AOX LEVELS IN THE RIVER RHINE - 50 PERCENT OF NATURAL ORIGIN

An AOX transport model is used to distinguish natural and anthropogeni c sources of organohalogen compounds in river basins. Application of t his model to AOX data of the river Rhine basin in the years 1986 to 19 91 shows a constant natural AOX contribution of about 15 mug.l-1 to th e total AOX flowing into The Netherlands. The anthropogenic discharge has decreased by 70-95% for the river Rhine basin in this six years re sulting in a situation that today 30-70% of the total AOX flowing into The Netherlands at Lobith originates from naturally produced organoha logen compounds.