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141.
This article describes the history of the Coachella Valley Multiple Species Habitat Conservation Plan (CVMSHCP), in the Riverside
County region of Southern California. When this collaborative biodiversity conservation planning process began, in 1994, local
participants and supporters had numerous factors working in their favor. Yet, as of April 2007, nearly 13 years had passed
without an approved plan. This is a common problem. Many multiple species habitat conservation plans now take more than a
decade to complete, and the long duration of these processes often results in negative consequences. The CVMSHCP process became
bogged down—despite strong scientific input and many political advantages—due to problematic relationships between the Plan’s
local supporters, its municipal signatory parties, and officials from the state and federal wildlife agencies, particularly
the regional office of the US Fish and Wildlife Service. This case study demonstrates the crucial importance of institutional
structures and relationships, process management, and timeliness in habitat conservation planning. We conclude by offering
several related recommendations for future HCP processes. 相似文献
142.
We demonstrate an approach for evaluating the level of protection attained using a variety of forms and levels of past, current,
and proposed Air Quality Standards (AQSs). The U.S. Clean Air Act requires the establishment of ambient air quality standards
to protect health and public welfare. However, determination of attainment of these standards is based on ambient pollutant
concentrations rather than prevention of adverse effects. To determine if a given AQS protected against adverse effects on
vegetation, hourly ozone concentrations were adjusted to create exposure levels that “just attain” a given standard. These
exposures were used in combination with a physiologically-based tree growth model to account for the interactions of climate
and ozone. In the evaluation, we used ozone concentrations from two 6-year time periods from the San Bernardino Mountains
in California. There were clear differences in the level of vegetation protection achieved with the various AQSs. Based on
modeled plant growth, the most effective standards were the California 8-hr average maximum of 70 ppb and a seasonal, cumulative,
concentration-weighted index (SUM06), which if attained, resulted in annual growth reductions of 1% or less. Least effective
was the 1-hr maximum of 120 ppb which resulted in a 7% annual reduction. We conclude that combining climate, exposure scenarios,
and a process-based plant growth simulator was a useful approach for evaluating effectiveness of current or proposed air quality
standards, or evaluating the form and/or level of a standard based on preventing adverse growth effects. 相似文献
143.
Membrane based treatment processes are very effective in removing salt from wastewater, but are hindered by calcium scale deposit formation. This study investigates the feasibility of removing calcium from treated sewage wastewater using accelerated seeded precipitation. The rate of calcium removal was measured during bench scale batch mode seeded precipitation experiments at pH 9.5 using various quantities of calcium carbonate as seed material. The results indicate that accelerated seeded precipitation may be a feasible option for the decrease of calcium in reverse osmosis concentrate streams during the desalination of treated sewage wastewater for irrigation purposes, promising decreased incidence of scaling and the option to control the sodium adsorption ratio and nutritional properties of the desalted water. It was found that accelerated seeded precipitation of calcium from treated sewage wastewater was largely ineffective if carried out without pre-treatment of the wastewater. Evidence was presented that suggests that phosphate may be a major interfering substance for the seeded precipitation of calcium from this type of wastewater. A pH adjustment to 9.5 followed by a 1-h equilibration period was found to be an effective pre-treatment for the removal of interferences. Calcium carbonate seed addition at 10 g l−1 to wastewater that had been pre-treated in this way was found to result in calcium precipitation from supersaturated level at 60 mg l−1 to saturated level at 5 mg l−1. Approximately 90% reduction of the calcium level occurred 5 min after seed addition. A further 10% reduction was achieved 30 min after seed addition. 相似文献
144.
Control of hazardous organic micropollutants is a challenging water quality issue. Dissolved humic organic matter (DOM) isolated from oxyhumolite coal mined in Bohemia was investigated as a complexation agent to remove polycyclic aromatic hydrocarbons (PAHs) and functionalized phenols from water by a two-stage process involving complexation and flocculation. After the formation of humic-contaminant complexes, ferric salts were added resulting in the precipitation and flocculation of the DOM and the associated pollutants. Flocculation experiments with ferric ion coagulants indicated that precipitation of oxyhumolite DOM together with the complexed contaminants occurred at lower ferric ion concentrations than with the reference DOM in acidic environments (pH approximately 3.5). The complexation-flocculation removal rates for non-reactive PAHs characterized by small localization energies of pi-electrons correlated well with the complexation constants. On the other hand, the combined complexation-flocculation removal rates for activated PAHs including trans-stilbene, anthracene and 9-methyl anthracene, as well as functionalized polar phenols, were higher than predicted from the complexation coefficients. Methodological studies revealed for the first time that the ferric ion coagulant contributed to enhanced removal rates, most probably due to ferric ion-catalyzed pollutant degradation resulting in oxidized products. 相似文献
145.
The widely used ECOSAR computer programme for QSAR prediction of chemical toxicity towards aquatic organisms was evaluated by using large data sets of industrial chemicals with varying molecular structures. Experimentally derived toxicity data covering acute effects on fish, Daphnia and green algae growth inhibition of in total more than 1,000 randomly selected substances were compared to the prediction results of the ECOSAR programme in order (1) to assess the capability of ECOSAR to correctly classify the chemicals into defined classes of aquatic toxicity according to rules of EU regulation and (2) to determine the number of correct predictions within tolerance factors from 2 to 1,000. Regarding ecotoxicity classification, 65% (fish), 52% (Daphnia) and 49% (algae) of the substances were correctly predicted into the classes "not harmful", "harmful", "toxic" and "very toxic". At all trophic levels about 20% of the chemicals were underestimated in their toxicity. The class of "not harmful" substances (experimental LC/EC(50)>100 mg l(-1)) represents nearly half of the whole data set. The percentages for correct predictions of toxic effects on fish, Daphnia and algae growth inhibition were 69%, 64% and 60%, respectively, when a tolerance factor of 10 was allowed. Focussing on those experimental results which were verified by analytically measured concentrations, the predictability for Daphnia and algae toxicity was improved by approximately three percentage points, whereas for fish no improvement was determined. The calculated correlation coefficients demonstrated poor correlation when the complete data set was taken, but showed good results for some of the ECOSAR chemical classes. The results are discussed in the context of literature data on the performance of ECOSAR and other QSAR models. 相似文献
146.
In many species reproduction and embryonic development have been shown to be sensitive to environmental contaminants. Understanding embryonic exposure to environmental contaminants is thus highly important. In this study concentrations of brominated flame retardants (BFRs) were measured in zebrafish eggs after parental exposure for 42 days via the diet. Zebrafish were exposed to two doses of eleven structurally-diverse BFRs. Eight BFRs were detected in the female zebrafish and maternal transfer to eggs was evident for all eight compounds. The highest concentrations in eggs were observed for hexabromocyclododecane (HBCD) and 2,4,4'-tribromodiphenyl ether (BDE 28), followed by 2,2',3,4,4',5',6-heptabromodiphenyl ether (BDE 183) and tetrabromobisphenol A 2,3-dibromopropyl ether (TBBPA DBPE). Five potential BFR metabolites were tentatively identified in female fish and maternal transfer was observed also for these compounds. The lipid adjusted concentrations in eggs were significantly higher than the concentrations in female fish for several of the BFRs. Further, the results showed a generally higher transfer in the lower exposure level and also indicated a dependency on the physico-chemical properties of the compounds. 相似文献
147.
Heeb NV Schweizer WB Mattrel P Haag R Gerecke AC Schmid P Zennegg M Vonmont H 《Chemosphere》2008,73(8):1201-1210
Hexabromocyclododecanes (HBCDs) are high production volume chemicals (>20000 ty(-1)) used as flame retardants for plastics and textiles. Lately, we reported on the stereoselective isomerization of beta-HBCDs. Herein we present insights into the mechanism and kinetics of (+)gamma- to (+)alpha- and of (-)gamma- to (-)alpha-HBCD isomerization. Only two of the six bromine atoms migrated, indicating that rearrangements of gamma- to alpha-HBCDs are regio- and stereoselective as well. The apparent first-order isomerization rate constants increased from 0.0013 to 0.0031 to 0.0070 min(-1) at 120, 130, and 140 degrees C, respectively, corresponding to half-lives of 540, 230, and 99 min. Thus, a thermal treatment of materials containing gamma-HBCDs at temperatures >100 degrees C may induce the formation of alpha-HBCDs and, hence, may alter the diastereomeric ratio of a HBCD mixture. The inversion of vicinal dibromides in like-configurations (RR/SS) prevailed, whereas unlike-configurations (RS/SR) were not affected. An intramolecular, stereoselective migration of neighboring bromine atoms via a four-center transition state would explain the observed stereoisomer pattern and first-order kinetics. Despite the fact that vicinal dibromides in HBCDs prefer synclinal (gauche) conformations, antiperiplanar (staggered) conformations are assumed to facilitate concerted 1.2-shifts of both bromine atoms. A conformation analysis revealed that under kinetic control, only those bromine atoms in the more flexible part of the molecules are migrating, whereas those in the conserved triple-turn motive were not affected. Thus, this structural motive, common to all alpha-, beta-, and gamma-HBCDs, is more rigid and less reactive than the flexible part, containing the reacting dibromides in like-configurations. 相似文献
148.
Modelling municipal solid waste generation: a review 总被引:1,自引:0,他引:1
The objective of this paper is to review previously published models of municipal solid waste generation and to propose an implementation guideline which will provide a compromise between information gain and cost-efficient model development. The 45 modelling approaches identified in a systematic literature review aim at explaining or estimating the present or future waste generation using economic, socio-demographic or management-orientated data. A classification was developed in order to categorise these highly heterogeneous models according to the following criteria--the regional scale, the modelled waste streams, the hypothesised independent variables and the modelling method. A procedural practice guideline was derived from a discussion of the underlying models in order to propose beneficial design options concerning regional sampling (i.e., number and size of observed areas), waste stream definition and investigation, selection of independent variables and model validation procedures. The practical application of the findings was demonstrated with two case studies performed on different regional scales, i.e., on a household and on a city level. The findings of this review are finally summarised in the form of a relevance tree for methodology selection. 相似文献
149.
Modelling of stable isotope fractionation by methane oxidation and diffusion in landfill cover soils 总被引:2,自引:0,他引:2
Mahieu K De Visscher A Vanrolleghem PA Van Cleemput O 《Waste management (New York, N.Y.)》2008,28(9):1535-1542
A technique to measure biological methane oxidation in landfill cover soils that is gaining increased interest is the measurement of stable isotope fractionation in the methane. Usually to quantify methane oxidation, only fractionation by oxidation is taken into account. Recently it was shown that neglecting the isotope fractionation by diffusion results in underestimation of the methane oxidation. In this study a simulation model was developed that describes gas transport and methane oxidation in landfill cover soils. The model distinguishes between (12)CH(4), (13)CH(4), and (12)CH(3)D explicitly, and includes isotope fractionation by diffusion and oxidation. To evaluate the model, the simulations were compared with column experiments from previous studies. The predicted concentration profiles and isotopic profiles match the measured ones very well, with a root mean square deviation (RMSD) of 1.7vol% in the concentration and a RMSD of 0.8 per thousand in the delta(13)C value, with delta(13)C the relative (13)C abundance as compared to an international standard. Overall, the comparison shows that a model-based isotope approach for the determination of methane oxidation efficiencies is feasible and superior to existing isotope methods. 相似文献
150.
Atmospheric emissions and attenuation of non-methane organic compounds in cover soils at a French landfill 总被引:1,自引:0,他引:1
Scheutz C Bogner J Chanton JP Blake D Morcet M Aran C Kjeldsen P 《Waste management (New York, N.Y.)》2008,28(10):1892-1908
In addition to methane (CH(4)) and carbon dioxide (CO(2)), landfill gas may contain more than 200 non-methane organic compounds (NMOCs) including C(2+)-alkanes, aromatics, and halogenated hydrocarbons. Although the trace components make up less than 1% v/v of typical landfill gas, they may exert a disproportionate environmental burden. The objective of this work was to study the dynamics of CH(4) and NMOCs in the landfill cover soils overlying two types of gas collection systems: a conventional gas collection system with vertical wells and an innovative horizontal gas collection layer consisting of permeable gravel with a geomembrane above it. The 47 NMOCs quantified in the landfill gas samples included primarily alkanes (C(2)-C(10)), alkenes (C(2)-C(4)), halogenated hydrocarbons (including (hydro)chlorofluorocarbons ((H)CFCs)), and aromatic hydrocarbons (BTEXs). In general, both CH(4) and NMOC fluxes were all very small with positive and negative fluxes. The highest percentages of positive fluxes in this study (considering all quantified species) were observed at the hotspots, located mainly along cell perimeters of the conventional cell. The capacity of the cover soil for NMOC oxidation was investigated in microcosms incubated with CH(4) and oxygen (O(2)). The cover soil showed a relatively high capacity for CH(4) oxidation and simultaneous co-oxidation of the halogenated aliphatic compounds, especially at the conventional cell. Fully substituted carbons (TeCM, PCE, CFC-11, CFC-12, CFC-113, HFC-134a, and HCFC-141b) were not degraded in the presence of CH(4) and O(2). Benzene and toluene were also degraded with relative high rates. This study demonstrates that landfill soil covers show a significant potential for CH(4) oxidation and co-oxidation of NMOCs. 相似文献