Abstract
Abstract. Isoprene is an important atmospheric volatile organic compound involved in ozone production and NOx (NO+NO2) sequestration and transport. Isoprene reaction with OH in the presence of NO can form either isoprene hydroxy nitrates ("isoprene nitrates") or convert NO to NO2 which can photolyze to form ozone. While it has been shown that isoprene nitrate production can represent an important sink for NOx in forest impacted environments, there is little experimental knowledge of the relative importance of the individual isoprene nitrate isomers, each of which has a different fate and reactivity. In this work, we have identified the 8 individual isomers and determined their total and individual production yields. The overall yield of isoprene nitrates at atmospheric pressure and 295 K was found to be 0.070(+0.025/−0.015). Three isomers, representing nitrates resulting from OH addition to a terminal carbon, represent 90% of the total IN yield. We also determined the ozone rate constants for three of the isomers, and have calculated their atmospheric lifetimes, which range from ~1–2 h, making their oxidation products likely more important as atmospheric organic nitrates and sinks for nitrogen.
Highlights
Isoprene (2-methyl-1,3-butadiene) is the dominant biogenic volatile organic compound emitted into the atmosphere at 500–750 Tg yr−1 (Guenther et al, 2006)
Isoprene is emitted by plants and readily reacts with OH radicals, ozone, and NO3 in the atmosphere (Tuazon and Atkinson, 1990; Chuong and Stevens, 2002; Guenther et al, 2006)
Eight isoprene nitrate isomers (INs), including the Z- and E- isomers of the (1,4)- and the (4,1)-Isoprene nitrate (IN), formed from Reactions (R1) and (R3), are shown in Fig. 1 (Chen et al, 1998). These isoprene nitrates are very reactive because they are still olefinic. Their atmospheric oxidation products, which are longer lived than the parent INs because they are saturated, are likely more important than the original nitrate with regard to transport and deposition (Giacopelli et al, 2005; Horowitz et al, 2007; Paulot et al, 2009b)
Summary
Isoprene (2-methyl-1,3-butadiene) is the dominant biogenic volatile organic compound emitted into the atmosphere at 500–750 Tg yr−1 (Guenther et al, 2006). These isoprene nitrates are very reactive because they are still olefinic Their atmospheric oxidation products, which are longer lived than the parent INs because they are saturated, are likely more important than the original nitrate with regard to transport and deposition (Giacopelli et al, 2005; Horowitz et al, 2007; Paulot et al, 2009b). Chen 2.1 Synthesis et al (1998) utilized a nitrate selective detector to measure the INs using chamber experiments and gas chromatography They determined a yield of 4.4 (±0.8)%. It has been discussed by Giacopelli et al (2005) that the lifetimes of the individual INs are likely quite different, and the ultimate distribution of isomers in ambient air will
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
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 call
