Retention and Long Term Accumulation of EOCl from Pulp Mill Effluents in a Baltic Sea Recipient

The total inventory and distribution of ExtractableOrganic Chlorine (EOCl) has been investigated in anestuary exposed to pulp mill effluents for over 50 yr.The estuarine turnover of suspended particulate matter(SPM) and associated pollutants was studied using a modeldescribing important processes for EOCl accumulation. Therecipient has a low retention of SPM due to dominatingstratified conditions in the water column. The totalinventory of EOCl in the sediment is therefore relativelylow as compared with the total discharge. It was foundthat the vertical distribution of EOCl has a closerelationship to the extent of chlorine use at the mill.Discharges of SPM from the pulp production process play amajor role in establishing the chronology of the sediment.A modernisation of the mill from 1986 to 1991 considerablyreduced the discharges of chlorinated substances. In the near future there will be an accumulation of EOCl in the estuary.