Sources, Levels, and Reactions of Boron in Florida Waters

Abstract

Abstract Levels of boron in Florida natural waters are generally low, (median value <50 µ g/liter for 120 samples) and not of toxic concern. However, municipal sewage effluents have levels high enough (150–800 µ g/liter) to cause phytotoxicity, at least to sensitive plants such as citrus. Detergent use of borate softeners and perborate bleaches is evidently the source of the elevated boron levels in sewage. Boron concentrations in rainfall increase with proximity to either coast in peninsular Florida, reaching levels of 80–90 µ g/liter. Marine aerosols are thus implicated as an important natural source in the boron cycle of Florida. Model ecosystem studies indicated little bioaccumulation and no toxic hazard at levels expected in natural waters. Interactions of boron with clays and with dissolved organic color (humates) were found to be small, and boron behaves as an essentially conservative element in natural waters.