Axens buys activated alumina business from Rio Tinto Alcan

Abstract

The south and east coastal currents of Lake Ontario were investigated to determine if they serve as the major source of the common odour compounds, 2-methylisoborneol (MIB) and geosmin (GM), to the St. Lawrence River (SLR). MIB and GM at low parts per trillion levels produce earthy-musty off-tastes in drinking waters. Previous investigations in 1996 and 1997 identified the presence of GM and MIB in SLR and in the southern coastal jet of Lake Ontario, which contributes the bulk of the summertime flow to the St. Lawrence River. Water samples were collected in July and September 1998 during cruises of Lake Ontario and the SLR, extracted shipboard and analyzed for MIB and GM. In July, both compounds were detected only in the SLR, but were found in both Lake Ontario and SLR stations in September. However, MIB and GM were found at higher levels in the St. Lawrence River (17 to 60 ng/L and 2 to 18 ng/L, respectively) than in samples from the Lake Ontario coastal current (0.5 to 10 ng/L and < 2 ng/L, respectively). The concentration profile of these samples from lake to river shows maximum concentrations of both MIB and GM in the St. Lawrence River near Brockville, Ontario. The data indicate sources of MIB and GM are primarily within the river (as opposed to sources from Lake Ontario). Zebra mussel infestation of the upper St. Lawrence River is particularly prevalent in the Brockville section of the St. Lawrence and they are implicated together with other benthic sources in the production of MIB and GM in the river.