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41.
Nicholas A. Martin Edward J. Leming Malcolm H. Henderson Robert P. Lipscombe John K. Black Scott D. Jarvis 《Atmospheric environment (Oxford, England : 1994)》2010,44(28):3378-3385
There is a requirement to verify the performance of sorbent-based passive or active samplers and to extend their use, where possible, to monitor volatile organic compounds (VOCs) that are known to be photochemical ozone pre-cursors or are relevant to the activities of the petrochemical industry. We report measurements of the 14-day diffusive uptake rates for the VOCs: i-butane (2-methyl propane), n-butane, i-pentane (2-methyl butane), n-pentane, n-hexane, benzene, toluene, and m-xylene (at environmental level concentrations) for industry standard axial samplers (Perkin–Elmer-type samplers) containing the sorbents Carbopack-X, -Z, -B or Tenax-TA. We also present data on back-diffusion, blank levels, and storage for the above sorbents, and describe the simultaneous use of the sorbent Carbopack-X for pumped sampling of certain VOCs. The results were obtained by dosing samplers in a controlled atmosphere test facility (CATFAC) operating under well-defined conditions of concentration, nominal temperature of 20 °C, wind speed of 0.5 m s?1, and relative humidities of 0% and 80%. Field measurements were also obtained to provide supplementary data to support the laboratory study. Results are compared to existing published data, where these are available. 相似文献
42.
43.
Nicholas A. Azzolina Edward F. Neuhauser John T. Finn Todd R. Crawford Krista A. Anders Melissa A. Doroski 《Environmental Forensics》2014,15(3):225-233
This study characterized organic compounds found in New York State manufactured gas plant (MGP) coal tar vapors using controlled laboratory experiments from four separate MGP sites. In addition, a limited number of deep (0.3–1.2 m above coal tar) and shallow (1.2–2.4 m above coal tar) soil vapor samples were collected above the in situ coal tar source at three of these sites. A total of 29 compounds were consistently detected in the laboratory-generated coal tar vapors at 50°C, whereas 24 compounds were detected at 10°C. The compounds detected in the field sample results were inconsistent with the compounds found in the laboratory-generated samples. Concentrations of compounds in the shallow soil vapor sample were either non-detectable or substantially lower than those found in deeper samples, suggesting attenuation in the vadose zone. Laboratory-generated data at 50°C compared the (% non-aromatic)/(% aromatic) ratio and indicated that this ratio may provide good discrimination between coal tar vapor and common petroleum distillates. 相似文献
44.
Miller JL Miller MJ de Vlaming V Larsen K Smith E Reece K 《Environmental monitoring and assessment》2009,150(1-4):333-349
A number of procedures have been developed to assess toxic effects on the early life stages of salmonid fish. In this study 13 rainbow trout embryo development relatively short-term (7 to 90 day) procedures were reviewed. Three 7-day methods from the published literature and three modifications developed at AQUA-Science (A-S) were evaluated in the laboratory. Based on that evaluation, A-S methods were selected for screening surface water samples (A-S 1) collected in the Sacramento River watershed (California) and for conducting toxicity identification evaluations (TIE) to identify cause(s) of toxicity. Test control performance, test sensitivity, and reference toxicant response variability in the A-S 1 were superior to those in commonly used freshwater toxicity testing methods. The incidence of Sacramento River watershed samples resulting in a notable decrease in embryo development was very low. Of 260 samples screened only 16 (6%) resulted in statistically significant inhibition of embryo development. Of the 16 toxic samples, nine caused minimal (less than 20% abnormal development) and four marginal (less than 30%) toxicity. Samples collected from the agriculture-dominated Colusa Basin Drain and rangeland/forest-dominated Battle Creek on June 16, 2005 caused significant toxicity. TIE procedures indicated that cationic chemicals were the primary cause of toxicity. Metals analysis did not reveal concentrations sufficient to inhibit embryo development, so the most probable cause of toxicity in the two samples was cationic chemicals (perhaps surfactants?) or metals that were not included in the analytical screening. 相似文献
45.
Roy Mauldin Edward Kosciuch Fred Eisele Greg Huey David Tanner Steve Sjostedt Don Blake Gao Chen Jim Crawford Douglas Davis 《Atmospheric environment (Oxford, England : 1994)》2010,44(4):572-581
Measurements of OH, H2SO4, and MSA at South Pole (SP) Antarctica were recorded as a part of the 2003 Antarctic Chemistry Investigation (ANTCI 2003). The time period 22 November, 2003–2 January, 2004 provided a unique opportunity to observe atmospheric chemistry at SP under both natural conditions as well as those uniquely defined by a solar eclipse event. Results under natural solar conditions generally confirmed those reported previously in the year 2000. In both years the major chemical driver leading to large scale fluctuations in OH was shifts in the concentration levels of NO. Like in 2000, however, the 2003 observational data were systematically lower than model predictions. This can be interpreted as indicating that the model mechanism is still missing a significant HOx sink reaction(s); or, alternatively, that the OH calibration source may have problems. Still a final possibility could involve the integrity of the OH sampling scheme which involved a fixed building site. As expected, during the peak in the solar eclipse both NO and OH showed large decreases in their respective concentrations. Interestingly, the observational OH profile could only be approximated by the model mechanism upon adding an additional HOx radical source in the form of snow emissions of CH2O and/or H2O2. This would lead one to think that either CH2O and/or H2O2 snow emissions represent a significant HOx radical source under summertime conditions at SP. Observations of H2SO4 and MSA revealed both species to be present at very low concentrations (e.g., 5 × 105 and 1 × 105 molec cm?3, respectively), but similar to those reported in 2000. The first measurements of SO2 at SP demonstrated a close coupling with the oxidation product H2SO4. The observed low concentrations of MSA appear to be counter to the most recent thinking by glacio-chemists who have suggested that the plateau's lower atmosphere should have elevated levels of MSA. We speculate here that the absence of MSA may reflect efficient atmospheric removal mechanisms for this species involving either dynamical and/or chemical processes. 相似文献
46.
Edward J. Lillis Dexter Young 《Journal of the Air & Waste Management Association (1995)》2013,63(10):1015-1018
The various aspects of two similar but indeed different air pollution problems are discussed. Both fugitive emissions (industrial) and fugitive dust emissions represent problems affecting attainment of national standards. Both are difficult to quantify so as to determine the relative magnitude of the problem. Both have been generally overlooked in the past in relation to developing an effective and widespread air pollution control program. Both problems will generally require the use of non-conventional air pollution control measures. Both are also becoming the subject of more intensive investigation as more knowledge is being gathered to implicate such emissions as significant air pollution problems. 相似文献
47.
EPA's “Third Symposium on Fabric Filters for Particle Collection,” held in Tucson December 5 and 6, 1977, emphasized the results obtained from both laboratory and field experience. Data from selected new and/or continuing research programs as well as from new pilot and field applications are reviewed. 相似文献
48.
Mercer LD Szpiro AA Sheppard L Lindström J Adar SD Allen RW Avol EL Oron AP Larson T Liu LJ Kaufman JD 《Atmospheric environment (Oxford, England : 1994)》2011,45(26):4412-4420
BACKGROUND: Epidemiological studies that assess the health effects of long-term exposure to ambient air pollution are used to inform public policy. These studies rely on exposure models that use data collected from pollution monitoring sites to predict exposures at subject locations. Land use regression (LUR) and universal kriging (UK) have been suggested as potential prediction methods. We evaluate these approaches on a dataset including measurements from three seasons in Los Angeles, CA. METHODS: The measurements of gaseous oxides of nitrogen (NOx) used in this study are from a "snapshot" sampling campaign that is part of the Multi-Ethnic Study of Atherosclerosis and Air Pollution (MESA Air). The measurements in Los Angeles were collected during three two-week periods in the summer, autumn, and winter, each with about 150 sites. The design included clusters of monitors on either side of busy roads to capture near-field gradients of traffic-related pollution. LUR and UK prediction models were created using geographic information system (GIS)-based covariates. Selection of covariates was based on 10-fold cross-validated (CV) R(2) and root mean square error (RMSE). Since UK requires specialized software, a computationally simpler two-step procedure was also employed to approximate fitting the UK model using readily available regression and GIS software. RESULTS: UK models consistently performed as well as or better than the analogous LUR models. The best CV R(2) values for season-specific UK models predicting log(NOx) were 0.75, 0.72, and 0.74 (CV RMSE 0.20, 0.17, and 0.15) for summer, autumn, and winter, respectively. The best CV R(2) values for season-specific LUR models predicting log(NOx) were 0.74, 0.60, and 0.67 (CV RMSE 0.20, 0.20, and 0.17). The two-stage approximation to UK also performed better than LUR and nearly as well as the full UK model with CV R(2) values 0.75, 0.70, and 0.70 (CV RMSE 0.20, 0.17, and 0.17) for summer, autumn, and winter, respectively. CONCLUSION: High quality LUR and UK prediction models for NOx in Los Angeles were developed for the three seasons based on data collected for MESA Air. In our study, UK consistently outperformed LUR. Similarly, the 2-step approach was more effective than the LUR models, with performance equal to or slightly worse than UK. 相似文献
49.
The fractal branching of an arborescent sponge 总被引:4,自引:0,他引:4
Edward R. Abraham 《Marine Biology》2001,138(3):503-510
The fractal properties of specimens of a planar branching sponge Raspailia inaequalis (Porifera, Demospongiae) were determined by analysing digitised photographs. The specimens, collected from a single site
in northeastern New Zealand, had a wide range of morphology. Three different fractal methods were used: box counting; a method
that gives the scaling of branch length with distance from the base of the fan; and an allometric analysis of the dependence
of frontal area on specimen size. All three approaches gave a similar value for the fractal dimension. The conjecture that
the specimens have a fractal branching structure is consistent with the results of a Horton analysis of their branching pattern.
There is a significant relationship between fractal dimension and number of fingers, which implies that a simple count of
the number of fingers is as useful for discriminating between individuals as the more complex fractal analysis. Using this
relation, sponges from a site with less water movement are inferred to have a lower fractal dimension. This result is in agreement
with the predictions of the Kaandorp model of sponge growth.
Received: 13 March 2000 / Accepted: 11 October 2000 相似文献
50.
Edward J. Phlips F J. Aidridge C. Hanlon 《Journal of the American Water Resources Association》1994,30(2):229-238
ABSTRACT: A 17-year record of chlorophyll a at eight limnetic sampling stations was used to evaluate putative changes in the trophic status of Lake Okeechobee, a shallow polymictic lake located in the subtropical environment of South Florida. Significant spatial differences were observed in the temporal patterns and variability of chlorophyll a concentrations. The highest chlorophyll a values were found in the northern and northwestern regions of the lake. The center of the lake, subject to high levels of non-algal suspended solids, exhibited relatively low chlorophyll a values and coefficient of variation. The lowest chlorophyll a values were observed at the southernmost sampling station in the lake. This was also the station that showed a significant upward trend in annual mean chlorophyll a values over the 17-year period of record. Examination of the relationship between chlorophyll a and three key environmental variables (i.e., total phosphorus concentration, phosphorus loading, and lake stage) revealed significant correlations at two out of the eight stations. The overall results of this study indicate that spatial and temporal disparities in the distribution and dynamics of chlorophyll a in Lake Okeechobee mandate more temporally and spatially intense approaches to the evaluation of trophic state than used in previous studies. 相似文献