1,198 publications from this institution
We identify dimethyl disulfide (DMDS) as the major reduced sulfur‐containing gas emitted from bushfires in Australia's Northern Territory. Like dimethyl sulfide (DMS), DMDS is oxidized in the atmosphere to sulfur dioxide (SO 2 ) and methane sulfonic acid (MSA), which are intermediates in the formation of sulfuric acid (H 2 SO 4 ). The mixing ratios of DMDS and DMS were the highest we have ever detected, with maximum values of 113 and 35 ppbv, respectively, whereas background values were below the detection limit (10 pptv). Molar emission ratios relative to carbon monoxide (CO) were [1.6 ± 0.1] × 10 −5 and [6.2 ± 0.3] × 10 −6 , for DMDS and DMS respectively, while molar emission ratios relative to carbon dioxide (CO 2 ) were [4.7 ± 0.4] × 10 −6 and [1.4 ± 0.4] × 10 −7 , respectively. Assuming these observations are representative of biomass burning, we estimate that biomass burning could yield up to 175 Gg/yr of DMDS (119 Gg S/yr) and 13 Gg/yr of DMS.
The late winter/early spring (February/March, 1994) measurements of Pacific Exploratory Mission‐West (PEM‐W) B have been analyzed to show latitudinal distributions (45°N to 10°S) of the mixing ratios of reactive nitrogen species (NO, peroxyacetylnitrate (PAN), HNO 3 , and NO y ), ozone, and chemical tracers (CO, NMHCs, acetone, and C 2 Cl 4 ) with a focus on the upper troposphere. Mixing ratios of all species are relatively low in the warm tropical and subtropical air south of the polar Jetstream (≈28°N) but increase sharply with latitude in the cold polar air north of the Jetstream. Noteworthy is the continuous increase in reservoir species (PAN and HNO 3 ) and the simultaneous decrease in NO x toward the northern midlatitudes. The Harvard global three‐dimensional model of tropospheric chemistry has been used to compare these observations with predictions. In the upper troposphere the magnitude and distribution of measured NO y and PAN as a function of latitude is well represented by this model, while NO x (measured NO + model calculated NO 2 ) is underpredicted, especially in the tropics. Unlike several previous studies, where model‐predicted HNO 3 exceeded observations by as much as a factor of 10, the present data/model comparison is improved to within a factor of 2. The predicted upper tropospheric HNO 3 is generally below or near measured values, and there is little need to invoke particle reactions as a means of removing or recycling HNO 3 . Comparison between measured NO y and the sum of its three main constituents (PAN + NO x + HNO 3 ) on average show a small mean shortfall (<15%). This shortfall could be attributed to the presence of known but unmeasured species (e.g., peroxynitric acid and alkyl nitrates) as well as to instrument errors.
