Aquatic Receptors Research Articles

Comparative Overview of Different Physical-Chemical Treatments Applied for Real Textile Effluents

The paper presents different physical-chemical treatment applications for textile effluents (i.e. one-single or mixed treatment stages as coagulation-flocculation, homogenous advanced oxidation with hydrogen peroxide as Fenton-like processes, sorption applied for different textile wastewaters followed by sedimentation and/or filtration). The efficiencies of textile wastewater treatments in terms of effluent quality, treatment degree, and optimal operating parameters (i.e. pH, concentration of chemical reagents and materials used, temperature, operating regime, and time) are discussed, together with some restrictions and recommendations. These data concerning different effluent treatments are useful to the environmental management staff but also to all employees that adopted an environmental attitude (EA) in all them behaviour. The concern of solving inside environmental problems (mainly focused on quality of final effluent discharge in aquatic receptor and/or treated effluent recycling), and acting into an ethical, legal and viable manner is necessary and obligatory in the present condition of fresh water deficit, pollution increasing of natural surface water resources, and its variety and/or complexity.

Ecological Risks Associated with Oyster Restoration Options for Chesapeake Bay

ABSTRACT Ecological risk assessments were conducted as part of the Programmatic Environmental Impact Statement designed to evaluate costs and benefits of alternative approaches to oyster restoration in Chesapeake Bay, USA, including the intentional introduction of a non-native Asian oyster species. A relative risk model was used to evaluate alternatives involving both the native Eastern oyster and the non-native species. Effects of options were examined for a diverse set of ecological resources and conditions for the Bay including oysters, submerged aquatic vegetation, phytoplankton, zooplankton, benthic invertebrates, blue crabs, fish, wildlife receptors, dissolved oxygen, and total suspended solids. A weight-of-evidence method based on available scientific evidence was also used to answer a set of questions developed by a science advisory panel. There was low risk that the Asian oyster would not provide ecosystem services similar to those afforded by the Eastern oyster; however, there is moderate to high risk that the Asian oyster would interact with and compete with the Eastern oyster. The potential for introduction and spread of diseases from the Asian oyster to other species in the Bay is considered negligible, but there is high risk that the Asian oyster would disperse outside of the Bay.

Influence diagrams as decision‐making tools for pesticide risk management

The pesticide policy arena is filled with discussion of probabilistic approaches to assess ecological risk, however, similar discussions about implementing formal probabilistic methods in pesticide risk decision making are less common. An influence diagram approach is proposed for ecological risk-based decisions about pesticide usage. Aside from technical data, pesticide risk management relies on diverse sources, such as stakeholder opinions, to make decisions about what, how, where, and when to spray. Bayesian influence diagrams allow multiple lines of evidence, including process related information from existing data and expert judgment, in 1 inclusive decision model. In ecological risk assessments, data informally incorporated for pesticide usage decisions, such as field and laboratory effect studies along with chemical monitoring and modeling data, can be formally incorporated and expressed in linked causal diagrams. A case study is presented from the perspective of an environmental manager wishing to efficiently control pests while minimizing risk to local aquatic receptors. Exposure modeling results and toxicity studies were incorporated, and an ecological risk assessment was carried out but combined with hypothetical information on spraying efficacy and valuation of outcomes that would be necessary for making risk management decisions. The variables and their links in the influence diagram are ones that are important to a manager and can be manipulated to optimally control pests while protecting nontarget resources.

Using Legacy Data to Relate Biological Condition to Cumulative Aquatic Toxicity in the Willamette River Basin (Oregon, USA)

In the Willamette River Basin (Oregon, USA), various residential, municipal, industrial, and agricultural activities produce physical, biological, and chemical stressors that may impinge on the basin's aquatic ecosystems. For > 30 years, numerous water-quality and biological-condition data have been accumulated by often disparate monitoring programs. This diagnostic analysis explored whether these legacy data could be used to correlate the presence of chemical stressors with biological condition impacts with the understanding that association is not necessarily causation. Other natural or anthropogenic stressors that may also impact biological conditions were not considered in this study. Acute-toxicity indices were calculated separately for trace metals and organic chemicals detected in surface waters between 1994 and 2010 and then compared with land-use metrics and vertebrate- and invertebrate-assemblage indices from surveys conducted basin-wide during this same period. Half of the possible relations between land use, biological condition, and toxicity were statistically significant at p ≤ 0.10. These results suggest that conditions for aquatic receptors improve either as agricultural or urban land decreases or as forested land increases and that chemical mixtures (primarily involving pesticides) may have impacted components of the basin's aquatic ecosystems. There may be a need for strengthened chemical-management practices on agricultural and urban lands and for maintaining undisturbed forested land to limit chemical migration into adjacent waters. Although these results indicate some utility for legacy data, they also suggest that a more defensible assessment of chemical stressors requires a program specifically designed for that purpose.

Pollution impact of cement production on air, soil and water in a production location in Nigeria

Environmental pollution caused by the activities of Ewekoro Cement production facility of the West African Portland Cement (WAPC, Plc), Ogun State, Nigeria was studied at some terrestrial and aquatic receptor locations within the catchments area of the production plant which hasbeen in operation for over 40years. Air, water and soil samples of the adjoining villages (Ajobiewe, Olapeleke, Alaguntan and Wasinmi) were analyzed. High particulate matter depositions were recorded for all the sampling locations. Dusts emitted from the cement factory wererich in heavy metals. Heavy metals concentration at Ajobiewe, Olapeleke and Alaguntan were significantly (pNi>Fe>Cr>Zn>Cu>Co>Pb>Cd. Heavy metals concentrations were significantly different (p

An updated weight of evidence approach to the aquatic hazard assessment of Bisphenol A and the derivation a new predicted no effect concentration (Pnec) using a non-parametric methodology

An aquatic hazard assessment establishes a derived predicted no effect concentration (PNEC) below which it is assumed that aquatic organisms will not suffer adverse effects from exposure to a chemical. An aquatic hazard assessment of the endocrine disruptor Bisphenol A [BPA; 2, 2-bis (4-hydroxyphenyl) propane] was conducted using a weight of evidence approach, using the ecotoxicological endpoints of survival, growth and development and reproduction. New evidence has emerged that suggests that the aquatic system may not be sufficiently protected from adverse effects of BPA exposure at the current PNEC value of 100 μg/L. It is with this background that; 1) An aquatic hazard assessment for BPA using a weight of evidence approach, was conducted, 2) A PNEC value was derived using a non parametric hazardous concentration for 5% of the specie (HC 5) approach and, 3) The derived BPA hazard assessment values were compared to aquatic environmental concentrations for BPA to determine, sufficient protectiveness from BPA exposure for aquatic species. A total of 61 studies yielded 94 no observed effect concentration (NOEC) and a toxicity dataset, which suggests that the aquatic effects of mortality, growth and development and reproduction are most likely to occur between the concentrations of 0.0483 μg/L and 2280 μg/L. This finding is within the range for aquatic adverse estrogenic effects reported in the literature. A PNEC of 0.06 μg/L was calculated. The 95% confidence interval was found to be (0.02, 3.40) μg/L. Thus, using the weight of evidence approach based on repeated measurements of these endpoints, the results indicate that currently observed BPA concentrations in surface waters exceed this newly derived PNEC value of 0.06 μg/L. This indicates that some aquatic receptors may be at risk for adverse effects on survival, growth and development and reproduction from BPA exposure at environmentally relevant concentrations.

Meeting the challenge of identifying persistent pollutants at the state level

In 2007, the State of Oregon enacted legislation aimed at identifying persistent pollutants that could pose a threat to waters of the State and then reducing their discharge by means of a comprehensive pollution prevention program. This legislation defined a persistent pollutant as one that is toxic and persistent or bioaccumulative; a broad definition that required evaluation of an extensive number and variety of chemicals. The Oregon Department of Environmental Quality, in consultation with a science workgroup, implemented a 12-step process for identifying and prioritizing persistent pollutants consistent with this definition. This process is characterized by (a) maximum overall transparency in its conduct, including extensive public involvement, (b) 3 levels of objective and predefined criteria for categorization of a chemical as a persistent pollutant, (c) full disclosure of values and sources for all physicochemical data used for comparison with these criteria, and (d) clear acknowledgement when a chemical was identified as a persistent pollutant for reasons other than these criteria alone. This process was used to identify those chemicals relevant as persistent pollutants and to then prioritize them in terms of their relative ability to adversely impact waters of the state, with special emphasis on impacts to aquatic receptors. An initial list of 2130 chemicals was compiled from existing lists. Criteria for toxicity, persistence, and bioaccumulative potential were defined and then used with 2 different chemical property evaluation models (PBT Profiler and EPISuite) to produce a final list of 118 chemicals. The final list includes several legacy pollutants but also contains numerous current-use pharmaceuticals, personal care products, and pesticides, approximately half of which appear only once or not at all on lists compiled by others. Although it drew from the experience of others, assembling this list proved to be an exemplar of science in the service of policy.

Acclimation to ultraviolet irradiation affects UV-B sensitivity of Daphnia magna to several environmental toxicants

Phototoxicity of several environmental contaminants by UV light has been reported in many studies. Nevertheless, field observations suggest the presence of certain defense mechanisms that would protect aquatic organisms against phototoxic damages. The current study was conducted to understand the responses of aquatic receptors to phototoxic chemicals in a natural environment where low dose UV light is present and long-term acclimation to UV might have been taken place. For this purpose, the water flea Daphnia magna was acclimated to a non-lethal, environmentally relevant level of UV-B light for >20 successive generations. The differences in toxicity response were evaluated between the UV-B acclimated and the non-acclimated daphnids when they were exposed to phototoxic compounds such as polynuclear aromatic hydrocarbons (fluoranthene and pyrene), a pharmaceutical (sulfathiazole), or metals (Cd and Cu) under UV-B light. Following the UV-B acclimation, toxicity of metals under UV-B light significantly decreased ( P < 0.1) suggesting the defense/repair system which might be developed through acclimation. For PAHs and sulfathiazole, however the acclimation rendered organisms more susceptible ( P < 0.05). The metabolic cost incurred during the acclimation to UV-B stress may in part explain the organisms’ reduced capacity to deal with other stressors. Addition of vitamin C significantly increased the resistance of UV-B acclimated individuals against Cu, while no change was observed for the other chemicals, suggesting that the mode of Cu phototoxicity is different from those of the other phototoxicants under UV-B light. Two-dimensional gel electrophoresis analyses showed that long-term acclimation to UV-B lead to notable changes in protein expression, which may be further evaluated to explain varying susceptibilities of the acclimated daphnids to different phototoxicants.

Wildlife toxicology: biomarkers of genotoxic exposures at a hazardous waste site

A large number of hazardous waste sites in the United States have undergone the initial stages of remediation or containment. At many of the remaining sites, the potential for exposure to ecological receptors is a primary concern. This manuscript reports on studies to investigate the impact on ecological receptors exposed to complex mixtures at a former creosote facility. Currently there are isolated areas on-site that were not addressed in the initial removal action that appear to be releasing polycyclic aromatic hydrocarbons (PAHs) to the surrounding environment. The U.S. EPA collected environmental samples and performed ex situ sediment bioassays to measure chronic toxicity; whereas, this study describes an in situ study to measure biomarkers of effect in two ecological receptors. Mosquitofish (Gambusia affinis) and cricket frogs (Acris crepitans) were collected from a small intermittent creek adjacent to the site, and reference stations. A weight-of-evidence ecological risk assessment was completed for the amphibian and fish communities. The ecological risk assessment was developed using analysis of media chemistry, body burden of specific PAHs, bioassay results, community surveys, and cellular genome size variation as a biomarker of genotoxicity. Flow cytometric estimates of chromosomal damage were significantly elevated for both mosquitofish and cricket frogs inhabiting the contaminated site, relative to at least one reference site. Surface water screening values for fish and amphibians exceeded screening values for PAHs by more than one order of magnitude in the on-site creek, and sediment PAH concentrations were extremely high (up to 1,549 microg/dry g). Tissue concentrations of PAHs were below screening values. Media chemistry, bioassay and genotoxicity data all support the same conclusion that on-site PAHs continue to impact aquatic receptors. The genotoxicity findings are consistent with and contribute to results of the weight-of-evidence ecological risk assessment. The results support continuing efforts to incorporate biomarkers as valuable lines of evidence within ecological risk assessment.

Effects of cement flue dusts from a Nigerian cement plant on air, water and planktonic quality

Effects of cement flue dust from Ewekoro cement Kilns were monitored at some aquatic receptor locations. High levels of total suspended particulates (TSPs) and atmospheric deposition rates (ADRs) were recorded within the factory compared to ancillary locations outside the factory. The TSP and ADR levels which were location dependent were significantly higher (P < 0.05) during the dry periods than in the wet season. Irrespective of seasonal variations, the key elements in the emissions were Ca(2+) and Fe(2+). The concentrations of Zn(2+), Mn(2+) and Pb(+) which were trace elements were significantly higher (P < 0.05) in the deposited than in the airborne particulates. The planktonic flora and fauna of the river systems draining the area were poor with 16 phytoplanktonic and nine zooplanktonic species. Numerically, the phytoplanktons were dominated by diatoms (Bacillariophyta) with Synedra sp. being the most abundant species. The zooplanktonic fauna dominated by rotifers had Lecane curvicornis as a regular occurrence in all the three catchment rivers. The physicochemical parameters assayed were significantly higher (P < 0.05) in the factory effluent discharges than in water samples from each of the catchment rivers. Seasonal variations inclusive, HCO(-)(3), CO(2-)(3), Ca(2+) and Mg(2+) constituted the major ionic component of water samples analysed irrespective of location. Alaguntan River which receives effluents directly from the factory had significantly higher levels (P < 0.05) of the assayed ions than the other two rivers draining the cement factory catchment areas.

THE ECOLOGICAL EFFECTS OF NANOMATERIALS: A FOCUS ON AQUATIC LIFE

This paper provides an overview of current knowledge regarding the aquatic effects of nanomaterials. Aquatic receptors can potentially be exposed to nanoparticles through ingestion, movement across gills, passive transport, and cellular absorption. Our review indicates that the toxicological research on nanomaterials is still relatively narrow. The present research has been targeted primarily at understanding potential effects to humans, and relatively few ecotoxicity studies have been conducted; however, new research is evolving rapidly. The studies that are currently available focus on metal oxide particles, carbon nanotubes, and fullerenes. Aquatic tests have examined the uptake of these nanoparticles by fish and filter feeders, and have provided evidence of toxicity or behavioral changes. Some of these studies conclude that nanoparticles can be taken up by or produce effects in biota, and that dose-response relationships and patterns of relative toxicity among types of particles are emerging. Caution should be used in designing and interpreting studies on nanoparticles, because factors such as the particle medium preparation method, the presence of other chemicals, and particle behavior such as agglomeration can influence exposure and aquatic toxicity. Ultimately, the objectives of this review are to expand our knowledge of the effects of nanomaterials on ecological processes and aquatic receptor populations, as well as help guide future research.

Determination of metals by total reflection X-ray fluorescence and evaluation of toxicity of a river impacted by coal mining in the south of Brazil

Metal (Fe, Mn, Zn, Ni, Cd, and Pb) concentrations in the region of Criciuma (Brazil), a region impacted by coal mining, were determined in water and sediments using total reflection X-ray fluorescence (TXRF) spectroscopy. Samples were collected from the Mãe Luzia River (south Brazil) at five different stations, from the source down to the river mouth (Ararangua estuary). Water and sediment toxicity were also evaluated using bioassays with Daphnia magna as the bioindicator. The metal present in the highest concentrations both in water (1.3–11 mg L −1) and in sediments (34–142 mg L −1) was iron. Results suggest an influence of coal mining on the aquatic receptors, showing a clear relationship between metal content (mostly Fe) and ecotoxicity.

English

In 2004, the Environmental Protection Agency released a Record of Decision for the remediation of one of the nation's largest Superfund sites - the upper Clark Fork River in western Montana. Fluvially deposited hard rock mine, mill, and smelter wastes from the Butte/Anaconda industrial complex have contaminated the river's floodplain. These acid metalliferous materials vary in depth from a few centimeters to at least one meter. Phytotoxic conditions limit agricultural production, barren river banks are unstable, and the amount of Cu released to the river results in both acute and chronic impacts to aquatic receptors. As stipulated in the Record of Decision, exposed tailings are to be removed, backfilled with appropriate quality cover soil, and revegetated. Streambanks will be stabilized by soft engineering - vegetation fabric, willows, logs, and root wads. Areas of impacted soils and vegetation will be treated in place, using careful addition of lime and other amendments, soil mixing, and revegetation. The Record of Decision also specified all land within the site be classified so impacted areas requiring remediation could be identified. Such a classification system, called the Riparian Evaluation System (RipES) uses key indicators of landscape stability and plant community dysfunction to categorize delineated portions of the site as unique polygons. Each polygon is associated with exact location, surface area, waste volume, and other attributes displayed as geographic information system layers over base area photographs. During the 2006/2007 field seasons, the first 80 km of floodplain were classified into one of four major types: (1) streambank length classified by stability type, (2) exposed tailings, (3) impacted soils and vegetation areas, or (4) slightly impacted soils and vegetation areas. For each of these polygons, a RipES score was derived to determine the most appropriate cleanup remedy specified by the record of decision. In this paper, the RipES system will be described and examples of remedial polygons will exhibited. This pre-remedial design approach is applicable to other large metal-contaminated watershed sites.

Comparison of a score‐based approach with risk‐based ranking of in‐use agricultural pesticides in canada to aquatic receptors

AbstractThe purpose of this paper is to present a new risk‐based approach developed by Environment Canada for ranking pesticides and their potential risk to aquatic life. These rankings are compared to those generated using a more traditional score‐based approach. Two hundred and twelve active ingredients registered in Canada for use in agricultural field crops were included in this assessment. For each major aquatic taxon assessed (fish, insects, crustaceans, algae, and macrophytes), risk was calculated by dividing the 96‐h estimated environmental concentration (modeled using parameters such as the application rate and method as well as physicochemical properties) by HC5 values (obtained through calculations of species sensitivity distribution — based toxicity endpoints). The traditional approach assigned scores based on toxicity endpoints in standard test species as well as physicochemical properties associated with the potential for aquatic contamination. A number of similarities were observed between the rankings but also notable differences. Only 22 active ingredients were common to the top 50 ranking positions from both approaches. The main reasons that accounted for the discrepancies between both rankings were the choice of toxicity endpoints, whether based on single or multiple species; the taxonomic breadth of retained data; the use of scores versus risk quotients; and the choices made in situations where multiple data points were available. We conclude that a risk‐based approach that considers a broad representation of species toxicity data and estimates of runoff and drift concentration in receiving aquatic systems (even from generic application scenarios) is a more realistic representation of potential toxicological effects and a superior method of ranking products for the risk they pose to the aquatic environment.

In situ biomonitoring of PAH-contaminated sediments using juvenile coho salmon ( Oncorhynchus kisutch)

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous marine and freshwater sediment contaminants. Extensive data exist to confirm that PAHs are toxic to aquatic receptors. However, limited information is available regarding the bioavailability and genotoxicity of sediment PAHs to aquatic organisms. This study investigated an integrated biomonitoring approach using chemical analyses and biomarkers to characterize the bioavailability and genotoxicity of a complex PAH mixture in freshwater lake sediments associated with a former manufactured gas plant (MGP). Sediment PAH genotoxicity was assessed by flow cytometry (FCM), DNA adduct 32P-postlabeling, and erythrocyte micronuclei in juvenile coho salmon ( Oncorhynchus kisutch) caged in the water column. Significant PAH-induced genotoxicity was observed with FCM and 32P-postlabeling, but not with erythrocyte micronuclei. Chromosome damage in peripheral blood and hepatic DNA adducts correlated with sediment, but not water column PAH concentrations. Total hepatic DNA adducts in salmon caged nearest the former MGP facility was 39±6.5 (RAL×10 9), while salmon caged in a reference lake had 28±2.3 total hepatic DNA adducts per 10 9 nucleotides. These results indicate that in situ biomonitoring using biomarkers and caged fish can be a sensitive indicator of genotoxic PAHs in sediments.

Comparison of a Score-Based Approach with Risk-Based Ranking of In-Use Agricultural Pesticides in Canada to Aquatic Receptors

The purpose of this paper is to present a new risk-based approach developed by Environment Canada for ranking pesticides and their potential risk to aquatic life. These rankings are compared to those generated using a more traditional score-based approach. Two hundred and twelve active ingredients registered in Canada for use in agricultural field crops were included in this assessment. For each major aquatic taxon assessed (fish, insects, crustaceans, algae, and macrophytes), risk was calculated by dividing the 96-h estimated environmental concentration (modeled using parameters such as the application rate and method as well as physicochemical properties) by HC5 values (obtained through calculations of species sensitivity distribution-based toxicity endpoints). The traditional approach assigned scores based on toxicity endpoints in standard test species as well as physicochemical properties associated with the potential for aquatic contamination. A number of similarities were observed between the rankings but also notable differences. Only 22 active ingredients were common to the top 50 ranking positions from both approaches. The main reasons that accounted for the discrepancies between both rankings were the choice of toxicity endpoints, whether based on single or multiple species; the taxonomic breadth of retained data; the use of scores versus risk quotients; and the choices made in situations where multiple data points were available. We conclude that a risk-based approach that considers a broad representation of species toxicity data and estimates of runoff and drift concentration in receiving aquatic systems (even from generic application scenarios) is a more realistic representation of potential toxicological effects and a superior method of ranking products for the risk they pose to the aquatic environment.

Direct Spectrophotometric Analysis of Cr(VI) Using a Liquid Waveguide Capillary Cell

Hexavalent chromium Cr(VI) is a notorious ground water contaminant toxic to humans and animals. Assessment of an exposure risk for aquatic receptors necessitates frequent Cr(VI) concentration data from a range of surface and groundwater locations at Cr(VI) contamination sites. In this work, we demonstrate that enhanced ultraviolet-visible (UV-vis) spectroscopy using a liquid waveguide capillary cell (LWCC) offers an easy-to-use and economical methodology for the determination of chromate anion CrO(4)(2-) in Hanford natural waters without chemical pretreatment and generation of hazardous waste. Direct determination of CrO(4)(2-) in actual surface and ground water samples with the complexities of competing ions, dissolved organics, and other potential interfering agents was achieved by measuring the chromate optical absorbance at 372 nm. For a 100 cm path length LWCC, the detection limit for chromate was found to be as low as 0.073 ppb. A quantitative relationship between the intensity of the absorbance signal and water pH allowed for the straightforward calculation of total Cr(VI) content in natural water. The described method is applicable for in-field monitoring of Cr(VI) in environmental water samples at trace levels.

Membrane processing for olive mill wastewater fractionation

The possibility of complete fractionation of olive mill wastewater (OMW) was investigated using membrane technology. Combinations of different membrane processes were used for the fractionation of OMW into by-products that may be further developed to achieve reduction of the expenses involved. Ultrafiltration (UF) in combination with nanofiltration (NF) and/or reverse osmosis (RO) were found to be very efficient for the treatment and fractionation OMW. An extended parametric study for the optimum fractionation yield of OMW involved variation of the operational system parameters including temperature, and the trans-membrane pressure. The final effluent obtained was a clean transparent with very low content of organic compounds and dissolved ionic salts. The chemical composition of the post-treatment effluent showed that it was suitable for disposal in aquatic receptors or for use for irrigation purposes. The ultrafiltration process resulted in the separation of high molecular weight constituents including suspended solid particles. Phenols present in the OMW were removed to an extent exceeding 95% of the initial value following the nanofiltration step. The concentrate obtained at this stage was very rich in phenols. Better efficiency of the OMW treatment was achieved applying RO after UF.

담수 물벼룩 Daphnia magna의 자외선 B 적응이 자외선과 중금속의 동시노출에 따른 독성반응에 미치는 영향

Many environmental contaminants including several metals, polycyclic aromatic hydrocarbons, and pharmaceuticals, have been identified to be phototoxic in the water environment. Concerns regarding photo-enhancement of toxicity of several environmental contaminants have been increasing because of the increased level of ultraviolet irradiation on the earth surface. However, there exist arguments that there might be certain defense mechanisms taking place in the aquatic ecosystem, which may include behavioral characteristics or genetic acclimation. This study was conducted to understand the potential responses of aquatic receptors to several phototoxic metals in the real environment, where long-term acclimation of such organisms to low dose UV-B may take place. For this purpose, water flea Daphnia magna was acclimated to environmentally relevant dose of UV-B (12 to <TEX>$18uW/cm^2$</TEX>) for >11 generations. The differences in developmental and life history characteristics, and toxicity responses were evaluated. Acclimation did not affect the daphnids' growth, longevity, and reproduction characteristics such as time to first brood, and brood size: After 21 d, survival of D. magna was not influenced by UV-B acclimation. When the number of young per female was compared. the daphnids acclimated for 11 generations tend to produce less number of neonates than the un-acclimated individuals but with no statistical significance (p>0.05). Four metals that were reported to be phototoxic elsewhere were employed in this evaluation, that include As, Cd. Cu, and Ni. UV-B level being applied in acclimation did increase the toxicity of Cd and Cu, significantly (p<0.05). However, the toxicities of As and Ni were not affected by irradiation of UV-B. Phototoxic responses were evaluated between the acclimated and the un-acclimated daphnids. For Cu, UV-B acclimation led to reduction of the photo-induced toxicity <TEX>$(p\approx0.1)$</TEX> in daphnids. Non-acclimated Daphnia were affected by 50% at 4.18 ug/l Cu. but UV-B acclimated individuals exhibited <TEX>$EC_{50}$</TEX> of 5.89 ug/l. With Cd, UV-B acclimation appeared to increase phototoxicity (p>0.05). With As and Ni, UV-B acclimation did not influence photo-induced toxicity. This observation may be in part explained by the type of reactive oxygen species that were generated by each metal. Similar to UV-B light, Cu is known to generate superoxide anion by acting as redox cycling toxicant. This is one of the first studies that employed_laboratory based UV-B acclimated test species for photoenhanced toxicity evaluation.

Accumulation of hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine in channel catfish (ictalurus punctatus) and aquatic oligochaetes (lumbriculus variegatus)

The extensively used military explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) has been widely released to the environment during production, usage, and disposal operations. Toxic effects of RDX have been reported in terrestrial and aquatic receptors, but investigations regarding the bioaccumulation potential of RDX in aquatic systems are scarce. The objective of the present study was to describe the toxicokinetics of RDX during aqueous exposure for the channel catfish (Ictalurus punctatus) and aquatic oligochaetes (Lumbriculus variegatus) and to compare the amount of RDX accumulation in juvenile catfish following aqueous exposure only, dietary exposure only, and a combination of dietary and aqueous exposure. The toxicokinetics measurements included bioconcentration factors (BCFs), uptake rates, elimination rates, and biological half-lives. First-order, single-compartment models described the toxicokinetics for both species. Uptake of RDX into oligochaetes was relatively rapid (uptake clearance constant [k(u)] of 5.17 ml/g/h) compared to that in catfish (k(u) = 1.28 ml/g/h). However, elimination also was more rapid in oligochaetes, with biological half-lives of 0.28 and 1.09 h for oligochaetes and catfish, respectively. Thus, both species had very similar estimated BCFs of 2.1 ml/g for oligochaetes and 2.0 ml/g for catfish. Accumulation of RDX in fish that were fed oligochaetes exposed to an exceedingly high water concentration of RDX was minimal. The present investigation indicates that RDX uptake via the aqueous route is the expected dominant uptake pathway, with dietary uptake contributing minimally to the overall body burden in fish inhabiting RDX-contaminated sites. Because of the exceedingly low bioaccumulative potential and low reported toxicity of RDX, the presence of this explosive in aquatic systems is unlikely to pose unacceptable risks to invertebrates and fish.