Chronic Water Quality Criteria Research Articles

Water quality criteria derivation and ecological risk assessment for ibuprofen, a common antifever drug in China

Ibuprofen, an extensively consumed antifever drug, has been inevitably recorded in various aquatic environments in China. However, water quality criteria (WQC) are rarely derived, thereby hindering the ecological risk assessment for this emerging pollutant. This study, therefore, aims to determine the WQC for IBU by screening toxicity data of freshwater and seawater species residing in China and simulating the species sensitivity distribution curves. The ecological risk of IBU in the aquatic environment of China was subsequently assessed through hazard quotient and margin of safety at 10% methods. A total of 15 acute and 9 chronic toxicity data were collected from the literature, and the acute and chronic WQC for IBU were derived as 7.6 mg/L and 2.9 μg/L, respectively. The ecological risk of IBU was generally negligible, with 21.4% of the waters in China at low chronic risk. The long-term effects and environmental existence of IBU, however, warrant further concern considering the shortage of ecotoxicology data and the popularity of usage for this well-known pharmaceutical.

Water Quality Criteria and Ecological Risk Assessment of Typical Transition Metals in South Asia.

Transition metal pollution in rivers in South Asia is more serious than in other regions because of the lack of adequate freshwater management measures. Water quality criteria (WQC) for South Asia is urgently needed to protect regional aquatic environments because of the occurrence of transboundary rivers. The present study established non-parametric kernel density estimation species sensitivity distribution (NPKDE-SSD) models and then derived the acceptable hazardous concentration for protection of 95% of all aquatic species (HC5) and WQC of six typical transition metals in South Asia. The results showed that the order of acute and chronic WQC was Mn > Fe > Cd > Zn > Cu > Hg and Cu > Fe > Cd, respectively. A risk assessment of these metals in the Indus River, the Ganges River, the Brahmaputra River, the Meghna River, and the Bagmati River was also carried out. Based on the results, these major rivers in South Asia were highly polluted with transition metals, with significant ecological risks for a large number of aquatic species. This study can contribute to a better understanding of ecological risks in South Asia and provide a scientific basis for the updating of water quality standards and the increase in overall water quality.

When it snows it pours: Increased chloride concentrations in the Cuyahoga River during the last half century

Road salt (NaCl, halite) use in areas with substantial snowfall has increased dramatically since the mid-20th century. However, few studies on chloride loading to the Laurentian Great Lakes or Ohio rivers have been conducted. To that end, we analyzed long-term (1972–2019) chloride data across 10 watersheds obtained as part of the Heidelberg Tributary Loading Program (HTLP) for the Lake Erie, Ohio River, and Grand Lake St. Marys watersheds and found that the Cuyahoga River, which has the greatest percent urban land use, had the highest watershed yield and mean concentrations of chloride for any of the HTLP rivers. Further, we apportioned the data seasonally to determine if river chloride levels were greater during seasons of road salt application (Winter) and snowmelt (Spring). Seasonally, winter levels of chloride exceeded the USEPA chronic water quality criteria concentration of 230 mg/L in more than half of the years of the 21st century, compared to only 1 year exceeding this value in the late 20th century. Further, road salt application is increasing with time in the Cuyahoga, Maumee, and Sandusky River watersheds. This increase is significantly and positively related to winter, spring, and fall mean chloride concentrations in the Cuyahoga River and winter mean chloride concentrations in the Maumee River. Finally, chloride-to-sulfate mass ratios (CSMR) for the Cuyahoga River almost always exceeded the 0.5 value that promotes corrosivity of metal pipes and are increasing with time. Ways to minimize the use of or even replace road salt as a deicer are warranted.

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.

Derivation of water quality criteria for glyphosate and its formulations to protect aquatic life in China.

Extensive use of the herbicide glyphosate leads to a high detection rate in the environment and potential risks to nontarget aquatic life. China ranks first globally in the production and consumption of glyphosate, but there are no glyphosate water quality criteria (WQCs) for protecting aquatic life. Here, data on the acute and chronic toxicity of glyphosate and glyphosate-based formulations (GBFs) to freshwater aquatic life were collected and screened. Significant differences in species sensitivity distributions (SSDs) and toxicity values for acute or chronic toxicity were found between glyphosate and GBFs. The hazardous concentrations for 5% of species (HC5) of glyphosate or GBFs between native and nonnative species were different, and native species were found to be more sensitive to the toxicity of glyphosate. The acute and chronic WQCs derived with the SSD method for glyphosate based on the toxicity data for native species in China were 3.35 and 0.26mg/L, respectively, and those found for GBFs were 0.21 and 0.005mg/L, respectively. The WQCs in this study were quite different from those estimated using similar statistical extrapolation methods in other countries, which reflects the differences in species sensitivity to glyphosate toxicity in different regions. The hazard quotients (HQs) were calculated based on the WQCs and concentrations of glyphosate in some surface waters in China and indicated that glyphosate exhibits medium or high hazard risk in some samples of Tai Lake, surface water in Guiyang, fishpond water in Chongqing, rural drinking water, and surface water and reservoir water in Henan Province. The WQCs of glyphosate and GBFs have scientific significance for the exposure and pollution control of herbicide formulations and the protection of aquatic life in China.

Combined effects of copper, nickel, and zinc on growth of a freshwater mussel (Villosa iris) in an environmentally relevant context.

Trace metals rarely contaminate freshwaters independently, hence regulatory limits based on single-metal toxicity may be underprotective of aquatic life. This could be especially the case for rare and sensitive fauna like freshwater mussels, such as those suppressed in the Clinch and Powell Rivers in eastern USA where trace metals are long-term contaminants but at concentrations below regulatory limits. We hypothesized metal mixtures may be exerting combined effects on mussels, resulting in greater toxicity than would be predicted based on single-metal exposures. To test that hypothesis, we conducted two experiments exposing juvenile rainbow mussels (Villosa iris) for 42 days to dissolved copper, nickel, and zinc, individually and in three-metal mixtures, in an environmentally-relevant context of water with chemistry (hardness 155mg/L as CaCO3, dissolved organic carbon 1.7-2.3mg/L, pH 8.4) similar to that of the Clinch River, which receives alkaline mine drainage. We used a toxic unit approach, selecting test concentrations based on literature values for the lower of 28-day survival or growth (length) effect concentrations for Villosa iris or Lampsilis siliquoidea (fatmucket). Our first experiment confirmed survival and growth effects when acute and chronic water quality criteria, respectively, are approached and/or exceeded. Our second experiment, at lower concentrations, showed no effects on survival but combined effects on growth were evident: a mixture of Cu, Ni, and Zn (7.2±1.2, 65.3±6.1, 183±32μg/L, respectively) inhibited growth (dry weight) by 95% versus 73%, 74%, and 83% inhibition for single-metal exposures to Cu, Ni, and Zn of similar concentration (8.0±1.1, 63.5±4.8, 193±31μg/L, respectively). Furthermore, a mixture of Cu, Ni, and Zn with individual concentrations 21%, 29%, and 37% of their water quality criteria (3.4±1.2, 21.8±1.8, and 62.1±8.4µg/L, respectively) inhibited growth (dry weight) by 61% relative to controls. Our observation of combined effects suggests that regulatory limits based on single-metal toxicity may be underprotective of freshwater mussels when multiple metals are present.

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.

Chronic arsenate exposure affects amphipod size distribution and reproduction.

Arsenate (As V) is the predominant inorganic species of arsenic in oxic aquatic environments. Chronic water quality criteria for arsenate have not been established due to the scarcity of relevant studies on its impact on aquatic biota. We examined the acute and chronic effects of arsenate on the benthic amphipod Leptocheirus plumulosus, an important test organism for ecotoxicological studies. We determined that a concentration of 1,971 µg/L arsenate induced 50% mortality (LC50) in juveniles in 96-hr water only exposure. Subsequently, we tested the efficacy of a 42-day sediment bioassay to determine chronic population-level effects. Specifically, we analyzed the survivorship, size distribution, reproduction and offspring sex ratio of this amphipod to a sublethal concentration of arsenate. The sublethal concentration was determined based on the results of the acute tests. Arsenate (500 µg/L) was added to seawater (20 psu) overlying natural sediments (particle sizes < 250 µm). Fifteen replicate chambers per treatment were employed, each stocked with 20 stage-sorted juvenile amphipods (500–600 µm). Five replicates per treatment were destructively sampled on week 3 and ten replicates were sampled on week 6. Arsenate exposure did not affect the survivorship of parental amphipods, as expected, but it decreased significantly the number of offspring in the largest size classes. By week 6, arsenate-exposed replicates had statistically fewer sexually mature offspring compared to controls, likely because the overall reproduction was suppressed. Arsenate exposed amphipods had significantly fewer offspring than controls by week 6 (9.3 vs. 19.1 per parent), but the sex ratio of the offspring was not altered. Our results indicate that size distribution and reproduction may be more sensitive endpoints than survivorship for the chronic effects of arsenate in oxic systems. The extended 42-day bioassay with Leptocheirus plumulosus is a very promising tool to study the effects of toxicants on population dynamics.

Predicting and comparing chronic water quality criteria from physicochemical properties of transition metals

Criteria continuous concentrations (CCCs) are the scientific basis for making sound environmental management decisions and assessing surface water quality. Transition metals are a group of elements, similar in physicochemical properties perpendicularly and horizontally across the Periodic Table, some of which are widely distributed in aquatic environments and can cause adverse effects on aquatic life and human health. Currently internationally recommended CCCs are available for only seven transition metals. It is challenging to derive CCCs for transition metals based on scarce empirical information. The present study found significant relationships between the suggested CCCs of transition metals and their nine physicochemical properties and an empirical model was developed to satisfactorily predict the CCCs of 56 transition metals by use of the most relevant parameter, r, for protecting aquatic ecosystems. Predicted values were largely consistent with the CCCs and CMCs predicted previously and over 80% predicted CMCs of transition metals are greater than or equal to their CCCs. The present study shows methodological advantages in obtaining CCCs, and provides reliable reference values for setting chronic WQC and assessing risk of transition metals.

Water quality criteria of total ammonia nitrogen (TAN) and un-ionized ammonia (NH3-N) and their ecological risk in the Liao River, China.

Ammonia has drawn great concern worldwide due to its ubiquity in surface water and high toxic effect. In China, ammonia pollution issues in the Liao River were highlighted from the Ministry of Ecology and Environment annual report. In this study, water quality criteria (WQC) for two types of ammonia (total ammonia nitrogen (TAN) and un-ionized ammonia (NH3-N)) and related temporal concentration distributions and ecological risks in the Liao River were investigated. For sampling sites (2014) and national monitoring sites (2008, 2013, 2016, 2017 and 2018) of the Liao River, there were seasonal variations identified for TAN and NH3-N. More specifically, high concentrations of TAN and NH3-N occurred separately in winter and summer, and there were increasing trends for TAN and NH3-N from 2013 to 2018. The acute and chronic WQC values for TAN based on the toxicity values of the Liao River species were 16.86 and 4.39 mg/L (pH of 7.0 and temperature of 20 °C), and the acute and chronic WQC values for NH3-N were 0.067 and 0.017 mg/L. The exceedance probabilities of 5% species affected for long-term exposure of TAN and NH3-N were ≥30% in 2014. In addition, the increasing trend of concentrations and ecological risks posed by NH3-N from 2013 should be paying more attention. This study could provide useful information for ammonia environmental risk management in China and ecological risk assessment procedure for NH3-N and TAN exposure in similar surface waters worldwide.

Chronic Toxicity of 4-Nonylphenol to Two Unionid Mussels in Water-Only Exposures.

Limited studies indicate that mussels are generally insensitive to organic chemicals; however, these studies were conducted in acute or short-term exposures, and little is known about the chronic sensitivity of mussels to organic chemicals. We evaluated the chronic (28days) toxicity of 4-nonylphenol (4-NP) to two commonly tested species of mussels: fatmucket (Lampsilis siliquoidea) and rainbow mussel (Villosa iris). By the end of the 28days chronic exposures, mean survival was ≥93% in all treatments, but the mean dry weight and biomass of mussels at the highest exposure concentrations were significantly reduced relative to the control. The 20% effect concentrations were similar between the two species. When compared to all other tested species, fatmucket and rainbow mussels are among the top four most sensitive species to 4-NP. However, U.S. Environmental Protection Agency chronic water quality criterion of 6.6μg 4-NP/L should protect the two mussel species.

Protectiveness of Cu water quality criteria against impairment of behavior and chemo/mechanosensory responses: An update.

A meta-analysis was conducted of studies that reported behavior and chemo/mechanosensory responses by fish, amphibians, and aquatic invertebrates in Cu-containing waters and also reported sufficient water chemistry for calculation of hardness-based and biotic ligand model (BLM)-based water quality criteria (WQC) for Cu. The calculated WQC concentrations were then compared with the corresponding 20% impairment concentrations (IC20) of Cu for those behavior and chemo/mechanosensory responses. The hardness-based acute and chronic WQC for Cu would not have been protective (i.e., the IC20 would have been lower than the WQC) in 33.6 and 26.2%, respectively, of the 107 combined behavior- and chemo/mechanosensory-response cases that also had adequate water chemistry data for BLM-based WQC calculations (32.7% inconclusive). In comparison, the BLM-based acute and chronic WQC for Cu would not have been protective in only 10.3 and 4.7%, respectively, of the same 107 cases (29.9% inconclusive). To improve evaluations of regulatory effectiveness, researchers conducting aquatic Cu toxicity tests should measure and report complete BLM-input water chemistry and bracket the hardness-based and BLM-based WQC concentrations for Cu that would be applicable in their exposure waters. This meta-analysis demonstrates that, overall, the BLM-based WQC for Cu were considerably more protective than the hardness-based WQC for Cu against impairment of behavior and chemo/mechanosensory responses. Environ Toxicol Chem 2018;37:1260-1279. © 2018 SETAC.

A field-based characterization of conductivity in areas of minimal alteration: A case example in the Cascades of northwestern United States

The concentration of salts in streams is increasing world-wide making freshwater a declining resource. Developing thresholds for freshwater with low specific conductivity (SC), a measure of dissolved ions in water, may protect high quality resources that are refugia for aquatic life and that dilute downstream waters. In this case example, methods are illustrated for estimating protective levels for streams with low SC. The Cascades in the Pacific Northwest of the United States of America was selected for the case study because a geophysical model indicated that the SC of freshwater streams was likely to be very low. Also, there was an insufficient range in the SC data to accurately derive a criterion using the 2011, US Environmental Protection Agency field-based extirpation concentration distribution method. Instead, background and a regression model was used to estimate chronic and acute SC levels that could extirpate 5% of benthic invertebrate genera. Background SC was estimated at the 25th centile (33μS/cm) of the measured data and used as the independent variable in a least squares empirical background-to-criteria (B-C) model. Because no comparison could be made with effect levels estimated from a paired SC and biological data set from the Cascades, the lower 50% prediction limit (PL) was identified as an example chronic water quality criterion (97μS/cm). The maximum exposure threshold was estimated at the 90th centile SC of streams meeting the chronic SC level. The example acute SC level was 190μS/cm. Because paired aquatic life and SC data are often sparse, the B-C method is useful for developing SC criteria for other systems with limited data.

Chronic Toxicity of Ferric Iron for North American Aquatic Organisms: Derivation of a Chronic Water Quality Criterion Using Single Species and Mesocosm Data

Iron is a common pollutant in waters near coal and hard rock mine disturbances. The current 1000 µg/L total recoverable chronic criterion for iron (Fe) for protection of aquatic life in the United States was developed using very limited data in 1976 and has not been revised since. To develop a more scientifically based criterion, several chronic laboratory toxicity experiments (> 30 days) were conducted with ferric Fe at circumneutral pH on a taxonomically diverse group of organisms including brown trout (Salmo trutta), mountain whitefish (Prosopium williamsoni), boreal toad tadpoles (Bufo boreas), the oligochaete worm Lumbriculus variegatus, the mayfly Hexagenia limbata, and the planarian Dugesia dorotocephala. Results of these tests and those of previously published toxicity data were used to derive a Final Chronic Value (FCV) of 499 µg/L by using the US Environmental Protection Agency’s recommended methods based on single species toxicity tests. In addition to single species toxicity tests, ferric Fe toxicity experiments (10 days) were performed on mesocosms containing naturally colonized communities of benthic macroinvertebrates. Fourteen genera in the mesocosms occurred at sufficient densities to estimate an iron concentration resulting in 20% reduction in abundance (EC20). Three of these taxa had EC20s less than the FCV of 499 µg/L derived from single species tests: the mayfly Epeorus sp. (335 µg/L), the caddisfly Micrasema sp. (356 µg/L), and midge Tanytarsini (234 µg/L). When mesocosm results were included, the FCV was lowered to 251 µg/L. These findings support the suggestion that modernization of water quality criteria should include data generated from mesocosm experiments and other lines of evidence.

Acute and chronic toxicity of aluminum to a unionid mussel (Lampsilis siliquoidea) and an amphipod (Hyalella azteca) in water-only exposures.

The US Environmental Protection Agency (USEPA) is reviewing the protectiveness of the national ambient water quality criteria (WQC) for aluminum (Al) and compiling a toxicity data set to update the WQC. Freshwater mussels are one of the most imperiled groups of animals in the world, but little is known about their sensitivity to Al. The objective of the present study was to evaluate acute 96-h and chronic 28-d toxicity of Al to a unionid mussel (Lampsilis siliquoidea) and a commonly tested amphipod (Hyalella azteca) at a pH of 6 and water hardness of 100 mg/L as CaCO3 . The acute 50% effect concentration (EC50) for survival of both species was >6200 μg total Al/L. The EC50 was greater than all acute values in the USEPA acute Al data set for freshwater species at a pH range of 5.0 to <6.5 and hardness normalized to 100 mg/L, indicating that the mussel and amphipod were insensitive to Al in acute exposures. The chronic 20% effect concentration (EC20) based on dry weight was 163 μg total Al/L for the mussel and 409 μg total Al/L for the amphipod. Addition of the EC20s to the USEPA chronic Al data set for pH 5.0 to <6.5 would rank the mussel (L. siliquoidea) as the fourth most sensitive species and the amphipod (H. azteca) as the fifth most sensitive species, indicating the 2 species were sensitive to Al in chronic exposures. The USEPA-proposed acute and chronic WQC for Al would adequately protect the mussel and amphipod tested; however, inclusion of the chronic data from the present study and recalculation of the chronic criterion would likely lower the proposed chronic criterion. Environ Toxicol Chem 2018;37:61-69. Published 2017 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.

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.

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.

Keystone indices probabilistic species sensitivity distribution in the case of the derivation of water quality criteria for copper in Tai Lake.

An alternative method for species sensitivity distribution (SSD) that considers the interaction between species and the community importance is illustrated in this article. First, a food web based on the relationship between predator and prey was constructed, and the keystone indices of species were obtained based on the food web. Then, the probability density distribution of the sensitivity for each species was derived from all of the available endpoints of each species. Finally, the species sensitivity distribution for ecosystem was constructed by sampling a specific number of values from the probability density distribution of the sensitivity for each species. Data of copper toxicity to the aquatic organisms in Tai Lake were selected to derived site-specific water quality criteria (WQC). Ninety-seven endpoints of acute toxicity for 47 species and 188 endpoints of chronic toxicity for 29 species were included, and the acute and chronic WQC developed by keystone indices probabilistic species sensitivity distribution (K-PSSD) were 4.982μg/L and 0.965μg/L, respectively. Results showed that the aquatic organisms of Tai Lake might be underprotected. Compared with the SSD, the K-PSSD coped with the interactions between species, the community importance, and the intraspecies and interspecies variation more effectively and was better at depicting the tendency and information of raw data. The K-PSSD was especially applicable to site-specific WQC and provided an alternative or supplement to the SSD.

Histological changes, apoptosis and metallothionein levels in Triturus carnifex (Amphibia, Urodela) exposed to environmental cadmium concentrations

The aim of this study was to verify if the freshwater safety values established from the European Community (1998) and the Italian Ministry of Health (2001) for cadmium (44.5nM/L in drinking water and 178nM/L in sewage waters) were safe for amphibians, since at these same concentrations cadmium induced endocrine disruption in the newt Triturus carnifex. Adult male specimens of T. carnifex were exposed daily to cadmium (44.5nM/L and 178nM/L as CdCl2, nominal concentrations), respectively, during 3- and 9-months; at the same time, control newts were exposed to tap water only. The accumulation of cadmium in the skin, liver and kidney, the levels of metallothioneins in the skin and the liver, the expression of metallothionein mRNA in the liver, as well as the presence of histological alterations and of apoptosis in the target organs were evaluated. The 9-months exposure induced cadmium accumulation in all the tissues examined; moreover, histological changes were observed in all the tissues examined, irrespective of the dose or the time of exposure. Apoptosis was only detected in the kidney, whereas metallothioneins and metallothionein mRNA did not increase. This study demonstrates that the existing chronic water quality criterion established for cadmium induces in the newt T. carnifex cadmium accumulation and histological alterations in the target organs examined. Together with our previous results, showing that, at these same concentrations, cadmium induced endocrine disruption, the present results suggest that the existing chronic water quality criterion for cadmium appears to be not protective of amphibians.

Bioavailability and Effects of Ingested Metals on Aquatic Organisms

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