Bioconcentration and depuration of endosulfan sulfate in mosquito fish (Gambusia affinis)

Endosulfan is an insecticide which has been widely used in agriculture. The technical grade material consists of two isomers (alpha and beta). Under natural environmental conditions, endosulfan is metabolized through oxidation and the main metabolite in the environment is endosulfan sulfate. Most ecotoxicology research has been conducted with technical grade endosulfan to determine effects on non-target aquatic organisms. Little data on the effects of endosulfan sulfate on aquatic organisms are available in the literature. This study characterizes endosulfan sulfate bioconcentration and depuration in mosquito fish (Gambusia affinis). During the study, G. affinis was exposed to an environmentally relevant endosulfan sulfate concentration of 0.25 μg L⁻¹ for 5 weeks (uptake phase) followed by a 3-week period (depuration phase) in clean water. This study found that G. affinis bioconcentrated endosulfan sulfate. During the exposure phase, fish tissue concentrations of endosulfan sulfate increased with time up to 730 μg kg⁻¹ dw or 215 μg kg⁻¹ ww. The bioconcentration data followed Michaelis-Menten kinetics better than the one-compartment first order kinetics (1-CFOK). Using these models, the bioconcentration factors for endosulfan sulfate-exposed G. affinis were from 687 to 888  L kg⁻¹ in wet weight or 2263 to 2936 L kg⁻¹ in dry weight. During the depuration phase, endosulfan sulfate concentrations in tissue significantly decreased and the data followed first order kinetics. The half-life of endosulfan sulfate in G. affinis was about 9 d. There was no significant difference in standard length or weight between control and exposed fish. The growth data followed the von Bertalanffy growth model. However, the condition factor of exposed fish increased with time during the exposure phase.     

Fathead minnow (Pimephales promelas) embryo to adult exposure to decamethylcyclopentasiloxane (D5)

The cyclic siloxane decamethylcyclopentasiloxane (D5) is a high production volume chemical which has recently been assessed under the Canadian Chemicals Management Plan (CMP). Cyclic volatile methyl siloxanes (cVMS) are one of the challenge substances in the CMP batches. To provide toxicity and growth information on a species of relevance to the Canadian environment, we assessed D5 in a fathead minnow (Pimephales promelas) embryo to young adult assay. The test was 65 d in length, and exposed fathead minnow eggs to juveniles until near maturity (60 d post-hatch). The D5 concentrations in flow-through fish exposure aquaria were about one-third of nominal D5 concentrations. Fathead minnows were exposed to 0.25, 0.82, 1.7, 3.6, and 8.7 μg L⁻¹ D5. During the exposure of fathead minnows to D5 there were few effects seen. Egg hatching and larval fish survival and growth were normal. Juvenile fish survival and growth were good in all environmentally-relevant concentrations of D5, and were similar to control fish. The two highest D5 concentrations (8.7 μg L⁻¹ and 3.6 μg L⁻¹, mean measured D5) increased the condition factors of fathead minnows compared to water control and DMSO control fish. Although there were few effects of D5 in our fathead minnow study, the compound was taken up and stored in fish bodies over the 65-d exposure. The bioconcentration factor for D5 in fathead minnows was 4450, for the lowest environmentally-relevant D5 exposure water concentrations, and 4920 for all D5 exposure concentrations tested.     

Determination of the dietary biomagnification of octamethylcyclotetrasiloxane and decamethylcyclopentasiloxane with the rainbow trout (Oncorhynchus mykiss)

Separate 77-d fish feeding studies were conducted on the cyclic volatile methylsiloxane (cVMS) chemicals octamethylcyclotetrasiloxane and decamethylcyclopentasiloxane with the rainbow trout, Oncorhynchus mykiss, with the determination of biomagnification factor (BMF) and lipid-adjusted BMF (BMF(L)) values as the final experimental metrics. The studies used fish food concentrations of ∼500 μg g⁻¹ for exposure periods of 35 d, followed by a depuration period of 42 d with clean food. The fish tissue concentrations of D4 and D5 achieved empirical steady-state by day 21 in each study. By day 7 of exposure, total ¹⁴C activity of both compounds had moved from the fish gastrointestinal (GI) tract into surrounding tissue. An absence of significant fish growth during the initial depuration phase allowed for measurement of empirical depuration rate constants (k₂) independent of growth dilution for D4 and D5 of 0.035 and 0.040 d⁻¹, respectively, corresponding to elimination half-lives of approximately 20 d. These rate constants indicated that ∼70–75% of steady-state was achieved during exposure in both studies, resulting in empirical steady-state BMF and BMF(L) values of 0.28 and 0.66 for D4, respectively, and 0.32 and 0.85 for D5, respectively. Kinetic modeling using simple first-order uptake and depuration dynamics produced good agreement with experimental data, with D4 and D5 assimilation efficiencies of 40% and 44%, respectively. Growth-corrected depuration rate constants modeled over the entire study data set indicated slower elimination kinetics for D4 (k₂ of 0.007 d⁻¹ or half-life of 100 d) compared to D5 (k₂ of 0.010 d⁻¹ or elimination half-life of 69 d). Kinetic BMF_k values (i.e., k₁/k₂) for D4 and D5 were 1.7 and 1.3, respectively, with lipid-adjusted BMF_k(L) values of 4.0 and 3.4, respectively.     

Toxic effects of chemical pesticides (trichlorfon and dimehypo) on Dunaliella salina

Dunaliella salina, a unicellular green alga of environmental tolerance, was employed as test organism to investigate the toxicity effects of trichlorfon and dimehypo widely used in agriculture and veterinary as pesticides. The influences of trichlorfon and dimehypo on cell growth, β-carotene level, cell morphology changes, and activities of superoxide dismutase (Sod) and catalase (Cat) were investigated. At the concentrations less than 0.050 g L⁻¹ trichlorfon or 0.0005 g L⁻¹ dimehypo, cell responses were similar to control. When treated with 0.075-0.100 g L⁻¹ trichlorfon or 0.001-0.004 g L⁻¹ dimehypo, cell growth and β-carotene levels declined at first and then revived. When concentrations were higher than 0.125 g L⁻¹ trichlorfon or 0.005 g L⁻¹ dimehypo, both cell growth and β-carotene levels decreased until they were undetectable. The 10-d IC50 of trichlorfon and dimehypo on D. salina were 0.179 g L⁻¹ and 0.032 g L⁻¹. Both pollutants could stimulate the increase of Cat activity at a low concentration. Tolerance of D. salina to trichlorfon was obviously higher than that of dimehypo.     

Volatilization of polycyclic aromatic hydrocarbons from coal-tar-sealed pavement

The effects of the herbicide atrazine on the gill of the freshwater fish Prochilodus lineatus were evaluated after exposure of fish to 2, 10 and 25 μg L⁻¹ atrazine during 48 h (acute exposure) and 14 d (subchronic exposure). Ions and osmolality were measured in plasma and gill samples were taken to determine the Na⁺/K⁺-ATPase (NKA) and carbonic anhydrase (CA) activities and for morphological analysis. Plasma osmolality and Na⁺ and Cl⁻ ions changed depending on atrazine concentration, but atrazine exposure had no effect on the Na⁺/Cl⁻ ratio. NKA activity did not change after atrazine exposure, but CA activity decreased in fish exposed to 25 μg L⁻¹ for 14 d. Gill MRC density decreased after acute exposure but did not change in fish exposed to the subchronic treatment. The MRC density at the epithelial surface increased in fish exposed to 25 μg L⁻¹, and the MRC fractional area (MRCFA) increased in fish exposed to 10 μg L⁻¹. The changes in MRCs provide evidence of morphological adjustments to maintain ionic homeostasis in spite of the inhibition of CA activity at the highest atrazine concentration.     

Evaluation of food chain transfer of the antibiotic oxytetracycline and human risk assessment

There has been recent concern regarding the possibility of antibiotics entering the aquatic food chain and impacting human consumers. This work reports experimental results of the bioconcentration of the antibiotic oxytetracycline (OTC) by the Asian watermeal plant (Wolffia globosa Hartog & Plas) and bioaccumulation of OTC in watermeal and water by the seven-striped carp (Probarbus jullieni). They show, for the first time, the extent to which OTC is able to transfer from water to plant to fish and enter the food chain. The mean bioconcentration factor (dry weight basis) with watermeal was 1.28 × 10³ L kg⁻¹. Separate experiments were undertaken to characterize accumulation of OTC by carp from water and watermeal. These showed the latter pathway to be dominant under the conditions employed. The bioconcentration and biomagnification factors for these processes were 1.75 L kg⁻¹ and 2 × 10⁻⁴ kg g⁻¹ respectively. Using an aqueous concentration range of 0.34–3.0 μg L⁻¹, hazard quotients for human consumption of contaminated fish of 1.3 × 10⁻² to 1.15 × 10⁻¹ were derived.     

Emerging pollutants in sewage, surface and drinking water in Galicia (NW Spain)

A monitoring programme was carried out on wastewater, surface and drinking water on the NW area of Spain during the four seasons of a year period (November 2007-September 2008). This study covered a series of emerging pollutants of different classes, including pharmaceuticals, neutral and acidic organophosphorus flame retardant/plasticizers (OPs), triclosan, phenoxy-herbicides, insect repellents and UV filters. From the total set of 53 compounds, 19 were found in raw wastewater with median concentrations higher than 0.1 μg L⁻¹. Among them, salicylic acid, ibuprofen and the UV filter benzophenone-4 (BP-4) were the most concentrated, exceeding the 1 μg L⁻¹ median value. Subsequently, 11 of these contaminants are not efficiently enough removed in the small WWTPs tested and their median concentrations in effluents still surpassed the 0.1 μg L⁻¹, so that they can spread through surface water. These chemicals are the pharmaceuticals naproxen, diclofenac and atenolol; the OPs tri(2-chloroethyl) phosphate (TCEP), tri(chloropropyl) phosphate (TCPP), tri-n-butyl phosphate (TnBP), diphenyl phosphate (DPhP) and diethylhexyl phosphate (DEHP); and the sulphonate UV filters BP-4 and 2-phenylbenzimidazole-5-sulphonic acid (PBSA). These OPs were then the dominant emerging pollutants occurring in surface and drinking water, where they are detected in the 20-200 ng L⁻¹ range. Pharmaceuticals and UV filters are typically below the 10 ng L⁻¹ level. Finally, herbicides were only detected in the last sampling campaign under the 100 ng L⁻¹ drinking water European Union limit.     

Identification and dose dependency of ibuprofen biliary metabolites in rainbow trout

The biotransformation of the anti-inflammatory drug ibuprofen (IBF) was studied by exposing rainbow trout (Oncorhynchus mykiss) to IBF via intraperitoneal (i.p.) injection, and via water at four (0.17, 1.9, 13 and 145 μg L⁻¹) exposure levels for 4 d. Following exposure, the bile was collected and analyzed by LC–MS/MS methods. The identification of the formed metabolites in i.p. injected fish bile was based on the exact mass determinations by a time-of-flight mass analyzer (Q–TOF–MS) and on the studies of fragments and fragmentation patterns of precursor ions by ion trap mass analyzer (IT-MS). In addition to unmetabolized IBF, several phase I and phase II metabolites were found in the bile. The main metabolites were acyl glucuronides and taurine conjugates of IBF and of hydroxylated IBFs. The bioconcentration factors (BCF_bile), defined as the ratio of the sum of IBF and its metabolites in fish bile to the concentration of IBF in water, was determined following enzymatic deconjugation and was found to range from 14 000 to 49 000. The highest BCF_bile was found at the lowest exposure concentration (0.17 μg L⁻¹). The results show that rainbow trout has a high capacity for biotransformation of IBF, and the exposure of fish to sub μg L⁻¹ concentrations of IBF can be determined by the analyses of the biliary metabolites of the compound.     

Endosulfan induces changes in spontaneous swimming activity and acetylcholinesterase activity of Jenynsia multidentata (Anablepidae, Cyprinodontiformes)

We assessed changes in spontaneous swimming activity and acetylcholinesterase (AchE) activity of Jenynsia multidentata exposed to Endosulfan (EDS). Females of J. multidentata were exposed to 0.072 and 1.4 μg L⁻¹ EDS. Average speed and movement percentage were recorded during 48 h. We also exposed females to EDS at five concentrations between 0.072 and 1.4 μg L⁻¹ during 24 h, and measured the AchE activity in brain and muscle. At 0.072 μg L⁻¹ EDS swimming motility decreased relative to the control group after 45 h, while at 1.4 μg L⁻¹ EDS swimming motility decreased after 24 h. AchE activity significantly decreased in muscle when J. multidentata were exposed to EDS above 0.072 μg L⁻¹, while no significant changes were observed in brain. Thus, changes in swimming activity and AchE activity in muscle are good biomarkers of exposure to EDS in J. multidentata.     

Evaluation of recycling the effluent of hydrogen fermentation for biobutanol production: Kinetic study with butyrate and sucrose concentrations

Butyrate in the effluent of hydrogen-producing bioreactor is a potential feed for biobutanol production. For recycling butyrate, this study investigated the kinetics of biobutanol production by Clostridium beijerinckii NRRL B592 from different paired concentrations of butyrate and sucrose in a series of batch reactors. Results show that the lag time of butanol production increased with higher concentration of either sucrose or butyrate. In regression analyses, the maximum specific butanol production potential of 6.49 g g⁻¹ of dry cell was projected for 31.9 g L⁻¹ sucrose and 1.3 g L⁻¹ butyrate, and the maximum specific butanol production rate of 0.87 g d⁻¹ g⁻¹ of dry cell was predicted for 25.0 g L⁻¹ sucrose and 2.6 g L⁻¹ butyrate. The specific butanol production potential will decrease if more butyrate is added to the reactor. However, both sucrose and butyrate concentrations are weighted equally on the specific butanol production rate. This observation also is true on butanol yield. The maximum butanol yield of 0.49 mol mol⁻¹ was projected for 25.0 g L⁻¹ sucrose and 2.3 g L⁻¹ butyrate. In addition, a confirmation study found butanol yield increased from 0.2 to 0.3 mol mol⁻¹ when butyrate addition increased from 0 to 1 g L⁻¹ under low sugar concentration (3.8 g L⁻¹ sucrose). The existence of butyrate increases the activity of biobutanol production and reduces the fermentable sugar concentration needed for acetone–butanol–ethanol fermentation.     

Effect of chronic exposure to acetaminophen and lincomycin on Japanese medaka (Oryzias latipes) and freshwater cladocerans Daphnia magna and Moina macrocopa, and potential mechanisms of endocrine disruption

Chronic toxicity of acetaminophen and lincomycin were evaluated using freshwater organisms including two crustaceans (Daphnia magna and Moina macrocopa) and a fish (Oryzias latipes). H295R, a human adrenal cell was also used to understand the effects on steroidogenesis. In 21 d D. magna exposure, survival NOEC was found at 5.72 mg L⁻¹ and no reproduction related effects were noted at this level of exposure to acetaminophen, while 21 d survival or growth effects were not observed even at the highest exposure levels (153 mg L⁻¹) for lincomycin. In the chronic fish toxicity test, significant reduction in juvenile survival was observed at 30 d post-hatch (dph) at 95 mg L⁻¹ of acetaminophen, and 0.42 mg L⁻¹ of lincomycin. After the exposure to both pharmaceuticals, vitellogenin levels tended to increase in male fish at 90 dph. In the eggs which were prenatally exposed to 9.5 mg L⁻¹ of acetaminophen, reduced hatchability was observed. The results of H295R cell assay showed that both pharmaceuticals could alter steroidogenic pathway and increase estrogenicity. Endocrine disruption potentials and their ecological implication may deserve further studies. Our observations suggest however that ecological risks of both pharmaceuticals are negligible at the concentrations currently found in the environment.     

Histopathological effects of copper and lithium in the ramshorn snail, Marisa cornuarietis (Gastropoda, Prosobranchia)

The aim of this study was to determine and quantify effects of copper and lithium in tissues of early juveniles of the ramshorn snail, Marisa cornuarietis. For this purpose, hatchlings of M. cornuarietis were exposed for 7 days to a range of five different sublethal concentrations of copper (5, 10, 25, 50, and 75 μg Cu²⁺ L⁻¹) and lithium (50, 100, 200, 1000, and 5000 μg Li⁺ L⁻¹). Both metals changed the tissue structure of epidermis, hepatopancreas, and gills, varying between slight and strong reactions, depending on the copper and lithium concentration. The histopathological changes included alterations in epithelial and mucous cells of the epidermis, swelling of hepatopancreatic digestive cells, alterations in the number of basophilic cells, abnormal apices of digestive cells, irregularly shaped cilia and changes in the amount of mucus in the gills. The most sensible organ in M. cornuarietis indicating Cu or Li pollution is the hepatopancreas (LOECs were 10 μg Cu²⁺ L⁻¹, or 200 μg Li⁺ L⁻¹). In epidermis, mantle and gills relevant effects occurred with higher LOECs (50 μg Cu²⁺ L⁻¹, or 1000 μg Li⁺ L⁻¹). Base on LOECs, our results indicated that histopathological endpoints are high sensitivity to copper and lithium compared to endpoints for embryonic developmental toxicity.     

Effects of the pharmaceuticals gemfibrozil and diclofenac on biomarker expression in the zebra mussel (Dreissena polymorpha) and their comparison with standardised toxicity tests

Pharmaceuticals, including the lipid regulator gemfibrozil and the non-steroidal anti-inflammatory drug diclofenac have been identified in waste water treatment plant effluents and receiving waters throughout the western world. The acute and chronic toxicity of these compounds was assessed for three freshwater species (Daphnia magna,Pseudokirchneriella subcapitata, Lemna minor) using standardised toxicity tests with toxicity found in the non-environmentally relevant mid mg L⁻¹ concentration range. For the acute endpoints (IC₅₀ and EC₅₀) gemfibrozil showed higher toxicity ranging from 29 to 59 mg L⁻¹ (diclofenac 47-67 mg L⁻¹), while diclofenac was more toxic for the chronic D. magna 21 d endpoints ranging from 10 to 56 mg L⁻¹ (gemfibrozil 32-100 mg L⁻¹). These results were compared with the expression of several biomarkers in the zebra mussel (Dreissena polymorpha) 24 and 96 h after exposure by injection to concentrations of 21 and 21,000 μg L⁻¹ corresponding to nominal concentrations of 1 and 1000 μg L⁻¹. Exposure to gemfibrozil and diclofenac at both concentrations significantly increased the level of lipid peroxidation, a biomarker of damage. At the elevated nominal concentration of 1000 μg L⁻¹ the biomarkers of defence glutathione transferase and metallothionein were significantly elevated for gemfibrozil and diclofenac respectively, as was DNA damage after 96 h exposure to gemfibrozil. No evidence of endocrine disruption was observed using the alkali-labile phosphate technique. Results from this suite of biomarkers indicate these compounds can cause significant stress at environmentally relevant concentrations acting primarily through oxidation pathways with significant destabilization of the lysosomal membrane and that biomarker expression is a more sensitive endpoint than standardised toxicity tests.     

Dietary exposure of rainbow trout to 8:2 and 10:2 fluorotelomer alcohols and perfluorooctanesulfonamide: Uptake, transformation and elimination

The bioaccumulation of perfluorooctanesulfonamide (PFOSA) and two fluorotelomer alcohols (8:2 FTOH, 10:2 FTOH) by rainbow trout (Oncorhynchus mykiss) through dietary exposure, including depuration rates and metabolism was investigated. Concentrations in the spiked feed ranged from 10.9 μg g⁻¹ wet weight (wet wt) for PFOSA and 6.7 μg g⁻¹ wet wt for 8:2 FTOH to 5.0 μg g⁻¹ wet wt for 10:2 FTOH. Trout was fed at 1.5% body weight per day for 30 d and depuration was followed for up to 30 d following previously published dietary exposure protocols. Perfluorooctanesulfonate (PFOS) was the major perfluoroalkylsulfonate (PFSA) detected in fish following dietary exposure to PFOSA. Half-lives of PFOS and PFOSA were 16.9 ± 2.5 and 6.0 ± 0.4 d, respectively. A biomagnification factor (BMF) of 0.023 was calculated for PFOSA which indicates that dietary exposure to PFOSA does not result in biomagnification in the rainbow trout. PFOS had a BMF of 0.08. The fluorotelomer saturated acids (8:2 FTCA, 10:2 FTCA) and fluorotelomer unsaturated acids (8:2 FTUCA, 10:2 FTUCA) were the major products detected in rainbow trout following dietary exposure to 8:2 FTOH and 10:2 FTOH, respectively. Half-lives were 3.7 ± 0.4, 2.1 ± 0.5, 3.3, and 1.3 d for 10:2 FTCA, 10:2 FTUCA, 8:2 FTCA, and 8:2 FTUCA, respectively. Small amounts of perfluorooctanoate (PFOA) and perfluorodecanoate (PFDA) were also detected in the FTOH exposed fish.     

Distribution of Se and its species in Myriophyllum spicatum and Ceratophyllum demersum growing in water containing Se (VI)

The uptake of Se (VI) by two aquatic plants, Myriophyllum spicatum L. and Ceratophyllum demersum L., and its effects on their physiological characteristics have been studied. Plants were cultivated outdoors under semi-controlled conditions and in two concentrations of Na selenate solution (20 μg Se L⁻¹ and 10 mg Se L⁻¹). The higher dose of Se reduced the photochemical efficiency of PSII in both species, while the lower dose had no effect on PSII. Addition of Se had no effect on the amounts of chlorophyll a and b. The concentration of Se in plants grown in 10 mg Se L⁻¹, averaged 212 ± 12 μg Se g⁻¹ DM in M. spicatum (grown from 8-13 d), and 492 ± 85 μg Se g⁻¹ DM in C. demersum (grown for 31 d). Both species could take up a large amount of Se. The amount of soluble Se compounds in enzyme extracts ranged from 16% to 26% in control, and in high Se solution from 48% to 36% in M. spicatum and C. demersum, respectively. Se-species were determined using HPLC-ICP-MS. The main soluble species in both plants was selenate (∼37%), while SeMet and SeMeSeCys were detected at trace levels.     

Integrated survey on toxic effects of lindane on neotropical fish: Corydoras paleatus and Jenynsia multidentata

We report the effect of lindane on fish experimentally exposed to lindane. Sublethal toxicity was assessed through (a) changes in histopathology; (b) the activity of GST in different organs; and (c) bioaccumulation in exposed fish. We present a survey on toxic effects of lindane at these three levels, proposing a sequence of dose-dependent effects. Physiological damage was reversible at lowest doses, but severe at the highest, including damage consistent with fibrosis in liver and karyolitic nucleus in brain of both studied species. Exposure of Jenynsia multidentata above 6 μg L⁻¹ caused activation a GST in liver and gills, followed by inhibition at 75 μg L⁻¹. Interestingly, the bioaccumulation rate was suddenly increased when GST was inhibited. Corydoras paleatus exposed to 6.0 μg L⁻¹ lindane did not present significant changes in GST activity; however, enzymatic inhibition was observed above 25 μg L⁻¹. The bioaccumulation rate in C. paleatus remained constant throughout the experiments. All in all, these results evidence that C. paleatus is more sensitive to lindane than J. multidentata.     

Lethal effects of abamectin on the aquatic organisms Daphnia similis, Chironomus xanthus and Danio rerio

Abamectin is used as an acaricide and insecticide for fruits, vegetables and ornamental plants, as well as a parasiticide for animals. One of the major problems of applying pesticides to crops is the likelihood of contaminating aquatic ecosystems by drift or runoff. Therefore, toxicity tests in the laboratory are important tools to predict the effects of chemical substances in aquatic ecosystems. The aim of this study was to assess the potential hazards of abamectin to the freshwater biota and consequently the possible losses of ecological services in contaminated water bodies. For this purpose, we identified the toxicity of abamectin on daphnids, insects and fish. Abamectin was highly toxic, with an EC₅₀ 48 h for Daphnia similis of 5.1 ng L⁻¹, LC₅₀ 96 h for Chironomus xanthus of 2.67 μg L⁻¹ and LC₅₀ 48 h for Danio rerio of 33 μg L⁻¹.     

Aerobic degradation of tetrabromobisphenol-A by microbes in river sediment

This study investigated the aerobic degradation of tetrabromobisphenol-A (TBBPA) and changes in the microbial community in river sediment from southern Taiwan. Aerobic degradation rate constants (k₁) and half-lives (t_1/2) for TBBPA (50 μg g⁻¹) ranged from 0.053 to 0.077 d⁻¹ and 9.0 to 13.1 d, respectively. The degradation of TBBPA (50 μg g⁻¹) was enhanced by adding yeast extract (5 mg L⁻¹), sodium chloride (10 ppt), cellulose (0.96 mg L⁻¹), humic acid (0.5 g L⁻¹), brij 30 (55 μM), brij 35 (91 μM), rhamnolipid (130 mg L⁻¹), or surfactin (43 mg L⁻¹), with rhamnolipid yielding a higher TBBPA degradation than the other additives. For different toxic chemicals in the sediment, the results showed the high-to-low order of degradation rates were bisphenol-A (BPA) (50 μg g⁻¹) > nonylphenol (NP) (50 μg g⁻¹) > 4,4′-dibrominated diphenyl ether (BDE-15) (50 μg g⁻¹) > TBBPA (50 μg g⁻¹) > 2,2′,3,3′,4,4′,5,5′,6,6′-decabromodiphenyl ether (BDE-209) (50 μg g⁻¹). The addition of various treatments changed the microbial community in river sediments. The results also showed that Bacillus pumilus and Rhodococcus ruber were the dominant bacteria in the process of TBBPA degradation in the river sediments.     

Spatial and seasonal variations in atrazine and metolachlor surface water concentrations in Ontario (Canada) using ELISA

Concerns regarding the impacts of pesticides on aquatic species and drinking water sources have increased demands on water quality monitoring programs; however the costs of sample analysis can be prohibitive. In this study we investigated enzyme-linked immunosorbent assay (ELISA) as a cost-effective, high through-put method for measuring pesticide concentrations in surface waters. Seven hundred and thirty-nine samples from 158 locations throughout Ontario were analysed for atrazine and metolachlor from April to October 2007. Concentrations ranged from <0.1 to 3.91 μg L⁻¹ (median = 0.12 μg L⁻¹) for atrazine and from <0.1 to 1.83 μg L⁻¹ (median = 0.09 μg L⁻¹) for metolachlor. Peak concentrations occurred in late spring/early summer, in rural agricultural locations, and decreased over the remainder of the growing season for both herbicides. About 3% of the samples that had ELISA results occurring above the limit of quantification (0.10 μg L⁻¹) were evaluated against gas chromatography-mass spectrometry (GC-MS). Linear regression analysis revealed a R² value of 0.88 and 0.39, for atrazine and metolachlor, respectively. ELISA tended to overestimate concentrations for atrazine and metolachlor, most likely because the ELISA kits also detect their metabolites. Atrazine data suggest that ELISA may be used complementary with GC-MS analysis to enhance the spatial and temporal resolution of a water quality monitoring study. The commercially available metolachlor ELISA kit requires further investigation. ELISA may be used to detect atrazine and metolachlor in surface water samples, but it is not recommended as a quantitative replacement for traditional analytical methods.