Pesticide fate at watershed scale: A new framework integrating multimedia behavior with hydrological processes

Pesticide and methylmercury fluxes to a marine protected region of Australia influenced by agricultural expansion

Estuarine environments provide diverse ecological services, including carbon burial and the sequestration of pollutants. Yet, urban expansion and anthropogenic activities can impact the ability of estuarine systems to retain and store pollutants, with unknown consequences for marine communities. Here, we present dated sediment cores from within the Solitarily Island Marine Park, a marine life sanctuary in Australia subject to runoff from a highly impacted catchment. We reveal historical accumulation rates of trace metals and pesticides likely associated with specific types of agricultural activities, including banana and blueberry production. Propiconazole and tebuconazole, fungicides highly reactive in marine habitats, were recorded in the sediment profile located at the site nearest the freshwater source. Furthermore, mercury content revealed elevated levels in the most recent sediments, up to 0.13 mg kg-1 in 1999, while methylmercury (MeHg) was detected ranging from 0.1 mg kg-1 in 2017 to 0.2 mg kg-1 in more recent sediments. Additionally, arsenic accumulation rates are shown here to have significantly increased from 19.1 mg m-2 year-1 in 1930 to 259.6 mg m-2 year-1 in 2020. These substances were found to be related to organic matter which was determined to be mostly of terrestrially derived sources, probably related to historical catchment deforestation, as indicated through δ13C and C:N molar ratios. This study highlights the importance in monitoring and evaluating agriculture-derived pollutant discharge to protected coastal regions and provides an initial dataset that may be used to monitor pollutant runoff in catchments impacted by expanding agricultural activities throughout Australia, and around the globe.

Quantifying leachate discharge and assessing environmental risks of gully-type coal-based solid waste dumps in small watersheds: A refined hydrological modeling approach for mitigation strategies

Rainfall-induced leaching from extensive coal-based solid waste storage results in a long-term risk to watershed's water quality and safety. The leachate carries heavy metals and other contaminants, which migrate and accumulate through the watershed, leading to a persistent deterioration of downstream water environment. However, the lack of systematic research on the release, accumulation, and spatial-scale migration dynamics of leachate limits effective management of diffused leachate pollutions. This study presents a novel cross-scale coupling framework which integrates multi-source remote sensing data with Soil and Water Assessment Tool (SWAT) model, employing a strategy that transfers parameters from large basins to accurately quantify the hydrological processes in coal waste sub-basins. Additionally, a comprehensive analysis is performed on the hydrological characteristics, leachate generation, and watershed migration dynamics in gangue dump sub-watersheds, providing a new methodological framework for managing mining-related leachate pollution. The large basin model demonstrated strong performance (R² = 0.79, NSE = 0.66 for calibration; R² = 0.74, NSE = 0.59 for verification), while the sub-basin model exhibited excellent accuracy (R² = 0.94, NSE = 0.92 for calibration; R² = 0.81, NSE = 0.77 for verification). High-resolution drone data estimated the annual leachate production to be 3366.87 m³. Simulations revealed that leachate migration peaks in the summer months (July to September), significantly increasing downstream pollution risks. Risk assessments indicate that vegetation in land restoration areas reduces leachate production and migration via evapotranspiration and other processes. This study provides an adaptable methodological framework for managing mining-related leachate pollution and highlights the critical importance of optimal reclamation strategies for mitigating pollution and restoring degraded landscapes.

Integrative modeling of POPs output flux from soil at a regional scale: A comprehensive approach

Plot-scale natural attenuation models provide valuable insights into localized pollutant behavior but struggle to account for regional-scale hydrological processes. Existing research has predominantly concentrated on single processes, lacking comprehensive models to describe the output flux of persistent organic pollutants (POPs) by transport and transformation from soil at a regional scale. To address this gap, a model was developed by combining natural attenuation processes (e.g., degradation, volatilization, plant uptake) with hydrological transport processes (e.g., leaching, water washout, sediment transport). The model was validated using data from a petrochemical area in China and compared with the previous model (mass balance and neural networks model) to assess pollutant output flux. Results indicated that water washout was the dominant output pathway from soil for both Phenanthrene (Phe) (94.67 %) and Benzo(a)pyrene (BaP) (98.33 %). Phe exhibited a broader output flux range (0-67.8 mg∙m-2∙a-1) compared to BaP (0-12.9 mg∙m-2∙a-1), due to its higher volatility and solubility. Performance evaluation through 10-fold cross-validation yielded coefficient of determination (R2) values greater than 0.7 and root mean square error (RMSE) below 3 %, outperforming the previous model. Sensitivity analysis revealed that the soil organic carbon mass fraction (foc) was the most influential parameter at both a plot and regional scale. This study fills a gap in environmental research by providing a comprehensive model for accurate estimates of POPs output fluxes from soil.

Spatiotemporal distribution and inter-media transfer of polycyclic aromatic hydrocarbons in Shanghai, China: Historical patterns and future trends

Polycyclic Aromatic Hydrocarbons (PAHs) represent pervasive pollutants, posing health risks in urban environments. It is essential to comprehend the spatiotemporal distributions, composition profiles, and inter-media transfer processes of PAHs in various environmental compartments, influenced by both natural changes and anthropogenic activities. This study integrates historical and future spatiotemporally changing environmental parameters, including climate data, GDP, population data, land-use types, and hydrological variables, into the Multimedia Urban Model (MUM). This integration enables the simulation of spatiotemporal distributions and inter-media transfer fluxes of PAHs among six different media from the 2010s to the 2100s under two distinct Shared Socio-economic Pathways (SSP) scenarios in the megacity of Shanghai, China. The MUM model, featuring diverse gridded parameters, effectively captures PAH concentrations and movement across environmental compartments. Results indicate a decreasing trend in PAHs concentrations in the 2100s compared to the 2010s, with PAH concentrations in water, sediment, vegetation, and organic film covering impermeable surfaces under the SSP3-7.0 scenario higher than those of the SSP1-2.6 scenario. Low molecular weight PAHs dominate in the sediment, water, and air, whereas high molecular weight PAHs prevail in the organic film, vegetation, and soil. Sediment and soil serve as the predominant sinks for PAHs. The primary transport processes for PAH movement include air-film, air-soil, film-water, soil-air, and water-air. Almost all transfer fluxes exhibit a declining trend in future periods except for the air-film transport pathway. The principal input and removal routes for PAHs in Shanghai involve the advection of air and water. The study provides essential insights into the environmental behavior of PAHs and informs targeted pollution control in Shanghai. Additionally, it serves as a technical reference for similar pollution prediction research.

Comprehensive evaluation of antibiotics pollution the Yangtze River basin, China: Emission, multimedia fate and risk assessment

Antibiotics have attracted global attention because of their potential ecological and health risks. The emission, multimedia fate and risk of 18 selected antibiotics in the entire Yangtze River basin were evaluated by using a level Ⅳ fugacity model. High antibiotic emissions were found in the middle and lower reaches of the Yangtze River basin. The total antibiotic emissions in the Yangtze River basin exceeded 1600 tons per year between 2013 and 2021. The spatial distribution of antibiotics concentration was the upper Yangtze River > middle Yangtze River > lower Yangtze River, which is positively correlated with animal husbandry size in the basin. Temperature and precipitation increases may decrease the antibiotic concentrations in the environment. Transfer fluxes showed that source emission inputs, advection processes, and degradation fluxes contributed more to the total input and output. High ecological risks in the water environment were found in 2018, 2019, 2020, and 2021. The comprehensive health risk assessment through drinking water and fish consumption routes showed that a small part of the Yangtze River basin is at medium risk, and children have a relatively high degree of health risk. This study provides a scientific basis for the pollution control of antibiotics at the basin scale.

Sustainable governance of drinking water conservation areas based on adaptive thresholds

Drinking water quality is integral to the Sustainable Development Goals framework. At the present, China's drinking water conservation faces a number of challenges that are partially brought on by strict conservation measures that don't fully take into account human-land conflict and sustainable development. Taking the idea of adaptive governance, this study seeks to identify adaptive thresholds and adaptive solutions for compatible drinking water conservation and local development. Pressure and resistance to drinking water quality in its status, future potential, and adaptive thresholds were explored to identify sustainable governance for the Baimei Conservation Area, Fujian Province. Field research, local governance forums, and the Soil and Water Assessment Tool (SWAT) model were utilized to explore the drinking water quality pressure and resistance to drinking water quality. In order to uncover potential future changes in pressure and resistance, suitability analyses and multi-scenario simulations were used to examine the status quo, pressure, and resistance scenarios. Adaptive thresholds were then identified through SWAT modeling of each scenario to guarantee the drinking water quality is greater than Class II in the Core Conservation Area and Class Ⅲ in 2nd-grade Conservation Area, respectively. The research finds that construction land development and farming are the key pressures on drinking water quality, and forests and wetlands are the primary resistances. The expansion of construction lands and the increased wetlands was centered on potential future scenarios because farming has no room for growth and forests are already heavily covered. The adaptive threshold of construction land expansion is identified to be 10% without new wetlands but can be 20% by adding 10% wetlands in subbasins, 5, 8, and 9. This study confirms the potential of adaptive sustainability for drinking water conservation areas. A similar analysis procedure can also be adapted to enhance adaptive governance for the sustainability of other conservation areas nationally and globally.