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The occurrence of twelve chlorinated and brominated volatile compounds was investigated by a HRGC (High Resolution Gas Chromatography) device with a dynamic purge (PTI, Chrompack) in the water of the river Seine under dry conditions and under contrasting hydrological regimes, according to three longitudinal profiles from upstream to downstream of the Paris urban centre. Our results showed an obvious rise of the solvent concentrations in the river Seine water along the profiles. The total chlorinated solvent concentration, which was below 1 μg L$^-1$ upstream of Paris, reached a maximum value of 8 μg L$^-1$ dowstream of the urban centre in December 1994. This corresponded to a flux of around 300 kg d$^-1$. This contamination originated in successive waste inputs, both domestic and industrial, from the Paris main sewers. The losses by evaporation from the river were taken into account for the estimation of the waste. The waste inputs represented about 85 to 97% of the total chlorinated solvent flux observed downstream of Paris. During the two first sampling sessions, dichloromethane represented 67% of the inputs. Though the hydrological regime plays a part both in the waste dilution and in the losses by evaporation processes, other factors such as the industrial activities or the ambient temperature may have a major influence upon the river contamination. [ABSTRACT FROM AUTHOR]