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511.
Three analytical methods have been evaluated for the determination of volatile organic compounds in water. These techniques have been subsequently applied to the study of a trade effluent discharge problem.  相似文献   
512.
The City of Los Angeles Hyperion Treatment Plant (HTP) (California) converted its anaerobic digesters to thermophilic operation to produce Class A biosolids. Phase IV tests demonstrated compliance of a two-stage, continuous-batch process with Alternative 1 of U.S. Environmental Protection Agency 40 CFR Part 503 (U.S. EPA, 1993), which defines the time-temperature requirement for batch treatment (T > or = 56.3 degrees C at 16-h holding). Fecal coliforms, Salmonella sp., viable helminth ova, and enteric viruses were not detected in biosolids in the postdigestion train, including the truck-loading facility and the farm for land application as the last points of plant control where compliance is to be demonstrated. The same results were achieved during Phase V tests, after lowering the second-stage holding temperature to 52.6 degrees C to reduce the elevated methyl mercaptan production that was observed during Phase IV. Hence, the Phase V process complied with Alternative 3 of 40 CFR Part 503. Currently, HTP operates its digesters under the same conditions as tested in Phase V. In 2003, monthly monitoring of the biosolids at the truck-loading facility and the farm for land application demonstrated consistent compliance with Alternative 3.  相似文献   
513.
This risk assessment on 1,1,2-trichloroethane (T112) was carried out specifically for the marine environment, according to the methodology laid down in the EU risk assessment Regulation (1488/94) and the Guidance Document of the EU New and Existing Substances Regulation (TGD, 1997). The study consists of the collection and evaluation of data on effects and environmental concentrations from analytical monitoring programs in large rivers and estuaries in the North Sea area. The risk is indicated by the ratio of the "predicted environmental concentrations" (PEC) and the "predicted no effect concentrations" (PNEC) for the marine aquatic environment. In total, 22 studies for fish, 45 studies for invertebrates and 9 studies for algae have been evaluated. Both acute and chronic toxicity studies have been taken into account and the appropriate assessment factors have been used to define a PNEC value of 300 µg/l. Most of the available monitoring data apply to rivers and estuaries and were used to calculate PECs. The most recent data (1991-1995) support a typical PEC of 0.01 µg T112/l water and a worst case PEC of 5 µg T112/l water. The calculated PEC/PNEC ratios give a safety margin of 60 to 30,000 between the predicted no effect concentration and the exposure concentration. Additional evaluation of environmental fate and bioaccumulation characteristics showed that no concern is expected for food chain accumulation.  相似文献   
514.
515.
The general profile of the pollution of drinking water, originating from groundwater, by nitrates, chloride and arsenic, in the Prefecture of Thessaloniki, was studied in this project. Samples (tap water) were collected from 52 areas-villages of the Prefecture, during a period of 6 months. The analytical results were related to certain points on the map of the area, thus producing coloured representations of the Prefecture, according to the concentration of the corresponding pollutant. The statistical analysis of the data led to some conclusions concerning the causes of pollution and the relation of the concentrations to certain physico-chemical parameters. Nitrate concentration of samples collected from two specific regions were especially high, sometimes above the highest permitted level. A limited number of samples (13.5%) contained arsenic concentrations above the imminent EC drinking water limit (10 ppb). The majority of the tap water samples, collected from areas along the seashore contained increased concentrations of chloride ions, which is a clear indication of seawater intrusion into the related aquifers.  相似文献   
516.
Holling proposed a four-phase conceptual model of ecosystem dynamics that includes exploitation, conservation, and destructive and renewal components to explain the failure of many natural resource management schemes. The model is drawn as a sideways figure-eight i.e. . There are two dimensions in this model, connectivity (abscissa) and the amount of capital stored in the system (ordinate). This conceptual model has been suggested as a guide to thinking about the impact of climate change on biodiversity, but the two dimensions are insufficient and the alignment of the figure-eight model is problematic when compared with actual data. Kay has adjusted the dimensions of the figure-eight model and renamed the abscissa as exergy stored and the ordinate as exergy consumed. We realign the original figure-eight model, labeling the abscissa as carbon stored and the ordinate as nutrients, such that the relative values of both axes are in qualitative agreement with data from four different studies. This new alignment is then shown to fit relatively well with Holling's original labels. This revision of the figure-eight model brings Holling's model into agreement with observations and provides insight into the linkages between biodiversity and climate change.  相似文献   
517.
This risk assessment on 1,2-dichloroethane (EDC) was carried out specifically for the marine environment, according to the methodology laid down in the EU risk assessment Regulation (1488/94) and the Guidance Document of the EU New and Existing Substances Regulation (TGD, 1997). The study consists of the collection and evaluation of data on effects and environmental concentrations from analytical monitoring programs in large rivers and estuaries in the North Sea area. The risk is indicated by the ratio of the "predicted environmental concentrations" (PEC) and the "predicted no effect concentrations" (PNEC) for the marine aquatic environment. In total, 21 studies for fish, 17 studies for invertebrates and 7 studies for algae have been evaluated. Both acute and chronic toxicity studies have been taken into account and the appropriate assessment factors have been used to define a PNEC value of 1100 µg/l. Most of the available monitoring data apply to rivers and estuaries and were used to calculate PECs. The most recent data (1991-1995) support a typical PEC of 0.5 µg EDC/l and a worst case PEC of 6.4 µg EDC/l. The calculated PEC/PNEC ratios give a safety margin of 170 to 2200 between the predicted no effect concentration and the exposure concentration. Additional evaluation of environmental fate and bioaccumulation characteristics showed that no concern is expected for food chain accumulation.  相似文献   
518.
This risk assessment on chloroform was carried out specifically for the marine environment, according to the methodology laid down in the EU risk assessment Regulation (1488/94) and the Guidance Document of the EU New and Existing Substances Regulation (TGD, 1997). The study consists of the collection and evaluation of data on effects and environmental concentrations from analytical monitoring programs in large rivers and estuaries in the North Sea area. The risk is indicated by the ratio of the "predicted environmental concentrations" (PEC) and the "predicted no effect concentrations" (PNEC) for the marine aquatic environment. In total, 23 studies for fish, 17 studies for invertebrates and 10 studies for algae have been evaluated. Both acute and chronic toxicity studies have been taken into account and the appropriate assessment factors have been used to define a typical PNEC value of 72 µg/l. Due to limitations of the studies evaluated, a worst PNEC of 1 µg/l could also be used. Most of the available monitoring data apply to rivers and estuaries and were used to calculate PECs. The most recent data (1991-1995) support a typical PEC of 0.2 µg chloroform per litre of water and a worst case PEC of 5 to 11.5 µg chloroform per litre of water. The calculated PEC/PNEC ratios give a safety margin of 6 to 360 between the predicted no effect concentration and the exposure concentrations. A worst case ratio, however, points to a potential risk for sensitive species. Refinement of the assessment is necessary by looking for more data. Additional evaluation of environmental fate and bioaccumulation characteristics showed that no concern is expected for food chain accumulation.  相似文献   
519.
This risk assessment on tetrachloroethylene (PER) was carried out specifically for the marine environment, according to the methodology laid down in the EU risk assessment Regulation (1488/94) and the Guidance Document of the EU New and Existing Substances Regulation (TGD, 1997). The study consists of the collection and evaluation of data on effects and environmental concentrations from analytical monitoring programs in large rivers and estuaries in the North Sea area. The risk is indicated by the ratio of the "predicted environmental concentrations" (PEC) and the "predicted no effect concentrations" (PNEC) for the marine aquatic environment. In total, 18 studies for fish, 13 studies for invertebrates and 8 studies for algae have been evaluated. Both acute and chronic toxicity studies have been taken into account and the appropriate assessment factors have been used to define a PNEC value of 51 µg/l. Most of the available monitoring data apply to rivers and estuary waters and were used to calculate PECs. The most recent data (1991-1995) support a typical PEC of 0.2 µg PER/l water and a worst case PEC of 2.5 µg PER/l water. The calculated PEC/PNEC ratios give a safety margin of 20 to 250 between the predicted no effect concentration and the exposure concentration. Additional evaluation of environmental fate and bioaccumulation characteristics showed that no concern is expected for food chain accumulation.  相似文献   
520.
Activated charcoal, Amberlite XAD-2 and Amberlite XAD-7 were evaluated for the adsorption of epichlorohydrin and ethylene chlorohydrin from air followed by desorption with solvent. Ethylene chlorohydrin was found to be unstable on activated charcoal in the presence of carbon disulfide. Recoveries from XAD-2 were low, and XAD-7 was found to be the best adsorbent for the sampling of these compounds from air.  相似文献   
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