Concentrations Of Contaminants In Water Research Articles

Screening of Characteristic Pollutants and Risk Pollutants in Different Media in the Yangtze River Basin Using Comprehensive Evaluation and Risk Quotient Methods

A variety of pollutants have frequently been detected in the Yangtze River Basin with the rapid economic development, the population increase, and the acceleration of urbanization, which threaten the aquatic ecosystem and human health. A multi-criteria comprehensive evaluation method was developed to identify the characteristic pollutants, and the risk quotient method was used to derive the risk pollutants in water and sediment samples in this article. A total of 155 pollutants from 11 categories were detected in the Yangtze River Basin according to the literature research. Then, the K-means method was used to analyze the cluster of pollutant comprehensive scores. All pollutants were graded based on their scores and recorded as Ⅰ-Ⅵ according to the number of cases in each cluster. A total of 43 pollutants with high scores of Ⅰ and Ⅱ were listed as the characteristic pollutants, which included 11 polycyclic aromatic hydrocarbons, 11 organochlorine pesticides, 10 polychlorinated biphenyls, eight dioxins, two heavy metals, and one phthalate ester. The top five median concentrations of contaminants in water and sediment samples were heavy metals, polycyclic aromatic hydrocarbons, phthalates esters, bisphenols, and pharmaceuticals and personal care products. According to the principle of risk maximization, the risk entropy value （RQ） was calculated based on the highest pollutant concentration. A total of 38 risky pollutants were screened in the water samples （RQ ≥ 0.1）. There were eight high-risk pollutants with RQ ≥ 1, which included benzo[a,h]-anthracene, anthracene, benzo[a]anthracene, pyrene, methoxychlor, aldrin, 2,4'-dichlorodiphenyl, and cadmium. There were 15 high-risk contaminants in the sediment, which included benzo[b]fluoranthene, anthracene, acenaphthene, fluoranthene, cadmium, lead, chromium, arsenic, selenium, dibutyl phthalate, dimethyl phthalate, diisobutyl phthalate, norfloxacin, perfluorobutyric acid, and bisphenol A. The risk pollutants contained emerging pollutants, which included ten pollutants in water samples and nine pollutants in sediments. Antibiotic pollutants accounted for the largest proportion of these emerging pollutants. The information provided in this article may be useful for the relevant departments to monitor the pollutants and propose management programs for the Yangtze River Basin. Additionally, it is of great significance for the ecological environmental protection and management of the Yangtze River Basin.

Public drinking water contaminant estimates for birth cohorts in the Environmental Influences on Child Health Outcomes (ECHO) Cohort.

The United States Environmental Protection Agency (USEPA) regulates over 80 contaminants in community water systems (CWS), including those relevant to infant health outcomes. Multi-cohort analyses of the association between measured prenatal public water contaminant concentrations and infant health outcomes are sparse in the US. Our objectives were to (1) develop Zip Code Tabulation Area (ZCTA)-level CWS contaminant concentrations for participants in the Environmental Influences on Child Health Outcomes (ECHO) Cohort and (2) evaluate regional, seasonal, and sociodemographic inequities in contaminant concentrations at the ZCTA-level. The ECHO Cohort harmonizes data from over 69 extant pregnancy and pediatric cohorts across the US. We used CWS estimates derived from the USEPA's Six-Year Review 3 (2006-2011) to develop population-weighted, average concentrations for 10 contaminants across 7640 ZCTAs relevant to the ECHO Cohort. We evaluated contaminant distributions, exceedances of regulatory thresholds, and geometric mean ratios (with corresponding percent changes) associated with ZCTA sociodemographic characteristics via spatial lag linear regression models. We observed significant regional variability in contaminant concentrations across the US. ZCTAs were most likely to exceed the maximum contaminant level for arsenic (n = 100, 1.4%) and the health-protective threshold for total trihalomethanes (n = 3584, 64.0%). A 10% higher proportion of residents who were American Indian/Alaskan Native and Hispanic/Latino was associated with higher arsenic (11%, 95% CI: 7%, 15%; and 2%, 95% CI: 0%, 3%, respectively) and uranium (15%, 95% CI: 10%, 21%; and 9%, 95% CI: 6%, 12%, respectively) concentrations. Nationwide epidemiologic analyses evaluating the association between US community water system contaminant concentration estimates and associated adverse birth outcomes in cohort studies are sparse because public water contaminant concentration estimates that can be readily linked to participant addresses are not available. We developed Zip Code Tabulation Area (ZCTA)-level CWS contaminant concentrations that can be linked to participants in the Environmental Influences on Child Health Outcomes (ECHO) Cohort and evaluated regional, seasonal, and sociodemographic inequities in contaminant concentrations for these ZCTAs. Future epidemiologic studies can leverage these CWS exposure estimates in the ECHO Cohort to evaluate associations with relevant infant outcomes.

Drinking Water Contaminant Concentrations and Birth Outcomes.

Previous research in the US has found negative health effects of contamination when it triggers regulatory violations. An important question is whether levels of contamination that do not trigger a health-based violation impact health. We study the impact of drinking water contamination in community water systems on birth outcomes using drinking water sampling results data in Pennsylvania. We focus on the effects of water contamination for births not exposed to regulatory violations. Our most rigorous specification employs mother fixed effects and finds changing from the 10th to the 90th percentile of water contamination (among births not exposed to regulatory violations) increases low birth weight by 12% and preterm birth by 17%.

Sensor with enhanced performance based on photonic crystal with a defect layer

We propose an improved structure of an optical biosensor based on a photonic crystal with a defect layer, which can detect the concentration of organic contaminants in water by defect mode shift. We investigated 4 types of defective photonic crystals with different arrangements of layers inside the perfect photonic crystals and their impact on the performance of the sensor. The sensitivity and amplitude of defect mode were examined as a function of defect layer thickness. Also, the peculiarities of edge modes in the presence of defect layer were investigated. Finally, we obtained a characteristic equation to determine the wavelengths of defect modes for an arbitrary 1D photonic crystal with an isotropic defect inside.

Recalibrating polyparameter linear free energy relationships and reanalyzing mechanisms for partition of nonionic organic compounds to low-density polyethylene passive sampler

Equilibrium passive sampling techniques based on the low-density polyethylene (LDPE) film are increasingly used for determining the concentration of contaminants in water and air. Reliable models capable of predicting LDPE–water and LDPE–air partition coefficients (KiLDPEw and KiLDPEa) would be very useful. In previous studies, polyparameter linear free energy relationships (PP-LFERs) based on Abraham's solute descriptors were calibrated for LDPE–water and LDPE–air systems. Unfortunately, a portion of unreliable partition coefficients and solute descriptors were included in the calibration sets of these previous studies, leading to unexpected system parameters and predictive performance in the regression results. In this study, more reliable PP-LFERs were recalibrated for LDPE–water and LDPE–air systems (20‒25 °C) using carefully collected reliable partition coefficients and solute descriptors of various polar and nonpolar compounds (over one hundred and with low redundancy) from the literature, as well as the robust regression method. The PP-LFERs performed well with root-mean-square errors of 0.15–0.25 log units and successfully predicted KiLDPEw and KiLDPEa values spanning over 10 orders of magnitude for compounds with reliable descriptors. The partitioning mechanisms of compounds to LDPE were also reanalyzed and compared in detail with n-alkanes (C6–C16). Generally, LDPE is more prone to form dispersion interactions with solutes than n-alkanes, while it is more difficult to form cavities in LDPE. In addition, the crystallinity of LDPE is not the sole reason for the distinct constant terms presenting in PP-LFERs for LDPE–water and n-hexadecane–water systems.

Socioeconomic vulnerability and public water arsenic concentrations across the US

Background/Aim: Inorganic arsenic is known human carcinogen and is routinely detected in community water systems (CWSs) across the US. Significant inequalities in CWS arsenic concentrations exist across broad sociodemographic subgroups of the US population. We evaluated the county-level association between socioeconomic vulnerability and CWS arsenic concentrations across the conterminous US. Methods: We evaluated previously developed, population-weighted, county-level CWS arsenic concentrations (2006-2011), the Centers for Disease Control and Prevention’s county-level socioeconomic vulnerability score (range: 0-1), median household income, and the proportion of adults with a high school diploma for 2,604 conterminous US counties. We used spatial lag models and evaluated the adjusted geometric mean ratio (GMR) of county-level CWS arsenic concentrations per interquartile range increase in socioeconomic vulnerability domain and in flexible spline models. We also stratified by region and by United States Department of Agriculture Rural-Urban Continuum Codes to assess potential effect measure modification by region and rurality. Results: Associations between socioeconomic vulnerability and CWS arsenic were modified by region, rurality, and socioeconomic domain. The fully adjusted GMR (95% CIs) of CWS arsenic per interquartile range increase in the proportion of adults with a high school education was 0.83 (0.71, 0.98) or 17% in the Southwest, 0.82 (0.71, 0.94) or 18% in the Eastern Midwest, and 0.65 (0.31, 1.36) or 35% in New England. Higher overall socioeconomic vulnerability was significantly associated with lower CWS arsenic, but only in counties in the Central Midwest and those with total populations less than 20,000. Conclusions: Higher educational attainment was associated with lower CWS arsenic in the Southwest, Eastern Midwest, and New England regions. Findings likely reflect regional/local differences in both socioeconomic/socio-cultural context and regulated drinking water contaminant concentrations. Region-specific analyses at finer geographic resolutions evaluating components of overall socioeconomic vulnerability are needed to adequately characterize the association. arsenic; drinking water; environmental justice

Removal of Urban-Use Insecticides in a Large Open-Water Wetland Pond

Worsening freshwater scarcity has heightened the need for treatment technologies capable of eliminating chemical and biological contaminants to allow for the beneficial use of traditionally underutilized water resources. In urbanized arid and semiarid regions such as California, urban drainage represents an increasingly important water source for augmenting water supply. However, monitoring shows that urban streams are contaminated ubiquitously with urban-use insecticides (e.g., pyrethroids and fipronil) that have broad-spectrum toxicity. In this study, a large open-water wetland pond (OWWP), characterized by shallow water depth and the absence of permanent vegetation, was evaluated for the removal of pyrethroids and fipronil (and its biologically active degradates). Concentration-based removal and changes in the pesticide mass flux were calculated to determine the efficacy of the OWWP. Toxic units for indicator aquatic invertebrates were estimated before and after the OWWP treatment to determine reductions in potential aquatic toxicity. Contaminant concentrations in water and sediment consistently decreased as the water was moving through the OWWP. Concentration-based removals were 44.2–100% for fipronil compounds, 61.8–100% for bifenthrin, and 47.3–92.7% for cyfluthrin, and the removal was attributed to sedimentation, in situ microbial degradation, and photolysis. The mitigation of these urban-use insecticides by the OWWP was similar to that of a densely vegetated constructed wetland at the same site. Therefore, OWWPs represent a low-maintenance and effective wetland configuration for large-scale water reclamation and may be particularly useful for arid and semiarid regions with favorable meteorological conditions (e.g., intense sunshine and high temperature).

Metrologické aspekty v analytické chemii: stanovení kovů ve vodách

The monitoring of water quality in the EU is described in detail and regulated by Directives of the European Commission and the Parliament, which underlines the importance of the quality of water (both potable and non-potable). Analysis of trace concentrations of contaminants in water, including metals, still presents challenges to demonstrate the quality and comparability of results. The article provides a detailed overview of the procedures that laboratories can use to assess the reliability of the results obtained by a particular measurement procedure. Emphasis is placed on three basic pillars: metrological traceability, validation and measurement uncertainty. Subsequently continuous evaluation is carried out using internal and external quality management measures. Regional aspects specific for the Czech Republic are also mentioned.

Automatic optimization of temporal monitoring schemes dealing with daily water contaminant concentration patterns

Online algorithms have been developed to automatically adjust monitoring schemes to sample instants characterized by maximum and/or minimum daily concentrations while reducing sampling costs with respect to traditional monitoring schemes.

Multidecadal biological monitoring and abatement program\ assessing human impacts on aquatic ecosystems within the Oak Ridge Reservation in eastern Tennessee, USA

AbstractHuman activities can be powerful drivers of ecosystem change within catchments. While most long‐term catchment studies have been conducted at pristine sites, such studies are less common from sites more impacted by human activity. The Oak Ridge National Laboratory's Biological Monitoring and Abatement Program (BMAP) was developed in the mid‐1980s to (1) assess compliance with environmental regulations, (2) identify causes of adverse ecological impacts, (3) provide data for human and ecological risk assessments, and (4) evaluate the effectiveness of remedial actions taken to mitigate the impacts of contaminants in soils, groundwater, and surface water by documenting ecological recovery on the Oak Ridge Reservation (ORR), a federally owned 33 476‐acre site in eastern Tennessee, managed by the US Department of Energy. The ORR is composed of multiple watersheds containing many small to mid‐size streams. BMAP uses an integrated approach for determining stream health; its databases include long‐term seasonal records of contaminant concentrations in water and biota, data from aquatic toxicity testing, and surveys of macroinvertebrate and fish assemblages from impacted and reference streams. These long‐term data provide valuable records of degradation and recovery in catchment ecosystems. Our objective here is to describe our study system and data series in order to increase awareness of the availability of these long‐term data to the catchment science community.

Effects of heavy metal contamination released by petrochemical plants on marine life and water quality of coastal areas.

The present study attempts to assess the threat of water contamination in Persian Gulf by heavy metals (Fe, Cr, Pb, Cu, Zn, Cd, Se, and Ni) and its subsequent effects on five fish species including Scomberomorus guttatus (S. guttatus), Lethrinus nebulosus (L. nebulosus), Brachirus orientalis (B. orientalis), Pomadasys kaakan (P. kaakan), and Scomberomorus commerson (S. commerson). Water and fish samples from fourteen monitoring stations were obtained to determine the concentrations of contaminants in water and fish. Heavy metal pollution index (HMPI) and non-carcinogenic hazard quotient (NHQI) were employed to evaluate contamination level in water and fish muscle. The Kriging geostatistical method was employed to determine the spatial distribution of different heavy metals around petrochemical plants. The highest NHQI values for P. kaakan and B. orientalis species were 1.036 and 1.046, respectively. In both cases, the NHQI values were higher than the maximum allowable value of 1, indicating that both fish species were on the verge of contamination by heavy metals, which in turn makes the consumption of these fish highly hazardous to human health. The lowest NHQI value was observed in S. commerson species at a value of 0.394, indicating its harmlessness to human health. Overall, fish species living within the top 5 m of the water column (S. commerson and S. guttatus) were found to be less contaminated by heavy metals compared to species dwelling near the seafloor (P. kaakan and B. orientalis). Results also indicated the pollution absorption rate in S. commerson and S. guttatus were 0.45 and 3.4 mg/kg-year, while the corresponding values for the B. orientalis and L. nebulosus species were 6 and 2 mg/kg-year, respectively. P. kaakan species showed a pollution absorption rate of 3.2 mg/kg-year. High heavy metal concentrations of 4.8, 10, 9.8, 5.2, 9.4, and 6.7 mg/L were obtained for Cr, Zn, Pb, Ni, Fe, Cu, and Cd, respectively, in water samples obtained from stations nearby petrochemical plants. The HMPI index for the most contaminated stations was ten times that of the maximum allowable limit. Given the intense activity of oil, gas, and petrochemical plants in the Persian Gulf, defining safe fishing areas by management practices similar to contamination zoning maps presented in this study can substantially protect the public health from heavy metal contamination.

Zeolite as a natural adsorbent for nitrogenous compounds being removed from water

Water is vital to the survival of humans and all other life forms, yet many sources of freshwater are being contaminated due to pollution, significantly limiting freshwater availability, and threatening human existence. Nitrates and ammonium are common water contaminants whose concentrations in water have increased significantly due to the excessive use of fertilisers. High concentrations of such contaminants in water can lead to multiple health issues, and thus controlling the concentration levels of these pollutants in water grows into the main task for environmental scientists. A natural zeolite filter was employed in this study to minimise traces of contaminants in water. Samples of synthetic polluted water were prepared that contained 50 mg/L of each contaminant for the laboratory tests. Testing natural zeolite doses ranging from 1 to 5 g/L at various pH levels (between 3 and 10) showed that a zeolite filter significantly improved the water quality from the initial concentrations of each pollutant by between 10 and 50 mg/l. In particular, more than 93% of both contaminants (nitrate and ammonium) were removed by using a 5 g/L dose of zeolite in a neutral pH level range for 120 minutes.

Zeolite as a natural adsorbent for nitrogenous compounds removal from water

Water is a vital element to the survival of humans and other life forms. Yet, this source is being contaminated due to pollution leading to significantly limited freshwater, which threatens humans’ existence. Nitrates and ammonium are water contaminants and their concentration has vividly increased owing to their applications as farm nourishments. High concentrations of such contaminants in water can lead to health issues. Thus, controlling the concentration levels of these pollutants in water grows into the main task for environmentalist. Thus, a natural zeolite filter was employed in this study to minimize the traces of contaminants from water. Samples of synthetic water have been prepared and used in the laboratory tests that contain 50 mg/l of each contaminant. Using natural zeolite dose ranged from 1-5 g/l at various pH level (between 3-10) showed that the zeolite filter significantly improved the water quality for initial concentrations of each pollutant ranged from 10 to 50 mg/l. The outcomes showed that more than 93 % of both contaminates (nitrate and ammonium) were separated after using 5 g/l dose of zeolite in neutral pH level range for 120 minutes.

Effect of water contamination on transmissivity behaviour of nonwoven geotextile

Nonwoven geotextiles are one of the most widely used geosynthetic materials in drainage and filtration in geotechnical engineering works and applications. In the present study, drainage property of geotextile fabric with three levels of water contamination (20, 40, and 60 gpl) and with clean water has been studied with the variation of transverse loads (1, 3, 5, and 7 kPa) and fabric mass density (300, 600, and 900 g/m2). Transmissivity of geotextile is found to be lower at higher level of water contamination. The effect of water contamination concentration is higher for fabric with higher mass density. However, the effect of contamination on geotextile material is lower at higher transverse load. The effect of transverse load on transmissivity of geotextile is higher for 300 g/m2 as compared to 600 and 900 g/m2. Although the reduction in transmissivity of fabric with higher mass density (900 g/m2) is higher, still the fabric exhibits better transmissivity behaviour as compared to 300 and 600 g/m2.

Data-driven approaches to advance California’s Human Right to Water Law: Characterizing inequities in drinking water quality among domestic well communities and public drinking water systems

In 2012, California became the first state to recognize the Human Right to Water. However, roughly 10% of California’s public drinking water systems are currently out of compliance with federal and state drinking water quality standards, and an estimated 6 million Californians are served by systems that have been in violation at some point since 2012. A disproportionate number of water quality violations occur in smaller drinking water systems that serve rural, low income communities color, where a lack of resources make it challenging to treat contaminated water and meet regulatory standards. Additionally, significant data gaps exist regarding the location and water quality of unregulated water sources, such as private domestic wells.The UC Berkeley Water Equity Science Shop sought to characterize demographic differences in water quality for communities reliant upon domestic wells and community water systems. We integrated data from the Department of Water Resources; Tracking California’s Drinking Water Systems Geographic Reporting Tool; and the US Census to identify the location of likely domestic well communities across California. Using water quality data from CalEnviroscreen 3.0 and the Groundwater Risk Index Tool, and demographic data from the American Community Survey, we estimate sociodemographic differences in water quality using multivariate analysis.Results indicate that over 1.3 million Californians rely on private wells for drinking water. We estimate 49,000 and 102,000 people live in domestic well areas where drinking water is likely to exceed regulatory standards for nitrates and arsenic, respectively. Average contaminant concentrations of arsenic and nitrate are over 1.5 times higher in areas served by domestic wells than in community water systems. Multivariate statistical models indicate that area-level measures of race/ethnicity and poverty are associated with increases in drinking water contaminant concentrations in domestic well areas.

Ecological causal assessment of benthic condition in the oil sands region, Athabasca River, Canada

Contaminant loads to rivers of the Canadian oil sands region are linked to industrial and natural sources. To date, biomonitoring studies have been unable to unequivocally assess potential environmental impacts associated with this development. As part of the Joint Alberta-Canada Oil Sands Monitoring initiative, we aimed to assess cumulative effects of anthropogenic activities and exposure to natural bitumen geology on benthic macroinvertebrate assemblages in the lower Athabasca River. We examined associations among macroinvertebrates and environmental correlates, such as nutrients, ions, metals, polycyclic aromatic compounds, and total suspended solids. The study design included sites within and outside the mineable bitumen deposits, within and outside of the active mining and extraction area, and above and below municipal sewage effluents. We predicted observing a negative association between ecological condition of the river and exposure to natural bitumen and oil sands activity. However, contaminant concentrations in water and sediment were far below known toxicity thresholds, and benthic macroinvertebrate assemblages in sites exposed to oil sands mining activities appeared more affected by nutrient enrichment from the MSE than contaminants from mining or natural bitumen. Although sites within the area of intense oil sands activity showed signs of mild environmental stress, assemblage pattern was more strongly associated with MSE nutrient enrichment than to diffuse contamination from either natural bitumen or oil sands mining. Enrichment likely increases food resources available to consumers, thereby potentially masking toxic responses of consumers to contaminants. Current regulations prohibit the direct release of oil sands contaminants to waterways, with diffuse atmospheric deposition of aerial emissions and fugitive dust the main contaminant pathways to freshwaters. As the storage capacity of tailings ponds is reached, this nutrient-contaminant pattern could change if the river receives the proposed direct release of treated oil sands process water. Focused investigation-of-cause studies are required to better assess the consequences of cumulative interactions and ecological effects of nutrients and contaminant exposure in this system.

Critical Review: DNA Aptasensors, Are They Ready for Monitoring Organic Pollutants in Natural and Treated Water Sources?

There is a growing need to monitor anthropogenic organic contaminants detected in water sources. DNA aptamers are synthetic single-stranded oligonucleotides, selected to bind to target contaminants with favorable selectivity and sensitivity. These aptamers can be functionalized and are used with a variety of sensing platforms to develop sensors, or aptasensors. In this critical review, we (1) identify the state-of-the-art in DNA aptamer selection, (2) evaluate target and aptamer properties that make for sensitive and selective binding and sensing, (3) determine strengths and weaknesses of alternative sensing platforms, and (4) assess the potential for aptasensors to quantify environmentally relevant concentrations of organic contaminants in water. Among a suite of target and aptamer properties, binding affinity is either directly (e.g., organic carbon partition coefficient) or inversely (e.g., polar surface area) correlated to properties that indicate greater target hydrophobicity results in the strongest binding aptamers, and binding affinity is correlated to aptasensor limits of detection. Electrochemical-based aptasensors show the greatest sensitivity, which is similar to ELISA-based methods. Only a handful of aptasensors can detect organic pollutants at environmentally relevant concentrations, and interference from structurally similar analogs commonly present in natural waters is a yet-to-be overcome challenge. These findings lead to recommendations to improve aptasensor performance.

Application of Least-Squares Support Vector Machines for Quantitative Evaluation of Known Contaminant in Water Distribution System Using Online Water Quality Parameters.

In water-quality, early warning systems and qualitative detection of contaminants are always challenging. There are a number of parameters that need to be measured which are not entirely linearly related to pollutant concentrations. Besides the complex correlations between variable water parameters that need to be analyzed also impairs the accuracy of quantitative detection. In aspects of these problems, the application of least-squares support vector machines (LS-SVM) is used to evaluate the water contamination and various conventional water quality sensors quantitatively. The various contaminations may cause different correlative responses of sensors, and also the degree of response is related to the concentration of the injected contaminant. Therefore to enhance the reliability and accuracy of water contamination detection a new method is proposed. In this method, a new relative response parameter is introduced to calculate the differences between water quality parameters and their baselines. A variety of regression models has been examined, as result of its high performance, the regression model based on genetic algorithm (GA) is combined with LS-SVM. In this paper, the practical application of the proposed method is considered, controlled experiments are designed, and data is collected from the experimental setup. The measured data is applied to analyze the water contamination concentration. The evaluation of results validated that the LS-SVM model can adapt to the local nonlinear variations between water quality parameters and contamination concentration with the excellent generalization ability and accuracy. The validity of the proposed approach in concentration evaluation for potassium ferricyanide is proven to be more than 0.5 mg/L in water distribution systems.

Risk Factors Associated with Mortality of Age-0 Smallmouth Bass in the Susquehanna River Basin, Pennsylvania.

Evidence of disease and mortalities of young of the year (age-0) Smallmouth Bass Micropterus dolomieu has occurred during the late spring and summer in many parts of the Susquehanna River watershed since 2005. To better understand contributing factors, fish collected from multiple areas throughout the watershed as well as out-of-basin reference populations (Allegheny and Delaware River basins; experimental ponds, Kearneysville, West Virginia) were examined grossly and histologically for abnormalities. Tissue contaminant concentrations were determined from whole-body homogenates, and water contaminant concentrations were estimated using time-integrated passive samplers at selected sites. Observed or isolated pathogens included bacteria, predominantly motile Aeromonas spp. and Flavobacterium columnare; largemouth bass virus, and parasites, including trematode metacercariae, cestodes, and the myxozoan Myxobolus inornatus. Although these pathogens were found in age-0 Smallmouth Bass from multiple sites, no one pathogen was consistently associated with mortality. Chemicals detected in tissue included polychlorinated biphenyl (PCB) congeners, organochlorine, and current-use pesticides. Pyraclostrobin, PCB congeners 170 and 187, cis-chlordane and trans-nonachlor were detected in all Susquehanna watershed samples but rarely in samples from the reference site. The findings support the idea that there is no single cause for disease of age-0 Smallmouth Bass; rather the cumulative effects of co-infections and potential immunomodulation by environmental stressors during a sensitive developmental life stage may lead to mortality. Identifying the most important risk factors will be necessary for more in-depth analyses of individual stressors and better management of the habitat and fish populations.

Modeling the Concentration of Volatile and Semivolatile Contaminants in Direct Contact Membrane Distillation (DCMD) Product Water

Direct contact membrane distillation (DCMD) is an emerging water treatment technology that has high salt rejection; however, its commercialization potential for applications such as seawater desalination or industrial wastewater reuse may be limited by low rejection of volatile and semivolatile contaminants. In this manuscript, a contaminant concentration (CC) model describing the transport of volatile and semivolatile contaminants for DCMD systems was developed and validated using data from the bench-scale DCMD treatment of synthetic wastewaters. The DCMD tests showed that the more volatile contaminants (methyl-tert-butyl ether, acetone, pentanone, butanol, and hexanol) accumulated in the permeate collection stream at greater concentrations than in the feed stream. The validated CC model (average normalized root mean squared error ≤11.3%) was then used to evaluate the product water quality from the large-scale DCMD treatment of oil and gas produced waters. The modeled product water contaminant concentrations exceeded the Environmental Protection Agency limits for discharging to publicly owned treatment works. This indicated that DCMD treatment of produced waters may require additional processing to meet discharge requirements.