Non-point Source Contamination Research Articles

Advances in chemical and microbial source tracking (MST) of fecal pollution in coastal waters: a review.

Coastal waters are the ultimate destination for both point and non-point sources of contamination. The uncontrolled dicharge of fecal waste into the ocean harms natural resources, marine life, and poses health risks to humans. Regular monitoring of coastal water quality and source tracking is important to prevent disease outbreaks. This review discusses all the fecal source tracking (FST) methods, ranging from traditional enumeration techniques to recent next-generation sequencing approaches, in the light of application on coastal waters. The advantages and disadvantages of the individual markers, method comparisons based on performance, correlation of marker with fecal indicator bacteria, and stability under waste water treatment and in field applications are mainly focused on enlightening the "tool box" approach for the marine environment.

Spatial-Temporal Characteristics and Driving Factors of Surface Water Quality in the Jing River Basin of the Loess Plateau

Water quality safety in the water source constitutes a crucial guarantee for public health and the ecological environment. This study undertakes a comprehensive assessment of the water quality conditions within the Jing River Basin of the Loess Plateau, emphasizing the spatial and temporal characteristics, as well as the determinants influencing surface water quality in the Shaanxi section. We utilized data from seven monitoring stations collected between 2016 and 2022, employing an enhanced comprehensive Water Quality Index (WQI) method, redundancy analysis (RDA), and Spearman’s correlation analysis. The results show that the average annual WQI value of the water quality of the Shaanxi section of the Jing River increased from 68.01 in 2016 to 76.18 in 2022, and the river’s water quality has gradually improved, with a significant improvement beginning in 2018, and a series of water quality management policies implemented by Shaanxi Province is the primary reason for the improvement. The river’s water quality has deteriorated slightly in recent years, necessitating stricter supervision of the coal mining industry in the upper section. The river has an average WQI value of 73.70 and is rated as ‘good’. The main pollution indicators influencing the river’s water quality are CODMn, COD, BOD5, NH3-N, and TP. From the upstream to the downstream, the water quality of the river shows a pattern of increasing and then decreasing, among which S4 (Linjing Bridge in Taiping Town) and S5 (Jinghe Bridge) have the best water quality. The downstream part (S6, S7) of the Jing River near the Weihe River has poor water quality, which is mostly caused by nonpoint source contamination from livestock and poultry rearing, agricultural activities, and sewage discharge. Redundancy analysis revealed that the spatial scale of the 2500 m buffer zone best explained water quality changes, and the amount of bare land and arable land in land use categories was the key influencing factor of river water quality.

An Innovative GIS-Based Policy Approach to Stream Water Quality and Ecological Risk Assessment in Mediterranean Regions: The Case of Crete, Greece

Due to the multiple pressures from human activities, many freshwater ecosystems are facing degradation. To address this issue, a new approach for assessing stream water quality and ecological (WQE) risk using a multi-criteria analysis through a GIS-based policy tool has been developed. The suggested methodology integrates eight different factors along the contaminant pathway from source to streams, including: (a) rainfall variability, (b) soil texture, (c) soil erodibility, (d) slope, (e) river buffer zone, (f) point source contamination buffer zone, (g) non-point source contamination of NO3, and (h) non-point source contamination of PO4. Utilizing fuzzy GIS tools, the above factors and their related maps were spatially overlaid (raster-based suitability for raster reclassification) to obtain the final stream WQE risk map. The final map depicts the spatial distribution of streams concerning their water quality risk and is represented by two classes of WQE risk. The first class is characterized as “appropriate”, in which there is no need for any further actions, while the other one is characterized as “non-appropriate”, indicating that actions should be taken to ensure the sustainability of streams’ water quality. The proposed approach was implemented for the island of Crete, which is located in the Southeast Mediterranean region. The developed methodology was validated using the Hellenic evaluation system (HESY2), an especially established and adapted to the Mediterranean river systems ecological quality metric method, obtained by in situ measurements that were conducted during different monitoring programs (1989–2015). Moreover, this study summarizes appropriate measures and practices that ensure the sustainable management of Mediterranean river basins. These practices can be adopted by local authorities, owners of polluting units, and farmers/breeders to improve the resiliency of streams’ water quality issues in the Mediterranean region.

RETRACTED: Assessing nonpoint source pollution risk in watersheds using a water-functioning zone approach

A thorough understanding of the geographical and spatial attributes of nonpoint source pollution risk in watersheds is crucial for conducting nonpoint source pollutant studies and implementing effective scientific administration strategies. The inclusion of a water-related functioning zone was considered during the nonpoint source's pollution risks assessment procedure. Nevertheless, there has not been a thorough investigation into the potential risk of nonpoint sources of pollution to adequately safeguard the quality of water in watersheds having varying capacities to handle contaminants in the water. This research presents an innovative approach for assessing the risk of nonpoint sources contamination. This allows for a quantitative evaluation of the effect of discharges of pollution from a sub-catchment on the quality of water bodies nearby. The nonpoint source losses of nutrients process, as modeled by the Water and Soil Assessment Tool, had been used to assess the hazard of nonpoint source contamination in Le ‘a River Watersheds. This assessment happened on both yearly and monthly scales. The findings indicated that the risk of nonpoint source contamination exhibits both seasonal and regional variations and is significantly impacted by the ability of the fluid ecosystem. Elevated nonpoint sources pollutants do not always equate to elevated pollutant dangers. On the other hand, a small amount of nutrients in the nonpoint sources does not indicate an insignificant degree of susceptibility to region risk. Furthermore, by utilizing a risk assessment method that considers the capacity of the water's environment, it is possible to identify variations in risk levels that may be overlooked when solely considering nonpoint sources contaminant losses, and fluid functioning zone. This approach allows for precise regulation of nonpoint sources of pollution administration.

Effects of agriculture and urbanization on the geochemistry of the Scioto River, Ohio

Despite efforts to reduce nonpoint source contamination of water resources, agriculture and urbanization remain primary sources that impair surface water quality. The Scioto River in Ohio, USA has headwaters in land dominated by primarily row-crop agriculture, then flows through metropolitan Columbus, the 14th largest city in the U.S. The river serves as a major drinking water source for the city and is dammed to form two reservoirs. The Scioto River was sampled for major ions, nutrients, and select trace elements weekly to monthly at five locations along changing agricultural and urban land use. Dissolved concentrations of many analytes were highest at the most upstream agricultural location, decreased to downtown Columbus, and increased at the location furthest downstream in agricultural land. The same trend was observed in discharge-weighted yields. Because much of the study area is underlain by carbonate bedrock, correlations with Ca2+ were likely to indicate a primarily geogenic source of the solute. Elements with moderate to strong positive correlations with Ca2+ included SO42−, Ni2+, Rb+, Mo6+, and Ba2+. Inorganic N species, emanating primarily from an agricultural source, had negative relationships with Ca2+. Concentration-discharge relationships revealed chemostatic to weak dilution of analytes positively correlated with Ca2+, suggesting a geogenic source of these elements that was weakly diluted with increasing discharge. Cu2+ showed a positive concentration-discharge slope, suggesting an anthropogenic input, but a defined source was not identified. Dams on the Scioto River that form drinking water reservoirs dampened chemical correlations and concentration-discharge relationships. Both agricultural and urban sources influence the river's chemistry based on hydroclimatic conditions and land use. Higher frequency sampling of the Scioto River during high flows allowed for a more nuanced understanding of sources of solutes to the river compared to previous work. Continued water quality monitoring is imperative to maintain and protect water quality resources, especially as urban populations are predicted to grow significantly in the next century.

Yield, Quality, and Nitrogen Leaching of Open-Field Tomato in Response to Different Nitrogen Application Measures in Northwestern China.

The overuse of fertilizers in open-field tomato leads to soil deterioration through nutrient leaching and increases the risk of agricultural non-point source contamination. Currently, the combined effects of different fertilization methods on soil nitrogen leaching and tomato production are still unclear. Therefore, the most effective fertilization method for open-field tomato should be discovered by examining how different fertilization methods affected tomato yield and quality, nitrogen use efficiency (NUE), and soil nitrogen leaching. Compared with CK (no fertilization), fertilization significantly increased the yield, total sugar (TS), total soluble solids (TSS), and vitamin C (vC) contents of fruits (p < 0.05), and OPT (optimal fertilization, controlled release nitrogen application, 240 kg ha-1) had the largest effect on increasing yield, quality, and net profit. However, when the fertilizer application rate reached 375 kg ha-1, these indices decreased. Nitrogen leaching concentrations, leaching amount, and titratable acids (TAs) increased with increased nitrogen application rates. Compared with other treatments, OPT reduced the total leaching amounts of total nitrogen (TN), nitrate nitrogen (NO3--N), and ammonia nitrogen (NH4+-N) by 30.09-51.79%, 24.89-50.03%, and 30-65%, respectively. Principal component analysis (PCA) showed that OPT achieved the highest overall score in terms of yield, quality, and nitrogen leaching conditions. The partial least squares path modeling (PLS-PM) further reveals that applications of high amounts of nitorigen have a positive effect on soil nitrogen leaching. The amount of nitrogen leaching vegetatively affects tomato yield and quality, while plant uptake of nitrogen positively affects tomato production. These findings confirm the importance of using controlled-release fertilizers and reducing nitrogen inputs to control nitrogen leaching and enhance open-field tomato yields.

Transport, dispersion, and degradation of nonpoint source contaminants during flood‐managed aquifer recharge

AbstractIn water‐stressed regions of the world, the inundation of working landscapes to replenish aquifers—known as flood‐managed aquifer recharge (flood‐MAR)—has become a valuable tool for sustainable groundwater management. Due to their diverse land use histories, however, many potential recharge sites host nonpoint source contaminants (such as salts, pesticides, and fertilizers) within the vadose zone that may flush to groundwater during recharge operations. To identify the controls on contaminant migration, we perform stochastic simulations of flood‐MAR through a heterogeneous alluvial aquifer and apply transient particle tracking to evaluate conservative and reactive contaminant transport over 80 years of recharge operations. With semi‐annual recharge events, the water table begins to rise 0.13–1.84 years after the first inundation event while solutes take much longer (11 to 80 years) to transit the 45‐m thick unsaturated zone. We derive a parametric expression for the ratio of celerity (or rate of pressure transmission) to velocity of the flood‐MAR wetting front and show that this simplified expression agrees with values calculated from heterogeneous model simulations. Slow solute velocities (0.25–1.75 m year−1) allow for significant contaminant removal through denitrification, but the contaminant plume experiences minimal dispersion or dilution over this time, reaching the water table as a sharp front. Our results suggest that minimizing groundwater velocity and maximizing groundwater celerity during flood‐MAR should optimize increases in water supply while limiting water quality degradation.

Sulfur Signature of a Mediterranean Wetland: The Case of Soils of the Inundated Floodplain Area at the Tablas de Daimiel National Park

In the Mediterranean region, numerous wetlands co-exist with competitive agricultural systems. Although wetlands’ hydrology (in water volume, source, and residence time terms) plays a major factor in their ecosystem structure, many of these wetlands have been subjected to different degradation processes. One such case is the Tablas de Daimiel National Park (TDNP), which witnesses one of its most environmentally sensitive times. In this context, scarce information is available on the sulfur (S) contents in this wetland. To diagnose this wetland’s degradation status, 43 soil samples were selected and analyzed to investigate S contents in the surface soils (0 to 30 cm) of the inundated floodplain area of the TDNP. They represent different degrees of exposure to pollutants and exposure to flooding. Sulfur determination was carried out by X-ray fluorescence. The S contents in the area range between 1.85 and 37.15 g kg−1, with a mean value of 13.71 g kg−1, which implies marked variability throughout this wetland. The highest values were observed near the wetland entrance via the Gigüela River, while the lowest ones appeared at its exit, with a relatively uniform gradient from the entrance to the exit. The relatively high S concentrations observed at sites other than the wetland entrance can be probably related to the continuous non-point source contamination with P, N, and S fertilizer applications, via runoff agricultural production systems. The results of this study are essential for understanding and predicting total S variability within the TDNP (Spain), which can interfere with soil management practices.

Characterisation of storm runoff contamination from a tropical urban residential area in Malaysia

It has been quite a long time since the Malaysian government endorsed the Urban Storm Water Management Manual (USWMM) in 2000. Until now, there is no proper and detailed database on the non-point source contamination characteristics from various land uses in tropical regions of Malaysia. As such this study was conducted to fill part of the information gap pertaining to the nature of runoff quality in the tropical regions. The combined sewer outfall of a 6.14 ha residential area in Malaysia was studied to characterise the urban runoff quality generated due to tropical rain. As the drainage outlet discharges sullage and storm runoff through the same drainage network, hourly flow pattern and contaminant concentrations were determined both for sullage and storm runoff. Basic statistical analysis was conducted to determine the mean, standard deviation and event mean concentration values for the study area, for which such data was not available. It was observed that the runoff generated from the area is polluted due to high total suspended solids (TSS), biochemical oxygen demand (BOD) and chemical oxygen demand (COD). The runoff contained more total organic carbon (TOC) than total inorganic carbon (TIC). The EMC values of BOD, COD, TSS, TOC, total Kjeldhal nitrogen, ammoniacal nitrogen and orthophosphate were 35, 168, 177, 11, 0.32, 0.54, 0.16 mg/L, respectively. The presence of heavy metals in the runoff was low. The EMC values of lead, zinc, nickel, cadmium, chromium and copper were 0.061, 0.358, 0.002, 0.002, 0.025 and 0.022 mg/L, respectively. Due to the high quantity of rainfall, a significant amount of annual contamination loading is generated from the nonpoint sources of the residential area.

Differentiating between point and non-point source nutrient loadings of wastewater in an agriculturally impacted area using a hybrid statistical model

Nutrient contamination from point and non-point sources can lead to harmful consequences, such as algal blooms. Point and non-point nutrient loading estimation is determined using modeling approaches and often require an abundance of variables and observations for calibration. Small rural streams that lack water use designations often lack available data to utilize current modeling strategies. This study proposes the use of a 3-phase hybrid stepwise statistical modeling approach using generalized linear mixed models (GLMM) and a reference stream. Two streams in Central Texas were sampled for 13 months between February 2020 and February 2021, one being impacted by a wastewater treatment plant (WWTP). Dissolved phosphorus (PO4-P), ammonia (NH3-N), nitrite/nitrate (NO2 + NO3-N), total nitrogen (TN), and total phosphorus (TP) were sampled in both streams for each month. Non-point sources of contamination, such as land use/land cover and geomorphology composition, were quantified for both sub-basin drainage areas. Phase I models predicted nutrient concentrations in the reference stream using non-point source variables along with discharge and temporal variables. Best fit models were carried forward to phase II and leveraged a point-source variable, which is a naïve estimate of effluent nutrient concentration in the absence of assimilation. Phase II model coefficients highlight the significance of point-source contamination in predicting nutrient concentration, but overall lacked the ability to make future predictions under new hydrologic regimes from WWTP intensification. Phase III models included deterministically calculating an uptake variable using the relationship between discharge and wetted widths, predicting background non-point concentrations by leveraging phase I models, and calculating future nutrient loadings from WWTP intensification. This approach predicted significant increases in nutrient concentrations under planned WWTP intensification scenarios and decreased uptake efficiencies under the new hydrologic regimes.

Efficiency of home water filters on pesticide removal from drinking water

Water pollution via natural and anthropogenic activities has become a global problem, which can lead to short and long-term impacts on humans' health and the ecosystems. Substantial amounts of individual or mixtures of organic pollutants move into the surface water via point and non-point source contamination. Some of these compounds are known to be toxic and difficult to remove from water sources, thus affecting their quality. Moreover, environmental regulations in high-income countries have become very strict for drinking water treatment over the past decades, especially regarding pesticides. This study aimed to evaluate the efficiency of different residential water treatments to remove 13 pesticides with distinct physicochemical characteristics from the drinking water. Nine water treatments were used: four membrane filters, an activated carbon filter, ultraviolet radiation, reverse osmosis, ion exchange resins, and ozonation. The trial was performed with tap water contaminated with an environmental concentration of 13 pesticides. According to the results, activated carbon and reverse osmosis were 100% efficient for pesticide removal, followed by ion exchange resins and ultraviolet radiation. Membrane filters, in general, showed low efficiency and should, therefore, not be used for this purpose.

Assessment of Water Quality Variations and Trophic State of the Joumine Reservoir (Tunisia) by Multivariate Analysis

North Tunisia’s Joumine reservoir provides water for drinking and agriculture irrigation purposes. Therefore, its water quality is crucial, especially with the recurrence of dry years in a global climate change context. This study aims to evaluate its environmental parameters, phytoplankton community structure, and trophic status. The data were newly analyzed using multivariate statistical methods and redundancy analysis (RDA) with the Trophic State Index (TSI) and Trophic State Index deviation (TSID). Monthly sampling occurred from May 2021 to June 2022 at eight stations. Water samples were collected to assess physical-chemical parameters and Chlorophyll-a, as well as to identify phytoplankton species. Three seasonal clusters of summer, autumn, and spring were identified. Water nutrient variations primarily resulted from point and non-point source contamination, along with natural processes. Carlson’s Trophic State Index (CTSI) indicates a eutrophic status for the Joumine reservoir. TSID indicated there was no algal turbidity in the reservoir. The study identified 25 phytoplankton taxa, with Chlorophyceae exhibiting high densities and diversities. RDA revealed that NO3−, NH4+, DO, pH, water flow, and water temperature were the most important environmental factors controlling phytoplankton structure in the Joumine reservoir. The outcomes of this study may provide helpful information to improve the management of the Joumine reservoir.

Spatio-temporal analysis of the sources and transformations of anthropogenic nitrogen in a highly degraded coastal basin in Southeast China.

Nitrogen transport from terrestrial to aquatic environments could cause water quality deterioration and eutrophication. By sampling in the high- and low-flow periods in a highly disturbed coastal basin of Southeast China, hydrochemical characteristics, nitrate stable isotope composition, estimation of potential nitrogen source input fluxes, and the Bayesian mixing model were combined to determine the sources and transformation of nitrogen. Nitrate was the main form of nitrogen. Nitrification, nitrate assimilation, and NH4+ volatilization were the main nitrogen transformation processes, whereas denitrification was limited due to the high flow rate and unsuitable physicochemical properties. For both sampling periods, non-point source pollution from the upper to the middle reaches was the main source of nitrogen, especially in the high-flow period. In addition to synthetic fertilizer, atmospheric deposition and sewage and manure input were also major nitrate sources in the low-flow period. Hydrological condition was the main factor determining nitrate transformation in this coastal basin, despite the high degree of urbanization and the high volume of sewage discharge in the middle to the lower reaches. The findings of this study highlight that the control of agricultural non-point contamination sources is essential to pollution and eutrophication alleviation, especially for watersheds that receive high amounts of annual precipitation.

Spatial distribution, sources and health risk assessment of heavy metals in topsoil around oil and natural gas drilling sites, Andhra Pradesh, India

Soils are usually the interface between human activity and environmental components that must be conserved and protected. As a result of rising industrialization and urbanization, activities such as exploration and extraction operations lead to the release of heavy metals into the environment. This study presents distribution of six heavy metals (As, Cr, Cu, Ni, Pb and Zn) in 139 top soil samples collected in and around oil and natural gas drilling sites at a sampling density of 1 site/12 km2. The results indicated the concentration ranged from 0.1 to 16 mg/kg for As, 3–707 mg/kg for Cr, 7–2324 mg/kg for Cu, 14–234 mg/kg for Ni, 9–1664 mg/kg for Pb, and 60–962 mg/kg for Zn. The contamination of soil was estimated on the basis of Index of geo accumulation (Igeo), enrichment factor (Ef), and contamination factor (Cf). Further, spatial distribution pattern maps indicated that the pollution levels for Cu, Cr, Zn, and Ni were higher around drilling sites of the study area relative to other regions. Using exposure factors for the local population and references from the USEPA’s integrated database, potential ecological risk indices (PERI) and health risk assessments were made. The hazard index (HI) values of Pb (in adults) and Cr, Pb (in children) exceeded the recommended limit of HI = 1, indicating the non-carcinogenic risks. Total carcinogenic risk (TCR) calculations revealed Cr (in adults) and As, Cr (in children) levels in soils exceeded the threshold value of 1.0E − 04, indicating significant carcinogenic risk due to high metal concentrations in the study area. These results may assist in determining the soil’s present state and its effect due to extraction strategies used during drilling process and initiate few remedial techniques, particularly for proper management strategies in farming activities to decrease point and non-point source of contamination.

Lime slurry treatment of soils developing on abandoned coal mine spoil: Linking contaminant transport from the micrometer to pedon-scale

Historical and abandoned coal mine spoil continues to generate acid- and metal(loid)-rich porewaters and represents a geographically large and diffuse non-point source of contamination to local watersheds. A potentially inexpensive approach to treat these materials and soils developing on them is through the application of lime slurries, to neutralize acidity and encourage the (co)precipitation of metal(loids) with Fe(III)-(oxy)hydroxides, and potentially other metal-oxides and/or Ca-bearing phases. The efficacy of this approach was evaluated through parallel field application and laboratory-based flow-through column experiments. The field site is Huff Run sub-watershed 25 located in Tuscarawas County, Ohio and was chosen in part because it was previously classified as one of the most highly AMD-impacted sub-watersheds in the region. Two locations with historical spoil were chosen and suction lysimeters were installed at 25 and 75 cm depth to monitor porewater composition on two sides at the base of each pile. Half of each slope received seven lime slurry treatments from June through October of 2017. A suite of aqueous (ICP-OES, IC, and TOC-L) and solid phase geochemical and mineralogical approaches (quantitative SEM-EDS and synchrotron μ-XRF) were used to determine how composition, texture, morphology, and spatial distribution of mineral coatings differ in pre- and post-lime treated soils, and how that impacts the distribution and transport of trace metal(loid)s. Mine spoil porewater at site 1 was slightly less alkaline (pH ranging from 7.04 to 7.37) than at site 2 (ranging from 7.55 to 7.71), and average electrical conductivity values at site 1 (316–405 μS cm−1) were slightly lower than at site 2 (358–464 μS cm−1), although differences between the sites were not significant. Porewater pH and electrical conductivity in all lysimeters decreased over the course of the field season but there was no obvious response to lime treatment at either site or any depth. At site 1, both treatment and depth were significant factors affecting Ca, K, Ni, SO42−, and DOC concentrations while only treatment effects were significant for dissolved Al and Cu (p < 0.05). For all soils, there were no trends in metal concentration observed over time although DOC and SO42− decreased over the field season. Pedon-scale changes in metal porewater concentrations in response to treatment were linked to micrometer-scale changes in mineral surface coatings; specifically, higher concentrations of Ca, Fe, Mn, and Zn were observed in the coatings and no changes were observed in Fe redox speciation, whereas total S decreased likely due to oxidation of S in coal fragments. In contrast to the field experiment, the column experiments exhibited a much greater response in effluent composition with respect to lime treatment. The untreated columns had approximately an order of magnitude more H+ leached over the course of the experiment (p < 0.001) and resulted in greater Ca, Al, Cu, and DIC leached and less Mn, Zn, and SO42−. Soils treated with the lime slurry in the column experiments exhibited larger and thicker secondary Fe-coatings, including the addition of Fe-sulfates. Despite clear trends in the laboratory-based column experiment where the lime-to-soil ratio was higher, the effects were either muted or undetected in the field pilot project, suggesting that a higher application rate of lime in the field is needed to achieve a similar effect. This work provides evidence that a less alkaline lime slurry could be a practical and inexpensive method of treating coal mine spoil-impacted soils and represents an important step in linking laboratory-based remediation studies to implemented field-based studies.

Optimal discharge protocol for urban stormwater settling tank across different scenarios under limited data aided with Monte-Carlo simulation incorporated mathematical model

Nonpoint source contamination from early stormwater runoff in the urban area has been frequently reported, and a comprehensive urban stormwater treatment system in high population density location is essential. However, there is an absence of a comprehensive discharge protocol for the settling tank that leads to inefficient treatment process with a non-adaptive practice that fixing certain discharge period. A case study in a large-scale urban settling tank located at Y-city, South Korea is considered to validate the discharge protocol proposed. The stormwater is first analyzed with its respective characteristics from various interception facilities, which act as buffers before entering settling tank. Thereupon, homogenous stormwater entered from multiple interception facilities is collected accordingly from the settling tank to assess the settling performance by measuring the suspended solid (SS) concentration in different timeframes. A mathematical model targeting the settling tank is then developed and further calibrated at different settling tank layers across different settling periods with multi-objective genetic algorithms based on the settling parameters considered. An uncertainty analysis is then conducted due to the relatively small dataset collected by incorporating 10,000 attempts of Monte-Carlo simulation, varying the SS concentration at different layers in the settling tank. As a result, discharge time for the top and middle layer by obeying the discharge limit falls at the 18th and 58th hour from the initial stormwater entry to the settling tank. This study successfully demonstrated the approach on identifying optimal discharge protocol for urban settling tank based on the initial SS concentration under limited data.

Assessing the effectiveness of potential best management practices for science-informed decision support at the watershed scale: The case of the Mar Menor coastal lagoon, Spain

Coastal lagoons are ecosystems of high environmental importance but are quite vulnerable to human activities. The continuous inflow of pollutant loads can trigger negative impacts on the ecological status of these water bodies, which is contrary to the European Green Deal. One example is the Mar Menor coastal lagoon in Spain, which has experienced significant environmental degradation in recent years due to excessive external nutrient input, especially from non-point source (NPS) pollution. Mar Menor is one of the largest coastal lagoons of the Mediterranean region and a site of great ecological and socio-economic value. In this study, the highly anthropogenic and complex watershed of Mar Menor, known as Campo de Cartagena (1244 km2), was modelled with the Soil and Water Assessment Tool (SWAT) to analyse potential options for recovery of this unique system. The model was used to simulate several best management practices (BMP) proposed by recent Mar Menor regulations, such as vegetative filter strips, shoreline buffers, contour farming, removal of illegal agriculture, crop rotation management, waterway vegetation restoration, fertiliser management and greenhouse rainwater harvesting. Sixteen scenarios of individual and combined BMPs were analysed in this study. We found that, as individual measures, vegetative filter strips and contour farming were most effective in nutrient reduction: approximately 30 % for total nitrogen (TN) and 40 % for total phosphorus (TP). Moreover, waterway vegetation restoration showed the highest sediment (S) reduction at approximately 20 %. However, the combination of BMPs demonstrated clear synergistic effects, reducing S export by 38 %, TN by 67 %, and TP by 75 %. Selecting the most appropriate BMPs to be implemented at a watershed scale requires a holistic approach considering effectiveness in reducing NPS pollution loads and BMP implementation costs. Thus, we have demonstrated a way forward for enabling science-informed decision-making when choosing strategies to control NPS contamination at the watershed scale.

Spatial and Temporal Pattern of Norovirus Dispersal in an Oyster Growing Region in the Northeast Pacific.

Contamination of Pacific oysters, Crassostrea gigas, by human norovirus (HuNoV) is a major constraint to sustainable shellfish farming in coastal waters of the Northeast Pacific. HuNoV is not a marine virus and must originate from a human source. A barrier to effective management is a paucity of data regarding HuNoV dispersal in the marine environment. The main objective of this study was to identify the spatial distribution and persistence of HuNoV in an active shellfish farming region in the Northeast Pacific. Market-size C. gigas were sequentially deployed for two-week intervals at 12 sites during the 2020 winter risk period from January to April. Detection of HuNoV quantification was performed by reverse transcription real-time PCR (RTqPCR) according to method ISO 15216-1:2017, with modifications. RTqPCR did not detect GI HuNoV. The estimated prevalence of GII HuNoV in oyster digestive tissue was 0.8 ± 0.2%. Spatiotemporal analysis revealed that contamination of oysters with GII HuNoV changed through time and space during the surveillance period. A single cluster of oysters contaminated with GII.2 HuNoV was detected in a small craft harbor on 23 April. There was no significant increase in the proportion of positive pools in the next nearest sampling station, indicating that HuNoV is likely to disperse less than 7 km from this non-point source of contamination. Results from this study indicate that HuNoV contamination of coastal waters from non-point sources, such as small craft harbors and urban settings, can pose a significant localised risk to shellfish farming operations in the region.

Land Use, Weather, and Water Quality Factors Associated With Fecal Contamination of Northeastern Streams That Span an Urban-Rural Gradient

Fecal contamination of surface water has been associated with multiple enteric disease outbreaks and food recalls. Thus, it is important to understand factors associated with fecal contamination of agricultural water sources. Since fecal indicator bacteria (FIB) were used to monitor surface water for potential fecal contamination, the purpose of the present study was to characterize associations between environmental factors, and (i) FIB (E. coli, Enterococcus, and coliform) levels, and (ii) host-specific fecal marker detection. This study used data collected from 224 sites along 3 waterways, which spanned an urban-rural gradient around Syracuse, New York. Between 2008 and 2017, 2,816 water samples were collected, and E. coli, Enterococcus, and/or coliform concentrations were enumerated. Thirty-one samples were also tested for human and ruminant microbial source-tracking markers. Water quality (e.g., turbidity, nitrate) and weather data were also collected for each site. Univariable Bayesian regression was used to characterize the relationship between each microbial target and land use, water quality, and weather factor. For each model, probability of direction and region of practical equivalence overlap (ROPE) were calculated to characterize the association's direction and strength, respectively. While levels of different FIB were not correlated with each other, FIB levels were associated with environmental conditions. Specifically, FIB levels were also positively associated with temperature, nutrient and sediment levels. Log10 E. coli levels increased by 0.20 (CI = 0.11, 0.31) and log10 Enterococcus levels increased by 0.68 (CI = 0.08, 1.24) for each log10 increase in salinity and nitrate, respectively. These findings may indicate that similar processes drove microbial, sediment, and nutrient contamination of the sampled watersheds. While fecal contamination was strongly associated with land use, the direction of association varied between FIBs and the buffer distance used to calculate land use metrics. E. coli levels and human marker detection were positively associated with percent pasture cover within 122, 366, and 1,098 m of the sampling site, while Enterococcus and coliform levels were only associated with pasture cover within 1,098 m (not 122 or 366 m). Ruminant markers were positively associated with pasture cover within 122 m, but not 366 or 1,098 m. These findings highlight the importance of considering (i) adjacent land use (and associated non-point sources of contamination) when developing strategies for managing fecal hazards associated in agricultural and recreational water, and (ii) spatial scale (e.g., 122 vs. 1,098 m) when developing these strategies.

Validation and Projections of Climate Characteristics in the Saginaw Bay Watershed, MI, for Hydrologic Modeling Applications

Fundamental differences in the nature of climate and hydrologic models make coupling of future climate projections to models of watershed hydrology challenging. This study uses the NCAR Weather Research and Forecast model (WRF) to dynamically downscale climate simulations over the Saginaw Bay Watershed, MI and prepare the results for input into semi-distributed hydrologic models. One realization of the bias-corrected NCAR CESM1 model's RCP 8.5 climate scenario is dynamically downscaled at a spatial resolution of 3 km by 3 km for the end of the twenty-first century and validated based on a downscaled run for the end of the twentieth century in comparison to ASOS and NWS COOP stations. Bias-correction is conducted using Quantile Mapping to correct daily maximum and minimum temperature, precipitation, and relative humidity for use in future hydrologic model experiments. In the Saginaw Bay Watershed the end of the twenty-first century is projected to see maximum and minimum average daily temperatures warming by 5.7 and 6.3°C respectively. Precipitation characteristics over the watershed show an increase in mean annual precipitation (average of +14.3 mm over the watershed), mainly due to increases in precipitation intensity (average of +0.3 mm per precipitation day) despite a decrease in frequency of −10.7 days per year. The projected changes have substantial implications for watershed processes including flood prediction, erosion, mobilization of non-point source and legacy contaminants, and evapotranspirative demand, among others. We present these results in the context of usefulness of the downscaled and bias corrected data for semi-distributed hydrologic modeling.