BORON CONCENTRATIONS IN SALINE LAKES: GREAT BASIN, USA; SASKATCHEWAN, CANADA; AND MCMURDO DRY VALLEYS, ANTARCTICA

Boron concentrations were measured in saline closed-basin lakes of McMurdo Dry Valleys (MCM), Antarctica; Great Basin, United States; and Saskatchewan, Canada, to better understand controls on the sources, transport, and fate of the element boron within different climatic saline lake systems. The lakes under investigation are located in semi-arid to arid regions, and each lake’s water balance is controlled by inputs of springs, streams, and limited precipitation, while outputs are from evaporation or sublimation. MCM is the most extreme arid environment of these sites with a mean annual temperature of -20ºC and annual precipitation of <5 cm per year. This is the largest ice-free area in Antarctica, and during the austral summer, glacial meltwater streams form and flow into ice-covered closed-basin lakes. Great Basin and Saskatchewan saline lakes are remnants of larger lakes formed during a wetter climate. We measured B concentrations ranging from 0.009 mM (surface water Lake Hoare, MCM) to 9.7 mM (Abert Lake, Great Basin). In comparison with published results, Mono Lake, Great Basin, has one of the highest reported B concentrations in terrestrial waters, 29.6 mM (Steiman et al. 2004). Of the Antarctic lakes, the hypolimnion of East Lake Bonney has the greatest B concentration of ~4.1 mM. In MCM, the source of B is from ancient seawater input and the dissolution of aerosol dust or chemical weathering of the stream channel materials. In Saskatchewan, Little Manitou has a B concentration 30X higher than other lakes in this region. This lake is fed only by groundwater. In a comparison of Na/Cl to B/Cl ratios across all systems, different geochemical evolutionary pathways are evident in these saline lakes. Great Basin lakes, with the high B concentrations, show the greatest enrichment in both B and Na. Relative to seawater ratios, MCM lakes’ variations display a large heterogeneity with some lakes being depleted in B and Na relative to Cl and others enriched in B and Na relative to Cl. Saskatchewan lakes are similar in B and Cl concentrations to the hypersaline bottom waters of East Lake Bonney, but with depletion in Na relative to Cl. Comparisons will made between our data, Australian salt lakes, Lake Van, Turkey; the Great Salt Lake, USA; and the Dead Sea for a broader, world perspective of boron geochemistry in terrestrial saline systems.