A study of global atmospheric budget and distribution of acetone using global atmospheric model STOCHEM-CRI

Abstract

h i g h l i g h t sPhotochemical production from monoterpenes gives 64% to the global acetone sources. The tropospheric life-time of acetone is found to be 18 days. Higher acetone is found over the forested regions throughout the summer. Good agreement between model and measurement data for acetone is found. a b s t r a c tThe impact of including a more detailed VOC oxidation scheme (CRI v2-R5) with a multi-generational approach for simulating tropospheric acetone is investigated using a 3-D global model, STOCHEM-CRI. The CRI v2-R5 mechanism contains photochemical production of acetone from monoterpenes which account for 64% (46.8 Tg/yr) of the global acetone sources in STOCHEM-CRI. Both photolysis and oxidation by OH in the troposphere contributes equally (42%, each) and dry deposition contributes 16% of the atmospheric sinks of acetone. The tropospheric life-time and the global burden of acetone are found to be 18 days and 3.5 Tg, respectively, these values being close to those reported in the study of Jacob et al. (2002). A dataset of aircraft campaign measurements are used to evaluate the inclusion of acetone formation from monoterpenes in the CRI v2-R5 mechanism used in STOCHEM-CRI. The overall comparison between measurements and models show that the parameterised approach in STOCHEM-NAM (no acetone formation from monoterpenes) underpredicts the mixing ratios of acetone in the atmosphere. However, using a detailed monoterpene oxidation mechanism forming acetone has brought the STOCHEM-CRI into closer agreement with measurements with an improvement in the vertical simulation of acetone. The annual mean surface distribution of acetone simulated by the STOCHEM-CRI shows a peak over forested regions where there are large biogenic emissions and high levels of photochemical activity. Year-long observations of acetone and methanol at the Mace Head research station in Ireland are compared with the simulated acetone and methanol produced by the STOCHEM-CRI and found to produce good overall agreement between model and measurements. The seasonal variation of model and measured acetone levels at Mace Head, California, New Hampshire and Minnesota show peaks in summer and dips in winter, suggesting that photochemical production may have the strongest effect on its seasonal trend.

Carbon monoxide isotopic measurements in Indianapolis constrain urban source isotopic signatures and support mobile fossil fuel emissions as the dominant wintertime CO source

“…We used an ‰; this change is insignificant relative to our measurement errors and can therefore be ignored (Table S2, Methane and non-methane hydrocarbon (NMHC) oxidation accounts for approximately half of the global CO budget (Duncan et al, 2007) and we estimate the contribution of these to the wintertime Indianapolis urban CO budget. Compounds such as OH and O 3 readily oxidize CH 4 and many NMHCs (Sander et al, 2006; Warneke et al, 2013;Russo et al, 2011;Khan et al, 2015) making them seasonally-varying sources of CO (Duncan et al, 2007). However, the relatively low wintertime NMHC and OH mole fractions (Helmig et al, 2013; Hu et al, 2015) mean that CH 4 and NMHC oxidation may be unimportant for our study.…”

“…However, the relatively low wintertime NMHC and OH mole fractions (Helmig et al, 2013; Hu et al, 2015) mean that CH 4 and NMHC oxidation may be unimportant for our study. Not all NMHC species capable of impacting CO are measured at INX; therefore some of the NMHC mole fractions are estimated using other urban studies in the literature (Warneke et al, 2013;Russo et al, 2011;Khan et al, 2015) (Table S2, supplemental material). Reaction rates with OH were calculated using k OH from Warneke et al (2013) if available, and if not, k OH was calculated using parameters from Sander et al (2006), and Atkinson et al, (1999, 2006.…”

Earth System Chemistry integrated Modelling (ESCiMo) with the Modular Earth Submodel System (MESSy) version 2.51

“…These results are in line with the previous evaluation of Pozzer et al (2007, Table 8), who observed an underestimation of ∼ 50-35 % for the same biogenic emissions as used here (55 Tg a −1 ), which account for ∼ 85 % of the total emissions. These results indicate the need for considering oceanic emissions and photochemical production of CH 3 COCH 3 from monoterpenes, methylbutenol, and higher iso-alkanes Khan et al, 2015), which were not included. For example Pozzer et al (2010) showed that i-butane and i-pentane are responsible for the photochemical production of 4.3 and 5.8 Tg a −1 of CH 3 COCH 3 , respectively.…”

Volatile organic compounds (VOCs) in photochemically aged air from the eastern and western Mediterranean

“…Depending on the season and geographical location the ocean can either be a sink (82 Tg yr −1 ) or a source (80 Tg yr −1 ) of acetone . Khan et al (2015), on the other hand, calculate a global acetone source of 72.7 Tg yr −1 , of which 55.6 Tg yr −1 are photochemical production from α-pinene, β-pinene and propane and 17.1 Tg yr −1 direct emission. From the total sink of 72.9 Tg yr −1 , 30.8 Tg yr −1 represent OH oxidation, 30.3 Tg yr −1 photolysis and 11.8 Tg yr −1 dry deposition and the ocean is regarded as being globally in a near-equilibrium state (Khan et al, 2015).…”