Summertime formaldehyde observations in New York City: Ambient levels, sources and its contribution to HOx radicals

Abstract

[1] Measurements of ambient formaldehyde (HCHO), related gases and particulate matter were carried out from the SUNY Albany mobile platform at the Queens College site in New York City (NYC) from 15 July to 3 August 2009. Ambient HCHO was measured using a quantum cascade laser (QCL) trace gas detector. HCHO concentrations ranged from 0.4 to 7.5 ppb with a mean value of 2.2 AE 1.1 ppb. Daily HCHO peaks were nearly always found between 1100 EST (Eastern Standard Time) and noontime throughout the sampling period. HCHO correlated strongly with NOx and black carbon during the traffic rush hours, but around noontime HCHO correlated much better with total oxidants (Ox = O 3 + NO 2 ). Using the diurnal pattern of HCHO/BC ratios, we estimated that 70% of HCHO present between 1200 EST to 1500 EST was produced by photochemical reactions. Sources of photochemically produced HCHO were calculated using measured concentrations of hydrocarbons, their reaction kinetics with OH radicals, and HCHO yields. These calculations indicated that isoprene oxidation was the dominant source of HCHO for this period at this site, responsible for 44%, followed by methane (25%) and propene (18%). To assess the impact of HCHO as a radical source, the HOx production rates from HCHO, HONO, O 3 photolysis, and alkenes +O 3 were calculated as well. Daily averaged HOx production rates from HONO, HCHO, O 3 photolysis and alkenes +O 3 were 8.6 Â 10 6 , 2.3 Â 10 6 , 1.7 Â 10 6 , 2.1 Â 10 5 molecules cm À3 s À1 , respectively, contributing 67, 18, 13 and 2% to the overall daily HOx radical budget from these precursors.

A case study of aerosol processing and evolution in summer in New York City

“…Given the short lifetime of HCHO (typically 3-4 h during the summertime conditions), the continuous increase of HCHO till 14:00 suggests that aerosol processing during the early stage III was most likely driven by local photochemical oxidation. The decrease of HCHO after 14:00 was likely due to photolysis and further oxidation by OH (Lin et al, 2011), consistent with the oxidation of SV-OOA to LV-OOA in the afternoon. LV-OOA + SV-OOA, a surrogate of SOA, shows tight correlation with O 3 (r 2 = 0.84) but weaker correlation (r 2 = 0.40) with O x (NO 2 + O 3 ), likely due to an important contribution of NO 2 from local emissions.…”

“…1c). Detailed analysis of the sources of HCHO during this campaign showed that on average ∼60 % of HCHO was produced from photochemical reactions, mainly oxidation of isoprene, methane, and propene (Lin et al, 2011). Given the short lifetime of HCHO (typically 3-4 h during the summertime conditions), the continuous increase of HCHO till 14:00 suggests that aerosol processing during the early stage III was most likely driven by local photochemical oxidation.…”

“…The HR-AMS was deployed inside the state-of-the-art Atmospheric Sciences Research Center-Mobile Laboratory (ASRC-ML) (Lin et al, 2011) along with various fastresponse aerosol and gas instruments. During the 3-week continuous measurements, the ASRC-ML was parked at Lot 6, which is approximately 500 m south of the Long Island Expressway (LIE, I-495) and 1.2 km east of the Van Wyck Expressway (I-678), two high-traffic highways in the NYC metropolitan area.…”

Quantifying the ambient formaldehyde sources utilizing tracers

“…The ratios of HCHO/acetaldehyde can be used as an indicator to perform a diagnostic evaluation, qualitatively, on the biogenic/anthropogenic origins of HCHO [2]. Several methods were used to quantify the primary and secondary sources of HCHO, such as methods based on the emission ratios of HCHO/tracer of primary sources [3,4], the multi-linear regression method based on ambient measurements of HCHO and tracers [5,6], the photochemical age method based on parameterization of atmospheric reactions [7,8] and receptor models like positive matrix factorization (PMF) [9,10]. In this study, the multi-linear regression approach was selected to estimate the HCHO sources in Ziyang city.…”

Theoretical investigation on the role of mineral dust aerosol in atmospheric reaction: A case of the heterogeneous reaction of formaldehyde with NO 2 onto SiO 2 dust surface

“…HCHO is one of the most prevalent VOCs in the Earth's atmosphere. It can be produced by the photooxidation of most VOCs and serve as an important source of HO x radical (Lin et al, 2012), peroxy radicals, and peroxyacyl nitrates (Carlos-Cuellar et al, 2003). Therefore, its dual role makes it as an important species for testing the performance of photochemical oxidant models.…”