Organic matter transport and degradation in the river Seine (France) aftera combined sewer overflow

The impact of a combined sewer overflow (CSO) upon receiving waters has bee n studied in the river Seine during Summers 1995 and 1996. Three main event s have been monitored with special attention paid to the computation of oxy gen, carbon and suspended solids budgets. Bacterial biomass and bacterial p roduction rates have been measured to provide a more accurate understanding of the carbon cycle of the river Seine. Oxygen consumption inside the poll uted water masses was totally due to the activity of large bacteria dischar ged into the river by the CSO, the activity of native small bacteria did no t significantly increase after CSOs. Suspended solids issued from the CSO v ery quickly settles in this deep, slowly flowing river. However, discharged dissolved organic carbon (DOC) cannot account for the observed oxygen depl etions, the additional carbon source could be phytoplankton or deflocculate d/degraded particulate organic matter. (C) 1988 Elsevier Science Ltd. All r ights reserved.