Abstract
Abstract. We have investigated an aerosol processing and evolution event from 21–22 July during the summer 2009 Field Intensive Study at Queens College in New York City (NYC). The evolution processes are characterized by three consecutive stages: (1) aerosol wet scavenging, (2) nighttime nitrate formation, and (3) photochemical production and evolution of secondary aerosol species. Our results suggest that wet scavenging of aerosol species tends to be strongly related to their hygroscopicities and also mixing states. The scavenging leads to a significant change in bulk aerosol composition and average carbon oxidation state because of scavenging efficiencies in the following order: sulfate > low-volatility oxygenated organic aerosol (LV-OOA) > semi-volatile OOA (SV-OOA) > hydrocarbon-like OA (HOA). The second stage involves a quick formation of nitrate from heterogeneous reactions at nighttime. During the third stage, simultaneous increases of sulfate and SV-OOA were observed shortly after sunrise, indicating secondary aerosol formation. Organic aerosols become highly oxidized in ~ half day as the result of photochemical processing, consistent with previously reported results from the CO-tracer method (OA/ΔCO). The photochemical reactions appear to progress gradually associated with a transformation of SV- OOA to low-volatility species based on the evolution trends of oxygen-to-carbon (O/C) ratio, relationship between f44 (fraction of m/z 44 in OA) and f43 (fraction of m/z 43 in OA), and size evolution of OOA and HOA. Aerosols appear to become more internally mixed during the processing. Our results suggest that functionalization by incorporation of both C and O plays a major role in the early period of OA oxidation (O/C < 0.5). Our results also show that photochemical production of LV-OOA during this event is approximately 2–3 h behind of sulfate production, which might explain, sometimes, the lack of correlations between LV-OOA and sulfate, two secondary aerosol species which often exist in internal mixtures over regional scales.
Highlights
Atmospheric aerosols, consisting of liquid and solid particles suspended in the air, are important components of atmosphere
Our results show that photochemical production of low-volatility oxygenated organic aerosol (LV-OOA) during this event is approximately 2– 3 h behind of sulfate production, which might explain, sometimes, the lack of correlations between LV-OOA and sulfate, two secondary aerosol species which often exist in internal mixtures over regional scales
The aerosol processing during these two days can be classified into three stages: (I) aerosol wet scavenging, (II) night time nitrate formation, and (III) photochemical production and aging of secondary aerosol species
Summary
Atmospheric aerosols, consisting of liquid and solid particles suspended in the air, are important components of atmosphere. Aerosols play a significant role in visibility reduction (Watson, 2002), regional air pollution (Molina and Molina, 2004), and climate change (IPCC, 2007). Aerosols and their associated direct and indirect effects on radiative forcing are highly uncertain (Forster et al, 2007) due to a lack of knowledge on their sources, composition, evolution processes and deposition (Poschl, 2005; Hallquist et al, 2009). Sun et al.: A case study of aerosol processing and evolution in summer in New York City al., 2007a; Jimenez et al, 2009), are most poorly understood because of their complex and diverse volatilities, functionalities, and solubilities. Aerosols exert a serious impact on human health by increasing the damage of respiratory and cardiovascular systems and reducing life expectancy (Pope et al, 2002, 2009)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
