K.A. Brice

Bio: K.A. Brice is an academic researcher. The author has contributed to research in topics: Radiation chemistry & Radical. The author has an hindex of 3, co-authored 3 publications receiving 393 citations.

An important ground surface sink for atmospheric nitrous oxide

Abstract: ONE of the more remarkable achievements of atmospheric chemistry is the identification by Crutzen1, in 1970, of nitric oxide (NO) as the main natural agent for the destruction of ozone produced photochemically in the stratosphere. The principal source of stratospheric NO is the reaction of excited oxygen atoms (O1D) with nitrous oxide (N2O)2, present as a normal constituent of the Earth's atmosphere. N2O was first observed, in 1938, by Adel3 in the absorption bands in the 7.8 µm region of the solar spectrum, but knowledge of its atmospheric life cycle is still very incomplete because of the few measurements available of its atmospheric concentration and limited information on atmospheric sources and sinks. The soil has been suggested as a major source of atmospheric N2O4 and the ocean has been proposed to act both as a source5 and as a sink6. The only sink so far positively established by atmospheric measurement lies in the stratosphere, being predominantly photodissociative in nature with an additional contribution from the chemical reaction with excited oxygen atoms4,7. We report here evidence for the existence of an appreciable, but unidentified, ground surface sink mechanism.

Future global warming from atmospheric trace gases

Abstract: Human activity this century has increased the concentrations of atmospheric trace gases, which in turn has elevated global surface temperatures by blocking the escape of thermal infrared radiation. Natural climate variations are masking this temperature increase, but further additions of trace gases during the next 65 years could double or even quadruple the present effects, causing the global average temperature to rise by at least 1 °C and possibly by more than 5 °C. If the rise continues into the twenty-second century, the global average temperature may reach higher values than have occurred in the past 10 million years.

A global three-dimensional model of the tropospheric sulfur cycle

Abstract: The tropospheric part of the atmospheric sulfur cycle has been simulated in a global three-dimensional model. The model treats the emission, transport, chemistry, and removal processes for three sulfur components; DMS (dimethyl sulfide), SO2 and SO4 2− (sulfate). These processes are resolved using an Eulerian transport model, the MOGUNTIA model, with a horizontal resolution of 10° longitude by 10° latitude and with 10 layers in the vertical between the surface and 100 hPa. Advection takes place by climatological monthly mean winds. Transport processes occurring on smaller space and time scales are parameterized as eddy diffusion except for transport in deep convective clouds which is treated separately. The simulations are broadly consistent with observations of concentrations in air and precipitation in and over polluted regions in Europe and North America. Oxidation of DMS by OH radicals together with a global emission of 16 Tg DMS-S yr−1 from the oceans result in DMS concentrations consistent with observations in the marine boundary layer. The average turn-over times were estimated to be 3, 1.2–1.8, and 3.2–6.1 days for DMS, SO2, and SO4 2− respectively.

Chemical mechanisms of acid generation in the troposphere

Abstract: Diverse chemical pathways in the troposphere convert sulphur and nitrogen oxides and organic compounds into acids, involving the gas phase, the liquid phase (cloud, fog and rain water) and, possibly, certain suspended aerosols. The rates of acid generation are critically affected by the extent of generation of the oxidizing species and the kinetics of the reactions. Precipitation in the eastern United States shows a strong seasonal variation in deposition of sulphates in contrast to nitrates. Computer simulations can now rationalize the observed seasonal trends. Recent tropospheric measurements of gaseous hydrogen peroxide show that this gas is a major oxidant leading to sulphuric acid generation in cloud water.