Atmospheric Pathways of the Phosphorus Cycle

Abstract

The flow of particulate phosphorus through the atmosphere has been studied: The goal of the work was to deduce the magnitude and direction of the fluxes of phosphorus through the atmosphere and to identify the sources of this phosphorus. Samples of atmospheric particulate matter were collected at urban, rural, and remote continental sites, at remote island sites, and on ship-board over the Atlantic and Pacific Oceans Samples of precipitation and. dry fallout were collected at sampling sites at Narragansett, R.I. and Bermuda. Total phosphorus was determined on both the samples of atmospheric particulate matter and the deposition samples. In addition, the amounts of phosphorus considered to be "organic" and "reactive" were determined on the aerosol samples. Sodium, aluminum, and vanadium were also determined on the aerosol samples. These elements were used as tracers for the sea salt, crustal, and anthropogenic fossil fuel combustion portions of the aerosol. The concentration of total particulate phosphorus in the atmosphere ranged from ~100 ng m-3 in New York City to ~0.2 ng m-3 at the geographic South Pole and down to ~0.2 ng m-3 in the remote South Pacific. Typical concentrations in other areas were: Narragansett, R.I., 20 ng m-3; Northwest Territories, Canada, 1.2 ng m-3; the Western North Atlantic between North American and Bermuda, 7 ng m-3; over the Peru current near the coast of Peru, 8 ng m-3; and in the marine air near the islands of Hawaii and Samoa, 0.5 ng m-3. Particulate phosphorus in the marine air near Hawaii and Samoa came from both continental and oceanic sources. The reactive phosphorus fraction was most closely associated with crustal material. An acid soluble inorganic fraction appears to have a marine source which could not be identified. The organic phosphorus fraction did not correlate with either aluminum or sodium. The material may have been derived from more than one source. The particulate phosphorus found over the North Atlantic near the northwest coast of Africa appeared to come from the Sahara desert. Phosphorus to iron ratios in this aerosol agreed well with the ratios found in a desert soil from Libya. Much of the phosphorus in the marine air over the western North Atlantic appeared to be of anthropogenic origin. A strong correlation was found between phosphorus and vanadium, both in the reactive and organic phosphorus fractions. Much of the phosphorus in the nominally "organic" fraction was evidently a water insoluble organic form.