Contaminant Loads Research Articles

Determinant Factors of Microbial Drinking Water Quality at the Point of Use in Rural Ethiopia: A Case Study of the South Gondar Zone

Access to safe drinking water is a fundamental human need for health and well-being implemented globally by the United Nations under Sustainable Development Goal (SDG) 6. Storing drinking water is common in rural areas of Ethiopia due to off-premises water sources and intermittent piped water supply. However, this practice can lead to further contamination during collection, transport, and storage, posing a risk to public health. The objective of this study was to identify the determinant factors of drinking water quality at the point of use in the rural setting of northwestern Ethiopia, South Gondar zone. A questionnaire survey was conducted, and water samples from 720 households were collected during the wet and dry seasons. The determinant factors were identified using the multivariable logistic regression model. About 39.2% of the surveyed households had basic water supply services, 41.9% were using unimproved sources, and 8.3% were using surface water. Only 9.4% were using basic sanitation services, and 57.2% were practicing open defecation. Safe water storage was practiced by 84.3% of households, while only 2% engaged in household water treatment. About 14% of dry and 8% of wet season samples from the storage were free from fecal coliform bacteria. Furthermore, 52.9% of dry and 62.2% of wet season samples fell under the high microbial health risk category. The season of the year, the water source type, storage washing methods, and the socioeconomic status of the household were identified as key predictors of household drinking water fecal contamination using the multivariable logistic regression model. It was observed that the drinking water in households had a high load of fecal contamination, posing health risks to consumers. To tackle these problems, our study recommends that stakeholders should enhance access to improved water sources, implement source-level water treatment, increase access to improved sanitation facilities, advocate for safe household water management practices, and endorse household water treatment methods.

An Efficient LC–HRMS-Based Approach to Evaluate Pesticide Contamination in Water Bodies with Measurement Uncertainty Considerations

Over recent decades, the global occurrence of pesticide residues in aquatic environments has been a pivotal issue; however, their trace-level concentrations necessitate the establishment of ultra-sensitive and reliable analytical approaches. To this end, the present study describes the optimization and validation of an LC-HRMS-based method for the accurate determination of 18 pesticides in river and sea water, accompanied by a measurement uncertainty estimation. This method was applied to analyze 17 real samples from agriculture and aquaculture-impacted areas in Greece and Albania. Different solid-phase extraction (SPE) protocols were tested. For the analysis, cutting-edge Orbitrap MS technology and MS/MS fragmentation, along with the use of matrix-matched calibration curves, provided unprecedented accuracy (<5 ppm) and sensitivity for the confirmation of positive detections. Regarding method performance, exceptional linearity was obtained; the limits of quantification ranged from 1.7 ng L−1 to 90 ng L−1, recoveries varied from 61% to 96% in river water, while slightly higher recoveries (60–111%) were observed in seawater. In all cases, repeatability and intra-laboratory reproducibility were below 15%. The measurement expanded uncertainty (U′, k = 2) was estimated considering precision and bias. MU% values were lower than 50% in all cases, as recommended in SANTE guidelines and applied to the quantified results. The matrix effect study exhibited negative values (<20%) for all compounds. Application to real samples showed a low pesticide contamination load that should not be underestimated.

Monitoring and Studying the Behavior of Metals in an Industrial Wastewater Treatment Plant in Italy

Heavy metals represent a significant hazard in textile wastewater, posing a considerable risk to both the ecosystem and human health. The objective of this study was to analyze the removal efficiency of specific heavy metals in a large wastewater treatment plant (WWTP) located in Prato (Tuscany, Italy), where the main Italian textile district is based. To achieve this, the mass balance calculation approach was employed. Therefore, two monitoring campaigns were conducted, collecting wastewater and sludge samples in some specific sections of the WWTP. The concentrations of Pb, Cd, Ni, As, and Sn were consistently below the detection limits. A good removal efficiency was determined for Zn, Cu, Ba, Crtot, and Sb, in the range of 37–79%. These metals are predominantly present in particulate form, facilitating their removal through sedimentation. Conversely, boron is largely present in the dissolved phase, resulting in its complete release through the treated effluent. Subsequently, an excellent linear correlation was identified between the input load and the contaminant load removed. This demonstrated that the plant’s efficiency remains unaffected by an increase in the input load at the observed contaminant concentrations. Finally, a probability law was identified that demonstrates an excellent degree of approximation in representing inlet metal concentrations. The findings of this study indicate that the treatment systems employed by the WWTP are capable of effectively removing heavy metals.

Techno-economic analysis of nutrient recovery from urine: Centralized treatment of hydrolyzed urine vs. decentralized treatment of fresh urine

The centralized process integrating “Thermal NH3 stripping → Na-chabazite adsorption → Struvite precipitation” has been proposed for nutrient recovery from hydrolyzed urine. Meanwhile, a decentralized approach involving Na-chabazite and biochar adsorption has been suggested for fresh urine, followed by urea hydrolysis and the subsequent centralized integration of struvite precipitation and thermal stripping. However, a systematic comparison of nutrient recovery processes for fresh and hydrolyzed urine, evaluating both technical viability and financial feasibility, is lacking. This study addresses the gap by thoroughly examining both scenarios over a 30-year project, using Université Laval as a case study. It provides a comprehensive roadmap for techno-economic assessment, offering guidance for evaluating nutrient recovery processes prior to scaling up. The decentralized process achieved higher recovery efficiencies for nitrogen and phosphorus, at 89.4 % and 98.7 %, respectively. Financially, the decentralized scenario demonstrated its advantage in the lower initial investment requirement, thereby generating higher gross profits compared to the centralized scenario. As a result, it is projected to reach the break-even point in the 21st year, demonstrating its potential economic feasibility. Sensitivity analysis indicated that a 20 % increase in urine inflow rate and the price of urea-enriched biochar could further enhance the economic viability of both processes. Beyond financial considerations, both scenarios have the potential to reducing the contaminant loading rate in the downstream wastewater treatment plants and promote nutrient recovery and recycling.

Continental-scale nutrient and contaminant delivery by Pacific salmon.

The movement of large amounts of nutrients by migrating animals has ecological benefits for recipient food webs1,2 that may be offset by co-transported contaminants3,4. Salmon spawning migrations are archetypal of this process, carrying marine-derived materials to inland ecosystems where they stimulate local productivity but also enhance contaminant exposure5-7. Pacific salmon abundance and biomass are higher now than in the last century, reflecting substantial shifts in community structure8 that probably altered nutrient versus contaminant delivery. Here we combined nutrient and contaminant concentrations with 40 years of annual Pacific salmon returns to quantify how changes in community structure influenced marine to freshwater inputs to western North America. Salmon transported tonnes of nutrients and kilograms of contaminants to freshwaters annually. Higher salmon returns (1976-2015) increased salmon-derived nutrient and contaminant inputs by 30% and 20%, respectively. These increases were dominated by pink salmon, which are short-lived, feed lower in marine food webs than other salmon species, and had the highest nutrient-to-contaminant ratios. As a result, the delivery of nutrients increased at a greater rate than the delivery of contaminants, and salmon inputs became more ecologically beneficial over time. Even still, contaminant loadings may represent exposure concerns for some salmon predators. The Pacific salmon example demonstrates how long-term environmental changes interact with nutrient and contaminant movement across large spatial scales and provides a model for exploring similar patterns with other migratory species9.

Legacy persistent organic pollutants among multiple cetacean species in the Northwest Atlantic

The historical contamination of eastern Canadian shelf waters remains an ongoing concern, predominantly stemming from anthropogenic discharges in the Great Lakes region. Although legacy persistent organic pollutants (POPs) were banned decades ago, it remains unclear whether their concentrations have sufficiently decreased to safer levels in cetaceans that feed in the continental shelf waters of the northwestern Atlantic. This study compares polychlorinated biphenyl (PCB) and organochlorine pesticide (OC) accumulation in six cetacean species sampled in the Northwest Atlantic from 2015 to 2022. We assessed the influence of relative trophic level and foraging habitat preferences on POP accumulations among species using stable isotopes and fatty acids as dietary tracers. We further identified the species most susceptible to the effects of these contaminants. Killer whales (Orcinus orca) exhibited the highest PCB (∼100 mg/kg lw) and OC concentrations, followed by other odontocetes, with lowest concentrations in mysticetes. Stable isotope analysis revealed an unexpected lack of correlation between δ15N values and contaminant levels. However, there was a positive correlation between δ13C values and POP concentrations. Cetaceans foraging on pelagic prey species, as indicated by elevated proportions of the FA markers 22:1n11 and 20:1n9, had lower contaminant loads compared to cetaceans with benthic/coastal FA signatures. PCB and DDT (dichlorodiphenyltrichloroethane) concentrations are lower now in most cetacean species than in the 1980s and 1990s, likely due to regulatory measures restricting their production and use. Although current PCB concentrations for most species are under the thresholds for high risks of immune and reproductive failure, concentrations in killer whales exceed all established toxicity thresholds, underscoring the need for further action to reduce sources of these contaminants to the continental shelf waters of the northwestern Atlantic.

Agricultural pesticides in feathers of the burrowing owl (Athene cunicularia) and its relationship to land-use in the argentinean pampas

The pampas of South America represent one of the most productive lands for agriculture in the world, and consequently this activity has expanded throughout the region, especially in Argentina. In this context, native fauna faces various risks associated with agriculture, with exposure to pesticides being one of the most dangerous and deadly. Assessing the impact of pesticides on wildlife becomes fundamental and the use of sentinel species emerges as an important tool to monitor environmental health. In this study, we determined pesticide levels in the burrowing owl Athene cunicularia nesting in both rural and urban areas of the argentinean pampas. We used a multiple scale approach to evaluate the influence of land-uses (urban, crops, and grazing fields) at the nesting site on the contaminant load of A. cunicularia individuals, and assessed the potential use of this owl as a sentinel species. From March 2018 to January 2020, A. cunicularia feathers were collected at their nest sites in one urban and two rural areas. These samples were analyzed for the presence of contaminants, including chlorpyrifos and 18 organochlorine pesticides. All the compounds analyzed were detected in A. cunicularia samples. The chlorpyrifos showed the highest frequency of occurrence and concentration, thus denoting the exposure of owls to current-use pesticides. ∑DDTs showed the highest occurrence among organochlorines, followed by ∑HCHs > ∑Endosulfans > ∑Heptachlors > ∑Drins = ∑Chlordanes > methoxychlor. Principal Component Analysis showed that most of the compounds found in A. cunicularia samples showed a positive association with grazing fields, suggesting that exposure to contaminants does not depend on specific habitat use at the local scale, but probably the regional scale. Our results evidenced the exposure of A. cunicularia individuals to past and current-use pesticides in the pampas of Argentina, and indicate that this owl would be useful as a sentinel species.

Photo-deposition of AgO thin films on TiO2 substrate for (P-N) hetero-junction applications: Considering the degree of contamination

This study explored the development of photocatalytic heterostructures via the P-N junction formation between TiO2 and AgO. TiO2 thin films were fabricated on glass substrates through dip coating. Subsequently, photodeposition of AgO was achieved under sunlight irradiation using varying AgNO3 concentrations (0.5-2.5g/L). The films were characterized using XRD, SEM, EDX, UV-vis, and water droplet tests. Samples with concentrations below 2g/L uniquely exhibited the anatase phase, while a significant prominence of AgO was observed in the film prepared with a 2g/L AgNO3 concentration. Silver nitrate contamination loads had a significant impact on the particle size and the overall morphological characteristics of the heterojunctions. The band gap values were 3.52eV for the anatase substrate, whereas the band gaps of the photodeposited films decreased from 2.44 to 1.98eV. Despite all films being hydrophilic, a rise in water droplet contact angle was observed in the heterojunctions compared to the pure TiO2. Photodegradation of methylene blue under sunlight irradiation demonstrated exceptional efficiency (>90%) for the 2g/L AgNO3 heterojunction in 6hours, maintaining high photocatalytic activity over multiple cycles (>77%). This same configuration achieved a 50% degradation of amoxicillin within 2hours. This investigation addresses water contamination issues while offering a straightforward production method for efficient P-N junction co-catalysts.

The impact of blue-green infrastructure on trace contaminants: A catchment-wide assessment

Blue-green infrastructure (BGI) reduce urban combined sewer overflows (CSOs) and stormwater outlets (SWOs). However, most conventional BGI are not designed to remove trace organic contaminants. Little is known about the potential of conventional BGI to improve surface water quality by reducing the discharge of trace organic contaminants. We derived wash-off loads for street runoff (6PPD-q, DPG, and HMMM), construction materials (diuron), and wastewater-derived contaminants (diclofenac) based on measurements in the combined sewer system. Subsequently, the performance of four BGI types (bioretention cells, green roofs, porous pavements, and urban wetlands) to reduce the discharge of trace organic contaminants via SWOs and CSOs was quantified with a hydrodynamic SWMM model. Moreover, the catchment-wide impact of SWOs and CSOs on surface water was assessed using risk quotients. We found that the annually discharged load can be considerably reduced by implementing BGI. Among the studied BGI types, bioretention cells are the most effective, with a load reduction of up to 80% to surface waters, mainly due to a larger suitable implementation area and a substantial stormwater infiltration. BGI implemented in the separate sewer system are more effective in reducing stormwater contaminant loads than BGI in the combined system. The assessment of the risk quotient in the surface water showed that the concentrations during SWO and CSO discharges exceed the acute environmental threshold in the surface water for 6PPD-q, DPG, diuron, and diclofenac during several events. The implementation of BGI reduced the hours of exceeded risk quotient in the surface water by 93% for bioretention cells. These findings underscore the need for a catchment-wide assessment of future BGI implementations to quantify, manage, and mitigate the impacts of urban pollution.

Long-term evaluation of soil-based bioelectrochemical green roof systems for greywater treatment

Water scarcity has generated the need to identify new sources. Due to its low organic contaminant load, greywater reuse has emerged as a potential alternative. Moreover, the search for decentralized treatment systems in urban areas has prompted research on using green roofs for greywater treatment. However, the performance of organic matter removal is limited by the type of substrate and height of the growing media. Bioelectrochemical systems (BESs) improve treatment performance by providing an additional electron acceptor (the electrode). In this study, nine reactors under three different conditions, i.e., open circuit (OC), microbial fuel cell (MFC), and microbial electrolysis cell (MEC), were built to evaluate the treatment of synthetic greywater in a substrate-growing medium composed of perlite and coconut fiber and operated in batch-cycle mode for 397 days. The results suggested that using BESs enables greywater treatment and the removal of pollutants to levels that allow their reuse for irrigation. Furthermore, electrical conductivity was reduced from 732.4 ± 41.2 μS/cm2 in OC to 637.32 ± 22.73 μS/cm2 and 543.15 ± 19.69 μS/cm2 in MEC and MFC, respectively. The soluble chemical oxygen demand in the latter treatments reached 76% removal, compared to levels above the OC, which only reached approximately 67%. Microbial community analysis revealed differences, mainly in the cathodes, showing a higher development of Flavobacterium, Azospirillum, and Zoogloea in MFCs, which could explain the higher levels of organic matter removal in the other conditions, suggesting that the BES could produce an enrichment of beneficial bacterial groups for treatment. Therefore, implementing BESs in green roofs enables sustainable long-term greywater treatment.

Exploring soil pollution patterns in Ghana's northeastern mining zone using machine learning models

This study assessed the pollution status and effectiveness of machine learning models in predicting pollution indices in soils from a mining area in Northeastern Ghana. 552 soil samples were analysed with an Energy Dispersive X-ray Fluorescence (ED-XRF) spectrometer for their elemental concentrations. Four pollution indices; Nemerow Integrated Pollution Index (NIPI), degree of contamination (Cdeg), modified degree of contamination (mCdeg) and Pollution Load Index (PLI). Additionally, the Multivariate Adaptive Regression Splines (MARS) machine learning approach were used. The high CV%, skewness, and kurtosis values show a high degree of variability and uneven distribution patterns which denotes dispersed hotspots that can be interpreted as an influence of gold anomalies and illegal mining activities in the area. V (120.86 mg/L), Cr (242.42 mg/L), Co (30.92 mg/L) Ba (337.62 mg/L), and Zn (35.42 mg/L) recorded values higher than the global and regional contaminant thresholds. The NIPI shows that 46.74% and 26.81% of samples are slightly and moderately polluted respectively. The Cdeg analysis supports these findings, with 36.96% and 41.49% of samples classified as having “moderate” to “considerable” contamination, respectively. The PLI indicates progressive soil quality deterioration (43.84%) of samples reflecting substantial environmental disturbance. The pollution indices show the effect of illegal mining on Shaega, Buin and other areas in the eastern boundary of the study. The MARS models developed for the study demonstrated high predictive capabilities with an R2 value of 0.9665 for model 1 (NIPI), and RMSE and MAE values of 0.8227 and 0.4287 respectively. For model 2 (Cdeg), R2 value of 0.9863, RMSE and MAE of 1.0416 and 0.6181, respectively. Model 3 (mCdeg) produced an R2 value of 0.9844, RMSE and MAE of 0.1225 and 0.0670. These findings suggest MARS models can be an integral tool for soil quality analysis in cooperation with pollution indices. The study suggests that remedial and legislative measures be implemented to address the issue of illegal mining in the area.

Research on the mechanisms of 2D road runoff pollution migration and the influence of pipeline overflow onto roads

In this paper, a novel numerical model capable of high-resolution, accurate simulation of the accumulation, wash-off, and migration of nonpoint source (NPS) pollutants on roads is proposed, effectively addressing the challenge of limited pipe network data for high-density urban building communities. This approach is based on a 1D-2D hydrodynamic and water quality dynamic bidirectional coupling model: GAST-SWMM. The calculation accuracy of the GAST two-dimensional road NPS wash-off model is validated via comparison with experimental data. The obtained Nash-Sutcliffe efficiency (NSE) is greater than 0.8. Moreover, the model was used to simulate the NPSs in a densely populated urban region of Xi'an, China, lacking building community pipeline data. The NPS pollutant transport and fate under the influence of both road runoff and the building community hydrodynamic water quality during rainfall events with a specific return period were examined. The proposed model can effectively and accurately replicate the accumulation and removal of NPS pollutants on a two-dimensional road and their dynamic interaction with the drainage network. With increasing rainfall return period, the peak time of the surface contaminant total load is postponed. The maximum surface pollutant load durations during rainfall events with 2-, 10-, and 50-year return periods are 60, 75, and 80 min, respectively. During the peak surface pollutant load time, the overflow pollutant fraction can exceed 85% for a 50-year rainfall return period. The simulation method presented in this paper accurately captures the spatial and temporal variations in NPS pollutants in densely populated urban areas, even when pipe network data for building communities are lacking. This method offers valuable technical assistance for urban environmental management and water quality protection.

Eco-toxic Risk Assessment of microplastics in water and sediment across Nigeria Offshore, Gulf of Guinea.

Globally, the environmental impacts of microplastics (MPs) as emerging pollutants have drawn a lot of attention. This study aimed to assess the distribution and associated potential ecotoxic risk of MPs in the water and sediment of Nigeria's offshore waters. Water and sediment samples were collected from sixteen (16) stations in October 2023 and analysed using Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy and stereomicroscopy. For physical characterization, the composition of MPs in sediment and water was 73 particles/kg and 48 particles/L, respectively, while the ATR-FTIR composition at the Eastern Zone (EZ) was 705 particles/L and 1033 particles/kg, the Central Zone (CZ) was 212 particles/L and 338 particles/kg, and the Western Zone (WZ) was 223 particles/L and 218 particles/kg. The identified MPs shapes were filaments, plastic films, fibre, and microbeads. Polychloroprene (CR) (18.10% and 16.86%) at EZ and CZ and polyvinyl alcohol (PVA) (20.64%) at WZ were most abundant in sediment, respectively. In comparison, PVA (22.3%, 22.2%, and 21.08%) was most abundant across EZ, CZ, and WZ in water. The polymer-based plastic contamination factors (ppCf) and pollution load index (pPLI) showed low contamination and pollution load, and the polymer risk index (pRi) showed medium and low risk in water and sediment, respectively. The polymer ecological risks index (pERI) showed a high-risk level (pERI: 1,001-10,000) in water and sediment across the EZ, CZ, and WZ of the Nigerian offshore waters. In marine environments, an extensive environmental monitoring program and trend forecasting for microplastics are crucial. This study will provide theoretical and technical support for developing efficient legislation or policy on the prevention and control of plastic pollution.

Comprehensive model for predicting toxic equivalents (TEQ) reduction due to dechlorination of polychlorinated dibenzo-p-dioxin and dibenzofurans (PCDD/F congeners)

Remediation-focused predictive tools for polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) rely on transformation models to evaluate the reduction in total contaminant load and toxic equivalency (TEQ). In this study, a comprehensive model predicting the profiles of PCDD/F congeners and the associated TEQs was developed. The model employs first-order kinetics to describe the transformation of 256 reactions for 75 PCDD congeners and 421 reactions for 135 PCDF congeners. It integrates the growth of anaerobic microbial guilds using Monod kinetics on hydrogen release compounds and stoichiometric growth for Dehalococcoides sp. The effects of temperature, salinity, pH, and availability of vitamin B12 (a cofactor) were also integrated. The PCDD/F congeners model was used to extract the first-order dechlorination rate constants from a number of pure culture and mixed microbial microcosm studies. Simulations for the transformation of PCDD/F congeners at concentrations representative of the Tittabawassee or Saginaw Rivers and watershed in MI, USA were carried out. For a starting TEQ of 5000 ng per kg dry sediment (ppt), the model predicted a decrease in the overall TEQ to below 2000 ppt after 2.6 years and below 250 ppt after ∼21 years. The developed model may be used for extracting rates from microcosm studies and to evaluate the effect of engineering interventions on TEQ reduction.

Potential for nutrients reuse, carbon sequestration, and CO2 emissions reduction in the practice of domestic and industrial wastewater recycling into agricultural soils: A review

This review assesses the feasibility of reusing treated wastewater for irrigation in agricultural soils as a strategy for nutrients recycling and mitigation of CO2 emissions. Through a literature review, it was examined wastewater sources enriched with carbon and nutrients, including municipal wastewater and associated sludge, vinasse, swine wastewater, as well as wastewater from the food industry and paper and pulp production. The review also explores the dynamics of organic matter within the soil, discussing the aspects related to its potential conversion to CO2 or long-term storage. It was found that industrial wastewaters, owing to their higher organic matter and recalcitrance, exhibit greater potential for carbon storage. However, the presence of pollutants in wastewater necessitates careful consideration, particularly concerning their impact on soil quality. Toxic metals, microplastics, and organic compounds emerged as significant contaminants that could accumulate in the soil, posing risks to ecosystem health. To mitigate the environmental impacts, it was evaluated various wastewater treatment technologies and their associated carbon emissions. While advanced treatments may effectively reduce the contaminant load and mitigate soil impacts, their adoption is often associated with an increase in CO2 emissions. Membrane bioreactors, microfiltration, ultrafiltration, and up-flow anaerobic sludge blanket reactors were identified as promising technologies with lower carbon footprints. Looking ahead, future research should aim to enhance the understanding of carbon dynamics in soil and validate the environmental impacts of treated wastewater disposal. Despite remaining uncertainties, the literature indicates a positive outlook for wastewater recycling in soil, offering a viable strategy for carbon storage and mitigation of greenhouse gas emissions.

Precipitation contributes to alleviating pollution of rubber-derived chemicals in receiving watersheds: Combining confluent stormwater runoff from different functional areas

The release of rubber-derived chemicals (RDCs) in road surface runoff has received significant attention. Urban surface runoff is often the confluence of stormwater runoff from specific areas. However, the impact of precipitation on RDCs contamination in confluent stormwater runoff and receiving watersheds remains poorly understood. Herein, we investigated the profiles of RDCs and their transformation products in confluent stormwater runoff and receiving rivers affected by precipitation events. The results showed that 34 RDCs are ubiquitously present in confluent stormwater runoff and surface water, with mean concentrations of 1.03–2749 and 0.28–436 ng/L, respectively. The most dominant target compounds in each category were N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), 6PPD-quinone, 2-benzothiazolol, and 1,3-diphenylguanidine. Total RDCs concentrations in confluent stormwater runoff decreased spatially from industrial areas to business districts to college towns. A significant decrease in RDCs levels in surface water after rainfall was observed (P < 0.01), indicating that precipitation contributes to alleviating RDCs pollution in receiving watersheds. To our knowledge, this is the first report of N,N'-ditolyl-p-phenylenediamine quinone (DTPD-Q) levels in surface waters in China. The annual mass load of ∑RDCs reached 72,818 kg/y in confluent stormwater runoff, while 38,799 kg/y in surface water. The monitoring of confluent stormwater runoff is an efficient measure for predicting contamination loads from RDCs in rivers. Risk assessment suggested that most RDCs posed at least medium risks to aquatic organisms, especially 6PPD-quinone. The findings help to understand the environmental fate and risks of RDCs in the confluent stormwater runoff and receiving environments after precipitation events.

Intercorrelations of Chlorinated Paraffins, Dechloranes, and Legacy Persistent Organic Pollutants in 10 Species of Marine Mammals from Norway, in Light of Dietary Niche.

Short-, medium-, and long-chain chlorinated paraffins (CPs) (SCCPs, MCCPs, and LCCPs) and dechloranes are chemicals of emerging concern; however, little is known of their bioaccumulative potential compared to legacy contaminants in marine mammals. Here, we analyzed SCCPs, MCCPs, LCCPs, 7 dechloranes, 4 emerging brominated flame retardants, and 64 legacy contaminants, including polychlorinated biphenyls (PCBs), in the blubber of 46 individual marine mammals, representing 10 species, from Norway. Dietary niche was modeled based on stable isotopes of nitrogen and carbon in the skin/muscle to assess the contaminant accumulation in relation to diet. SCCPs and dechlorane-602 were strongly positively correlated with legacy contaminants and highest in killer (Orcinus orca) and sperm (Physeter macrocephalus) whales (median SCCPs: 160 ng/g lw; 230 ng/g lw and median dechlorane-602: 3.8 ng/g lw; 2.0 ng/g lw, respectively). In contrast, MCCPs and LCCPs were only weakly correlated to recalcitrant legacy contaminants and were highest in common minke whales (Balaenoptera acutorostrata; median MCCPs: 480 ng/g lw and LCCPs: 240 ng/g lw). The total contaminant load in all species was dominated by PCBs and legacy chlorinated pesticides (63-98%), and MCCPs dominated the total CP load (42-68%, except 11% in the long-finned pilot whale Globicephala melas). Surprisingly, we found no relation between contaminant concentrations and dietary niche, suggesting that other large species differences may be masking effects of diet such as lifespan or biotransformation and elimination capacities. CP and dechlorane concentrations were higher than in other marine mammals from the (sub)Arctic, and they were present in a killer whale neonate, indicating bioaccumulative properties and a potential for maternal transfer in these predominantly unregulated chemicals.

Varying amplification efficiency real-time PCR assay for the specific detection and estimation of Salmonella contamination levels in poultry rinse

The most common foodborne infection in the world that leads to hospitalizations is caused by Salmonella enterica. Most Salmonella testing workflows are qualitative and only determine the presence or absence of Salmonella, failing to quantify the contamination load present. This study aimed to standardize and validate a novel varying amplification efficiency real-time PCR assay for the detection and estimation of broad Salmonella contamination levels. The approach relies on the use of two Salmonella-specific primer-probe pairs (i.e., invA and ttrR) with different amplification efficiencies to detect and differentiate between samples contaminated with low (1 log CFU/30 mL) or high (2–4 log CFU/30 mL) levels of Salmonella. The standardized multiplex PCR assay was validated with 131 pure culture strains and 260 laboratory-inoculated chicken-rinse samples. The multiplex assay specifically identified all Salmonella strains. The invA and ttrR primer-probe showed amplification efficiency of 128% and 90%, resulting in an analytic sensitivity of 0.01 and 0.1 pg/reaction for pure culture DNA samples, respectively. After a 5-h enrichment, the assay detected Salmonella in all inoculated samples and accurately identified high and low contamination levels in 87% (n = 226/260) of samples. This varying amplification efficiency (VAE) assay offers a simple approach enabling the food industry to detect and identify high-risk samples contaminated by Salmonella.

Effects of Vibrio vulnificus and Microcystis aeruginosa co-exposures on microplastic accumulation and depuration in the Eastern Oyster (Crassostrea virginica)

Microplastics are ubiquitous in the aquatic environment, and bivalves such as the Eastern oyster (Crassostrea virginica) can accumulate these particles directly from the water column. Bivalves are concurrently exposed to pathogenic and toxin-producing bacteria, including Vibrio spp. and Microcystis spp., which have been shown to adversely impact filtration rates. Exposure to these bacteria could thus affect oysters’ ability to accumulate and depurate microplastics. As climate change creates conditions that favor Vibrio spp. and Microcystis spp. growth in estuaries, it is increasingly important to understand how these co-occurring biotic stressors influence microplastic contamination in bivalves. The objective of this study was to examine how co-exposures to Vibrio vulnificus and Microcystis aeruginosa influence microplastic accumulation and depuration in Eastern oysters. Oysters were exposed to nylon microplastics (5000 particles L−1) and either V. vulnificus, M. aeruginosa, or both species (104 colony-forming units or cells mL−1, respectively) and sampled over time up to 96 h. Following exposure, remaining oysters were allowed to depurate in clean seawater and sampled over time for up to 96 h. Microplastic concentrations in oysters were quantified and compared among treatments, and rate constants for uptake (ku) and depuration (kd) were calculated using nonlinear regression and two-compartment kinetic models. Overall, microplastic concentrations in oysters exposed to V. vulnificus (X‾ = 2.885 ± 0.350 (SE) particles g−1 w.w.) and V. vulnificus with M. aeruginosa (X‾ = 3.089 ± 0.481 particles g−1 w.w.) were higher than oysters exposed to M. aeruginosa (X‾ = 1.540 ± 0.235 particles g−1 w.w.) and to microplastics alone (X‾ = 1.599 ± 0.208 particles g−1 w.w.). Characterizing microplastic accumulation and depuration in oysters co-exposed to these biotic stressors is an important first step in understanding how contaminant loads in bivalves can change. With this research, the efficacy of depuration for commonly-consumed seafood species can be estimated.

Towards a Canadian National River Water Quality-Modelling System: State of Science and Future Prospects

Water quality is of significant concern and ultimately critical to every Canadian’s quality of life and security. Canada has diverse and vast landscapes and stressors that impact various waterbodies differentially, with influencing factors including contaminant and nutrient loads from human activity (mining effluent, wastewater, agricultural runoff, plastics), landscape change (wetland drainage, urbanization) and climate change (warming water temperatures, longer open water seasons, extreme hydrological events, intensifying wildfires). Canadian rivers are especially important to the overall biogeochemistry, hydrology, biodiversity, and ultimate health of aquatic and terrestrial ecosystems. While each of Canada’s provinces and territories has extensive river water quality (physical, chemical, biotic) data and monitoring programs, Environment and Climate Change Canada coordinates various national programs that contribute to the collection and consolidation of these data and conducts extensive research into the study and modelling of key river water quality processes. Despite program-specific efforts, there remains poor capacity to predict current and future conditions in monitored and unmonitored Canadian rivers, particularly remote or northern rivers, due to a myriad of factors including lack of coordination amongst groups and examination of areas in which modelling efforts might be integrated. Herein, we review and analyse the current state of data availability, process studies, and modelling systems for Canadian river water quality. Our synthesis reveals that specific physical processes (water temperature, ice formation, permafrost thaw, sediment dynamics), biogeochemical processes (dissolved oxygen, dissolved organic matter, nutrient cycling, metals/contaminants) and ecological/biological features (biota mass, functional indicators) are well understood, though complex, and are amenable to empirical or mechanistic modelling. Review of this information assists us in identifying opportunities and challenges for developing a national water quality modelling system (NWQMS), that would eventually include similar modelling activities for parallel processes in lakes and integrated watersheds. We identify needs for stronger coordination of monitoring programs in remote areas, recommend use of novel remote sensing technologies, and development of a flexible, iterative ‘process’ for integrated modelling to which stakeholders beyond government can contribute. Such a platform would support short and long-term predictive models of Canadian water quality and ecosystem health, inform effluent concentration limits, and be an early warning system for source waters.