Dry and Wet Atmospheric Deposition Composition in Southwest Florida: Environmental and Health Implications

Abstract

Southwest Florida is one of the most rapidly growing regions of the United States and has been impacted over the past decade with water-quality issues and some associated health problems. The ionic ratios of the dust measured in southwest Florida vary significantly from those on the Florida east coast and in the Caribbean. The metals concentrations reported herein are enriched in potassium and calcium from local sources. Atmospheric deposition of metals and nutrients appears to have potential impacts on both indirect health problems and environmental issues of concern, particularly harmful algal blooms. However, no significant past research has been performed on measurement of the concentration of either metals including the micronutrient iron or nutrient concentrations occurring in atmospheric dry and wet fallout in southwest Florida. Measurements of the composition of key metals and nutrients were made over a one-year period. Concentrations of total phosphorus in the dust ranged from 0–80.5 mg/kg with an average of 4 mg/kg and in rainfall from 1–15.8 чg/L with an average of 4 mg/kg. Nitrate ranged from 0–746 чg/L with an average of 114.4 чg/L in rainfall in a soluble form, and from 1.3 to 718 mg/kg with an average of 209.9 mg/kg in an insoluble form. Ammonia was measured to range from 1.4 to 658 mg/kg with an average of 101.4 mg/kg in rainfall. Iron was found in the dust at concentrations ranging from 0–81 mg/kg with an average of 3.8 mg/kg and in rainfall from 0–125.7 mg/kg with an average of 3.0 mg/kg. While the measured nutrient and iron concentrations are not likely to initiate a harmful algal bloom, they are likely to sustain an existing bloom. Global climate change may exacerbate the atmospheric aerosol issue by increased wind speeds over Africa associated with longer term drought conditions caused by atmospheric temperature increases.