Date of Award
Doctor of Philosophy in Oceanography
Robert A. Duce
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. The true amount of organic phosphorus could not be extracted from the North Atlantic aerosol data.
A field study in Narragansett Bay, R.I. using a bubble interfacial microlayer sampler showed that phosphorus is carried into the atmosphere on the drops from bursting bubbles and that it is enriched relative to sodium on these droplets. Enrichment of organic phosphorus ranged between 60-150, about ten times gr-eater than that of reactive phosphorus. The source of this phosphorus appeared to be the sea-surface microlayer. The data from samples-collected over the phosphorus-rich waters of the Peru current support the existence of the fractionation process in nature. A strong correlation was found between organic phosphorus and sodium in these samples. The average enrichment was 160.
The estimated global burden of particulate phosphorus in the atmosphere is 2.8 x 109 g. The inputs of phosphorus to the atmosphere are estimated to be: crustal, ~380 x 1010 g y-1, marine, ~33 x 1010 g y-1, and anthropogenic, ~46 x 1010 g y-1. Transport of crustal and anthropogenic material to the oceans is estimated to be ~100 x 1010 g y-1, while transport of marine phosphorus to the continents is ~3 x 1010 g y-1. These estimates are only good to a factor of two or three. An estimated ~20 x 1010 g y-1 of crustal phosphorus is readily released upon contact with ocean water. This amounts to about 10% of the riverine input of dissolved phosphorus to the oceans.
Graham, William F., "Atmospheric Pathways of the Phosphorus Cycle" (1977). Open Access Dissertations. Paper 1342.