Factors regulating the distribution of boron in water in the River Dee catchment in north east Scotland

Boron concentrations have been measured on four occasions, two under high discharge conditions and two under low discharge conditions, in 59 subcatchments of the River Dee catchment in north east Scotland. Correlations between B concentration and % land use cover, other river water constituents and distance from the coast have been examined. The results, especially the strong link with Na and Cl concentrations and their distributions, suggest that a primary source of B in relatively unpolluted river water in north east Scotland is input in precipitation, ultimately derived from oceanic spray. However, precipitation inputs alone do not account for the observed B:Cl ratio in river water, and other atmospheric inputs must also be important. It is suggested that inputs in precipitation and dry deposition approximately balance outputs in river water, except where agricultural land use disrupts the biogeochemical cycling of B.