The effect of the dumping of waste-acid from the titanium-dioxide production on the chlorophyl-a concentration of North Sea water: A time series analysis.

Since 1963 the waste-acid of the German titanium dioxide industry is discharged off the Dutch coast. From March 1980 on the dumping takes place in an area situated 40-80 km from the coast. Although about 2 500 000 kg waste-acid is discharged every day, until now no effects could be found on the plankton.This paper describes the study on the effects of the dumping on the chlorophyl-a concentration of the seawater at a site north of the dumping area, with the help of time series analysis. It is shown that considerable changes in the chlorophyl concentration occur during the dumping period and that these changes coincide with certain events within the dumping history. However, it is most remarkable that the starting of the dumping itself does not show an effect on the chlorophyl concentrations. Explanations are suggested, but could not be investigated yet.This study shows also that collecting data without a proper statistical design make it impossible to draw unambiguous conclusions based on those data.