DISSOLVED ORGANIC-MATTER QUANTITY AND QUALITY FROM FRESH-WATER AND SALTWATER LAKES IN EAST-CENTRAL ALBERTA

Concentrations of dissolved organic matter (DOM) in surface waters of sub-humid to semi-arid lakes in east-central Alberta increase with increasing salinity and water residence time from about 20 to 330 mg L(-1) as dissolved organic carbon (DOG). This pattern is opposite to that observed among freshwater lakes spanning a gradient in water residence times, and is probably caused by evaporative concentration of refractory DOM. The proportion of total DOG, operationally defined as humic substances using XAD-8 resin, was high, though similar to surface waters typically referred to as ''humic'', and independent of salinity: Very long water residence times (hundreds of years) in saline lakes favors evapoconcentration of low-color, low molecular weight DOM, with N-content characteristic of allochthonous DOM.