Chronic toxicity of a copper, cadmium and zinc mixture to the fathead minnow (Pimephales promelas rafinesque)

Fathead minnows were exposed to a series or concentrations of a copper, cadmium and zinc mixture during a 12.5 month chronic test in water of 200 mg 1⁻¹ total hardness. The metal concentrations in the mixture were selected on the basis of results obtained during previous chronic exposures to each of the metals individually in the same water. Strict summation of the chronic toxicities of the metals was not indicated when they were tested in combination. Toxic effects of the mixture attributable to copper appeared to be increased, but that attributable to cadmium was reduced. The effects thought to be due to zinc were similar in degree to those observed in the single chronic exposure. Summation of effects resulting from a mixture containing about the same proportions of copper, cadmium and zinc occurred at a much higher, acutely lethal concentration. A lethal threshold was attained in the mixture when each metal was present at a concentration of 0.4 or less of its individual lethal threshold.     

Aspects of water quality and the toxicity of copper to rainbow trout

Studies were made of the effects of additions of a sewage effluent, an amino acid, humic substances, and suspended organic matter on the acute lethal toxicity of water containing copper sulphate to rainbow trout. In all cases the toxicity of a given total concentration of copper was quantitatively reduced. It was concluded that neither the total concentration of copper nor that of “soluble” copper in a water could be used to determine the toxicity to fish which was attributable to copper. It was also concluded that data from toxicity tests with copper in which natural surface waters are used for dilution purposes cannot define the true toxicity of copper or have application to other natural waters except when the concentrations of the toxic chemical species are known.     

Toxicity of sodium nitrilotriacetate (NTA) to the fathead minnow and an amphipod in soft water

Amphipods, Gammarus pseudolimnaeus Bousfield and fathead minnows, Pimephales promelas Rafinesque, were submitted to acute (96-h) and chronic (generation-cycle) bioassays with sodium nitrilotriacetic acid (NTA). All measurements are reported as Na₃NTA. The average 96-h TL50 values under flow-through conditions were 98 mg 1⁻¹NTA for the amphipod and 114 mg 1⁻¹ for the fathead minnow. The acute toxicity of NTA was caused in part by the high pH resulting from the addition of large amounts of NTA (> 100 mg 1⁻¹) to soft water. Controlling pH reduced the lethality of NTA by at least one-half to fathead minnow larvae. The chronic no-effect level of NTA to the amphipods was 19 mg 1⁻¹; in fathead minnows, it exceeded the highest exposure level (> 54 mg 1⁻¹).     

Effects of pH increases and sodium chloride additions on the acute toxicity of 2,4-dichlorophenol to the fathead minnow

The observable toxic effects produced by short-term exposure of fathead minnows (Pimephales promelas) to 2,4-dichlorophenol were reduced when the pH of the test water was increased by the addition of NaOH. After exposure for 192 h to 7.43 mg 2,4-dichlorophenol l^-1, the average survival of fathead minnows ranged from 28% at pH 7.57 to 100% at pH 9.08. Normal schooling behaviour was completely disrupted, and the equilibrium of most fish was affected after a 24-h exposure to 7.43 mg 2,4-dichlorophenol 1^-1 at pH 7.57, but neither schooling nor equilibrium were affected even after 192 h at pH 8.68 and 9.08. Schooling and swimming behaviour of fathead minnows exposed to 12.33 mg 2,4-dichlorophenol l^-1 were affected at all pH levels. Survival of these fish after 24 h ranged from 0% at pH 7.84–46% at pH 8.81. Sodium chloride in concentrations ranging from 0 to 13.9 mg l^-1 had no observable effects on the acute toxicity of 2,4-dichlorophenol to fathead minnows.     

Sublethal toxicity of commercial insecticide formulations and their active ingredients to larval fathead minnow (Pimephales promelas)

Toxic effect concentrations of insecticides are generally determined using the technical grade or pure active ingredient. Commercial insecticide formulations, however, contain a significant proportion (> 90%) of so-called inert ingredients, which may alter the toxicity of the active ingredient(s). This study compares the sublethal toxicity of two insecticides, the pyrethroid bifenthrin, and the phenylpyrazole fipronil, to their commercial formulations, Talstar® and Termidor®. Both insecticides are used for landscape treatment and structural pest control, and can be transported into surface water bodies via stormwater and irrigation runoff. We used larval fathead minnow (Pimephales promelas), to determine effects on growth and swimming performance after short-term (24 h) exposure to sublethal concentrations of pure insecticides and the respective formulations. Significantly enhanced 7 d growth was observed at 10% of the 24 h LC₁₀ (53 μg L⁻¹) fipronil. Swimming performance was significantly impaired at 20% of the 24 h LC₁₀ (0.14 μg L⁻¹) of bifenthrin and 10% of the 24 h LC₁₀ of Talstar® (0.03 μg L⁻¹). Fipronil and Termidor® led to a significant impairment of swimming performance at 142 μg L⁻¹ and 148 μg L⁻¹ respectively, with more pronounced effects for the formulation. Our data shows that based on dissolved concentrations both formulations were more toxic than the pure active ingredients, suggesting that increased toxicity due to inert ingredients should be considered in risk assessments and regulation of insecticides.     

Epidemiological investigation on chronic copper toxicity to children exposed via the public drinking water supply

Copper in drinking water has been associated with Non-Indian Childhood Cirrhosis (NICC), a form of early childhood liver cirrhosis. This epidemiological study examines the exposition of infants to increased copper concentrations through drinking water from public water supplies in Berlin, Germany, and if this dietary copper intake can cause liver damage in early childhood. In total, water samples from 2944 households with infants were tested for copper. Mean copper concentrations in the two different types of collected composite samples were 0.44 and 0.56 mg/l, respectively. Families having a copper concentration at or above 0.8 mg/l in one or both of the composite samples (29.9% of all sampled households) and a defined minimum ingestion of tap water of their infant were recommended to undergo a paediatric examination. Nearly every of the 541 recommended infants were examined by a local paediatrician and of these 183 received a blood serum analysis, too. None of the infants had clear signs of a liver disease although a few serum parameters lay outside the accompanying reference range and abdominal ultrasound imaging gave slightly unusual results in five cases. Additionally, no signs of a negative health effect could be found in the statistical analysis of the serum parameters GOT, GPT, GGT, total bilirubin, serum copper, or ceruloplasmin in relation to estimated daily and total copper intakes of the infants from tap water. No dose relation of serum parameters and estimated copper intakes could be established. From the results of the study, no confirmed indication of a liver malfunction in infants whose food had been prepared using tap water with an elevated copper concentration could be found and, therefore, no indication of a hazard due to copper pipes connected to public water supplies could be detected.     

Effect of exposure time and copper concentration on reproduction of the fathead minnow (Pimephales Promelas)

Three concurrent studies were conducted to determine the chronic effect of prespawning exposure to various concentrations of copper on fathead minnow reproduction. Copper was introduced into the three exposure systems to give 6-, 3-, and 0-months exposure prior to spawning. Prespawning exposure time had no significant effect on reproduction. Number of eggs produced per female decreased, however, with increase in copper concentrations. Egg production at copper concentrations of 37μg 1⁻¹ and higher was significantly lower (P = 0.05) than in the control, but at concentrations of 24μg 1⁻¹ and lower it was not different. The maximum acceptable toxicant concentration (MATC) was estimated to be 32μg Cu 1⁻¹, which is 0.07 of the 96h LC₅₀. This application factor for copper is similar to those found in other studies.     

A comparison of toxicity tests conducted in the laboratory and in experimental ponds using cadmium and the fathead minnow (Pimephales promelas)

Acute toxicity tests were conducted in the laboratory with fathead minnows (Pimephales promelas) to determine the 96-h LC₅₀ of cadmium under three conditions: (1) in laboratory water, (2) in water from experimental ponds, and (3) in pond water underlain by sediment. Cadmium was then applied at doses equivalent to the estimated LC₅₀ values to 0.07-ha ponds containing caged fathead minnows. A cadmium ion selective electrode, ultrafiltration, and equilibrium calculations were used to determine cadmium speciation, and several water quality characteristics were measured to correlate differences in mortality between test systems (laboratory and field) with observed differences in water quality. The LC₅₀ estimates (mg l⁻¹) for the bioassays were 4.39 for the laboratory water, 3.52 for the pond water with sediment, and 2.91 for the pond water. Concentrations of Cd²⁺ decreased and those of cadmium in the particulate (> 1.2 μm) and 300,000 mol. wt (0.018–1.2 μm) fractions increased over the 96-h; cadmium in these fractions was believed to consist of colloidal sized CdCO₃ precipitates. Concentrations of Cd²⁺ decreased at different rates between test systems, regulated by the degree of CdCO₃(s) supersaturation which in turn depended on pH and total metal concentrations. Differences in toxicity in the laboratory tests were attributed to differences in water hardness and Cd²⁺ concentrations. Mortality of fathead minnows was low (0–10%) during the 96-h test period in the ponds due to the higher pH, which produced supersaturated conditions resulting in the rapid formation of nontoxic CdCO₃ precipitates and a more rapid decrease in Cd²⁺ concentrations as compared to the laboratory bioassays.     

Acute and chronic systemic chromium toxicity

Although chromium and compounds containing it have been recognized as having potential severe adverse effects on health for more than 160 years, understanding of the systemic toxicology and true hazard of these compounds is still not complete. A review of the current state of knowledge is attempted in this paper, with appropriate attention given to the complications of multiple valence states and solubility. Selected chromium compounds, particularly hexavalent ones, are carcinogens, corrosives, delayed contact sensitizers, and have the kidney as their primary target organ. But chromium is also an essential element for humans. The body clearly possesses some effective detoxification mechanisms for some degree of exposure to hexavalent chrome compounds. The significant features of acute and chronic chromium toxicity are presented in view of these considerations.     

Acute and chronic toxicity of lead to rainbow trout salmo gairdneri, in hard and soft water

Lead was found to be highly toxic to rainbow trout in both hard water (hardness 353 mg l⁻¹ as CaCO₃) and soft water (hardness 28 mg l⁻¹. Analytical results differ greatly with methods of analysis when measuring concentrations of lead in the two types of water. This is exemplified in LC50's and maximum acceptable toxicant concentrations (MATC's) obtained when reported as dissolved lead vs total lead added in hard water. Two static bioassays in hard water gave 96-h LC50's of 1.32 and 1.47 mg l⁻¹ dissolved lead vs total lead LC50's of 542 and 471 mg l⁻¹, respectively. In a flow-through bioassay in soft water a 96-h LC50 of 1.17 mg l⁻¹, expressed as either dissolved or total lead, was obtained. From chronic bioassays, MATC's of lead for rainbow trout in hard water were between 18.2 and 31.7 μg l⁻¹ dissolved lead vs 120–360 μg l⁻¹ total lead. In soft water, where exposure to lead was initiated at the eyed egg stage of development, the MATC was between 4.1 and 7.6 μg l⁻¹. With exposure to lead beginning after hatching and swim-up of fry, the MATC was between 7.2 and 14.6 μg l⁻¹. Therefore, fish were more sensitive to the effects of lead when exposed as eggs.     

Chronic effect of low pH on fathead minnow survival, growth and reproduction

Fathead minnows (Pimephales promelas Rafinesque) were continuously exposed to reduced pH levels of 4.5, 5.2, 5.9, 6.6 and 7.5 (control) during a 13-month, one-generation test. Survival was not affected, even at the lowest pH tested. Fish behavior was abnormal, and fish were deformed at pH 4.5 and 5.2. Egg production and egg hatchability were reduced at pH 5.9 and lower, and all eggs were abnormal. A pH of 6.6 was marginal for vital life functions, but safe for continuous exposure. Free carbon dioxide, liberated by the addition of sulfuric acid to reduce the pH, may have had an unknown effect. The fish did not become acclimated to low pH levels.     

Induction of CYP1A and DNA damage in the fathead minnow (Pimephales promelas) following exposure to biosolids

Biosolids (treated sewage sludge) are increasingly disposed of on land. Thus particle-sorbed and dissolved constituents have the potential to enter nearby watersheds. Although organic contaminants are known to be present in biosolids these are not currently regulated and little data exist on their potential toxicity to aquatic organisms. We exposed Pimephales promelas to two concentrations of biosolids (0.5 and 2.5 g l(-1)) for 28-days (static-renewal) and characterized contaminants present and the extent of CYP1A and DNA damage induction at various time points. Many organic contaminants were detected in the biosolids, with polycyclic aromatic hydrocarbons (PAHs) being the dominant class. Substantial levels of polybrominated diphenyl ethers (PBDEs) and nonylphenols (NPs) were also present. Significant induction of hepatic CYP1A protein compared with controls (P<0.05) was observed in both low (0.5 g l(-1)) and high (2.5 g l(-1)) exposed fish from Day 7. CYP1A levels peaked at Day 21 with 21-fold and 8-fold inductions over controls in high and low dose fish respectively. Induction of DNA damage in hepatocytes (single strand breaks as measured using the COMET assay) was observed in both exposures compared with controls on Days 14 and 28 (P<0.05). A significant correlation was found between CYP1A induction and DNA damage (Pearson correlation index, P<0.05). It is plausible that activation of PAHs may be responsible for the induction of CYP1A and resulting increase in DNA damage. Our data show the potential for detrimental effects in the event of exposure of aquatic organisms to biosolids and the need for further investigations of possible impacts due to constituents not covered by current guidelines.     

Comparison of chlorine and chlorine dioxide toxicity to fathead minnows and bluegill

The comparative toxicity of total residual chlorine (TRC) and chlorine dioxide (ClO₂) was evaluated by conducting 96 h flow-through bioassays with three types of fish. The fish were subjected to an intermittent exposure regime in which biocide residuals were present for approx. 2-h periods beginning at 0, 24, 48 and 72 h into the tests. These conditions simulated the antifouling procedure (1 h day⁻¹ biocide addition) used to control biofouling of nuclear reactor heat exchangers at the Savannah River Plant near Aiken, South Carolina. LC₅₀ values showed that ClO₂ was approx. 2–4 times more toxic than TRC to: (1) juvenile and 1-year-old fathead minnows (Pimphales promelas); and (2) young-of-the-year bluegill (Lepomis macrochirus).The TRC mean 96-h LC₅₀ values were: 0.08 mg l⁻¹ for juvenile fathead minnows, 0.35 mg l⁻¹ for adult fathead minnows and 0.44 mg l⁻¹ for young-of-the-year bluegills. The ClO₂ mean LC₅₀ values were: 0.02 mg l⁻¹ for juvenile fathead minnows, 0.17 mg l⁻¹ for adult fathead minnows and 0.15 mg l⁻¹ for young-of-the-year bluegills.     

The toxicity of copper to crucian carp (Carassius carassius) in soft water

Crucian carp (Carassius carassius) were exposed to a Cu rich medium (pH 6.6, conductivity 25 microS/cm, 2.91 mg Ca(2+)/l, approximately 300 microg Cu(2+)/l). Untreated department water (pH 6.6, conductivity 25 microS/cm, 2.91 mg Ca(2+)/l) acted as control. Mortality in crucian carp was first observed after 13 days of exposure to the Cu rich medium. There were, however, significant changes in haematocrit, plasma chloride, plasma sodium and water content in muscle in fish exposed to the Cu rich medium after two days. After 14 days of exposure to copper, haematocrit increased to 52+/-2% (control: between 37 and 40%), plasma chloride decreased to 45+/-5 mmol/l (control: 99-106 mmol/l), plasma sodium decreased to 81+/-6 mmol/l (control: 116-137 mmol/l), and water content in muscle increased to 83.0+/-0.3% (control: 78.7-79.9%). No apparent changes in blood ethanol, and minor changes in plasma lactate were observed in copper exposed fish. Analyses of the gills revealed an increasing concentration of copper on the gills from fish exposed to Cu rich water. After 14 days, the concentration of copper accumulated in the gill was 12.8+/-4.1 microg Cu/g wet weight (control: 0.91-1.19 microg Cu/g wet weight). A reduction of the respiratory area in fish exposed to copper was observed, in terms of both lamellar and filamental fusion. The normoxic O(2) uptake did not change, but the critical oxygen tension was elevated to 6.12+/-1.04 mg O(2)/l after a 6 day exposure to copper (control: 1.03+/-0.05 mg O(2)/l). This study shows that crucian carp has a higher tolerance to copper compared to other freshwater fish species. Our results suggest that this tolerance is based on the ability of crucian carp to avoid becoming hypoxic as well as an extreme tolerance to severe loss of plasma ions.     

Estimating the effect of water quality on surface water supplies

River quality models derived by regression analysis are often quick and cheap to produce. They can be used as a basis for forecasting river quality and to calculate the effects of water quality constraints on the operation of water supplies drawn from rivers and impoundments. Results for nitrate show that to operate intakes according to river quality is a poor method of controlling quality in impoundments.     

Assessment of the surface water quality in Northern Greece

The application of different multivariate statistical approaches for the interpretation of a large and complex data matrix obtained during a monitoring program of surface waters in Northern Greece is presented in this study. The dataset consists of analytical results from a 3-yr survey conducted in the major river systems (Aliakmon, Axios, Gallikos, Loudias and Strymon) as well as streams, tributaries and ditches. Twenty-seven parameters have been monitored on 25 key sampling sites on monthly basis (total of 22,350 observations). The dataset was treated using cluster analysis (CA), principal component analysis and multiple regression analysis on principal components. CA showed four different groups of similarity between the sampling sites reflecting the different physicochemical characteristics and pollution levels of the studied water systems. Six latent factors were identified as responsible for the data structure explaining 90% of the total variance of the dataset and are conditionally named organic, nutrient, physicochemical, weathering, soil-leaching and toxic-anthropogenic factors. A multivariate receptor model was also applied for source apportionment estimating the contribution of identified sources to the concentration of the physicochemical parameters. This study presents the necessity and usefulness of multivariate statistical assessment of large and complex databases in order to get better information about the quality of surface water, the design of sampling and analytical protocols and the effective pollution control/management of the surface waters.     

Assessment of seasonal variations in surface water quality

Assessment of seasonal changes in surface water quality is an important aspect for evaluating temporal variations of river pollution due to natural or anthropogenic inputs of point and non-point sources. In this study, surface water quality data for 16 physical and chemical parameters collected from 22 monitoring stations in a river during the years from 1998 to 2001 were analyzed. The principal component analysis technique was employed to evaluate the seasonal correlations of water quality parameters, while the principal factor analysis technique was used to extract the parameters that are most important in assessing seasonal variations of river water quality. Analysis shows that a parameter that is most important in contributing to water quality variation for one season may not be important for another season except for DOC and electrical conductance, which were always the most important parameters in contributing to water quality variations for all four seasons.     

城市水环境与水质的演化及调控

截至8月2日,内蒙古赤峰市新城区自来水受污染事件已致4322人就医,治愈近4000人。赤峰自来水污染事件,不是第一起,也不会是最后一起。赤峰只是饮水安全受害城市中的一个,在它之前,已经有哈尔滨、无锡、盐城等。这些城市遭受水污染的原因虽然不同,但城市水质安全问题已经向我们敲响了警钟。为此,本期"水科技"栏目就城市水质安全及监测,提出了一些问题与建议,供业内人士借鉴参考。     

我国研究生招考制度改革与发展趋势研究——以中国科学技术大学为例

梳理我国研究生招生考试制度的历史沿革,分析招考制度改革的政策背景,结合中国科学技术大学四十年研究生招生工作的实践与创新经验,预测我国未来研究生招考制度将呈现招生与考试更深层次的分离,招考形式更加多元化,导师自主权进一步扩大,创新能力与综合素质强的考生将更受亲睐的趋势。     

The toxic effects of trinitrotoluene (TNT) and its primary degradation products on two species of algae and the fathead minnow

The effects of alpha trinitrotoluene (alpha TNT) and its primary degradation product (TNTcc), commonly referred to as “pink water”, were determined on members of two trophic levels. The growth responses of the algae Selenastrum capricornutum and Microcystis aeruginosa were examined through static bioassays. Death and behavioral responses of the fathead minnow (Pimephales promelas) were determined using a proportional diluter. Alpha TNT and TNTcc were both more toxic to the fathead minnow than to either species of alga. Five and 15 mg l⁻¹ alpha TNT inhibited S. capricornutum and M. aeruginosa growth, respectively. TNTcc inhibited S. capricornutum growth at concentrations above 9 mg l⁻¹; it was lethal to M. aeruginosa at 50 mg l⁻¹, but stimulated growth at lower concentrations. The 96-h lc₅₀ values based on the death response of the fathead minnow to alpha TNT and TNTcc were 2.58 and 1.60 mg l⁻¹, respectively. The 96-h ec₅₀ values based on the behavioral responses were 0.46 and 0.64 mg l⁻¹, respectively. There was no response to concentrations of 0.05 mg l⁻¹ alpha TNT and 0.07 mg l⁻¹ TNTcc.