SOURCES AND ATMOSPHERIC DISTRIBUTION OF PARTICULATE AND GAS-PHASE BORON

Atmospheric samples were collected during warm and cold weather condit ions at continental, coastal and marine sites. Source sampling was per formed at a coal-fired power plant and several volcanic sites. Atmosph eric gas-phase and particulate boron concentrations were determined by neutron capture prompt-gamma activation analysis and compared to meas urements from other studies. Rain and snow samples collected at one co ntinental site were analysed for soluble and insoluble B. Volcanic dep osit and ash samples were also analysed for B. The tropospheric burden s 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 reaso nably well with previously reported upper limits. About 65-85 % of tot al B source strength can be attributed to the oceans, and 8-20% to coa l, agricultural, fuelwood and refuse burning. Volcanism may contribute 6-15% of the total, but accurate source estimates are difficult. Tota l global B removal from the atmosphere by wet and dry deposition was e stimated to be (530-700) x 10(10) gyr-1, a factor of 2 lower than prev iously reported but in fairly good agreement with the global total B s ource estimate of (200-530) x 10(10) gyr-1.