Differences in aerosol trace metals between the northern Caribbean and southeastern United States.

Five Interagency Monitoring of Protected Visual Environments (IMPROVE) monitoring stations in the southeastern United States and the U.S. Virgin Islands (U.S.V.I.), clearly show the metals in aerosols are derived from two different sources. The aerosols are collected by IMPROVE samplers and passed through a series of filter cassettes that are analyzed at University of California, Davis laboratories. Teflon, nylon and quartz filters were used to collect fine particles, PM_2.5, while a fourth filter of Teflon collected PM₁₀ particles. The Teflon filters that collected PM₁₀ particles were analyzed using gravimetric analysis. The second Teflon filter was used to measure elements and mass; Particle Induced X-Ray Emission (PIXE) and X-Ray Fluorescence (XRF) were used to measure the concentrations of the elements from sodium to lead while Proton Elastic Scattering Analysis (PESA) was used to measure hydrogen concentrations. Nylon filters were used to measure nitrate, sulfate and chloride concentrations by ion chromatography. The average yearly concentrations in η g m^-3 of copper, iron, potassium and zinc, one of the elemental groups tested by IMPROVE, in the U.S.V.I. aerosols are 0.20 η g m^-3, 176.49 η g m^-3, 89.32 η g m^-3and 1.61 η g m^-3. In Sipsy Wilderness, Alabama the concentrations are 1.37 η g m^-3, 50.06 η g m^-3, 61.03 η g m^-3and 9.86 η g m^-3respectively. Statistical analysis of the data indicates that the composition of the aerosols at the more northern sites of Sipsy Wilderness, Alabama, Okefenokee National Wildlife Reserve, Georgia and Chassahowitzka Wildlife Refuge, Florida are distinctly different than the Everglades National Park (E.N.P.), Florida and the U.S.V.I. Correlations of elements at the U.S.V.I. and E.N.P. sites are similar and the correlation coefficients are strong (> 0.75) for elements considered to be of terrestrial source. At the northern sites, there is no relation among the metals. Examination of the annual data with cluster analysis techniques show that the strong relations of elements between the U.S.V.I. and E.N.P. existed during 1995, 1996 and 1997. In 1998 a strong El Nino-Southern Oscillation event altered the airflow and caused the relation between the U.S.V.I. and E.N.P. to break down. During this period the aerosols collected in the E.N.P. were similar in composition to those found in the northern sites. This analysis of aerosol composition demonstrated that during years without El Nino events, the airflow and thus the aerosols in southern-most Florida are related to the sources of deposited material in the Caribbean northern region. Material deposited north of central Florida is for the most part similar to that found in the southeastern United States.