Abstract-The occurrence, sources, and fate of trichloroacetic acid (TCA) has been investigated in surface waters, ground waters, drinking waters, wastewaters, and rainwater in Switzerland. The concentrations found in surface waters varied between less than 27 ng/L (limit of quantification) and 340 ng/L, whereas the concentrations in ground water were always below 27 ng/L. It was found that the main sources of TCA in surface waters were the effluents of wastewater treatment plants (average concentration, 430 ng/L; range, 40-1060 ng/L). The average TCA concentration in rainwater was 300 ng/L range, (Ͻ27-900 ng/L). A dynamic mathematical model revealed that TCA is not significantly degraded in a lake (half-life Ͼ230 d). A detailed mass balance in the catchment area of a small lake (Greifensee) and a very rough mass balance over Switzerland indicate that rain is the major source of TCA in Switzerland (Ͼ90%), but they also show that about 60 to 80% of the TCA deposited by rain is eliminated, most probably in the soil.

The occurrence, sources, and fate of trichloroacetic acid (TCA) has been investigated in surface waters, ground waters, drinking waters, wastewaters, and rainwater in Switzerland. The concentrations found in surface waters varied between less than 27 ng/L (limit of quantification) and 340 ng/L, whereas the concentrations in ground water were always below 27 ng/L. It was found that the main sources of TCA in surface waters were the effluents of wastewater treatment plants (average concentration, 430 ng/L; range, 40-1060 ng/L). The average TCA concentration in rainwater was 300 ng/L range, (Ͻ27-900 ng/L). A dynamic mathematical model revealed that TCA is not significantly degraded in a lake (half-life Ͼ230 d). A detailed mass balance in the catchment area of a small lake (Greifensee) and a very rough mass balance over Switzerland indicate that rain is the major source of TCA in Switzerland (Ͼ90%), but they also show that about 60 to 80% of the TCA deposited by rain is eliminated, most probably in the soil.

A case study was carried out at an old landfill site (Riet site) located in Winterthur, northern Switzerland. The Riet site contains mainly municipal solid wastes (MSW) comprising four discrete unlined landfill compartments, the oldest of which dates back to 1918. One goal of the case study was to assess the investigative techniques used to determine the risk of groundwater contamination. Waste compartments and leachate plumes were delineated with the electromagnetic method EM31 and with tracer methods. The most efficient methods for a risk assessment were flow modelling based on reliable hydraulic head and hydraulic conductivity measurements, and chemical analyses. Chemical analyses of leachate and groundwater samples showed that the older compartments of the landfill pose only a small risk to the groundwater. The other goal of the study was to determine the long-term risk of groundwater contamination posed by MSW landfills of different ages. To this end, chemical concentrations of leachate from the Riet site were compared with those of other MSW landfills of various ages. The longterm risk of landfill compartments older than about 1960 can be considered in general to be considerably smaller than that of younger ones. Age of the compartment and leachate concentrations could be correlated.

A case study was carried out at an old land®ll site (Riet site) located in Winterthur, northern Switzerland. The Riet site contains mainly municipal solid wastes (MSW) comprising four discrete unlined land®ll compartments, the oldest of which dates back to 1918. One goal of the case study was to assess the investigative techniques used to determine the risk of groundwater contamination. Waste compartments and leachate plumes were delineated with the electromagnetic method EM31 and with tracer methods. The most ef®cient methods for a risk assessment were¯ow modelling based on reliable hydraulic head and hydraulic conductivity measurements, and chemical analyses. Chemical analyses of leachate and groundwater samples showed that the older compartments of the land®ll pose only a small risk to the groundwater. The other goal of the study was to determine the long-term risk of groundwater contamination posed by MSW land®lls of different ages. To this end, chemical concentrations of leachate from the Riet site were compared with those of other MSW land®lls of various ages. The longterm risk of land®ll compartments older than about 1960 can be considered in general to be considerably smaller than that of younger ones. Age of the compartment and leachate concentrations could be correlated.

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