2002 Denver Annual Meeting (October 27-30, 2002)

Paper No. 8
Presentation Time: 10:00 AM


HOLMES, Charles W. and MILLER, Ryan, US Geol Survey, St. Petersburg, FL 33701, cholmes@usgs.gov

It has been recognized that Saharan dust is introduced into ecosystems bordering the western Atlantic Ocean. The composition of material collected in Africa, from “dust-events” that crossed the Azores, and collection sites, such as cisterns in the Caribbean and the Eastern United Stated reveal that arsenic and other metals are transported within the dust. The arsenic content of dust material collected in Mali, North Central Africa, was approximately 17 mg/kg. Arsenic in a cistern collected on eastern-most end of St. John, U.S. Virgin Islands was about 38 mg/kg. The largest aerosol data set available with arsenic data is the IMPROVE (Interagency Monitoring of Protected Visual Environments) data set. In addition to a Virgin Islands site, the IMPROVE program established three sites in Florida, one in Everglades National Park in south Florida, one a Chassahowitzka National Wildlife Refuge along the Central Florida Gulf Coast and one in the Okefenokee Wildlife Refuge on the Florida/Georgia border. Arsenic, in the 289 samples, ranged from 0.5 to 44 mg/kg, with a mean of 17 mg/kg. In the Everglades National Park in south Florida, the data suggests approximately 50% of the arsenic is associated with other than soil material. At Chassahowitzka Wildlife Refuge in central Florida, approximately 25% were linked with the soil fraction. At the Okefenokee Wildlife Refuge, approximately 2.5% had an association with soil; the remaining fraction had a strong relationship to organic carbon concentrations. Of all the sites, Chassahowitzka samples appeared to have the highest arsenic concentrations ranging from 0.5 to 198 mg/kg with a mean value of 33 mg/kg. Recent studies have demonstrated that there is a high degree on bioaccumulation of arsenic in a fern commonly found in Florida. Time series analysis of the arsenic in the aerosols indicates a strong link between fire occurrences and aerosol arsenic. In addition, ground water data shows that arsenic in central Florida is highest in the region of high aerosol arsenic. It is hypothesized, that there is a link between the dust, and ground water, with the dust transporting the arsenic to Florida, which is flushed from the troposphere by summer storms, it is accumulated in the plants which subsequently burn during the dry winter season becoming available to leaching into the groundwater systems.