Cd levels in porewater. These findings suggest that it is feasible to reduce As and Cd concentration in the soil by implementing appropriate depth-controlled water management techniques.

Agro-environmental applications of biochar and biochar in combination with biostimulants require a full understanding of the mobility and fate of the carbon and nitrogen fractions in soils. The effects of biochar and biostimulants on forms of nitrogen and carbon in soil during a field-scale incubation were investigated by a multi-analytical approach. This study was conducted on a tomato-cultivated agricultural land treated with low doses of biochar (about 0.1%) and different biostimulants: Micosat F®, arbuscular mycorrhiza fungi (AMF), or a consortium of Pseudomonas fluorescens, Bacillus sp., and a nitrogen-fixing bacteria (Consortium B). Forms of carbon and nitrogen and their mobility before, during, and after tomato growth, were studied with different techniques including elemental analysis, adsorption and molecular fluorescence spectroscopy, ion chromatography, and a column leaching test. Due to the low load of biochar and the short study time, elemental analyses might not be sensitive enough to determine C and N variation in the soil. Based on the dissolved organic carbon (DOC) and dissolved nitrogen forms, the treatments with biochar and biostimulants affected the mobility of these elements with an overall decrease at the end of tomato growth. The organic carbon is mainly ascribable to humic and fulvic acids, as indicated by spectroscopic analysis. The leaching column test demonstrated that cumulative leached C is about one order of magnitude lower than the DOC. In addition, simulated rain cycles profoundly affected their leaching, so it is important to design leaching tests based on local and seasonal weather conditions. In short, positive effects were observed in the marketable production of tomato when soil was treated with biochar combined with a mixture of biostimulants.

Soil organic carbon (SOC) plays a crucial role in soil health and global carbon cycling, therefore accurate estimates of its spatial distribution are important for managing soil health and mitigating global climate change. Digital soil mapping shows its potential to provide accurate and high-resolution spatial distribution of SOC across scales. To convert SOC content to SOC density (SOCD), two inference trajectories exist for predicting SOCD in digital soil mapping: the direct approach (calculate-then-model) and indirect approach (model-then-calculate). However, there is a lack of comprehensive exploration regarding the differences in their performance in SOCD estimates, particularly in regions characterized by diverse pedoclimatic conditions. To bridge this knowledge gap, we evaluated the two approaches based on model performance of SOCD in France. Using 916 topsoils (0−20 ​cm) from the LUCAS Soil 2018 and 24 environmental covariates, random forest model and forward recursive feature selection were used to build the spatial predictive models of SOCD using direct and indirect approaches. The results show that, using random forest model and full covariates, both approaches show moderate performance (R² ​= ​0.28−0.32). By utilizing forward recursive feature selection model, the number of predictors was reduced from 24 to 9, enhancing model performance for direct approach (R² of 0.35), with no improvement for indirect approach (R² of 0.28). The mean SOCD of the French topsoil was 5.29 and 6.14 ​kg ​m⁻² by direct and indirect approaches, resulting in SOC stock of 2.8 and 3.3 ​Pg, respectively. We found that the direct approach clearly underestimated the high SOCD (>9 ​kg ​m⁻²), while the indirect approach performed much better for high SOCD. Our findings serve as a valuable reference for SOCD mapping, thereby providing a scientific basis for maintaining soil health.

Soil organic matter (SOM) serves as an important indicator of soil health. Soils with high SOM are associated with high crop yield under drought conditions. However, a critical question remains unanswered: is the yield-stabilizing effect of SOM attributable to inherent soil properties, such as soil texture and taxonomy? Or is it driven by dynamic soil properties that reflect the overall health of the soil? Following the Soil Health Assessment Protocol and Evaluation, we derived a soil health score (SHS; range: 0–1) from the SOM concentration by accounting for site-specific variables, including climate, texture, and soil suborder. Using county-level data of rainfed corn across the U.S. from 2000 to 2016, we found that higher SHS were associated with higher yields. During the most severe drought events, an increase of 0.5 in SHS was associated with a 1.15 ​± ​0.18 ​Mg ​ha⁻¹ increment in corn yield, suggesting that high SHS helps to stabilize yield in drought. Interestingly, smaller but statistically significant effects of SHS on yield were found during less intensive droughts. The SOM concentration was a slightly better predictor of corn yield than the SHS. We also found similar effects of SHS on corn yield across different soil types, i.e., different textures or soil suborders, under severe drought conditions. Our results suggest that soil health is a main factor in explaining the yield benefits of SOM, while the effects of soil health were not driven by differences in soil texture or suborder. We argue that the resilience of corn yield against drought can be potentially increased by adopting agronomic practices aimed at augmenting SOM and improving overall soil health across a broad spectrum of geographical locations and site characteristics.

Agrochemicals misuse is common in developing countries with many environmental implications. This work assessed the ecological risk of pesticides, including insecticides, fungicides and herbicides based on earthworms in soils at the lower slopes of Mount Cameroon using the Pesticide Risk in the Tropics to Man, Environment and Trade (PRIMET) model. PRIMET was developed in 2008 in The Netherlands for use in tropical regions. Data on usage scheme and ecotoxicological information were collected and keyed into PRIMET for three main outputs: Predicted Environmental Concentration (PEC), No Effect Concentration (NEC), and Exposure Toxicity Ratio (ETR = PEC/NEC). Pesticides predicted for no acute and no chronic risk to earthworms included fipronil and chlorothalonil. Several pesticides were predicted for an acute risk to earthworms, and they comprised acetamiprid, imidacloprid, lambda-cyhalothrin, and carbendazim when used on maize (PEC ​= ​2.69 ​mg ​kg⁻¹; ETR ​= ​5) and tomato (PEC ​= ​16.15 ​mg ​kg⁻¹; ETR ​= ​30); 2, 4-D and abamectin when used on tomato and ethoprophos. Insecticides exhibiting a possible chronic risk to earthworms comprised acetamiprid, cypermethrin, emamectin benzoate, imidacloprid, indoxacarb, lambda-cyhalothrin, oxamyl, and thiametoxam. The majority of fungicides assessed (83%) posed a possible chronic terrestrial risk, with carbendazim at the top position when applied on tomato (PEC ​= ​16.15 ​mg ​kg⁻¹; ETR ​= ​81). Some herbicides predicted for possible chronic risk based on earthworms included 2, 4-D, diuron, glyphosate, ethoprophos, and metaldehyde. Pesticides with the highest risk to earthworms comprised chlorpyrifos-ethyl, imidacloprid, ethoprophos, and nicosulfuron. The riskiest pesticides should hereby be regulated or replaced by less risky ones. The measurement of pesticide residues in water and food in the various agroecological zones of Cameroon is necessary to shed more light on pesticide ecotoxicology.

Nitrogen deficiency and contamination by potentially toxic elements (PTEs) adversely impact soil health and ecosystem services. Existing tools for assessing contaminated soils, necessary for sustainable management, remain limited. In this study, we introduce an integrated approach using geochemical constituents and biological factors to construct a comprehensive index to evaluate contaminant impacts on soil health. We collected samples in triplicate from six plots within an urban allotment with a history of PTE contamination. Selected biological and chemical characteristics of the samples were quantified to derive impact scores, with a single numerical index representing overall soil quality for each plot. Multivariate, T-statistics and Pearson Correlation analysis were used to identify relationships and differences between selected soil parameters between plots. The role of the free-living amoeba Acanthamoeba in nitrogen recycling was assessed with feeding experiments, enzymatic assays and bioinformatics analysis. The plot with the highest index value, indicative of good health, exhibited higher pH, significantly high microbial load, and a high nitrate to ammonium (NO₃⁻:NH₄⁺) ratio of 5.3. This turnover was associated with Acanthamoeba uptake of exogenous nitrates and secretion of ammonium, through the assimilatory/dissimilatory nitrate reduction pathway. In contrast, the lower index plot with the low nitrogen turnover of 0.69, showed elevated aluminium, low pH activity and a significantly reduced microbial load, dominated by aluminium resistant microorganisms. Our findings highlight the importance of a comprehensive soil quality index by integrating multiple characteristics to assess soil health and contamination. The approach addresses the need for improved tools to identify the direct impact of contaminants on soil biological activity, supporting more sustainable land management.

Fire frequency and severity have increased in recent decades in the western United States, with direct implications for the quantity and composition of soil organic matter (SOM). While the effects of wildfire on soil carbon (C) and inorganic nitrogen (N) have been well studied, little is known about its impacts on soil organic N. Since organic N is the most abundant form of soil N in conifer forests and dominant source of plant N facilitated by symbiotic mycorrhizae and mineralization, better understanding of post-fire organic N chemistry will help address a critical gap in our understanding of fire effects on SOM. Here, we characterized changes to organic N chemistry across fire severity gradients resulting from two wildfires that burned lodgepole pine (Pinus contorta) forest along the Colorado/Wyoming border, USA. One representative gradient was selected for high-resolution analysis based on results from bulk data (total C and N, and pH). Mineral soils were collected from two depths in low, moderate, and high severity burned areas and adjacent, unburned locations one year following the Ryan and Badger Creek fires. Nuclear magnetic resonance spectroscopy and 21 tesla ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry analysis showed that N content and aromaticity of water-extractable SOM (0–5 ​cm depth) increased with burn severity, while minimal changes to 5–10 ​cm depth were observed. Heterocyclic N species are generally higher in toxicity compared to their non-nitrogenated counterparts, which prompted soil toxicity measurements. Complementary Microtox® analysis revealed a positive relationship between increased fire severity and increased soil toxicity to Aliivibrio fischeri (microbial test species). These findings add to our molecular-level understanding of organic C and N responses to wildfire severity, with likely implications for nutrient cycling, forest recovery and water quality following severe wildfire.