SOURCES AND ATMOSPHERIC DISTRIBUTION OF PARTICULATE AND GAS-PHASE BORON

Atmospheric samples were collected during warm and cold weather conditions at continental, coastal and marine sites. Source sampling was performed at a coal-fired power plant and several volcanic sites. Atmospheric gas-phase and particulate boron concentrations were determined by neutron capture prompt-gamma activation analysis and compared to measurements from other studies. Rain and snow samples collected at one continental site were analysed for soluble and insoluble B. Volcanic deposit and ash samples were also analysed for B. The tropospheric burdens for particulate and gas-phase B were estimated to be 0.6 x 10(10) g and (6-11) x 10(10) g, respectively, with the latter about a factor of 3 lower than previous estimates. Global anthropogenic particulate and gas-phase B source estimates were consistent with previous estimates, and natural particulate and gas-phase B source estimates agreed reasonably well with previously reported upper limits. About 65-85 % of total B source strength can be attributed to the oceans, and 8-20% to coal, agricultural, fuelwood and refuse burning. Volcanism may contribute 6-15% of the total, but accurate source estimates are difficult. Total global B removal from the atmosphere by wet and dry deposition was estimated to be (530-700) x 10(10) gyr-1, a factor of 2 lower than previously reported but in fairly good agreement with the global total B source estimate of (200-530) x 10(10) gyr-1.