Pollutant dispersion in shallow coastal water

Abstract

Expanding industrial development and the growing demand for energy coupled with the need to insure protection of our natural environment has made it necessary to develop modeling techniques to predict the fate of pollutants discharged to our natural waters. A primary problem in developing mathematical models is the establishment of the important input parameters which are dependent upon physical ambient characteristics. One of the most difficult parameters to establish in the so called far-field modeling is the values for eddy diffusion coefficients. This paper is primarily concerned with discussing physical field monitoring techniques and the associated analysis required to establish both horizontal and vertical eddy diffusion coefficients for shallow coastal waters. Data obtained in several areas along the north-east Atlantic coast are used to develop diffusion coefficients. The results include analysis of dye tracer, drogue and continuous time aeries current measurement obtained concurrently with other physical oceanographic data. The lateral eddy diffusion coefficients based on the continuous dye data lie in the range of 10^{2} cm2/sec to 10^{5} cm2/sec. The horizontal eddy diffusion coefficients based on the drogue data indicates the same increasing trend from 10 cm2/sec to 10^{4} cm2/sec over a three hour measurement period. The estimated eddy diffusion coefficients from the moored current meter data are within the range from 10^{5} cm2/sec to 10^{7} cm2/sec. The alongshore component of eddy diffusion coefficient from the current meter data is one order higher than the corresponding offshore component due to large scale fluctuations in the alongshore direction. The current circulation pattern in the near-shore region is generally characterized by the combination of rotary tidal currents, predominant alongshore current, and variable currents influenced by local wind and large scale flow system. Monte Carlo simulation of pollutant dispersion with characteristic values are shown as an example.