IDENTIFICATION OF DIFFUSE AND POINT SOURCES OF DISSOLVED ORGANIC-CARBON (DOC) IN A SMALL STREAM (ALB, SOUTHWEST GERMANY), USING GEL-FILTRATION CHROMATOGRAPHY WITH HIGH-SENSITIVITY DOC-DETECTION

Using gel filtration chromatography and high-sensitivity UV and organi c carbon (OC) detection, the quality and quantity of organic matter in a stream (the Alb, Southern Germany) has been studied in the winter s eason. In the catchment area and upstream of two sewage plant effluent s the organic load has been low (below 1 mg/l TOC) and has been domina ted by humic substances (more than 80%). Downstream of the sewage plan ts, TOC increased up to 5 mg/l while humic constituents decreased down to 30%. A detailed analysis showed that in the catchment area the hum ic fraction has been composed of fulvic acids with relatively high amo unts of aliphatic structures. Downstream of the sewage plants, the hum ic fraction has been composed of fulvic acid precursors with associate d non-humic matter. It is concluded that the quality and quantity of o rganic constituents in the stream has been dominated by the secondary effluents.