共查询到20条相似文献,搜索用时 48 毫秒
1.
Andrew T. Lambe Jennifer M. Logue Nathan M. Kreisberg Susanne V. Hering David R. Worton Allen H. Goldstein Neil M. Donahue Allen L. Robinson 《Atmospheric environment (Oxford, England : 1994)》2009,43(25):3941-3950
We present highly time-resolved measurements of organic molecular markers in downtown Pittsburgh, which are used to investigate sources contributing to atmospheric aerosols in the area. Two-hour average concentrations of condensed-phase and semivolatile organic species were measured using a Thermal Desorption Aerosol GC/MS (TAG). Concentrations for mobile source markers like hopanes had regular diurnal and day-of-week patterns. Pairing high time-resolved measurements with meteorological data helped identify contributions from known point sources for markers correlated with wind direction. Black carbon (BC), volatile organic compounds (VOCs) and organic molecular markers were apportioned to sources using the Chemical Mass Balance (CMB) and Positive Matrix Factorization (PMF) receptor models. Diesel and gasoline mobile source factors were identified as the main sources of BC in the downtown Pittsburgh area, contributing 67% and 20% of the study-average BC. 13% of the BC was associated with a source factor tentatively identified as an industrial or regional source. The high time resolution of the TAG has the potential to provide important new insight into source apportionment efforts using organic molecular marker measurements. 相似文献
2.
《Atmospheric environment (Oxford, England : 1994)》2007,41(1):103-118
To study the impact of emissions at an airport on local air quality, a measurement campaign at the Zurich airport was performed from 30 June 2004 to 15 July 2004. Measurements of NO, NO2, CO and CO2 were conducted with open path devices to determine real in-use emission indices of aircraft during idling. Additionally, air samples were taken to analyse the mixing ratios of volatile organic compounds (VOC). Temporal variations of VOC mixing ratios on the airport were investigated, while other air samples were taken in the plume of an aircraft during engine ignition. CO concentrations in the vicinity of the terminals were found to be highly dependent on aircraft movement, whereas NO concentrations were dominated by emissions from ground support vehicles. The measured emission indices for aircraft showed a strong dependence upon engine type. Our work also revealed differences from emission indices published in the emission data base of the International Civil Aviation Organisation. Among the VOC, reactive C2–C3 alkenes were found in significant amounts in the exhaust of an engine compared to ambient levels. Also, isoprene, a VOC commonly associated with biogenic emissions, was found in the exhaust, however it was not detected in refuelling emissions. The benzene to toluene ratio was used to discriminate exhaust from refuelling emission. In refuelling emissions, a ratio well below 1 was found, while for exhaust this ratio was usually about 1.7. 相似文献
3.
Analysis of air pollution data at a mixed source location using boosted regression trees 总被引:1,自引:0,他引:1
David C. Carslaw Paul J. Taylor 《Atmospheric environment (Oxford, England : 1994)》2009,43(22-23):3563-3570
This paper explores the use of boosted regression trees to draw inferences concerning the source characteristics at a location of high source complexity. Models are developed for hourly concentrations of nitrogen oxides (NOX) close to a large international airport. Model development is discussed and methods to quantify model uncertainties developed. It is shown that good explanatory models can be developed and further, allowing for interactions between model variables significantly improves the model fits compared with non-interacting models. Methods are used to determine which variables exert most influence over predicted concentrations and to explore the NOX dependency for each. Model predictions are used to estimate aircraft take-off contributions to total concentrations of NOX and determine how these predictions are affected by annual variations in meteorological conditions and runway use patterns. Furthermore, the results relating to the aircraft contributions to total NOX concentration are compared with those from a more detailed independent field campaign. Finally, we find empirical evidence that plumes from larger aircraft disperse more rapidly from the point of release compared with smaller aircraft. The reasons for this behaviour and the implications are discussed. 相似文献
4.
The longitudinal dependence of black carbon concentration on traffic volume in an urban environment 总被引:1,自引:0,他引:1
deCastro BR Wang L Mihalic JN Breysse PN Geyh AS Buckley TJ 《Journal of the Air & Waste Management Association (1995)》2008,58(7):928-939
The purpose of this study was to evaluate the effect of traffic volume on ambient black carbon (BC) concentration in an inner-city neighborhood "hot spot" while accounting for modifying effects of weather and time. Continuous monitoring was conducted for 12 months at the Baltimore Traffic Study site surrounded by major urban streets that together carry over 150,000 vehicles per day. Outdoor BC concentration was measured with an Aethalometer; vehicles were counted pneumatically on two nearby streets. Meteorological data were also obtained. Missing data were imputed and all data were normalized to a 5-min observational interval (n = 105,120). Time-series modeling accounted for autoregressively (AR) correlated errors. This study found that outdoor BC was positively correlated at a statistically significant level with neighborhood-level vehicle counts, which contributed at a rate of 66 +/- 10 (SE) ng/m3 per 100 vehicles every 5 min. Winds from the SW-S-SE quarter were associated with the greatest increases in BC (376-612 ng/m3). These winds would have entrained BC from Baltimore's densely trafficked central business district, as well as a nearby interstate highway. The strong influence of wind direction implicates atmospheric transport processes in determining BC exposure. Dew point, mixing height, wind speed, season, and workday were also statistically significant predictors. Background exposure to BC was estimated to be 905 ng/m3. The optimal, statistically significant representation of BC's autocorrelation was AR([1:6]) x 288 x 2016, where the short-term AR factor (lags 1-6) indicated that BC concentrations are correlated for up to 30 min, and the AR factors for lags 288 and 2016 indicate longer-term autocorrelations at diurnal and weekly cycles, respectively. It was concluded that local exposure to BC from mobile sources is substantially modified by meteorological and temporal conditions, including atmospheric transport processes. BC concentration also demonstrates statistically significant autocorrelation at several time scales. 相似文献
5.
《Atmospheric environment (Oxford, England : 1994)》2002,36(25):4057-4068
A particle measurement campaign was conducted in a suburban environment near a major road in Kuopio, Central Finland from 3 August to 9 September 1999. The mass concentrations of fine particles (PM2.5) were measured simultaneously at distances of 12, 25, 52 and 87 m from the centre of a major road at a height of 1.8 m, using identical samplers. The concentration measurements were conducted during 16 daytime hours (from 6.00 a.m. to 10.00 p.m.) for 27 days. Traffic flows and relevant meteorological parameters were measured on-site; meteorological measurements from a nearby synoptic weather station were also utilised. We also suggest a preliminary model for predicting the concentrations of PM2.5 and apply this model in order to analyse the measured data. The regionally and long-range transported contribution was evaluated on the basis of a semi-empirical mathematical model utilising as input values the daily sulphate, nitrate and ammonium measurements at the EMEP stations (Co-operative programme for monitoring and evaluation of the long-range transmission of air pollutants in Europe). The influence of primary vehicular emissions from the nearest roads was evaluated using a roadside emission and dispersion model, CAR-FMI, in combination with a meteorological pre-processing model, MPP-FMI. The contribution of non-exhaust particulate matter emissions (including resuspension of particulate matter from road surfaces) was estimated simply to be directly proportional to the concentrations originating from primary vehicular emissions. Comparison of the predicted results and measurements yields information on the relative importance of various source categories of the measured concentrations of PM2.5. The regionally and long-range transported contribution, the primary and non-exhaust vehicular emissions, and other sources were estimated to contribute on average 41±6%, 33±6% and 26±7% of the observed PM2.5 concentrations, respectively. The model presented could also be applied in other European cities for analysing the source contributions to measured fine particulate matter concentrations. 相似文献
6.
Joan Hrenko Novak D. Bruce Turner 《Journal of the Air & Waste Management Association (1995)》2013,63(6):570-575
The information presented in this paper is directed to air pollution scientists with an interest in applying air quality simulation models. RAM is the three letter designation for this efficient Gaussian-plume multiple-source air quality algorithm. RAM is a method of estimating short-term dispersion using the Gaussian steady-state model. This algorithm can be used for estimating air quality concentrations of relatively stable pollutants for averaging times from an hour to a day in urban areas from point and area sources. The algorithm is applicable for locations with level or gently rolling terrain where a single wind vector for each hour is a good approximation to the flow over the source area considered. Calculations are performed for each hour. Hourly meteorological data required are wind direction, wind speed, stability class, and mixing height. Emission information required of point sources consists of source coordinates, emission rate, physical height, stack gas volume flow and stack gas temperature. Emission information required of area sources consists of south-west corner coordinates, source area, total area emission rate and effective area source height. Computation time is kept to a minimum by the manner in which concentrations from area sources are estimated using a narrow plume hypothesis and using the area source squares as given rather than breaking down all sources to an area of uniform elements. Options are available to the user to allow use of three different types of receptor locations: 1 ) those whose coordinates are input by the user, 2) those whose coordinates are determined by thé model and are downwind óf significant point and area sources where maxima are likely to occur, and 3) those whose coordinates are determined by the model to give good area coverage of a specific portion of the region. Computation time is also decreased by keeping the number of receptors to a minimum. 相似文献
7.
Daily, weekly, and seasonal time courses of VOC concentrations in a semi-urban area near Barcelona 总被引:2,自引:0,他引:2
In order to study the daily, weekly, and seasonal patterns and possible origins of air concentrations of volatile organic compounds (VOCs), measurements were taken on a minute-by-minute basis with a PTR-MS in the vicinity of a highway in a semi-urban site near Barcelona. Four periods of the year were chosen and samples were taken under different meteorological conditions and at different phenological stages of the surrounding vegetation. None of the measured VOCs concentrations exceeded air-quality guidelines. The results showed that diurnal, weekly, and seasonal fluctuations in measured VOC concentrations depended on variations in the strength of sources, as well as on photochemical activity and meteorological conditions. There was a decrease in concentrations in most VOCs when mixing depth, photochemical destruction, and wind speed increased at midday. On the other hand, high values of some VOCs occurred at night when the strength of their sinks and the mixing layer decreased. Interestingly, in June, night emissions and concentration peaks of methanol and acetone occurred in periods with dew formation and no wind. VOCs related to anthropogenic emissions presented a weekly pattern of variation with a clear distinction being found between working days and the weekend. The seasonal variation showed higher levels in December for all VOCs, except for isoprene. The thinning of the mixing layer leading to greater concentrations of volatiles and lower wind speeds in winter could account for those higher VOC levels. Benzene and toluene originated mainly from anthropogenic emissions. The sources of acetaldehyde, methanol, and acetone appeared to be mainly biogenic and these compounds were the most abundant of all the measured VOCs. Isoprene concentration patterns suggest a predominantly anthropogenic origin in December and March and a mainly biogenic origin in June and October. All these data provide useful information on the dynamics of VOCs in an area where ozone levels in summer exceed quite often the standard protection thresholds for O3. 相似文献
8.
《Atmospheric environment(England)》1978,12(12):2279-2287
The transport of sulphur dioxide over distances of a few hundred kilometers is studied by measuring concentrations with a network consisting of fixed monitoring stations and a dynamic monitoring unit (moving laboratory). From the horizontal ground level measurements information about the vertical SO2 distribution is deduced. With a two-dimensional advection model the “effective mixing height” is estimated directly from the measured ground concentrations. A second quantity which will be denoted as “pollution height” is estimated from dynamically measured concentration and gas burden. For several case studies the introduced quantities are compared. In one of the cases the significance of these quantities was verified by aircraft measurements.The total flux of SO2, transported into the Netherlands from the major source areas in the surrounding countries, is determined. The results indicate that in general a major part of the transport takes place above the surface layer, not affecting the ground concentrations. When under special meteorological conditions all transport takes place within the surface layer, very high ground concentrations are found even at large distance from the source areas. 相似文献
9.
《Atmospheric environment (Oxford, England : 1994)》1999,33(19):3133-3142
Varimax rotation factor analysis was applied to monthly concentrations of elements in total suspended air particulate (TSP) matter in Ho Chi Minh City collected from December 1992 to November 1996, covering four dry/rainy seasons. Six pollution source types were revealed. Resuspended soil/road dust accounts for 74% of the TSP mass loading. Motor vehicles and a source which emits particulates containing arsenic account for 10% and 9%, respectively. There are three minor sources, namely, cement dust from the nearby construction site, road dust of local traffic origin and burning emissions. The contributions from these source were estimated with high uncertainties. The interpretation of sources was corroborated by studying source profiles and temporal variations of source contributions. The monthly variations of source contributions at the receptor were modelled by using source apportionment techniques. From the variation patterns, emission scenarios for burning, construction and motor vehicle sources were reproduced. Source contributions also exhibit seasonal variability induced by changes of meteorological conditions. No seasonal change was found for the As-containing particulates, suggesting a speculation on their origin as coal fly ash emitting from any local coal burning source. 相似文献
10.
Liu W Zhang J Kwon J Weisel C Turpin B Zhang L Korn L Morandi M Stock T Colome S 《Journal of the Air & Waste Management Association (1995)》2006,56(8):1196-1204
This paper presents the analysis of ambient air concentrations of 10 carbonyl compounds (aldehydes and ketones) measured in the yards of 87 residences in the city of Elizabeth, NJ, throughout 1999-2001. Most of these residences were measured twice in different seasons; the sampling duration was 48 hr each time. The authors observed higher concentrations for most of the measured carbonyl compounds on warmer days, reflecting larger contributions of photochemical reactions on warmer days. The estimated contributions of photochemical production varied substantially across the measured carbonyl compounds and could be as high as 60%. Photochemical activity, however, resulted in a net loss for formaldehyde. The authors used stepwise multiple linear regression models to evaluate the impact of traffic sources and meteorological conditions on carbonyl concentrations using the data collected on colder days (with lower photochemical activities). They found that the concentrations of formaldehyde, acetaldehyde, acrolein, propionaldehyde, crotonaldehyde, benzaldehyde, glyoxal, and methylglyoxal significantly decreased with increasing distance between a measured residence and one or more major roadways. They also found significant negative associations between concentrations for most of the measured carbonyl compounds and each of the following meteorological parameters: mixing height, wind speed, and precipitation. 相似文献
11.
Molini M. Patel Steven N. Chillrud Juan C. Correa Marian Feinberg Yair Hazi K.C. Deepti Swati Prakash James M. Ross Diane Levy Patrick L. Kinney 《Atmospheric environment (Oxford, England : 1994)》2009,43(32):4975-4981
Relatively little is known about exposures to traffic-related particulate matter at schools located in dense urban areas. The purpose of this study was to examine the influences of diesel traffic proximity and intensity on ambient concentrations of fine particulate matter (PM2.5) and black carbon (BC), an indicator of diesel exhaust particles, at New York City (NYC) high schools. Outdoor PM2.5 and BC were monitored continuously for 4–6 weeks at each of 3 NYC schools and 1 suburban school located 40 km upwind of the city. Traffic count data were obtained using an automated traffic counter or video camera. BC concentrations were 2–3 fold higher at urban schools compared with the suburban school, and among the 3 urban schools, BC concentrations were higher at schools located adjacent to highways. PM2.5 concentrations were significantly higher at urban schools than at the suburban school, but concentrations did not vary significantly among urban schools. Both hourly average counts of trucks and buses and meteorological factors such as wind direction, wind speed, and humidity were significantly associated with hourly average ambient BC and PM2.5 concentrations in multivariate regression models. An increase of 443 trucks/buses per hour was associated with a 0.62 μg/m3 increase in hourly average BC at an NYC school located adjacent to a major interstate highway. Car traffic counts were not associated with BC. The results suggest that local diesel vehicle traffic may be important sources of airborne fine particles in dense urban areas and consequently may contribute to local variations in PM2.5 concentrations. In urban areas with higher levels of diesel traffic, local, neighborhood-scale monitoring of pollutants such as BC, which compared to PM2.5, is a more specific indicator of diesel exhaust particles, may more accurately represent population exposures. 相似文献
12.
Background, Aims and Scope This research attempted to identify the dominant factors simultaneously affecting the airborne concentrations of five air
pollutants with principal component analysis and to determine the meteorologically related parameters that cause severe air-pollution
events. According to the definition of subPSI and PSI values through the U.S. EPA, the historical raw data of five criteria
air pollutants, SO2, CO, O3, PM10 and NO2, were calculated as daily subPSI values. In addition to the airborne concentrations,
this study simultaneous collected the surface meteorological parameters of the Taipei meteorological station, established
by the Central Weather Bureau.
Methods Principal component analysis was conducted to screen severe air pollution scenarios for five air pollutants: SO2, CO, O3,
PM10 and NO2. The concentrations of various air pollutants measured at 17 air-quality stations in northern Taiwan from 1995
to 2001 were transformed into daily subPSI values. The correlation analysis of the five air pollutants and four meteorological
parameters (wind speed, temperature, mixing height and ventilation rate) were included in this research. After screening severe
air pollution scenarios, this study recognized the synoptic patterns easily causing the severe air-pollution events.
Results and Discussion Analytical results showed that the eigenvalues of the first two principal components for SO2, CO, O3, PM10 and NO2 were greater
than 1. The first component of five air pollutants explained 64, 64, 67, 76 and 63% of subPSI variance for SO2, CO, O3, PM10
and NO2, respectively. Only the correlation coefficient of NO2 and CO had statistically significant positive values (0.82);
other pollutant pairs presented medium (0.4 to 0.7) or low (0 to 0.4) positive values. The correlation coefficients for air
pollutants and three meteorological parameters (wind speed, mixing height and ventilation index) were medium or low negative
values. In northern Taiwan, spring was most likely induced high concentrations and the component scores of the first component
for SO2, CO, PM10 and NO2; summer was the worst season that caused high O3 episodes. Consequently, the analytical results
of factor loadings for the first principal component and emission inventory of various sources revealed that mobile sources
were dominant factors affecting ambient air quality in northern Taiwan.
Conclusion According to the results of principal component analysis for the five air pollutants, the first two of 17 components were
cited as major factors and explained 71% of subPSI variance. Based on the inventory of NOx emissions and the isopleth diagram
of factor loading for the first component, mobile sources in the southwest Taipei City accounted for the highest factor loading
values and emission inventory values. Synoptic analysis and principal component analysis demonstrated that three types of
weather patterns (high-pressure recirculation, prefrontal warm sector and the southwesterly wind system) easily caused the
severe air-pollution scenarios. In summary, if severe air-pollution days occurred, the average meteorological parameters experienced
adverse conditions for diffusing air pollutants; that is, the average values of wind speed, mixing height and ventilation
index were lower than 2.1 ms-1, 360 m and 800 m2s-1, respectively. If one of the three synoptic patterns were to occur in
combination with adverse meteorological conditions, severe air-pollution events would be developed.
Recommendation and Outlook By utilizing synoptic patterns, this work found three weather systems easily caused severe air-pollution events over northern
Taiwan. Analytical results showed, respectively, the wind speed and mixing height were less than 2.1 m/s and 360 m during
severe air-pollution events. 相似文献
13.
This paper describes a diffusion model designed to permit calculation of seasonal average concentrations of an air pollutant, in particular, sulfur dioxide. The calculations can encompass multiple sources and multiple receptors. For each receptor location the model sums the effect of all sources over a wide range of meteorological conditions. Input data include source pollutant emissions, source configuration and location, receptor location, and meteorological data expressed as a joint frequency distribution of wind direction, wind speed, stability. To determine the model’s accuracy, concentration estimates for St. Louis, Mo., are compared with measured SO2 concentrations. The overall correlation with observed data is satisfactory. A computer program to handle the numerous calculations was written in Fortran IV language for use on an IBM 1130 computer. 相似文献
14.
Mukund Bapna Ramya Sunder Raman S. Ramachandran T. A. Rajesh 《Environmental science and pollution research international》2013,20(3):1617-1631
This study characterizes over 5 years of high time resolution (5 min), airborne black carbon (BC) concentrations (July 2003 to December 2008) measured over Ahmedabad, an urban region in western India. The data were used to obtain different time averages of BC concentrations, and these averages were then used to assess the diurnal, seasonal, and annual variability of BC over the study region. Assessment of diurnal variations revealed a strong association between BC concentrations and vehicular traffic. Peaks in BC concentration were co-incident with the morning (0730 to 0830, LST) and late evening (1930 to 2030, LST) rush hour traffic. Additionally, diurnal variability in BC concentrations during major festivals (Diwali and Dushera during the months of October/November) revealed an increase in BC concentrations due to fireworks displays. Maximum half hourly BC concentrations during the festival days were as high as 79.8 μg m?3. However, the high concentrations rapidly decayed suggesting that local meteorology during the festive season was favorable for aerosol dispersion. A multiple linear regression (MLR) model with BC as the dependent variable and meteorological parameters as independent variables was fitted. The variability in temperature, humidity, wind speed, and wind direction accounted for about 49% of the variability in measured BC concentrations. Conditional probability function (CPF) analysis was used to identify the geographical location of local source regions contributing to the effective BC measured (at 880 nm) at the receptor site. The east north-east (ENE) direction to the receptor was identified as a major source region. National highway (NH8) and two coal-fired thermal power stations (at Gandhinagar and Sabarmati) were located in the identified direction, suggesting that local traffic and power plant emissions were likely contributors to the measured BC. 相似文献
15.
Weili Liu Jaymin Kwon Clifford Weisel Barbara Turpin Lin Zhang 《Journal of the Air & Waste Management Association (1995)》2013,63(8):1196-1204
Abstract This paper presents the analysis of ambient air concentrations of 10 carbonyl compounds (aldehydes and ketones) measured in the yards of 87 residences in the city of Elizabeth, NJ, throughout 1999–2001. Most of these residences were measured twice in different seasons; the sampling duration was 48 hr each time. The authors observed higher concentrations for most of the measured carbonyl compounds on warmer days, reflecting larger contributions of photochemical reactions on warmer days. The estimated contributions of photochemical production varied substantially across the measured carbonyl compounds and could be as high as 60%. Photochemical activity, however, resulted in a net loss for formaldehyde. The authors used stepwise multiple linear regression models to evaluate the impact of traffic sources and meteorological conditions on carbonyl concentrations using the data collected on colder days (with lower photochemical activities). They found that the concentrations of formal-dehyde, acetaldehyde, acrolein, propionaldehyde, crotonaldehyde, benzaldehyde, glyoxal, and methylglyoxal significantly decreased with increasing distance between a measured residence and one or more major roadways. They also found significant negative associations between concentrations for most of the measured carbonyl compounds and each of the following meteorological parameters: mixing height, wind speed, and precipitation. 相似文献
16.
LaRosa LE Buckley TJ Wallace LA 《Journal of the Air & Waste Management Association (1995)》2002,52(1):41-49
Black carbon (BC) was measured every 5 min for two years (May 1998-May 2000) inside and immediately outside a northern Virginia house (suburban Washington, DC) occupied by two nonsmokers. Two aethalometers, which measure BC by optical transmission through a quartz fiber tape, were employed indoors and outdoors. Meteorological parameters were obtained on an hourly basis from nearby Dulles airport. Indoor activities were recorded to identify indoor sources such as combustion activities, which occurred 9% of the time during the first year and 4% of the time during the second year. At times without indoor sources, indoor/outdoor BC ratios averaged 0.53 in the first year and 0.35 in the second year. The main outdoor source of BC was the general regional background, contributing 83-84% of the total during each of the two years. Morning rush hour traffic contributed 8-9% of the total BC. An evening peak in the fall and winter, thought to include contributions from wood burning, was responsible for approximately 8% of the annual average BC concentration. The main indoor sources of BC were cooking and candle burning, contributing 16 and 31%, respectively, of the annual average indoor concentrations in the two years. Relative humidity (RH) affected the outdoor aethalometer in both years. An artifact associated with the tape advance was noted for the aethalometer, but a correction factor was developed that reduced the associated error by a factor of 2. 相似文献
17.
Maureen Simonds Malachowski Steven P. Levine Gary Herrin Robert C. Spear Michael Yost Zhou Yi 《Journal of the Air & Waste Management Association (1995)》2013,63(5):673-682
Open path Fourier transform infrared (OP-FTIR) spectroscopy is a new air monitoring technique that can be used to measure concentrations of air contaminants in real or near-real time. OP-FTIR spectroscopy has been used to monitor workplace gas and vapor exposures, emissions from hazardous waste sites, and to track emissions along fence lines. This paper discusses a statistical process control technique that can be used with air monitoring data collected with an OP-FTIR spectrometer to detect departures from normal operating conditions in the workplace or along a fence line. Time series data, produced by plotting consecutive air sample concentrations in time, were analyzed. Autocorrelation in the time series data was removed by fitting dynamic models. Control charts were used with the residuals of the model fit data to determine if departures from defined normal operating conditions could be rapidly detected. Shewhart and exponentially weighted moving average (EWMA) control charts were evaluated for use with data collected under different room air flow and mixing conditions. Under rapidly changing conditions the Shewhart control chart was able to detect a leak in a simulated process area. The EWMA control chart was found to be more sensitive to drifts and slowly changing concentrations in air monitoring data. The time series and statistical process control techniques were also applied to data obtained during a field study at a chemical plant. A production area of an acrylonitrile, 1,3-butadiene, and styrene (ABS) polymer process was monitored in near-real time. Decision logics based on the time series and statistical process control technique introduced suggest several applications in workplace and environmental monitoring. These applications might include signaling of an alarm or warning, increasing levels of worker respiratory protection, or evacuation of a community, when gas and vapor concentrations are determined to be out-of-control. 相似文献
18.
Howard M. Segal 《Journal of the Air & Waste Management Association (1995)》2013,63(10):1054-1056
Analysis of vertical temperature soundings at Los Angeles International Airport (LAX) shows that a conservative height of the inversion base for pollutant containment purposes is 490 ft (150 m). This altitude is considerably less than the 3000 ft (914 m) pollution containment altitude assumed by the EPA in preparing their emission inventory for the airport. (Figure 1.) After correcting the EPA emission inventory to reflect a real world inversion height, the emission inventory for aircraft at Los Angeles International Airport is estimated to be approximately 50% less. Aircraft thus become a less significant pollution source and consideration should be given to relaxing engine emission control requirements accordingly. This paper examines current emission control philosophy, which according to the EPA should be based upon the significance of the particular polluting source. The problem of accounting for above ground aircraft emissions is then considered. Daily inversion height data are then used to determine a realistic vertical containment altitude for aircraft emissions. Problems in obtaining good inversion data are described. Finally, aircraft emissions at Los Angeles International Airport are adjusted to reflect real world inversion conditions on those days when the inversion height is low enough to influence significantly air pollution levels. Recommendations are made for additional research leading to possible change to NOx emission control requirements for aircraft. 相似文献
19.
J.M. Logue K.E. Huff-Hartz A.T. Lambe N.M. Donahue A.L. Robinson 《Atmospheric environment (Oxford, England : 1994)》2009,43(39):6205-6217
High time-resolved (HTR) measurements can provide significant insight into sources and exposures of air pollution. In this study, an automated instrument was developed and deployed to measure hourly concentrations of 18 gas-phase organic air toxics and 6 volatile organic compounds (VOCs) at three sites in and around Pittsburgh, Pennsylvania. The sites represent different source regimes: a site with substantial mobile-source emissions; a residential site adjacent to a heavily industrialized zone; and an urban background site. Despite the close proximity of the sites (less than 13 km apart), the temporal characteristic of outdoor concentrations varied widely. Most of the compounds measured were characterized by short periods of elevated concentrations or plume events, but the duration, magnitude and composition of these events varied from site to site. The HTR data underscored the strong role of emissions from local sources on exposure to most air toxics. Plume events contributed more than 50% of the study average concentrations for all pollutants except chloroform, 1,2-dichloroethane, and carbon tetrachloride. Wind directional dependence of air toxic concentrations revealed that emissions from large industrial facilities affected concentrations at all of the sites. Diurnal patterns and weekend/weekday variations indicated the effects of the mixing layer, point source emissions patterns, and mobile source air toxics (MSATs) on concentrations. Concentrations of many air toxics were temporally correlated, especially MSATs, indicating that they are likely co-emitted. It was also shown that correlations of the HTR data were greater than lower time resolution data (24-h measurements). This difference was most pronounced for the chlorinated pollutants. The stronger correlations in HTR measurements underscore their value for source apportionment studies. 相似文献
20.
Li WW Cardenas N Walton J Trujillo D Morales H Arimoto R 《Journal of the Air & Waste Management Association (1995)》2005,55(3):352-364
The causes for evening low-wind PM10 and PM2.5 peaks at Sunland Park, NM, were investigated by using wind sector analysis and by assessing relationships between PM loadings and meteorological parameters through canonical ordination analysis. Both PM10 and PM2.5 concentrations during the evening hours accounted for approximately 50% of their respective 24-hr averages, and the PM10 was mainly composed of coarse material (PM10-2.5 amounted to 77% of PM10). A wind sector analysis based on data from three surface meteorological monitoring stations in the region narrowed the potential source region for PM10 and PM2.5 to an area within a few kilometers south of Sunland Park. Canonical ordination analysis confirmed that the peak frequently occurred under stable conditions with weak southerly winds. Chemical analyses of PM showed that elemental and organic carbon (EC and OC, respectively) dominate PM2.5 and inorganic elements dominate PM10-2.5. The combined data for EC/OC, geologic elements, and various trace elements indicate that under low wind and stable conditions, traffic-related PM emissions (motor vehicle exhausts and re-suspended road dust) from the south of the site are the most likely sources for the evening PM10 and PM2.5 peaks. 相似文献