| Resumo: |
An investigation was made to determine the influence of the dumping of a 1000 ton day<sup>-1</sup>, on the average, of acid-iron waste from the titanium dioxide industry into the shallow but turbulent Southern Bight of the North Sea. This waste contains some 20% sulphuric acid and 2% iron. After the passage of the barge that discharges 10 ton of waste min<sup>-1</sup> into its wake, the vertical and horizontal distributions of the pH, iron-concentrations and turbidity were measured as a function of time. It appeared that a few seconds after the discharge and for a very brief period, the pH was down to approx. 4 and the Fe-concentration was 13 mg l<sup>-1</sup>. More than 1 min after the discharge a pH below 6 and an iron-level above 3 mg l<sup>-1</sup> could not be detected anywhere. The measured factor for waste dilution by sea water, based on the observed acid and iron concentration in the waste and in the discharge track, were around 5,000 after 5 min, 9,000 after 10 min and 80,000 after 20 min. Before and long after the dumping, the total iron-concentration in this Southern Bight area was around 100 µg l<sup>-1</sup>, but this high level might be due to natural causes.
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