Toxicity Identification Evaluation Research Articles

Toxicity and chemical characterization of shale gas wastewater discharged to the receiving water: Evidence from toxicity identification evaluation

Flowback and produced water (FPW) generated from shale gas extraction is a complex mixture consisting of injected drilling fluid, deep formation water, and byproducts of downhole reactions. Limited knowledge is available regarding the impact of discharged FPW on surface water in China. With the development of shale gas exploitation, this emphasizes an urgent need for comprehensive assessments and stringent regulations to ensure the safe disposal of shale gas extraction-related wastewater. Herein, we explored potential impacts of treated shale gas wastewater discharged into a local river in southwest China through toxicity identification evaluation (TIE). Results revealed that organics and particulates significantly contributed to the overall toxicity of the treated FPW wastewater. Through target and suspect chemical analyses, various categories of organic contaminants were detected, including alkanes, aromatic hydrocarbons, biocides, phenols, and phthalates. Furthermore, non-target analysis uncovered the presence of surfactant-related contaminants in tissues of exposed organisms, but their contribution to the observed toxicity was unclear due to the lack of effect data for these compounds. Higher toxicity was found at the discharge point compared with upstream sites; however, the toxicity was rapidly mitigated due to dilution in the receiving river, posing little impact on downstream areas. Our study highlighted the importance of monitoring toxicity and water quality of FPW effluent even though dilution could be a viable approach when the water volume in the discharge was small.

Toxicity identification evaluation for hydraulic fracturing flowback and produced water during shale gas exploitation in China: Evidence from tissue residues and gene expression.

Hydraulic fracturing flowback and produced water (HF-FPW) from shale gas extraction processes is a highly complex medium with potential threats to the environment. Current research on ecological risks of FPW in China is limited, and the link between major components of FPW and their toxicological effects on freshwater organisms is largely unknown. By integrating chemical and biological analyses, toxicity identification evaluation (TIE) was used to reveal causality between toxicity and contaminants, potentially disentangling the complex toxicological nature of FPW. Here, FPW from different shale gas wells, treated FPW effluent, and a leachate from HF sludge were collected from southwest China, and TIE was applied to obtain a comprehensive toxicity evaluation in freshwater organisms. Our results showed that FPW from the same geographic zone could cause significantly different toxicity. Salinity, solid phase particulates, and organic contaminants were identified as the main contributors to the toxicity of FPW. In addition to water chemistry, internal alkanes, PAHs, and HF additives (e.g., biocides and surfactants) were quantified in exposed embryonic fish by target and non-target tissue analyses. The treated FPW failed to mitigate the toxicity associated with organic contaminants. Transcriptomic results illustrated that organic compounds induced toxicity pathways in FPW-exposed embryonic zebrafish. Similar zebrafish gene ontologies were affected between treated and untreated FPW, again confirming that sewage treatment did not effectively remove organic chemicals from FPW. Thus, zebrafish transcriptome analyses revealed organic toxicant-induced adverse outcome pathways and served as evidence for TIE confirmation in complex mixtures under data-poor scenarios.

Critical review of the OSPAR risk-based approach for offshore-produced water discharges.

The management of produced water (PW) discharges from offshore oil and gas installations in the North Atlantic is under the auspices of OSPAR (Oslo/Paris convention for Protection of the Marine Environment of the North-East Atlantic). In 2010, OSPAR introduced the risk-based approach (RBA) for PW management. The RBA includes a hazard assessment estimating PW ecotoxicity using two approaches: whole-effluent toxicity (WET) and substance-based (SB). Set against the framework of the WET and SB approach, we conducted a literature review on the magnitude and cause of PW ecotoxicity, respectively, and on the challenges of estimating these. A large variability in the reported magnitude of PW WET was found, with EC50 or LC50 values ranging from <1% to >100%, and a median of 11% (n = 301). Across the literature, metals, hydrocarbons, and production chemicals were identified as causing ecotoxicity. However, this review reveals how knowledge gaps on PW composition and high sample and species dependency of PW ecotoxicity make clear identification and generalization difficult. It also highlights how limitations regarding the availability and reliability of ecotoxicity data result in large uncertainties in the subsequent risk estimates, which is not adequately reflected in the RBA output (e.g., environmental impact factors). Thus, it is recommended to increase the focus on improving ecotoxicity data quality before further use in the RBA, and that WET should play a more pronounced role in the testing strategy. To increase the reliability of the SB approach, more attention should be paid to the actual composition of PW. Bioassay-directed chemical analysis, combining outcomes of WET and SB in toxicity identification evaluations, may hold the key to identifying drivers of ecotoxicity in PW. Finally, an uncertainty appraisal must be an integrated part of all reporting of risk estimates in the RBA, to avoid mitigation actions based on uncertainties rather than reliable ecotoxicity estimations. Integr Environ Assess Manag 2023;19:1172-1187. © 2022 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Use of Toxicity Identification Evaluation Procedures to Clarify the Relationship Between Ammonium Concentrations and Phytoplankton Blooms in the San Francisco Bay Estuary, California, USA.

Phytoplankton blooms in the northern San Francisco Bay Estuary have historically supported much of the larval fish production in the estuary. In the past, blooms were limited largely by reduced light intensities and net outflows through the system, as well as dense populations of introduced clams that continuously filter the water column. Conversely, the estuary is exposed to a wide variety of contaminants that may also impact phytoplankton growth. Interestingly, previous investigations have suggested that relatively low concentrations of ammonium may inhibit development of bloom conditions by interfering with nitrate assimilation. Given the complex dynamics of the system, with multiple factors that could potentially affect algal growth, additional data to validate this hypothesis are important to identify appropriate management options. Consequently, toxicity identification evaluation (TIE) procedures were applied to ambient water samples and monitored for 72-96 h under controlled conditions to evaluate their effects on algal growth and utilization of dissolved inorganic nitrogen. The TIE treatments specifically targeted ammonium, as well as the potential contributions of metals and nonpolar organic contaminants. Notably, all samples exhibited positive growth over the exposure period with no evidence of toxicity, and TIE treatments did not further improve growth. A subsequent 72-h study evaluated the effect of ammonium up to 12 µM at a fixed concentration of nitrate was monitored at 24-h intervals and showed no inhibition of the development of bloom conditions. Collectively, there was no evidence that ammonium interfered with growth, even at concentrations well above the range of postulated effect levels. Of additional interest, the lack of increased growth in TIE treatments targeting chelatable metals and nonpolar organics suggested that these contaminant classes were not present at inhibitory concentrations. These results demonstrate the importance of validation of cause in multistressor environments, and further clarify the roles of different factors that may limit development of bloom conditions in the estuary. Environ Toxicol Chem 2023;42:178-190. © 2022 SETAC.

Omics-based high throughput toxicity screening and risk assessment of pollutants

<p indent="0mm">Screening priority pollutants with high toxicity and risk potential from a large number of environmental chemical pollutants is the prerequisite for prevention and control of environmental risks. After entering the living system, toxic pollutants can induce adverse outcomes through a series of disturbed molecular targets and biological pathways. Existing high-throughput toxicity screening methods rely on few and isolated cellular or molecular endpoints, making it difficult to capture the key biological processes that cause toxicity and to determine the direct relationship between chemical pollutants and disease. Meanwhile, the awareness is increasing that we are exposed to a true cocktail of chemicals, among which only a fraction has been identified through analytical methods. Integrated bioanalytical approaches, such as effect-directed analysis and toxicity identification evaluation (TIE), have been used to identify risk drivers in complex mixture pollutants. However, it is still difficult to elucidate the molecular toxicological drivers of chemical stress in the environment. Toxicogenomics take advantage of genome-wide coverage, high throughput, and big data capacity that are associated with omics technologies to achieve technology innovation in screening and risk assessment of chemical pollutants. We reviewed the technical advantages and the recent progress of toxicogenomic methodology in high-throughput toxicological screening and risk assessment of chemical pollutants from four aspects with specific research cases. To identify the molecular events initiated by toxic pollutants, toxicogenomics could uncover a large number of molecular events and pathways potentially disturbed at the early development stage of toxicity. Dose-dependent transcriptomes for high-throughput chemical testing have been developed to quantitatively assess responses induced by chemical pollutants at the molecular level, which improve the sensitivity of identifying bioactivity by 1–3 orders of magnitude. To uncover the biological pathways of adverse health outcome by chemical pollutants, systemic toxicological assessment by omics strategies provide mechanistic information for chemical pollution screening and health risk assessment at multiple biological levels. Through biological pathway enrichment analysis, such as the gene ontology (GO) and kyoto encyclopedia of genes and genomes (KEGG) pathway, the molecular mechanistic information of toxicity could be captured. Moreover, multi-omics integration allows for multi-scale, comprehensive biological network analysis, which provide a systematic understanding of toxicity pathways or adverse outcome pathways (AOPs) to guide ecological and human health risk assessments. For human diseases diagnostics, functional genomics provide a new tool to explore mechanisms of individual disease risk and susceptibility under toxic pollutants exposure. Variations of individual susceptibility to toxicant-induced disease are largely due to genetic susceptibility across different populations. The direct relationship among pollutants, genes and adverse outcomes could be established by combining functional genomics and molecular epidemiological approaches. Finally, for risk management of complex mixture pollutants, it is important to assess the overall toxicity effects of the pool of pollutants and identify the key toxic pollutant. The combination of high-throughput bioassays and chemical analysis can be used to identify the highly bioactive fraction and to screen the key chemical pollutant that pose ecological and health risks. Recently, progresses have been made in integrating transcriptomic techniques with molecular toxicity identification and evaluation (mTIE) to assess the overall effects of mixtures and distinguish the key pollutants in inducing the corresponding biological responses. Particularly, dose-response transcriptome could be used to quantitatively evaluate the overall toxic effects and to guide the key toxicant identification by high mechanistic resolution. In summary, the development of omics-based high-throughput toxicity screening technologies will strongly support accurate environmental risk assessment of conventional and new pollutants in the future.

Bioassay-based identification and removal of target and suspect toxicants in municipal wastewater: Impacts of chemical properties and transformation

Municipal wastewater contains numerous chemicals and transformation products with highly diverse physiochemical properties and intrinsic toxicity; thus, it is imperative but challenging to identify major toxicants. Herein, toxicity identification evaluation (TIE) was applied to identify major toxicants in a typical municipal wastewater treatment plant (WWTP). Impacts of chemical properties on the removal of contaminants and toxicity at individual treatment stages were also examined. The WWTP influent caused 100% death of Daphnia magna and zebrafish embryos, and toxicity characterization suggested that organics, metals, and volatiles all contributed to the toxicity. Toxicity identification based on 189 target and approximately one-thousand suspect chemicals showed that toxicity contributions of organic contaminants, metals, and ammonia to D. magna were 77%, 4%, and 19%, respectively. Galaxolide, pyrene, phenanthrene, benzo[a]anthracene, fluoranthene, octinoxate, silver, and ammonia were identified as potential toxicants. Comparatively, the detected transformation products elicited lower toxicity than their respective parent contaminants. In contrast, the analyzed contaminants showed negligible contributions to the toxicity of zebrafish embryos. Removal efficiencies of these toxicants in WWTP were highly related to their hydrophobicity. Diverse transformation and removal efficiencies of contaminants in WWTPs may influence the chemical compositions in effluent and ultimately the risk to aquatic organisms in the receiving waterways.

Acute toxicity of tire wear particles, leachates and toxicity identification evaluation of leachates to the marine copepod, Tigriopus japonicus

Tire wear particles (TWPs) have been characterized as microplastics in recent years, and many of these TWPs will be eventually deposited in coastal areas, leading to adverse effects to marine organisms. Results of the acute toxicity test in this study showed that the 96-h LC50 values of the particles and leachate were 771.4 mg/L (95% CI = 684.4–869.6 mg/L) and 5.34 g/L (95% CI = 4.75–6.07 g/L), respectively. The chemical constituents of TWP and the leachate are very complex, and little research has been conducted to determine which of these constituents contribute to the toxicity of TWP leachate to marine organisms. Therefore, the composition of the TWP and leachate was analyzed, and a variety of chemicals were identified, including metals (Mn, Zn, etc.) and organic compounds (cyclohexanthiol, 4-ethyl-1,2-dimethylbenzene, benzothiazole, stearic acid, N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine, etc.). In addition, the marine copepod Tigriopus japonicus was applied as a model species in the toxicity identification evaluation study to characterize, identify and confirm the toxicity-causing substances in the TWP leachate. Zn was identified and confirmed as the main toxicant contributing to the toxicity. Furthermore, Zn concentrations in the leachate over time were investigated. The release of Zn from TWPs to the aquatic environment was slow, and conformed to a parabolic model with a release constant k of 2.06. The organic component, benzothiazole, exhibited an antagonistic effect with zinc in the acute toxicity of the TWP leachate.

Effect-based water quality assessment of rivers receiving discharges from legacy mines by using acute and chronic bioassays with two cladoceran species

Abstract Information about the ecotoxicological impacts of surface waters that receive discharges from legacy mines is valuable to infer the ecological impacts on natural environment for managing mine discharges. In this study, we investigated behavioural and reproductive responses of two cladoceran species Ceriodaphnia dubia and Daphnia magna to water samples collected from metal-contaminated and reference rivers near legacy mines in Japan. The toxicity identification evaluation (TIE) of water samples that caused D. magna immobility was conducted to evaluate the key metals causing acute toxicity. The results of our water quality assessment performed using two cladoceran species demonstrated modest to significant adverse effects on their behaviour and reproduction, suggesting the potential for ecotoxicological impacts on natural populations and communities at several contaminated sites that received mine drainage. The results of TIE of water samples that caused D. magna immobility indicated likely contributions of Zn and Cu. These results imply that effect-based water quality assessments such as ours can provide direct and unique evidence of the ecotoxicological impacts of metals in river waters, which will be useful for better understanding and predicting the ecological effects of these metals in the natural environment.

Evaluation of Toxicity Effect of Palm Oil Mill Effluent Final Discharge by using Daphnia magna

Palm Oil Mill Effluent (POME) final discharge has a risk to the ecosystem due to various harmful contaminants including organic and inorganic materials. In this study, biological monitoring method was used to evaluate the toxicity effects of POME final discharge using Daphnia magna. The physical and chemical nature of toxicants present in the effluent were characterized through acute Whole Effluent Toxicity (WET), and Toxicity Identification Evaluation (TIE) tests. The Toxicity Unit (TU) and median lethal concentration (LC50) of the POME sample were 11.09 and 9.02% (v/v) respectively. From TIE test, the toxicants present in the effluent can be characterized as filterable and oxidisable through filtration and aeration treatment. The presence of cationic metals, chlorine and disinfection by-products were also determined by the toxicity reduction of the effluent after treatment using ethylenediaminetetraacetic acid (EDTA) and sodium thiosulphate. From TIE test, the filtration treatment at pH 10 of the POME final discharge was the most effective method in reducing the toxicity of the effluent with a value of TU, 1.16 and LC50, 86.34% (v/v). It is recommended that biological tests using Daphnia magna can be made as potential methods to indicate the effects of POME final discharge to the aquatic ecosystem.

Toxicity Identification Evaluation of Sediments from the Xihe River.

In the present study, chinonomus riparius larvae were selected as a model organism, and 11 sediment samples from the Xihe River in Shenyang underwent toxicity identification evaluation (TIE) to identify sediment toxic pollutants. Heavy metals and organic pollutants were the main toxic pollutants through toxicity screening and characterization. The results of toxicity identification showed that the pollution level from Cd was most serious and that phenol and P-methyl phenol were the major organic pollutants. Moreover, a spiking test of Cd was conducted, which indicated that Cd was the main toxic pollutant of sediments at sites 4, 6, 7, 8, and 10. We confirm that TIE is the most effective method to determine the relationship between toxic effects and toxic pollutants. Environ Toxicol Chem 2021;40:3103-3110. © 2021 SETAC.

Chemical and biological tracking in decentralized sanitation systems: The case of artificial constructed wetlands

Given that the social and economic sustainability of rural areas is highly based on the protection of natural resources, biodiversity and human health, simple-operated and cost-effective wastewater treatment systems, like artificial constructed wetlands (CWs), are widely proposed for minimizing the environmental and human impact of both water and soil pollution. Considering that the optimization of wastewater treatment processes is vital for the reduction of effluents toxic potential, there is imperative need to establish appropriate management strategies for ensuring CW performance and operational efficiency. To this end, the present study aimed to assess the operational efficiency of a horizontal free water surface CW (HFWS-CW) located in a world heritage area of Western Greece, via a twelve-month duration Toxicity Identification Evaluation (TIE)-like approach, including both chemical and biological tracking tools. Conventional chemical tracking, by means of pH, conductivity, total COD, and nitrogen-derived components, like nitrates and ammonia–nitrogen, were monthly recorded in both influents and effluents to monitor whether water quality standards are maintained, and to assess potent CW operational deficiencies occurring over time. In parallel, Whole Effluent Toxicity (WET) bioassays were thoroughly applied, using freshwater algae and higher plant species (producers), crustaceans and rotifers (consumers), as well as human lymphocytes (in terms of Cytokinesis Block Micronucleus assay) to evaluate the acute and short-term toxic and hazardous potential of both influents and effluents. The integrated analysis of abiotic (physicochemical parameters) and biotic (toxic endpoints) parameters, as well as the existence of “cause-effect” interrelations among them, revealed that CW operational deficiencies, mainly based on poorly removal rates, could undermine the risk posed by treated sewage. Those findings reinforce the usage of WET testing, thus giving rise to the importance of applying appropriate water management strategies and optimization actions, like oxygen enrichment of surface and bottom of HFWS-CW basins, expansion of the available land, the enhancement of bed depth and seasonal harvesting of plants, for ensuring sewage quality, in favor of water resources protection and sustainable growth in rural areas.

Microscale Toxicity Identification Evaluation (TIE) for interstitial water of estuarine sediments affected by multiple sources of pollution.

Estuaries in the world are affected by different contamination sources related to urbanisation and port/industrial activities. Identifying the substances responsible for the environmental toxicity in estuaries is challenging due to the multitude of stressors, both natural and anthropogenic. The Toxicity Identification and Evaluation (TIE) is a suitable way of determining causes of toxicity of sediments, but it poses difficulties since its application is labour intensive and time consuming. The aim of this study is to evaluate the diagnosis provided by a TIE based on microscale embryotoxicity tests with interstitial water (IW) to identify toxicants in estuarine sediments affected by multiple stressors. TIE showed toxicity due to different combinations of metals, apolar organic compounds, ammonia and sulphides, depending on the contamination source closest to the sampling station. The microscale TIE was able to discern different toxicants on sites subject to different contamination sources. There is good agreement between the results indicated in the TIE and the chemical analyses in whole sediment, although there are some disagreements, either due to the sensitivity of the test used, or due to the particularities of the use of interstitial water to assess the sediment toxicity. The improvement of TIE methods focused on identifying toxicants in multiple-stressed estuarine areas are crucial to discern contamination sources and subsidise management strategies.

After remediation – Using toxicity identification evaluation of sediment contamination in the subtropical Erren river basin

This study utilized the freshwater amphipod (Hyalella azteca) for the indication of contamination risk levels of sediment-associated contaminants in the Erren (ER1∼ER10) and Sanye Rivers (SY1∼SY5) which were contaminated by metal scrap and smelting industries for decades. Toxicity identification evaluations involving the manipulation of pore water and whole-sediment samples were conducted to identify causative pollutants. Impacts on the aquatic environment were then evaluated in order to explore how industrial development led to contaminant accumulation in sediments and resulted in biological effects. A whole-sediment TIE indicated that the major toxicant at sampling sites ER8 and SY5 was ammonia and that its toxicity was significantly reduced by the addition of zeolite. Toxicity at sampling sites ER4 and ER9 was induced by ammonia and heavy metals (Zn, Cd, Cr, As), whereas Cr was at toxic levels at ER6. ∑PAHs was another major class of contaminants at site ER2. Metals (Zn, Ni, Pb, Cd, Cr, and As) were identified as major toxic contaminants at three sites (ER3, SY1, and SY3). The application of TIEs confirmed that a causative toxicant can be identified and that its measured toxicity correlated with its concentration. In conclusion, a TIE approach was successful in demarcating most effective contaminant groups (ammonia, heavy metals, and non-polar organic compounds) in whole-sediment cores, their porewaters and potential toxicities from a highly polluted river after remediation in southern Taiwan to an invertebrate animal model H. azteca.

A Novel In Situ Toxicity Identification Evaluation (iTIE) System for Determining which Chemicals Drive Impairments at Contaminated Sites.

Human-dominated waterways contain thousands of chemicals. Determining which chemical is the most important stressor is important, yet very challenging. The Toxicity Identification Evaluation (TIE) procedure from the US Environmental Protection Agency uses a series of chemical and physical manipulations to fractionate compounds within a matrix and systematically identify potential toxicants through laboratory bioassay testing. Although this may provide useful information, it lacks ecological realism because it is subject to laboratory-related artifacts and is resource intensive. The in situ Toxicity Identification Evaluation (iTIE) technology was developed to improve this approach and has undergone a number of modifications over the past several years. The novel prototype 3 consists of an array of iTIE ambient water fractionation units. Each unit is connected to a peristaltic pumping system with an organism exposure chamber that receives water from a resin chamber to chemically fractionate test site water. Test organisms included freshwater and marine standard toxicity test species. Postfractionation waters are collected for subsequent chemical analyses. Currently, the resins allow for separation of ammonia, metals, and nonpolar organics; the subsequent toxicity responses are compared between treatments and unfractionated, ambient exposures. The iTIE system was deployed to a depth of 3 m and evaluated in streams and marine harbors. Chemical analyses of water and iTIE chemical sorptive resins confirmed chemical groups causing lethal to sublethal responses. The system proved to be as sensitive or more so than the traditional phase 1 TIE test and required almost half of the resources to complete. This iTIE prototype provides a robust technology that improves stressor-causality linkages and thereby supports strong evidence for ecological risk weight-of-evidence assessments. Environ Toxicol Chem 2020;39:1746-1754. © 2020 SETAC.

Application of the cellular oxidation biosensor to Toxicity Identification Evaluations for high-throughput toxicity assessment of river water

Toxicity Identification Evaluation (TIE) is a useful method for the classification and identification of toxicants in a composite environment water sample. However, its extension to a larger sample size has been restrained owing to the limited throughput of toxicity bioassays. Here we reported the development of a high-throughput method of TIE Phase I. This newly developed method was assisted by the fluorescence-based cellular oxidation (CO) biosensor fabricated with roGFP2-expressing bacterial cells in 96-well microplate format. The assessment of four river water samples from Langat river basin by this new method demonstrated that the contaminant composition of the four samples can be classified into two distinct groups. The entire toxicity assay consisted of 2338 tests was completed within 12 h with a fluorescence microplate reader. Concurrently, the sample volume for each assay was reduced to 50 μL, which is 600 to 4700 times lesser to compare with conventional bioassays. These imply that the throughput of the CO biosensor-assisted TIE Phase I is now feasible for constructing a large-scale toxicity monitoring system, which would cover a whole watershed scale.

Investigating the Potential Toxicity of Hydraulic Fracturing Flowback and Produced Water Spills to Aquatic Animals in Freshwater Environments: A North American Perspective.

Unconventional methods of oil and natural gas extraction have been a growing part of North America's energy sector for the past 20-30years. Technologies such as horizontal hydraulic fracturing have facilitated the exploitation of geologic reserves that were previously resistant to standard drilling approaches. However, the environmental risks associated with hydraulic fracturing are relatively understudied. One such hazard is the wastewater by-product of hydraulic fracturing processes: flowback and produced water (FPW). During FPW production, transport, and storage, there are many potential pathways for environmental exposure. In the current review, toxicological hazards associated with FPW surface water contamination events and potential effects on freshwater biota are assessed. This review contains an extensive survey of chemicals commonly associated with FPW samples from shale formations across North America and median 50% lethal concentration values (LC50) of corresponding chemicals for many freshwater organisms. We identify the characteristics of FPW which may have the greatest potential to be drivers of toxicity to freshwater organisms. Notably, components associated with salinity, the organic fraction, and metal species are reviewed. Additionally, we examine the current state of FPW production in North America and identify the most significant obstacles impeding proper risk assessment development when environmental contamination events of this wastewater occur. Findings within this study will serve to catalyze further work on areas currently lacking in FPW research, including expanded whole effluent testing, repeated and chronic FPW exposure studies, and toxicity identification evaluations.

Toxicity identification and evaluation of palm oil mill effluent and its effects on the planktonic crustacean Daphnia magna

Palm oil mill effluent (POME) contains complex and highly biodegradable organic matters so discharging it without appropriate treatment may lead to environmental problems. POME final discharge quality is normally determined based on conventional chemical detection such as by biological oxygen demand (BOD) and chemical oxygen demand (COD). The novelty of the present study is that the toxicity effects of the POME final discharge samples were evaluated based on whole effluent toxicity (WET) and toxicity identification evaluation (TIE) tests using Daphnia magna. The toxicity unit (TU) values were recorded to be in the range from TU = 1.1–11 obtained from WET, and the TIE manipulation tests suggested that a substantial amount of toxic compounds was contained in the POME final discharge. Phenol, 2,6-bis (1,1-dimethylethyl)- and heavy metals such as Cu and Zn were detected in all the effluents and were recognized as being the main toxicants in the POME final discharge. GC/MS analyses also successfully identified cyclic volatile methyl siloxanes; cyclotetrasiloxane, octamethyl- (D4), cyclopentasiloxane, decamethyl- (D5), cyclohexasiloxane, dodecamethyl- (D6). D4 was detected at 0.0148–0.0357 mg/L, which could be potentially toxic. The palm oil industry used only water in the form of steam to process the fruits, and the presence of these compounds might be derived from the detergents and grease used in palm oil mill cleaning and maintenance operations. An appropriate treatment process is thus required to eliminate these toxicants from the POME final discharge. It is recommended that two approaches, chemical-based monitoring as well as biological toxicity-based monitoring, should be utilized for achieving an acceptable quality of POME final discharge in the future.

Characterization of Miscellaneous Effluent Discharges from a Mobile Offshore Drilling Unit to the Marine Environment.

A study was performed to evaluate the potential biological impacts from 8 different miscellaneous discharges from an oil and gas mobile offshore drilling unit (MODU) including deck drainage, desalination unit waste, boiler blowdown, fire control system test water, noncontact cooling water, and bilge water. Samples were evaluated for toxicity using a rapid (<1 h) initial screening test (echinoderm [Dendraster excentricus] fertilization test), and if toxicity was found, further testing was conducted using 3 chronic whole-effluent toxicity tests. This additional testing included the embryo larval development 72-h echinoderm (D. excentricus); 7-d mysid (Americamysis bahia) survival, growth, and fecundity invertebrate test; and 7-d topsmelt (Atherinops affinis) survival and growth fish test. Toxicity identification evaluations were performed on 3 discharges that consistently elicited a toxic response during whole-effluent toxicity testing. To place the results of the toxicity testing into the context of environmental risk, the spatial extent of potential biological effects was investigated using the CORMIX mixing zone model. The output of the modeling indicated that discharge of selected effluents did not result in concentrations, or duration of exposure, that would elicit toxic effects to organisms living in the surrounding environment. The present study provides a comprehensive data set that was used to characterize potential toxicity and environmental risk of MODU "miscellaneous discharges" which could help inform future risk assessments of these discharges. Environ Toxicol Chem 2019;38:2811-2823. © 2019 SETAC.

Ecological risk assessment of combined pollution in watersheds

Water pollution in China is severe and combined pollution with multiple stressors poses a great challenge to watershed risk management. Under the conditions of combined pollution, recognizing high-risk areas of concern, identifying key toxicants from multiple stressors and comprehensively assessing their ecological risk are the urgent and difficult tasks in watershed management. Traditional ecological risk assessment mainly focuses on single pollutant, which is difficult to obtain holistic information on the risk related to combined pollution. Based on the current research progress of combined pollution assessment, this review proposes a framework for ecological risk assessment of combined pollution in watersheds, including recognition of high-risk areas, identification of key toxicants and comprehensive assessment of ecological risk of the key toxicants. Firstly, high-risk areas are identified by weight of evidence analysis, which integrates information from both laboratory and in situ exposure and effect analyses. Most of exposure and effect data so far are based on chemical analyses and bioassays in the laboratories, yet bias may exist in extrapolating information from laboratory data to the field. Alternatively, in situ analysis serves an effective approach in reducing this extrapolation bias and, at the same time, more realistically recording biological effects under some field exposure scenarios, such as pulse exposure. Passive sampling devices have been applied for in situ exposure assessment. The integration of passive sampling with in situ organism exposure chambers successfully gains both chemical and toxicological lines of evidence for ecological risk assessment. Secondly, key toxicants in the high-risk areas are identified using toxicity identification evaluation (TIE) and effect-directed analysis (EDA) techniques. Conventional TIE is of environmental relevance by using whole organism bioassays; however, it is lack of effective methods in identifying major contributors to the toxicity because it merely focuses on analyzing the contaminants in target lists. Alternatively, EDA is a powerful tool in identifying key organic toxicants with a combination of chemical fractionation and analysis of targeted and non-targeted contaminants. Nevertheless, the common use of in vitro bioassays and exhaustive extraction make EDA lack of environmental relevance. Therefore, integrating TIE and EDA would provide an environmentally relevant method to effectively determine causality of sediment toxicity by combining the merits of the two methodologies. To improve the accuracy of toxicity identification, bioavailable extraction and dosing techniques are recommended to be incorporated into the integrated method. Thirdly, probabilistic ecological risk of the key toxicants in the high-risk areas is evaluated using tiered ecological risk assessment methods. Hazard quotient method has been widely used in providing conservative risk screening information, but uncertainties could not be quantified with this method. Therefore, a probabilistic assessment method, including distributions of exposure, response and hazard quotient levels, is proposed to achieve a holistic ecological risk assessment. At the end, recent developments and challenges in ecological risk assessment of combined pollution in watersheds are prospected. Overall, integrating the understanding of joint toxicity mechanisms in combined pollution risk assessment, improving the ability in non-targeted analysis and developing bioavailability-based sediment thresholds are important to assess ecological risk of combined pollution in watersheds.

Integrating multiple lines of evidence of sediment quality in a tropical bay (Guanabara Bay, Brazil)

The present study evaluated the ecological risk of metal contamination in sediments of Guanabara Bay (GB) by combining multiple lines of evidence (LOEs). Chemical analysis and a set of whole-sediment toxicity assays were conducted with Tiburonella viscana, Kalliapseudes schubartii, Anomalocardia flexuosa, and Nitocra sp. Results were integrated by multivariate analysis and qualitative methods. Additionally, a whole-sediment Toxicity Identification Evaluation technique (TIE) was applied to identify the chemical groups responsible for the effects. Sediments from harbor and industrial areas exhibited toxicity linked to moderate to high concentrations of Zn, Pb, Cu and Cr. The TIE technique confirmed such effects, but it also indicates the contribution of ammonia and organic compounds to the observed toxicity. Our results demonstrate that the combination of multiple LOEs improves the effectiveness of environmental risk assessment of chemical stressors and management of coastal ecosystems in tropical regions.