OPTIMAL COST-EFFECTIVE SAMPLING FOR MONITORING AND DREDGING OF CONTAMINATED SEDIMENTS

We used spatial statistics to study variability within contaminated se diments of three zones in Lake Ketelmeer in the Netherlands. Attention focused on the copper (Cu) and benzo(A)pyrene (BAP) content of the co ntaminated layer, its thickness, and related clay and organic matter ( OM) contents. Optimal sampling distances for monitoring aquatic pollut ants and the thickness of the contaminated layer in the sediments were estimated taking spatial variability into account. These distances de pend on water depth, sedimentation, erosion, shipping activities, and types of sediment. In 40% of the study area, the thickness of the cont aminated layer can be surveyed at a grid spacing that is 18 times as w ide as that needed in harbors, near shores, and shipping routes to ach ieve the same accuracy. A new optimizing and cost-effective method for accurate aquatic monitoring is suggested as a preliminary step to the removal of contaminants in the future.