Toxicity and removal of pesticides by selected aquatic plants

Pesticides are being detected in water bodies on an increasingly frequent basis. The present study focused on the phytoremediation potential of selected aquatic plants to remove phytosanitary products from contaminated water. We investigated the uptake capacity of Lemna minor (L. minor), Elodea canadensis (E. canadensis) and Cabomba aquatica (C. aquatica) on three pesticides: copper sulphate (fungicide), flazasulfuron (herbicide) and dimethomorph (fungicide). Pesticide toxicity was evaluated by exposing plants to five concentrations (0-1 mg L(-1)) in culture media for 7d using chlorophyll fluorescence as a biomarker. The toxicity of the contaminants was the same for all the aquatic plants studied and occurred in this descending order of toxicity: flazasulfuron>copper>dimethomorph. We found that L. minor had the most efficient uptake capacity, followed by E. canadensis and then C. aquatica. The maximum removal rate (microg g(-1)fresh weight d(-1)) of copper, flazasulfuron and dimethomorph was 30, 27 and 11, respectively.     

Phyto-remediation potential of Ipomoea aquatica for Cr(VI) mitigation

Phyto-remedial efficiency of Ipomoea aquatica was examined at different experimental conditions for a period of 3 months. This plant was selected due to its easy establishment, tolerance and growing easiness. In all trials, the I. aquatica was grown in coir dust to ensure an inert medium. Essential growth nutrients were supplied externally using Albert solution. Once plant growth conditions were fixed, the model system was spiked with Cr(VI) solution in the range of 7-90 ppm. Up to 28 ppm Cr(VI), I. aquatica exhibits uniform absorption characteristics showing over 75% removal of added Cr(VI). At this stage I. aquatica was not affected and it showed no toxicity symptoms. Therefore, it is suited as a potential phyto-remediant. Further I. aquatica is a vegetable particularly in Asian region; therefore caution has to be taken when selecting it for human consumption due to its high chromium accumulation capacity.     

Effects of pH on the mortality and accumulation of copper in tissues of Oreochromis niloticus

In the present study, effect of pH on the mortality and accumulation of copper in various tissue and organs of Oreochromis niloticus were tested at varying concentrations of copper in the medium and over different periods of time. Experimental animals were exposed to pH 5.5, 7.8 and 9.5 and 0.1, 0.5, 1.0 and 5.0 ppm copper over periods of 7, 15 and 30 days in liver, gills and muscle were determined using atomic absorption spectrophotometric techniques. The rate of mortality at 1.0 and 5.0 ppm Cu was 100% after 7 days of exposure at pH 5.5 while at 5.0 ppm Cu was 66% after 30 days of exposure at pH 7.8. No mortality was observed in any of the copper concentrations tested at pH 9.5. In all pH levels, tissue accumulation of copper increased with increasing concentrations of copper in the medium at a given exposure period. In all pH values tested, highest levels of copper were found in the liver of O. niloticus, followed by the gills and muscle tissues. Accumulation of copper in all tissues were higher at pH 5.5 compared with the other pH values in all the conditions tested.     

Experimental effects of tributyltin (TBT) contaminated sediment on a range of meiobenthic communities

Microcosm experiments have been carried out with whole natural meiobenthic communities to look at the effects of TBT sediment contamination on the community structure of the dominant nematode component of the meiobenthos. TBT has a high affinity for aquatic sediments, yet this is the first study of the effects of this contaminant in sediment on natural benthic communities. Three communities were studied from contrasting locations in south-west England: the intertidal of the Lynher estuary (muddy sediment) and the Exe estuary (sandy sediment) and the subtidal (50m depth) at Rame Head off Plymouth (muddy sand). Fresh sediment with natural meiobenthic communities was incubated for 2 months with TBT-contaminated sediment (three dose levels) in bottles. Nematodes were identified and enumerated and subjected to multivariate data analysis. The sandy Exe estuary fauna was significantly affected by TBT-contaminated sediment at all three doses (0.3, 0.6 and 0.9 microg g(-1) dry wt (as Sn) sediment), whereas the offshore fauna from Rame Head was significantly affected only at the highest dose. The muddy Lynher estuary meiofauna was affected (somewhat peculiarly) at the medium dose level only. Meiobenthic nematodes may not be as sensitive to TBT-contaminated sediment as other infaunal benthos but exhibited responses to levels of contamination still persisting in some UK estuaries and harbours. Comparing the effects of TBT with those of copper and zinc in the same laboratory experiments, our observations suggest that the relative impact of TBT on meiobenthic community structure is not as great as these contaminants in marine sediments. Although there are very few observations of TBT toxicity in sediment, it appears that TBT is toxic at much lower concentrations in seawater (ppb) than it is in sediment (ppm).     

Long-term effects of heavy metals on aouatic plants

In long-term experiments lasting up to 73 days the effect of rather low levels of zinc, copper, lead and cadmium on the growth and metal uptake was studied by investigating four aquatic plant species: Elodea nuttallii, Callitriche plataycarpa, Spirodela polyrhiza and Lemma gibba. Except Elodea, which was already very sensitive to 5 μmol Cu 1^?1, no differentiation in growth or mortality could be detected depending on species or elements. There was a clear differentiation between the uptake levels of the heavy metals with regard to the plant species, resulting in a higher heavy metal content in de submerged species in comparison to the floating ones. For zinc, lead and cadmium, an equal ratio was detected between the concentration in the medium and in the plant tissue independent of the plant species. The involvement of roots in element absorption by aquatic plants and the possibility of using aquatic plants as indicators of heavy metal pollution in Dutch waters are discussed.     

Comparative study on the susceptibility of freshwater species to copper-based pesticides

Copper compounds have been intentionally introduced into water bodies as aquatic plant herbicides, algicides and molluscicides. Copper-based fertilizers and fungicides have been widely used in agriculture as well. Despite the fact that copper is an essential element for all biota, elevated concentrations of this metal have been shown to affect a variety of aquatic organisms. Nonetheless, comparative studies on the susceptibility of different freshwater species to copper compounds have seldom been performed. This study was conducted to compare toxicity of copper-based pesticides (copper oxychloride, cuprous oxide and copper sulfate) to different freshwater target (Raphidocelis subcapitata, a planktonic alga and Biomphalaria glabrata, a snail) and non-target (Daphnia similis, a planktonic crustacean and Danio rerio, a fish) organisms. Test water parameters were as follows: pH = 7.4 +/- 0.1; hardness 44 +/- 1 mg/l as CaCO3; DO 8-9 mg/l at the beginning and > 4 mg/l at the end; temperature, fish and snails 25 +/- 1 degrees C, Daphnia 20 +/- 2 degrees C, algae 24 +/- 1 degrees C. D. similis (immobilization), 48-h EC50s (95% CLs) ranging from 0.013 (0.011-0.016) to 0.043 (0.033-0.057) mg Cu/l, and R. subcapitata (growth inhibition), 96-h IC50s from 0.071 (0.045-0.099) to 0.137 (0.090-0.174) mg Cu/l, were the most susceptible species. B. glabrata (lethality), 48-h LC50s from 0.179 (0.102-0.270) to 0.854 (0.553-1.457) mg Cu/l, and D. rerio (lethality), 48-h LC50s 0.063 (0.045-0.089), 0.192 (0.133-0.272) and 0.714 (0.494-1.016) mg Cu/l, were less susceptible than Daphnia to copper-based pesticides. Findings from the present study therefore suggest that increased levels of copper in water bodies is likely to adversely affect a variety of aquatic species.     

Biomonitoring of air quality employing in situ Ramalina celastri in Argentina

The lichen Ramalina celastri was employed as an in situ biomonitor for the study of air quality and heavy metal distribution in the central region of the Argentine Republic. The thallus content of copper, iron, manganese, cobalt, zinc, nickel and lead was determined by atomic absorption spectrophotometry. Pigments, hydroperoxy conjugated dienes, malondialdehyde and sulfur were also measured. Some of these parameters were used to calculate a pollution index. Geographical distribution patterns were obtained for the different metals by mapping. Thus, zinc shows high levels in industrial and agricultural zones. The highest nickel values were found in urban-industrial zones located at the centre and south of the study area. The same was observed for sulfur. The pollution index distribution map showed that major physiological damage in the biomonitor was found in central and southeastern areas that coincide with Cordoba City and agricultural zones. So, the effect would seem to be related to urban activities and the use of pesticides.     

Growth,photosynthesis and removal responses of the cyanobacteria Chroococcus sp. to malathion and malaoxon

Abstract

Malathion is an organophosphorus pesticide widely used in agricultural crops, despite its toxicity. In addition, malaoxon occurs by oxidation of malathion being more toxic. The toxic effects of malathion and malaoxon in humans include hepatoxicity, breast cancer, genetic damage and endocrine disruption. The aim of this study involved assessing the effect of malathion commercial grade on Chroococcus sp., and its potential as an alternative to the removal of this pesticide and its transformation product such as malaoxon. We evaluated the effect of malathion at different concentrations (1, 25, 50, 75 and 100?ppm) on the biomass of the cyanobacteria Chroococcus sp. grown in medium BG-11; also, we analyse its ability to degrade both malathion and malaoxon into a temperature of 28?±?2?°C and at pH 6. The results showed that 50?ppm of malathion the cyanobacteria Chroococcus sp. reached the highest removal efficiency of malathion and malaoxon (69 and 65%, respectively); also, the growth rate of Chroococcus sp. increased without inhibiting the production of chlorophyll “a”, this can be explained by the hormesis phenomenon. Therefore, we consider that the cyanobacteria Chroococcus sp. may be a good candidate for bioremediation of aquatic systems contaminated with organophosphorus pesticides such as malathion and its transformation product such as malaoxon.     

Effects of prevalent freshwater chemical contaminants on in vitro growth of Escherichia coli and Klebsiella pneumoniae

Many surface and ground waters in the continental US are contaminated with a variety of chemical pollutants, which are usually present in concentrations in the ppm and ppb range. The effects of these pollutants on coliform bacteria, which are prominent members of the aquatic flora, are poorly understood. Using a microtiter plate assay, isolates of Escherichia coli (from chicken intestine and fresh water), and an isolate of Klebsiella pneumoniae (from bovine milk) were exposed to varying concentrations of common pollutants over a 24 h period. The herbicides/pesticides simazine, atrazine, and diazinon; the VOCs trichloroethene and MTBE; the estrogens estradiol and estrone; and caffeine, all failed to inhibit bacterial growth at ppm levels. Only ethylene glycol, and the herbicide 2,4-D, significantly inhibited bacterial growth compared to controls. These results suggest that the replication of coliform bacteria in fresh waters is not adversely impacted by many common pollutants.     

The combination of zinc compounds and acidic pH limits aerobic growth of a Salmonella typhimurium poultry marker strain in rich and minimal media

The objective of the present study was to examine the combined effects of zinc compounds with different acidic pH levels on the aerobic growth of a S. typhimurium poultry isolate in either rich or minimal media. When overall main effects of pH levels of medium or concentrations of Zn compounds were compared, growth rates of the S. typhimurium poultry isolate were significantly (p < 0.05) decreased by stepwise increase of pH levels of medium (pH 4, 5, 6, and 7) or concentrations (0.67, 3.35, and 6.03%) of Zn compounds (Zn acetate and Zn sulfate). In general growth rates of S. typhimurium poultry isolate appeared to be more reduced by Zn acetate than by Zn sulfate and more reduced in minimal media compared to rich media.     

A study of polonium-210 distribution aspects in the riverine ecosystem of Kaveri, Tiruchirappalli, India

Distribution of a natural radionuclide (210Po) in water, sediment and biota was quantified along a 95 km reach of the Kaveri River, India. It is observed that the soft tissues of animals concentrated a higher level of 210Po than the hard parts like shell and bone. The ranges of 210Po activity in biological samples were 2.32-10.78 Bq kg(-1) wet (aquatic weeds), 18.94-28.55 Bq kg(-1) wet (plankton), 32.51 to 46.17 Bq kg(-1) wet (snail), 57.42 to 105.78 Bq kg(-1) wet (bivalve), 12.13 to 19.10 Bq kg(-1) wet (prawn) and 1.86 to 4.17 Bq kg(-1) wet (fish). The concentration factors (CFs) for the aquatic organisms ranged from 10(3) to 10(4), indicating a high affinity of 210Po for organic moieties. The bivalve mollusc, Lamellidens marginalis, accumulated higher concentrations of 210Po, suggesting that it could serve as a biomonitor of 210Po radionuclide in riverine systems. Further, the levels of 210Po in water, sediment and biological samples from impoundments were higher than those from stations located in the open river. This may be largely due to aerial inputs of the radionuclide, accumulation of radionucliderich silt and organic matter, and increased biological production in the impounded water body.     

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.     

Impact of land use and physicochemical settings on aqueous methylmercury levels in the Mobile-Alabama River System

Mercury (Hg) concentrations above levels that could pose health risks have been measured recently in predatory fish from many aquatic systems in the southeastern region of the United States. Based on hypotheses derived from published experimental data on the aqueous geochemistry of Hg, we investigated the effect of certain natural and human-imposed conditions on in situ levels of methylmercury (MeHg) in the Mobile-Alabama River System (MARS). Water samples were collected from different types of environments, hypothesized to have contrasting levels of MeHg in the aqueous phase, and were analyzed for total-Hg (THg) and MeHg concentrations, as well as some key geochemical parameters. The results showed the following. i) Overall, total Hg concentrations in waters of the MARS are quite uniformly distributed and vary from 0.2 to 6 ng L(-1), suggesting that besides geological sources, atmospheric deposition is certainly the main source of Hg inputs in the studied system. ii) In locations with comparable THg levels, the Hg fraction present as MeHg was consistently higher in samples collected from the Coastal Plain portion of the MARS as compared to those from other geological provinces. iii) Our in situ observations confirmed conclusions derived from laboratory experiments, in that, MeHg abundance in aquatic systems correlates with sulfate (but only within a narrow range of concentrations); decreasing pH; and has no direct relationships with either nitrate or phosphate. iv) The investigation of Hg accumulation in biota at a single site showed that an aquatic system with low THg concentrations but a high MeHg:THg ratios, could have organisms with Hg content above safe levels. Therefore, potential health risks to fish eating populations can exist even when the aqueous phase does not show signs of significant Hg enrichment.     

Copper-induced response of physiological parameters and antioxidant enzymes in the aquatic macrophyte Potamogeton pusillus

Bioaccumulation and toxicity of copper was evaluated on Potamogeton pusillus L. The effect of copper (5–100 μg L^?1) applied for several days was assessed by measuring changes in the chlorophyll's, phaeophytin's, malondialdehyde, electrical conductivity, glutathione peroxidase (GPX), glutathione reductase (GR) and guaiacol peroxidase (POD) activities. Plants accumulated copper with a maximum of 162 μg g^?1 dw after 7-days exposure at 100 μg L^?1, however most of the metal was accumulated after 1-day exposure. The toxic effect caused by Cu was evident by the reduction of photosynthetic pigments, increase of malondialdehyde and electrical conductivity. P. pusillus shows Cu-induced oxidative stress by modulating antioxidant enzymes like GPX, GR and POD. Antioxidant enzymes activity increased significantly after exposure to 40 μg L^?1 during 24 h, followed by a drop at longer times. Thus, P. pusillus is proposed as a good biomonitor for the assessment of metal pollution in aquatic ecosystems.     

The Combination of Zinc Compounds and Acidic pH Limits Aerobic Growth of a Salmonella typhimurium Poultry Marker Strain in Rich and Minimal Media

Abstract

The objective of the present study was to examine the combined effects of zinc compounds with different acidic pH levels on the aerobic growth of a S. typhimurium poultry isolate in either rich or minimal media. When overall main effects of pH levels of medium or concentrations of Zn compounds were compared, growth rates of the S. typhimurium poultry isolate were significantly ( p < 0.05) decreased by stepwise increase of pH levels of medium (pH 4, 5, 6, and 7) or concentrations (0.67, 3.35, and 6.03%) of Zn compounds (Zn acetate and Zn sulfate). In general growth rates of S. typhimurium poultry isolate appeared to be more reduced by Zn acetate than by Zn sulfate and more reduced in minimal media compared to rich media.     

Antioxidant and biotransformation enzymes in Myriophyllum quitense as biomarkers of heavy metal exposure and eutrophication in Suquía River basin (Córdoba, Argentina)

We report the evaluation of changes in water quality, increasing pollution level, of a section of Suquía River basin (Córdoba, Argentina) by using Myriophyllum quitense as bioindicator in addition to the measurement of chemical parameters, combined with chemometrics (ANOVA, Cluster and Discriminant Analysis). Myriophyllum quitense was collected upstream from Córdoba city at an unpolluted site of Suquía River basin. After collection plants were transplanted to different sites with different pollution levels. Subsequent to transplantation plants were weekly collected from the original site as well as from transplantation stations. Water quality was evaluated throughout the transplantation experiment, while the use of this macrophyte as bioindicator was verified through the activation of its antioxidant defenses and biotransformation system. Myriophyllum quitense reacts to the pollution stress increasing the activity of glutathione-S-transferases (CDNB and Fluorodifen), glutathione reductase (GR) and peroxidase (POD). Elevated enzyme activities agreed to different pollution levels, especially inorganic nitrogen loads combined with elevated lead and aluminum concentrations, all of them originated by anthropogenic activities, thus presenting Myriophyllum quitense as a good biomonitor for assessment of water quality in this polluted aquatic ecosystem.     

Effect of fertilizer on the growth of radish plants exposed to simulated acidic rain containing different sulfate to nitrate ratios

Two successive experiments were performed in the greenhouse to test the hypothesis that plant response to the amounts and ratios of sulfuric and nitric acids in rain is affected by the amount of fertilizer added to the growing medium. Radish plants, grown with different levels of N?P?K fertilizer, were given ten 1-h exposures over a 3-week period to simulate acidic rain at pH values from 2.6 to 5.0 and sulfate to nitrate mass ratios from 0.3 to 7.5. Increased acidity of simulated rain reduced plant growth, with a greater depression of hypocotyl mass than shoot mass. The reverse growth response occurred with increased supply of fertilizer: plant biomass rose with a larger increase in shoot mass than hypocotyl mass. In one experiment, plants that received a greater supply of fertilizer exhibited more obvious reductions in growth of hoots at the higher levels of acidity of simulated rain. There were no significant effects of sulfate to nitrate ratios in simulated rain on plant growth, nor any effect of this ratio on the response of shoots and hypocotyls to acidity of simulated rain. Addition of fertilizer had no effect on plant response to sulfate to nitrate ratios. These results do not support the hypothesis that nutrient-deficient plants are either more or less responsive to sulfate and nitrate in rain than plants grown with optimal supplies of nutrients. They support previous results indicating no effects of sulfate to nitrate ratio in simulated acidic rain on plant growth. The results also suggest that the greatest risk of harmful effects on vegetation may come from the combination of high sulfate and high acidity in rainfall.     

Effect of 17beta-estradiol on the reproduction of Japanese medaka (Oryzias latipes)

Estrogenic compounds such as 17beta-estradiol (E2) and its analogs are present in the aquatic environment and can adversely affect the reproductive systems of aquatic organisms. Although E2 has been detected at a maximum concentration of 64 ng/l in effluents of sewage treatment works (STWs), few reports address the associated effects on reproduction in fish. Therefore, we exposed adult medaka (Oryzias latipes) to mean measured E2 concentrations of 29.3, 55.7, 116, 227, and 463 ng/l for 21 d and assessed the effects on the egg number and fertility of paired medaka during the exposure period. In addition, we determined the hepatic vitellogenin (Vtg) concentration and histologically assessed the gonads of these fish. The number of egg produced and fertility of the paired medaka exposed to 463 ng/l E2 were significantly less compared with those of the control fish. Males in all treatment groups had developed testis-ova. Males treated with E2 concentrations = 55.7 ng/l contained relating great concentrations of hepatic Vtg. Therefore, although only the greatest E2 concentration tested in our study affected fecundity and fertility, effects of E2 were observed on induction of Vtg and testis-ova in male medaka exposed to environmentally relevant concentrations of E2.     

Uptake, tissue distribution and metabolism of the insecticide endosulfan in Jenynsia multidentata (Anablepidae, Cyprinodontiformes)

The study reports the accumulation, distribution and metabolism of technical endosulfan in Jenynsia multidentata. Adult females were exposed to acute sublethal concentrations (0.072, 0.288 and 1.4 μg L⁻¹). After 24 h, fish were sacrificed and gills, liver, brain, intestine and muscle were removed. Results show that both isomers of technical-grade endosulfan (α- and β-) are accumulated in fish tissues and biotransformation to endosulfan sulfate occurs at all concentrations tested. Significantly differences in endosulfan accumulation were only found at 1.4 μg L⁻¹ but not between the lowest concentrations. However a similar distribution pattern was observed at all exposure levels where liver, intestine and brain had the highest levels of α-, β-endosulfan and endosulfan sulfate. Moreover, liver and brain showed the highest endosulfan sulfate:α-endosulfan ratios due to high biotransfomation capacity. J. multidentata demonstrated to be a sensitive species under exposure to technical endosulfan and, therefore, could be used to assess aquatic pollution.     

Control of bacterial growth in water using synthesized inorganic disinfectant

Chlorine is a popular method for controlling bacterial growth in cooling towers. However, there are several drawbacks such as the difficulties in maintaining the disinfection efficacy particularly at high temperature and pH. In order to overcome these difficulties, an inorganic disinfectant based on silver and copper, which is called EEKO-BALL (commercial name), was recently developed. EEKO-BALL is made from specific ceramics and coating materials. This study was performed to evaluate the efficacy of EEKO-BALL and compare it with that of silver (Ag+) and copper (Cu2+) ions. In addition, a field study was undertaken to investigate the control of bacterial growth in several cooling tower systems. The results showed that the contact time required for inactivating 99% of E. coli was 15 min in the EEKO-BALL stock solution at 25 degrees C, pH 7.3, with 0.05 mgl(-1) Ag and 0.05 mgl(-1) Cu. EEKO-BALL was approximately four times more effective than silver and copper ions in inactivating E. coli at 25 degrees C, pH 7.3. The control of bacterial growth in the cooling towers was found to be effective, lasting more than two months after a one-time installation of the EEKO-BALL. Overall, this study suggests that EEKO-BALL can effectively work as an inorganic disinfectant for bacterial growth control.