Journal of environmental quality最新文献

Intensification of US livestock production, generating an estimated 1.27 billion metric tons of manure per year from nearly 10 billion animals, presents both a nutrient resource and an environmental challenge. This technical review synthesizes current knowledge on manure's agronomic and soil health benefits versus its environmental risks. The study compares different management approaches, land application, stockpiling, lagoons, and critically assesses advanced treatment and valorization technologies, including anaerobic digestion, solid-liquid separation, nutrient recovery (struvite precipitation, ammonia stripping), biochar co-composting, and precision application tools (injection, variable-rate spreading, and real-time nutrient sensors). Adoption drivers such as regulatory frameworks (Clean Water Act, concentrated animal feeding operation permits, and California SB 1383), economic incentives (Environmental Quality Incentives Program [EQIP] cost-share and carbon and nutrient credit markets), and digital innovations are also evaluated alongside persistent barriers of high capital costs, logistical constraints in nutrient transport, knowledge gaps in emission quantification (CH₄, N₂O, and NH₃), pathogen fate, and site-specific trade-offs among air, water, and soil quality. The review also outlines potential future scenarios, from incremental technology mainstreaming to integrated circular biorefineries, and highlights research priorities to optimize manure as a circular resource while safeguarding ecosystem and human health. By contextualizing manure management within a climate-resilient, circular agricultural economy, this review identifies the research gaps and informs researchers, extension agents, and policymakers on strategies to advance sustainable livestock systems in the United States and beyond.

This study examines trends in nitrate contamination in Iowa's community water systems (CWS) from 2000 to 2022, focusing on the characteristics of CWS that are most vulnerable to elevated nitrate levels and those likely to be impacted by a lower maximum contaminant level (MCL). Using Safe Drinking Water Act (SDWA) compliance data for CWS currently without nitrate removal, we analyzed nitrate levels across CWS types, source water type, well characteristics, and geography. Results show that large CWS serving >100,000 people frequently exceed 5 mg-N/L due to their reliance on surface water that is vulnerable to non-point source pollution. Small systems (<10,000 consumers) often exhibit episodic spikes in nitrate, often during spring and early summer, coinciding with fertilizer use and rainfall-driven leaching. Shallow and pre-1990 wells were disproportionately affected. Geospatial mapping analysis identified nitrate hotspots in agriculturally intensive regions. A future MCL based on an annual average of 5 mg/L-N would only affect ∼25 CWS annually, far fewer than those impacted under a scenario where any instance above 5 mg/L-N would be a violation. These data-driven findings support future policy for nitrate regulation and drinking water protection.

The natural background contribution from grasslands and forest lands is important to consider in research and management to address the contribution of agricultural, industrial, and urban lands to water quality degradation. To our knowledge, no study has compiled and analyzed reference water quality from small reference grasslands and forests even though land use export coefficients for background water quality are assigned at that scale in decision support tools and models, total maximum daily load projects, and comparative analysis. Thus, our major objective was to summarize nitrogen (N), phosphorus (P), and sediment loads in runoff from grassland and forested reference watersheds. Measured annual nutrient loads were available from 13 grassland and nine forest reference sites in 12 North American Level II ecoregions. The grassland reference sites were relatively arid with annual runoff <353 mm (average runoff coefficient = 0.11), and forest reference sites were humid with runoff ranging from 108 to 1274 mm (average runoff coefficient = 0.34). Grassland reference watersheds tended to have higher annual sediments loads (>300 kg/ha), while forest reference watersheds tended to have higher dissolved N loads. This research provides valuable summary results and initial comparisons related to reference water quality across the United States that can serve as a benchmark to compare how anthropogenic activities affect this vital ecosystem service.

Agricultural soils lose P to waterbodies and C to the atmosphere. Reversing the C trend requires change in management (carbon farming), but what is the effect of carbon farming practices on P transport from soils to waterbodies? This was empirically studied by analyzing the P loss risks from 20 farms participating in a 5-year on-farm carbon farming experiment. We evaluated the effect of C farming practices on soil P balance, P stocks, and potential P loss through surface runoff, subsurface drainage, and erosion. We integrated data from fertilizer application, yield, soil test P, site hydrology, and erosion into P loss estimation tools (P indices and annual phosphorus loss estimator model). Based on the results, carbon farming (cover crops, ley farming, improved grazing, soil amendments, and subsoiling) had only minor impacts on P loss compared with the current soil conservation practices (minimum tillage, vegetated buffers, and crop rotation) already applied by the farms. P fertilization was not adjusted in response to P availability, therefore resulting in weak P balances. Furthermore, only a small fraction of the field area (18%) was responsible for the majority (50%) of the estimated P loss, indicating the importance of P loss hotspots. C farming practices do not seem to improve water quality unless they are tailored to target key processes of P loss such as maintaining a negative P balance on high-P sites, reducing runoff, and focusing on local critical source areas.

Agricultural soils are sources of nitrous oxide (N₂O) and, under prolonged saturation, methane (CH₄)-two potent greenhouse gases (GHGs). Soil management, field topography, and climate all influence GHG emissions, yet their interactions are not well understood. Over 17 months, we evaluated how three distinct management systems-Conventional, a soil health system (Soil Health), and a flocculated manure solid amendment (Flocculated Solids)-interacted with topographically high and low areas to influence N₂O and CH₄ emissions in a 21 ha corn (Zea mays L.) silage field in western Vermont, during a period of abnormally high precipitation. At 18 plots (3 treatments × 2 topographic positions × 3 replicates), we measured GHG fluxes year-round alongside soil temperature, moisture, and inorganic nitrogen. Annual N₂O emissions were 4.4 times greater in Soil Health-Low plots (74.3 kg N₂O-N ha^-1 year^-1) than in Flocculated Solids plots, which had the lowest emissions (17.0 kg N₂O-N ha^-1 year^-1). Annual CH₄ emissions were greatest in low plots across all treatments, with low plots emitting 2.2 times more CH₄ than high plots. Boosted regression tree models identified soil moisture, ammonium, CO₂ flux, and nitrate as the strongest predictors of daily N₂O fluxes. For CH₄, inundation duration was the dominant driver, with emissions increasing sharply after >40 days of continuous saturation. Treatment and topography explained <5% of emissions in both models, indicating that their effects are primarily indirect, modifying soil moisture, nitrogen availability, and organic matter inputs that ultimately drive GHG emissions.

To better understand the dynamics of per- and polyfluoroalkyl substances (PFAS) in complex freshwater ecosystems, we performed a systematic meta-analysis of PFAS distributions and spatiotemporal variance in biota of the Laurentian Great Lakes watersheds. We reviewed 50 publications that contained 2489 records (primarily of fish and birds) spanning 42 years of biological sampling. Using this dataset, we built generalized additive models for six compounds-perfluorooctanesulfonic acid (PFOS) and five perfluoroalkyl carboxylic acids (PFCAs)-routinely detected in biological tissues. Estimated concentrations of PFOS, the dominant compound in biota, increased along a lake gradient from west (Lake Superior) to east (Lake Ontario), and PFCA levels also varied across the lakes. Modeled temporal trends of PFOS in biota were highly significant but non-linear, and may be correlated with industrial production, the timeline of compound phase-out, food web shifts, and lake-specific conditions. In the eastern lakes, biotic PFOS concentrations were highly variable through time, spanning one to two orders of magnitude, and model estimates generally declined following industrial phase-out of the compound. In the western lakes, PFOS levels did not demonstrate substantial changes from lower baseline concentrations. PFOS, but not PFCA, levels biomagnified from primary producers to apex predators across the Great Lakes. Model output indicated that eggs, blood, and liver samples were consistently the most contaminated tissues. Our review also revealed several data constraints in the literature revolving around lake coverage, taxonomic biases, and methodological inconsistencies. Addressing these data gaps will maximize the inferential ability of future synthetic studies of PFAS.

During manure storage, methane (CH₄) is produced by anaerobic decomposition of organic matter by methanogens. Frequent removal and further processing of manure from the barn can reduce CH₄ emissions. However, little is known about how much CH₄ is lost during the adaptation of methanogens to the changing environment from the gut to storage. The objective was to determine the breakdown of organic matter and emission of CH₄ from dairy cattle and pig slurry in the first 3 days after excretion. CH₄ and carbon dioxide (CO₂) emissions from fresh slurry (<1 h old) were measured in climate respiration chambers. Three treatments were studied: (1) dairy cattle slurry with a temperature of 15°C (CS15), (2) dairy cattle slurry with a temperature of 20°C (CS20) and (3) pig slurry with a temperature of 20°C (PS20). CH₄ emissions from both dairy cattle and pig slurry were minimal during the first 3 days after excretion. Temperature influenced emission rates, resulting in higher CH₄ and CO₂ emissions from CS20 than from CS15. Cumulative CH₄ and CO₂ emissions from PS20 were not significantly different from those of CS20, but emission patterns of pig slurry differed from cattle slurry. Less than 0.3% of the methane potential and only about 0.7% of the IPCC Tier 1 emission factor were emitted as CH₄ during the first 3 days after excretion. In conclusion, quick removal of manure from the barn can reduce emissions, although immediate removal is not required from a CH₄ emissions perspective.

Iron-modified biochar is a promising cost-effective material for cadmium (Cd)-contaminated soil remediation, yet how the additional iron (Fe) affects Cd uptake and translocation in rice remains unclear. This study compared two Fe-modified biochars, including impregnated biochar (I-PBC) and co-pyrolyzed biochar (Fe-PBC), with raw biochar (PBC) and explored their effects on Cd accumulation in rice under low application rates (0.1%-0.2%, w/w). These rates were selected for field applicability and cost-efficiency in regional agricultural practices. Cd-contaminated acidic soil collected from southeastern China was used in the pot experiments. In the first pot experiment, I-PBC at 0.1% significantly reduced Cd concentrations in rice grains by 26.3%, 43.7%, and 13.5%, compared with the control, PBC, and 0.1% Fe-PBC, respectively. The results from a second experiment (0.1% amendments: PBC, I-PBC, FeSO₄, water-washed PBC) suggest that I-PBC enhances Cd compartmentalization in aboveground tissues by increasing Cd in the cytosolic fraction while reducing soluble Cd proportions, likely sequestering Cd into less metabolically active compartments (e.g., vesicles). Additionally, I-PBC promoted the conversion of Cd into low-toxicity Cd-oxalate complexes, as evidenced by a significant increase in the HCl-extractable Cd fraction (FHCl, predominantly Cd-oxalate) in stems. These findings demonstrate that impregnation is superior to co-pyrolysis for Fe-modified biochar in inhibiting grain Cd accumulation, with key mechanisms involving enhanced Cd chelation by oxalic acid and subcellular compartmentalization. This study highlights the potential of low-dose I-PBC for practical Cd-contaminated farmland remediation.

Phosphorus (P) availability is a critical factor influencing plant growth, particularly in highly weathered tropical and subtropical soils where mineral and organic P sources often exhibit low absorption efficiency. In response to soil low P availability, plants typically undergo physiological and biochemical adaptation, including reduced photosynthetic rates, increased root/shoot ratio, and alterations in the root system. This study aimed to assess changes in the maize root system and their relationship with P absorption and utilization efficiency under field conditions. The experimental design comprised three treatments: pig slurry, mineral fertilizer, and a control with no fertilizer, arranged in a randomized block design with four replications. Key morphological parameters were analyzed at the vegetative (V8) and flowering (R1) phenological stages, alongside physiological and chemical assessments of the aboveground plant parts. Plants grown in soil with a history of pig slurry application had the lowest morphological root parameters, yet demonstrated higher P absorption efficiency, grain yield, and dry matter production. The application of pig slurry and mineral fertilizers increased P and potassium (K) levels in the soil, photosynthetic rates, and dry matter production. These findings underscore the complex interplay between root morphology and nutrient absorption, offering insights into optimizing fertilizer strategies for maize cultivation in low-P availability soils.

Sustainable phosphorus (P) management includes producing food within environmental boundaries for water quality. In regions where environmental boundaries are crossed, it is beneficial to identify P loss hotspots and implement mitigation measures. In this study, we assessed the risk of P losses to shallow groundwater and surface water from agricultural fields on non-calcareous sandy soils with an exceptionally low P sorption capacity and high hydrological connectivity due to shallow groundwater levels and the presence of open trenches. Specifically, we investigated P quantity–intensity relationships in soils from two agricultural fields and monitored groundwater levels and P concentrations in both groundwater and water fluxes from open trenches. The results showed that non-calcareous soils with low sorption capacities reach high P saturation degrees when fertilized to an agronomic optimum based on a P quantity measure. This leads to high reactive P concentrations in soil solution that can be transported to surface water via interflow, overland flow, and land drainage. In these situations, open trenches are a significant P loss pathway because they directly connect the P-saturated topsoil to surface water, leading to P losses ranging from 1.3 to 7.5 kg P ha⁻¹ year⁻¹. Effective mitigation measures include reducing dissolved P losses by reducing the soil P status of fields to environmental soil P intensity thresholds through negative P balances and reducing particulate P losses by implementing erosion control measures. However, because inlet water substantially contributes to the total water discharge, within-catchment mitigation measures may need to be complemented by upstream mitigation measures.