Influence of water hardness and sulfate on the acute toxicity of chloride to sensitive freshwater invertebrates

Total dissolved solids (TDS) represent the sum of all common ions (e.g., Na, K, Ca, Mg, chloride, sulfate, and bicarbonate) in freshwater. Currently, no federal water quality criteria exist for the protection of aquatic life for TDS, but because the constituents that constitute TDS are variable, the development of aquatic life criteria for specific ions is more practical than development of aquatic life criteria for TDS. Chloride is one such ion for which aquatic life criteria exist; however, the current aquatic life criteria dataset for chloride is more than 20 years old. Therefore, additional toxicity tests were conducted in the current study to confirm the acute toxicity of chloride to several potentially sensitive invertebrates: water flea (Ceriodaphnia dubia), fingernail clams (Sphaerium simile and Musculium transversum), snail (Gyraulus parvus), and worm (Tubifex tubifex), and determine the extent to which hardness and sulfate modify chloride toxicity. The results indicated a significant ameliorating effect of water hardness (calcium and magnesium) on chloride toxicity for all species tested except the snail; for example, the 48-h chloride median lethal concentration (LC50) for C. dubia at 50?mg/L hardness (977?mg Cl(-) /L) was half that at 800?mg/L hardness (1,836?mg Cl(-) /L). Conversely, sulfate over the range of 25 to 600?mg/L exerted a negligible effect on chloride toxicity to C. dubia. Rank order of LC50 values for chloride at a given water hardness was in the order (lowest to highest): S. simile?相似文献   

Effects of sulfate on the acute toxicity of selenate to freshwater organisms

This study evaluated the relationship between ambient sulfate concentrations and acute selenate toxicity to freshwater aquatic life. Previous studies indicated that increasing sulfate concentrations reduced selenate bioconcentration and toxicity. However, these studies generally were not conducted in a manner that was conducive to their use in deriving a water quality criterion. We compiled results from previous studies and generated additional data to help define a selenate-sulfate relationship for acute toxicity. Selenate toxicity was determined in standardized test waters with varying sulfate concentrations using Ceriodaphnia dubia, Gammarus pseudolimnaeus, Hyalella azteca, and Pimephales promelas as the test organisms. Analysis of test results indicated that a significant relationship does exist between acute selenate toxicity and ambient sulfate concentrations. Data from these tests and previous studies were combined to develop a statistical relationship sufficiently robust to derive a sulfate-dependent water quality criterion for selenate. The relationship is similar to those commonly derived between divalent metals and hardness to adjust water quality criteria.     

Comparative toxicity of fluoranthene and pentachlorobenzene to three freshwater invertebrates

This study examined the temporal component of pentachlorobenzene lethal body residues among three freshwater invertebrates. Also, using previous fluoranthene data allowed a more detailed examination of the role of biotransformation in lethal body residues and comparisons of lethal residues across chemical classes. Time-dependent toxicity of fluoranthene and pentachlorobenzene were compared among Hyalella azteca, Chironomus tentans, and Diporeia spp. Lethal body residues required for 50% mortality (LR50) were not constant and decreased with exposure time for all species. Fluoranthene was most toxic to C. tentans with LR50 values of 0.38 micromol x g(-1) at 2 d to 0.15 micromol x g(-1) at 10 d and least toxic to Diporeia spp. with values of 9.97 micromol x g(-1) at 10 d to 3.67 micromol x g(-1) at 28 d. The LR50 values for H. azteca were intermediate and ranged from 2.25 micromol x g(-1) at 5 d to 0.56 micromol x g(-1) at 28 d. Pentachlorobenzene LR50 values were less variable among species and ranged from 1.20 micromol x g(-1) at 4 d to 0.81 micromol x g(-1) at 10 d for C. tentans, 5.0 micromol x g(-1) at 20 d and 2.75 micromol x g(-1) at 28 d for Diporeia spp., and 1.51 micromol x g(-1) at 4 d and 0.71 micromol x g(-1) at 28 d for H. azteca. When LR50 values for fluoranthene and pentachlorobenzene were compared at steady state, the lethal residues for the amphipod species were within the range expected for nonpolar narcotic chemicals (anesthetics); however, C. tentans was more sensitive to fluoranthene than pentachlorobenzene, confirming our previous hypothesis that biotransformation of fluoranthene likely produces a metabolite(s) acting by some specific mechanism of action. The information collected from this study allows a greater understanding of residue-response relationships, specifically relative species sensitivities.     

Effects of water hardness and temperature on the acute toxicity of mercuric chloride on rainbow trout (Oncorhynchus mykiss)

In this study, the toxicity of mercuric chloride (HgCl(2)), an important pollutant threatening water resources for many years, and the effects of water temperature and hardness on the toxicity in cultured rainbow trout Oncorhynchus mykiss (4.79 ± 0.16 g; 7.38 ± 0.24 cm; mean ± SD) were investigated at different temperatures (12 and 17°C) and hardness concentrations (35, 70 and 120 mg l(-1) as calcium carbonate, CaCO(3)). For this purpose, the acute toxicity tests were performed by 96-h static tests in different water temperatures and water hardness concentrations. For acute toxicity tests, solutions ranging from 0.4 to 1.2 mg l(-1) were used at 12°C and solutions ranging from 0.4 to 1.0 mg l(-1) at 17°C. The LC(50) values of HgCl(2) that killed 50% of rainbow trout within 96 h in the hardness concentrations of 35, 70 and 120 mg l(-1) CaCO(3) were calculated using probit analysis, and were found to be 0.725, 0.788, 0.855 mg l(-1) at 12°C and 0.670, 0.741, 0.787 mg l(-1) at 17°C, respectively. Consequently, the toxicity of HgCl(2) on rainbow trout decreased when the temperature decreased from 17 to 12°C. Toxicity increased when the hardness decreased from 120 to 35 mg l(-1) CaCO(3). In contrast to temperature, water hardness presents a negative effect on the toxicity of HgCl(2).     

Effect of humic acids on toxicity of DDT and chlorpyrifos to freshwater and estuarine invertebrates

The effects of dissolved humic acids (HAs) on the acute toxicities of the organophosphate pesticide chlorpyrifos and the organochlorine pesticide 4,4'-dichlorodiphenyltrichloroethane (DDT) were assessed by using freshwater crustaceans (Ceriodaphnia dubia) and saltwater crustaceans (Americamysis bahia). The effects of filtered Aldrich HAs (10-100 mg/L) on organism mortality were determined. Humic acids had no effect on mortality of A. bahia for either pesticide at a salinity of 20 parts per thousand, but greatly reduced the mortality of C. dubia for both pesticides in freshwater (0 parts per thousand). In the latter case, the effect was proportional to the HA concentration. The difference in toxicity mitigation as a function of salinity is believed to be due to conformational changes in the HA molecules, which impact pesticide-HA binding, rather than to organismal effects.     

Effects of diet,water hardness,and population source on acute and chronic copper toxicity toCeriodaphnia dubia

The effects of diet, water hardness, and population source on acute toxicity, and diet and water hardness on chronic toxicity of copper (Cu) toCeriodaphnia dubia were evaluated. A diet of three algae (Chlamydomonas rheinhardti, Ankistrodesmus falcatus, and Chlorella vulgaris, hereafter referred to as CAC) cultured in vitaminenriched media was superior to synthetic diets consisting of yeast, Cerophyll, and trout chow (YCT). Neonates from mothers reared on CAC were 1.4 to 1.5 times more resistant to Cu than those reared on YCT or yeast and Cerophyll (YC). Forty-eight hr LC50s of Cu toC. dubia increased from 35 to 79 g/L at water hardness of 94 and 170 mg CaCO₃/L. Three populations ofCeriodaphnia derived from three USEPA (United States Environmental Protection Agency) laboratories showed no differential Cu sensitivity. Chronic Cu impairment was measured by neonate production in the 7-day life-cycle test. Chronic values were 7.9 and 10.1 g/L at water hardnesses of 94 and 170 mg/L respectively. A comparison of daily water renewal and renewal on days 3 and 5 only was made. Neonate production was significantly greater using day 3 and 5 renewals (Friedmann's Rank Sum Test, p < 0.005), even though Cu concentrations were comparable between the two tests. Therefore, handling stress may have been incurred using daily changes. It is recommended that future tests and USEPA guidelines should address deleting YCT and including multi-algal diets for culturing and chronic testing ofCeriodaphnia.     

The toxicity of waterborne boron toDaphnia magna andChironomus decorus and the effects of water hardness and sulfate on boron toxicity

The concentrations of many elements, including boron, are increasing in aquatic ecosystems due to anthropogenic activities. Laboratory studies were undertaken to evaluate the toxicity of waterborne boron to two key fresh water macroinvertebrates and to evaluate the effects of water hardness and sulfate on boron toxicity. Acute toxicity evaluations of waterborne sodium tetraborate resulted in 48 h. LC₅₀ values of 141 and 1376 mg B/L for neonateDaphnia magna and fourth instarChironomus decorus, respectively. Chronic sublethal studies demonstrated a significant decrease inC. decorus growth rate at 20 mg B/L. Further studies showed that increasing water hardness (10.6 to 170 mg/L as CaCO₃) and sulfate (10.2 to 325.4 mg SO₄ ^–1/L) concentrations did not affect boron toxicity toD. magna. These results, in conjunction with a review of the literature, suggest that aquatic macrophytes may be more sensitive to boron than macroinvertebrates and thus would be better choices for aquatic risk assessment evaluations for this element.     

Histopathological changes induced by acute toxicity of mercuric chloride on the epidermis of freshwater catfish--Heteropneustes fossilis (Bloch).

The toxic effects of 0.3 ppm (96-hr LC50 value) of mercuric chloride solution on the epidermis of Heteropneustes fossilis at different time intervals have been studied. The epidermis reacts instantaneously by secreting a profuse amount of slime, especially due to hyperactivity of the goblet mucous cells which subsequently degenerate and get lost. Later, all other cell types also get entangled in the degenerative process. The damaged cells, especially the club cells, get sloughed at the surface, forming a thick crust of debris from the degenerating cells. Side-by-side regeneration of the epidermis also continues from the lower layers of the intact tissue with the addition of all the cell types. However, even before attaining maturity, these budding cells, especially the club cells, show signs of degeneration, their degeneration occurring faster than their regeneration. Thus most of the space left behind by the degenerated club cells gets quickly filled with haphazardly arranged polygonal epithelial cells, giving the epidermis an altogether different morphology.     

Partial life-cycle and acute toxicity of perfluoroalkyl acids to freshwater mussels

Freshwater mussels are among the most sensitive aquatic organisms to many contaminants and have complex life-cycles that include several distinct life stages with unique contaminant exposure pathways. Standard acute (24-96 h) and chronic (28 d) toxicity tests with free larva (glochidia) and juvenile mussels are effective at generating data on contaminant effects at two discrete life stages but do not incorporate effects on brooded glochidia. We developed a novel partial life-cycle assay that incorporates exposures to brooding adult female mussels and used this method in combination with acute toxicity tests to assess adverse effects of perfluoroctanesulfonic acid (PFOS) and perfluoroctanoic acid (PFOA) on freshwater mussels. Fatmucket (Lampsilis siliquoidea) were exposed to PFOS at two life stages: brooding glochidia (in marsupia) for 36 d and free glochidia in water for 24 h. In standard acute tests with glochidia (24-48 h exposures) and juveniles (48-96 h exposures) of fatmucket and black sandshell (Ligumia recta), glochidia were 8 to 25 times more sensitive than juveniles. Perfluoroctanesulfonic acid significantly reduced the duration of glochidia viability and reduced probability of metamorphosis at concentrations 3,000 times lower than the most sensitive acute endpoint (24-h EC50). The partial life-cycle test is adaptable to a variety of endpoints and research objectives and is useful for identifying adverse effects at contaminant concentrations below those required for an acute lethal response.     

Determinants of variability in acute to chronic toxicity ratios for aquatic invertebrates and fish

Variability in acute to chronic ratios (ACRs; median lethal or effect concentration divided by chronic value) has been of continuing interest in aquatic toxicology because of the reliance on ACRs to estimate chronic toxicity for chemicals and species with known acute toxicity data but with limited or no information for chronic toxicity. To investigate the variability and significant differences in ACRs, an extensive data set was compiled of 456 same-species pairs of acute and maximum acceptable toxicant concentrations for metals, narcotics, pesticides, and other organic chemicals. The overall median value for 456 aquatic invertebrate and fish ACRs analyzed in the present study was 8.3, with a 16,000-fold range in values (1.1-18,550) and a 32-fold range in 10th and 90th percentile values (2.5-79.5). Median ACRs for taxa, ambient habitat media, chronic test end point, and chemical mode of action (MOA)/class categories generally were similar but, in some cases, extremely variable (ranges of 1 to >10,000). No significant differences (p 相似文献   

Toxicity of carbon nanotubes to freshwater aquatic invertebrates

Carbon nanotubes (CNTs) are hydrophobic in nature and thus tend to accumulate in sediments if released into aquatic environments. As part of our overall effort to examine the toxicity of carbon-based nanomaterials to sediment-dwelling invertebrates, we have evaluated the toxicity of different types of CNTs in 14-d water-only exposures to an amphipod (Hyalella azteca), a midge (Chironomus dilutus), an oligochaete (Lumbriculus variegatus), and a mussel (Villosa iris) in advance of conducting whole-sediment toxicity tests with CNTs. The results of these toxicity tests conducted with CNTs added to water showed that 1.00 g/L (dry wt) of commercial sources of CNTs significantly reduced the survival or growth of the invertebrates. Toxicity was influenced by the type and source of the CNTs, by whether the materials were precleaned by acid, by whether sonication was used to disperse the materials, and by species of the test organisms. Light and electron microscope imaging of the surviving test organisms showed the presence of CNTs in the gut as well as on the outer surface of the test organisms, although no evidence was observed to show penetration of CNTs through cell membranes. The present study demonstrated that both the metals solubilized from CNTs such as nickel and the "metal-free" CNTs contributed to the toxicity.