Acute and chronic toxicity of glyphosate compounds to glochidia and juveniles of Lampsilis siliquoidea (Unionidae)

Native freshwater mussels (family Unionidae) are among the most imperiled faunal groups in the world. Factors contributing to the decline of mussel populations likely include pesticides and other aquatic contaminants; however, there is a paucity of data regarding the toxicity of even the most globally distributed pesticides, including glyphosate, to mussels. Therefore, the toxicity of several forms of glyphosate, its formulations, and a surfactant (MON 0818) used in several glyphosate formulations was determined for early life stages of Lampsilis siliquoidea, a native freshwater mussel. Acute and chronic toxicity tests were performed with a newly established American Society of Testing and Materials (ASTM) standard guide for conducting toxicity tests with freshwater mussels. Roundup, its active ingredient, the technical-grade isopropylamine (IPA) salt of glyphosate, IPA alone, and MON 0818 (the surfactant in Roundup formulations) were each acutely toxic to L. siliquoidea glochidia. MON 0818 was most toxic of the compounds tested and the 48-h median effective concentration (0.5 mg/L) for L. siliquoidea glochidia is the lowest reported for any aquatic organism tested to date. Juvenile L. siliquoidea were also acutely sensitive to MON 0818, Roundup, glyphosate IPA salt, and IPA alone. Technical-grade glyphosate and Aqua Star were not acutely toxic to glochidia or juveniles. Ranking of relative chronic toxicity of the glyphosate-related compounds to juvenile mussels was similar to the ranking of relative acute toxicity to juveniles. Growth data from chronic tests was largely inconclusive. In summary, these results indicate that L. siliquoidea, a representative of the nearly 300 freshwater mussel taxa in North America, is among the most sensitive aquatic organisms tested to date with glyphosate-based chemicals and the surfactant MON 0818.     

Acute and chronic toxicity of technical-grade pesticides to glochidia and juveniles of freshwater mussels (Unionidae)

Chemical contaminants are among many potential factors involved in the decline of freshwater mussel populations in North America, and the effects of pesticides on early life stages of unionid mussels are largely unknown. The objective of this study was to determine the toxicity of technical-grade current-use pesticides to glochidia and juvenile life stages of freshwater mussels. We performed acute toxicity tests with glochidia (five species) and juveniles (two species) exposed to a suite of current-use pesticides including herbicides (atrazine and pendimethalin), insecticides (fipronil and permethrin), and a reference toxicant (NaCl). Because of limited availability of test organisms, not all species were tested with all pesticides. Toxicity tests with fungicides (chlorothalonil, propiconazole, and pyraclostrobin) were performed with one species (Lampsilis siliquoidea). Lampsilis siliquoidea glochidia and juveniles were highly sensitive to the fungicides tested but the technical-grade herbicides and insecticides, at concentrations approaching water solubility, were not acutely toxic to this or the other unionid species. In a 21-d chronic test with four-month-old juvenile L. siliquoidea, the 21-d median effective concentration (EC50) with atrazine was 4.3 mg/L and in atrazine treatments >or=3.8 mg/L mussel growth was significantly less than controls. The relatively high sensitivity of L. siliquoidea to chlorothalonil, propiconazole, and pyraclostrobin is similar to that reported for other aquatic organisms commonly used for toxicity testing. The relative risk associated with acute exposure of early life stages of mussels to technical-grade atrazine, pendimethalin, fipronil, and permethrin is likely low; however, survival and growth results with juvenile L. siliquoidea indicate that chronic exposure to high concentrations (>/=3.8 mg/L) of atrazine may have the potential to impact mussel populations and warrants further investigation.     

Acute and chronic toxicity of pesticide formulations (atrazine, chlorpyrifos, and permethrin) to glochidia and juveniles of Lampsilis siliquoidea

Freshwater mussels are among the most imperiled faunal groups in North America; approximately 67% of the nearly 300 native freshwater mussel species (family Unionidae) are listed as endangered, threatened, or of special concern. Despite evidence that glochidia and juvenile life stages are highly sensitive to some chemical contaminants, the effects of pesticides on early life stages of unionid mussels are largely unknown. In the United States, pesticide registration is based on toxicity data of the active ingredient, not formulations as they are sold and applied. Some pesticide formulations, however, are more toxic than their active ingredient (technical-grade pesticide) alone because of the presence of surfactants, adjuvants, or other ingredients in the formulation. The objective of the present study was to compare the toxicity of active ingredients of several current-use pesticides (atrazine, chlorpyrifos, and permethrin) to the toxicity of pesticide formulations to glochidia and juvenile life stages of a freshwater mussel (Lampsilis siliquoidea). The atrazine formulation (Aatrex) was more toxic than technical-grade atrazine in chronic tests with juvenile L. siliquoidea. For other pesticides, acute and chronic toxicity of technical-grade pesticides were similar to the toxicity of pesticide formulations. Median effective concentrations for chlorpyrifos were 0.43 mg/L for glochidia at 48 h, 0.25 mg/L for juveniles at 96 h, and 0.06 mg/L for juveniles at 21 d. Atrazine and permethrin as well as their formulations did not cause significant acute toxicity in glochidia or juveniles at exposure concentrations approaching water-solubility limits. Additional research is needed on other pesticides with different modes of action, on the role of different routes of exposure, and with other species of unionid mussels to evaluate similarities of toxic response.     

Acute and chronic toxicity of mercury to early life stages of the rainbow mussel, Villosa iris (Bivalvia: Unionidae)

Mercury (Hg) contamination is receiving increased attention globally because of human health and environmental concerns. Few laboratory studies have examined the toxicity of Hg on early life stages of freshwater mussels, despite evidence that glochidia and juvenile life stages are more sensitive to contaminants than adults. Three bioassays (72-h acute glochidia, 96-h acute juvenile, and 21-d chronic juvenile toxicity tests) were conducted by exposing Villosa iris to mercuric chloride salt (HgCl2). Glochidia were more sensitive to acute exposure than were juvenile mussels, as 24-, 48-, and 72-h median lethal concentration values (LC50) for glochidia were >107, 39, and 14 microg Hg/L, respectively. The 24-, 48-, 72-, and 96-h values for juveniles were 162, 135, 114, and 99 microg Hg/L, respectively. In the chronic test, juveniles exposed to Hg treatments > or = 8 microg/L grew significantly less than did control organisms. The substantial difference in juvenile test endpoints emphasizes the importance of assessing chronic exposure and sublethal effects. Overall, our study supports the use of glochidia as a surrogate life stage for juveniles in acute toxicity tests. However, as glochidia may be used only in short-term tests, it is imperative that an integrated approach be taken when assessing risk to freshwater mussels, as their unique life history is atypical of standard test organisms. Therefore, we strongly advocate the use of both glochidia and juvenile life stages for risk assessment.     

Evaluation of Lethality and Genotoxicity in the Freshwater Mussel <Emphasis Type="Italic">Utterbackia imbecillis</Emphasis> (Bivalvia: Unionidae) Exposed Singly and in Combination to Chemicals Used in Lawn Care

Many chemicals, including fertilizers, herbicides, and insecticides, are routinely applied to turf in the care and maintenance of lawns. These chemicals have the potential to leach into nearby surface waters and adversely affect aquatic biota. In this study, we evaluated the lethal and genotoxic effects of chemicals used in lawn care on an early life stage of freshwater mussels (Utterbackia imbecillis). The chemicals tested were copper and commercial formulations of atrazine, glyphosate, carbaryl, and diazinon. Mussel glochidia were exposed to chemicals singly or in combination (equitoxic and environmentally realistic mixtures) for 24 h and toxic interactions were evaluated with Markings additive index. Genotoxicity was quantified with the alkaline single-cell gel electrophoresis assay (Comet assay). In acute tests, copper was the most toxic of all chemicals evaluated (LC50 = 37.4 µg/L) and carbaryl was the most toxic of all pesticides evaluated (LC50 = 7.9 mg/L). In comparison to other aquatic organisms commonly used in toxicity tests (e.g., amphipods, cladocerans, and chironomids), mussel glochidia were as or more sensitive to the chemicals evaluated with the exception of diazinon, where mussels were observed to be less sensitive. The combined toxicity of equitoxic and environmentally realistic mixtures to mussels was additive. Genotoxic responses were observed in mussels exposed to copper, atrazine and diazinon at levels below their respective no-observed-effect concentrations. Together, these data indicate that freshwater mussels are among the most sensitive aquatic organisms tested for some chemicals commonly used in lawn care and that DNA damage may be useful as a screening tool to evaluate potential sublethal effects of lawn care products on non-target aquatic organisms.     

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

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

Ameliorative effects of sodium chloride on acute copper toxicity among Cope's gray tree frog (Hyla chrysoscelis) and green frog (Rana clamitans) embryos

Urban stormwater runoff is composed of a mixture of components, including polycyclic aromatic hydrocarbons, metals, deicing agents, and many others. The fate of these chemicals is often in stormwater detention ponds that are used by amphibians for breeding. Among aquatic organisms, the toxic mechanism for many metals involves interference with active Na(+) and Cl(-) uptake. Addition of cations has been shown to reduce the toxicity of metals among some aquatic organisms through competitive inhibition, but no studies have investigated the interaction between NaCl and Cu among amphibian embryos and larvae. To determine the degree to which NaCl may ameliorate the toxicity of Cu to amphibian embryos and larvae, the authors exposed Hyla chrysoscelis (Cope's gray treefrogs) and Rana (Lithobates) clamitans (green frogs) to seven levels of Cu and NaCl in fully factorial experiments. When exposure was in artificial hard water, Cu was highly toxic to both species (96-h median lethal concentration [LC50] of 44.7 μg/L and 162.6 μg/L for H. chrysoscelis and R. clamitans, respectively). However, approximately 500 mg/L of NaCl eliminated Cu toxicity over the range of Cu concentrations used in the experiments (maximum 150 μg Cu/L for H. chrysoscelis and 325 μg Cu/L for R. clamitans). The current results suggest that NaCl is likely responsible for the toxic effects of NaCl and metal mixtures that might be typical of runoff from road surfaces in northern latitudes.     

The thyroid endocrine disruptor perchlorate affects reproduction, growth, and survival of mosquitofish

The perchlorate anion--an oxidizer found in rockets, missiles, some ammunition, flares, airbags, and fireworks--occurs as a contaminant in ground and surface water in many parts of the United States. Its toxic effects include inhibition of thyroid hormone synthesis. To investigate its chronic toxicity, mosquitofish (Gambusia holbrooki) adults and fry were exposed to aqueous sodium perchlorate at 1, 10, and 100mg/L, and growth and reproductive performance (fecundity, eggs/embryos mass, and gonadosomatic index [GSI]) were determined. Five-day acute toxicity tests were also performed. Perchlorate had a stimulatory effect on fecundity, GSI, and egg/embryo mass, at least for some treatments. The LC50 of sodium perchlorate was 404 mg/L. Growth was enhanced at 1mg/L but inhibited at 10mg/L. These results suggest that, at environmentally relevant concentrations, perchlorate does not induce acutely toxic effects but may have mild stimulatory or hormetic effects on fitness parameters in this species.     

Phototoxicity of anthracene and pyrene to glochidia of the freshwater mussel Utterbackia imbecillis

The acute toxicity of photoactivated anthracene and pyrene to the glochidial larvae of the paper pondshell (Utterbackia imbecillis) was characterized in the laboratory using two sets of experiments. Acute toxicity tests designed to determine the overall sensitivity of glochidia to anthracene and pyrene were conducted under simulated sunlight (ultraviolet [UV]-A = 70+/-0.5 microW/cm2 [mean +/- standard deviation]). The median lethal concentration (LC50) and median lethal dose (LD50) of anthracene at 24 h were 1.93 (95% CI, 0.87-3.02) microg/L and 1.94 (1.87-2.00) microg/g glochidia, respectively. The LC50 and LD50 for pyrene at 24 h were 2.63 (2.38-2.90) microg/L and 6.36 (5.82-6.94) microg/g glochidia, respectively. Acute toxicity tests designed to delineate the relationship between the rate of mortality and UV intensity were conducted under one of four different UV intensities (UV-A = 15, 31, 50, and 68 microW/cm2). Regression analyses revealed that time to death decreased as tissue residue concentrations and UV intensity increased for both compounds. Based on measured tissue residues, anthracene was 1.5-fold more potent than pyrene and 3-fold more potent than fluoranthene. The lower potency of fluoranthene is in agreement with previously developed structure-activity relationships; however, these relationships predict equal potency between anthracene and pyrene. These findings suggest that glochidia of freshwater mussels are sensitive to photoactivated anthracene and pyrene at environmentally relevant concentrations, that the time-dependent mortality of glochidia can be accurately predicted through evaluating the product of tissue residue and light intensity, and that species-dependent factors may alter the predicted relative potencies of anthracene and pyrene.     

Chlorine toxicity to early life stages of freshwater mussels (Bivalvia: Unionidae)

Chlorine (Cl) is a highly toxic, widely used halogen disinfectant that is present in point-source pollution discharges from wastewater treatment plants and industrial facilities. The U.S. Environmental Protection Agency freshwater criteria for Cl are 19 microg total residual Cl (TRC)/L as a maximum 1-h average concentration and 11 microg TRC/L as a maximum 4-d average; however, toxicological data for unionids were not used in these calculations. To address this void in the data, we conducted acute tests with glochidia from several species and 21-d bioassays with three-month-old Epioblasma capsaeformis and three-, six-, and 12-month-old Villosa iris juveniles. The 24-h lethal concentration 50 values for glochidia were between 70 and 220 [Lg TRC/L, which are 2.5 to 37 times higher than those reported in other studies for cladocerans. Significant declines in growth and survivorship were observed in the 21-d test with E. capsaeformis at 20 microg TRC/L. Lowest-observed-adverse-effects concentrations in bioassays with juvenile V. iris were higher (30-60 microg TRC/L) but showed a significant trend of declining toxicity with increased age. Although endpoints were above water quality criteria, the long life spans of unionids and potential implications of chronic exposure to endangered juvenile mussels still warrant concern.     

Characterization of the acute toxicity of photoactivated fluoranthene to glochidia of the freshwater mussel, Utterbackia imbecillis

The acute photoactivated toxicity of fluoranthene to the glochidial larvae of the paper pondshell, Utterbackia imbecillis, was characterized in the laboratory using three sets of experiments. Toxicokinetic studies revealed that glochidia rapidly bioaccumulated fluoranthene, reaching an apparent steady state in 4 h. Based on a two-compartment model, uptake (Ku) and depuration (Kd) rate constants were 1394 ml/g/h and 0.769/h, respectively. However, experimental data suggested the presence of a fast and slow depuration compartment with a Kd of 0.290 and 0.031/h, respectively. Replicate 24-h acute toxicity tests designed to determine the overall sensitivity of glochidia to photoactivated fluoranthene were conducted under simulated sunlight (ultraviolet [UV]-A = 69.0 +/- 1.0 microW/cm2) (mean +/- standard deviation [SD]). Mean median lethal concentrations (LC50) of fluoranthene at 8, 16, and 24 h were 5.59 +/- 0.59, 4.09 +/- 0.57, and 2.45 +/- 0.45 micrograms/L, respectively. Mean median lethal doses (LD50) at the same time periods were 14.76 +/- 2.17, 11.66 +/- 2.82, and 6.98 +/- 1.31 micrograms/g dry weight, respectively. Acute toxicity tests designed to elucidate the relationship between the rate of mortality and UV intensity were conducted under one of four different UV intensities (UV-A = 15, 31, 50, and 68 microW/cm2). Regression analysis revealed that the time-dependent mortality of glochidia was inversely related to the product of initial tissue residue of fluoranthene and UV intensity. These findings suggest that glochidia of freshwater mussels are among the most sensitive organisms tested to date to photoactivated fluoranthene and the time-dependent mortality of glochidia can accurately be predicted through evaluation of the product of fluoranthene tissue residue and the light intensity to which the glochidia is exposed.     

Wastewater treatment polymers identified as the toxic component of a diamond mine effluent

The Ekati Diamond Mine, located approximately 300 km northeast of Yellowknife in Canada's Northwest Territories, uses mechanical crushing and washing processes to extract diamonds from kimberlite ore. The processing plant's effluent contains kimberlite ore particles (< or =0.5 mm), wastewater, and two wastewater treatment polymers, a cationic polydiallydimethylammonium chloride (DADMAC) polymer and an anionic sodium acrylate polyacrylamide (PAM) polymer. A series of acute (48-h) and chronic (7-d) toxicity tests determined the processed kimberlite effluent (PKE) was chronically, but not acutely, toxic to Ceriodaphnia dubia. Reproduction of C. dubia was inhibited significantly at concentrations as low as 12.5% PKE. Toxicity identification evaluations (TIE) were initiated to identify the toxic component of PKE. Ethylenediaminetetraacetic acid (EDTA), sodium thiosulfate, aeration, and solid phase extraction with C-18 manipulations failed to reduce PKE toxicity. Toxicity was reduced significantly by pH adjustments to pH 3 or 11 followed by filtration. Toxicity testing with C. dubia determined that the cationic DADMAC polymer had a 48-h median lethal concentration (LC50) of 0.32 mg/L and 7-d median effective concentration (EC50) of 0.014 mg/L. The anionic PAM polymer had a 48-h LC50 of 218 mg/L. A weight-of-evidence approach, using the data obtained from the TIE, the polymer toxicity experiments, the estimated concentration of the cationic polymer in the kimberlite effluent, and the behavior of kimberlite minerals in pH-adjusted solutions provided sufficient evidence to identify the cationic DADMAC polymer as the toxic component of the diamond mine PKE.     

Chronic toxicity of arsenic to the Great Salt Lake brine shrimp,Artemia franciscana

We determined the chronic toxicity of arsenic (sodium arsenate) to the Great Salt Lake brine shrimp, Artemia franciscana. Chronic toxicity was determined by measuring the adverse effects of arsenic on brine shrimp growth, survival, and reproduction under intermittent flow-through conditions. The study commenced with <24-h-old nauplii, continued through reproduction of the parental generation, and ended after 28 days of exposure. The concentrations tested were 4, 8, 15, 31, and 56mg/L dissolved arsenic. The test was conducted using water from the Great Salt Lake, Utah as the dilution water. Adult survival was the most sensitive biological endpoint, with growth and reproduction somewhat less sensitive than survival. The no observed effect concentration (NOEC) for survival was 8mg/L, and the lowest observed effect concentration (LOEC) was 15mg/L dissolved arsenic. The LOEC for growth and reproduction was greater than the highest concentration tested, 56mg/L. Based on survival, the final chronic value (geometric mean of the NOEC and LOEC) was 11mg/L dissolved arsenic. The F(1) generation appeared to acclimate to the prior arsenic exposure of the parental generation and was significantly less sensitive than the parental generation. For example, survival for the F(1) generation through day 12 was 100% in 56mg/L dissolved arsenic, compared to 26% for the parental generation. Growth of the F(1) generation was significantly less than that of the parental generation across all concentrations including the control, indicating a generational difference in brine shrimp growth rather than an arsenic effect. This study represents one of the few full life cycle toxicity tests conducted with brine shrimp.     

Toxicity of laundry detergent components to a freshwater cladoceran and their contribution to detergent toxicity

The toxicity of 39 laundry detergent components including surfactants, enzymes, builders, fabric brighteners, fillers, and coloring agents to the cladoceran Ceriodaphnia cf. dubia was determined. The difference between the most and the least toxic components was approximately 17,000-fold and 1,000,000-fold for the mg/L and mmol/L EC50 data, respectively. Two of the components had high toxicity (EC50 values < 1 mg/L), 11 moderate toxicity (EC50 values between 1 and 10 mg/L), and the remaining 26 components had low toxicity (EC50 values > 10 mg/L). Analysis revealed that mixtures of the components interacted antagonistically, additively, and synergistically. On a molarity basis the most toxic group of compounds was the surfactants followed by the brighteners. The most toxic individual components included sodium carboxymethyl cellulose, sodium silicate solution, four brighteners, sodium perborate tetrahydrate, and the surfactants. Many of the most toxic components, however, contributed very little to the toxicity of the detergents due to being present in the detergents at low concentrations. The main contributors to the toxicity of detergents were the sodium silicate solution and the surfactants-with the remainder of the components contributing very little to detergent toxicity. The potential for acute aquatic toxic effects due to the release of secondary or tertiary sewage effluents containing the breakdown products of laundry detergents may frequently be low. However, untreated or primary treated effluents containing detergents may pose a problem. Chronic and/or other sublethal effects that were not examined in this study may also pose a problem.     

Evaluation of Ionic Contribution to the Toxicity of a Coal-Mine Effluent Using Ceriodaphnia dubia

The United States Environmental Protection Agency has defined national in-stream water-quality criteria (WQC) for 157 pollutants. No WQC to protect aquatic life exist for total dissolved solids (TDS). Some water-treatment processes (e.g., pH modifications) discharge wastewaters of potentially adverse TDS into freshwater systems. Strong correlations between specific conductivity, a TDS surrogate, and several biotic indices in a previous study suggested that TDS caused by a coal-mine effluent was the primary stressor. Further acute and chronic testing in the current study with Ceriodaphnia dubia in laboratory-manipulated media indicated that the majority of the effluent toxicity could be attributed to the most abundant ions in the discharge, sodium (1952 mg/L) and/or sulfate (3672 mg/L), although the hardness of the effluent (792 ± 43 mg/L as CaCO₃) ameliorated some toxicity. Based on laboratory testing of several effluent-mimicking media, sodium- and sulfate-dominated TDS was acutely toxic at approximately 7000 μS/cm (5143 mg TDS/L), and chronic toxicity occurred at approximately 3200 μS/cm (2331 mg TDS/L). At a lower hardness (88 mg/L as CaCO₃), acute and chronic toxicity end-points were decreased to approximately 5000 μS/cm (3663 mg TDS/L) and approximately 2000 μS/cm (1443 mg TDS/L), respectively. Point-source discharges causing in-stream TDS concentrations to exceed these levels may risk impairment to aquatic life.     

Toxicity of organophosphorus insecticides in the zebra mussel, Dreissena polymorpha P.

The 96-h toxicity of four organophosphates (thiometon, disulfoton, malathion, and demeton-S-methyl, the oxygen analogue of thiometon) in the freshwater bivalve mollusc Dreissena polymorpha was tested using different nominal concentrations ranging between 6 and 50 mg/L. No mortalities were observed in mussels exposed to malathion and demeton-S-methyl (26 mg/L and 6 mg/L, respectively), and at the lowest concentrations of thiometon and disulfoton (6 and 10 mg/L, respectively). At higher thiometon and disulfoton concentrations, mortalities occurred. At the highest concentrations of 50 mg thiometon/L and 30 mg disulfoton/L, mussel mortalities of 88 and 93%, respectively, were determined. Organophosphate concentrations of up to a factor 10 times higher than in the ambient water were found in exposed mussels, irrespective of whether they were alive or dead. The search for organophosphate metabolites via GC/MS analysis of mussel tissue extracts was negative, suggesting lacking or low oxidative activation of the insecticides used. The mollusc is highly resistant to toxic effects of organophosphate insecticides and their biological active oxygen analogues.     

给水处理中含砷污泥的浸出毒性和初步处置研究

目的研究混凝微滤工艺处理高砷饮用水所产生的铁盐和铝盐含砷污泥的浸出毒性,以及含砷污泥的处置与利用方法。方法采用中国国家标准方法和USEPA的TCLP方法检验了含砷污泥的浸出毒性,并采用水泥固化的方法对含砷污泥的处置进行了初步研究。将铁盐含砷污泥添加到路用基材中,探讨其废物利用的可能性。结果铁盐和铝盐含砷污泥TCLP方法浸出液中砷的浓度分别为118μg/L和420μg/L,高于国家标准方法的9.5μg/L和11.8μg/L,但两种方法测定的浸出毒性均低于危险废物浸出毒性的国家标准。普通硅酸盐水泥固化体的TCLP浸出液中砷浓度仅为污泥的10%左右,固化体的无侧限抗压强度分别为3.25MPa和0.76MPa,可以满足堆放要求。掺入少量铁盐含砷污泥的路用基材强度提高12%左右。结论给水处理中含砷污泥不属于具有浸出毒性的危险废物,水泥固化是处置含砷污泥的有效方法,将少量铁盐含砷污泥添加到路用基材中使含砷污泥得到了有效利用,又避免了可能出现的环境污染问题。     

Toxicity of uranium, molybdenum, nickel, and arsenic to Hyalella azteca and Chironomus dilutus in water-only and spiked-sediment toxicity tests

A series of laboratory spiked-sediment toxicity tests with the amphipod Hyalella azteca and the midge Chironomus dilutus were undertaken to determine acute and chronic toxicity thresholds for uranium (U), molybdenum (Mo), nickel (Ni), and arsenic (As) based on both whole-sediment (total) and pore water exposure concentrations. Water-only toxicity data were also generated from separate experiments to determine the toxicities of these metals/metalloids under our test conditions and to help evaluate the hypothesis that pore water metal concentrations are better correlated with sediment toxicity to benthic organisms than whole-sediment metal concentrations. The relative toxicity of the four elements tested differed depending on which test species was used and whether whole-sediment or pore water metal concentrations were correlated with effects. Based on measured whole-sediment concentrations, Ni and As were the two most acutely toxic elements to H. azteca with 10-d LC50s of 521 and 532 mg/kg d.w., respectively. Measured pore water concentrations indicated that U and Ni were the two most acutely toxic elements, with 10-d LC50s to H. azteca of 2.15 and 2.05 mg/L, respectively. Based on pore water metal concentrations, the no-observed-effect concentrations (NOECs) for growth were (H. azteca and C. dilutus, respectively) 0.67 and 0.21 mg/L for U, <0.37 and 0.60 mg/L for Ni, and 16.43 and <0.42 mg/L for As. Pore-water lowest-observed-effect concentrations (LOECs) for growth were (H. azteca and C. dilutus, respectively) 2.99 and 0.48 mg/L for U, 0.37 and 2.33 mg/L for Ni, and 58.99 and 0.42 mg/L for As. For U and Ni, results from 96-h water-only acute toxicity tests correlated well with pore water metal concentrations in acutely toxic metal-spiked sediment. This was not true for As where metalloid concentrations in overlying water (diffusion from sediment) may have contributed to toxicity. The lowest whole-sediment LOEC reported here for As was 6.6- and 4-fold higher than the Canadian Council of Ministers of the Environment interim sediment quality guideline and the Canadian Nuclear Safety Commission (CNSC) lowest effect level (LEL), respectively. The lowest whole-sediment LOECs reported here for Ni, U and Mo were 4-, 17.5-, and >260-fold higher, respectively, than the CNSC LELs for these metals/metalloids. Data on pore water metal concentrations in toxic sediment would be a useful addition to future Guidelines documents.     

Assimilation and physiological effects of ferrocyanide on weeping willows

Uptake, assimilation, and toxicity of exogenous iron cyanide complexes in plants were investigated. Pre-rooted young weeping willows (Salix babylonica L.) were exposed to hydroponic solutions spiked with potassium ferrocyanide at 24.0 ± 1°C for 192 h. Transpiration rates, chlorophyll contents, soluble protein, and activities of superoxide dismutases (SOD), catalase (CAT), and peroxidase (POD) of the plants were monitored to determine toxicity to the cuttings. Of all selected parameters, POD activity in leaves was the most sensitive bioindicator to the increase of ferrocyanide concentrations. Between 11% and 19% of applied ferrocyanide in the solutions was removed by willows at the end of the incubation period. Only small amounts of ferrocyanide were recovered in different parts of the plant materials. Mass balance analysis showed that more than 90% of the ferrocyanide taken up from the hydroponic solutions was assimilated by plants. The assimilation of ferrocyanide by plants showed a dose-dependent manner. These findings suggest that phytoremediation of ferrocyanide-contaminating wastewater and soils can be possible for the environmental cleaning up.     

Evaluation of influence of sediment on the sensitivity of a unionid mussel (Lampsilis siliquoidea) to ammonia in 28-day water exposures

A draft update of the U.S. Environmental Protection Agency ambient water quality criteria (AWQC) for ammonia substantially lowers the ammonia AWQC, primarily due to the inclusion of toxicity data for freshwater mussels. However, most of the mussel data used in the updated AWQC were generated from water-only exposures and limited information is available on the potential influence of the presence of a substrate on the response of mussels in laboratory toxicity tests. Our recent study demonstrated that the acute sensitivity of mussels to ammonia was not influenced by the presence of substrate in 4-d laboratory toxicity tests. The objective of the current study was to determine the sensitivity of mussels to ammonia in chronic 28-d water exposures with the sediment present (sediment treatment) or absent (water-only treatment). The chronic toxicity test was conducted starting with two-month-old juvenile mussels (fatmucket, Lampsilis siliquoidea) in a flow-through diluter system, which maintained consistent pH (≈8.3) and six concentrations of total ammonia nitrogen (N) in overlying water and in sediment pore water. The chronic value (ChV, geometric mean of the no-observed-effect concentration and the lowest-observed-effect concentration) was 0.36 mg N/L for survival or biomass in the water-only treatment, and was 0.66 mg N/L for survival and 0.20 mg N/L for biomass in the sediment treatment. The 20% effect concentration (EC20) for survival was 0.63 mg N/L in the water-only treatment and was 0.86 mg N/L in the sediment treatment (with overlapping 95% confidence intervals; no EC20 for biomass was estimated because the data did not meet the conditions for any logistic regression analysis). The similar ChVs or EC20s between the water-only treatment and the sediment treatment indicate that the presence of sediment did not substantially influence the sensitivity of juvenile mussels to ammonia in the 28-d chronic laboratory water exposures.