Aquatic risk assessment of copper in freshwater and saltwater ecosystems of South Florida

Synergistic effect of chloroquine and copper to the euryhaline rotifer Proales similis

Chloroquine (CQ) has been widely used for many years against malaria and various viral diseases. Its important use and high potential to being persistent make it of particular concern for ecotoxicological studies. Here, we evaluated the toxicity of CQ alone and in combination with copper (Cu) to the euryhaline rotifer Proales similis. All experiments were carried out using chronic toxicity reproductive five-day tests and an application factor (AF) of 0.05, 0.1, 0.3, and 0.5 by multiplying the 24-h LC₅₀ values of CQ (4250 µg/L) and Cu (68 µg/L), which were administered in solution. The rate of population increase (r, d^-1) ranged from 0.50 to 52 (controls); 0.20 to 0.40 (CQ); 0.09 to 0.43 (Cu); and -0.03 to 0.30 (CQ-Cu) and showed significant decrease as the concentration of both chemicals in the medium increased. Almost all tested mixtures induced synergistic effects, mainly as the AF increased. We found that the presence of Cu intensifies the vulnerability of organisms to CQ and vice versa. These results stress the potential hazard that these combined chemicals may have on the aquatic systems. This research suggests that P. similis is sensitive to CQ as other standardized zooplankton species and may serve as a potential test species in the risk assessment of emerging pollutants in marine environments.

Single and combined toxicity of polystyrene nanoplastics and copper on Platymonas helgolandica var. tsingtaoensis: Perspectives from growth inhibition, chlorophyll content and oxidative stress

The combined toxic effects of nanoplastics and heavy metals on aquatic organisms have attracted widespread attention; however, the results are inconsistent and the mechanisms remain unclear. In this study, the single and combined toxicity effects of Cu and two types of polystyrene nanoplastics (PS-NPs; 50 nm PS and 55 nm PS-COOH) on Platymonas helgolandica var. tsingtaoensis were investigated, including growth inhibition, chlorophyll content, and oxidative stress. An adverse dose-response relationship on growth inhibition was found in the Cu treatment groups, which was related to the decrease in chlorophyll content and damage to cell membranes. The growth inhibitory effect of PS-NPs on microalgae increased with exposure time and concentration, and no significant difference was found in the two types of PS-NPs because of the negligible contribution of functional groups. A more significant increase in chlorophyll content was found in PS treatments than in PS-COOH treatments at 96 h because of the microscale aggregates formed by PS. Higher concentrations (≥ 50 mg/L) of PS-NPs caused membrane lipid peroxidation, which might be responsible for growth inhibition. In the combined exposure experiments, a synergistic effect on the growth inhibition rate was obtained using the independent action model and Abbott model. Combined exposure triggered more severe oxidative damage to the microalgae. Adsorption experiment results showed that there was no adsorption between PS-NPs and Cu, while the interaction of Cu and algal cells could be promoted due to the presence of the PS-NPs, which explained the increasing combined toxicity. This study could improve our understanding of the combined toxicity of nanoplastics and heavy metals and could provide a new explanation for the mechanism of combined toxicity.

The ECOTOXicology Knowledgebase: A Curated Database of Ecologically Relevant Toxicity Tests to Support Environmental Research and Risk Assessment

The need for assembled existing and new toxicity data has accelerated as the amount of chemicals introduced into commerce continues to grow and regulatory mandates require safety assessments for a greater number of chemicals. To address this evolving need, the ECOTOXicology Knowledgebase (ECOTOX) was developed starting in the 1980s and is currently the world's largest compilation of curated ecotoxicity data, providing support for assessments of chemical safety and ecological research through systematic and transparent literature review procedures. The recently released version of ECOTOX (Ver 5, www.epa.gov/ecotox) provides single-chemical ecotoxicity data for over 12,000 chemicals and ecological species with over one million test results from over 50,000 references. Presented is an overview of ECOTOX, detailing the literature review and data curation processes within the context of current systematic review practices and discussing how recent updates improve the accessibility and reusability of data to support the assessment, management, and research of environmental chemicals. Relevant and acceptable toxicity results are identified from studies in the scientific literature, with pertinent methodological details and results extracted following well-established controlled vocabularies and newly extracted toxicity data added quarterly to the public website. Release of ECOTOX, Ver 5, included an entirely redesigned user interface with enhanced data queries and retrieval options, visualizations to aid in data exploration, customizable outputs for export and use in external applications, and interoperability with chemical and toxicity databases and tools. This is a reliable source of curated ecological toxicity data for chemical assessments and research and continues to evolve with accessible and transparent state-of-the-art practices in literature data curation and increased interoperability to other relevant resources. Environ Toxicol Chem 2022;41:1520-1539. © 2022 SETAC. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

A Mesoscopic Simulation Approach Based on Metal Fibre Characterization Data to Evaluate Brake Friction Performance

The coefficient of friction (COF) is an important parameter when evaluating brake system performance. It is complex to predict friction due to its dependence on parameters, such as sliding velocity, contact pressure, temperature, and friction material mixtures. The aim of this work is to evaluate the macroscopic COF of a disc brake system under specific braking conditions by a meso-scale approach, using a cellular automaton simulation where the friction material mixture is modelled starting from its basic components. The influence of the local components in contact is taken into account. Simulated COF values are in line with the experimental values.

Copper impair autophagy on zebrafish (Danio rerio) gill epithelium

Copper (Cu) is an essential element for organism's metabolism, being controversially listed as a priority pollutant. Importantly, the toxicity of Cu has been linked to several cell death pathways. Thus, this study aimed to assess if macroautophagic pathways are triggered by Cu in zebrafish gill, the main target of waterborne pollutants. The electron microscopy findings indicated that Cu induced profound impacts on zebrafish gill structure and functions, being this tissue a biomarker sensitive enough to indicate early toxic effects. The findings also support a clear impairment of autophagy, througth the absence of phagossomes and the significant down-regulation mRNA transcript levels of microtubule-associated protein light chain 3 (LC3). The reduction of LC3 levels was often associated to an increase of apoptotic activation, indicating that the inhibition of macroautophagy triggers apoptosis in zebrafish gills. This study highlighted that the autophagic down-regulation might be affected through the activation of other cell death signaling pathway.

Hardness-dependent water quality criteria for cadmium and an ecological risk assessment of the Shaying River Basin, China

Hardness is one important water quality parameter that influences the toxicity of cadmium. Several studies have derived water quality criteria (WQC) for cadmium, but most of these studies did not consider environmental factors. Moreover, few studies considered environmental factors when carrying out ecological risk assessments (ERA) based on environmental factors. In this research, six native aquatic organisms in the Shaying River were adopted to conduct toxicity tests for cadmium. By combining published toxicity data for cadmium with hardness values and toxicity data from this study, hardness-dependent WQC were established. When normalized to a hardness of 100 mg/L CaCO₃, the criterion maximum concentration (CMC) of 6.46 μg/L and criterion continuous concentration (CCC) of 1.49 μg/L in the Shaying River Basin were derived according to the USEPA guidelines. The acute predicted no effect concentrations (PNECs) derived by species sensitivity distribution (SSD) methods based on log-logistic, log-normal and Burr Type III models were 1.03, 2.41 and 1.66 μg/L, respectively. Recommended WQC values finally expressed as a function of hardness: (1) CMC=(1.136672-0.041838 × lnH) × e^{0.9969×lnH-2.6676}; and (2) CCC=(1.101672-0.041838 × lnH) × e^{1.0083×lnH-6.1156}. In addition, three tiers of ERA of cadmium in surface waters were conducted based on hardness obtained during different seasons in the Shaying River using the hazard quotient (HQ), the margin of safety (MOS₁₀), and the joint probability (JPC) methods. In tiered 1, 2, and 3 ERA, cadmium exposure concentrations were standardized to a hardness of 100 mg/L. The three levels of the ERA method in the tiered framework gave consistent results: the ecological risks of cadmium in the Shaying River Basin were at acceptable levels. The present study provides a reference for the derivation of WQC and risk assessment of pollution affected by differences in aquatic species and water quality factors such as hardness.

Ecological risk assessment of heavy metal pollution in the water of China's coastal shellfish culture areas

In order to learn about the status of heavy metals and ecological risks in the water of thirteen China's costal shellfish culture areas, principal component analysis was applied to analyze the distributions of five kinds of heavy metal, while the safety threshold method was employed to evaluate the ecological risks. The results showed that among the 13 shellfish culture areas, the average metal concentrations were in the order of Zn > Cu > Pb > Hg > Cd, and all heavy metals were below the second standards for sea water quality of China. The distribution of heavy metals in 13 shellfish culture areas was reflected by two principal components with the contribution rates of F1(Cu) and F2(Zn, Pb) were 36.14% and 23.40%,respectively,which was less affected by economic and geographical differences. The ecological risks assessment of five kinds of heavy metals showed that MOS10 was more than one; the probabilities of five heavy metals affecting more than 10% of aquatic organisms were 49.52%, 24.11%, 17.49%, 22.05%, and 5.66%, respectively, the ecological risk of five main heavy metals was in order Cu > Zn > Cd > Pb > Hg. In the selected thirteen shellfish culture areas, the value of msPAF of seven culture areas was higher than 20%, indicating these areas are highly ecologically contaminated by heavy metals, and the other four shellfish culture areas with value of 0, indicating that these areas have no ecological risk of heavy metals pollution.

A Multi-Scale Simulation Approach to Investigate Local Contact Temperatures for Commercial Cu-Full and Cu-Free Brake Pads

Copper from vehicles disc brakes is one main contributor of the total copper found in the environment. Therefore, the U.S. Environmental Protection Agency (EPA) and the automotive industries started the Copper-Free Brake Initiative. The pad friction material is essentially composed of a binder, fillers, reinforcing fibres and frictional additives. Copper and brass fibres are the most commonly used fibres in brake pads. There is a need to understand how the contact temperature distribution will change if copper-based fibres are changed to steel fibres. The aim of this work is, therefore, to investigate how this change could influence the local contact temperatures. This is done by developing a multi-scale simulation approach which combines cellular automaton, finite element analysis (FEA) and computational fluid dynamics (CFD) approaches with outputs from inertia brake dyno bench tests of Cu-full and Cu-free pads. FEA and thermal-CFD are used to set the pressure and the temperature boundary conditions of the cellular automaton. The outputs of dyno tests are used to calibrate FEA and CFD simulations. The results of the study show lower peaks in contact temperature and a more uniform temperature distribution for the Cu-free pad friction material.

Combined effects of nanoplastics and copper on the freshwater alga Raphidocelis subcapitata

Nanoplastics are recognized as able to interact with other pollutants including heavy metals, and with natural organic matter, with implications for the potential risks to biota. We investigated the interaction of carboxylated polystyrene nanoparticles (PS-COOH NPs) with copper (Cu) and algal exudates (EPS) and how such interaction could affect Cu toxicity towards the freshwater microalga Raphidocelis subcapitata. PS-COOH NPs behavior in the presence of Cu and EPS was determined by dynamic light scattering (DLS), while PS-COOH NPs surface interaction with Cu ions and EPS was investigated by fluorimetric analysis. ICP-MS was used to test Cu ion adsorption to PS-COOH NPs in the presence and absence of algae. The interaction between PS-COOH NPs and the algal cell wall was assessed by fluorescence microscopy. Short- and long-term toxicity tests were carried out in parallel to assess the impact of PS-COOH NPs on algal growth. Results showed altered nanoparticle surface charge and hydrodynamic diameter following algal EPS exposure, supporting the hypothesis of a protein corona formation. In contrast, no absorption of Cu ions was observed on PS-COOH NPs, either in the presence or absence of algae. No differences on algal growth inhibition were observed between exposure to Cu only, and to Cu in combination with PS-COOH NPs, in short-term as well as long-term tests. However, after 72 h of exposure, the adsorption of PS-COOH NPs to algal cell walls appeared to correspond to morphological alterations, revealing potential disturbances in the mitotic cycle. Our findings confirm the ability of PS-COOH NPs to interact with EPS as shown for other nanomaterials. Environmentally realistic exposure scenarios are thus needed for evaluating nanoplastic toxicity, as nanoparticles will not maintain their pristine nature once released into natural media. Prolonged exposure and use of different end-points such as cell morphological changes and EPS production seem more reliable for the investigation of nanoplastic/algal cell interactions which can drive food chain transfer of nanoplastics and ultimately toxicity.

Development of marine water quality criteria for inorganic mercury in China based on the retrievable toxicity data and a comparison with relevant criteria or guidelines

The development of marine water quality criteria (WQC) in China has been insufficient because data on the toxicity of pollutants for marine organisms based on the species sensitivity distribution (SSD) method are lacking. The Chinese aquatic environmental quality standards, including those for seawater, were derived from the developed countries. Therefore, establishing Chinese marine WQC is crucial for identifying the sensitivity of marine species in China and will improve their protection from threats. Mercury (Hg) is one of the primary pollutants commonly exceeding Chinese seawater quality standards. Several countries have developed their marine WQC for inorganic Hg in the past decades, but no study has been conducted in China. In this study, 45 acute toxicity and 14 chronic toxicity data of inorganic Hg on the marine species which inhabit in China were obtained mainly from the ECOTOX database, the CNKI, and the Google Scholar. The acute and chronic hazardous concentrations for 5% of the species (HC₅) were calculated based on the best-fit distribution model Sweibull. The criteria for maximum and continuous concentrations of 1.30 and 0.66 μg/L, respectively, for inorganic Hg to protect marine organisms in China were derived by halving the HC₅ values. The criteria were comparable to those of the United States, Australia, and the European Union countries, indicating the general applicability of WQCs developed based on the classical SSD method using different species groups. This study may provide valuable information for assessing marine ecological risk in China.

Nanoparticle- and microparticle-based luminescence imaging of chemical species and temperature in aquatic systems: a review

Most aquatic systems rely on a multitude of biogeochemical processes that are coupled with each other in a complex and dynamic manner. To understand such processes, minimally invasive analytical tools are required that allow continuous, real-time measurements of individual reactions in these complex systems. Optical chemical sensors can be used in the form of fiber-optic sensors, planar sensors, or as micro- and nanoparticles (MPs and NPs). All have their specific merits, but only the latter allow for visualization and quantification of chemical gradients over 3D structures. This review (with 147 references) summarizes recent developments mainly in the field of optical NP sensors relevant for chemical imaging in aquatic science. The review encompasses methods for signal read-out and imaging, preparation of NPs and MPs, and an overview of relevant MP/NP-based sensors. Additionally, examples of MP/NP-based sensors in aquatic systems such as corals, plant tissue, biofilms, sediments and water-sediment interfaces, marine snow and in 3D bioprinting are given. We also address current challenges and future perspectives of NP-based sensing in aquatic systems in a concluding section. Graphical abstract ᅟ.

Suppressive effects of thermal-treated oyster shells on cadmium and copper translocation in maize plants

The effect of varied concentrations of thermal-treated oyster shells (TOS) on the suppression of cadmium (Cd) and copper (Cu) uptake and translocation into the shoots of maize plants was examined. Maize plants were grown in Cd- and Cu-contaminated Andosol for 70 days. The concentration of mobile Cd (extracted with 1 M NH₄NO₃) decreased with increasing TOS applications, whereas an increase in the concentration of mobile Cu in soil resulted from cumulative TOS additions. The addition of 2% TOS had no prohibitive effects on Cd uptake in maize shoots, but the 4 and 8% TOS treatments decreased Cd accumulation in shoots by 41 and 59%, respectively. The possible mechanisms underlying Cd suppression in maize shoots were the enhanced Cd adsorption caused by pH-induced increases in the negative charge of the soil and the antagonistic effects of Ca resulting from competition for exchange sites at the root surface. Cu accumulation in maize shoots increased by 34, 51, and 53% with the addition of 2, 4, and 8% TOS, respectively, but this increase was not observed for Cd accumulation. These results suggested that, in multi-metal-contaminated soils, attention should be paid to the potential mobility of target metals and the pH of the contaminated soil. From a plant physiological perspective, contaminated soils slightly reduced photosynthetic performance. However, the addition of TOS to the soil at levels higher than 4% substantially decreased photosynthetic performance, indicating that CaO-based suppressants at critical loads might damage the net photosynthetic rates of sensitive maize plants.

pH-dependent ecological risk assessment of pentachlorophenol in Taihu Lake and Liaohe River

Pentachlorophenol (PCP) has been reported toxic to aquatic organisms, and it frequently occurs at relatively high concentrations in most Chinese waters due to the re-emergence of schistosomiasis since 2003. Several studies about Water Quality Criteria (WQC) for PCP had been performed to protect the aquatic ecosystem, but in most of these studies the toxicity data were not properly analyzed (e.g. screening and processing methods). Moreover, little study was carried out on the ecological risk assessment (ERA) based on environmental factors. In this study, through collecting published native toxicity data of PCP along with relationships between toxicity and pH, pH-dependent WQC was established using a standardized scientific statistical method in China. The Criterion Maximum Concentration (CMC) and Criterion Continuous Concentration (CCC) were expressed as a function of pH. These were (1) CMC = exp(1.361×pH-8.034) and (2) CCC = exp(1.361×pH-10.434). At pH 7.8, the derived CMC and CCC were 13.21 and 1.20μg/L, respectively. In addition, four tiers of the ERA were conducted based on pH for different waterbodies at different seasons. In tiered 1, 2, 3 and 4 ERA, PCP exposure concentrations were standardized to that at pH 7.8. Results showed that all levels of ERA method in the tiered framework were consistent with each other, and the risks of PCP in Liaohe river of wet season, Taihu lake and Liaohe river of dry season increased successively. The Hazard quotient (HQ) method indicated that small fluctuations in pH would lead to misleading hazard results. PCP concentrations of 8.66μg/L at pH 7.37 in one site posed more risk than PCP of 9.57μg/L at pH 7.93 in another site. The joint probability suggested that ecological risks may exist 11.84% in the dry season and 1.51% in the wet season in Liaohe River, and 4.98% in Taihu Lake, respectively while 5% thresholds (HC₅) were set up to protect aquatic organisms. We hope this work could provide more information to manage and control PCP pollution in Taihe Lake and Liaohe River.

Distribution, diffusive fluxes, and toxicity of heavy metals and PAHs in pore water profiles from the northern bays of Taihu Lake

Pore water plays a more significant role than do sediments in pollutant cycling dynamics. Also, concentrations of pollutants in pore water provide important information about their bioavailability or eco-toxicity; however, very few studies have focused on this topic. In this study, four duplicate sediment cores from three typical northern bays as well as the central part of Taihu Lake were collected to investigate the distribution, diffusive fluxes, and toxicity of heavy metals and polycyclic aromatic hydrocarbons (PAHs) in pore water profiles, which will be good in understanding the mobility and toxicity of these toxic pollutants and achieving better environmental management. The diffusive fluxes of heavy metals across the sediment-water interface was estimated through Fick's First Law, and the toxicity of heavy metals and PAHs in pore water was assessed by applying a water quality index (interstitial water toxicity criteria unit, IWCTU) and a hazard index (HI), respectively. The average concentrations of Cr, Cu, Ni, Pb, and Zn in surface pore water were 18.8, 23.4, 12.0, 13.5, and 42.5 μg L^-1, respectively. Also, concentrations of the selected heavy metals in both overlying water and pore water from Taihu Lake were all lower than the standard values of the environmental quality standards for surface water. The concentrations as the pore water depth increased, and the highest detected concentrations of heavy metals were recorded between 3 and 5 cm below the sediment surface. The average diffusive fluxes of these metals were 27.3, 24.8, 7.03, 7.81, and -3.32 μg (m² day)^-1, respectively, indicating export from sediment into overlying water, with the exception of Zn. There was a potential risk of toxicity, mainly from Pb and Cu, indicating that heavy metals in pore water had slight to moderate impact on sediment-dwelling organisms by values of the IWCTU and the Nemeraw index. The total PAH concentrations in pore water were higher than those in overlying water, and such gradient implies a potential flux of PAHs from pore water to overlying water. The average HI value of PAHs in surface pore water showed no or low ecological risk. While there may be occasional risk due to the HI values in some sites being greater than 1, the dominant contributors were carcinogenic PAHs. Because of their potential biological impact, heavy metals and PAHs and their comprehensive toxic effects in pore water should be given priority attention to keep the safety of Taihu Lake.

Copper toxicity and the influence of water quality of Dongnai River and Mekong River waters on copper bioavailability and toxicity to three tropical species

The present study investigated copper (Cu) toxicity and the influence of water quality characteristics of Dongnai River and Mekong River (Vietnam) surface waters to three tropical species; Daphnia lumholtzi, Ceriodaphnia cornuta, and Danio rerio. The river waters had a range of water quality parameters that modify Cu bioavailability and toxicity. The range of total hardness, alkalinity, pH and dissolved organic carbon were 15-64 mg/L as CaCO3, 18-58 mg/L as CaCO3, 6.62-7.88, and 6.9-14.7 mg/l, respectively. The US EPA acute toxicity test method with a modification to the light photoperiod and temperature for tropical organisms was used to investigate Cu toxicity. Result of the present study found that Cu produced toxic effect to the studied organisms at low concentrations. The 48-h LC50 ranged from 3.92 to 8.61 µg/l, 2.92-9.56 µg/l, and 15.71-68.69 µg/l dissolved Cu for D. lumholtzi, C. cornuta, and D. rerio, respectively. In general, water quality had an influence on Cu bioavailability and toxicity to the studied organisms. The toxicity of Cu was higher in water with lower hardness, DOC, and/or pH. The present study indicates a contribution of Cu hydroxide and carbonate to Cu bioavailability to Mekong organisms. Results of the present study will be used for calibrating the US Cu Biotic Ligand Model (BLM) to Mekong River water and organisms in support of application of the BLM for setting site-specific Cu water quality guidelines in the ecosystem of the Lower Mekong River Basin.

Present knowledge and perspectives on the role of copper in brake materials and related environmental issues: A critical assessment

This critical review presents several aspects related to the use of copper as a main component in brake pads in road vehicles. The compositions of these materials are attracting increasing interest and concern due to the relative contribution of wear products to particulate matter emissions in the environment as a result of braking action even though there has been a reduction in exhaust products from internal combustion engines. We review the data on the main wear mechanisms in brake systems and highlight the positive role of copper. However, similar to other heavy metal emissions, even the release of copper into the atmosphere may have important environmental and health effects. Thus, several replacement strategies are being pursued, and the positive and negative features will be critically reviewed. Additionally, the future perspectives in materials development will be discussed.

Probabilistic ecological risk assessment of copper in Chinese offshore marine environments from 2005 to 2012

The objective of the present study was to conduct a probabilistic assessment of risk posed by copper found in the coastal marine environment of China from 2005 to 2012. This was achieved by applying a tiered ecological risk assessment (ERA) approach for characterization of risks of concentrations of copper from nationwide marine water monitoring program. The results show that from 2005 to 2012 the overall trend of hazard quotients (HQs) in the coastal marine environment of China the proportion of locations that exceed a HQ of 1.0 decreased from 64% in 2005 to 31% in 2012. While this indicates an overall improvement of the environment, there still have potential ecological risks in the most of the area, especially for the major gulfs of Liaodong and Bohai Bays and Yellow River Estuary. In addition, probabilities of exceeding the toxicity threshold for 5% of species were 27.6%, 5.4%, 4.9%, 0.8%, 0.4%, 1.0%, 1.8% and 0.12% annually between 2005 and 2012, respectively.

Ecological risk assessment and sources of heavy metals in sediment from Daling River basin

To investigate the distribution, source, and ecological risk of heavy metals in Daling River basin, 28 surface sediments collected in this region were analyzed by experimental and theoretical methods. Seven heavy metals, including Pb, Cr, Hg, Cu, As, Cd, and Zn, were detected in all samples. Monte Carlo simulation was used to assess the ecological risks of these heavy metals. It was found that the pollution of Cd was the most serious; the ecological risks in Daling River and Bohai Bay were significantly higher than those in estuary, Bohai Sea, and wetland, but overall, the ecological risks of these heavy metals were low to aquatic organisms in Daling River basin at present. Correlation analysis, principal component analysis, and cluster analysis showed that these heavy metals might originate from the same pollution sources located near Daling River and Bohai Bay.

Predicted no-effect concentrations for mercury species and ecological risk assessment for mercury pollution in aquatic environment

Mercury (Hg) exists in different chemical forms presenting varied toxic potentials. It is necessary to explore an ecological risk assessment method for different mercury species in aquatic environment. The predicted no-effect concentrations (PNECs) for Hg(II) and methyl mercury (MeHg) in the aqueous phase, calculated using the species sensitivity distribution method and the assessment factor method, were 0.39 and 6.5×10(-3)μg/L, respectively. The partition theory of Hg between sediment and aqueous phases was considered, along with PNECs for the aqueous phase to conduct an ecological risk assessment for Hg in the sediment phase. Two case studies, one in China and one in the Western Black Sea, were conducted using these PNECs. The toxicity of mercury is heavily dependent on their forms, and their potential ecological risk should be respectively evaluated on the basis of mercury species.

The potential risk assessment for different arsenic species in the aquatic environment

The different toxicity characteristics of arsenic species result in discrepant ecological risk. The predicted no-effect concentrations (PNECs) 43.65, 250.18, and 2.00×10(3)μg/L were calculated for As(III), As(V), and dimethylarsinic acid in aqueous phase, respectively. With these PNECs, the ecological risk from arsenic species in Pearl River Delta in China and Kwabrafo stream in Ghana was evaluated. It was found that the risk from As(III) and As(V) in the samples from Pearl River Delta was low, while much high in Kwabrafo stream. This study implies that ecological risk of arsenic should be evaluated basing on its species.

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.

A toxicity-based method for evaluating safety of reclaimed water for environmental reuses

A large quantity of toxic chemical pollutants possibly remains in reclaimed water due to the limited removal efficiency in traditional reclamation processes. It is not enough to guarantee the safety of reclaimed water using conventional water quality criteria. An integrated assessment method based on toxicity test is necessary to vividly depict the safety of reclaimed water for reuse. A toxicity test battery consisting of lethality, genotoxicity and endocrine disrupting effect was designed to screen the multiple biological effects of residual toxic chemicals in reclaimed water. The toxicity results of reclaimed water were converted into the equivalent concentrations of the corresponding positive reference substances (EQC). Simultaneously, the predicted no-effect concentration (PNEC) of each positive reference substance was obtained by analyzing the species sensitivity distribution (SSD) of toxicity data. An index "toxicity score" was proposed and valued as 1, 2, 3, or 4 depending on the ratio of the corresponding EQC to PNEC. For vividly ranking the safety of reclaimed water, an integrated assessment index "toxicity rank" was proposed, which was classified into A, B, C, or D rank with A being the safest. The proposed method was proved to be effective in evaluating reclaimed water samples in case studies.

Effects of contaminated St. Lucie River saltwater sediments on an amphipod (Ampelisca abdita) and a hard-shell clam (Mercenaria mercenaria)

The St. Lucie estuary (SLE) ecosystem in South Florida has been shown to be contaminated with metals and pesticides. Our earlier studies also showed that aquatic organisms, especially benthic species in the SLE ecosystem, might be potentially at high risk from copper (Cu) exposure. The objectives of this study were to conduct studies with separate groups of organisms exposed to seven field-collected sediment samples from the St. Lucie River according to standard procedures to evaluate toxicity and tissue concentrations of Cu and zinc (Zn). Short term and longer term whole sediment acute toxicity studies were performed with Ampelisca abdita and Mercenaria mercenaria. Analysis of sediment chemical characteristics showed that Cu and Zn are of most concern because their concentrations in 86 % of the sediments were higher than the threshold effect concentrations for Florida sediment quality criteria and the National Oceanic and Atmospheric Administration Screening Quick Reference Tables (SQuiRTs) sediment values. There was no significant effect on survival of the tested organisms. However, increased Cu and Zn concentrations in the test organisms were found. Dry weight of the tested organisms was also inversely related to Cu and Zn concentrations in sediments and organisms. The effects on organism weight and Cu and Zn uptake raise concerns about the organism population dynamics of the ecosystem because benthic organisms are primary food sources in the SLE system and are continuously exposed to Cu- and Zn-contaminated sediments throughout their life cycle. The results of the present study also indicate that Cu and Zn exposures by way of sediment ingestion are important routes of exposure.

Predicted no-effect concentration and risk assessment for 17-[beta]-estradiol in waters of China

Contamination of the aquatic environment by EDCs has received considerable attention from scientists, government officials, and the public. E2, one of the EDCs with high estrogenic effect, has the potential to cause multiple endocrine-disrupting effects, even at small concentrations. In the present review, the toxicity of E2 to aquatic organisms was reviewed. Results of published studies show that, for aquatic species, reproductive effects were the most sensitive endpoint for E2 exposure.Although the risks posed by EDCs have caused much attention, the research on the WQC 'for EDCs is still at the initial stage. It has been suggested in several reports that the PNEC can be regarded as the most appropriate reference value for developing WQC for the EDCs. The SSD method was applied to derive PNECs that were based on reproductive effects endpoints. In the present review, 31 NOECs, based on reproductive effect endpoints for different species, were selected to construct the curve. ThePNEC value was determined to be 0.73 ng E2/L, which could protect the biodiversity of aquatic ecosystems. Moreover, 6 NOECs for multigeneration species were also analyzed in anticipation of sensitivity comparison between the Fa and the F1 generations.When multiple generations of aquatic species were exposed to concentrations no greater than 100 ng E2/L, nearly 71.4% of the F 1 generation individuals were more sensitive to the effects of E2 than those of the Fa generation. This result indicated that different generations of the same species may respond differently to EDCs exposure.Individuals of the F 1 generation were slightly more sensitive than those of the Fa generation,in general. Therefore, protecting the F1 generation of aquatic organisms is particularly important when WQC values for the EDCs are established.Considering the toxic effects of EDCs on reproduction, long-term toxic effects(viz., full-life cycle study and the most sensitive life stage) should be used in settingWQC. Unfortunately, the NOECs of E2 for multigeneration species did not meet the requirement of PNEC derivation for protecting the Fl generation. Therefore, further research results are needed on the Fl generation of aquatic species to provide more insight into what constitutes adequate protection for aquatics lives. In the present review, the PNEC values derived in the study were compared to thePNEC values developed by others, and the results showed that they were highly consistent. In addition, we also compared the PNEC value for E2 to the PNEC value for EE2, a similar estrogen, and the result was also highly consistent when their EEFs were considered. These comparisons affirmed that the method we used for deriving the PNEC value of E2 was reasonable and the PNEC values we derived were acceptable for protecting aquatic organisms. By comparing the PNEC values we calculated to actual E2 concentrations in the natural water environment, we found that E2 in surface waters may pose high risks in many countries, especially China, Japan, the USA, Great Britain, and Italy.

Probabilistic ecological risk assessment of polycyclic aromatic hydrocarbons in southwestern catchments of the Bohai Sea, China

A probability risk assessment was undertaken to study the individual and combined ecological risks induced by six polycyclic aromatic hydrocarbons (PAHs) both in surface water and sediment from southwestern catchments of the Bohai Sea, China. The actual measured PAH concentrations in water and sediment were compared with toxicity effect data (the 10th percentile of predicted no effect concentration) to calculate the risk quotients (RQs) for an individual PAH. The equilibrium partitioning method was applied to estimate toxicity data in sediment. A method based on the equivalent concentration concept was proposed and applied to assess the combined ecological risk of multiple PAHs. Monte Carlo simulation and bootstrap technique were utilized to calculate the distribution of RQs and associated uncertainties. The ecological safety level was defined by RQ ≤ 1. Results indicated that both in water and sediment, fluoranthene and pyrene posed the highest risks, whereas acenaphthene and fluorene posed negligible risks. Naphthalene and phenanthrene did not pose risks to the ecological community in surface water but had relatively higher risks in sediment. The median RQs of combined risk in surface water and sediment were 0.934 and 2.42, and the probabilities of RQ > 1 were up to 0.473 and 0.599, respectively, which were much higher than the individual compound acting alone. The risk level in sediment was quite higher than in surface water probably owing to the non-equilibrium distribution between two phases, which suggested that local authorities should focus more on sediment quality management.

Heavy-metal fractionation in surface sediments of the Cauvery River Estuarine Region, Southeastern coast of India

Geochemical fractionation of iron (Fe), manganese (Mn), copper (Cu), chromium (Cr), lead (Pb), zinc (Zn), and nickel (Ni) were determined using five-stage sequential extraction in sediments collected from estuarine stretches of Cauvery River delta on the eastern coast of India with emphasis on seasonal variation. Abundance of metals in terms of sum of total fractionations varied in the following order: Fe > Mn > Cr > Zn > Cu > Ni > Pb. Exchangeable fraction, believed to be bioavailable, showed differential abundances during the dry and wet seasons in the following order: Pb > Zn > Cu > Mn > Ni > Cr > Fe and Zn > Cu > Cr > Ni > Mn > Pb > Fe, respectively, indicating the possibility of anthropogenic influence. Among nonlithogenic fraction, organic matter-bound fraction is the second largest and a key scavenger for all of the heavy metals studied except Fe and Mn. A significant portion of Cu-associated organic matter fraction shows strong association of Cu with organic matter at most of the sampling sites. Environmental risk of metals evaluated using risk-assessment code and mobility factor showed low to high risk for Pb, Zn, and Cu. The results of the present study also hint at notable enrichment of heavy metals in the certain pockets of the Cauvery Estuary.

Dissolution of copper and iron from automotive brake pad wear debris enhances growth and accumulation by the invasive macrophyte Salvinia molesta Mitchell

Automotive vehicles release particulate matter into the environment when their brakes are applied. The environmental effects of this automotive brake pad wear debris (BPWD) on the environment is a matter of growing debate yet the effects on plants have been largely untested. In this study, the effect of BPWD on the growth of the aquatic invasive Salvinia molesta Mitchell was examined. Salvinia molesta, plants were grown hydroponically in distilled water or in a distilled water extract containing BPWD. Growth of floating leaves, submerged leaves, and leaf nodes were measured over 20 d at 4-d intervals. At the conclusion of the study the amount of BPWD present in solutions and plant tissues was quantified using atomic absorption spectrometry (AAS). Cultivation of S. molesta in the water containing BPWD resulted in greater dissolution of Cu and Fe than occurred in the absence of plants. The tissue Cu and Fe concentrations of plants cultivated in the BPWD were significantly higher than plants grown in the absence of BPWD. Growth of S. molesta significantly increased when cultivated in the BPWD solutions in comparison to the distilled water. The results suggest that S. molesta and similar aquatic plants may be capable of increasing the dissolution of metal micronutrients from BPWD and utilizing those micronutrients to increase growth. Such growth responses could indicate that BPWD may interact with invasive floating macrophytes to more rapidly degrade the quality and stability of aquatic communities.

Toxicity reference values and tissue residue criteria for protecting avian wildlife exposed to methylmercury in China

MeHg is the most biologically available and toxic from of mercury, and has the potential to bioaccumulate and biomagnify as it moves up the food chain. These characteristics result in MeHg exposure to avian wildlife at high trophic levels that can produce adverse effects. The toxicity of MeHg to birds was reviewed, and using available data, TRVs and TRCs were derived for protecting birds in China. The TRV and TRC values were based on concentrations of MeHg in diet (or fish tissue based) and tissues of birds. Two methods were applied to derive TRVs from concentrations in the diet or in tissues. These were the CSA and SSD approaches. Results of published studies show that reproductive productivity of while ibis was the most sensitive endpoint for MeHg exposure, and study results on white ibises were used for deriving the TRV and TRC values, which included applying a UF of 2.0. For the SSD approach, data for ten species were used to construct the SSD for MeHg, and to calculate the dietary-based TRV and TRC values. Using the CSA approach, the TRV was based on MeHg in the diet and was derived as 5.0 ng MeHg/g (bm).day; for feathers and blood, the TRV's were 3.16 μg THg/g (wwt), and 0.365 μg THg/g (wwt), respectively. The corresponding TRCs were 15.47 ng MeHg/g (wwt), 3.16 μg THg/g (wwt)respectively. The dietary-based TRV and TRC derived by SSD were 3.09 ng MeHg (bm)/day and 9.56 ng MeHg/g (wwt) respectively. However, birds tissue residue-based criteria were not available because insufficient MeHg effects data existed to construct an SSD for birds. We compared the criteria derived in our study to those developed by others, and concluded that our results provided more reasonable protection to Chinese avian wildlife. By comparing the criteria derived values we calculated to actual MeHg levels in fish and bird tissues, we concluded that these criteria values are useful indicators for screening-level risk assessments of avian wildlife in Chinese aquatic systems. The results of this meta-analysis might therefore have important implications for assessing the risk of Hg exposure to birds and for environmental management in China and in other regions. Moreover, because humans and top avian wildlife consumers are at the same trophic level, these criteria may also be used as a reference for human health risk assessment. The diet of birds consists of aquatic species from different trophic levels. However, the structure of the food web for avian wildlife and the environmental factors that effect their exposure to MeHg vary among aquatic systems. Therefore, further research results are needed on the food web structure of avian wildlife in Chinese aquatic systems to provide more insight into what constitutes adequate protection for avian wildlife.

Characterizing ecological risk for polycyclic aromatic hydrocarbons in water from Lake Taihu, China

Lake Taihu provides vital ecological services for humans in China; it receives a great deal of attention regarding its ecological and environmental conditions. In this study, the ecological risks of eight individual polycyclic aromatic hydrocarbons (PAHs) in water were assessed using probabilistic distributions of the hazard quotient based on Monte Carlo simulation. The results show that the 95th percentile of the hazard quotients ranged from 0.00074 to 2.831, and the ecological risk of Flua was highest, followed by, in descending order of risk, B[a]P > Pyr > Ant > Phe > Flu > Ace > Chr. The probabilities of hazard quotients exceeding a decision criteria of 0.3 were 18.09%, 6.51%, 3.76%, and 2.85% for Flua, B[a]P, Pyr, and Ant, respectively, indicating their potential ecological risks to aquatic organisms. The spatial distribution of hazard quotients for these four individual PAHs with potential ecological risk were obtained using Geographic Information System (GIS), and similar spatial distribution patterns were also observed in the lake. The highest ecological risks of these four individual PAHs to aquatic organisms were found in Meiliang Bay, followed by Gonghu Bay and Xukou Bay. The uncertainty within the ecological risk assessment was also discussed.

Spatial distribution and multiple sources of heavy metals in the water of Chaohu Lake, Anhui, China

In this study, a survey for the spatial distribution of heavy metals in Chaohu Lake of China was conducted. Sixty-two surface water samples were collected from entire lake including three of its main river entrances. This is the first systematic report concerning the content, distribution, and origin of heavy metals (Cu, Cr, Cd, Hg, Zn, and Ni) in the Chaohu Lake water. The results showed that heavy metals (Cu, Cr, Zn, and Ni) concentrations in the estuary of Nanfei River were relatively higher than those in the other areas, while content of Hg is higher in the southeast lake than northwest lake. Moreover, Cd has locally concentration in the surface water from the entire Chaohu Lake. The heavy metal average concentrations, except Hg, were lower than the cutoff values for the first-grade water quality (China Environment Quality Standard) which was set as the highest standard to protect the social nature reserves. The Hg content is between the grades three and four water quality, and other heavy metals contents are higher than background values. The aquatic environment of Chaohu Lake has apparently been contaminated. Both the cluster analysis (CA) and correlation analysis provide information about the origin of heavy metals in the Lake. Our findings indicated that agricultural activities and adjacent plants chimneys may contribute the most to Cd and Hg contamination of Chaohu Lake, respectively.

Risk assessment of polycyclic aromatic hydrocarbons in aquatic ecosystems

A probability risk assessment of anthracene, benzo(a)pyrene, chrysene, fluorene, phenanthrene and pyrene was carried out to examine the ecological risk of these six polycyclic aromatic hydrocarbons (PAHs) in aquatic ecosystems in China. The literature on PAH concentrations in surface water in China was collected to evaluate the environmental exposure concentrations (EEC). The 10th percentile of predicted no observed effect concentration (PNEC(10%)) of PAHs, calculated according to the data from the USEPA AQUIRE database and regulatory reviews, was applied as the toxicity assessment endpoint. The ratio of EEC and PNEC(10%), expressed as a risk quotient (RQ), was used to characterize the risk value. Bootstrapping method and Monte Carlo simulation were utilized to calculate the distribution of EEC, PNEC(10%), RQ and associated uncertainties. Risk assessment showed that reliable maximum RQs of anthracene, benzo(a)pyrene, chrysene, fluorene and phenanthrene were in the range of 0.064-0.755, lower than the acceptable value of 1. However, the reliable maximum RQ of pyrene was 1.39, indicating its potential ecological risk. Notwithstanding the uncertainty, these results suggest that the aquatic ecosystems with high PAH concentrations might pose potential ecological risks, and concerted efforts are required to ensure that surface water is protected.

Bioaccumulation and toxicity of copper in outdoor freshwater microcosms

This study characterizes the effects of copper (Cu) on Florida apple snails (Pomacea paludosa) and mosquito fish (Gambusia affinis) using a replicated outdoor microcosm design. Soils used in this study were collected from two Cu-enriched citrus agricultural sites in South Florida (Agler property (AGLR) in St. Lucie County and Sunrise Boys property (SRB) in Palm Beach County) and a reference site (Equus property) in St. Lucie County. The study included a 5-week aging phase, an 11 month exposure phase, and a 3 month post-treatment (exposure) phase. The aging phase was initiated by flooding agricultural soils with rainwater in 4 m(3) fiberglass microcosm tanks. Introducing juvenile apple snails (≤7 d old) and mosquito fish (2-3 cm) into the microcosm tanks initiated the exposure phase. Survival, growth, and reproduction of apple snails and fish, and Cu uptake in apple snails, fish, and periphyton were determined in this study. Water chemistry (e.g., dissolved Cu concentration, dissolved organic carbon and dissolved oxygen concentrations, pH, hardness, alkalinity, etc.) was measured daily or weekly during the study. Initial soil Cu concentrations in Equus, SRB, and AGLR microcosms were 7, 55, and 99 mg/kg dw, respectively. Dissolved Cu concentrations in Equus, SRB and AGLR microcosms at the beginning of the study were 3, 82, and 43 μg/L, respectively and decreased to low saturation levels of about ≤9 μg/L Cu after the first 3 months of the study. The decrease of dissolved Cu concentrations was likely due to the dilution of rainwater. Snail and fish mortality appeared to be higher in SRB microcosms than in Equus and AGLR microcosms. There was no significant difference in growth of the snails between treatments. Snail growth data followed the von Bertalanffy Model. The maximum shell length, shell height, and shell width of the snails calculated by the von Bertalanffy Model (L(∞)) were 2.76, 2.05, and 2.18 cm, respectively. The maximum wet weight was 9.38 g. Growth rate (k) of the snails increased in order of shell height (0.459), shell length (0.550), and shell weight (0.598). There was no reproduction in the snails in any treatments including the reference during the exposure phase. However, Cu did not affect reproduction of fish during this period. Copper concentrations in periphyton from Equus, SRB, and AGLR microcosms ranged from 2 to 62, 31 to 371, and 13 to 478 mg/kg, respectively. Copper concentrations in fish at the beginning, days 30 and 150 of the study ranged from 3.19 to 7.53 mg/kg and were not significantly different from the different treatments. Average Cu concentrations in the soft tissue of dead snails from SRB and AGLR microcosms were 4602 mg/kg dw (ranged from 2913 to 8370 mg/kg dw) and 2824 mg/kg dw (ranged from 2118 to 3600 mg/kg dw), respectively. The Cu concentrations in the soft tissue of dead snails found in this study were higher than the tissue Cu concentrations in live aquatic organisms reported in the literature. These high Cu concentrations in edible apple snail soft tissue might pose a risk to Florida apple snail predators, including the snail kite. The post-exposure phase, with snails exposed to only water (i.e., no soils) showed depuration of copper from apple snails and reproduction in all treatments.

Effects of sublethal chronic copper exposure on the growth and reproductive success of the Florida apple snail (Pomacea paludosa)

Florida apple snails (Pomacea paludosa) were exposed to three concentrations of copper (Cu), in water (8 microg/L, 16 microg/L, 24 microg/L), for one generation to examine uptake and the effects on survival, growth, and reproduction of the F(0) generation and survival, growth, and whole body Cu of the F(1) generation. During a 9-month Cu exposure, apple snails exposed to 8-16 microg/L Cu had high Cu accumulation (whole body, foot, viscera, and shell) and significantly reduced clutch production (8-16 microg/L) and egg hatching (16 microg/L). Apple snails exposed to the 24 microg/L Cu had low survival and the treatment was therefore terminated. Concentrations of minerals (Na(+), K(+), Mg(2+), Ca(2+)) in tissues were maintained regardless of Cu exposure, but the distribution of Cu in the body of snails differed, depending on exposure concentrations. Higher exposure concentrations resulted in a greater percentage of Cu accumulated in the viscera of the snail. Copper exposure to the F(0) generation did not affect the survival, growth, or whole body Cu concentrations in the F(1) generation. These finding are significant, given the importance of the Florida apple snail in the Everglades food chain. Changes in the abundance of apple snail populations, as a result of Cu exposure, could ultimately affect foraging success of predators.

Copper desorption in flooded agricultural soils and toxicity to the Florida apple snail (Pomacea paludosa): implications in Everglades restoration

Copper (Cu) desorption and toxicity to the Florida apple snail were investigated from soils obtained from agricultural sites acquired under the Comprehensive Everglades Restoration Plan. Copper concentrations in 11 flooded soils ranged from 5 to 234 mg/kg on day 0 and from 6.2 to 204 mg/kg on day 28 (steady-state). The steady-state Cu concentration in overlying water ranged from 9.1 to 308.2 microg/L. In a 28-d growth study, high mortality in snails occurred within 9 to 16 d in two of three soil treatments tested. Growth of apple snails over 28 d was affected by Cu in these two treatments. Tissue Cu concentrations by day 14 were 12-23-fold higher in snails exposed to the three soil treatments compared to controls. The endangered Florida snail kite and its main food source, the Florida apple snail, may be at risk from Cu exposure in these managed agricultural soil-water ecosystems.