Current Water Quality Criteria Research Articles

Turbid Waters and Clearer Standards: Refining Water Quality Criteria for Coastal Environments by Encompassing Metal Bioavailability from Suspended Particles.

Suspended particulate matter (SPM) carries a major fraction of metals in turbid coastal waters, markedly influencing metal bioaccumulation and posing risks to marine life. However, its effects are often overlooked in current water quality criteria for metals, primarily due to challenges in quantifying SPM's contribution. This contribution depends on the SPM concentration, metal distribution coefficients (Kd), and the bioavailability of SPM-bound metals (assimilation efficiency, AE), which can collectively be integrated as a modifying factor (MF). Accordingly, we developed a new stable isotope method to measure metal AE by individual organisms from SPM, employing the widely distributed filter-feeding clam Ruditapes philippinarum as a representative species. Assessing SPM from 23 coastal sites in China, we found average AEs of 42% for Zn, 26% for Cd, 20% for Cu, 8% for Ni, and 6% for Pb. Moreover, using stable isotope methods, we determined metal Kd of SPM from these sites, which can be well predicted by the total organic carbon and iron content (R2 = 0.977). We calculated MFs using a Monte Carlo method. The calculated MFs are in the range 9.9-43 for Pb, 8.5-37 for Zn, 2.9-9.7 for Cu, 1.4-2.7 for Ni, and 1.1-1.6 for Cd, suggesting that dissolved-metal-based criteria values should be divided by MFs to provide adequate protection to aquatic life. This study provides foundational guidelines to refine water quality criteria in turbid waters and protect coastal ecosystems.

Consistent declines in aquatic biodiversity across diverse domains of life in rivers impacted by surface coal mining.

The rivers of Appalachia (United States) are among the most biologically diverse freshwater ecosystems in the temperate zone and are home to numerous endemic aquatic organisms. Throughout the Central Appalachian ecoregion, extensive surface coal mines generate alkaline mine drainage that raises the pH, salinity, and trace element concentrations in downstream waters. Previous regional assessments have found significant declines in stream macroinvertebrate and fish communities after draining these mined areas. Here, we expand these assessments with a more comprehensive evaluation across a broad range of organisms (bacteria, algae, macroinvertebrates, all eukaryotes, and fish) using high-throughput amplicon sequencing of environmental DNA (eDNA). We collected water samples from 93 streams in Central Appalachia (West Virginia, United States) spanning a gradient of mountaintop coal mining intensity and legacy to assess how this land use alters downstream water chemistry and affects aquatic biodiversity. For each group of organisms, we identified the sensitive and tolerant taxa along the gradient and calculated stream specific conductivity thresholds in which large synchronous declines in diversity were observed. Streams below mining operations had steep declines in diversity (-18 to -41%) and substantial shifts in community composition that were consistent across multiple taxonomic groups. Overall, large synchronous declines in bacterial, algal, and macroinvertebrate communities occurred even at low levels of mining impact at stream specific conductivity thresholds of 150-200 µS/cm that are substantially below the current U.S. Environmental Protection Agency aquatic life benchmark of 300 µS/cm for Central Appalachian streams. We show that extensive coal surface mining activities led to the extirpation of 40% of biodiversity from impacted rivers throughout the region and that current water quality criteria are likely not protective for many groups of aquatic organisms.

Is metal flocculation from mining activities a previously overlooked mechanism for impairing freshwater ecosystems?

Ecological effects of mining activity are a global concern; with most studies ascribing the effect on freshwater biota to metal toxicity from metal uptake through dietary or dissolved metal exposure. Although the potential for smothering effects from metal flocs has been suggested, studies have not separated metal toxicity effects and smothering effects from metal flocs on stream macroinvertebrates. We analysed traits of stream macroinvertebrates hypothesised to be sensitive to metal flocs (caused by its smothering effects) and metal toxicity (through metal uptake from dietary and dissolved metal exposure). We analysed data from sites receiving (test sites) and not receiving (reference sites) metal pollution from a disused mine to determine the primary mechanism for biotic impairment (e.g. smothering by metal flocs or metal toxicity). We found macroinvertebrates with traits associated with fine-sediment sensitivity (e.g. traits such as exposed gills) were less abundant at the test sites compared with the reference sites. The differences in the macroinvertebrate traits were consistent with smothering from metal flocs being the chief mechanism by which metals were affecting the macroinvertebrate community at the test sites and inconsistent with metal toxicity being the primary cause. Current water quality criteria only consider metal pollution in terms of toxicity to aquatic life. Yet our findings show that smothering effects from metal flocs can cause significant biological impairment.

An integrative methodological framework for setting environmental criteria: Evaluation of stakeholder perceptions

In water quality management, delisting decisions for impaired waterbodies bear resemblance to the statistical null hypothesis testing in which the prevailing conditions in the system at hand are compared against a reference (or non-impaired) state. This binary comparison presupposes the existence of a robust delineation of what constitutes a non-impaired state along with the establishment of threshold values for key environmental variables that act as surrogates for the degree of system impairment. Drawing the dichotomy between impaired and non-impaired conditions can be a challenging exercise, as it can be influenced by different trade-offs between environmental priorities and socioeconomic values. In this study, we present an integrative methodological framework that first uses mathematical modelling to reproduce the fundamental relationships between external stressors and ecosystem response and then statistically links the projected patterns with the likelihood to achieve acceptable water quality conditions. Our case study is the Bay of Quinte, Ontario, Canada; an embayment at the northeastern end of Lake Ontario with a long history of eutrophication. Our survey was conducted during the winter and spring of 2014 and included a total of 51 individuals who were actively involved with the Bay of Quinte Remedial Action Plan. Our analysis found that there is a perceptual difference between public and experts in that the latter group tends to more favorably characterize the present conditions, but is also more conservative about the delisting prospects of the system. Statistical analysis showed an average level of confidence lower than 50% about the delisting likelihood when experts were asked to assess the current water quality criteria. We conclude by arguing that the occurrence frequency of extreme conditions (i.e., exceedance of maximum allowable nutrient levels and/or toxic algal blooms) should be an integral component of the delisting process.

Effects of nitrogenous wastes on survival of the Barton Springs salamander (Eurycea sosorum).

The objective of our study was to determine the acute toxicity of 3 common aquatic nitrogenous toxicants to the federally endangered Barton Springs salamander (Eurycea sosorum). Based on our findings, the 96-h median lethal concentrations (96-h LC50) for un-ionized ammonia-N, nitrite-N, and nitrate-N to E. sosorum are 2.0 ± 0.32, 31.7 ± 4.02, and 968.5 ± 150.6 mg/L, respectively. These results establish a benchmark for the tolerance of plethodontid salamanders to these toxicants and indicate that current water quality criteria are adequate for their protection. Environ Toxicol Chem 2017;36:3003-3007. © 2017 SETAC.

Determination of water environment standards based on water quality criteria in China: Limitations and feasibilities

There is a need to formulate water environment standards (WESs) from the current water quality criteria (WQC) in China. To this end, we briefly summarize typical mechanisms applied in several countries with longer histories of developing WESs, and three limitations to formulating WESs in China were identified. After analyzing the feasibility factors including economic development, scientific support capability and environmental policies, we realized that China is still not ready for a complete change from its current nation-wide unified WES system to a local-standard-based system. Thus, we proposed a framework for transformation from WQC to WESs in China. The framework consists of three parts, including responsibilities, processes and policies. The responsibilities include research authorization, development of guidelines, and collection of information, at both national and local levels; the processes include four steps and an impact factor system to establish water quality standards; and the policies include seven specific proposals.

Human health risk implications of multiple sources of faecal indicator bacteria in a recreational waterbody

We simulate the influence of multiple sources of enterococci (ENT) as faecal indicator bacteria (FIB) in recreational water bodies on potential human health risk by considering waters impacted by human and animal sources, human and non-pathogenic sources, and animal and non-pathogenic sources. We illustrate that risks vary with the proportion of culturable ENT in water bodies derived from these sources and estimate corresponding ENT densities that yield the same level of health protection that the recreational water quality criteria in the United States seeks (benchmark risk). The benchmark risk is based on epidemiological studies conducted in water bodies predominantly impacted by human faecal sources. The key result is that the risks from mixed sources are driven predominantly by the proportion of the contamination source with the greatest ability to cause human infection (potency), not necessarily the greatest source(s) of FIB. Predicted risks from exposures to mixtures comprised of approximately 30% ENT from human sources were up to 50% lower than the risks expected from purely human sources when contamination is recent and ENT levels are at the current water quality criteria levels (35 CFU 100 mL-1). For human/non-pathogenic, human/gull, human/pig, and human/chicken faecal mixtures with relatively low human contribution, the predicted culturable enterococci densities that correspond to the benchmark risk are substantially greater than the current water quality criteria values. These findings are important because they highlight the potential applicability of site specific water quality criteria for waters that are predominantly un-impacted by human sources.

Copper bioavailability and toxicity to Mytilus galloprovincialis in Shelter Island Yacht Basin, San Diego, CA

The bioavailability and toxicity of copper (Cu) in Shelter Island Yacht Basin (SIYB), San Diego, CA, USA, was assessed with simultaneous toxicological, chemical, and modeling approaches. Toxicological measurements included laboratory toxicity testing with Mytilus galloprovincialis (Mediterranean mussel) embryos added to both site water (ambient) and site water spiked with multiple Cu concentrations. Chemical assessment of ambient samples included total and dissolved Cu concentrations, and Cu complexation capacity measurements. Modeling was based on chemical speciation and predictions of bioavailability and toxicity using a marine Biotic Ligand Model (BLM). Cumulatively, these methods assessed the natural buffering capacity of Cu in SIYB during singular wet and dry season sampling events. Overall, the three approaches suggested negligible bioavailability, and isolated observed or predicted toxicity, despite an observed gradient of increasing Cu concentration, both horizontally and vertically within the water body, exceeding current water quality criteria for saltwater.

Field surveys can support ecological risk assessment

Field surveys can support ecological risk assessment

Effect of Organic Complexation on Copper Accumulation and Toxicity to the Estuarine Red Macroalga Ceramium tenuicorne: A Test of the Free Ion Activity Model

Current water quality criteria (WQC) regulations on copper toxicity to biota are still based on total dissolved (<0.4 μm membrane filter) copper concentrations with a hardness modification for freshwaters. There are however ongoing efforts to incorporate metal speciation in WQC and toxicity regulations (such as the biotic ligand model-BLM) for copper and other metals. Here, we show that copper accumulation and growth inhibition of the Baltic macroalga Ceramium tenuicorne exposed to copper in artificial seawater at typical coastal and estuarine DOC concentrations (similar to 2-4 mg/L-C as fulvic acid) are better correlated to weakly complexed and total dissolved copper concentrations rather than the free copper concentration [Cu2+]. Our results using a combination of competitive ligand exchange-adsorptive cathodic stripping voltammetry (CLE-ACSV) measurements and model calculations (using visual MINTEQ incorporating the Stockholm Humic Model) show that copper accumulation in C. tenuicorne only correlates linearly well to [Cu2+] at relatively high [Cu2+] and in the absence of fulvic acid. Thus the FIAM fails to describe copper accumulation in C. tenuicorne at copper and DOC concentrations typical of most marine waters. These results seem to indicate that at ambient total dissolved copper concentration in coastal and estuarine waters, C. tenuicorne might be able to access a sizable fraction of organically complexed copper when free copper concentration to the cell membrane is diffusion limited.

Influence of in‐stream diel concentration cycles of dissolved trace metals on acute toxicity to one‐year‐old cutthroat trout (Oncorhynchus clarki lewisi)

Extrapolating results of laboratory bioassays to streams is difficult, because conditions such as temperature and dissolved metal concentrations can change substantially on diel time scales. Field bioassays conducted for 96 h in two mining-affected streams compared the survival of hatchery-raised, metal-naïve westslope cutthroat trout (Oncorhynchus clarki lewisi) exposed to dissolved (0.1-microm filtration) metal concentrations that either exhibited the diel variation observed in streams or were controlled at a constant value. Cadmium and Zn concentrations in these streams increased each night by as much as 61 and 125%, respectively, and decreased a corresponding amount the next day, whereas Cu did not display a diel concentration cycle. In High Ore Creek (40 km south of Helena, MT, USA), survival (33%) after exposure to natural diel-fluctuating Zn concentrations (range, 214-634 microg/L; mean, 428 microg/L) was significantly (p = 0.008) higher than survival (14%) after exposure to a controlled, constant Zn concentration (422 microg/L). Similarly, in Dry Fork Belt Creek (70 km southeast of Great Falls, MT, USA), survival (75%) after exposure to diel-fluctuating Zn concentrations (range, 266-522 microg/L; mean, 399 microg/L) was significantly (p = 0.022) higher than survival (50%) in the constant-concentration treatment (392 microg/L). Survival likely was greater in these diel treatments, both because the periods of lower metal concentrations provided some relief for the fish and because toxicity during periods of higher metal concentrations was lessened by the simultaneous occurrence each night of lower water temperatures, which reduce the rate of metal uptake. Based on the present study, current water-quality criteria appear to be protective for streams with diel concentration cycles of Zn (and, perhaps, Cd) for the hydrologic conditions tested.

Effects of Pulsed Contaminant Exposures on Early Life Stages of the Fathead Minnow

Water quality standards for protecting aquatic life are based primarily on laboratory tests that use constant exposure concentrations. Typical effluent and nonpoint source exposure concentrations fluctuate in frequency, magnitude, and duration, which may result in different toxicological impacts. Current information indicates that pulsed or fluctuating exposures are generally more toxic than continuous exposures, when averaged over the applicable time period. However, few studies have evaluated chronic or sublethal effects of pulsed exposures, particularly those applicable to wastewater discharge situations. To address this issue, several pulsed exposure toxicity tests were conducted using modified fathead minnow (Pimephales promelas) early life stage (7 d) tests and several chemicals representative of those commonly encountered in wastewater effluents including copper, nitric acid, cadmium, and sodium chloride. Results suggest that survival and/or growth effects depend on the combination of frequency, magnitude, and duration, as well as the type of chemical. Nitric acid and sodium chloride pulsed treatments did not exhibit growth effects independent of survival effects, but both metals did elicit only growth effects in some treatments. Growth effects were related to pulse frequency and duration for copper and pulse duration and magnitude for cadmium. A 12-h exposure of approximately five times the 7-d continuous exposure IC(25) concentration of either metal quickly elicited mortality responses. Prolonged (>24 h) lag effects on survival were not observed in any of the experiments, regardless of the contaminant tested. Our results suggest that current water quality criteria may be underprotective if based on an average concentration over a 2-4 d exposure. For these contaminants, a short-term increase in concentration may elicit effects even though the average concentration is within nontoxic ranges for the organism.

Toxicological studies in tropical ecosystems: an ecotoxicological risk assessment of pesticide runoff in South Florida estuarine ecosystems.

A multiyear study in the C-111 canal system and associated sites in Florida Bay was undertaken to determine the potential pesticide risk that exists in South Florida. After the examination of extensive pesticide concentration data in surface water, tissues, and semipermeable membrane devices (SPMDs), canal contamination seems to be derived from the extensive agricultural production that drains into the C-111 canal. The results of this study indicate that runoff from agricultural processes led to quantifiable pesticide residues in both canal and bay surface water, which occasionally exceeded current water quality criteria. The major pesticide of concern was endosulfan, which was detected at 100% of the sites sampled. Endosulfan exposure did not cause any acute effects in fish and crustaceans deployed in field bioassays. Chronic effects were observed in copepods, clams, and oysters but could not be attributed to endosulfan exposure. The decision to alter the C-111 canal flow and allow increased freshwater flow into the adjacent Everglades National Park may result in discharges of pesticides into the Everglades. Continued monitoring in this area is needed during this change in flow regime.

Modeling Aquatic Mercury Fate in Clear Lake, Calif.

This paper describes the construction and application of a numerical model representing mercury transformations and bioavailability in the aquatic environment of Clear Lake, Calif. The initial application described here provides the basis for more detailed fate and transport modeling of the lake. Results show that total Hg and MeHg concentrations in the lake may be reasonably modeled as functions of sediment total Hg. Calibrated rates of methylation and benthic exchange compare favorably with rates observed in the field and at other lakes. The model suggests the importance of accurately defining a biochemically “available” fraction of total Hg, and demonstrates that even a relatively small amount of available Hg in lake sediments can account for high levels of potentially toxic methylmercury in the water and sediment bed. Indications are that Clear Lake is experiencing a net loss of Hg at a rate of less than 2%/year. At such a remediation rate, mercury concentrations in the lake would meet current water quality criteria in a little over 200 years.

Chemicals in California drinking water: source contaminants, risk assessment, risk management, and regulatory standards

Monitoring studies from 1983 to 1992 of water supply and drinking water wells in the state for organic contaminants indicated that more than 80 chemicals were present in ground water. Most of the chemicals detected occurred infrequently and at levels below the current water quality criteria (maximum contaminant level, MCL, or action level, AL). Drinking water wells with levels exceeding these criteria were either closed or had remedial actions taken. Dibromochloropropane (DBCP), simazine, diuron, atrazine, tetrachloroethylene (PCE), and trichloroethylene (TCE) were some of the chemicals detected most frequently in these studies. DBCP, simazine, diuron, and atrazine are agricultural pesticides and are either no longer registered or restricted for use as active ingredients. Special chemical contaminants of concern in ground water are nitrate, arsenic, fluoride, and radon. Surface water from rain and snow runoffs from the Sierra Nevada provides drinking water for most of the San Francisco Bay Area. This water is considered pristine and requires only treatment against disease-causing microorganisms. Most of Southern California depends on surface water from the Sacramento-San Joaquin River Delta and the Colorado River. The quality of water in the Delta is affected by discharges of pollutants into the watersheds of the Sacramento and San Joaquin Rivers and the intrusion of seawater from the San Francisco Bay. The major concern of most water utilities with regard to the use of Delta water for drinking is the formation of trihalomethanes (THMs) and other disinfection by-products. California can promulgate its own regulations which are frequently more stringent than the federal regulations. Standards have also been established for many water contaminants that are uniquely found in California. This report presents the state and federal drinking water standards for 19 inorganic, 66 organic, and 10 other chemicals, mainly radionuclides.

A randomized trial to evaluate the risk of gastrointestinal disease due to consumption of drinking water meeting current microbiological standards.

This project directly and empirically measured the level of gastrointestinal (GI) illness related to the consumption of tapwater prepared from sewage-contaminated surface waters and meeting current water quality criteria. A randomized intervention trial was carried out; 299 eligible households were supplied with domestic water filters (reverse-osmosis) that eliminate microbial and chemical contaminants from their water, and 307 households were left with their usual tapwater without a filter. The GI symptomatology was evaluated by means of a family health diary maintained prospectively by all study families over a 15-month period. The estimated annual incidence of GI illness was 0.76 among tapwater drinkers compared with 0.50 among filtered water drinkers (p less than 0.01). These findings were consistently observed in all population subgroups. It is estimated that 35% of the reported GI illnesses among the tapwater drinkers were water-related and preventable. Our results raise questions about the adequacy of current standards of drinking water quality to prevent water-borne endemic gastrointestinal illness.