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Volatile Organic Compounds (VOCs) were collected in canister samples during NASA’s Deriving Information on Surface conditions from COlumn and VERtically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) mission in July 2011. Twenty three samples were collected at the surface and analyzed for OH reactivity, temporal variability, and relationships with atmospheric dynamics in an effort to have some insight into VOC behaviors at Edgewood, MD during a short period of time. Alkenes and oxygenated volatile organic compounds (VOCs) were the most abundant and the most reactive VOCs measured over the site. Source attribution of the measured species indicates that biogenically sourced VOCs account for half the calculated OH reactivity at the site. A case study of 2 days of canister samples and ozonesondes were used to investigate VOC dynamics over the site. A stable boundary layer present on 21 July prevented a lofted layer of pollution from mixing to the ground, causing relative anthropogenic VOC contributions to decrease, increasing the relative biogenic and oxygenated mixing ratios throughout the day. Mixing of the residual layer to the ground on 22 July enhanced the anthropogenic VOCs, and high temperatures increased biogenic emissions leading to a day that with high ozone and VOC measurements. more...

Recent intensive sampling and numerical modeling studies have given insights to the processes driving atmospheric chemistry in the mid-Atlantic region. We summarize the meteorology and air quality measurements conducted as part of the NASA Deriving Information on Surface Conditions from COlumn and VERtically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) campaign and other mid-Atlantic sampling intensives during July 2011. We review the important findings of the work contained within the Processes Impacting NEar-Surface Atmospheric Pollutants (PINESAP) special issue and highlight the importance of intensive sampling campaigns as a means of gaining understanding of atmospheric chemistry in a changing climate. more...

Total-column nitrogen dioxide (NO2) data collected by a ground-based sun-tracking spectrometer system (Pandora) and an photolytic-converter-based in-situ instrument collocated at NASA’s Langley Research Center in Hampton, Virginia were analyzed to study the relationship between total-column and surface NO2 measurements. The measurements span more than a year and cover all seasons. Surface mixing ratios are estimated via application of a planetary boundary-layer (PBL) height correction factor. This PBL correction factor effectively corrects for boundary-layer variability throughout the day, and accounts for up to ≈75 % of the variability between the NO2 data sets. Previous studies have made monthly and seasonal comparisons of column/surface data, which has shown generally good agreement over these long average times. In the current analysis comparisons of column densities averaged over 90 s and 1 h are made. Applicability of this technique to sulfur dioxide (SO2) is briefly explored. The SO2 correlation is improved by excluding conditions where surface levels are considered background. The analysis is extended to data from the July 2011 DISCOVER-AQ mission over the greater Baltimore, MD area to examine the method’s performance in more-polluted urban conditions where NO2 concentrations are typically much higher. more...