Water Quality Criteria Research Articles

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.

Stream Salamanders are Relatively Tolerant of Salty Streams.

The application of road salt as a deicing agent is common, but investigations of potential negative effects of salt runoff on stream salamanders have been limited. Additionally, modern stormwater management practices should influence the delivery of salt ions to streams. We used data loggers in streams draining watersheds with and without stormwater management ponds and acute 96-h LC50 tests to investigate exposure of, and road salt toxicity among, two widespread salamanders in the Eastern USA, northern dusky salamanders (Desmognathus fuscus) and northern two-lined salamanders (Eurycea bislineata). In streams below stormwater ponds, base levels of conductivity were elevated throughout the year and elevated Cl- levels led to more frequent acute and chronic exceedances of U.S. Environmental Protection Agency ambient water quality criteria for Cl- when compared to streams draining watersheds with no stormwater management ponds. However, five of the six streams studied had exceedance frequencies suggesting Cl- associated with road salt application represented a persistent threat to aquatic life. Larval stream salamanders were relatively tolerant of salt, not exhibiting any lethal effects over a 96-h period until chloride levels exceeded 5000mg/L for both species, and concentrations in streams rarely exceeded these levels and only for very short periods of time. Our results suggest road salts are not having acute lethal effects on salamanders in the streams we studied, but exceedance of U.S. Environmental Protection Agency ambient water quality standards for Cl- suggest the potential for sublethal and indirect effects of Cl- on salamander populations that require further study.

Recovered mine drainage passive treatment residuals address legacy sediment pollution: A field mesocosm study at Grand Lake o' the Cherokees, Oklahoma

Grand Lake o' the Cherokees, Oklahoma is a large multipurpose reservoir that receives both elevated metals concentrations from the upstream Tri-State Lead-Zinc Mining District (TSMD) and excess nutrients from its agricultural watershed along with significant internal phosphorus (P) legacy loads. Mine drainage residuals (MDRs), amorphous iron oxyhydroxides recovered from passive treatment systems, may serve as phosphorus sinks. To evaluate the role of MDRs on reservoir sediment dynamics, a field mesocosm study (20-L vessels) was designed with four different mine drainage residuals (MDR) treatments: sediment control (no addition), mixed (MDR mixed with sediment), layered (MDR on top of sediment, no mixing) and bagged (MDR inside a fine mesh bag on top of sediment, no mixing) with phosphorus-spiked water. Soluble reactive P (SRP) concentrations demonstrated decreasing trends and the control treatment showed greater concentrations than all MDR treatments. P adsorption capacity (PAC) was determined to be approximately 0.7 mg/g and > 30 mg/g for sediments and MDRs, respectively. At Day 135, SRP reached >99% removal for all four treatments. Aqueous lead and cadmium concentrations were below detection limits and zinc concentrations were below the National Recommended Water Quality Criteria. Sediment lead, zinc and cadmium concentrations were below the TSMD-specific sediment quality guidelines, except for final Mixed MDR treatment sediment with 16.7% of samples exceeding both Cd and Pb criteria. Results showed that MDRs removed excess P from the water column and by using the recommended bagged addition method, trace metal release to both the water column and sediment layer were minimized.

Evaluation of heavy metal content in water and removal of metals using native isolated bacterial strains

Abstract. Saleh LIF, Rashed RO, Muhammed SM. 2021. Evaluation of heavy metal content in water and removal of metals using native isolated bacterial strains. Biodiversitas 22: 3163-3174. Natural surface water sources are susceptible to chemical contamination, including heavy metals. The goals of this study were to isolate naturally occurring heavy metal-tolerant bacteria by evaluating their ability to remove heavy metals from Tanjaro River and assessing the river’s water quality. The potency of bacteria to remove heavy metals (Cd, Pb, Cu, Cr, Ni, Zn, Co, and Fe) from the medium was conducted by inductively coupled plasma-optical emission spectrometry. Results of physicochemical parameters of the water samples were as follows: temperature 11.9–31°C, pH 6.1–8.64, total dissolved solids 268–464 mg.l-1, total hardness 232–485 mg.l-1, and alkalinity 122–324.3 mg.l-1. The overall mean concentrations of the heavy metals were in the order of Zn >Cu> Pb> Ni> Co> Fe> Cr> Cd), with values of 0.086, 0.073, 0.71, 0.068, 0.051, 0.056, 0.031, and 0.024ppm, respectively Moreover, the concentrations were generally exceeded the water quality criteria of WHO in some observations. The isolates included both gram-negative (56.5%) and gram-positive (43.5%) bacteria. The isolates displayed different degrees of resistance to heavy metals with maximum tolerable concentrations (MTCs) ranging from (10-250) ppm. Bacillus safensis and Leucobacter chromiiresistens were respectively able to tolerate (80, 90 ppm) Cd, (250, 160 ppm) Pb, (210,100 ppm) Cr, (110, 90 ppm) Ni and (160, 170 ppm) Co, while, Proteus mirabilis could tolerate 90 ppm Cd. The isolates were able to remove 55.4%Pb, 53.1%Cr, 53.7%Ni, 47.7Fe, 61.4%Co, and 55.8% Cu from a medium supplemented with the mixture of these heavy metals. The finding of this study indicated that Tanjaro River was undergoing frequent changes in water quality. Native bacterial isolates possessed considerable tolerance to selected heavy metals, which provides promising candidates for use in bioremediation.

Human health ambient water quality criteria for 13 heavy metals and health risk assessment in Taihu Lake

Human health ambient water quality criteria for 13 heavy metals and health risk assessment in Taihu Lake

Deriving Human Health and Aquatic Life Water Quality Criteria in the United States for Bioaccumulative Substances: A Historical Review and Future Perspective.

Methods used to derive water quality regulations for persistent, bioaccumulative, and toxic substances (PBTs) in the United States have evolved substantially over the past 50 yr, leveraging current understandings and assumptions about the nature and magnitude of partitioning and accumulation of substances in water, sediments, and organisms. In the United States and across the world, environmental regulations continue to evolve into more refined water quality criteria protective of aquatic life and human health. The present review provides historical context on the establishment of aquatic life and human health water quality criteria in the United States by compiling information from regulatory agencies and peer-reviewed literature on methods used to characterize and quantify bioaccumulation of substances in aquatic organisms and humans. Primary data needs and assumptions for various methods, as well as their application in setting criteria by the US Environmental Protection Agency over the past half century, are highlighted. Our review offers an important retrospective on the data and methods used to derive water quality criteria for PBTs and provides commentary on the future of US criteria development. Environ Toxicol Chem 2021;40:2394-2405. © 2021 SETAC.

Derivation of water quality criteria of zinc to protect aquatic life in Taihu Lake and the associated risk assessment

Zinc is a widely distributed environmental pollutants and has been listed as priority heavy metal pollutant in China. Similar as other heavy metals, toxicity of zinc to aquatic organisms affects by environmental factors such as water hardness. It is necessary to develop regional water quality criteria (WQC) to protect native aquatic life against zinc due to the diversity of aquatic organisms’ variability across different water systems, as a concretization and supplement for national zinc WQC. This study derived WQC for zinc by species sensitivity distribution (SSD) curve method. The zinc toxicity data of the aquatic organisms in Taihu Lake used in SSD curve was collected based on published toxicity data for zinc with hardness values and supplemented with acute toxicity tests conducted in this study. Six aquatic organism natives to Taihu Lake were selected to conduct zinc acute toxicity test in a range of hardness conditions. The relationship between water hardness and zinc toxicity was constructed. The criterion maximum concentration (CMC) and criterion continuous concentration (CCC) for zinc in Taihu Lake were then derived, which considered the water quality and taxonomic groups in Taihu Lake. The CMC and CCC were 100.69 μg/L and 30.79 μg/L, respectively. The environmental risk of zinc to Taihu Lake are acceptable, at moderate to low levels. This study has provided a basis for regional water quality criterion derivation and risk assessment in China.

Rare Earth Element Accumulation and Fractionation in a Lake Ecosystem Impacted by Past Uranium Mining.

Rare earth elements (REEs) are a natural resource of vital economic interest. While REE mining and processing are known for severe environmental issues, REEs are also by-products of other mining processes (e.g. uranium). Here, we provide an in-depth assessment of REE distribution across a lake system impacted by adjacent uranium mining over a long period (Bow Lake, Ontario, Canada). We observed a robust REE-U correlation with a consistent La/U ratio of 2.0 ± 0.2 and La concentrations up to 2200µgg-1. Selective extraction results demonstrated that 80-94% of REEs were acid extractible, while 3-8% of REEs were extracted by an alkaline solution (i.e. bound to natural organic matter). Analysis of specific REE patterns, together with a strong REE-P correlation, suggest that (co)precipitation with P mineral would be an important mechanism sequestrating REEs into Bow Lake sediments. Moreover, we identified three sources of particles delivering REEs into the lake with unique REE patterns: mine tailings, U ores and Precambrian bedrock. Negative Sm anomalies were detected in three soil samples and associated with the Precambrian bedrock. We also detected positive Gd and La anomalies in the sediments. Lanthanum anomalies were strongly correlated with U authigenic accumulation and thus associated with microbial processes requiring La, such as methanotrophy. This research demonstrates that lake sediments adjacent to U mining could represent ecological risks given that La and other REE concentrations largely exceed the maximum permissible concentrations. Water and sediment quality criteria are therefore required as both primary REE mining and extraction of REEs as by-products from legacy metallurgical tailings are increasing.

Development of regional water quality criteria of lead for protecting aquatic organism in Taihu Lake, China

Lead is a widely distributed priority controlled heavy metals in aquatic system, its toxicity to aquatic organisms affected by water quality parameters. This study investigated the acute toxicity of lead (Pb) to the aquatic organisms in Taihu Lake under various water hardness, corresponding regional water quality criteria were derived. The acute toxicity experimental results revealed that the toxicity of Pb to aquatic organisms increased with water hardness. The Pb toxicity has a highest toxicity at water hardness 50 mg/L (expressed as CaCO3), especially for Palaemon modestus where the 96 h LC50 value was 0.024 mg/L. The hazardous concentration for 5% of biological species (HC5) values were determined via species sensitivity distribution (SSD) method as 94.0 μg/L, 222.3 μg/L and 375.8 μg/L for Pb at water hardness 50, 150, and 250 mg/L, respectively. The assessment factor (AF) value was set at 2, followed by the current SSD framework where European commission recommend a fixed AF of 5–1. Thus, the predicted no effect concentration (PNEC) values was 47.0 μg/L, 111.2 μg/Land 187.9 μg/L at water hardness 50, 150, and 250 mg/L, respectively. Meanwhile, the short-term water quality criteria of Pb for Taihu lake aquatic organisms were derived as 111.2 μg/L at water hardness 150 mg CaCO3/L. The long-term water quality criteria were derived as 4.3 μg/L by using acute/chronic ratio 51.29. When the derived value was used for Taihu Lake, 2.7% of the sampling sites in Taihu Lake was exceeded this criterion. The results of this study can provide technical methods and basic information for deriving Pb regional water quality criteria for protecting native aquatic organisms, in China.

Assessment of habitat quality using macroinvertebrates and water quality parameters of a clay quarry wetland

In this study, it is aimed to determine the habitat quality of the Bozalan quarry wetland by using diversity and a compositional index of benthic macroinvertebrates and some of the water quality parameters. The field studies were conducted in the three sampling sites chosen in the wetland three times (March, April, and May) in 2018. The standard multi-habitat method was used for the benthos sampling. Besides, water sampling was performed for the parameters measured in-situ and analyzed in the laboratory to reveal the water quality status of the wetland. Some of the diversity index values of the benthic macroinvertebrates including Shannon Wiener (H′), Evenness Index (EI), and BMWP-e were calculated. The results showed that the sampling sites were categorized into higher classes (I and II) in general according to water quality criteria of the surface waters of Turkey. Fourteen taxa of benthic macroinvertebrates were identified. The most dominant taxa were Coenagrion sp. (42.31%), Baetis rhodani (15.38%), and Physella acuta (10%) in the study area. The highest number of individuals of macroinvertebrates was obtained in March (62 ind./m2), meanwhile the highest taxa number was determined in May (10 taxa). The H′ index was reached its highest value in May (1.723), whereas the lowest value of the index was in March (1.054). The highest score of the BMWP-e was found in May (26), while the lowest score was found in April (16).

Metal contamination and coexistence of metal and antibiotic resistance in Vibrio species recovered from aquaculture ponds with and without history of antibiotic usage in Southwest Nigeria

BackgroundThe use of metal-containing and antimicrobial compounds is a common practice in aquaculture operations in Nigeria. Only a few studies have focused on the impact of these chemicals on metal and antibiotic resistance development in the bacterial flora of aquaculture. This study therefore sets out to fill this gap.ResultsFive metals, namely copper (Cu), zinc (Zn), lead (Pb), nickel (Ni) and chromium (Cr), were detected at different concentrations in the pond water samples, with most values obtained exceeding the maximum recommended national standard for fisheries and recreation water quality criteria set by the National Environmental Standards and Regulations Enforcement Agency (NESREA) in Nigeria. A total of 121 Vibrio spp. were recovered from the aquaculture pond water with Vibrio cholerae having the highest frequency (37) followed by Vibrio parahaemolyticus (36), Vibrio vulnificus (36) and Vibrio alginolyticus (12). Seventy-five isolates were recovered from ponds with history of antibiotic use, while the ponds with no recognized history of antibiotic use had forty-six isolates. The percentage resistance to antibiotics in the isolates was: ampicillin (88.5%), amoxicillin–clavulanate (44.3%), tetracycline (41%), trimethoprim-sulfamethoxazole (22.1%), chloramphenicol (15.6%), ciprofloxacin (11.5%), imipenem (5.7%), ceftazidime (4.1%) and gentamicin (0%). All the isolates tolerated all the metals to 400 µg/mL concentration while only the trio of Pb, Ni and Cr were tolerated beyond the concentration. Zn and Cu appeared to be the most toxic metals on Vibrio spp., with no isolate surviving beyond the 400 µg/mL concentration mark, while 57 of the 121 isolates survived Cr at the highest concentration (3200 µg/mL), making it the most tolerated of the metals.ConclusionThis study reports a high level of metal contamination in the aquaculture ponds studied. The concentration of the metals exceeded the maximum permissible limits in Nigeria. Also, there was coexistence of metal and antibiotic resistance in the bacteria recovered from the aquaculture ponds. There is a need to regulate the use of chemicals, especially antibiotics and some biocidal compounds, to clamp down on the introduction of metals and antibiotics into the aquaculture systems, as these chemicals could facilitate the development of resistance traits in aquaculture bacteria by creating a selective pressure in the aquaculture environment.

Freshwater quality criteria of four strobilurin fungicides: Interspecies correlation and toxic mechanism

Strobilurin fungicides are widely used pesticides in the world. They can have toxic effects not only to target organisms, but also to nontarget organisms. To assess their ecological risk, species sensitivity distributions (SSDs) are required for the development of water quality criteria (WQC). In this paper, the acute toxicity of four methoxyacrylate fungicides were experimentally determined and evaluated at 24, 48, 72 and 96 h for the species of Rana chensinensis and Limnodrilus hoffmeisteri, respectively. Acute and chronic HC5 (5% hazard concentration) values and WQC values were calculated from SSDs based on the toxicity values determined in this paper and compiled from literature. SSDs revealed that aquatic animals were relatively sensitive species and aquatic plants are insensitive species for the four fungicides. However, different orders of species sensitivity in the acute and chronic toxicity indicated that these four fungicides had different toxic mechanisms or mode of action (MOA) to different species. According to toxicity correlation and principal component analysis (PCA), the kresoxim-methyl toxicity was very close to trifloxystrobin as compared with others due to that they are neutral compounds with very similar physicochemical properties. Quantitative structure-activity relationship (QSAR) revealed that toxicity of strobilurin fungicides were dependent both on chemical hydrophobicity and hydrogen bond basicity. These two molecular descriptors reflect the bio-uptake process and interaction of compounds with target receptors in an organism. WQC values and interspecies correlation are valuable for assessing water quality and understanding toxic mechanisms to different species.

Trophic ecology of sympatric batoid species (Chondrichthyes: Batoidea) assessed by multiple biogeochemical tracers (δ13C, δ15N and total Hg)

Aquatic pollution is known to reduce biodiversity and disrupt wildlife populations. Mercury (Hg) pollution is pervasive worldwide, contributing to the degradation of ecosystems, and causing deleterious effects to exposed organisms and populations. Batoids have a life history linked to the benthic substrate of coastal areas and occupy upper trophic levels. These combined with large bodies, long lifespan, and slow growth rates contributes to increased uptake and accumulation of Hg. However, mechanisms governing these associations are not well understood. Using multiple biogeochemical tracers (δ13C, δ15N and total Hg), we describe trophic interactions of three sympatric batoid species inhabiting an urbanized estuary and identify diet sources that contribute to Hg accumulation and trophic position among these mesopredators. We also use the Bat-ray (Myliobatis californica) as a model species, to compare diet composition, trophic position, and isotopic niche between two populations in two Californian bays. Trophic plasticity in M. californica was characterized by isotopic niche, diet proportions, and trophic position estimates using Bayesian statistics. We found diet and local contamination background strongly associated with Hg accumulation, and Hg levels that exceed EPA water quality criterion (<0.3 μg.g−1 w.w.) in all studied species.

Acute and Chronic Toxicity Testing of Drinking Water Treatment Residuals in Freshwater Systems.

The beneficial use of drinking water treatment residuals (DWTRs) faces barriers due primarily to uncertainties and concerns about their potential environmental impacts. We used total and water leachable toxic metal concentrations and 2 benthic organism-based bioassays to identify suitable DWTR substrates for introduction to freshwater systems. Using total metal contents and the consensus probable effect concentration concept, 3 DWTRs were selected and used in elutriate and toxicity studies. The concentrations of water leachable Ag, As, Cd, Cu, Cr, Ni, Pb, and Zn were below the US Environmental Protection Agency's ambient water quality criteria. Using the long-term 65-d life cycle Chironomus tentans test and 4 different endpoints (survival, adult emergence, egg case production, and number of eggs produced per female), no statistical differences were found between the DWTR treatments and the controls. Similarly, results obtained using the 10-d Hyalella azteca test showed no toxicity. However, although both survival and growth were recorded in all bioassays, the results of the 10-d C. tentans and the 28-d H. azteca tests were ambiguous. For C. tentans, 2 of the 3 DWTRs resulted in significantly lower survival rates compared to the controls. For H. azteca, no significant growth differences were observed between controls and DWTR treatments, but 2 of the 3 DWTRs resulted in significantly lower survival rates than the controls. Overall, these results suggest that certain DWTR substrates could be suitable for introduction to aquatic systems. Environ Toxicol Chem 2021;40:2005-2014. © 2021 SETAC.

Bathing Water Quality Monitoring Practices in Europe and the United States.

Many countries including EU Member States (EUMS) and the United States (U.S.) regularly monitor the microbial quality of bathing water to protect public health. This study comprehensively evaluates the EU bathing water directive (BWD) and the U.S. recreational water quality criteria (RWQC) as regulatory frameworks for monitoring microbial quality of bathing water. The major differences between these two regulatory frameworks are the provision of bathing water profiles, classification of bathing sites based on the pollution level, variations in the sampling frequency, accepted probable illness risk, epidemiological studies conducted during the development of guideline values, and monitoring methods. There are also similarities between the two approaches given that both enumerate viable fecal indicator bacteria (FIB) as an index of the potential risk to human health in bathing water and accept such risk up to a certain level. However, enumeration of FIB using methods outlined within these current regulatory frameworks does not consider the source of contamination nor variation in inactivation rates of enteric microbes in different ecological contexts, which is dependent on factors such as temperature, solar radiation, and salinity in various climatic regions within their geographical areas. A comprehensive “tool-box approach”, i.e., coupling of FIB and viral pathogen indicators with microbial source tracking for regulatory purposes, offers potential for delivering improved understanding to better protect the health of bathers.

Efficiency of Natural Clay Mineral Adsorbent Filtration Systems in Wastewater Treatment for Potential Irrigation Purposes

This project investigated the relative efficiencies of three pilot-scale constructed columns for enhancing drainage wastewater treatment processes to ensure compliance with Egyptian and international water quality criteria. In this investigation, basic materials (sand and gravel) and variable natural clay minerals zeolite (Z), diatomite (D) and bentonite (B) were utilized as packing materials to build up a Z column (ZC), D column (DC) and B column (BC), respectively. The three columns’ ability to remove pollutants from waste water for re-use in irrigation was investigated throughout one year (12 trials). The results revealed that the influent water had 211 mg/L total suspended solids, 6.09 mg/L total nitrogen, 36.67 mg/L biochemical oxygen demand, 56 mg/L chemical oxygen demand, 1700 mg/L total dissolved solids, 0.97 mg/L copper (Cu2+), 1.12 mg/L iron (Fe2+), 1.07 mg/L manganese (Mn2+), 1.02 mg/L lead (Pb2+), 1.05 mg/L zinc (Zn2+), and 46 × 103 CFU/mL fecal coliforms. These parameters were higher than the values permitted by Egyptian and international licenses. The range of removal efficiency of these pollutants by ZC was 96–21%, by BC was 99–29.8%, and by DC was 99–19.80%. Regeneration studies for the spent adsorbents demonstrated that the percentages of pollutant removal were sufficiently high. The treated effluent produced by the three columns was suitable for irrigation purposes, especially at a contact time of four hours, with the order for column treatment efficiency being BC ˃ DC ˃ ZC. Treated water was classified for irrigation suitability according to the Agrifood Water Quality Index (AFWQI) as marginal from the ZC, very good from the DC, and excellent from the BC. Treatment of such drainage water using the BC and DC appears feasible, because the process is easily operated and leads to final treated effluent of high quality for agricultural uses. The economic cost also confirms the feasibility of this treatment.

Derivation of site-specific selenium water quality criteria: A comparison of two methods and regulatory implications.

In 2016, the US Environmental Protection Agency (USEPA) issued revised aquatic life water quality criteria for selenium (Se). The criteria ("elements") consisted of threshold concentrations applicable to fish tissue (three tissue types, though the egg and ovary tissue takes precedence over the whole-body and muscle tissue thresholds), and water column. The agency rationalized that measured concentrations of Se in fish tissue were more predictive of potential adverse reproductive effects than those measured in external media. The agency provided two mechanisms for derivation of site-specific Se water criteria: a bioaccumulation factor (BAF) approach, and a partitioning-based bioaccumulation model approach. The use of either approach assumes that fish tissue concentrations exceed one or more of the tissue criteria. We compared the two approaches using fish tissue samples from various species in the Ohio River to evaluate resulting similarities and differences in the calculated Se water quality criteria. Fish (five species) were collected near two coal-fired power plants at sites unaffected by Se from wastewater discharges. Using results for all species and all sites combined, the resulting site-specific Se criteria for the BAF and partitioning-based model approach (median values) were 2.0 and 1.5 µg/L, respectively. Considering all species, resulting criteria differed little between the two power plant locations. Resulting criteria for both methods were strongly influenced by a small (less than detection) background Se water concentration. At least for the upper Ohio River, the BAF approach (requiring less input data) seems adequate for derivation of site-specific Se water criteria. In the current study, however, none of the tissue samples exceeded USEPA's tissue criteria. Thus, the decision to derive site-specific Se water quality criteria should be evaluated on a case-by-case basis, because the process may result in either a more stringent or less stringent value, wholly dependent on local factors. Integr Environ Assess Manag 2021;17:1255-1262. © 2021 SETAC.

Comparative Performance of Multiple Linear Regression and Biotic Ligand Models for Estimating the Bioavailability of Copper in Freshwater.

An increasing number of metal bioavailability models are available for use in setting regulations and conducting risk assessments in aquatic systems. Selection of the most appropriate model is dependent on the user's needs but will always benefit from an objective, comparative assessment of the performance of available models. In 2017, an expert workshop developed procedures for assessing metal bioavailability models. The present study applies these procedures to evaluate the performance of biotic ligand models (BLMs) and multiple linear regression (MLR) models for copper. We find that the procedures recommended by the expert workshop generally provide a robust series of metrics for evaluating model performance. However, we recommend some modifications to the analysis of model residuals because the current method is insensitive to relatively large differences in residual patterns when comparing models. We also provide clarification on details of the evaluation procedure which, if not applied correctly, could mischaracterize model performance. We found that acute Cu MLR and BLM performances are quite comparable, though there are differences in performance on a species‐specific basis and in the resulting water quality criteria as a function of water chemistry. In contrast, the chronic Cu MLR performed distinctly better than the BLM. Observed differences in performance are due to the smaller effects of hardness and pH on chronic Cu toxicity compared to acute Cu toxicity. These differences are captured in the chronic MLR model but not the chronic BLM, which only adjusts for differences in organism sensitivity. In general, we continue to recommend concurrent development of both modeling approaches because they provide useful comparative insights into the strengths, limitations, and predictive capabilities of each model. Environ Toxicol Chem 2021;40:1649–1661. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Long-term monitoring reveals convergent patterns of recovery from mining contamination across 4 western US watersheds

Long-term studies of stream ecosystems are essential for assessing restoration success because they allow researchers to quantify recovery trajectories, gauge the relative influence of episodic events, and determine the time required to achieve clean-up objectives. To quantify responses of benthic macroinvertebrate assemblages to stream remediation, we integrated results of 4 long-term (20–29 y) assessments of mining-impacted watersheds that were broadly distributed across the western US (California, Colorado, Idaho, Montana). Using a before–after control–impact (BACI) study design, we observed substantial reductions in metal concentrations and corresponding improvements of benthic assemblages following remediation. Recovery rates were relatively consistent, and streams typically recovered within 10 to 15 y after remediation was initiated (mean = 10.25 y), although episodic events changed trajectories at some sites. Differences in recovery among watersheds were likely determined by a number of factors, including the severity of contamination, effectiveness of remediation, proximity to upstream sources of colonization, and hydrologic variation. We also observed considerable variation in the rate and extent of recovery among assemblage metrics. For example, total abundance and richness recovered rapidly at most sites, but the composition of benthic macroinvertebrate assemblages remained substantially altered compared with reference sites. Using piecewise linear regression, we estimated a threshold response of Ephemeroptera, Plecoptera, and Trichoptera (EPT) species richness at ~1 cumulative criteria unit (CCU), which is the sum of the fractions of chronic water-quality criteria for metals measured, suggesting this value was protective of benthic assemblages. However, EPT richness was reduced by ~20% at 2× this CCU value, indicating that moderate exceedances of water-quality criteria could substantially affect stream biodiversity. Non-metric multidimensional scaling analyses identified common sets of species trait states across the 4 watersheds that were associated with either metal contamination or with recovering and intact reference stream assemblages. Our study illustrates the importance of long-term studies for quantifying responses to stream restoration and the usefulness of BACI designs for demonstrating cause-and-effect relationships between restoration treatments and community recovery. Because these 4 watersheds were among the most severely polluted sites in the western US, our study demonstrates the value of these investments in watershed restoration and the potential for success under the most extreme conditions.

Application of the health risk assessment of acetochlor in the development of water quality criteria

Acetochlor is a widely used herbicide in agricultural production. Studies have shown that acetochlor has obvious environmental hormone effects, and long-term exposure may pose a threat to human health. To quantify the hazards of acetochlor in drinking water, a health risk assessment of acetochlor was conducted in major cities of China based on the data of acetochlor residue concentrations in drinking water. The approach of the Species Sensitivity Distributions (SSD) method is used to extrapolate from animal testing data to reflect worst case human toxicity. Results show that hazard quotients related to acetochlor residues in drinking water for different age groups range from 1.94 × 10−4 to 6.13 × 10−4, so, there are no indication of human risk. Compared to the total estimated hazard quotient from oral intake of acetochlor, the chronic exposure imputed to acetochlor residues in drinking water in China accounts for 0.4%. This paper recommends 0.02 mg/L to be the maximum acetochlor residue concentration level in drinking water and source water criteria.