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ABSTRACTThis study examined reactive oxidized nitrogen (NOy) speciation and partitioning at one urban site, Queens College (QC) in New York City, and one rural site, Pinnacle State Park (PSP) in Addison, New York (NY) from September 2016 to August 2018 and June 2016 to September 2018, respectively. Oxides of nitrogen (NOx), nitric acid (HNO3), particle nitrate (pNO3), peroxy nitrates (PNs), alkyl nitrates (ANs), and NOymeasurements were made at both sites. Across all seasons at QC, the median NOx, HNO3, pNO3, PNs, ANs, and NOyconcentrations were 10.99, 0.49, 0.24, 0.62, 0.94, and 13.95 parts per billion (ppb), respectively. All-season median percent contributions of NOx, HNO3, pNO3, PNs, and ANs to the total NOyat QC were 77, 4, 2, 5, and 7%, respectively. Therefore, the sum of the individual NOyspecies (NOyi≈ NOx+ HNO3+ pNO3+ PNs + ANs) accounted for 95% of the total NOyat QC, which was well within measurement uncertainties. At PSP, the median NOx, HNO3, pNO3, PNs, ANs, and NOyconcentrations were 0.65, 0.16, 0.12, 0.13, 0.18, and 1.56 ppb, respectively, over all seasons. The median percent contributions of NOx, HNO3, pNO3, PNs, and ANs to NOyover all seasons at PSP were 42, 10, 8, 9, and 12%, respectively. NOyicomprised 81% of NOyacross all seasons at PSP, and deviations from 100% closure were generally within measurement uncertainties. Since both datasets yielded NOybudget closure results that were either fully or largely explained by the measurement uncertainties, the observed NOyiis likely representative of ambient NOyin urban and rural New York. The results have implications for understanding the fate of NOxemissions and their impact on local and regional air quality in urban and rural New York State.Implications: Continuous speciated and total reactive oxidized nitrogen (NOy) measurements were made in urban and rural New York from 2016 to 2018. Different NOyspecies have contrasting effects on the chemistry that impacts ozone (O3) and fine particulate matter (PM2.5) formation and concentrations. Since O3and PM2.5are regulated pollutants that have proven difficult to control, the results have implications for current and future air quality policy.

ABSTRACTNear-road measurements in Rochester, NY with a Portable Air Quality Monitoring System indicate a significant plume control of PM2.5black carbon (BC) concentrations. This study evaluates the performance of two portable air quality enclosures deployed at collocated research sites to determine their accuracy and usefulness in field deployments, and specifically in pollution plume analysis. One system deployed collocated sensors for measurement of particulate matter mass concentration (Thermo pDR 1500 against Tapered Element Oscillating Microbalance (TEOM) measurement) and the second system deployed sensors for measurement of black carbon (Magee AE33 aethalometer and Brechtel Tricolor Absorption Photometer) in ambient and near-road locations in Rochester, New York, respectively. While the optical PM2.5sensors tended to be biased in their determination of concentration by ~15%, they followed changes and trends in concentration very well. The black carbon sensors in the portable systems agreed very well with each other and with the collocated sensor. As a case study to determine the contribution from statistically significant short-lived excursions of pollutant concentration, Morlet wavelet analysis was performed on data from the portable system sensors. Black carbon was found to be strongly influenced by plume behavior with significant plume excursions representing just over 12% of all data points and contributing on average 1 µg/m3of black carbon above ambient concentrations.Implications: This paper first evaluates two air pollutant monitoring enclosures with wide applicability including near-road detection of pollutants. Then, we present a novel method to designate isolate statistically significant excursions in air pollution concentration which can be used to determine the impact of pollutant plumes as observed in PM and black carbon behavior near road.

The effect of foggy/moist conditions on the characteristics of secondary organic aerosol (SOA) was studied. Analysis of the high‐resolution time‐of‐flight aerosol mass spectrometer measurements identified two fresh biogenic SOA factors (BSOA: BSOA‐1 and BSOA‐2), hypothesized to be formed through the nighttime reaction of biogenic volatile organic compounds with nitrate radical. During foggy periods, the more oxidized oxygenated OA (MO‐OOA) was scavenged most efficiently (86% removal), followed by the less oxidized OOA (LO‐OOA) (55%), SO4(53%), and BSOA (25%). Aerosol mass increased during fog events, and the post‐fog aerosol mass was higher (11%) than during the prefog period, with a reduction for MO‐OOA and an enhancement for LO‐OOA and BSOA. The high positive correlation observed between aerosol liquid water (ALW) and BSOA suggests the importance of aqueous‐phase processing on the BSOA formation, and an increase in log10(ALW) of 1 corresponded to an average increase of about 0.9 μg m−3in BSOA. Ground‐level aerosols impact human health, climate, and ecosystem health. Aerosols have complex chemical composition, and the chemistry of the carbonaceous fraction is a topic of great interest to atmospheric chemistry and air quality. Aerosol liquid water is an important component of these particles in humid environments, and it becomes the dominant component if the particle grows to become a fog or cloud droplet. In addition to influencing particle growth, the aerosol liquid water provides another medium in which chemical reactions can occur and produces species that remain in the condensed phase and thereby increase aerosol mass loading. This study investigated the evolution of aerosol mass and chemical composition in moist and foggy nighttime environments in a rural forested area of the Northeast U.S. Organic aerosols that were identified as biogenic secondary organic aerosols were observed to increase in mass concentration during foggy conditions, and in this environment, they increased linearly in mass as a function of the base 10 logarithm of aerosol liquid water over a wide range. The influence of aerosol liquid water on the chemical reactivity of aerosols could help to bridge the gap between modeled and observed secondary organic aerosol mass. The effect of foggy conditions and fog processing on the characteristics of secondary aerosol was studiedBiogenic secondary organic aerosol (BSOA) concentrations increased during nighttime moist conditionsHigh positive correlation existed between BSOA and relative humidity (RH)/or aerosol liquid water (ALW)