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AN EQUATORIAL PACIFIC RAIN EVENT: INFLUENCE ON THE DISTRIBUTION OF IRON AND HYDROGEN PEROXIDE IN SURFACE WATERS
Hanson, A. K., N. W. Tindale, AND M. AbdelMoati. AN EQUATORIAL PACIFIC RAIN EVENT: INFLUENCE ON THE DISTRIBUTION OF IRON AND HYDROGEN PEROXIDE IN SURFACE WATERS. MARINE CHEMISTRY 75:68-88, (2001).
Methods are described for measuring changes in atmospheric O2 concentration with emphasis on gas handling procedures. Cryogenically dried air samples are collected in 5 L glass flasks at ambient pressure and analyzed against reference gases derived from high-pressure aluminum tanks. Fractionation effects are minimized by avoiding pressure and flow variations throughout the gas-handling system. The overall external reproducibility is approximately ?3.3 per meg, with systematic errors associated with collecting samples and with storing them for 1 year reduced to the level of 3 per meg or smaller. The demonstrated short-term reproducibly of air delivered from high-pressure tanks is ? 1.5 per meg, with the composition changing by at most 5 per meg by surface desorption reactions as the tank is depleted to below 3500 kPa. A 9-year survey of a suite of six reference gases showed no systematic long-term trends in relative O2 concentrations to the level of 5 per meg. Results are presented from samples collected at Cape Grim (41 S) Macquarie Island (54 S) and the South Pole Station (90 S). From measurements spanning 1991-1995 it is found that the O2 concentrations at the South Pole are on average 3.6 ? 1.2 per meg higher than at Cape Grim. This result runs contrary to the expectation that the air at high southern latitudes should be depleted in O2 as a result of O2 uptake from the Southern Ocean and may require the existence of unknown O2 sources near Antarctica or unexpected atmospheric transport patterns.