Distribution of organochlorines between seawater and suspended solids
An analytical method was developed for the experimental investigations. This included sampling, separation into fractions, clean-up and determination of the organochlorines in suspended solids and seawater. A sampling apparatus was designed and built in our laboratory, capable of sampling seawater up to 28 l, and separating the suspended particles prior to the extraction of the filtered water with organic solvent. The analytical method for the determination of chlorinated biphenyls (CBs) and a large number of organochlorine pesticides in sediments was readily available in our laboratory. In addition, a method for the determination of pentachlorophenol (PCP) in seawater and solids was developed. The complete analytical method for the determination of particulate and dissolved organochlorines in the seawater column, at the ng l-1-pg l-1 level, was validated. Small scale experiments were not able to replicate the environment, therefore, a large scale experiment was undertaken in a Loch in the NW of Scotland. Experimental bags, 60,000 l capacity, were attached to a floatable frame and filled with seawater, then contaminated sewage sludge was dumped on it. A sampling strategy was designed, and a set of samples was obtained to investigate the factors affecting the partitioning, and the kinetics of the partitioning, between suspended solids and seawater. The experimental data from the analysis of the samples were used to propose a simple mathematical model describing the changes in the concentrations of particulate and dissolved organochlorines over the time of the experiment. The mathematical modelling provided values for the desorption rates and the partition coefficients of the nonequilibrium for the individual organochlorines. These calculated parameters were used to elucidate the possible trends related to physico-chemical properties of the organochlorines, and to propose the process affecting the organochlorine-particle interactions: intra-organic matter diffusion.