Estimating particulate dispersiveness and accumulation at nearshore ocean dumpsites

The characteristics controlling the dispersion and accumulation of ocean-dumped sewage sludge are analysed for eight sites in the United Kingdom, Europe, and the United States. Based on the assumption that the sludge consists of a rain of fine materials descending on a sandy substrate, annual dispersiveness from both the local dumpsite and the dumpsite region is calculated as a fraction of sludge solids dumped during a given year. Using actual dumping amounts, indices of local and regional sludge accumulation are then calculated. The local index ranges from less than 1 for slightly impacted sites to 35 for the most severely impacted location. The regional index is less than 1 in all but one case. The index appears to be useful as a predictive tool for assessing impact from a given dumping scenario.