A model for the photochemistry of the global troposphere constrained by observed concentrations of H2O, O3, CO, CH4, NO, NO2, and HNO3 is presented. Data for NO and NO2 are insufficient to define the global distribution of these gases but are nonetheless useful in limiting several of the more uncertain parameters of the model. Concentrations of OH, HO2, H2O2, NO, NO2, NO3, N2O5, HNO2, HO2NO2, CH3O2, CH3OOH, CH2O, and CH3CCl3 are calculated as functions of altitude, latitude, and season. Results imply that the source for nitrogen oxides in the remote troposphere is geographically dispersed and surprisingly small, less than 107 tons N yr−1. Global sources for CO and CH4 are 1.5 × 109 tons C yr−1 and 4.5 × 108 tons C yr−1, respectively. Carbon monoxide is derived from combustion of fossil fuel (15%) and oxidation of atmospheric CH4 (25%), with the balance from burning of vegetation and oxidation of biospheric hydrocarbons. Production of CO in the northern hemisphere exceeds that in the southern hemisphere by about a factor of 2. Industrial and agricultural activities provide approximately half the global source of CO. Oxidation of CO and CH4 provides sources of tropospheric O3 similar in magnitude to loss by in situ photochemistry. Observations of CH3CCl3 could offer an important check of the tropospheric model and results shown here suggest that computed concentrations of OH should be reliable within a factor of 2. A more definitive test requires better definition of release rates for CH3CCl3 and improved measurements for its distribution in the atmosphere.

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Tropospheric chemistry: A global perspective

This review shows that thermodynamic and kinetic constraints largely prevent large-scale methanogenesis in the open ocean water column. One example of open-ocean methanogenesis involves anoxic digestive tracts and fecal pellet microenvironments; methane released during fecal pellet disaggregation results in the mixed-layer methane maximum. However, the bulk of the methane in the ocean is added by coastal runoff, seeps, hydrothermal vents, decomposing hydrates, and mud volcanoes. Since methane is present in the open ocean at nanomolar concentrations, and since the flux to the atmosphere is small, the ultimate fate of ocean methane additions must be oxidation within the ocean. As indicated in the Introduction and highlighted in Table 3, sources of methane to the ocean water column are poorly quantified. There are only a small number of direct water column methane oxidation rates, so sinks are also poorly quantified. We know that methane oxidation rates are sensitive to ambient methane concentrations, but we have no information on reaction kinetics and only one report of the effect of pressure on methane oxidation. Our perspective on methane sources and the extent of methane oxidation has been changed dramatically by new techniques involving gene probes, determination of isotopically depleted biomarkers, and recent 14C-CH4 measurements showing that methane geochemistry in anoxic basins is dominated by seeps providing fossil methane. The role of anaerobic oxidation of methane has changed from a controversial curiosity to a major sink in anoxic basins and sediments. © 2007 American Chemical Society.

/pdf/oceanic-methane-biogeochemistry-12rf80pqzx.pdf

Oceanic methane biogeochemistry.

(1983). Ionizing Radiation: Sources and Biological Effects. International Journal of Radiation Biology and Related Studies in Physics, Chemistry and Medicine: Vol. 43, No. 5, pp. 585-586.

Ionizing Radiation: Sources and Biological Effects

Trace metals in atmospheric deposition: A review and assessment

"Support for this paper was provided by funding from the North Temperate Lakes LTER program, NSF DEB‐0822700."

/pdf/the-ecology-of-methane-in-streams-and-rivers-patterns-3a86lcsz2f.pdf

The ecology of methane in streams and rivers: patterns, controls, and global significance

Trichlorofluoromethane (CCl3F) measurements in the troposphere over the Atlantic in 1971 and over the Pacific in 1972 and 1974 were compared. A rapid increase of CCl3F in the troposphere is evident. The observed increase of CCl3F between 1971 and 1974 is proportional to the increase of industrially produced amounts of CCl3F in the same time period.

http://science.sciencemag.org/content/sci/187/4179/832.full.pdf

Trichlorofluoromethane in the Troposphere, Distribution and Increase, 1971 to 1974.

Mercury. Short-term storage of natural waters

New data support the contention that the mercury content of Greenland glacial ices has not increased dramatically in recent years but rather is distributed nonhomogeneously through the ice sheet.

http://science.sciencemag.org/content/sci/181/4102/843.full.pdf

Mercury in the greenland ice sheet: further data.

Anomalous fluoride concentrations in the North Atlantic

Trace gas measurements (222Rn, CO, CH4), weather satellite images, and conventional meteorological observations established the existence of a pronounced land and sea breeze regime at the Sepik River coast. Its interaction with the synoptic wind field was evaluated. Considerable natural variability of atmospheric CO and CH4 was observed. CCl4 behaved similarly to man-made CCl3F.

P. E. Wilkniss

Papers

Trichlorofluoromethane in the Troposphere, Distribution and Increase, 1971 to 1974.

Mercury. Short-term storage of natural waters

Mercury in the greenland ice sheet: further data.

Anomalous fluoride concentrations in the North Atlantic

Atmospheric trace gases and land and sea breezes at the Sepik River coast of Papua New Guinea