Ambient Atmospheric Hydrocarbon Content as Determined by Gas Chromatographic Techniques from Rural Tidewater Virginia in Late Spring 1974

In an attempt to ascertain the naturally generated hydrocarbon contribution to the air quality of the Hampton Roads region of Tidewater Virginia, a series of 27 air samples was obtained in two rural locations during late spring of 1974. These samples were analyzed for their hydrocarbon content (carbon number range C5 to C10) using gas chromatographic techniques. The thirty different hydrocarbon species were identified and monitored in the experiment. Preliminary analysis of the data indicates an average concentration of 397 parts per billion by weight (carbon) for the total non-methane hydrocarbon loading for C5 to C10 during the experiment. This value exceeds the National Primary Air Quality Standards as set by the Environmental Protection Agency

Interdisciplinary study of atmospheric processes and constituents of the mid-Atlantic coastal region.

Past research projects for the year 1974-1975 are listed along with future research programs in the area of air pollution control, remote sensor analysis of smoke plumes, the biosphere component, and field experiments. A detailed budget analysis is presented. Attachments are included on the following topics: mapping forest vegetation with ERTS-1 MSS data and automatic data processing techniques, and use of LARS system for the quantitative determination of smoke plume lateral diffusion coefficients from ERTS images of Virginia

Transport of sulfur dioxide from the Asian Pacific Rim to the North Pacific troposphere

The NASA Pacific Exploratory Mission over the Western Pacific Ocean (PEM-West B) field experiment provided an opportunity to study sulfur dioxide (SO2) in the troposphere over the western Pacific Ocean from the tropics to 60°N during February–March 1993. The large suite of chemical and physical measurements yielded a complex matrix in which to understand the distribution of sulfur dioxide over the western Pacific region. In contrast to the late summer period of Pacific Exploratory Mission-West A (PEM-West A) (1991) over this same area, SO2showed little increase with altitude, and concentrations were much lower in the free troposphere than during the PEM-West B period. Volcanic impacts on the upper troposphere were again found as a result of deep convection in the tropics. Extensive emission of SO2 from the Pacific Rim land masses were primarily observed in the lower well-mixed part of the boundary layer but also in the upper part of the boundary layer. Analyses of the SO2 data with aerosol sulfate, beryllium-7, and lead-210 indicated that SO2 contributed to half or more of the observed total oxidized sulfur (SO2 plus aerosol sulfate) in free tropospheric air. The combined data set suggests that SO2 above 8.5 km is transported from the surface but with aerosol sulfate being removed more effectively than SO2. Cloud processing and rain appeared to be responsible for lower SO2 levels between 3 and 8.5 km than above or below this region

Highlights of OH, H2SO4, and methane sulfonic acid measurements made aboard the NASA P-3B during Transport and Chemical Evolution over the Pacific

Measurements of hydroxyl radical (OH), sulfuric acid (H2SO4), and methane sulfonic acid (MSA) were performed aboard the NASA P-3B using the selected ion chemical ionization mass spectrometry technique during the Transport and Chemical Evolution over the Pacific (TRACE-P) study. Photochemical box model calculations of OH concentrations yielded generally good agreement with an overall tendency to overestimate the measured OH by ∼20%. Further analysis reveals that this overestimation is present only at altitudes greater than ∼1.5 km, with the model underestimating OH measurements at lower altitudes. Boundary layer H2SO4 measurements, performed in a volcanic plume off the southern coast of Japan, revealed some of the largest marine boundary layer H2SO4 concentrations ever observed and were accompanied by new particle formation. Nighttime measurements of OH, H2SO4, and MSA in the remote pacific off Midway Island revealed significant boundary layer concentrations of H2SO4 and MSA, indicating evidence of nighttime boundary layer oxidation processes but in the absence of OH. A cursory exploration of the sources of production of the H2SO4 and MSA observed at night is presented

Carbonyl sulfide and carbon disulfide: Large-scale distributions over the western Pacific and emissions from Asia during TRACE-P

An extensive set of carbonyl sulfide (OCS) and carbon disulfide (CS2) observations were made as part of the NASA Transport and Chemical Evolution over the Pacific (TRACE-P) project, which took place in the early spring 2001. TRACE-P sampling focused on the western Pacific region but in total included the geographic region 110°E to 290°E longitude, 5°N to 50°N latitude, and 0–12 km altitude. Substantial OCS and CS2 enhancements were observed for a great many air masses of Chinese and Japanese origin during TRACE-P. Over the western Pacific, mean mixing ratios of long-lived OCS and shorter-lived CS2 showed a gradual decrease by about 10% and a factor of 5–10, respectively, from the surface to 8–10 km altitude, presumably because land-based sources dominated their distribution during February through April 2001. The highest mean OCS and CS2levels (580 and 20 pptv, respectively, based on 2.5° × 2.5° latitude bins) were observed below 2 km near the coast of Asia, at latitudes between 25°N and 35°N, where urban Asian outflow was strongest. Ratios of OCS versus CO for continental SE Asia were much lower compared to Chinese and Japanese signatures and were strongly associated with biomass burning/biofuel emissions. We present a new inventory of anthropogenic Asian emissions (including biomass burning) for OCS and CS2 and compare it to emission estimates based on regional relationships of OCS and CS2 to CO and CO2. The OCS and CS2 results for the two methods compare well for continental SE Asia and Japan plus Korea and also for Chinese CS2 emissions. However, it appears that the inventory underestimates Chinese emissions of OCS by about 30–100%. This difference may be related to the fact that we did not include natural sources such as wetland emissions in our inventory, although the contributions from such sources are believed to be at a seasonal low during the study period. Uncertainties in OCS emissions from Chinese coal burning, which are poorly characterized, likely contribute to the discrepancy

Seasonal dependence of peroxy radical concentrations at a northern hemisphere marine boundary layer site during summer and winter: evidence for photochemical activity in winter

International audiencePeroxy radicals (HO2+?RO2) were measured at the Weybourne Atmospheric Observatory (52° N, 1° E), Norfolk using a PEroxy Radical Chemical Amplifier (PERCA) during the winter and summer of 2002. The peroxy radical diurnal cycles showed a marked difference between the winter and summer campaigns with maximum concentrations of 12 pptv at midday in the summer and maximum concentrations as high as 30 pptv (10 min averages) in winter at night. The corresponding nighttime peroxy radical concentrations were not as high in summer (3 pptv). The peroxy radical concentration shows a distinct anti-correlation with increasing NOx during the daylight hours. At night, peroxy radicals increase with increasing NOx indicative of the role of NO3 chemistry. The average diurnal cycles for net ozone production, N(O3) show a large variability in ozone production, P(O3), and a large ozone loss, L(O3) in summer relative to winter. For a daylight average, net ozone production in summer than winter (1.51±0.5 ppbv h?1 and 1.11±0.47 ppbv h?1 respectively) but summer shows more variability of (meteorological) conditions than winter. The variability in NO concentration has a much larger effect on N(O3) than the peroxy radical concentrations. Photostationary state (PSS) calculations show an NO2 lifetime of 5 min in summer and 21 min in the winter, implying that steady-state NO-NO2 ratios are not always attained during the winter months. The results show an active peroxy radical chemistry at night and the ability of winter to make oxidant. The net effect of this with respect to production of ozone in winter is unclear owing to the breakdown in the photostationary state

Seasonal dependence of peroxy radical concentrations at a Northern hemisphere marine boundary layer site during summer and winter: evidence for radical activity in winter

Peroxy radicals (HO2+Σ RO2) were measured at the Weybourne Atmospheric Observatory (52° N, 1° E), Norfolk using a PEroxy Radical Chemical Amplifier (PERCA) during the winter and summer of 2002. The peroxy radical diurnal cycles showed a marked difference between the winter and summer campaigns with maximum concentrations of 12 pptv at midday in the summer and maximum concentrations as high as 30 pptv (10 min averages) in winter at night. The corresponding nighttime peroxy radical concentrations were not as high in summer (3 pptv). The peroxy radical concentration shows a distinct anti-correlation with increasing NOx during the daylight hours. At night, peroxy radicals increase with increasing NOx indicative of the role of NO3 chemistry. The average diurnal cycles for net ozone production, N(O3) show a large variability in ozone production, P(O3), and a large ozone loss, L(O3) in summer relative to winter. For a daylight average, net ozone production in summer was higher than winter (1.51±0.5 ppbv h−1 and 1.11±0.47 ppbv h−1, respectively). The variability in NO concentration has a much larger effect on N(O3) than the peroxy radical concentrations. Photostationary state (PSS) calculations show an NO2 lifetime of 5 min in summer and 21 minutes in the winter, implying that steady-state NO-NO2 ratios are not always attained during the winter months. The results show an active peroxy radical chemistry at night and that significant oxidant levels are sustained in winter. The net effect of this with respect to production of ozone in winter is unclear owing to the breakdown in the photostationary state

Regional-scale chemical transport modeling in support of the analysis of observations obtained during the TRACE-P experiment

Data obtained during the TRACE-P experiment is used to evaluate how well the CFORS/STEM-2K1 regional-scale chemical transport model is able to represent the aircraft observations. Thirty-one calculated trace gas and aerosol parameters are presented and compared to the in situ data. The regional model is shown to accurately predict many of the important features observed. The mean values of all the model parameters in the lowest 1 km are predicted within ±30% of the observed values. The correlation coefficients (R) for the meteorological parameters are found to be higher than those for the trace species. For example, for temperature, R \u3e 0.98. Among the trace species, ethane, propane, and ozone show the highest values (0.8 \u3c R \u3c 0.9), followed by CO, SO2, and NOy, NO and NO2 had the lowest values (R \u3c 0.4). Analyses of pollutant transport into the Yellow Sea by frontal events are presented and illustrate the complex nature of outflow. Biomass burning from SE Asia is transported in the warm conveyor belt at altitudes above ∼2 km and at latitudes below 30N. Outflow of pollution emitted along the east coast of China in the postfrontal regions is typically confined to the lower ∼2 km and results in high concentrations with plume-like features in the Yellow Sea. During these situations the model underpredicts CO and black carbon (among other species). An analysis of ozone production in this region is also presented. In and around the highly industrialized regions of East Asia, where fossil fuel usage dominates, ozone is NMHC-limited. South of ∼30-35N, ozone production is NOx-limited, reflecting the high NMHC/NOx ratios due to the large contributions to the emissions from biomass burning, biogenics sources, and biofuel usage in central China and SE Asia. Copyright 2003 by the American Geophysical Union