Journal of environmental quality最新文献

Phosphorus (P) loss from soils can contribute significantly toward P enrichment in water bodies, impairing water quality. Application of soil amendments is a viable strategy to decrease soluble P in surface soils. Since soluble P is reduced through different mechanisms that are amendment-specific, blended amendments could be a better approach than single amendment applications; however, very little information is available on blended amendment effects in reducing P loss from soils. We compared the effectiveness of gypsum (CaSO₄·2H₂O), Epsom salt (MgSO₄·7H₂O), and alum [Al₂(SO₄)₃·18H₂O] applied singly or blended in different ratios in reducing water-extractable P (WEP) and Mehlich-3 P of two soils (0- to 15-cm depth) with contrasting P status (Mehlich-3 P of 7.1 mg kg^-1 and 202 mg kg^-1) from the Red River Valley region in MB, Canada. Ten treatments used for the laboratory incubation study were unamended control, gypsum or Epsom salt at 2.5 or 5 Mg ha^-1, alum at 2.5 Mg ha^-1, and four blended treatments of gypsum: alum or Epsom salt: alum at 1:1 or 2:1. Treated soils were saturated and incubated for 2 weeks and analyzed for WEP (an indicator of risk of P loss) and Mehlich-3 P (plant-available P) concentrations. All amendments significantly reduced the WEP concentrations compared to control in both soils. The blended amendments, particularly gypsum-alum blends, performed better than unblended amendments in reducing the potential risk of P loss. Mehlich-3 P concentration was not influenced by amended treatments, suggesting no significant decrease in plant-available P with amendments in both soils.

Population growth in coastal areas increases nitrogen inputs to receiving waterways and degrades water quality. Wetland habitats, including floodplain forests and marshes, can be effective nitrogen sinks; however, little is known about the effects of chronic point source nutrient enrichment on sediment nitrogen removal in tidally influenced coastal systems. This study characterizes enrichment patterns in two tidal systems affected by wastewater treatment facility (WWTF) effluent and assesses the impact on habitat nitrogen removal via denitrification. We collected intact sediment cores from prevalent habitats in a tidal freshwater river (TFZ; swamp forest) and a tidal estuarine creek system (EST; salt marsh) upstream and downstream of a WWTF outfall, and quantified dissolved gas fluxes across the sediment-water interface during wet conditions in early summer and dry conditions in late summer. Data collected during two synoptic water quality monitoring campaigns complimented laboratory experiments to provide environmental context for biogeochemical processing. The two systems exhibited different enrichment patterns such that the river-dominated TFZ system was characterized by consistently elevated nitrate + nitrite concentrations downstream of the WWTF, whereas precipitation and tidal influence affected nutrient distributions in the EST creek. Downstream sediments in TFZ exhibit an apparent saturation response, while upstream rates may be limited by other factors, such as labile organic matter availability. In contrast, downstream sediments in EST denitrify at higher rates than upstream during wet conditions that may enhance transport of effluent. This work provides information on ecosystem functioning in human-influenced environments and can be of use in developing nature-based solutions, such as water treatment wetlands, for nitrogen removal.

The Eastern Corn Belt (ECB) node of the Long-Term Agroecosystem Research (LTAR) network is representative of row crop agricultural production systems in the poorly drained, humid regions of the US Midwest and a significant focus for addressing water quantity and quality concerns affecting Lake Erie and the Gulf of Mexico. The objectives of this paper were to (1) present relevant background information and collection methodology, (2) provide summary analyses of measured data, and (3) provide details for accessing the dataset and discuss potential database applications. The ECB-water quality (ECB-WQ) database is comprised of hydrology and water quality data from three privately owned farms in Northwest Ohio and Northeast Indiana and is available for download through the United States Department of Agriculture Ag Data Commons. The dataset includes information on site characteristics (drainage area and soil type), field management (fertilizer application, planting rate, and yield), and daily discharge and measured nutrient concentrations from surface and subsurface tile drainage outlets. Discharge and water quality vary widely across the ECB and are paramount to developing innovative management strategies that balance crop production goals with environmental targets. Discharge is generally greater from subsurface tile drainage compared to surface runoff. Phosphorus concentrations are typically greater in the surface runoff compared to tile drainage, while nitrogen concentrations are greater in subsurface tile drainage. The ECB-WQ database was developed to better facilitate understanding of water quantity and quality within this unique, systematic, artificially tile-drained region and is critical for understanding implications of field management practices, quantifying environmental and production processes, constraining hydrology/water quality models, and informing future water quality policies.

Agricultural researchers are increasingly encouraged to engage with stakeholders to improve the usefulness of their projects, but iterative research on the design and assessment of stakeholder engagement is scarce. The USDA Long-Term Agroecosystem Research (LTAR) Network recognizes the importance of effective engagement in increasing the utility of information and technologies for future agriculture. Diverse stakeholders and researchers at the Kellogg Biological Station (KBS) LTAR site co-designed the KBS LTAR Aspirational Cropping System Experiment, a process that provides a testing ground and interdisciplinary collaborations to develop theory-driven assessment protocols for continuous stakeholder engagement. Informed by prior work, we designed an assessment protocol that aims to measure participant preferences, experiences, and perceived benefits at various stages of this long-term project. Two online surveys were conducted in 2021 and 2022 among participants of LTAR engagement events at KBS, using a pre-post design, resulting in 125 total responses. Survey respondents had positive perceptions of the collaboratively designed research experiment. They had a strong expectation that the research would generate conservation and environmental advances while also informing policy and programs. Respondents also indicated a desire to network with other stakeholders. The research team noted the significant role of a long-term stakeholder engagement specialist in inviting participants from diverse backgrounds and creating an open and engaging experience. Overall, results highlight an interdisciplinary path of intentional and iterative engagement and evaluation to build a program that is adaptive and responsive to stakeholder needs.

Soil ecophysiology is adversely affected by various environmental hazards, particularly in mining regions. While there has been substantial research on the effects of coal, mica, copper (Cu), and manganese (Mn) mining on soil quality, the impact of bauxite mining operations on nearby soils has largely been overlooked in the literature. Therefore, this study aims to investigate how microbial activity and dynamics are influenced by soil stressors, such as acidity and heavy metals, in areas adjacent to active bauxite mines. Soil samples were collected from three adjacent locations of an active bauxite mine area at distances of <100 m (S1), 100-500 m (S2), and >500 m (S3). The samples contained chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), zinc (Zn), manganese (Mn), and cadmium (Cd), as well as elevated acidity and aluminum (Al). These conditions adversely affected the soil microbial indicators, including fluorescein diacetate (FDA), microbial biomass carbon (MBC), and enzyme activity. The highest concentrations of labile metals (i.e., water-soluble and exchangeable) were found in soil mixed with mining waste (S1), whereas acidity and Al were highest in sparsely vegetated soil (S3). Total acidity, total potential acidity, pH-dependent acidity, and Al were significantly positively correlated. Moreover, the significant positive correlation among organic carbon (OC), acidity, Al, and microbial properties (FDA, MBC, and microbial enzymes) suggests a potential effect of OC in mitigating acidity in S3. The ratios of microbial properties with OC depicted a significant negative correlation with acidity and Al fraction, denoting that acidity and Al posed a deleterious effect on soil microbial health. The similarity percentage analysis identified acid phosphatase as the key enzyme accounting for ∼78% of the observed differences in enzyme composition across the sites. Visual MINTEQ modeling revealed that the sites were saturated with different Al-bearing minerals. Pollution load index (PI) and the geo-accumulation index (I_geo) values identified the region as heavily contaminated (PI > 1). Finally, the health risk analysis revealed that Ni posed a potential carcinogenic risk for both adults and children.

Evaluating how weather, farm management, and soil conditions impact phosphorus (P) loss from agricultural sites is essential for improving our waterways in agricultural watersheds. In this study, rainfall characteristics, manure application timing, tillage, surface condition, and soil test phosphorus (STP) were analyzed to determine their effects on total phosphorus (TP) and dissolved phosphorus (DP) loss using 125 site-years of runoff data collected by the University of Wisconsin Discovery Farms and Discovery Farms Minnesota. Three linear mixed models (LMMs) were then used to evaluate the influence of those factors on TP and DP losses: (1) a model that included all runoff events, (2) manured sites only, and (3) precipitation events only. Results show that the timing of manure application relative to the timing of a runoff event only had a marginal association with P loads and concentrations, although the majority of the runoff events were collected after 10 days of manure application. Tillage was as influential factor, with greater DP loads and concentrations associated with no-till, especially during frozen conditions. Fields in this study had high STP values, but the model results only showed positive associations between DP load and DP flow-weighted mean concentration (FWMC) loss at the 0- to 15-cm depth. The precipitation event LMM (which included precipitation characteristics) was the model that resulted in the largest R² value. While the predictive capacity of the LMMs was low, they did illuminate the relative importance of management and environmental variables on P loss, and can be used to guide future research on P loss in this region.

Atmospheric nitrous oxide (N₂O) is a potent greenhouse gas, with long atmospheric residence time and a global warming potential 273 times higher than CO₂. N₂O emissions are mainly produced from soils and are influenced by biotic and abiotic factors that can be substantially altered by anthropogenic activities, such as land uses, especially when unmanaged natural ecosystems are replaced by croplands or other uses. In this study, we evaluated the spatial variability of N₂O emissions from croplands (maize, soybean, wheat, and sugar cane crops), paired with the natural grasslands or forests that they replaced across a wide environmental gradient in Argentina, and identified the key drivers governing the spatial variability of N₂O emissions using structural equation modeling. We conducted on-farm field measurements over 2 years at nine different sites, including a wide environmental gradient (mean rainfall from 679 to 1090 mm year^-1 and mean temperatures from 13.8°C to 21.3°C), with diverse plant species life forms, and ecosystems, from the Semiarid Chaco forests in the Northwest of Argentina to the Pampas grasslands in the Southeast. On average, agricultural systems emitted more than twice N₂O (+120%), had higher soil water content (+9%), higher soil temperatures (+3%), higher soil nitrate content (+19%) but lower ammonium (-33%) than natural ecosystems. We found that land use was the main driver of N₂O emissions by directly affecting soil NO₃ ^- contents in both natural ecosystems and croplands. Urgent management practices aimed at reducing N₂O emissions from croplands are needed to mitigate their contributions to global climate change.

Eastern North Carolina has been subjected to widespread water quality degradation for decades, notably throughout the Cape Fear River Watershed, owing largely to the magnitude of concentrated animal feeding operations (CAFOs) in the region. Long-term nutrient monitoring data from numerous locations throughout southeastern North Carolina have shown significantly elevated organic nitrogen (Org-N) concentrations starting around the year 2000-a concerning development, as labile Org-N can stimulate algal blooms and subsequent bacterial production, thus enhancing eutrophication in freshwater systems. By measuring the stable isotope signatures (δ¹³C, δ¹⁵N) of particulate organic matter sampled from a range of southeastern North Carolina waters, the predominant sources to the observed Org-N loadings were elucidated. Isotope data from across the Cape Fear River watershed indicated a large gradient of livestock waste-N contributions, with hog waste-N contributions consistently higher in the Northeast Cape Fear River watershed and with fertilizer-N contributions higher in the Black River watershed-findings that are consistent with each sub-basin's land usage. %N sediment content was positively correlated with hog waste-N contributions in the Black River watershed, indicating that sediments in CAFO-dense regions are reservoirs for agricultural nutrient pollution. Hog waste-N source contributions and %N sample contents for Black River sediments were strongly correlated with regional swine and poultry CAFO densities, establishing a strong connection between industrial animal production and stream sediment nutrient loads. Collectively, these findings suggest a major role of livestock waste, as well as human sewage, in driving the long-term Org-N increase in eastern North Carolina water bodies.

Ephemeral streams are important pollutant conduits, but the mechanisms that control nutrient transport to these systems remain unclear. In the US Virgin Islands (USVI), where most streams flow ephemerally, a lack of continuous hydrologic and water quality data limits our understanding of streamflow behavior and its influence on water quality. We therefore assessed the impact of soil moisture and hydrometeorological conditions on nitrogen (N) concentrations within an ephemeral stream on St. Croix, USVI. Stream N concentrations were usually highest during initial flow events, after prolonged dryness, and declined thereafter. Nitrogen increased with shallow antecedent soil moisture and rainfall intensity and decreased with deep soil moisture and baseflow emergence, indicating it was predominantly exported to the stream via surface runoff, as opposed to subsurface leaching. Our results are the first of their kind for the USVI and could be used to improve water quality of freshwater and marine systems.

Hydrologic alterations associated with urbanization can weaken connections between riparian zones, streams, and uplands, leading to negative effects on the ability of riparian zones to intercept pollutants carried by surface water runoff and groundwater flow such as nitrate (NO₃ ^-) and phosphate (PO₄ ^3-). We analyzed the monthly water table as an indicator of riparian connectivity, along with groundwater NO₃ ^- and PO₄ ^3- concentrations, at four riparian sites within and near the Gwynns Falls Watershed in Baltimore, MD, from 1998 to 2018. The sites included one forested reference site (Oregon Ridge), two suburban riparian sites (Glyndon and Gwynnbrook), and one urban riparian site (Cahill) with at least two locations and four monitoring wells, located 5 m from the center of the stream, at each site. Results show an increase in connectivity as indicated by shallower water tables at two of the four sites studied: Glyndon and Cahill. This change in connectivity was associated with decreases in NO₃ ^- at Glyndon and increases in PO₄ ^3- at Glyndon, Gwynnbrook, and Cahill. These changes are consistent with previous studies showing that shallower water table depths increase anaerobic conditions, which increase NO₃ ^- consumption by denitrification and decrease PO₄ ^3- retention. The absence of change in the forested reference site, where climate would be expected to be the key driver, suggests that other drivers, including best management practices and stream restoration projects, could be affecting riparian water tables at the two suburban sites and the one urban site. Further research into the mechanisms behind these changes and site-specific dynamics is needed.