Boron in coastal North Florida rainfall

Boron concentrations of coastal North Florida rainfall averaged 8.3, 12, and 7.0 μg 1−1 for summer showers, winter frontal activity, and samples collected sequentially during tropical storm Becky, respectively. B/Na ratios were 11×10−3 and 5×10−3 in summer and winter samples, respectively. Mean calculated B enrichments ENa(B) for summer and winter sample sets were 32 and 11, respectively. A surprisingly constant concentration of ‘excess’ B above that expected from direct seawater injection of approximately 6 μg 1−1 was observed in the sequential Becky samples. The lower winter B/Na ratios, and thus the calculated ENa(B) values, appear related to higher Na concentrations; however, several alternative hypotheses can be advanced to explain the results, including greater particulate sea-salt injection during winter months, incorporation of soil materials with a B/Na ratio above the seawater value, and possible influences of temperature variation on gaseous B incorporation in rain and evaporation from the sea surface.