Non-point Source Research Articles

Bioremediation of non-point hydrogen sulfide emissions using bacterial cellulose/activated carbon membrane

BackgroundHydrogen sulfide (H2S) gas, characterized by its low odor threshold and toxicity, poses significant challenges in non-point source odor management. Traditional biotechnologies are effective in removing malodorous gases from point sources but they are limited for non-point source odor control.ResultsIn this study, the sqr and pdo genes from Cupriavidus pinatubonensis JMP134 were introduced into the bacterial cellulose-producing strain Kosakonia oryzendophytica FY-07. This genetic modification enhanced the strain’s sulfur oxidation capacity, which increased over time, with an average transformation capacity of approximately 275 mg·L− 1·day− 1. By incorporating 1% activated carbon, an efficient, naturally degradable bio-composite membrane was developed, achieving a maximum H2S adsorption capacity of 7.3 g·m− 3·day− 1. FY-07 remained stable in soil and improved the microbial community for H2S treatment.ConclusionThe resulting bio-composite membrane is environment-friendly and efficient, making it suitable for emergency odor control in landfills. This study offers recommendations for using membrane materials in managing non-point hydrogen sulfide emissions.

Spatial–Temporal and Decoupling Effect of Agricultural Carbon Pollution Synergy in Ecologically Fragile Areas

As an important industry in ecologically fragile areas, the synergy of agricultural pollution control and carbon reduction is vital for the balanced development of industries and regional synergy. This paper aims to explore the synergistic result of agricultural pollution control and carbon reduction in ecologically fragile areas so as to clarify the weak links and solve carbon pollution in ecologically fragile areas. Leveraging the 2006–2021 municipal data of ecologically fragile areas, this paper calculates the coupling coordination degree (CCD) of agricultural non-point source pollution and agricultural carbon emission in ecologically fragile areas; calculates the decoupling relationship between agricultural carbon emissions, pollutants, and gross agricultural output based on the Tapio decoupling index; and quantitatively depicts the synergy of agricultural pollution control and carbon reduction in ecologically fragile areas. From 2006 to 2021, agricultural carbon emissions in ecologically fragile areas depicted a fluctuating and increasing trend. Agricultural non-point source pollution depicted an “inverted U-shaped” growth trend. The emission trends of agricultural carbon emissions and agricultural pollutants depict that although agricultural pollutants and carbon emissions are homologous, there is heterogeneity in the trend and change in emissions. The synergistic results of agricultural pollution control and carbon reduction show a fluctuating upward trend in ecologically fragile areas, and the coordination degree of ecologically fragile areas increased from 0.32 to 0.89, indicating that the level of coordinated development between agricultural pollution control and carbon reduction increased significantly. Taking into account the decoupling effect, the decoupling state of agricultural carbon pollution synergistic economic growth in ecologically fragile areas has changed from negative decoupling to strong decoupling to weak decoupling, mainly in the state of strong decoupling, negative decoupling of expansion, and weak decoupling; in addition, the synergistic capacity of agricultural pollution control and carbon reduction needs to be further optimized. Based on the research results, there is some room for improvement in agricultural carbon pollution synergy in ecologically fragile areas, and regions should strengthen regional cooperation.

Seasonal Distribution of Nutrient Salts and Microbial Communities in the Pearl River Delta

The transformations of iron (Fe), phosphorus (P), and sulfide (S) have been previously investigated in many areas, but quantifying the effects of the seasons on nutrient transformations and bacterial community distributions is a major issue that requires urgent attention in areas with serious anthropogenic disturbance. The authors used the diffusive gradients in thin films (DGTs) technique and 16S rRNA gene sequencing to determine the spatial heterogeneity in the nutrient distribution and bacterial community structure in the overlying water and sediment in the Pearl River Delta (PRD). Sampling campaigns were conducted in summer and winter. The results show that the nutrient salts exhibited greater differences in time than in space and there were higher water pollution levels in winter than in summer. During summer, the abundant non-point source pollution from the rainfall input provided a rich substrate for the bacteria in the water, leading to a strong competitiveness of the PAOs and nitrifying bacteria. Meanwhile, a high temperature was favorable for the exchange of elements at the SWI, with a greater release of P, Fe, and N, while, with the low temperatures and high DO and nutrient salts seen in winter, the SOB and denitrifying bacteria were active, which correctly indicated the high concentration of SO42− and NH4+-N in the water. The microbial diversity and abundance were also affected by the season, with a higher richness and diversity of the microbial communities in summer than in winter, and the high salinity and nutrient salt concentration had a significant inhibitory effect on the microorganisms. A Mantel test revealed that the spatiotemporal distribution patterns of the dominant bacteria were closely related to the TOC and DO levels and played an important role in the P, Fe, S, and N cycle. These observations are important for understanding the nutrient salt transformation and diffusion in the Pearl River Delta.

Estimation of non-point source of pollution loads in the River Song, a tributary of River Ganga, India.

The Himalayan rivers are particularly vulnerable to regional climate changes and anthropogenic influences, which can significantly alter both water quality and quantity, jeopardizing the fragile river ecosystems. This study investigates the hydrochemical characteristics of the Song River, a tributary of River Ganga focusing on non-point source (NPS) pollution, during the period June 2022 to November 2023. Monitoring of river discharge was carried out water samples were collected weekly during the monsoon (June to September), bi-weekly in the post-monsoon (October & November), and monthly during lean periods (December-May) from three monitoring stations. The study revealed that Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) eventually exceeded the criteria limits (3mg/L for BOD and 10mg/L for COD) prescribed by the Central Pollution Control Board (CPCB). The chemical composition of the river water at the monitoring stations revealed Ca2+and Mg2+ as the dominant cations, while HCO3⁻ and SO42⁻ were identified as the major anions. Gibbs plot suggesting the dominance of rock weathering as the major natural controlling mechanism of chemical composition in the basin. Carbonation and sulphide oxidation are two proton-producing reactions controlling the chemical weathering processes. C-ratio plot suggested that dominance of carbonate dissolution in the tributary Suswa, while Song River showed dominance of sulphide oxidation, particularly in its upstream region. Spatial and temporal analysis identified nutrient pollution (NO₃⁻, NH₄⁺, PO₄3⁻), organic loads (BOD, COD), and other parameters (TSS, Cl⁻) as key contributors to water quality deterioration at the monitoring stations. A chemical mass balance (CMB) approach based on mass conservation has been applied for estimating the NPS pollution loads on the Song River. CMB calculations carried out for major cations such as (Na+, K+, Ca2+, Mg2+, and NH4+) and major anions (Cl⁻, SO42⁻, HCO3⁻, NO3⁻, and PO43⁻) across a 21km stretch of the river, encompassing approximately 305 sq. km. and observed that the contribution of uncharacterised load was maximum in dry season and minimum during monsoon season. Seasonal variations in ion concentration and flux were strongly correlated with hydrological processes, highlighting the need for comprehensive monitoring and management of NPS pollution in the Song River to safeguard its water quality and downstream impacts on the Ganga River system.

Modelling phosphorus inputs and dynamics in a large tropical semiarid basin.

This study proposed a simple process-based model to predict total phosphorus (TP) inputs and dynamics in a large tropical semiarid basin in Brazil (19,015 km2), where the Castanhão dam, the largest non-hydropower reservoir in Latin America, is located. The model solved on a monthly basis the water balance and TP dynamics along the river system, considering complete mixing at the cross-section, steady-state regime, and a piston-type transport with first-order decay. Both primary and secondary data were used to validate the model, with deviations of up to about 20%. A linear increase in the flow rate along the river was observed, indicating that transmission gains were dominant. TP concentration increased with river flow rate and a consistent decay along the system was observed. TP from point sources (PS) was assumed constant. TP from non-point sources (NPS) decreased with time (R2 = 0.90) due to the continuous wash-off process. NPS was the dominant load, decreasing respectively from 99 to 61% of the total load from high to low flows. TP load varied from 1 to 141 ton/month, with an average of 34 ton/month. This resulted in an average TP yield of 21.2kgkm-2year-1, which is significantly lower than the national average due to the peculiarities of the region: lower precipitation, intermittent rivers, and high-density reservoir network. All the simulated TP values were above the mandatory limit of 0.05mg/L. PS reduction was only effective for relatively low flows, while NPS reduction was the most relevant remediation measure for both high and low flows. The impact of climate change on TP concentration also yielded TP > 0.05mg/L for all the projected scenarios, with the input loads to the Castanhão reservoir spanning from 23 to 266 ton/month. The proposed model can also be applied to other regions with different hydroclimatic conditions and land uses.

Seasonal variations in groundwater chemistry and quality and associated health risks from domestic wells and crucial constraints in the Pearl River Delta.

Groundwater quality is strongly compromised by polluted surface water recharge in rapidly developing urban regions. However, gaps still remain in the understanding of the critical contaminants controlling water quality and the health risks associated with groundwater consumption, particularly considering seasonal and climate changes in rainfall. This work focused on changes in groundwater quality and critical contaminants in domestic wells in the fast-developing Pearl River Delta (PRD) from the wet season to the dry season. The stable isotope δD and δ18O values indicated that groundwater was largely impacted by precipitation and has experienced strong evaporation. The groundwater generally exhibited oxidizing and slightly alkaline properties and was predominantly of the Ca-HCO3 type. Owing to the dominant water type of Ca-HCO3 and the high concentrations of Ca, concerns related to hard water arose, particularly during the wet season, which promotes the need for water softening before groundwater use. Although the heavy metal pollution index (HPI) and water quality index (WQI) indicated excellent or good water quality, 34% and 47% of the groundwater samples presented elevated concentrations of arsenic and nitrate, respectively, compared with the WHO recommended levels, and the contamination level was elevated during the dry season. To our knowledge, this study is the first to report the fluoride concentrations in the PRD groundwater, with median values below 0.5 mg L-1, underscoring the need for dietary fluoride supplementation. Health risk assessment confirmed the presence of both noncarcinogenic risks from arsenic and nitrate and cancer risk from arsenic in local populations resulting from groundwater consumption in the PRD region. This research emphasizes the importance of critical contaminants that constrain groundwater quality from different seasons with large variations in rainfall. Our work highlights the urgent need for the construction of adequate sanitation systems and for the control of agricultural nonpoint source pollution in rapidly urbanizing areas to safeguard both surface water and groundwater resources.

Toward Effective Monitoring of Diffuse VOC Emissions: A Critical Discussion and Review of the Applications of EN 17628:2022

The estimation and characterization of diffuse emissions of volatile organic compounds (VOCs) is a crucial issue for industry and environmental regulators. Compared to channelled ones, diffuse emissions derive from complex (non-point) sources, such as wastewater treatment plants, storage tanks, and process unit components. Such sources are typically influenced by dynamic factors such as operational activities and weather conditions. Therefore, this complexity makes the localization and quantification of diffuse VOC emissions a crucial challenge from a technical and regulatory perspective. Recently, the technical standard EN 17628:2022 has been published, which provides a framework to address this issue, proposing five different techniques for the localization, identification, and quantification of diffuse emissions. Nevertheless, while it represents a step forward in this field, the standard shows some shortcomings for a proper implementation, potentially causing divergent interpretations of the guidelines. The accuracy of the measurements is highly dependent on the configuration and morphology of the site, but especially on the meteorological data implemented to calculate the emitted flux. In addition, these techniques, despite being well-established, are particularly complex from both a technical–scientific and logistical–economic point of view. An emerging method, Quantitative Optical Gas Imaging (QOGI) appears to theoretically overcome some issues, but requires further studies to ensure accurate and reproducible quantification of emissions. This review aims to highlight the advantages, disadvantages, and potential developments of the various techniques described in the standard for the characterization of diffuse VOC emissions in the industrial sector.

Industrial Agriculture’s Influence on Recreation: The Need for a Relational Approach

Recent reviews of leisure and recreation literature have asserted a need to con-sider the relationship between ecosystem function and recreation at multiple spatial scales. One way socio-ecological interactions across a regional landscape impact recreation are through the industrialization of agricultural practices. Little research has examined how the industrialization of agriculture, mainly through confined animal feeding and the intensification of monocultural row crop farming, has impacted recreational opportunities in locations such as the Upper Midwest of the United States. While beach closures and fish kills attributed to non-point source pollution are glaring examples, it is likely that the relationship between industrialized agriculture and recreational opportunities is not fully understood. It is increasingly evident that a fundamental transformation of socio-ecological systems will be necessary to adapt to our changing climate and community needs. Recreation and leisure studies could play a critical role in shaping the conversation and assessing the impacts of these socio-ecological transitions.

Meta‐Analysis of Urban Non‐Point Source Pollution From Road and Roof Runoff Across China

AbstractUrban non‐point source (NPS) pollution has become an important issue affecting water quality, but current research has focused mainly on local scales and has lacked systematic evaluations at large spatial scales. Here, a meta‐analysis was conducted to explore the characteristics of runoff pollution indicators (TSS: total suspended solids, TN: total nitrogen, TP: total phosphorus, and COD: chemical oxygen demand) on the roads and roofs in 41 Chinese cities, and a boosted regression tree model was used to reveal the geographical differences in pollution levels and the contribution rates of their influencing factors. The results revealed that the average event mean concentrations (EMCs) of TSS (326 mg/L), TP (0.6 mg/L), and COD (160 mg/L) were significantly greater in road runoff than in roof runoff. Among them, the TSS concentrations were nearly four times greater than those in roof runoff, whereas the TP and COD concentrations were 3.2 and 2.3 times greater, respectively. Urban NPS pollution is severe in China, and the concentrations of runoff pollutants far exceed those in the USA, Germany, and France. There were significant geographical differences in urban NPS pollution due to the influences of air quality (35% relative contribution), climate conditions (15%), and human activities (45%). Prominent pollution from road runoff was observed in the Central region, more severe pollution from roof runoff was observed in the Northern region, and relatively light pollution was observed in the Southern and North‐Eastern regions. This study provides the first synthesis of NPS road and roof runoff pollution levels in Chinese cities on a large spatial scale, resulting in scientific guidance for urban stormwater management and NPS pollution control.

How efficient are pre-dams as reservoir guardians? A long-term study on nutrient retention

Assessing nutrient loading and processing is crucial for water quality management in lakes and reservoirs. Quantifying and reducing external nutrient inputs in these systems remains a significant challenge. The difficulty arises from low monitoring frequencies of the highly dynamic external inputs and the limited availability of measures to reduce diffuse source loading. One option for the latter is the use of pre-dams, i.e. small impoundments at the inflow points into reservoirs, designed to retain nutrients by algal uptake and sedimentation. This study analyzes long-term (ranging from 8 to 21 years) nutrient and discharge time series for nine German pre-dams to assess their retention capacity. For that, we (i) quantified nutrient loading using four different mathematical methods, (ii) derived their retention efficiencies, and (iii) identified environmental factors determining the retention of Nitrogen (N), Phosphorus (P), and Silica (Si). We show that retention of soluble reactive phosphorus (SRP) (43.6%) and total phosphorus (TP) (39.9%) is far higher than for nitrate (NO3) (15.3%) and Si (15.9%). Retention efficiency for SRP and TP was higher during the warm seasons because of higher algal nutrient uptake and thus higher nutrient sedimentation. Mixed effects models documented a significant positive effect of the pre-dams’ hydraulic residence time (HRT) on retention efficiency. Pre-dams provide substantial service in retaining nutrients and help to protect downstream waterbodies from nutrient inputs. They provide effective measures for trapping nutrients including those originating from non-point sources.

Developing a real-time water quality simulation toolbox using machine learning and application programming interface.

Developing a real-time water quality simulation toolbox using machine learning and application programming interface.

Aquatic occurrence, fate and potential ecotoxicity of insecticide and fungicide residues originating from a biofuels production facility using pesticide-treated seeds.

Aquatic occurrence, fate and potential ecotoxicity of insecticide and fungicide residues originating from a biofuels production facility using pesticide-treated seeds.

Identifying critical riparian zones for eco-environmental management of the Yangtze River through pollution mapping.

Identifying critical riparian zones for eco-environmental management of the Yangtze River through pollution mapping.

Effects of polyculture on nutrient removal from residential raw sewage using field-scale artificial floating islands.

Effects of polyculture on nutrient removal from residential raw sewage using field-scale artificial floating islands.

Study on the Estimating the Contribution Rate of Livestock-Induced Pollution in River Basins using Correlation Coefficients by Branch

The recent expansion of livestock farming has significantly increased livestock wastewater discharge, which contains a higher pollutant load compared to other wastewater sources and poses a serious threat to river water quality. This study quantitatively evaluates the impact of livestock wastewater on river water quality and proposes optimal management measures. The Hwanggujicheon watershed in Gyeonggi Province was selected as the study area, with the main river stretch defined from the upstream micro-watershed endpoint (Q0) to the downstream micro-watershed endpoint (Q1). Additionally, four sub-watersheds—BJ (Q2), SM (Q3), G (Q4), and HG (Q5)—were analyzed. To evaluate pollution contributions, statistical methods were employed to assess the influence of upstream pollutant loads on Q1. Livestock non-point source pollution contributions were estimated based on livestock status survey data and national pollution source survey data, following the guidelines for total water pollution load management. The results revealed that the Galcheon (Q4) sub-watershed had the most significant impact on river water quality, with livestock pollution contributing 1.851%, 11.85%, and 7.20% to total nitrogen (T-N), total phosphorus (T-P), and biological oxygen demand (BOD), respectively. These findings confirm that statistical contribution analysis is an effective tool for quantitatively evaluate the impact of livestock-related pollution on river water quality. Furthermore, the alignment of the statistical analysis with field survey data validates this approach as a reliable scientific analysis method. Effective management of major pollution sources, such as the Galcheon (Q4) sub-watershed, is crucial in improving downstream water quality. This study provides a scientific foundation in developing livestock-related pollution management and non-point source pollution control policies. By quantitatively identifying the contribution of livestock-related pollution sources to river water quality through advanced statistical methods, the findings emphasize the importance of systematic management in preserving river ecosystems and promoting sustainable watershed management. Moreover, the study offers practical insights in formulating effective water quality improvement strategies.

Agricultural Non-Point Source Pollution: Comprehensive Analysis of Sources and Assessment Methods

Agricultural Non-Point Source Pollution: Comprehensive Analysis of Sources and Assessment Methods

GIS and AHP-based methods for river risk zone (RRZ) assessment: a case study of the Himalayan rivers in Doon Valley, Uttarakhand, India.

Pollution from both point and non-point sources, over-extraction of freshwater, and significant climatic changes in recent years are some factors that put substantial pressure on worldwide water resources. As the demand for potable water increases globally for human, agricultural, and industrial uses, the need to evaluate the river risk assessment also increases. GIS-based studies in recent years have gained prominence as they are rapid, cheap, and provide insight into the resources for further development of research on the rivers. Therefore, the present study assessed the river risk zone (RRZ) of the Himalayan rivers in the Doon Valley of Uttarakhand in India. A combination of GIS and analytical hierarchical process (AHP) techniques was used in the present study. A total of 15 thematic layers, total dissolved solids (TDS), conductivity, pH, salinity, temperature, depth, drainage density, land use/land cover (LULC), elevation, slope, flow, width, soil type, geology, and aspect, were prepared and studied from primary survey data and open-source digital elevation model (DEM) and satellite imagery for RRZ evaluation. Weights assigned to each class are based on their characteristics and risk towards the river through the AHP method. The RRZ map thus obtained was categorized into five classes: very high, high, medium, low, and very low. The study reveals that about 56.38% of the river area is covered under high and very high-risk zones. The medium, low, and very low-risk zones are observed in 33.71%, 2.93% and 6.98%, respectively. Identifying and monitoring these risk zones give planners and decision-makers opportunities to intervene where it counts most to prevent further degradation or collapse systematically, thus preserving the health and sustainability of river systems over time.

Back to chromite as a mineralogical strategy for long-term chromium pollution control

Re-oxidation of Cr(III) in treated Cr-contaminated sites poses a considerable source of Cr(VI) pollution, necessitating stable treatment solutions for long-term control. This study explores the immobilization of Cr(VI) into chromite, the most stable and weathering-resistant Cr-bearing mineral, under ambient conditions. Batch experiments demonstrate chromite formation at pH above 7 and Fe(III)/Cr(III) ratios exceeding 1, with Fe(III) occupying all tetrahedral sites, essential for stability. A theoretical model is developed to evaluate the effects of pH and Fe(III)/Cr(III) ratios on chromite crystallinity, resulting in AI4Min-Cr, a publicly accessible platform offering real-time intelligent remediation strategies. To tackle the complexities of non-point source Cr pollution, we employ microbial methods to regulate on-site Eh and pH, optimizing chromite precipitation. Long-term stability tests confirm that chromite remained stable for over 180 days, with potential for magnetic separation recovery. This study presents a mineralogical strategy to address re-oxidation and Cr resource recovery in Cr-contaminated water and soil.

Quantifying variation of non-point source pollution and its impact factors: A study of Nansi Lake Basin.

Agricultural non-point source (NPS) pollution directly affects the quality of soil and water, ecological balance and human health, and is a key challenge to achieve sustainable environmental development and efficient resource management. Taking the Nansi Lake Basin (NLB) as the study area, this study explores the main sources of agricultural NPS pollution and its influencing factors, aiming to provide scientific basis for the management of water resources in the basin. Current studies usually use the runoff pollution partitioning method to estimate agricultural NPS pollution loads in runoff, but the accuracy of the analyses is limited by the incompleteness of water quality monitoring data, especially the lack of complete runoff records in some years. To compensate for this deficiency, this study simulated the river runoff based on the Long-Term Hydrological Impact Assessment (L-THIA) model, and applied the simulation results to the quantitative calculation of agricultural NPS pollution loads after verifying the model reliability through accuracy calibration. Based on L-THIA model, the spatial and temporal distribution data of agricultural NPS pollution in the basin from 2010 to 2020 were obtained, the distribution characteristics of chemical oxygen demand (COD) and ammonia nitrogen (NH3-N) were quantitatively assessed, and the impacts of natural and socio-economic factors on them were analyzed. A regression model was developed to simulate future agricultural NPS pollution through multiple regression analysis. The results showed that the total agricultural NPS pollution in the NLB showed an increasing trend during the study period. In particular, among the socio-economic factors, COD and NH3-N were significantly correlated with fertilizer application, pesticide use, rural employment and total population. Among the natural factors, topographic index, watershed area and gully density were positively correlated with pollutants, while slope and soil organic matter were negatively correlated. The results of this study raise awareness of the contribution of influencing factors and allow researchers and planners to focus on the most important NPS pollution sources and influencing factors. The study provides an important reference for the prevention and control of agricultural NPS pollution in the NLB, which is of great practical importance.

Simulating Nonpoint Source Pollution Impacts in Groundwater: Three-Dimensional Advection–Dispersion Versus Quasi-3D Streamline Transport Approach

Numerical models are commonly used to support the management of diffuse pollution sources in large agricultural landscapes. This paper investigates the suitability of a three-dimensional groundwater streamline-based nonpoint source (NPS) assessment tool for agricultural aquifers. The streamline approach is built on the assumption of steady-state groundwater flow and neglects the effect of transverse dispersion but offers considerable computational efficiency. To test the practical applicability of these assumptions, two groundwater transport models were developed using the standard three-dimensional advection–dispersion equation (ADE): one with steady-state flow and the other with transient flow conditions. The streamline approach was compared with both ADE models, under various nitrate management practice scenarios. The results show that the streamline approach predictions are comparable to the steady-state ADE, but both steady-state methods tend to overestimate the concentrations across wells by up to 10% compared to the transient ADE. The prediction of long-term attenuation of nitrate under alternative land management scenarios is identical between the streamline and the transient ADE results.