Assessing Se cycling and toxicity in aquatic ecosystems

Toxic substances exert impacts on ecosystems at several levels: biogeochemical, toxicological, and populations/communities. Integrating exposure (biogeochemistry) and effects (toxicology) into an ecological context requires models as a necessary step to prediction and assessment of effects on populations and their interactions. To this end, research is being conducted to develop techniques for predicting the effects of Se on aquatic ecosystems. The objective is to develop mechanistic models to predict biogeochemical cycling, toxicological processes, and toxic effects on population and community dynamics. Earlier research demonstrated that different chemical forms of Se have different toxicological properties. Biogeochemical research culminated with a dynamic model of the Se cycle. In ongoing research, experiments are being conducted on microorganisms, phytoplankton, microzooplankton, zooplankton, benthic invertebrates, and fish to measure uptake, biotransformation, and depuration kinetics of different chemical forms of Se, transfer through the food web, and effects on growth, reproduction, community interactions, and survival. This information will provide the basis for the ecosystem effects model.     

Comparisons of terrestrial and aquatic bioassays for oil-contaminated soil toxicity

Background  Petroleum products are widely used in various sections of industry and they are one of the most abundant sources of environmental contamination. These products are classified by their physico-chemical properties such as boiling point, density and viscosity. Oil contamination in the environment is primarily evaluated by measuring the chemical concentrations of petroleum products in the solid or water phase. The results of chemical analyses do not correspond directly with the harmful environmental effects of petroleum products on the soil flora and fauna, because the interactions between oil compounds and the production of their methabolites in soil are not measured in chemical assessments. These kinds of effects of complex chemical mixtures in soil can be estimated by bioassays. Therefore, ecotoxicological tests are important for estimating soil quality in the risk assessment of oil-contaminated soil sites. Objectives  The objective of this study was to examine the oil-contaminated soil site of a closed petrol station with both chemical and ecotoxicological methods. The goals of this study were to compare the sensitivity of the terrestrial and aquatic bioassays and to compare the toxicity responses of aquatic bioassays determined from three different extraction procedures. In addition, our aim was to characterise a cost-effective battery of bioassays that could be applied to a comparison of oil-contaminated soils. It was in our interest to investigate oil-contaminated soil with oil concentrations of 2500–12000 mg/kg and to find out the possible differences between terrestrial and aquatic toxicity tests. Methods  Six soil samples from a closed petrol station were examined for toxicity with terrestrial and aquatic tests. Terrestrial tests includedEnchytraeus albidus survival and reproduction assays and seed germination assays using wheat, cress, lettuce, and red clover seeds and growth inhibition assays of onions. The toxicities of the water-extractable fractions of the soil samples obtained from three different extractions were tested with aquatic bioassays based on plants (onion and duckweed growth inhibition tests), microbes (luminescent bacteria test), and enzyme inhibition (reverse electron transport test, RET). Chemical analyses of the solid samples were carried out simultaneously. Results. Oil concentrations ranged from 2500 to 12000 mg/kg, BTEX varied from 300 to 2800 mg/kg, and fuel additives: MTBE and TAME from 0.0 1 to 260 mg/kg. Only the sample contain-ing 12000 mg/kg oil had a significant toxic impact on all test organisms. Soil samples with oil concentrations 2500–6200 mg/ kg had no or only slight adverse effects on the test organisms with one exception, theE. albidus reproduction test. TheE. albidus survival and reproduction tests were the most sensitive bioassays of the terrestrial tests, and the luminescent bacteria test of the aquatic tests.     

Comparison ofDaphnia magna,rainbow trout and bacterial-based toxicity tests of Ontario Hydro aquatic effluents

Over a one year program of intensive monitoring of effluents from Ontario Hydro's nuclear, fossil and hydroelectric generating facilities, theDaphnia magna and rainbow trout,Oncorhynchus mykiss, acute toxicity tests correlated well, with 61 % of the toxic effluents toxic to both species. If the effluent was toxic to only one of the test species it was generally toxic toD. magna, with from 23 to 57% of the toxic effluents toxic toD. magna only. The greater sensitivity ofD. magna to boiler blowdown effluent likely resulted from a combination of the low conductivity of boiler blowdown effluent and the smaller size and greater surface to volume ratio ofD. magna relative to rainbow trout.D. magna were also particularly susceptible to oil/water separator samples, with the daphnids frequently observed to be caught at the surface/water interface. These observations suggest that an accumulation of organic material at the air/water interface was responsible for the mortality ofD. magna. In subsequent tests, we also examined the relationship between theD. magna acute toxicity test and a bacterial-based assay (Toxi-Chromotest®) for several toxic effluents from Ontario Hydro stations to determine if bacterial-based tests could provide similar information in less time with smaller sample volumes. TheD. magma acute toxicity test did not correlate well with the bacterial-based Toxi-chromotest®. In particular, many of the samples which were toxic toD. magna were not toxic to the Toxi-chromotest® assay. The poor correlation between theD. magna and Toxi-chromotese® likely relates to both the relatively low toxicity of many of the effluent samples, and the fact that in many cases toxicity likely resulted from relatively simple combinations of inorganic toxicants. Accordingly, the Toxi-Chromotest® assay would not seem suitable as a surrogate for theD. magna acute toxicity test for our effluents.     

Combined effect of cypermethrin and copper on catalase activity in soil

Background, aim, and scope  Pollution of soil environment has become a serious problem in many countries. Repeated application of bordeaux mixture and pyrethroids insecticides have led to elevated copper (Cu) and pyrethroids concentrations in vineyard surface soils. Therefore, it is recommended to evaluate the combined effect of copper and pyrethroids on soil enzymes. Our aim was to get a more comprehensive understanding of the effects of Cu and cypermethrin on the soil catalase, and to provide more information about the potential ecological risk of chemicals on the soil ecosystem. Materials and methods  The dried and sieved soil sample was first thoroughly mixed with aqueous solution of CuSO₄ 5H₂O, and acetone solution of cypermethrin according to the orthogonal design, and then incubated at 25°C for 35 days. Five concentration levels for each pollutant (Cu and cypermethrin) were studied. Control without any artificial contamination received the same amount of distilled water and acetone. Each test was conducted with three replications. Moisture in the incubated soil samples was kept at 60% of the full soil water holding capacity by weighing daily. Catalase activity was determined by back-titrating residual H₂O₂ with KMnO₄ after 7, 14, 21, 28, and 35 days. Data treatment was essentially based on analysis of the variance test. Results  During the incubation time, soil catalase activity was lower than the control samples and the result ranged from 70.64% to 100%, except for that of the two samples S6 and S13. The catalase activity in all samples was declined after application of Cu, without addition of cypermethrin. While the concentration of cypermethrin ranged from 0 to 150 mg kg^–1, without the addition of Cu, the variety of catalase activity was as follows: restrained–activated–restrained. The combined effect of cypermethrin and Cu on soil catalase activity depends largely on the concentration of pollutants. Discussion  The presumable explanation of the result that the catalase was inhibited by single Cu addition was due to: (1) complexation of the substrate, (2) combination with the protein-active groups of the enzymes, or (3) reaction with the enzyme–substrate complex. In our study, there were some differences in the catalase when soil samples were treated with a different concentration of cypermethrin. This is possibly related to the protect mechanism of soil catalase. In addition, the combined effect of cypermethrin and Cu on catalase activity is stronger than single cypermethrin, while weaker than single Cu. One of the possible explanations of this phenomenon is related with the interaction between cypermethrin and Cu. Another may be related to bioavailability. Conclusions  The combined effect of cypermethrin and Cu on soil catalase activity depends largely on the concentration of the pollutants. The magnitude and type of interaction may be strongly dependent on the level of response and the relative proportion of the components in the mixture. These factors should therefore be considered in risk assessments and in the setting of soil quality criteria. Recommendations and perspectives  Generally speaking, the influence of pesticides and heavy metals on soil is a long-term process and is closely related to soil characteristics. Much more should be done to clearly understand the mechanism of interaction between cypermethrin and Cu on soil.     

铜对土壤中功夫菊酯和氯氰菊酯迁移和扩散的影响

Repeated applications of bordeaux mixture （a blend of copper sulfate and calcium hydroxide） and pyrethroid insecticides （Pys） have led to elevated copper （Cu） and Pys concentrations in vineyard surface soils. To understand the potential influence of Cu on the fate of Pys in the soil environment, we selected two Pys, cypermethrin （CPM） and lambda-cyhalothrin （λ-CHT）, and two typical Chinese vineyard soils, Haplic Acrisol and Luvic Phaeozem, as experimental samples. The dissipation experiment was conducted at room temperature in the dark, and the transport of both Pys through the soils was investigated using soil thin-layer chromatography. The results showed that the transport of Pys in both soils increased as the Cu²⁺ concentration increased from 0 to 100 mg L^-1 , and Pys were more transportable in Haplic Acrisol （HA） than in Luvic Phaeozem （LP） under the same experimental conditions. For CPM, only 100 mg L^-1 of Cu²⁺ significantly （P<0.05） increased Pys transport through both soils relative to water. Lambda-CHT was significantly （P<0.05） transported through HA by all the Cu²⁺ concentrations compared to water, and all but the 1 mg L^-1 of Cu²⁺ significantly （P<0.05） increased the transport of λ-CHT through LP relative to water. However, the dissipation rates of CPM and λ-CHT decreased with the addition of Cu to soils. Our findings suggest that the risk of groundwater contamination by Pys increases in the soils with elevated Cu concentrations.     

长期施肥对土壤中氯氰菊酯降解转化的影响

采用长期不同施肥处理土壤：有机肥（OM）、无机肥（NPK、PK、NK）和不施肥（CK）研究施肥对氯氰菊酯降解的影响,通过测定土壤中氯氰菊酯残留量及降解产物3-苯氧基苯甲酸生成量来确定其降解速度。结果表明：不同施肥处理对氯氰菊酯在土壤中降解有显著影响,其中在PK、CK土壤中降解较快,半衰期分别为9.6 d和10.7 d,在NK土壤中降解最慢,半衰期为15.1 d,长期施用有机肥（OM）较无机肥（NPK）降解呈增加趋势,但未达显著水平,半衰期分别为10.8 d和11.8 d。相关分析表明土壤中速效氮含量与氯氰菊酯半衰期呈显著负相关,长期偏施氮肥可提高土壤中速效氮的含量,进而能显著降低氯氰菊酯在土壤中降解速度。氯氰菊酯在OM、NPK土壤中降解较慢的原因可能是土壤高有机质含量增加了对农药的吸附,进而抑制了其降解。     

Abiotic enantiomerization of permethrin and cypermethrin: effects of organic solvents

All synthetic pyrethroids are chiral compounds, and isomerization has been frequently observed from exposure to certain solvents. However, so far, pyrethroid isomerization caused by solvents has not been characterized at the enantiomer level. In this study, we evaluated the occurrence of enantiomerization of two commonly used pyrethroids, permethrin and cypermethrin, in various organic solvents and solvent-water systems. The four stereoisomers of permethrin were stable under all test conditions. Rapid enantiomerization of cypermethrin was observed in isopropanol and methanol but not in n-hexane, acetone, or methylene chloride. After 4 days at room temperature, 18-39% conversions occurred for the different cypermethrin stereoisomers in isopropanol and methanol, and the enantiomerization invariably took place at the alpha-carbon position. The extent of enantiomerization was affected by temperature dependence and was also influenced by water as a cosolvent. In solvent-water mixtures, cypermethrin underwent gradual enantiomerization in acetone-water and rapid enantiomerization in isopropanol-water or methanol-water. The extent of enantiomerization varied among the solvents and as a function of the solvent-to-water ratio. Results from this study suggest that exposure to certain solvents and water may cause artifacts in chiral analysis and that for isomer-enriched pyrethroid products, such abiotic enantiomerization may render the products less effective because the conversion leads to the formation of inactive stereoisomers.     

Acute toxicity of water soluble fractions derived from a coal liquid (SCR-II) to three aquatic organisms

Acute toxicity screening tests were conducted with water soluble fractions (WSFs) of a solvent refined coal (SRC-II) liquid from a pilot plant and three reference organisms: the cladoceran Daphnia magna, the fathead (FH) minnow Pimephales promelas, and larvae of the midge fly Chironomus tentans. Stock WSFs typically contained 900 to 1100 mg l^?1 total carbon (TC) and 700 to 800 mg l^?1 total dye complexable phenolics, with lower concentrations of aromatic and saturate hydrocarbons and N compounds. Under standard test conditions (temperature 20 °C, pH 7.3 to 8.2 and hardness 65 to 80 mg l^?1 CaCO₃), mean LC50 values in mg l^? TC were 3.3 for daphnia, 11.l for FH minnow, and 13.7 for midge larvae. Acute toxicity was also examined under other water quality conditions (temperature 10 or 25 °C, pH 6.0 or 6.5, and hardness ? 180 to 220 mg 1^?1 CaCO₃). The coal liquid was less toxic to daphnids at 10 °C than at 20 or 25 °C, but response of other organisms at different temperatures varied. The pH of the liquid had little effect on toxicity values. All organisms were less susceptible in hard water. Chemical compositions of stock WSFs were similar, suggesting that temperature, pH, and hardness had little effect on solubility of major synfucl components. Dilution indexes for stock WSFs were higher than for petroleum oils, and reflect the greater solubility of chemicals from the liquified coal in freshwater.     

Separation and analysis of diastereomers and enantiomers of cypermethrin and cyfluthrin by gas chromatography

Synthetic pyrethroid (SP) insecticides are of environmental significance because of their high aquatic toxicity. Due to their chirality, SP compounds contain multiple diastereomers and enantiomers. However, due to great structural similarities and lack of isomer standards, gas chromatographic (GC) analysis of SP diastereomers or enantiomers is poorly developed. In this study, we used a HP-5 column to separate the diastereomers and a beta-cyclodextrin-based enantioselective column (BGB-172) to separate the enantiomers of cypermethrin (CP) and cyfluthrin (CF). Resolved peaks were identified by comparing chromatograms of isomer-enriched CP products. Diastereomers of both CP and CF were separated on the HP-5 column. On the BGB-172 column, enantiomers of all cis diastereomers were separated, while those of trans diastereomers were not separated. The elution order appears to be regulated by configuration, a finding which may allow peak identification in the absence of isomer standards. When coupled with electron capture detection, the developed methods had low detection limits and may be used for analysis of SP diastereomers and enantiomers in environmental samples.     

Development of an enzyme-linked immunosorbent assay for the pyrethroid cypermethrin

A competitive enzyme-linked immunosorbent assay (ELISA) for the detection of cypermethrin was developed. Two haptens, the trans- and cis-isomers of 3-[(+/-)-cyano-3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropanecarbonyloxy]methyl]phenoxyacetic acid, were conjugated with thyroglobulin as immunogens. Four antisera were generated and screened against six different coating antigens. The assay that was the most sensitive for cypermethrin was optimized and characterized. The IC(50) for cypermethrin was 13.5 +/- 4.3 microg/L, and the lower detection limit (LDL) was 1.3 +/- 0.5 microg/L. This ELISA had relatively low cross-reactivities with other major pyrethroids, such as deltamethrin, phenothrin, resmethrin, fluvalinate, and permethrin. Methanol was found to be the best organic cosolvent for this ELISA, with an optimal sensitivity observed at a concentration of 40% (v/v). The assay parameters were unchanged at pH values between 5.0 and 8.0, whereas higher ionic strengths strongly suppressed the absorbances. To increase the sensitivity of the overall method, a C(18) sorbent-based solid-phase extraction was applied to various domestic and environmental water samples. The water samples, fortified with cypermethrin, were analyzed according to this method. Good recoveries and correlation with spike levels were observed.     

Bioparticulate solubilization and biodegradation in semi-continuous aerobic thermophilic digestion

The effects of charge size, cycle time, and the presence of added N on the extent of solubilization and biodegradation of microbial solids were investigated during semi-continuous operation of an aerobic thermophilic digestion process. Use of a charge size of 50% of the bioreactor operating volume resulted in the removal of more than 59% of the total suspended solids concentration in the feed and showed enhanced performance compared with when a 25% charge size was used. The addition of a supplementary N source resulted in enhanced dissolved organic carbon (DOC) concentrations with the 50% charge size, but did not affect overall solids removal. With the 25% charge size, addition of a supplementary N source resulted in an overall improvement in process performance.     

氮对土壤中氯氰菊酯及其降解产物3-苯氧基苯甲酸降解的影响

Increasing use of pyrethroid insecticides has resulted in concerns regarding potential effects on human health and ecosystems. Cypermethrin and its metabolite 3-phenoxybenzoic acid （PBA） have exerted adverse biological impacts on the environment; therefore, it is critically important to develop different methods to enhance their degradation. In this study, incubation experiments were conducted using samples of an Aquic Inceptisol supplied with nitrogen （N） in the form of NH4NO3 at different levels to investigate the effect of nitrogen on the degradation of cypermethrin and PBA in soil. The results indicated that appropriate N application can promote the degradation of cypermethrin and PBA in soil. The maximum degradation rates were 80.0% for cypermethrin after 14 days of incubation in the treatment with N at a rate of 122.1 kg ha^-1 and 41.0% for PBA after 60 days of incubation in the treatment with N at a rate of 182.7 kg ha^-1. The corresponding rates in the treatments without nitrogen were 62.7% for cypermethrin and 27.8% for PBA. However, oversupplying N significantly reduced degradation of these compounds. Enhancement of degradation could be explained by the stimulation of microbial activity after the addition of N. In particular, dehydrogenase activities in the soil generally increased with the addition of N, except in the soil where N was applied at the highest level. The lower degradation rate measured in the treatment with an oversupply of N may be attributed to the microbial metabolism shifts induced by high N.     

木质纤维素原料厌氧生物降解研究进展

分析了木质纤维素原料生物降解特性的分析,重点从两个方面介绍了利用这种原料进行厌氧生物降解产沼气的研究进展:原料预处理技术,包括物理处理、化学处理、生物处理以及热处理技术;厌氧发酵工艺,包括单相发酵和两相发酵工艺,以及混合原料发酵工艺,并简要探讨了木质纤维素原料厌氧生物降解进一步的研究和发展方向。     

烟草薄片生产废水中烟碱的厌氧降解及反硝化强化

为强化废水中烟碱的厌氧生物降解性能,对造纸法制烟草薄片产生的废水,在厌氧颗粒污泥UASB小试反应器中的生物降解进行监测和分析,测定了厌氧处理过程中烟碱的降解曲线,发现微生物对烟碱的降解过程可能涉及协同降解机理。提出了以反硝化反应强化厌氧过程中烟碱降解的思路,通过外加硝酸盐来诱导驯化厌氧颗粒污泥中硝化菌的代谢活动,经过驯化,厌氧颗粒污泥UASB小试反应器出水中烟碱浓度由120 mg/L以上降至约25 mg/L,同时反硝化反应促进了废水中其他有机物的深度降解,出水化学需氧量（CODCr）由约600 mg/L降至200～300 mg/L,反硝化强化造纸法烟草薄片废水中烟碱生物降解作用明显。     

Perchlorate biodegradation in contaminated soils and the deep unsaturated zone

In the United States, perchlorate has been officially recognized as an environmental contaminant. In Israel, widespread perchlorate contamination has been found in the 40-m deep vadose zone near an ammonium perchlorate manufacturing plant north of Tel Aviv, above the central part of Israel's coastal aquifer, with peak concentrations of 1200 mg kg_sediment^?1. In this study, we examined the perchlorate-reduction potential by native microbial communities along this deep contaminated vadose zone profile. We analyzed the effect of various concentrations of nitrate on perchlorate reduction and determined whether perchlorate concentrations in the profile are toxic to the native microbial population. All experiments were performed in soil slurries with sediments taken from the contaminated site. Perchlorate was reduced to chloride in three (1, 15 and 35 m) of the four examined sediment samples taken from different depths (1, 15, 20, and 35 m below surface). No activity was observed in the sediment sample from 20 m below land surface, suggesting low viable microbial communities and water content, and high perchlorate concentrations. In the presence of nitrate, the lag time for perchlorate degradation was inversely correlated to nitrate concentration. We found no perchlorate degradation as long as nitrate was present in the system, and perchlorate degradation initiated only after all the nitrate had been reduced. Nitrate-reduction rates were correlated to the initial concentrations of nitrate and no lag period was observed for nitrate reduction. Viable microbial populations were observed at both high concentrations (10,000 mg l^?1 and 20,000 mg l^?1) and with no addition of perchlorate, at levels of 2.35 × 10⁵, 4.01 × 10⁵, and 3.41 × 10³ CFU ml^?1, respectively; these results were well correlated to those found by PCR amplification analysis of chlorite dismutase. We suggest that the microbial community has adapted to the conditions of high perchlorate concentrations in the unsaturated zone over 30 years of exposure. When no external carbon source was added to the slurry of soil from land surface, all perchlorate was removed after 134 days of incubation. The average perchlorate-reduction rate using natural organic matter as a carbon source was 0.45 mg day^?1, while the average rate using acetate as an external carbon source was 7.2 mg day^?1.     

Nitrogen starvation promotes biodegradation of N-heterocyclic compounds in soil

Mineralization studies were performed to examine the impact of N deprivation on microbial utilization of the N-heterocyclic herbicides, atrazine and cloransulam-methyl (C-M). Soil depleted by 130 years of cropping to Zea mays without fertilization was contrasted to soil from the same site regularly receiving fertilizers. Long-term N deprivation promoted rapid degradation of atrazine and the C-M pyrimidine ring, whereas no significant effect was observed on degradation of the C-M phenyl ring. When a sandy soil naturally low in N was used, addition of 5 or more μg NH₄-N/g soil suppressed mineralization of the C-M pyrimidine ring. These findings provide insight into organic N availability and suggest broad implications for the effect of exogenous N in degradation of heterocyclic herbicides.     

Assessing selenium cycling and accumulation in aquatic ecosystems

We conducted a joint experimental research and modeling study to develop a methodology for assessing selenium (Se) toxicity in aquatic ecosystems. The first phase of the research focused on Se cycling and accumulation. In the laboratory, we measured the rates and mechanisms of accumulation, transformation, and food web transfer of the various chemical forms of Se that occur in freshwater ecosystems. Analytical developments helped define important Se forms. We investigated lower trophic levels (phytoplankton and bacteria) first before proceeding to experiments for each successive trophic component (invertebrates and fish). The lower trophic levels play critical roles in both the biogeochemical cycling and transfer of Se to upper trophic levels. The experimental research provided the scientific basis and rate parameters for a computer simulation model developed in conjunction with the experiments. The model includes components to predict the biogeochemical cycling of Se in the water column and sediments, as well as the accumulation and transformations that occur as Se moves through the food web. The modeled processes include biological uptake, transformation, excretion, and volatilization; oxidation and reduction reactions; adsorption; detrital cycling and decomposition processes; and various physical transport processes within the water body and between the water column and sediments. When applied to a Se-contaminated system (Hyco Reservoir), the model predicted Se dynamics and speciation consistent with existing measurements, and examined both the long-term fate of Se loadings and the major processes and fluxes driving its biogeochemical cycle.     

Persistence and biodegradation of selected organophosphorus insecticides in flooded versus non-flooded soils

Summary The persistence of parathion, methyl parathion and fenitrothion in five tropical soils of varying physicochemical characteristics was compared under flooded and non-flooded conditions. The degradation of all the three insecticides was more rapid under flooded conditions than under non-flooded conditions in four out of five soils. Degradation of these insecticides proceeded by hydrolysis under non-flooded conditions and essentially by nitro group reduction and to a minor extent by hydrolysis under flooded conditions. Kinetic analysis indicated that degradation of the three insecticides followed a first-order reaction irrespective of the soil and water regime. The degradation of these organophosphorus insecticides was accelerated after repeated applications to flooded alluvial soil. Nitro group reduction was the major pathway of degradation for all the three insecticides after the first addition while the rate of hydrolysis increased after each successive addition.