Date of Award

1978

Degree Type

Thesis

Degree Name

Master of Science in Oceanography

Department

Oceanography

First Advisor

Robert A. Duce

Abstract

Dry deposition, rainfall and atmospheric particulate samples collected at a coastal Rhode Island site, and aboard RV/Trident over the North West Atlantic Ocean were analyzed for Na and Mg in order to understand the rate and mechanisms of removal of atmospheric sea salt. Perkin Elmer atomic absorption spectrophotometer models 303 and 360 were used for the analyses. Samples collected at the R.I. coastal site were divided into 3 different categories, namely, "marine", "land" and "mixed" samples depending on the local surface wind direction during sampling. Based upon the Mg/Na ratio , it appears that most of the Na and Mg in "marine" samples were derived from the ocean while "land" samples essentially consist of Na and Mg of crustal origin and "mixed" samples were a combination of the two.

The rate of wet removal of atmospheric Na and Mg, calculated from "marine" and "land" samples and the rate of dry deposition of sea salt calculated only from "marine" samples, appear to be proportional to the wind speed. Consideration of the Mg/Na ratios in rainfall and dry fallout samples observed from the ''marine", "mixed" and "land" samples categories, suggest that rainfall scavenges sea salt Na and Mg more efficiently than crustal particles.

The annual global removal rate of atmospheric sea salt was estimated at ~3.0x1015 g/yr.60% of this is removed by rainfall and the rest by dry deposition. Of the total cyclic sea salt removed annually over the globe, less than 7% is deposited over land. 90% of this is removed by rainfall and the rest by dry deposition.

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