Distribution of boron in the environment.

The findings of a study to identify and quantify the orders of magnitude for major reservoirs and flows of boron (B) in the environment are outlined. The orders of magnitude for B reservoirs and flows arising through natural processes, such as the hydrological cycle and volcanism, are compared with those arising from anthropogenic activities, such as coal combustion and the extraction and use of borates for commercial purposes. The major stores and reservoirs for B have been identified, in order of magnitude, as the continental and oceanic crusts (10(18) kg B), the oceans (10(15) kg B), groundwater (10(11) kg B), ice (10(11) kg B), coal deposits (10(10) kg B), commercial borate deposits (10(10) kg B), biomass (10(10) kg B), and surface waters (10(8) kg B). The largest flows of B in the environment arise from the movement of B into the atmosphere from oceans, at between 1.3 x 10(9) kg and 4.5 x 10(9) kg B per annum. Other hydrological flows are also important. Drainage from soil systems into groundwaters and surface waters accounts for between 4.3 x 10(8) kg and 1.3 x 10(9) kg B per annum. B mining and volcanic eruptions represent the next most significant B flows, accounting for approx 4.0 x 10(8) kg and 3.0 x 10(8) kg B, respectively.