Circulation of copper in the biotic compartments of a freshwater dammed reservoir

This study concerns a chronic copper release in an aquatic ecosystem: Mirgenbach reservoir; which is characterized by high salinity, conductivity and hardness, a eutrophic state and a high temperature. To study the bioavailability of copper in the biotic compartments, the sampling covered the entire food chain (phyto- and zooplankton, macroalgae, aquatic plants, crustaceans, mollusks, and fish). Of the organisms present, the filter feeder Dreissena polymorpha, the detritivorous Bithynia tentaculata and Orconectes limosus were most contaminated by copper. The level of copper found in fish was the lowest. Body copper concentrations recorded in the present study show large variability between species even in some that are closely related. In most cases, however, the metal handling strategy, feeding habits, morphology and ecology can, at least partially, explain the metal content recorded. Pollution factors have been used to assess the state of contamination of the food chain. This study showed finally that the copper in the lake is bioavailable and bioaccumulated by organisms up to high levels and some effects of long-term toxicity of copper on benthic community and planktonic biomass were pointed out.     

Spatial and temporal trends of metals and arsenic in German freshwater compartments

Cadmium, lead, mercury, copper, nickel, zinc, and arsenic were analyzed in suspended particulate matter (SPM), zebra mussels, and bream sampled yearly under the program of the German Environmental Specimen Bank (ESB) in the rivers Rhine, Elbe, Danube, Saar, Mulde, and Saale and in Lake Belau. Temporal and spatial trends were analyzed, correlations between metal levels in different specimen types assessed, and sampling sites ranked according to their metal levels by calculating a Multi-Metal Index (MMI) for every specimen type and site. SPM: Highest metal loads were detected in Mulde, Saale, and Elbe right downstream of the Saale confluence. In the Elbe, metal loads in SPM were mostly highest in the upper and middle section of the river while in Rhine and Saar concentrations increased downstream. Temporal trends since 2005 were detected only at three sites. Zebra mussel: MMIs were highest in the tidal section of the Elbe and the lower Rhine and lowest in Lake Belau and the upper Danube. Different temporal trends were detected since the early 1990s depending on site and metal. Bream: As, Pb, Cu, and Hg were analyzed in muscle tissue and Pb, Cd, Cu, and Zn in liver. For both tissues, MMIs were highest in Mulde and Saale and the lower and middle Elbe. Since the early 1990s, Hg, Pb, and Cu decreased in bream muscle at many sites while As increased at 6 of the 17 sites. The findings indicate that Hg, Pb, and Cu have obviously decreased in many freshwater ecosystems in recent years, whereas As and Ni levels have increased at several sites. Metal levels and temporal trends mostly differed between the specimen types under investigation and only few correlations between specimen types were detected. This underlines the importance of including different components of an ecosystem when assessing its environmental quality.     

Evaluation of copper effects upon Girardia tigrina freshwater planarians based on a set of biomarkers

Copper is a common environmental contaminant, which is particularly toxic to living organisms when in high concentrations. To monitor environmental contamination by Cu2+ and other heavy metals, well characterized bioindicator organisms and standardized assays are needed. As a first step toward this end, we have analysed Cu2+ effects upon Girardia tigrina freshwater planarians, based on the assessment of mobility, regeneration performance, micronucleus (MN) frequency in regenerating animals, and reproductive performance. These four biomarkers provided complementary information on Cu2+ toxicity, teratogenicity, mutagenicity and chronic (>96 h of exposure) effects, respectively. The LC50 was calculated for newborn, adult and regenerating planarians, and values of 12+/-0.02 mg l(-1), 42+/-0.08 mg l(-1), 48+/-0.13 mg l(-1), respectively, were obtained after 96 h of exposure. Mobility, for intact adults, and time of regeneration and MN frequency, for regenerating animals, were significantly affected by Cu2+ concentrations as low as 0.10 mg l(-1). MN assay for regenerating G. tigrina neoblasts showed higher sensitivities than MN assays performed with other bioindicator freshwater organisms, such as moluscs or fish. Chronic exposure effects were clearly evidenced by assessment of reproductive performance, with significant reduction in fecundity and fertility rates upon exposure to Cu2+ concentrations as low as 0.05 mg l(-1). Therefore, G. tigrina can be regarded as a useful bioindicator species for the detection and evaluation of Cu2+ effects upon freshwater invertebrates, allowing insights on the effects of Cu2+ (and possibly other heavy metals) in a freshwater environment.     

Modelling the phytoplankton dynamics in a nutrient-rich solar saltern pond: predicting the impact of restoration and climate change

An ecological model for the solar saltern of Sfax (Tunisia) was established and validated by comparing simulation results to observed data relative to horizontal distributions of temperature, nutrients and phytoplankton biomass. Sensitivity analysis was performed in order to assess the influence of the main ecological model parameters. First applied at the saltern’s pond A1, the model was calibrated with field data measured over 4 years of study (from 2000 to 2003), which allowed an evaluation of parameters such as maximum growth rate of phytoplankton, optimal growth temperature and constant of half saturation for P/N assimilation by phytoplankton. Simulation results showed that the model allowed us to predict realistic phytoplankton variations of the study area, though we were unable to accurately reproduce the nutrient variation. The model was then applied to simulations of the impact of changes in phytoplankton biomass through scenarios such as hypothetic climate changes and saltern restoration.     

Response of plankton communities in freshwater pond and stream mesocosms to the herbicide metazachlor

Metazachlor is a frequently used herbicide with concentrations in surface waters up to 100 microg L(-1). A long-term mesocosm study was performed in order to investigate effects on stream and pond communities also regarding recovery. Single metazachlor doses of 5, 20, 80, 200, and 500 microg L(-1) were given and the aquatic communities monitored for 140 days. In this paper, special attention is paid to the plankton response and the results of the entire study are summarised. Metazachlor strongly affected the stream and pond mesocosm communities at concentrations higher than 5 microg L(-1). Direct negative effects were most prominent for chlorophytes whereas diatoms and cryptophytes seemed insensitive. The effects on zooplankton were caused by changes in habitat structure due to the strong decline of macrophytes. The slow degradation of metazachlor combined with the absence of recovery in both chlorophytes and macrophytes is likely to cause long-lasting effects on aquatic ecosystems.     

Effects of zinc on the structure and growth dynamics of a natural freshwater phytoplankton assemblage reared in the laboratory

The response of a natural phytoplankton assemblage to different concentrations of Zn(2+) was evaluated by means of a static laboratory bioassay. Aliquots of surface water, taken in autumn from a non-polluted point of the Reconquista River (Buenos Aires, Argentia), were incubated in mineral nutrient media containing 2.5, 10 or 25 mg litre(-1) of Zn(2+) (as zinc chloride). The comparative structure and dynamics of the communities were followed through periodic physico-chemical and biological analyses of samples taken during 24 days of incubation. Under the experimental conditions of the bioassays, the existence of several Zn(2+) tolerant algal species was shown: the most important of them were Chlorella vulgaris Beij. (Chlorophyceae, Chlorococcales), Nitzschia palea (Kütz.) Smith and Gomphonema parvulum (Kütz.) Kütz. (Bacillariophyceae). It was also demonstrated that the algal responses to Zn(2+) were selectively concentration dependent: at 2.5 and 10 mg litre(-1) a stimulatory effect was observed in the diatoms; at 25 mg litre(-1), diatom toxicity occurred. In contrast, Chlorophyceae growth was stimulated at the maximal Zn level. In general, the diversity, richness and equitability of the community were adversely affected by Zn in a concentration-dependent fashion.     

Atrazine effects on in vitro maturation and in vitro fertilization in the bovine oocyte

The effect of low levels of atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) on in vitro oocyte maturation, in vitro capacitation of sperm, or in vitro fertilization of bovine oocytes and on the quality of blastocyst formation was studied. Bovine oocytes collected from abattoir ovaries were matured, fertilized, and developed to the blastocyst stage in vitro. Embryos that reached a morula or blastocyst stage were stained with Hoechst 33258 stain to determine the number of blastomeres per embryo. Three bulls whose fertilization rates were proven consistent among straws were used for this study. Atrazine was tested at concentrations of 0.01, 0.1, 1, and 10 microM in either the maturation medium, sperm capacitation medium, or the fertilization medium. Because atrazine was dissolved in ethanol, an ethanol control was used to determine any possible effects of ethanol on the in vitro process. The addition of atrazine to both the maturation and fertilization media did not result in any significant difference in fertilization rates between the controls and the treatments. In the capacitation medium, a significant difference between the controls and the atrazine levels of 0.1, 1, and 10 microM was noted for one bull. Atrazine did not affect the number of blastomeres per embryo. There was not a significant difference (p>0.05) in the number of blastomeres per embryo between the controls and the different levels of atrazine in each medium. This study indicates that low levels of atrazine do not have an effect on in vitro fertilization rates or the number of blastomeres per embryo produced in vitro.     

Polychlorinated dibenzo-p-dioxins and dibenzofurans in commercial diphenyl ether herbicides,and in freshwater fish collected from the application area

This paper describes the analyses of polychlorinated dibenzodioxins, dibenzofurans, and related compounds in diphenyl ether herbicides, CNP, NIP, and X-52. The levels of tetra-, penta-CDDs, and tetra-CDFs were about 150, 30, and 15 ppm, respectively in CNP formulations. NIP and X-52 contained lower chlorine alalogs. Isomer distribution of PCDDs in CNP agreed with an estimate from the reaction of chlorophenols. Freshwater fish samples heavily contaminated with CNP in the application season also contained 0.2 ppb of 1,3,6,8-tetra-CDD.     

The dissipation of nonlyphenol in stream and pond water under simulated field conditions

Abstract

The dissipation of 1.0 ppm nonylphenol in stream and pond water, incubated in flasks at 16°C under simulated field conditions up to 44 days indicated that the half‐life was 2.5 days if the flasks were open, and 16 days if they were closed. A transformed product was detected in the closed flasks.

Translocation of nonylphenol in water occurred when treated water samples were incubated in the presence of sediment. After 10 days, nonylphenol was detected only in the sediment, but not in water (detection limit = 10 ppb). About 80% of the nonylphenol was degraded in 71 days, but no degradation occurred if the water and the sediment were autoclaved prior to incubation.     

Effects of propanil, tebufenozide and mefenacet on growth of four freshwater species of phytoplankton: a microplate bioassay

The Albufera Natural Park situated in Valencia (Spain), with a very rich flora and fauna is surrounded by rice fields in which pesticide spraying is a regular practice. With this in mind, the sensitivity of four algal species, Scenedesmus acutus, Scenedesmus subspicatus, Chlorella vulgaris and Chlorella saccharophila to pesticides propanil, tebufenozide and mefenacet was studied using single species toxicity tests. Organisms were exposed to different concentrations of these herbicides and the algal growth was measured in a microplate reader at 410 nm, at 0, 24, 48 and 72 h. Tebufenozide appeared to be the most inhibitory to Scenedesmus and Chlorella species growth. 72 h EC50 of propanil, tebufenozide and mefenacet ranged from 0.29 to 5.98 mg/l, 0.12 to 0.15 mg/l and from 0.25 to 0.67 mg/l, respectively for the four algal species. The two species of Chlorella were more tolerant than the two species of Scenedesmus.     

Differential effects of the herbicides bensulfuron and cinosulfuron on soil microorganisms.

Bensulfuron toxicity on soil microbes was evaluated by the methods used in a previous study on cinosulfuron; the effects of the two sulfonylureas were compared. Cinosulfuron and bensulfuron, at the normal field application rate and 100 times higher, had no effect on the total number of bacteria and nitrifiers, or on the respiration activity in the soil, but they did decrease the nitrification activity. In vitro toxicity tests carried out on representative soil microbial strains using bensulfuron at 50 mg l(-1) showed some inhibition of three of the 17 bacterial strains and strong inhibition of almost all the 12 fungal strains; cinosulfuron had had no effect on any of these strains in the previous study. It is concluded that, compared with cinosulfuron, bensulfuron is potentially more toxic on soil heterotrophic microorganisms, but only at very high concentrations that are nearly impossible to reach with the usual agricultural use of the herbicides. However, autotrophic nitrifiers were more sensitive to both sulfonylureas than the other microorganisms.     

Influence of sugar cane vinasse on the sorption and degradation of herbicides in soil under controlled conditions

This study reports the influence of sugar cane vinasse on the persistence, sorption and leaching potential of diuron (3-(3,4-dichlorophenyl)-1,1-dimethylurea), hexazinone (3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4-dione) and tebuthiuron (1-(5-tert-butyl-1,3,4-thiadiazol-2-yl)-1,3-dimethylurea) in both a clay and sandy soil from a tropical area of Brazil. The experiments were conducted out under controlled laboratory conditions. The addition of sugarcane vinasse to soil influenced the persistence and sorption of the herbicides in both the studied clay and sandy soils, with a considerable decrease in the diuron DT(50) values in clay soil. The Ground Water Ubiquity Score (GUS) Index classifies the herbicides as leachers in both soils and treatments, with the exception of diuron, which is classified as a non-leacher in clay soil-vinasse and as a transient herbicide in sandy soil. These results suggest that special attention should be given to areas such as those where the sandy soil was collected in this study, which is a recharge area of the Guarani Aquifer and is likely to experience groundwater contamination due to the high leaching potential of the applied pesticides.     

Influence of sugar cane vinasse on the sorption and degradation of herbicides in soil under controlled conditions

This study reports the influence of sugar cane vinasse on the persistence, sorption and leaching potential of diuron (3-(3,4-dichlorophenyl)-1,1-dimethylurea), hexazinone (3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4-dione) and tebuthiuron (1-(5-tert-butyl-1,3,4-thiadiazol-2-yl)-1,3-dimethylurea) in both a clay and sandy soil from a tropical area of Brazil. The experiments were conducted out under controlled laboratory conditions. The addition of sugarcane vinasse to soil influenced the persistence and sorption of the herbicides in both the studied clay and sandy soils, with a considerable decrease in the diuron DT₅₀ values in clay soil. The Ground Water Ubiquity Score (GUS) Index classifies the herbicides as leachers in both soils and treatments, with the exception of diuron, which is classified as a non-leacher in clay soil-vinasse and as a transient herbicide in sandy soil. These results suggest that special attention should be given to areas such as those where the sandy soil was collected in this study, which is a recharge area of the Guarani Aquifer and is likely to experience groundwater contamination due to the high leaching potential of the applied pesticides.     

CeO2 nanoparticle fate in environmental conditions and toxicity on a freshwater predator species: a microcosm study

Environmental Science and Pollution Research - We studied the fate and toxicity of two types of CeO2 NPs (bare or citrate-coated) in environmentally relevant conditions, using large indoor...     

曝气时长对中试曝气塘-浮萍塘联合系统中污染物去除的影响

浮萍塘污水处理技术具有管理简便、运行成本低、可资源化回收氮磷污染物等优势。然而,因水体溶解氧(DO)不足造成的污染物去除率低的问题限制了该技术的推广应用。为此,本研究在浮萍塘前端引入曝气塘,构建中试曝气塘-浮萍塘联合系统,借此增加浮萍塘DO含量,并进一步考察了曝气时长(0、0.5、1、2和4 h)对污染物去除效果及浮萍生长的影响,以此探寻低耗高效的最佳曝气时长。结果表明,曝气塘可有效降低水体的浊度,但对氮磷去除的贡献较小,氮磷的去除以浮萍塘为主。曝气处理可显著提高曝气塘及浮萍塘水体DO含量和氧化还原电位(Eh),且DO和Eh随曝气时长的增加而上升。此外,曝气处理还能显著促进浮萍生长及其污染物的去除,但促进效果并未简单地随曝气时长的增加而提高。其中,TN、氨氮和浊度的去除率在曝气时长1 h时已基本达到峰值(去除率分别为58.42%、61.89%和89.90%),TP去除率虽在曝气时长4 h时最大(81.44%),但与曝气时长0.5 h(73.05%)相比并无显著差异;浮萍虽在曝气时长2 h时干基生长速率最高(8.00 g·(m²·d)⁻¹),但与曝气时长0.5 h和1 h(7.35 g·(m²·d)⁻¹左右)相比也无显著差异,而曝气成本却成倍增加。因此,综合考虑污染物去除、浮萍生长及曝气成本,建议曝气时长不宜高于1 h,推荐0.5~1 h为佳。以上结果可为曝气塘-浮萍塘联合系统的应用及曝气时长的选择提供参考。     

Evaluation of the cytotoxic effects of glyphosate herbicides in human liver,lung, and nerve

Glyphosate-based herbicides are broad-spectrum pesticides widely used in the world, which is considered a highly safe pesticide due to their target specificity, but recently, there has been an ongoing controversy regarding their carcinogenicity and possible side effects of glyphosate on human health. Commercial glyphosate-based herbicides (GBHs) consist of declared active ingredient (glyphosate salts) and a number of formulants such as ethoxylated formulants (4130®, 3780^®, and A-178^®). The aim of our study is to investigate whether the toxicity of GBHs is related to formulants. The effects of GBHs on human health were studied at the cellular level based on their toxicity to liver, lungs and nerve tissue. The inhibitory toxicity to cell viability by GBHs was examined with cell-based systems using three human cell lines: HepG2, A549, and SH-SY5Y. Data obtained showed that all tested ethoxylated formulants and their mixtures with declared active ingredient glyphosate isopropylamine salt (GP) have significant inhibitory effect on cell proliferation, while the declared active ingredient has no significant toxicity. Our study demonstrates that the toxic effect of GBH is primarily due to the use of formulants. This result suggests that GP is relatively safe and a new approach for the assessment of toxicity should be made.     

Predicting Pb bioavailability to freshwater microalgae in the presence of fulvic acid: algal cell density as a variable

In order to better understand the relationship between lead speciation and its bioavailability in natural waters, the interactions between Pb(II), fulvic acid and the freshwater alga, Chlorella kesslerii were studied at various algal cell densities. An increase in cellular lead or fulvic acid adsorbed to algae was observed with decrease of the cell density from ca. 10(7) to 10(5)cells ml(-1). In the presence of fulvic acid, cellular Pb was greater than that expected for the same free lead ion concentrations in the absence of fulvic acid in agreement to our previous study. This effect was found to be more pronounced at lower cell density, in accordance with increased fulvic acid adsorption to algae. Good fit between experimental observations and model predictions of cellular Pb at various cell densities, was observed by assuming that fulvic acid adsorbed to algae give rise to additional binding sites for Pb(II). The findings of this study indicate that a further extension of the biotic ligand model which includes the formation of a ternary complex and cell density (or concentration) as an input parameter is needed to improve its site-specific predictive capacity, especially in the case of dissolved organic matter-rich surface waters. This extension of predictive capacity would allow to reduce the deviations from the BLM model predictions for microalgae in the presence of dissolved organic matter and hence will serve as a mechanistic tool for establishing ambient site-specific water quality criteria.     

An experimental comparison of the effects of two chemical stressors on a freshwater zooplankton assemblage

Mesocosms in an Ohio, USA lake were dosed with ten levels (0-100 microg liter(-1)) of copper (experiment 1) or Carbaryl (experiment 2). Zooplankton responses were determined after 4-day incubations. Species level responses differed for the two chemicals; community level responses were very similar. Across the gradients of increasing Cu or Carbaryl doses, cladocerans were greatly reduced and copepods became dominant. For Carbaryl, the response was consistent with that reported previously. For Cu, different responses were previously observed at other lakes. The taxonomic composition of the zooplankton may largely determine the community level response. In the present experiments, cladoceran declines may have secondarily affected food web function. In the Carbaryl experiment, where the chemical did not directly suppress algae, their biomass increased with dose level. This coincided with the cladoceran decline, suggesting an algal response to reduced top-down control.     

Relationship between water solubility of chlorobenzenes and their effects on a freshwater green alga

The effective concentrations of benzene and 12 chlorobenzenes that reduced 50% of the primary productivity (EC₅₀) of a freshwater green alga, $\text{Ankistrodesmus falcatus}$, were determined. Benzene was the least toxic chemical and the toxicity increased as the degree of chlorine substitution in the aromatic ring increased. No EC₅₀ value could be obtained for HCB. A quantitative relationship was found to exist between water solubility, lipophilicity and the EC₅₀. A good correlation was also observed between the EC₅₀ for this alga and other toxicity data for various aquatic biota.