Influence of sea salt aerosols and long range transport on precipitation chemistry at El Verde,Puerto Rico

The chemistry of bulk precipitation was measured from November 1983 to September 1987 at El Verde in the Luquillo Experimental Forest, Puerto Rico. Wet-only precipitation was also analyzed as part of the National Atmospheric Deposition Program from 1984 to 1987. Volume-weighted mean pH was 5.14 in bulk precipitation and 5.12 in wet precipitation. Concentrations of most species were correlated negatively with weekly rainfall. Sea salt aerosols contributed most of the Na⁺, Cl⁻, Mg²⁺ and K⁺ found in wet and bulk precipitation; sulfate and calcium, however, were derived primarily from non-sea salt sources. Due to the high rainfall (3.4 m annually during the study period) and close proximity of the study site to the ocean, deposition rates of the major cations and anions were high relative to many other tropical sites. Precipitation chemistry at El Verde appears to be affected by several factors. During summer, Saharan dusts contribute a significant portion of the excess Ca²⁺, K⁺ and Mg²⁺. During winter months, cold fronts may transport SO₄²⁻ and NO₃⁻ from North America and the western part of Puerto Rico to the sampling site.