The present study deals with the biodegradation of catechol through co-metabolism with glucose in aqueous solution as primary substrate in an upflow anaerobic sludge blanket (UASB) reactor. Batch studies indicated that the 1000mgl(-1) glucose concentration was sufficient to cometabolize and degrade catechol in an aqueous solution up to a concentration of 1000mgl(-1). The reactor operated at 35+/-2 degrees C, and at a constant hydraulic retention time of 8h with a gradual stepwise increase in catechol concentration from 100 to 1000mgl(-1) along with glucose as a cosubstrate. The results showed that the catechol was successfully mineralized in an UASB reactor in which microbial granulation was achieved with only glucose as the substrate. The reactor showed > or = 95% COD removal efficiency with 500-1000mgl(-1)catechol concentration in the feed and a glucose concentration of 1500mgl(-1) as a cosubstrate. Similar efficiency was obtained at a constant catechol concentration of 1000mgl(-1) with 500-1000mgl(-1) glucose concentration. Once the reactor got acclimatized with catechol, higher concentrations of catechol can be mineralized with a minimum amount of glucose as the cosubstrate without affecting the performance of the UASB reactor. 相似文献
We collected and analyzed 955 individual fish (six species) for sexual differences in PCB bioaccumulations from a southeastern, USA reservoir. Using 2-way ANCOVAs, we found significant differences in fillet PCB concentrations between sexes for channel catfish (Ictalurus punctatus), largemouth bass (Micropterus salmoides) and spotted bass (Micropterus punctulatus). Striped bass (Morone saxatilus), black crappie (Pomoxis nigromaculatus) and freshwater drum (Aplodinotus grunniens) did not display differences between sexes in PCB concentrations. We suspect that sexual differences may be due to biological differences in reproduction, relative motility and lipid deposition. For one species (striped bass), sexual differences in PCB concentrations were inconsistent with a study in the Hudson River suggesting that sexual differences in bioaccumulations can change across ecosystems. Two species which did show sexual differences, largemouth bass and channel catfish, are often chosen as representative species (e.g., "piscivore" and "benthivore") in contaminant monitoring in many USA states indicating human consumption and risk management decisions would be improved if an equal number of male and female fish were included in composite PCBs analysis. This could reduce variability in fish PCBs data from which consumption advisories are based. 相似文献
The objective of this research was to assess the degradation of fipronil [5-amino-1-(2,6-dichloro-alpha,alpha,alpha -trifluoro-p-tolyl)-4-trifluoromethylsulfinylpyrazole-3-carbonitrile] in soils from sugar cane fields in Northeastern Brazil. Degradation experiments were carried out under laboratory conditions (controlled temperature and in the dark), where sterile and non-sterile soils (Ustoxs) were incubated [under moisture content of 55% of the water holding capacity (WHC)] and analyzed for fipronil disappearance and metabolite formation. Microbial communities present in the soil degrade fipronil. However, biodegradation seems to be dependent on the bioavailability of the fipronil and the half-life according to the zero-order model. Fipronil degradation rate appeared to be biphasic. Degradation fipronil ranged from 83 days (initial concentration = 978 ng g(-1); short-term experiment) to 200 days (initial concentration = 689 ng g(-1); long-term experiment). This an initial slower rate followed by a faster rate after 90 days of incubation may lead to shorter half-life than that calculated with the zero-order model. The sulfone derivative (an oxidation product) was the predominant metabolite, but the sulfide (a reduction product) and amide (a hydrolysis product) derivatives were also formed under non-sterile conditions after 120 days of incubation. The metabolites underwent further biodegradation, particularly the sulfone derivative. Bioavailability appears to affect fipronil degradation in soils with an effective capacity to adsorb fipronil (such as Ustoxs), while redox potential was important for the formation of metabolites. Despite the fine texture, more aerobic sites were present, thus favoring the formation of the sulfone metabolite over that of the sulfide metabolite. Therefore, microaggregation of Ustoxs, with high clay content, played a very important role in determining the types of metabolites formed. 相似文献
Wastewater samples from an anaerobic reactor were extracted with hexane and derivatized with diazomethane (method 1) and with acetic anidride (method 2). Gas chromatography with electron-capture detection (ECD) was employed for separating the parent compound and intermediates trichlorophenols (TCP) and dichlorophenols (DCP) which originated from the penta chlorophenol (PCP) degradation process. The relations between concentrations of PCP, TCP and DCP areas were linear in the range of concentrations of 0.2 to 8 mg/L and 0.025 mg/L to 5 mg/L for methods 1 and 2, respectively. The repeatability of the extraction methods was satisfactory, with variation coefficients lower than 11%. For method 1, at the fortification level of 0.2 mg/L, recovery of PCP, TCP, and DCP was 112%, 74% and 45%, respectively. For method 2, the corresponding recovery values at the fortification level of 0.1 mg/L were 91%, 93% and 103%, respectively. Storage of the frozen samples did not alter their PCP determination properties. The chromatographic methods adapted for chlorophenol determination in wastewater were suitable with relatively simple manipulation techniques. The obtained results were reproducible and allowed identification of intermediates formed during the PCP degradation process. 相似文献
This study aimed to evaluate the leaching of pesticides and the applicability of the Attenuation Factor (AF) Model to predict their leaching. The leaching of carbofuran, carbendazim, diuron, metolachlor, alpha and beta endosulfan and chlorpyrifos was studied in an Oxisol using a field experiment lysimeter located in Dom Aquino-Mato Grosso. The samples of percolated water were collected by rain event and analyzed. Chemical and physical soil attributes were determined before pesticide application to the plots. The results showed that carbofuran was the pesticide that presented a higher leaching rate in the studied soil, so was the one representing the highest contamination potential. From the total carbofuran applied in the soil surface, around 6% leached below 50 cm. The other pesticides showed lower mobility in the studied soil. The calculated values to AF were 7.06E-12 (carbendazim), 5.08E-03 (carbofuran), 3.12E-17 (diuron), 6.66E-345 (alpha-endosulfan), 1.47E-162 (beta-endosulfan), 1.50E-06 (metolachlor), 3.51E-155 (chlorpyrifos). AF Model was useful to classify the pesticides' potential for contamination; however, that model underestimated pesticide leaching. 相似文献
Here we review mechanisms and factors influencing contaminant exposure among terrestrial vertebrate wildlife. There exists a complex mixture of biotic and abiotic factors that dictate potential for contaminant exposure among terrestrial and semi-terrestrial vertebrates. Chemical fate and transport in the environment determine contaminant bioaccessibility. Species-specific natural history characteristics and behavioral traits then play significant roles in the likelihood that exposure pathways, from source to receptor, are complete. Detailed knowledge of natural history traits of receptors considered in conjunction with the knowledge of contaminant behavior and distribution on a site are critical when assessing and quantifying exposure. We review limitations in our understanding of elements of exposure and the unique aspects of exposure associated with terrestrial and semi-terrestrial taxa. We provide insight on taxa-specific traits that contribute, or limit exposure to, transport phenomenon that influence exposure throughout terrestrial systems, novel contaminants, bioavailability, exposure data analysis, and uncertainty associated with exposure in wildlife risk assessments. Lastly, we identify areas related to exposure among terrestrial and semi-terrestrial organisms that warrant additional research. 相似文献
Moss transplants of Tortula ruralis were used as active biomonitoring organisms as part of a monitoring study to assess the metals (Al, Cd, Cu, Cr, Fe, Ni, Pb, V and Zn) associated with ambient particles on mosses in Budapest, the capital town of Hungary. The moss samples were collected in a nature conservation area from a semi-arid sand grassland (Festucetum vaginatae danubiale), less than 1 month before transplantation. Moss cushions were exposed to pollution in Budapest during October–November 1993 and February–March 1994. In the study area, 16 sites were marked out as measuring sites, in accordance with the structure of the city. A similar stand was established in the Botanical Gardens of the Szent István University in Gödöll? as a control site. ICP-AES analysis of moss for metals showed the ability of Tortula ruralis to accumulate the metals under study. Control site showed lower impact in comparison to the other sites. 相似文献
Use of sewage sludge, a biological residue produced from sewage treatment processes in agriculture is an alternative disposal technique of waste. To study the usefulness of sewage sludge amendment for palak (Beta vulgaris var. Allgreen H-1), a leafy vegetable and consequent heavy metal contamination, a pot experiment was conducted by mixing sewage sludge at 20% and 40% (w/w) amendment ratios to the agricultural soil. Soil pH decreased whereas electrical conductance, organic carbon, total N, available P and exchangeable Na, K and Ca increased in soil amended with sewage sludge in comparison to unamended soil. Sewage sludge amendment led to significant increase in Pb, Cr, Cd, Cu, Zn and Ni concentrations of soil. Cd concentration in soil was found above the Indian permissible limit in soil at both the amendment ratios.
The increased concentration of heavy metals in soil due to sewage sludge amendment led to increases in heavy metal uptake and shoot and root concentrations of Ni, Cd, Cu, Cr, Pb and Zn in plants as compared to those grown on unamended soil. Accumulation was more in roots than shoots for most of the heavy metals. Concentrations of Cd, Ni and Zn were more than the permissible limits of Indian standard in the edible portion of palak grown on different sewage sludge amendments ratios. Sewage sludge amendment in soil decreased root length, leaf area and root biomass of palak at both the amendment ratios, whereas shoot biomass and yield decreased significantly at 40% sludge amendment. Rate of photosynthesis, stomatal conductance and chlorophyll content decreased whereas lipid peroxidation, peroxidase activity and protein and proline contents, increased in plants grown in sewage sludge-amended soil as compared to those grown in unamended soil.
The study clearly shows that increase in heavy metal concentration in foliage of plants grown in sewage sludge-amended soil caused unfavorable changes in physiological and biochemical characteristics of plants leading to reductions in morphological characteristics, biomass accumulation and yield. The study concludes that sewage sludge amendment in soil for growing palak may not be a good option due to risk of contamination of Cd, Ni and Zn and also due to lowering of yield at higher mixing ratio. 相似文献
In the present paper we investigated the effects of sub-lethal concentrations of Cu2+ in the growth and metabolism of Scenedesmus incrassatulus. We found that the effect of Cu2+ on growth, photosynthetic pigments (chlorophylls and carotenoids) and metabolism do not follow the same pattern. Photosynthesis was more sensitive than respiration. The analysis of chlorophyll a fluorescence transient shows that the effect of sub-lethal Cu2+ concentration in vivo, causes a reduction of the active PSII reaction centers and the primary charge separation, decreasing the quantum yield of PSII, the electron transport rate and the photosynthetic O2 evolution. The order of sensitivity found was: Growth > photosynthetic pigments content = photosynthetic O2 evolution > photosynthetic electron transport > respiration. The uncoupled relationship between growth and metabolism is discussed. 相似文献
The Siam weed, Chromolaena odorata (L.) King & Robinson, Family Asteraceae, was found to be a new Pb hyperaccumulator by means of field surveys on Pb soil and hydroponic studies. Plants from field collection accumulated 1377 and 4236mgkg(-1) Pb in their shoots and roots, respectively, and could tolerate soil Pb concentrations up to 100000 mgkg(-1) with a translocation factor of 7.62. Very low concentrations of Cd and Zn were found in plants collected from the field. Under nutrient solution culture condition, C. odorata from the contaminated site (CS) and from non-contaminated site (NCS) grew normally with all three metals (Pb, Cd, Zn) supplied. However, the relative growth rates of all treated plants decreased with increased metal concentrations. The percentage uptakes of Pb, Cd, and Zn by C. odorata increased with increasing metal concentrations. Pb concentration in shoots and roots reached its highest values (1772.3 and 60655.7mgkg(-1), respectively) at a Pb supply level of 10mgl(-1). While the maximum concentrations of Cd (0.5mgl(-1)) in shoots and roots of C. odorata were 102.3 and 1440.9mgkg(-1), and the highest concentrations of Zn (20mgl(-1)) were 1876.0 and 7011.8mgkg(-1), respectively. The bioaccumulation coefficients of Pb and Cd were greater than 1000. These results confirm that C. odorata is a hyperaccumulator which grows rapidly, has substantial biomass, wide distribution and has a potential for the phytoremediation of metal contaminated soils. 相似文献