Transfer of atmospheric boron from the oceans to the continents: An investigation using precipitation waters and epiphytic lichens

Abstract

[1] Abstract: The variation of B concentration in atmospheric deposition was studied from the analysis of 35 individual rain events, 17 snow packs, and 17 lichens sampled over NE North America (south from Hudson Bay) and Asia (from the coast of Bangladesh to the high Himalayas of Nepal). Rain samples show a range of B concentration between 0.3 and 9.4 mg/L (average of 1.8 1.7 mg/L), excluding two rains with higher B contents of 17 and 37.5 mg/L, most likely reflecting anthropic contamination. Snowpacks and lichens which average atmospheric deposition over periods of a few months to a few years show a smaller range of variation, from 0.1 to 2.3 mg/L (average 1.1 0.8 mg/L) for snowpacks and from 1 to 25.9 ppm for lichens. The lichens have elemental ratios (such as B/Cl) similar to the average of rains, showing that they are good monitors of atmospheric B deposition without significant biofractionation of elements. This is also demonstrated by their halogen contents, which follow the systematics of the atmospheric distribution of these elements previously derived from the study of rains and atmospheric particles. Though individual rains do not show systematic decrease in B concentration with distance to the sea, this behavior is clearly shown by samples having longer integration times, snowpacks, and lichens. The snow and lichen data show that seawater is a major source of atmospheric B. Using the lichen data, the enrichment factor (normalized to Na) of marine air masses relative to seawater is estimated to be $13 (average B/Na of 5.6 Â 10 À3 ). This implies that the fractionation factor of atmospheric suspended marine particles relative to seawater (F X = (X/Na) particle / (X/Na) seawater ) is 0.177. Thus B transfer from seawater to the atmosphere occurs mostly via degassing of sea salts, the residence time of gaseous B being estimated at 15.9-fold that of particulate B. The distribution of B in the atmosphere between gaseous B and degassed sea salts can be used to model the large range of B concentrations measured in single rain events by selective removal of one of the two B components. In this model, unfractionated marine air masses can reach the continents with very variable B concentrations, between $0.2 and $20 mg/L.

Boron isotopic composition of atmospheric precipitations and liquid–vapour fractionations

“…Principal sources are usually considered to be (1) for gaseous boron: evaporation of sea water, both directly and indirectly via sea water aerosol evaporation, and volcanic emissions, and (2) for particulate boron: salts from evaporated sea water aerosols, volcanic and terrestrial dusts. As suggested by the systematics of the B, Cl and Na contents of epiphytic lichens which average atmospheric precipitations over periods of a few months to a few years, the variations of the B contents and B/Na ratios of precipitation reflect a selective scavenging of particulate B relative to gaseous B (Rose et al, 2000a). The lichen data also indicate that the atmospheric residence time of gaseous B is $16 times that of particulate B in agreement with previous estimates (obtained from rain data) which are of 19-36 days and of 2-6 days for gaseous and particulate B, respectively (Fogg and Duce, 1985).…”

“…Boron is a quite variable trace constituent in the atmosphere with concentrations usually between 0.2 and 300 ppb (e.g., Fogg and Duce, 1985;Duce, 1996;Miyata et al, 2000;Rose et al, 2000a). It is present in both gaseous and particulate forms with the former probably representing more than 90-95% of the total (Fogg and Duce, 1985).…”

Carências de boro no interior - norte e centro - de Portugal

“…Com efeito, a ajuizar pela distribuição dos locais onde a carência de B foi identificada por Branco (1961) no seu estudo exploratório, ficou evidente a maior ocorrência da deficiência de B no interior do país. O mesmo se poderá dizer acerca dos registos de Dias (1953b), ao constatar o desaparecimento dos indícios da 'maromba' nas videiras enviadas do Douro e plantadas em Sacavém em solos derivados de rochas carbonatadas e areníticas, as quais, à partida, eram pobres em B. Nas zonas costeiras, devido à proximidade do mar, as adições de B através da atmosfera são naturalmente mais elevadas (Shorrocks, 1997;Rose et al, 2000).…”

Inferring the effect of catchment complexity on mesoscale hydrologic response

“…For Ba and B, a secondary concentration minimum occurred at the subsidiary peak at Herborn on the sixth day of the event ( Figure 7b). Unlike Ba and B, the behavior of U appeared to reflect the large discharge from Rose et al [2000]. The concentrations of Rb < 1 mg/l and U < 0.01 mg/l were divided by 2 in order to account for the limit of determination.…”

“…Lacking site-specific data for precipitation chemistry, its chemical composition was approximated according to Plessow et al [2001] for continental Europe. Boron concentrations in rain were drawn from Rose et al [2000]. Mean daily discharge data were used from the gauging stations Asslar, Dillenburg and Herborn (see Figure 1b for location and Figure 2b for hydrographs) operated by the HLUG (Hessisches Landesamt für Umwelt und Geologie).…”