Comparison of daytime and nighttime oxidation of biogenic and anthropogenic VOCs along the New England coast in summer during New England Air Quality Study 2002

Abstract

[1] Volatile organic compounds (VOCs) and some of their oxidants (O 3 , NO 3 ) were measured on board the National Oceanic and Atmospheric Administration research ship R/V Ronald H. Brown along the coast of New England, downwind of New York, Boston, and Portsmouth and large forested areas in New Hampshire, Maine, and Massachusetts in July and August 2002. The diurnal variations of isoprene, monoterpenes, and aromatics were mainly dependent on their emissions and the abundance of the oxidants OH and NO 3 . Elevated mixing ratios of short-lived VOCs were only encountered at the ship, which was about 1-6 hours downwind of the sources, when the concentrations of the oxidants were low. For the biogenic compounds this was generally the case during morning and evening hours, when the lifetime of the biogenics was long because of low OH and NO 3 concentrations. Most anthropogenic VOCs do not react with NO 3 , and therefore their mixing ratios remained elevated during the night. The products of isoprene oxidation, methyl vinyl ketone, methacrolein, and peroxymethacrylic nitric anhydride (MPAN) were, on average, more abundant than isoprene itself. Only during the transition periods from day to night, when oxidation rates were at a minimum, could isoprene exceed its products. The loss of the biogenic VOCs was dominated by reactions with NO 3 , whereas the loss of anthropogenics came mostly from reactions with OH. The oxygenated VOCs are the major contributor to the OH loss, except in close vicinity of emission sources. The total loss of biogenic compounds during the night was so effective that after one night of transport they were in most cases completely reacted away, whereas the mixing ratios of the anthropogenic compounds remained high during the night. The pool of reactive hydrocarbons at sunrise was thus typically dominated by anthropogenic VOCs.

Diurnal and temporal variations of water-soluble dicarboxylic acids and related compounds in aerosols from the northern vicinity of Beijing: Implication for photochemical aging during atmospheric transport

“…During mid-day, OH radicals are important oxidants (Fan and Zhang, 2004) as well as O 3 (Kamens et al, 1982). In contrast, the nighttime oxidant is mainly NO 3 , which attacks biogenic (such as monoterpenes and isoprene) and anthropogenic VOCs (Warneke et al, 2004). Thus, VOCs and their oxidation products may serve as precursors in nighttime.…”

Budget of organic carbon in a polluted atmosphere: Results from the New England Air Quality Study in 2002

“…Most of this time was spent along the coast of New Hampshire and Massachusetts (July 17-August 6) and on a single transect along the coast of Maine . The sampled air masses had been impacted by major urban areas such as New York City and Boston, and by biogenic emissions in New Hampshire and Maine [Warneke et al, 2004;Goldan et al, 2004]. Power plants and ocean vessels were found to be very minor sources of VOCs.…”

“…[6] The cruise track of the NOAA research vessel Ronald H. Brown during NEAQS, and the measurements used in the paper have been described in detail elsewhere [de Gouw et al, 2003a;Warneke et al, 2004;Goldan et al, 2004], and only the details pertinent to the current work are presented here. The cruise track of the NOAA ship Ronald H. Brown consisted of two legs: Charleston, SC -Portsmouth, NH between July 12 and 26 of 2002, and Portsmouth -Charleston from July 29 until August 10.…”

“…[21] Warneke et al [2004] have shown that for all anthropogenic VOCs the reaction with OH was the dominant loss mechanism during NEAQS (assumption 3). Reactions with nitrate (NO 3 ) radicals at night were minor sinks for anthropogenic VOCs, a large fraction of which consists of saturated and aromatic hydrocarbons.…”

“…where [VOC] and [C 2 H 2 ] are the volume mixing ratios of a primary VOC (benzene and ethyl benzene in this case) and acetylene, ER VOC is the emission ratio of the VOC versus acetylene, and k VOC and k C 2 H 2 are the rate coefficients for the reactions of those compounds with OH (3 Â 10 6 molecules cm À3 [Warneke et al, 2004]). The full curves in Figures 1c and 1d show the best fit of equation (3) (3) remains the same.…”