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771.
Kinetic evaluation of H2S and NH3 biofiltration for two media used for wastewater lift station emissions 总被引:1,自引:0,他引:1
Jones KD Martinez A Maroo K Deshpande S Boswell J 《Journal of the Air & Waste Management Association (1995)》2004,54(1):24-35
In this study, biofiltration using a natural wood chip medium and a commercial biofiltration medium was evaluated for the removal of moderate concentrations of hydrogen sulfide (H2S) (up to 100 parts per million by volume [ppmv]) in the presence of significant concentrations of ammonia (NH3). These levels were chosen as representative of wastewater lift station emissions in the Brownsville, TX, area. NH3-removing portions of the biofilms may compete with H2S-removing portions and inhibit H2S removal. H2S process removal efficiencies for the commercial and natural media ranged from 90 to 96% depending on inlet loading and media type and bed height. Kinetic analysis of the H2S removal process followed apparent first-order reaction behavior. The average first-order reaction rates were 0.03 sec(-1) for the commercial medium and 0.09 sec(-1) for the natural medium. Pressure drops across the columns ranged from 0.41 in. H2O/ft for the commercial medium to 1.41 in. H2O/ft for the natural medium. NH3 gas levels of up to 80 ppmv did not affect the H2S removal process efficiency, and calculated kinetic rate constants for H2S removal remained almost the same. The NH3 gas also was removed simultaneously with the H2S up to 98% removal efficiency by the commercial medium. 相似文献
772.
Young AL Giesy JP Jones PD Newton M 《Environmental science and pollution research international》2004,11(6):359-370
BACKGROUND: In 1996, the Committee on the Assessment of Wartime Exposure to Herbicides in Vietnam of the National Academy of Sciences' Institute of Medicine (IOM) issued a report on an exposure model for use in epidemiological studies of Vietnam veterans. This exposure model would consider troop locations based on military records; aerial spray mission data; estimated ground spraying activity; estimated exposure opportunity factors; military indications for herbicide use; and considerations of the composition and environmental fate of herbicides, including changes in the TCDD content of the herbicides over time, the persistence of TCDD and herbicides in the environment, and the degree of likely penetration of the herbicides into the ground. When the final report of the IOM Committee was released in October 2003, several components of the exposure model envisioned by the Committee were not addressed. These components included the environmental fate of the herbicides, including changes in the TCDD content over time, the persistence of TCDD and herbicides in the environment, and the degree of likely penetration of herbicides into the ground. This paper is intended to help investigators understand better the fate and transport of herbicides and TCDD from spray missions, particularly in performing epidemiological studies. METHODS: This paper reviews the published scientific literature related to the environmental fate of Agent Orange and the contaminant, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), and discusses how this affected the potential exposure to TCDD of ground troops in Vietnam. Specifically, the mechanisms of dissipation and degradation as they relate to environmental distribution and bioavailability are addressed. RESULTS: The evaluation of the spray systems used to disseminate herbicides in Vietnam showed that they were capable of highly precise applications both in terms of concentrations sprayed and area treated. Research on tropical forest canopies with leaf area indices (a measure of foliage density) from 2 to 5 indicated that the amount of herbicide and associated TCDD reaching the forest floor would have been between 1 and 6% of the total aerial spray. Studies of the properties of plant surface waxes of the cuticle layer suggested that Agent Orange, including the TCDD, would have dried (i.e., be absorbed into the wax layer of the plant cuticle) upon spraying within minutes and could not be physically dislodged. Studies of Agent Orange and the associated TCDD on both leaf and soil surface have demonstrated that photolysis by sunlight would have rapidly decreased the concentration of TCDD, and this process continued in shade. Studies of 'dislodgeable foliar residues' (DFR, the fraction of a substance that is available for cutaneous uptake from the plant leaves) showed that only 8% of the DFR was present 1 hr after application. This dropped to 1% of the total 24 hrs after application. Studies with human volunteers confirmed that after 2 hrs of saturated contact with bare skin, only 0.15-0.46% of 2,4,5-T, one of the phenoxy acetic acid compounds that was an active ingredient of Agent Orange, entered the body and was eliminated in the urine. CONCLUSIONS: The prospect of exposure to TCDD from Agent Orange in ground troops in Vietnam seems unlikely in light of the environmental dissipation of TCDD, little bioavailability, and the properties of the herbicides and circumstances of application that occurred. Photochemical degradation of TCDD and limited bioavailability of any residual TCDD present in soil or on vegetation suggest that dioxin concentrations in ground troops who served in Vietnam would have been small and indistinguishable from background levels even if they had been in recently treated areas. Laboratory and field data reported in the literature provide compelling evidence on the fate and dislodgeability of herbicide and TCDD in the environment. This evidence of the environmental fate and poor bioavailability of TCDD from Agent Orange is consistent with the observation of little or no exposure in the veterans who served in Vietnam. Appreciable accumulation of TCDD in veterans would have required repeated long-term direct skin contact of the type experienced by United States (US) Air Force RANCH HAND and US Army Chemical Corps personnel who handled or otherwise had direct contact with liquid herbicide, not from incidental exposure under field conditions where Agent Orange had been sprayed. 相似文献
773.
Bioremediation of coal tar PAH in soils using biodiesel 总被引:5,自引:0,他引:5
The addition of biodiesel together with nitrate and phosphate to soil containing coal tar, in laboratory and field experiments, resulted in degradation of coal tar polycyclic aromatic hydrocarbons (PAH) that was not apparent when the nutrients alone were added. The addition of motor diesel fuel instead of biodiesel was also tested. Over the 55 days of the field and laboratory experiments, the biodiesel resulted in an increased degradation of naphthalene in the coal tar by 52% and 85%, respectively, and motor diesel resulted in increased depletions of 85% and 96%, respectively. Other PAH containing up to four rings were depleted to lesser extents. The increases in PAH biodegradation by the diesel treatments were ascribed to tar solubilisation and dispersion thereby increasing the PAH bioavailability. The ready biodegradability and low phytotoxicity of biodiesel suggest that it may be suitable as a novel treatment for the bioremediation of coal tar contaminated soils. 相似文献
774.
Alan M. Jones Roy M. Harrison 《Atmospheric environment (Oxford, England : 1994)》2006,40(40):7733-7741
Proposals from the European Commission have raised the possibility that Member States may be able to subtract the concentrations of natural components of airborne particulate matter from measured concentrations when evaluating compliance with EU Limit Values. By applying the pragmatic mass closure model [Harrison et al., 2003. A pragmatic mass closure model for airborne particulate matter at urban background and roadside sites. Atmospheric Environment 37, 4927–4933] to chemical composition data for PM10, it has been possible to estimate the concentrations of natural sea salt, strongly bound water and secondary organic carbon (which is assumed wholly biogenic) to the measured mass of PM10. Because of the difficulty in distinguishing between natural and anthropogenic crustal dusts, the contribution of natural windblown dust and soil has not been accounted for. When the natural components are estimated for two urban and one rural site in the UK, the long-term mean PM10 concentration is reduced by between 5.2 and 7.3 μg m−3. The number of exceedences of the 50 μg m−3 24-h limit value falls dramatically from 54 to 21 (from a total of 291 days) at an urban street canyon site, 7 to 3 (n=292 days) at an urban background site and from 8 to 0 (n=241 days) at a rural site when using gravimetric PM10 concentrations. The calculations have also been performed using PM10 concentrations measured by TEOM increased by a factor of 1.3 as recommended by the European Commission as an interim means of estimating gravimetric equivalency, and the number of exceedences of the 24-h limit value fell from 92 to 47 (from a total of 291 days) at the urban street canyon site, from 11 to 3 (n=292 days) at the urban background site and from 6 to 3 (n=241) at the rural site. Clearly, therefore, application of this proposed measure would make a very major difference to the likelihood of compliance or otherwise with the 24-h limit value for PM10. 相似文献
775.
Evidence of extensive leaching losses of nutrients, particularly of K, suggest that loss of 137Cs by foliar leaching could be considerable and could stimulate further root uptake and redistribution of 137Cs in plants. This study investigated the foliar leaching of 137Cs from two deciduous graminoid species, Eriophorum vaginatum and Scirpus caespitosus and one evergreen shrub, Erica tetralix. Plants were labelled with 137Cs via the roots and subjected to a leaching treatment in August and November and changes in both leachate and plant 137Cs activity were determined. Leaching losses were significantly reduced in November compared with August in the deciduous species, but not in the evergreen E. tetralix. A reduction in the total activity of 137Cs of leached plants was observed not only in leaves but also in stems and roots in some instances, suggesting that 137Cs from these organs had been redistributed to replenish that lost by leaching from the leaves. The data suggest that leaching losses were greater from older and senescent leaves than from younger leaves of E. vaginatum. The extent to which this is an accurate representation of foliar leaching of field-grown plants by rainfall, and the likely fate of 137Cs lost by foliar leaching are discussed. 相似文献
776.
Polynuclear aromatic hydrocarbons in the United Kingdom environment: a preliminary source inventory and budget 总被引:60,自引:0,他引:60
This paper presents the first attempt to quantify the production, cycling, storage and loss of PAHs in the UK environment. Over 53 000 tonnes of sigmaPAHs (sum of 12 individual compounds) are estimated to reside in the contemporary UK environment, with soil being the major repository. If soils at contaminated sites are included, this estimate increases dramatically. Emission of PAHs to the UK atmosphere from primary combustion sources are estimated to be greater than 1000 tonnes sigmaPAHs per annum, with over 95% coming from domestic coal combustion, unregulated fires and vehicle emissions. It is estimated that approximately 210 tonnes of sigmaPAH are delivered to terrestrial surfaces each year via atmospheric deposition. Therefore, inputs of PAHs to the UK atmosphere outweigh the outputs by a factor of over 4. This may be explained by enhanced particulate deposition near point sources, PAH degradation in the atmosphere and transport away from the UK with prevailing winds. Disposal of waste residues is estimated to contribute a further 1000 tonnes of sigmaPAH per year to the terrestrial environment. It is illustrated that the use of creosote has the potential to release considerable quantities of PAHs to the UK environment. Temporal trends in PAH cycling are then considered. There is good evidence to suggest that air concentrations and fluxes to the UK surface are now lower than at any time throughout this century. Nonetheless, the UK sigmaPAH burden is still increasing at the present time, principally through retention by soils. However, there are marked differences in the behaviour of individual compounds: there is evidence, for example, that phenanthrene concentrations in soils have declined since the 1960s, although soil concentrations of benzo[a]pyrene and other heavier PAHs have continued to increase through this century. Volatilisation of low molecular weight PAHs accumulated in soils over previous decades may be making an important contribution to the current atmospheric burden. The major uncertainties identified by data on this budget are: (1) the lack of PAH concentrations in some environmental matrices; (2) the possible importance of contaminated soils as a major repository and source of PAHs; (3) the lack of emission data (especially vapour phase releases) for some PAH sources; (4) the importance of biodegradation and volatilisation as loss mechanisms for low molecular weight PAHs in soils; and (5) the importance of creosote use in the PAH cycle. 相似文献
777.
Cadmium in cereal grain and herbage from long-term experimental plots at Rothamsted, UK 总被引:1,自引:0,他引:1
Crop samples harvested and stored from three long-term agricultural experiments started in the 1840-1850s at Rothamsted Experimental Station (UK) have been analysed recently for Cd. Increased Cd burden in the soils of the experiments, which have had a range of treatments, originates mainly from atmospheric deposition. Soils treated with farmyard manure (FYM) or, in some cases, applications of phosphate fertilisers, have increased Cd levels. Herbage, wheat and barley grain from the three experiments were analysed by neutron activation analysis (NAA) and graphite furnace atomic absorption spectrometry (GFAAS). Samples were bulked for groups of years between 1860 and 1986, from variously treated plots in each experiment (control or 'nil' treatment, P-fertilised, FYM-amended, NPK-fertilised-limed and unlimed). There were marked differences in Cd concentrations between treatments. For example, uptake of Cd into herbage was greater where P fertiliser had been applied than not, and was greater from unlimed than limed soils. Offtake of Cd (mg ha(-1) year(-1)) was affected by large differences in yield and probably also by other factors. These include changes in botanical composition in the permanent grassland experiment; cultivar changes in the wheat and barley experiments; changes in soil organic matter and soil pH of some plots; changes in atmospheric deposition of Cd through time. All of these potentially confounding factors make the interpretation of results complicated. It is concluded, however, that, with one exception, there is little evidence of a long-term increase in crop Cd concentrations at Rothamsted. 相似文献
778.
Effect of chlorsulfuron on growth of submerged aquatic macrophyte Potamogeton pectinatus (sago pondweed) 总被引:3,自引:0,他引:3
Research has been conducted on the effect of chlorsulfuron on non-target plants but little information is available on its effects on aquatic macrophytes. Potamogeton pectinatus (sago pondweed) is an ecologically important submerged aquatic macrophyte found in freshwater bodies. Many species of wildlife use this plant as a food source. The objective of this study was to measure the phytotoxic effects of chlorsulfuron on sago pondweed. P. pectinatus plants were exposed to chlorsulfuron at 0, 0.25, 0.50, 1.0, or 2.0 ppb, in an environmental growth chamber. Plants exposed to 0.25 ppb chlorsulfuron showed a reduction in length (76%), number of leaves (50%), and number of stems (50%), compared to control plants. A reduction (47%) was also observed in the length of stems produced by plants treated with > or = 0.50 ppb chlorsulfuron. Significant reductions in wet and dry weights, and increased mortality were observed on treatments with > or = 1.0 ppb chlorsulfuron. 相似文献
779.
Assessment of organic contaminant fate in waste water treatment plants. I: Selected compounds and physicochemical properties 总被引:1,自引:0,他引:1
An extensive and comprehensive literature review has been conducted for compounds which we hypothesise could be present in sludge and maintain their integrity following application to agricultural land. The following compounds have been selected for review; chlorinated paraffins, quintozene, brominated diphenyl ethers, polychlorinated naphthalenes, polydimethylsiloxanes, chloronitrobenzenes, and a range of biologically active and pharmaceutical compounds. All have received interest as a result of their persistence and/or toxicity in environmental media. Physicochemical property information has also been compiled and/or calculated. In this way, an accompanying paper will attempt to predict compound fate in waste water treatment plants (WWTPs) and assess likely transfers from soil/plants to grazing livestock. These papers describe a first attempt to predict the fate of these classes of compounds in the environment and prioritise those of greatest concern. 相似文献
780.
Jones JM Hogrefe C Henry RF Ku JY Sistla G 《Journal of the Air & Waste Management Association (1995)》2005,55(1):13-19
The updated regulatory framework for demonstrating that future 8-hr ozone (O3) design values will be at or below the National Ambient Air Quality Standards (NAAQS) provides guidelines for the development of a State Implementation Plan (SIP) that includes methods based on photochemical modeling and analytical techniques. One of the suggested approaches is the relative reduction factor (RRF) for estimating the efficacy of emission reductions. In this study, the sensitivity of model-predicted responses towards emission reductions to the choice of meteorology and chemical mechanisms was examined. While the different modeling simulations generally were found to be in agreement on whether predicted future-year design values would be above or below the NAAQS for 8-hr O3 at a majority of the monitoring locations in the eastern United States, differences existed for a small percentage of monitors (approximately 6.4%). Another issue investigated was the ability of the attainment demonstration procedure to predict changes in monitored O3 design values. A retrospective analysis was performed by comparing predicted O3 design values from model simulations using emission estimates for 1996 and 2001 with monitored O3 design values for 2001. Results indicated that an average gross error of approximately 5 ppb was present between modeled and observed design values and that, at approximately 27% of all sites, model-predicted and observed design values disagreed as to whether the design value was above or below the NAAQS. Retrospective analyses such as the one presented in this study can provide valuable insights into the strengths and limitations of modeling and analysis techniques used to predict future design values over time periods of a decade or more for the purpose of developing SIPs. Furthermore, such analyses could provide avenues for improvement and added confidence in the use of the RRF approach for addressing attainment of the NAAQS. 相似文献