Estimation of particulate organic nitrates from thermodenuder-aerosol mass spectrometer measurements in North China Plain

Abstract

Abstract. Particulate organic nitrates (pON) are an important component of secondary organic aerosol in biogenic emission dominant environments, and play a critical role in NOx cycles. However, estimation of pON has been a challenge in polluted environments, e.g., North China Plain with high concentrations of inorganic nitrate and NOx. Here we developed a method for estimation of pON from the measurements of high-resolution aerosol mass spectrometer coupled with a thermodenuder based on the volatility differences between inorganic nitrate and pON. The results generally correlated well with those estimated from positive matrix factorization of combined organic and inorganic mass spectra and from the ratio of NO+ to NO2+ (NOx+ ratio), yet had improvements in reducing negative values due to the influences of high concentration of inorganic nitrate and constant NOx+ ratio of organic nitrates (RON). By applying this approach to the measurements at an urban (Beijing) and a rural site (Gucheng) in summer and winter in North China Plain, we estimated that the average mass concentrations of NO3,org (1.8 µg m−3 vs.1.0 µg m−3) and pON to OA (27.5 % vs. 14.8 %) were higher in summer than in winter in Beijing, indicating more pON formation in biogenically and anthropogenically mixed environments. In addition, the average NO3,org loading in Gucheng was 1.9 µg m−3, and the pON at the rural site also showed higher contribution to OA than that in Beijing during wintertime due to higher primary emissions and gaseous precursors in Gucheng. In addition, RON was determined and showed considerable differences between day-night and clean-polluted periods, highlighting the complexity of pON compounds from different chemical pathways (e.g., OH and NO3 oxidation) and sources.

Contribution of Organic Nitrates to Organic Aerosol over South Korea during KORUS-AQ

“…Particle-phase organic nitrates (pRONO 2 ) have recently emerged as a significant component of SOA in areas dominated by biogenic emissions, including in the Southeast United States, − in the Rocky Mountains, across Europe, in the boreal forest, in the California Central Valley, , and in rural areas of both northern and southern China. − A number of studies have also found significant contributions of pRONO 2 to SOA in regions of oil and gas production, including in the Alberta Oil Sands and in the Uintah Basin . Recent observations have shown that organic nitrates are a significant contributor to OA in Chinese cities. , Specifically, Yu et al found that organic nitrates make up 9–25% of OA during spring-autumn in urban Shenzhen, and the dominant precursors to pRONO 2 included both biogenic (α-pinene, limonene, and camphene) and anthropogenic (styrene) VOCs.…”

A comprehensive evaluation of enhanced temperature influence on gas and aerosol chemistry in the lamp-enclosed oxidation flow reactor (OFR) system

“…For the existing OA which is sampled into the OFR, the evaporation of input OA upon heating can be roughly estimated based on the results of thermal denuder (TD) experiments, in which the aerosols were heated from ambient/room temperatures (20-25 °C ) to higher temperatures (typically 60-200 °C ) at a typical residence time of 10-60 s (typically ~20 480 s) (Huffman et al, 2009;Xu et al, 2020;Hu et al, 2016;Saha et al, 2017;Kolesar et al, 2015;Saha and Grieshop, 2016;Lee et al, 2011). Previous studies suggest the evaporation of aerosol is kinetically limited, which varies with temperature, residence time, OA mass and volatility, phase state and dissociation rates for oligomers (Cappa, 2010;Riipinen et al, 2010;Roldin et al, 2014;Schobesberger et al, 2018).…”