Patricia E. Korsog

Measurements of SOx, NOx and aerosol species on Bermuda

During August 1982 and January and February 1983, General Motors Research Laboratories operated an air monitoring site on the southwest coast of Bermuda. The data show that the levels of the NOx and SOx species reaching Bermuda are determined by the direction of the air flow. The highest levels of sulfate (mean = 4.0 μg m−3), nitric acid (126 ppt) and other species are observed when air masses arrive from the northeastern United States while the lowest levels (sulfate = 1.1 μg m−3; nitric acid = 41 ppt) occur during air flow from the SE direction. With westerly air flow, increases in many anthropogenic constituents such as particulate sulfate, lead, elemental carbon, sulfur dioxide, nitrogen dioxide, nitric acid and ozone are observed. These species are generally the lowest during SE winds which bring high concentrations of soil- and crustal-related aerosol species. The source of this crustal material appears to be the Sahara Desert. On the average, the levels of anthropogenic constituents are higher in winter because of frequent intrusions of N American air masses. Conversely, the levels of crustal materials are higher in summer when the SE flow is more prevalent.

Measurements of sulfur oxides, nitrogen oxides, haze and fine particles at a rural site on the Atlantic coast

During August, 1982 and January and February, 1983, General Motors Research Laboratories operated air monitoring sites on the Atlantic Coast near Lewes, Delaware and 1250 km to the east on the southwest coast of Bermuda. The overall purpose of this project was to study the transformations of the principal acid precipitation precursors, NO x and SO x species, as they transport under conditions not complicated by emissions from local sources. In this paper, the measurements of gas and particulate species from Lewes are described and the composition and sources of sulfate aerosol, which is the most important haze-producing species, are investigated. On the average, the total suspended particulate (TSP) concentration was 27.9 μg/m3 while the PM10 (mass of particles with a diameter less than or equal to 10 μm) concentration was 22.0 μg/m3 or 79 percent of the TSP. The PM10 consisted of 6.1 μg/m3 of coarse particles (CPM, diameter = 2.5 − 10μm) and 15.9 μg/m3 of fine particles (FPM, diameter < 2.5 μm). On a mas...

A characterization of the principal PM-10 species in Claremont (summer) and Long Beach (fall) during SCAQS

Abstract As part of the Southern California Air Quality Study (SCAQS), General Motors Research Laboratories made comprehensive air quality measurements during the summer of 1987 in Claremont, CA, and during the fall of 1987 in Long Beach, CA. These locations are typically in the areas of highest pollution for the respective seasons. Claremonts air quality during the summer was characterized by high concentrations of photochemically produced pollutants including ozone (O3), nitric acid (HNO3), particulate nitrate (NO3−) and particulate organic carbon (OC). The highest concentrations of these species were experienced during the daytime sampling period (0600–1800 h) and were associated with transport from the western part of the basin. Long Beachs air quality during the fall was characterized by frequent periods of air stagnation that resulted in high concentrations of primary pollutants including PM-10, OC and elemental carbon (EC) as well as particulate NO3−. Night-time levels of most constituents exceeded daytime levels due to poorer night-time dispersion conditions. At Claremont, OC and NO3− compounds account for 52% of the PM-10 while at Long Beach they account for 67% of the PM-10. On the average, there appears to be sufficient particulate ammonium (NH4+) to completely neutralize the nitrate and acidic sulfates. Significant artifact OC was detected and corrected for at both sites. At Claremont the artifact accounted for 21% of the uncorrected OC mass and 13% at Long Beach. Because of NO3− and NH4+ losses on Teflon filters, the measured PM-10 and fine particulate mass (FPM) had to be corrected. This correction amounted to increasing the average measured FPM and PM-10 by 17 and 12%, respectively, at Claremont, and 8 and 6%, respectively, at Long Beach.

Evidence for the transformation of polycyclic organic matter in the atmosphere

Abstract The ratios of 1-nitropyrene and hydroxynitropyrenes to inert marker species (fine particulate lead, selenium, and elemental carbon) were considerably higher at a remote site on Bermuda than in Delaware. The results suggested that these nitroaromatic POM are formed in atmospheric reactions. The ratio of benzo( a )pyrene to marker species was not significantly different at the two sites. This result did not reflect the expected loss of BaP in atmospheric photochemical reactions.

Relationships between fine particulate species, gaseous pollutants and meteorological parameters in detroit

Abstract During June, July and August 1981, General Motors Research Laboratories operated a comprehensive air-quality monitoring site in Detroit. Parameters monitored included the criteria pollutants, meteorological variables and the organic carbon, elemental carbon and sulfate content of the fine and coarse fractions of inhalable particulates (diameter ⩽ 15 μm). In addition, air parcel trajectories were used to compute the length of time air parcels spent in various upwind emission-source areas before arriving in Detroit. The data were analyzed using varimax-rotated principal component analysis. The results show that midwestern sources upwind of southeastern (SE) Michigan are responsible for most of the observed sulfate, which accounted for about 50% of the fine particle fraction. Significant amounts of ozone, particulate organic carbon and sulfur dioxide are also transported in from upwind sources. Local emissions dominate the concentrations of coarse particulate mass, elemental carbon, carbon monoxide and non-methane hydrocarbons. Important local sources exist for nitrogen oxides, sulfur dioxide and particulate organic carbon.

The influence of local and regional sources on the concentration of inhalable particulate matter in southeastern Michigan

During June, July and August 1981, General Motors Research Laboratories collected daily fine (FPM = diameter < 2.5 μm) and coarse (CPM = ⩾ 2.5 μm, ⩽ 15 μm) particulate samples at four sites in southeastern Michigan. Dichotomous air samplers were located at a downtown Detroit site (DSC), a heavily industrialized site in Dearborn (RR), a suburban downwind site in Warren (TC), and an upwind site in Ann Arbor (AA) which behaved like a rural site. Analyses of the spatial variations of the various particulate components revealed the following results. (1) At all four sites the FPM was dominated by regional influences rather than local sources. The site in the industrial sector, RR, had the largest impact of local sources, but even at this site the local influences appeared to be smaller than the regional ones. (2) The regional influences were most pronounced on the sulfate (SO2−4) levels which accounted for the largest fraction (40–50 %) of the FPM. Evidence suggests that much of the observed SO2−4 was transported into the southeastern Michigan study area and was formed primarily via photochemically initiated reactions. (3) Organic carbon (OC) compounds were the second most abundant FPM species accounting for 20–40 % of the mass. OC seems to be controlled by both local and regional organic carbon influences. Vehicular emissions and possibly secondary reactions appear to affect the OC concentrations at the four sites. (4) Elemental carbon (EC), a relatively minor FPM species, appears to be dominated at DSC, RR and TC by local emissions. The EC levels at AA appear to be representative of the regional background as they were similar to the levels observed in rural areas far removed from local sources. (5) The CPM was dominated by local sources. At RR, however, the crustal-like material could only account for 18% of the CPM. This indicates that other local, noncrustal sources dominated the CPM levels at RR.

AN EXAMINATION OF URBAN OZONE TRENDS IN THE NORTHEASTERN U.S. (1973-1983) USING A ROBUST STATISTICAL METHOD

Abstract Stringent volatile organic compounds (VOC) control measures for both mobile and stationary sources have been introduced in the U.S. in an attempt to reduce ambient concentrations of ozone (O 3 ). Despite the expense of billions of dollars to implement these measures, the impact on O 3 air quality is still unknown, and most major metropolitan areas are still in violation of the daily 1-h National Ambient Air Quality Standard for O 3 of 120 ppb. This study was initiated to examine the trends of O 3 from 1973 to 1983 at eight major population centers in the northeastern U.S. using a robust statistical method. The effects of the late 1970s change in O 3 calibration methodology and meteorology on these trends were also examined. The 75th percentile was shown to be a good statistic for determining trends and was used for analysis of the trends before and after the calibration change was applied. The surface temperature and upper air temperature variables were found to be the best predictors of O 3 behavior. Two regression procedures, the fixed-range and fixed-value techniques, were performed to remove the variability of meteorological conditions conducive to high O 3 (i.e. O 3 > 80 ppb). Finally, a robust, nonparametric statistical procedure, which does not require specific statistical assumptions to be met, was used for each set of estimates derived above. The results of these analyses show there has been a decrease of a few ppb on a yearly basis for the majority of the sites.

Estimates of the contributions of sources to inhalable particulate concentrations in detroit

Abstract For a one-week period during July 1981, samples of fine (diameter −3 . A major contribution from a sulfate source, which appears to be coal combustion, was identified. This source is estimated to account for about 50% of the fine mass. Small contributions (less than 10%) from motor vehicles, incineration, fugitive dust and fuel oil combustion were also identified. Organic carbon, not associated with any of the above sources, also accounted for ≈ 10%. The coarse fraction which averaged 25.8 μg m −3 was dominated by crustal material which accounted for about two-thirds of the coarse material. Significant contributions were also identified from motor vehicles (mostly due to reintrained road dust) and iron and steel industry emissions.

Multivariate statistical analyses of air quality data and bacterial mutagenicity data from ambient aerosols

Abstract As part of the 1982 Detroit Summer Air Pollution Study, the relationships between the mutagenicity of ambient aerosols and other air quality components were examined. Thirty-one samples of total suspended particulate matter collected at a site in central Detroit were extracted with dichloromethane and fractionated into 16 fractions using thin layer chromatography. The individual fractions were then examined for mutagenicity by the Ames test using tester strains TA98, TA98NR and TA98DNP6. The results showed that most of the mutagenicity (64%) was contained in four polar fractions, and one polar fraction accounted for 34% of the total activity. Using principal component and multiple linear regression analyses, we examined relationships between the mutagenicity in each fraction and the air quality and meteorological variables. Overall, the measured observables explained about 40% of the mutagenicity variance. A single component containing SO2 emissions was the most important component as it explained 20% of the mutagenicity variance. The component containing motor vehicle emissions explained 13% of the mutagenicity variance. Photochemically-initiated reactions appear to play a minor role as this component explained an insignificant amount of the mutagenicity variance. The liquid water content of the ambient aerosol explained a significant part of the mutagenic variance of several fractions.

Ozone control strategies based on the ratio of volatile organic compounds to nitrogen oxides

The 1990 Clean Air Act Amendments require states with O3 nonattainment areas to adopt regulations to enforce reasonable available control technologies (RACT) for NOX stationary sources by November 1992. However, if the states can demonstrate that such measures will have an adverse effect on air quality, NOX requirements may be waived. To assist the states in making this decision, the U.S. EPA is attempting to develop guidelines for the states to use in deciding whether NOX reductions will have a positive or negative impact on O3 air quality. Although NOX is a precursor of O3, at low VOC/NOX ratios, the reduction of NOX can result in increased peak O3. EPA is examining existing information on VOC/NOX ratios to develop “rules of thumb” to guide the states in their decision-making process. An examination of 6 a.m. to 9 a.m. VOC/NOX ratios at a number of sites in the eastern U.S. indicates that the ratio is highly variable from day-to-day and there is no apparent relationship between ratios measured at differ...