Atmospheric Trends in Methylchloroform and the Global Average for the Hydroxyl Radical

Abstract

Frequent atmospheric measurements of the anthropogenic compound methylchloroform that were made between 1978 and 1985 indicate that this species is continuing to increase significantly around the world. Reaction with the major atmospheric oxidant, the hydroxyl radical (OH), is the principal sink for this species. The observed mean trends for methylchloroform are 4.8, 5.4, 6.4, and 6.9 percent per year at Aldrigole (Ireland) and Cape Meares (Oregon), Ragged Point (Barbados), Point Matatula (American Samoa), and Cape Grim (Tasmania), respectively, from July 1978 to June 1985. These measured trends, combined with knowledge of industrial emissions, were used in an optimal estimation inversion scheme to deduce a globally averaged methylchloroform atmospheric lifetime of 6.3 (+ 1.2, -0.9) years (1sigma uncertainty) and a globally averaged tropospheric hydroxyl radical concentration of (7.7 +/- 1.4) x 10(5) radicals per cubic centimeter (1sigma uncertainty). These 7 years of gas chromatographic measurements, which comprise about 60,000 individual calibrated real-time air analyses, provide the most accurate estimates yet of the trends and lifetime of methylchloroform and of the global average for tropospheric hydroxyl radical levels. Accurate determination of hydroxyl radical levels is crucial to understanding global atmospheric chemical cycles and trends in the levels of trace gases such as methane.

Evaluation of Volatile Organic Compounds at Petrochemical Complexes in Iran

“…Ethylbenzene and xylene are more reactive than benzene and toluene; therefore, their concentrations decrease quickly in the ambient air when photochemical reactions take place. Since the half-life of benzene is greater than that of toluene and xylene (17) and since solar radiation is more predominant in the summer than in the winter, the B/T and B/X ratios increase in the winter, mainly due to a decrease in the reactivity of benzene. In addition, the longer half-life and lesser reactivity of ethylbenzene along with less sunlight in the winter lead to an increase in EB/T ratio in the winter.…”

Three‐dimensional climatological distribution of tropospheric OH: Update and evaluation

“…Ever since Levy [1971] presented a model of tropospheric chemistry with the hydroxyl radical as the key species, efforts have continued to estimate accurately 1986; Prinn et al, 1983Prinn et al, , 1987Prinn et al, , 1992Prinn et al, , 1995 Thompson [1994] for a review of studies of tropospheric OH through the early 1990s).…”

Methane Emissions Deduced from a Two-Dimensional Atmospheric Transport Model and Surface Measurements

“…The CH3CCl3 concentrations calculated for Adrigole/Mace Head, Ireland (52/53N, 1, 0W), Cape Meares, Oregon (45N, 124W), Ragged Point, Barbados (13N, 59W), Point Matatula, American Samoa (14S, 170E), and Cape Grim, Tasmania (40S, 144E) are shown in Fig. 1, together with the measurement results (Prinn et al, 1987(Prinn et al, , 1992(Prinn et al, , 1995. As seen from this figure, the observed concentration has increased steadily at all sites.…”