Chloromethane is the most important natural carrier of chlorine to the stratosphere. From a newly determined carbon isotope effect of −11.2 ‰ for the tropospheric loss of CH₃Cl we derive a tropical rainforest CH₃Cl source of 670 ± 200 Gg a⁻¹, 60 % smaller than previous estimates. A revision of previous bottom-up estimates using above-ground biomass instead of rainforest area strongly supports this lower estimate. Our results suggest a large unknown tropical value of 1530 ± 200 Gg a⁻¹.

We present the first observations of the oxygen-17 excess of atmospheric nitrate (Δ¹⁷O(NO⁻₃)) collected in Beijing haze to reveal the relative importance of different nitrate formation pathways. We found that nocturnal pathways (N₂O₅ + H₂O/Cl^– and NO₃ + HC) dominated nitrate production during polluted days (PM_2.5 ≥ 75 μg m^–3), with a mean possible fraction of 56–97 %.

Chloromethane is involved in stratospheric ozone depletion, but detailed knowledge of its global budget is missing. In this study stable hydrogen isotope analyses were performed to investigate the dominant loss process for atmospheric chloromethane with photochemically produced hydroxyl radicals. The findings might have significant implications for the use of stable isotope signatures in elucidation of global chloromethane cycling.

The photochemical oxidation of organic compounds in the atmosphere results in the formation of important secondary pollutants such as ozone and fine particles. The extent of oxidation the organic compounds have been subjected too since there emissions is essential is key for understanding the formation of secondary pollutants. This paper demonstrates that measurements of the carbon isotope ratios allow determining the extent of photochemical processing for individual compounds.

We present experimental kinetic isotope effects (KIE) for the OH oxidation of CH₃D and ¹³CH₃D and their temperature dependence. Our determination of the ¹³CH₃D + OH KIE is novel and we find no "clumped" isotope effect within the experimental uncertainty.

We evaluate isotopic composition of NO3- in different environments across East Antarctica. At high snow accumulation sites, isotopic ratios are suggestive of preservation of NO3- deposition. At low accumulation sites, isotopes are sensitive to both the loss of NO3- due to photolysis and secondary formation of NO3- within the snow. The imprint of post-depositional alteration is not uniform with depth, making it difficult to predict the isotopic composition at depth from near-surface data alone.

Stratospheric ozone protects life on Earth from harmful UV-B radiation. Chlorofluorocarbons (CFCs) are man-made compounds which act to destroy this barrier. This paper presents (1) the first measurements of the stratospheric δ(37Cl) of CFCs -11 and -113; (2) the first quantification of long-term trends in the tropospheric δ(37Cl) of CFCs -11, -12 and -113. This study provides a better understanding of source and sink processes associated with these destructive compounds.