Ambient Water Quality Criteria Research Articles

Seasonal and animal farm size influences on in-stream phosphorus transport in an agricultural watershed

Excess phosphorus (P) is generally responsible for the eutrophication of Midwestern surface waters and causes algal blooms, fish kills, and other detrimental ecological effects. In-stream transport of dissolved and particulate P (PP), under both stormflow and baseflow conditions, was studied in an agricultural Wisconsin watershed with diverse sizes of animal farm operations. Trends in P losses were compared both on an individual event and seasonal (spring, summer, fall) basis. In-stream P transport was characterized by high PP losses in the spring during periods of relatively little crop cover and high dissolved P losses in the fall, when surface coverage was still present. The majority of P (64–71%) was transported in the spring season during periods of high flow. Presence of high animal density at lower portions of the watershed resulted in increasing downstream P concentration and load (i.e., concentration dilution effects with increasing drainage area were absent). The baseflow TP concentrations were always above the USEPA eutrophication threshold [Ecoregion VII, level III-53: 0.08 mg L−1; (USEPA in Ambient water quality criteria recommendations. Information supporting the development of state and tribal nutrient criteria. Rivers and stream in nutrient ecoregion VII. EPA 822-B-00-018. https://www.epa.gov/sites/production/files/documents/rivers7.pdf, 2000)]. While upland conservation practices are necessary for non-point source pollution control, it is important to ensure that these practices afford protection during the spring time periods when agricultural fields are most vulnerable for offsite movement of sediments and associated constituents.

Revisiting inland hypoxia: diverse exceedances of dissolved oxygen thresholds for freshwater aquatic life.

Water resources in many regions are stressed by impairments resulting from climate change, population growth and urbanization. In the United States (US), water quality criteria (WQC) and standards (WQS) were established to protect surfacewaters and associated designated uses, including aquatic life. In inland waters of the south central US, for example, depressed dissolved oxygen (DO) consistently results in impaired aquatic systems due to noncompliance with DO WQC and WQS. In the present study, we systematically examined currently available DO threshold data for freshwater fish and invertebrates and performed probabilistic aquatic hazard assessments with low DO toxicity data that were used to derive the US Environmental Protection Agency's (EPA) Ambient Water Quality Criteria (AWQC) for DO and newly published information. Aquatic hazard assessments predicted acute invertebrate DO thresholds for Ephemeroptera, Plecoptera, or Trichoptera (EPT) taxa and species inhabiting lotic systems to be more sensitive than fish. For example, these organisms were predicted to have acute low DO toxicity thresholds exceeding the US EPA guidelines 17, 26, 31 and 38% and 13, 24, 30 and 39% of the time at 8.0, 5.0, 4.0 and 3.0mg DO/L, respectively. Based on our analysis, it appears possible that low DO effects to freshwater organisms have been underestimated. We also identified influences of temperature on low DO thresholds and pronounced differences in implementation and assessment of the US EPA AWQC among habitats, seasons, and geographic regions. These results suggest some implemented DO guidelines may adversely affect the survival, growth, and reproduction of freshwater aquatic organisms in a region susceptible to climate change and rapid population growth. Given the global decline of species, particularly invertebrates, low DO threshold information, including sublethal (e.g., reproduction, behavior) responses, for additional species (e.g., mollusks, other invertebrates, warm water fish) across seasons, habitats, and life history stages using consistent experimental designs is needed to support more sustainable environmental assessment efforts and management of biodiversity protection goalsin inland waters.

Seasonal Pollution Characteristics and Source Identification of Polycyclic Aromatic Hydrocarbons and Organochlorine Pesticides in Surface Water of Baiyangdian Lake

Seasonal variations of 17 polycyclic aromatic hydrocarbons(PAHs) and 15 persistent organochlorine pesticides(OCPs) were analyzed during spring and summer in surface water from 12 sampling sites of Baiyangdian lake to elucidate their seasonal pollution characteristics and sources. The results showed that total concentrations of PAHs in surface water of Baiyangdian lake ranged from 35.38 to 88.06 ng·L-1(46.57 ng·L-1 in average) in spring and 25.64 to 301.41 ng·L-1(76.23 ng·L-1 in average) in summer, respectively, and total concentrations of OCPs ranged from 0.69 to 4.50 ng·L-1(1.77 ng·L-1 in average) in spring and 0.11 to 3.20 ng·L-1(0.90 ng·L-1 in average) in summer, respectively. Seasonal pollution characteristics of PAHs in surface water during two different seasons showed that the total concentration of PAHs was much higher in summer than in spring at three sampling sites of Baiyangdian lake including Qiantang, Guancheng and Anxin bridge, and the level of PAHs in spring was much higher than that in summer at the other nine sites. While seasonal pollution characteristics of OCPs showed that the total concentration of OCPs was much higher in summer than in spring in samples of Guancheng sites, and the level of OCPs in spring was slightly higher than that in summer in the rest of samples. From the perspective of spatial and temporal variations in the composition patterns of PAHs and OCPs in surface water of Baiyangdian lake, PAHs were predominated by 3-ring PAHs with 45.92% and 61.36%(52.60% in average) of total PAHs in spring, while in summer Nap was the chief component of 2-ring PAHs in three sampling sites including Qiantang, Guancheng and Anxin bridge with 84.91%, 91.04% and 78.10% of the total, respectively, and 3-ring PAHs were primary pollutants in the other nine sites with 37.14% to 53.90%(48.94% in average) of the total. Residues of HCHs and DDTs were detected in different degrees and β-HCH was the main pollutant at all sampling sites with 29.94% and 100%(59.87% in average) of total HCHs in spring, while β-HCH was the predominant compounds at five sampling sites with 57.55% and 80.23%(61.98% in average) in summer and α-HCHs and δ-HCH were abundant at other sampling sites. Source analysis based on isomer ratios indicated that the main source of PAHs in Baiyangdian lake originated from combustion sources, and additional sources for several sampling sites could be petroleum processes. Ratios of HCH isomers and DDT congeners confirmed that environmental historical residues and long range atmospheric transport were the major sources of OCPs contamination in the study area. Compared with the water quality standard of China and other countries or organizations, concentrations of PAHs and OCPs in surface water of Baiyangdian lake did not exceed the target values of the standard. However, the concentrations of α-HCH and p,p'-DDD in Anxin bridge and Quantou sites exceeded the limit of human health ambient water quality criteria developed by EPA, which reflected that α-HCH and p,p'-DDD would have a potential hazards risk to the residents from Baiyangdian district.

Acute sensitivity of a broad range of freshwater mussels to chemicals with different modes of toxic action.

Freshwater mussels, one of the most imperiled groups of animals in the world, are generally underrepresented in toxicity databases used for the development of ambient water quality criteria and other environmental guidance values. Acute 96-h toxicity tests were conducted to evaluate the sensitivity of 5 species of juvenile mussels from 2 families and 4 tribes to 10 chemicals (ammonia, metals, major ions, and organic compounds) and to screen 10 additional chemicals (mainly organic compounds) with a commonly tested mussel species, fatmucket (Lampsilis siliquoidea). In the multi-species study, median effect concentrations (EC50s) among the 5 species differed by a factor of ≤2 for chloride, potassium, sulfate, and zinc; a factor of ≤5 for ammonia, chromium, copper, and nickel; and factors of 6 and 12 for metolachlor and alachlor, respectively, indicating that mussels representing different families or tribes had similar sensitivity to most of the tested chemicals, regardless of modes of action. There was a strong linear relationship between EC50s for fatmucket and the other 4 mussel species across the 10 chemicals (r2 = 0.97, slope close to 1.0), indicating that fatmucket was similar to other mussel species; thus, this commonly tested species can be a good surrogate for protecting other mussels in acute exposures. The sensitivity of juvenile fatmucket among different populations or cultured from larvae of wild adults and captive-cultured adults was also similar in acute exposures to copper or chloride, indicating captive-cultured adult mussels can reliably be used to reproduce juveniles for toxicity testing. In compiled databases for all freshwater species, 1 or more mussel species were among the 4 most sensitive species for alachlor, ammonia, chloride, potassium, sulfate, copper, nickel, and zinc; therefore, the development of water quality criteria and other environmental guidance values for these chemicals should reflect the sensitivity of mussels. In contrast, the EC50s of fatmucket tested in the single-species study were in the high percentiles (>75th) of species sensitivity distributions for 6 of 7 organic chemicals, indicating mussels might be relatively insensitive to organic chemicals in acute exposures. Environ Toxicol Chem 2017;36:786-796. Published 2016 Wiley Periodicals, Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.

A statistical assessment of pesticide pollution in surface waters using environmental monitoring data: Chlorpyrifos in Central Valley, California

Pesticides are routinely monitored in surface waters and resultant data are analyzed to assess whether their uses will damage aquatic eco-systems. However, the utility of the monitoring data is limited because of the insufficiency in the temporal and spatial sampling coverage and the inability to detect and quantify trace concentrations. This study developed a novel assessment procedure that addresses those limitations by combining 1) statistical methods capable of extracting information from concentrations below changing detection limits, 2) statistical resampling techniques that account for uncertainties rooted in the non-detects and insufficient/irregular sampling coverage, and 3) multiple lines of evidence that improve confidence in the final conclusion. This procedure was demonstrated by an assessment on chlorpyrifos monitoring data in surface waters of California's Central Valley (2005–2013). We detected a significant downward trend in the concentrations, which cannot be observed by commonly-used statistical approaches. We assessed that the aquatic risk was low using a probabilistic method that works with non-detects and has the ability to differentiate indicator groups with varying sensitivity. In addition, we showed that the frequency of exceedance over ambient aquatic life water quality criteria was affected by pesticide use, precipitation and irrigation demand in certain periods anteceding the water sampling events.

Scientific Review of Cyanide Ecotoxicology and Evaluation of Ambient Water Quality Criteria

The USEPA's ambient water quality criteria (AWQC) for cyanide were developed in 1984. Recently, however, concerns have arisen that the AWQC for cyanide have been problematic to implement and may not accurately reflect either the toxic forms or bioavailable concentrations of cyanide in water, sediments, and tissues of aquatic organisms. Also, the cyanide criteria typically have been implemented based on total cyanide concentrations rather than the free cyanide concentrations that formed the basis of the criteria calculations. New knowledge on cyanide toxicity, cyanide speciation and its measurement, and the relative toxicity of bioavailable cyanide species suggested that a re-evaluation of the aquatic toxicity data and chemistry that serve as the basis of the current national criteria is warranted. In response to these concerns, studies sponsored by the Water Environment Research Foundation (WERF) evaluated the formation and fate of cyanide in municipal wastewater effluents. Kavanaugh et al. (2003) evaluated the reliability of several analytical methods for measurement of cyanide species at low (ppb) concentrations, along with studies to evaluate the sources, transport, and fate of cyanide species in wastewater treatment plants (WWTPs) and receiving waters. Results indicated that potentially toxic forms of cyanide can be generated in WWTPs from several chemical processes, including dissociation of thiocyanate by chlorination or UV disinfection, chlorination in the presence of residual ammonia, nitrosation, and photolysis of ferrocyanate. Models were developed for predicting the fate of these compounds in surface waters downstream of WWTP effluents to establish where organisms might be most at risk from cyanide exposure. While implementation of these results could assist in the development of site-specific water quality standards for cyanide, a more thorough update to the National AWQC was warranted to apply our more current scientific understanding of cyanide toxicology to the derivation of aquatic life criteria. The present study was therefore undertaken to review and update knowledge of the aquatic toxicity of cyanide, and to develop recommended updates to the existing national AWQC to enhance the scientific basis of the concentrations and chemical forms of cyanide specified for protection of aquatic organisms. This update was conducted according to USEPA guidance for derivation of AWQC for protection of aquatic life, and is based both on an extensive literature review and on new toxicity studies that fill key data gaps. This re-evaluation of cyanide criteria also includes consideration of impacts on benthic (sediment) organisms, wildlife that consume aquatic biota, and possible effects to threatened and endangered species to ensure that revised criteria are adequately protective of the entire aquatic ecosystem. This title belongs to WERF Research Report Series ISBN: 9781843397533 (Print) ISBN: 9781780403755 (eBook)

Bioavailability and Effects of Ingested Metals on Aquatic Organisms

Laboratory toxicity studies and a caged bivalve field study complemented by computer modeling were conducted to investigate the significance of effects on aquatic organisms due to dietary exposure to metals. The lab studies were performed with saltwater and freshwater organisms. The saltwater studies provided partial support for previous research that showed dietary effects could occur when the food source, a mono-algal culture, was loaded with Ag, Cu, Ni or Zn at dissolved metal concentrations below than the current ambient water quality criteria (WQC). However, in contrast to the earlier studies, continuous 7-day exposures to Ag rather than a 4-hour pulse exposure were required to elicit a response by Acartia tonsa. The effects concentrations were also much higher than in the earlier studies and slightly higher than the proposed chronic water quality criteria (WQC) for Ag. The three other metals were only tested under a continuous-exposure regime and yielded similar test results to Ag, though the dissolved concentrations in which the algae were cultured were below the current chronic saltwater WQC. In the freshwater studies performed with Ceriodaphnia dubia exposed to dietary Cu and Ag, reproductive impairment was not consistent among repeat tests. Variations in reproductive vitality of the C. dubia might have contributed to the variability in adverse responses by the organisms. Questions remain regarding the applicability of the saltwater and freshwater results to field conditions, where mitigating factors such as a more nutritional mixed-algal diet or increased metal complexation capacity could decrease the amount of the bioavailable form of the metals, thereby decreasing exposure and effects. This title belongs to WERF Research Report Series ISBN: 9781843397656 (eBook)

Developing Ambient Water Quality Criteria for Mercury: A Probabilistic Site-Specific Approach

This project examined the development of ambient water quality criteria (AWQC) for the protection of wildlife for mercury. Mercury is considered a serious risk to wildlife in many areas. As a result, the Great Lakes Water Quality Initiative and others have developed AWQC. These AWQC have been controversial, however, because (1) the AWQC were single values that did not account for site-specific conditions; (2) derivation of the AWQC relied on a single NOAEL, and (3) the AWQC had an unknown level of conservatism because of reliance on both average and conservative assumptions and uncertainty factors. Rather than develop a single value AWQC for total mercury, we derive an AWQC model that explicitly incorporates factors controlling bioavailability, methylation rates and bioaccumulation in the aquatic environment (e.g., pH, DOC, sulfate). To derive our AWQC model, field data was collected including numerous water quality parameters and total mercury and methylmercury concentrations in whole body fish tissue from 31 lakes in Ontario and an additional 10 lakes in Nova Scotia. An independent dataset consisting of 51 water bodies in the United States was then used to confirm the validity and robustness of the AWQC model. Next we combined the results of chronic-feeding studies with similar protocols and endpoints, in a meta-analysis to derive a dose-response curve for mink exposed to mercury in the diet. Using this approach, one can derive an LD5 or other similar endpoint that can then be used as the basis for deriving -wildlife AWQC. In the final step, we used a probabilistic risk model to estimate the concentrations of methylmercury in water that would lead to levels in fish sufficient for there to be a 10% probability of exceeding the mink LD5. This analysis was repeated for various combinations of pH and DOC. The result is an AWQC model for mercury for the protection of wildlife that can be used for a variety of site-specific conditions. This title belongs to WERF Research Report Series ISBN: 9781843396376 (Print) ISBN: 9781780404028 (eBook)

Nickel and Copper Toxicity to Embryos of the Long-Spined Sea Urchin, Diadema savignyi.

The sensitivity of long-spined sea urchins (Diadema savignyi) collected from Guam (Northern Marianas Islands), USA, to nickel and copper in seawater was explored using 48-h embryo-larval development toxicity tests. The median effective concentrations (EC50) averaged 94 µg L(-1) for nickel, and 19 µg L(-1) from a single exposure to copper, and suggest relatively high sensitivity of this species to nickel compared with other sea urchin genera, but similar sensitivity to copper. Ambient nickel and copper concentrations concurrently sampled from 16 near-shore locations around Guam were one to two orders of magnitude lower than those that would be expected to result in adverse effects to D. savignyi embryos. Although nationally recommended chronic ambient water quality criteria, currently 8.2 and 3.1 µg L(-1) for nickel and copper, respectively, were not exceeded, recently derived qualifying toxicity data should be considered for updating these criteria to ensure protectiveness of sensitive tropical species.

Derivation of human health-based ambient water quality criteria: a consideration of conservatism and protectiveness goals.

Under the terms of the Clean Water Act, criteria for the protection of human health (Human Health Ambient Water Quality Criteria [HHWQC]) are traditionally derived using equations recommended by the US Environmental Protection Agency (USEPA) that include parameters for exposure assessment. To derive "adequately protective" HHWQC, USEPA proposes the use of default values for these parameters that are a combination of medians, means, and percentile estimates targeting the high end (90th percentile) of the general population. However, in practice, in nearly all cases, USEPA's recommended default assumptions represent upper percentiles. This article considers the adequacy of the exposure assessment component of USEPA-recommended equations to yield criteria that are consistent with corresponding health protection targets established in USEPA recommendations or state policies, and concludes that conservative selections for exposure parameters can result in criteria that are substantially more protective than the health protection goals for HHWQC recommended by USEPA, due in large part to the compounding effect that occurs when multiple conservative factors are combined. This situation may be mitigated by thoughtful selection of exposure parameter values when using a deterministic approach, or by using a probabilistic approach based on data distributions for many of these parameters.

A Preliminary Laboratory Investigation of PCB Flux from Dredge Resuspensions and Residuals

A preliminary laboratory investigation was conducted to understand the relative contributions of major dredge resuspension and residual processes on the releases of polychlorinated biphenyl (PCB) contaminants from sediments to water column. Sediments from New Bedford Harbor were used as test samples. Six sets of experiments were run for simulated resuspension and residual scenarios. During the experiments, water above the sediments was recirculated by peristaltic pumping or orbital shaking and the levels of two PCBs, Aroclor 1248 (PCB-1248) and Aroclor 1254 (PCB-1254), were monitored for 15 days. Analysis of the model predicted data indicated that resulting water column PCB concentrations differed with sediment surface, residual, and resuspension type. Highest PCB water column concentrations were observed for a condition which used a settled fluff from thin sediment slurry as a residual source and the column water was recirculated by orbital shaking. Lowest water column PCB levels were observed for a thick sediment deposit placed over clean sand. The PCB levels in the water column for all six simulated conditions were several orders higher than the USEPA ambient water quality criteria concentrations for aquatic environment and human consumption.

Chronic sensitivity of white sturgeon (Acipenser transmontanus) and rainbow trout (Oncorhynchus mykiss) to cadmium, copper, lead, or zinc in laboratory water-only exposures.

Chronic toxicity of cadmium, copper, lead, or zinc to white sturgeon (Acipenser transmontanus) and rainbow trout (Oncorhynchus mykiss) was evaluated in water-only exposures started with newly hatched larvae or approximately 1-mo-old juveniles. The 20% effect concentration (EC20) for cadmium from the sturgeon tests was higher than the EC20 from the trout tests, whereas the EC20 for copper, lead, or zinc for the sturgeon were lower than those EC20s for the trout. When the EC20s from the present study were included in compiled toxicity databases for all freshwater species, species mean chronic value for white sturgeon was in a relatively low percentile of the species sensitivity distribution for copper (9th percentile) and in the middle percentile for cadmium (55th percentile), zinc (40th percentile), or lead (50th percentile). However, the species mean chronic value for rainbow trout was in a high percentile for copper, lead, and zinc (∼68th-82nd percentile), but in a low percentile for cadmium (23rd percentile). The trout EC20s for each of the 4 metals and the sturgeon EC20s for cadmium or lead were above US Environmental Protection Agency chronic ambient water quality criteria (AWQC) or Washington State chronic water quality standards (WQS), whereas the sturgeon EC20s for copper or zinc were approximately equal to or below the chronic AWQC and WQS. In addition, acute 50% effect concentrations (EC50s) for copper obtained in the first 4 d of the chronic sturgeon test were below the final acute value used to derive acute AWQC and below acute WQS for copper.

Simultaneous removal of oil and grease, and heavy metals from artificial bilge water using electro-coagulation/flotation

US and international regulations pertaining to the control of bilge water discharges from ships have concentrated their attention to the levels of oil and grease rather than to the heavy metal concentrations. The consensus is that any discharge of bilge water (and oily water emulsion within 12 nautical miles from the nearest land cannot exceed 15 parts per million (ppm). Since there is no specific regulation for metal pollutants under the bilge water section, reference standards regulating heavy metal concentrations are taken from the ambient water quality criteria to protect aquatic life.The research herein presented discusses electro-coagulation (EC) as a method to treat bilge water, with a focus on oily emulsions and heavy metals (copper, nickel and zinc) removal efficiency. Experiments were run using a continuous flow reactor, manufactured by Ecolotron, Inc., and a synthetic emulsion as artificial bilge water. The synthetic emulsion contained 5000 mg/L of oil and grease, 5 mg/L of copper, 1.5 mg/L of nickel, and 2.5 mg/l of zinc. The experimental results demonstrate that EC is very efficient in removing oil and grease. For oil and grease removal, the best treatment and cost efficiency was obtained when using a combination of carbon steel and aluminum electrodes, at a detention time less than one minute, a flow rate of 1 L/min and 0.6 A/cm2 of current density. The final effluent oil and grease concentration, before filtration, was always less than 10 mg/L.For heavy metal removal, the combination of aluminum and carbon steel electrodes, flow rate of 1 L/min, effluent recycling, and 7.5 amps produced 99% zinc removal efficiency. Copper and nickel are harder to remove, and a removal efficiency of 70% was achieved.

A Preliminary Laboratory Study of Initial Copper Release from Dredge Residuals

A preliminary laboratory study was conducted to investigate the impact of different residual types and sediment surface roughness on copper contaminant fluxes to the water column. Sediments from Torch Lake, Michigan served as the test samples. These sediments are mining by‐products with elevated Cu levels. Six experiments were run during which the sediments were conditioned to simulate different forms of residuals. During these experiments, the water column above the sediments was circulated via peristaltic pumping or orbital shaking and the total and dissolved Cu levels were monitored periodically for 15 days. Dissolved Cu levels indicated that during the first 48 hr the water column concentrations approached equilibrium for all six cases. Total Cu levels increased with time and did reach equilibrium but were more susceptible to fluctuations in water column suspended solids levels. Analysis of the resulting dissolved Cu data indicated that the resulting water column Cu concentrations differed with sediment surface and residual type. The highest dissolved Cu water column concentrations were observed for a roughened surface with a larger surface area. The lowest water column dissolved Cu levels were observed for the case with sediment slurry placed over clean sand. The dissolved Cu levels in the water column for all six simulated conditions were several orders higher than the USEPA ambient water quality criteria for protection of aquatic life. © 2014 Wiley Periodicals, Inc.*

The impact of recent advances in research on arsenic cancer risk assessment

Scientific debate surrounds the regulatory approach for evaluating carcinogenic risk of arsenic compounds. The arsenic ambient water quality criteria (AWQC), based on the assumption of a linear mode of action for skin cancer risk, results in an allowable limit of 0.018ppb in ambient waters; the drinking water Maximum Contaminant Level (MCL) was determined using a similar linear approach. Integration of results from recent studies investigating arsenic’s mode of action provide the basis for a change in the approach for conducting an arsenic cancer risk assessment. Results provide support for a concentration demonstrating a dose-dependent transition in response from those representing adaptive changes to those that may be key events in the development of cancer endpoints. While additional information is needed, integration of current research results provides insight for a new quantitative cancer risk assessment methodology as an alternative toxicologically-based dose response (BBDR) cancer modeling. Integration of the new experimental results, combined with epidemiological evidence, support a dose-dependent transition concentration of approximately 0.1μM arsenic. Some uncertainties remain; additional information from chronic in vitro studies underway is needed. Results to date also provide initial insight into variability in population response at low arsenic exposures.

Meeting the Needs of the People: Fish Consumption Rates in the Pacific Northwest

Meeting the Needs of the People: Fish Consumption Rates in the Pacific Northwest

Deriving Chesapeake Bay Water Quality Standards

AbstractAchieving and maintaining the water quality conditions necessary to protect the aquatic living resources of the Chesapeake Bay and its tidal tributaries has required a foundation of quantifiable water quality criteria. Quantitative criteria serve as a critical basis for assessing the attainment of designated uses and measuring progress toward meeting water quality goals of the Chesapeake Bay Program partnership. In 1987, the Chesapeake Bay Program partnership committed to defining the water quality conditions necessary to protect aquatic living resources. Under section 303(c) of the Clean Water Act, States and authorized tribes have the primary responsibility for adopting water quality standards into law or regulation. The Chesapeake Bay Program partnership worked with U.S. Environmental Protection Agency to develop and publish a guidance framework of ambient water quality criteria with designated uses and assessment procedures for dissolved oxygen, water clarity, and chlorophyll a for Chesapeake Bay and its tidal tributaries in 2003. This article reviews the derivation of the water quality criteria, criteria assessment protocols, designated use boundaries, and their refinements published in six addendum documents since 2003 and successfully adopted into each jurisdiction's water quality standards used in developing the Chesapeake Bay Total Maximum Daily Load.

A novel fractionation approach for water constituents – distribution of storm event metals

A novel fractionation method, based on both particle size and settling characteristics, was employed to examine metal distributions among five fractions. In-stream and stormwater runoff samples were collected from four land use types: highway, urban, agricultural (storm event and irrigation), and natural. Highway samples contained the highest dissolved concentrations for most metals, and freshwater ambient water quality criteria were exceeded for Cd, Cu, Pb, and Zn in the first storm of the water year. Anthropogenic sources were indicated for Cu, Zn, Cd, and Pb in highway and urban samples, and total metal loadings (mg km(-2)) were observed to be as follows: highway > urban > agricultural storm event ∼ natural > agricultural irrigation. Notably, ∼10-fold higher suspended solids concentration was observed in the agricultural storm event sample, and suspended solids-associated metals were correspondingly elevated. Distribution coefficients revealed the following affinities: Zn, Ni, Cd, and Pb to large dense particles; and Cu, Zn, Cr, Ni, and Pb to colloidal organic matter.

Water Quality Standards: A Scientific and Theological-Ethical Analysis

Water Quality Standards: A Scientific and Theological-Ethical Analysis

Passive Sampling to Measure Baseline Dissolved Persistent Organic Pollutant Concentrations in the Water Column of the Palos Verdes Shelf Superfund Site

Passive sampling was used to deduce water concentrations of persistent organic pollutants (POPs) in the vicinity of a marine Superfund site on the Palos Verdes Shelf, California, USA. Precalibrated solid phase microextraction (SPME) fibers and polyethylene (PE) strips that were preloaded with performance reference compounds (PRCs) were codeployed for 32 d along an 11-station gradient at bottom, surface, and midwater depths. Retrieved samplers were analyzed for DDT congeners and their breakdown products (DDE, DDD, DDMU, and DDNU) and 43 PCB congeners using GC-EI- and NCI-MS. PRCs were used to calculate compound-specific fractional equilibration achieved in situ for the PE samplers, using both an exponential approach to equilibrium (EAE) and numerical integration of Fickian diffusion (NI) models. The highest observed concentrations were for p,p'-DDE, with 2200 and 990 pg/L deduced from PE and SPME, respectively. The difference in these estimates could be largely attributed to uncertainty in equilibrium partition coefficients, unaccounted for disequilibrium between samplers and water, or different time scales over which the samplers average. The concordance between PE and SPME estimated concentrations for DDE was high (R(2) = 0.95). PCBs were only detected in PE samplers, due to their much larger size. Near-bottom waters adjacent to and down current from sediments with the highest bulk concentrations exhibited aqueous concentrations of DDTs and PCBs that exceeded Ambient Water Quality Criteria (AWQC) for human and aquatic health, indicating the need for future monitoring to determine the effectiveness of remedial activities taken to reduce adverse effects of contaminated surface sediments.