Acute Water Quality Criteria Research Articles

Water quality criteria for lanthanum for freshwater aquatic organisms derived via species sensitivity distributions and interspecies correlation estimation models

The increasing exploitation and application of rare earth elements (REEs) may induce hazardous risks to freshwater aquatic organisms. Due to the lack of water quality criteria (WQC) and sufficient reliable toxicity data, little information is available on the ecological risk of REEs in surface water. In this study, lanthanum (La) toxicity data were collected from published toxicological studies, and the data quality was assessed using a toxicological data reliability assessment tool. To obtain more toxicity data, Daphnia magna, Cyprinus carpio, and Dania rerio embryos were selected as surrogate species, and an interspecies correlation estimation (ICE) model was used to predict the toxicity of La for untested species. The species sensitivity distributions (SSDs) of La toxicity and WQC were investigated. Differences were observed in the hazardous concentrations for 5% of species (HC5), but no statistically significant differences were noted in the SSD curves between the measured acute toxicity data and the predicted data. For the SSDs constructed from the measured toxicity data, the ICE-predicted toxicity data and all acute data supplemented with the ICE-predicted data, the acute WQC values of La were 88, 1022 and 256 μg/L, respectively. According to the SSD and corresponding HC5 of chronic toxicity data, the chronic WQC was 14 μg/L. The results provide a scientific reference for establishing WQC for freshwater aquatic organisms and ecological risk assessments of REEs.

Data and Diversity in the Development of Acute Water Quality Criteria in the United States.

The US Environmental Protection Agency (USEPA) is responsible for the development of water quality criteria, regulatory standards that protect aquatic organisms from harmful chemical exposure. Although these criteria are intended to be broadly protective of aquatic life, the data used to derive criteria do not necessarily reflect the actual diversity of natural communities nor are they available for most chemicals. In addition, although the USEPA's current procedures emphasize using toxicity data with a certain minimum amount of biological diversity, the quantitative impact of such diversity on criteria is unclear. In the present study we assessed the changes to acute toxicity data over time, determined the prevalence of significant taxonomic differences in sensitivity, and investigated the effect of biological diversity on criteria. We found major gaps in existing toxicity data that we hypothesize have contributed to the absence of acute criteria for the majority of chemical pollutants. Taxonomic patterns of sensitivity in these data are abundant, although the resolution of the patterns is relatively poor. In addition, we found that the amount of biological diversity in a toxicity data set and the data set's taxonomic composition does not quantitatively affect criteria in most cases. Because the USEPA has published acute criteria for fewer than 20% of priority pollutants and the persistence of major gaps in toxicity data over the last 37 years, we recommend that the USEPA consider revisions to their water quality criteria guidelines that will expedite the criteria development process and advance the responsible management of pollutants in the aquatic environment. Environ Toxicol Chem 2022;41:1333-1343. © 2022 SETAC.

Ecological Risk Assessment of Phthalate Esters (DBP and DEHP) in Surface Water of China

As a new type of pollutant, phthalate esters (PAEs) are common organic compounds in industrial production and daily life, which are widely detected in surface water environment. Among them, dibutyl phthalate (DBP) and bis (2-ethylhexyl) phthalate (DEHP) have attracted much attention due to their harmful effects on aquatic life such as endocrine disrupting effects. In this study, the toxicity data of DBP and DEHP were collected and screened through literature research, and their water quality criteria (WQC) for protecting aquatic life were derived by the species sensitivity distribution method. In addition, the distributions of DBP and DEHP in surface water environment of China were analyzed and their ecological risk levels to aquatic life in six regions were evaluated by hazard quotients (HQs) and probabilistic approaches. The result revealed that the chronic WQC of DBP is 12.9 μg/L (criteria continuous concentration, CCC) and acute WQC is 162.9 μg/L (criteria maximum concentration, CMC) and the chronic WQC of DEHP is 1.0 μg/L (CCC) and acute WQC is 71.8 μg/L (CMC). The ecological risk of DBP and DEHP in North China and Yangtze River is relatively higher than other regions, which may have harmful effects on the aquatic environments. So, it is necessary to strengthen the water quality management. The results could provide scientific basis for ecological risk management of DBP and DEHP.

Water quality of runoff from flat panel display glass concrete during modified accelerated aging plus leaching tests.

Flat panel display glass (FPDG) from plasma televisions is difficult to recycle due to their heavy metal composition. When crushed, flat panel display glass has similar physical properties to sand and could be used as a recycled aggregate in concrete, if the potentially harmful metals in FPDG can be encapsulated. To replicate leaching from environmental exposure, at periodic points during freeze-thaw tests, samples of concrete with 0%, 10%, and 20% FPDG were exposed to simulated rainwater and the runoff water was analyzed. For the metals detected (arsenic, barium, chromium, and lead), lead concentrations in the leachate/runoff from 20% FPDG samples exceeded the acute ambient water quality criteria after approximately 50-60 cycles; however, no samples exceeded the toxic characteristic leaching procedure limits at any point during freeze-thaw testing. Increases in lead and chromium concentrations over time indicate a need for stabilization, especially since lead exceeded the acute water quality criteria. PRACTITIONER POINTS: TCLP results indicate flat panel display glass is not expected to release RCRA-8 metals at or above regulatory limits. Accelerated aging-leaching tests indicate lead might be released at levels approaching or exceeding the acute ambient water quality criteria. With additional lead stabilization, this study shows flat panel display glass has the potential to be used in concrete.

Marine environmental risk assessment and acute water quality criterion for pentachlorophenol in coastal waters.

Pentachlorophenol (PCP) is a organochlorine biocide that, unlike most other organochlorines, is still in use as timber preservative. Its water solubility, high toxicity, bioaccumulation potential, and the concentrations reported in estuarine waters (up to 0.1 µg L-1) indicate it may pose a risk in coastal environments. Aquatic environrmental regulations are commonly based on standard freshwater organisms that may not represent the sensitivity of marine species. The present study consists of a water quality criteira reevalutation of PCP in coastal waters based on toxicity tests conducted recording sensitive endpoints of marine species representative of coastal ecosystems, following QA/QC standard procedures. The toxicity thresholds (EC10) found were 4.69 µg L-1 for Paracentrotus lividus sea-urchin embryos, 6.47 µg L-1 for Mytilus galloprovincialis mussel larvae, and 78.4 µg L-1 for Isochrysis galbana cells. Therefore, there is only one order of magnitude between the predicted no-effect concentration (PNEC) for early life stages of bivalves and echinoderms and the maximum concentrations actually recorded in coastal water, which yields a remarkable risk quotient for PCP in these highly productive marine habitats. In addition, we have reviewed the ecotoxicological data on PCP toxicity on marine species representative of the main systematic groups, from algae to chordates, and derived a probabilistic acute saltwater quality criterion of 2.66 µg L-1, intended to protect 95% of the marine species. Lack of adequate protection for marine ecosystems in some current PCP national guidelines has been identified.

Model for Predicting Toxicities of Metals and Metalloids in Coastal Marine Environments Worldwide.

Metals can pose hazards to marine species and can adversely affect structures and functions of communities of marine species. However, little is known about how structural properties of metal atoms combined with current geographical and climatic conditions affect their toxic potencies. A mathematical model, based on quantitative structure-activity relationships and species sensitivity distributions (QSAR-SSD) was developed by use of acute toxicities of six metals (Cd, Cr, Cu, Hg, Ni, and Zn) to eight marine species and accessory environmental conditions. The model was then used to predict toxicities of 31 metals and metalloids and then to investigate relationships between acute water quality criteria (WQC) and environmental conditions in coastal marine environments. The model was also used to predict WQC in the coastal areas of different countries. Given global climate change, the QSAR-SSD model allows development of WQC for metals that will be protective of marine ecosystems under various conditions related to changes in global climate. This approach could be of enormous benefit in delivering an evidence-based approach to support regulatory decision making in management of metal and metalloids in marine waters.

Toxicity of Chromium (VI) to Two Mussels and an Amphipod in Water-Only Exposures With or Without a Co-stressor of Elevated Temperature, Zinc, or Nitrate.

The objectives of the present study were to develop methods for propagating western pearlshell (Margaritifera falcata) for laboratory toxicity testing and evaluate acute and chronic toxicity of chromium VI [Cr(VI)] to the pearlshell and a commonly tested mussel (fatmucket, Lampsilis siliquoidea at 20°C or in association with a co-stressor of elevated temperature (27°C), zinc (50µg Zn/L), or nitrate (35mg NO3/L). A commonly tested invertebrate (amphipod, Hyalella azteca) also was tested in chronic exposures. Newly transformed pearlshell (~1week old) were successfully cultured and tested in acute 96h Cr exposures (control survival 100%). However, the grow-out of juveniles in culture for chronic toxicity testing was less successful and chronic 28-day Cr toxicity tests started with 4month-old pearlshell failed due to low control survival (39-68%). Acute median effect concentration (EC50) for the pearlshell (919µg Cr/L) and fatmucket (456µg Cr/L) tested at 20°C without a co-stressor decreased by a factor of > 2 at elevated temperature but did not decrease at elevated Zn or elevated NO3. Chronic 28-day Cr tests were completed successfully with the fatmucket and amphipod (control survival 83-98%). Chronic maximum acceptable toxicant concentration (MATC) for fatmucket at 20°C (26µg Cr/L) decreased by a factor of 2 at elevated temperature or NO3 but did not decrease at elevated Zn. However, chronic MATC for amphipod at 20°C (13µg Cr/L) did not decrease at elevated temperature, Zn, or NO3. Acute EC50s for both mussels tested with or without a co-stressor were above the final acute value used to derive United States Environmental Protection Agency acute water quality criterion (WQC) for Cr(VI); however, chronic MATCs for fatmucket at elevated temperature or NO3 and chronic MATCs for the amphipod at 20°C with or without elevated Zn or NO3 were about equal to the chronic WQC. The results indicate that (1) the elevated temperature increased the acute Cr toxicity to both mussel species, (2) fatmucket was acutely more sensitive to Cr than the pearlshell, (3) elevated temperature or NO3 increased chronic Cr toxicity to fatmucket, and (4) acute WQC are protective of tested mussels with or without a co-stressor; however, the chronic WQC might not protect fatmucket at elevated temperature or NO3 and might not protect the amphipod at 20°C with or without elevated Zn or NO3.

Acute water quality criteria for polycyclic aromatic hydrocarbons, pesticides, plastic additives, and 4-Nonylphenol in seawater

Probabilistic environmental quality criteria for Naphthalene (Nap), Phenanthrene (Phe), Fluoranthene (Flu), Pyrene (Pyr), Triclosan (TCS), Tributyltin (TBT), Chlorpyrifos (CPY), Diuron (DUR), γ-Hexaclorocyclohexane (γ-HCH), Bisphenol A (BPA) and 4-Nonylphenol (4-NP) were derived from acute toxicity data using saltwater species representative of marine ecosystems, including algae, mollusks, crustaceans, echinoderms and chordates. Preferably, data concerns sublethal endpoints and early life stages from bioassays conducted in our laboratory, but the data set was completed with a broad literature survey. The Water Quality Criteria (WQC) obtained for TBT (7.1·10−3 μg L−1) and CPY (6.6· 10−3 μg L−1) were orders of magnitude lower than those obtained for PAHs (ranging from 3.75 to 45.2 μg L−1), BPA (27.7 μg L−1), TCS (8.66 μg L−1) and 4-NP (1.52 μg L−1). Critical values for DUR and HCH were 0.1 and 0.057 μg L−1 respectively. Within this context, non-selective toxicants could be quantitatively defined as those showing a maximum variability in toxicity thresholds (TT) of 3 orders of magnitude across the whole range of marine diversity, and a cumulative distribution of the TT fitting to a single log-logistic curve, while for selective toxicants variability was consistently found to span 5 orders of magnitude and the TT distribution showed a bimodal pattern. For the latter, protective WQC must be derived taking into account the SSD of the sensitive taxa only.

Derivation of freshwater water quality criteria for dibutyltin dilaurate from measured data and data predicted using interspecies correlation estimate models

Dibutyltin dilaurate (DBTL) is an organotin compound that has been widely detected in aquatic environments. However, the ecological risk assessment for DBTL is hard to perform due to the absence of water quality criteria (WQC) and lack of toxicity data. In this study, toxicity data were obtained from acute and chronic toxicity tests using aquatic species resident in China. Based on the species sensitivity distributions (SSDs) constructed from these test data, the acute water quality criterion (AWQC) and chronic water quality criterion (CWQC) were then derived to be 132 μg/L and 31.9 μg/L for DBTL. In order to valid the predicted data in the application to the protective criteria development and hazard assessment, the web-based interspecies correlation estimation (Web-ICE) system was used to estimate acute toxicities. Here two acute toxicity data groups for surrogate species were chosen from experimental data and QSAR Toolbox-predicted data separately, giving estimated data for prediction species using Web-ICE software. According to Kolmogorov–Smirnov test results, Web-ICE-based SSDs and measurement-based SSD were not significantly different. The results showed that the differences between measurement-based (132 μg/L) and Web-ICE-based AWQCs (39.7 μg/L and 58.5 μg/L) were statistically acceptable. Under certain conditions, it is therefore worth considering using the QSAR Toolbox plus Web-ICE method here to provide a beneficial supplement for developing preliminarily screen level toxicities in WQC when little or no relevant information are available. Besides, the geographic distribution of species was demonstrated not to be a significant factor in SSD establishment and WQC derivation.

Non-parametric kernel density estimation of species sensitivity distributions in developing water quality criteria of metals.

Due to use of different parametric models for establishing species sensitivity distributions (SSDs), comparison of water quality criteria (WQC) for metals of the same group or period in the periodic table is uncertain and results can be biased. To address this inadequacy, a new probabilistic model, based on non-parametric kernel density estimation was developed and optimal bandwidths and testing methods are proposed. Zinc (Zn), cadmium (Cd), and mercury (Hg) of group IIB of the periodic table are widespread in aquatic environments, mostly at small concentrations, but can exert detrimental effects on aquatic life and human health. With these metals as target compounds, the non-parametric kernel density estimation method and several conventional parametric density estimation methods were used to derive acute WQC of metals for protection of aquatic species in China that were compared and contrasted with WQC for other jurisdictions. HC5 values for protection of different types of species were derived for three metals by use of non-parametric kernel density estimation. The newly developed probabilistic model was superior to conventional parametric density estimations for constructing SSDs and for deriving WQC for these metals. HC5 values for the three metals were inversely proportional to atomic number, which means that the heavier atoms were more potent toxicants. The proposed method provides a novel alternative approach for developing SSDs that could have wide application prospects in deriving WQC and use in assessment of risks to ecosystems.

Formaldehyde concentration in discharge from land based aquaculture facilities in Atlantic Canada.

Formaldehyde is used in freshwater aquaculture facilities in the Maritimes region of Canada to prevent external parasites and is discharged without treatment to freshwater receiving environments. In this study, formaldehyde was measured at effluent outfalls and 100 m downstream of four land based aquaculture facilities at various post-treatment time intervals. Concentrations of formaldehyde ranged from 0.2 to 7.1 mg/L. Based on Environment Canada's environmental no effect value, all of the samples show a potential risk to aquatic life. Furthermore, based on a chronic aquatic life water quality criterion of 1.61 mg/L all but two of the samples had concentrations considered to be toxic to aquatic life. An acute water quality criteria was only exceeded once in all of the environmental measurements of formaldehyde. These results lead us to hypothesize that the discharge of formaldehyde from land-based facilities may cause adverse chronic impacts.

Weighted species sensitivity distribution method to derive site-specific quality criteria for copper in Tai Lake, China.

Tai Lake (Ch: Taihu), which is the largest lake in Jiangsu province, China, has been affected by human activities. As part of a concerted effort to improve water quality to protect the integrity of the Tai Lake ecosystem, a water quality criterion (WQC) was developed for copper (Cu) II. The acute WQC was based on 440 values for acute toxicity of Cu to 24 species from 6 phyla, 16 families, and 20 genera. In addition, 255 values for chronic toxicity of Cu to 10 species from 5 phyla, 8 families, and 9 genera were used to derive chronic WQC. Instead of using a traditional approach based species sensitivity distributions (SSD), a weighted species sensitivity distribution (WSSD) approach was used to calculate the cumulative probability based on endemic species to Tai Lake. Acute and chronic WQC developed by use of the WSSD were 5.3 and 3.7 μg Cu/L, respectively. While the WQC values were comparable to those of other countries, there were slight differences due to variability in species composition of different regions. The site-specific criteria indicated that the current standard set for surface water by the Chinese government might not be protective of aquatic organisms in Tai Lake.

Ecotoxicologically based marine acute water quality criteria for metals intended for protection of coastal areas

Acute water quality criteria (WQC) for the protection of coastal ecosystems are developed on the basis of short-term ecotoxicological data using the most sensitive life stages of representative species from the main taxa of marine water column organisms. A probabilistic approach based on species sensitivity distribution (SSD) curves has been chosen and compared to the WQC obtained applying an assessment factor to the critical toxicity values, i.e. the ‘deterministic’ approach. The criteria obtained from HC5 values (5th percentile of the SSD) were 1.01μg/l for Hg, 1.39μg/l for Cu, 3.83μg/l for Cd, 25.3μg/l for Pb and 8.24μg/l for Zn. Using sensitive early life stages and very sensitive endpoints allowed calculation of WQC for marine coastal ecosystems. These probabilistic WQC, intended to protect 95% of the species in 95% of the cases, were calculated on the basis of a limited ecotoxicological dataset, avoiding the use of large and uncertain assessment factors.

Derivation of water quality criteria for representative water-body pollutants in China

In this study, toxicological data for zinc (Zn), cadmium (Cd), hexavalent chromium (Cr (VI)), benzene, and nitrobenzene were collected from various databases and publications, screened and then constructed into species sensitivity distribution (SSD) curves. Then water quality criteria (WQC) were derived for protection of the freshwater aquatic life in China against five representative pollutants. The values derived in this study were compared with those issued by the US Environmental Protection Agency and the Chinese national environmental standard for surface water to identify factors underlying the differences. The results showed that the SSD curves for the five pollutants differed significantly, with the examined aquatic species being generally more sensitive to Zn, Cd, and Cr (VI) than benzene and nitrobenzene. The acute WQC were: 48.43 μg L−1 for Zn, 0.4218 μg L−1 for Cd, 45.79 μg L−1 for Cr (VI), 2651 μg L−1 for benzene, and 1426 μg L−1 for nitrobenzene. The chronic WQC were: 20.01 μg L−1 for Zn, 0.2428 μg L−1 for Cd, 14.22 μg L−1 for Cr (VI), 530.2 μg L−1 for benzene, and 286.2 μg L−1 for nitrobenzene. The results of this comparative study of representative pollutants may offer guideline values for future WQC studies for China.

Pollutant fate and spatio-temporal variability in the choptank river estuary: Factors influencing water quality

Restoration of the Chesapeake Bay, the largest estuary in the United States, is a national priority. Documentation of progress of this restoration effort is needed. A study was conducted to examine water quality in the Choptank River estuary, a tributary of the Chesapeake Bay that since 1998 has been classified as impaired waters under the Federal Clean Water Act. Multiple water quality parameters (salinity, temperature, dissolved oxygen, chlorophyll a) and analyte concentrations (nutrients, herbicide and herbicide degradation products, arsenic, and copper) were measured at seven sampling stations in the Choptank River estuary. Samples were collected under base flow conditions in the basin on thirteen dates between March 2005 and April 2008. As commonly observed, results indicate that agriculture is a primary source of nitrate in the estuary and that both agriculture and wastewater treatment plants are important sources of phosphorus. Concentrations of copper in the lower estuary consistently exceeded both chronic and acute water quality criteria, possibly due to use of copper in antifouling boat paint. Concentrations of copper in the upstream watersheds were low, indicating that agriculture is not a significant source of copper loading to the estuary. Concentrations of herbicides (atrazine, simazine, and metolachlor) peaked during early-summer, indicating a rapid surface-transport delivery pathway from agricultural areas, while their degradation products (CIAT, CEAT, MESA, and MOA) appeared to be delivered via groundwater transport. Some in-river processing of CEAT occurred, whereas MESA was conservative. Observed concentrations of herbicide residues did not approach established levels of concern for aquatic organisms. Results of this study highlight the importance of continued implementation of best management practices to improve water quality in the estuary. This work provides a baseline against which to compare future changes in water quality and may be used to design future monitoring programs needed to assess restoration strategy efficacy.

Evaluation of acute copper toxicity to juvenile freshwater mussels (fatmucket, Lampsilis siliquoidea) in natural and reconstituted waters

The influence of dissolved organic carbon (DOC) and water composition on the toxicity of copper to juvenile freshwater mussels (fatmucket, Lampsilis siliquoidea) were evaluated in natural and reconstituted waters. Acute 96-h copper toxicity tests werec onducted at four nominal DOC concentrations (0, 2.5, 5, and 10 mg/L as carbon [C]) in dilutions of natural waters and in American Society for Testing and Materials (ASTM) reconstituted hard water. Toxicity tests also were conducted in ASTM soft, moderately hard, hard, and very hard reconstituted waters (nominal hardness 45-300 mg/L as CaCO₃). Three natural surface waters (9.5-11 mg/L DOC) were diluted to obtain a series of DOC concentrations with diluted well water, and an extract of natural organic matter and commercial humic acid was mixed with ASTM hard water to prepare a series of DOC concentrations for toxicity testing. Median effective concentrations (EC50s) for dissolved copper varied >40-fold (9.9 to >396 gg Cu/L) over all 21 treatments in various DOC waters. Within a particular type of DOC water, EC50s increased 5- to 12-fold across DOC concentrations of 0.3 to up to 11 mg C/L. However, EC50s increased by only a factor of 1.4 (21-30 gg Cu/L) in the four ASTM waters with wide range of water hardness (52-300 mg CaCO₃/L). Predictions from the biotic ligand model (BLM) for copper explained nearly 90% of the variability in EC50s. Nearly 70% of BLM-normalized EC50s for fatmucket tested in natural waters were below the final acute value used to derive the U.S. Environmental Protection Agency acute water quality criterion for copper, indicating that the criterion might not be protective of fatmucket and perhaps other mussel species.

Influence of pH on the acute toxicity of ammonia to juvenile freshwater mussels (fatmucket, Lampsilis siliquoidea)

The objective of the present study was to evaluate the influence of pH on the toxicity of ammonia to juvenile freshwater mussels. Acute 96-h ammonia toxicity tests were conducted with 10-d-old juvenile mussels (fatmucket, Lampsilis siliquoidea) at five pH levels ranging from 6.5 to 9.0 in flow-through diluter systems at 20 degrees C. Acute 48-h tests with amphipods (Hyalella azteca) and 96-h tests with oligochaetes (Lumbriculus variegatus) were conducted concurrently under the same test conditions to determine the sensitivity of mussels relative to these two commonly tested benthic invertebrate species. During the exposure, pH levels were maintained within 0.1 of a pH unit and ammonia concentrations were relatively constant through time (coefficient of variation for ammonia concentrations ranged from 2 to 30% with a median value of 7.9%). The median effective concentrations (EC50s) of total ammonia nitrogen (N) for mussels were at least two to six times lower than the EC50s for amphipods and oligochaetes, and the EC50s for mussels decreased with increasing pH and ranged from 88 mg N/L at pH 6.6 to 0.96 mg N/L at pH 9.0. The EC50s for mussels were at or below the final acute values used to derive the U.S. Environmental Protection Agency's acute water quality criterion (WQC). However, the quantitative relationship between pH and ammonia toxicity to juvenile mussels was similar to the average relationship for other taxa reported in the WQC. These results indicate that including mussel toxicity data in a revision to the WQC would lower the acute criterion but not change the WQC mathematical representation of the relative effect of pH on ammonia toxicity.

Heavy metal pollution in the Baotou section of the Yellow River, China

Baotou City is a representative heavy industrial city in the drainage basin of the Yellow River. This paper studies the pollution of a contaminated section (Baotou section) of the Yellow River, China, with a known anthropogenic heavy metal input from the industrial discharge. The distribution of heavy metals (Cu, Pb, Zn and Cd) in the overlying water, filtered water (overlying water filtered through a 0.45-μm filter membrane) and sediments was determined in the Baotou section of the Yellow River. The results of this research indicate that heavy metal pollutants transport mostly through the carriers of suspended particulates and sediments in the fluvial environment. Baotou City’s industrial discharge draining into the Yellow River from the tributaries (the Kundulun River and the Sidaosha River) increases the concentrations of Cu, Pb, Zn and Cd in the mainstream and influences heavy metals speciation. Speciation analyses show that the Cd is easily enriched in the secondary phase (bioavailable form), followed by Pb. Furthermore, based on the acute water quality criteria (WQC-Acute) and chronic water quality criteria (WQC-Chronic) set by the United States Environmental Protection Agency, the acute sediment quality criteria (SQC-Acute) and the chronic sediment quality criteria (SQC-Chronic) are calculated respectively using the developed equilibrium partitioning approach (EqP). By comparing heavy metal contents in sediments with SQC-Acute and SQC-Chronic respectively, we note that Pb and Cd have posed a high risk to the quality of water environment and to the aquatic ecosystem health of Baotou section of the Yellow River.

Acute toxicity of copper, ammonia, and chlorine to glochidia and juveniles of freshwater mussels (unionidae)

The objective of the present study was to determine acute toxicity of copper, ammonia, or chlorine to larval (glochidia) and juvenile mussels using the recently published American Society for Testing and Materials (ASTM) Standard guide for conducting laboratory toxicity tests with freshwater mussels. Toxicity tests were conducted with glochidia (24- to 48-h exposures) and juveniles (96-h exposures) of up to 11 mussel species in reconstituted ASTM hard water using copper, ammonia, or chlorine as a toxicant. Copper and ammonia tests also were conducted with five commonly tested species, including cladocerans (Daphnia magna and Ceriodaphnia dubia; 48-h exposures), amphipod (Hyalella azteca; 48-h exposures), rainbow trout (Oncorhynchus mykiss; 96-h exposures), and fathead minnow (Pimephales promelas; 96-h exposures). Median effective concentrations (EC50s) for commonly tested species were >58 microg Cu/L (except 15 microg Cu/L for C. dubia) and >13 mg total ammonia N/L, whereas the EC50s for mussels in most cases were <45 microg Cu/L or <12 mg N/L and were often at or below the final acute values (FAVs) used to derive the U.S. Environmental Protection Agency 1996 acute water quality criterion (WQC) for copper and 1999 acute WQC for ammonia. However, the chlorine EC50s for mussels generally were >40 microg/L and above the FAV in the WQC for chlorine. The results indicate that the early life stages of mussels generally were more sensitive to copper and ammonia than other organisms and that, including mussel toxicity data in a revision to the WQC, would lower the WQC for copper or ammonia. Furthermore, including additional mussel data in 2007 WQC for copper based on biotic ligand model would further lower the WQC.

RISK ASSESSMENT OF WATER QUALITY IN THREE NORTH CAROLINA, USA, STREAMS SUPPORTING FEDERALLY ENDANGERED FRESHWATER MUSSELS (UNIONIDAE)

Water quality data were collected from three drainages supporting the endangered Carolina heelsplitter (Lasmigona decorata) and dwarf wedgemussel (Alasmidonta heterodon) to determine the potential for impaired water quality to limit the recovery of these freshwater mussels in North Carolina, USA. Total recoverable copper, total residual chlorine, and total ammonia nitrogen were measured every two months for approximately a year at sites bracketing wastewater sources and mussel habitat. These data and state monitoring datasets were compared with ecological screening values, including estimates of chemical concentrations likely to be protective of mussels, and federal ambient water quality criteria to assess site risks following a hazard quotient approach. In one drainage, the site-specific ammonia ecological screening value for acute exposures was exceeded in 6% of the samples, and 15% of samples exceeded the chronic ecological screening value; however, ammonia concentrations were generally below levels of concern in other drainages. In all drainages, copper concentrations were higher than ecological screening values most frequently (exceeding the ecological screening values for acute exposures in 65-94% of the samples). Chlorine concentrations exceeding the acute water quality criterion were observed in 14 and 35% of samples in two of three drainages. The ecological screening values were exceeded most frequently in Goose Creek and the Upper Tar River drainages; concentrations rarely exceeded ecological screening values in the Swift Creek drainage except for copper. The site-specific risk assessment approach provides valuable information (including site-specific risk estimates and ecological screening values for protection) that can be applied through regulatory and nonregulatory means to improve water quality for mussels where risks are indicated and pollutant threats persist.