Use of energy-dispersive x-ray microanalysis as a rapid method for demarcating areas around marine outfalls that may be influenced by effluent: a case study

Abstract

Surveys that monitor pollution in a marine environment often include the measurement of heavy metals and other trace elements in sediments obtained from multiple stations near marine outfalls. This study investigates the use of energy-dispersive x-ray (EDX) microanalysis as a rapid screening method, where characteristic or "signature" elements (SE) in effluent can be located and mapped on the seabed. Thereafter, sediments from stations/areas with high SE can be examined using more sensitive spectroscopic methods, and, if present, trace metals quantified. To serve as controls, 21 samples of sediment were obtained from two "pristine" areas off the Kwazulu Natal coast. A further 99 samples were obtained from stations within 2km of the Huntsman Tioxide pipeline. Each sample was sonicated to separate the course from fine fractions. The fines were collected on a paper filter and mounted next to its corresponding, washed, coarse fraction on a graphite stub. Each sample was coated with C and examined by EDX Huntsman Tioxide effluent was rich in Ti and Fe. The fine and coarse fractions of all sediments were screened for these elements. A contamination index (1) was constructed from the combined fines, Ti and Fe data. Surfer 16, software was employed to create contour plots showing the distribution of Ti, Fe, and I in fine and Ti in coarse fractions of sediments near the Huntsman Tioxide pipeline. The results showed that EDX was an effective method for locating fallout "hot spots" and delimiting an area affected by effluent.