Contaminant dilution measure for the solute transport in an estuary

Abstract

Abstract The pollution pressures on coastal waters predominantly come from the river freshwater transport and loadings of contaminants into the estuary. This study presents the probabilistic model of the near field solute transport in an estuary based on the spatially integrated concentration statistics. A methodology is presented for quantifying the degree of dilution within the surface layer in terms of expected mass and volume fraction functions as a simple alternative to the point concentration probability density function. The theoretical prediction is experimentally validated using the salinity dilution as an inverse process in the field case of river Žrnovnica near the city of Split. A novel dilution measure is presented as combination of expected mass and volume fraction indicating the area of an estuary where dilution process will attenuate the concentration of a passive contaminant below any selected environmental limits. Introduced dilution measure directly corresponds to different catchment loadings through the river as a hydrological pathway of mass transport and can be used for assessing water quality status for transitional water bodies and to guide future efforts for monitoring potential eutrophication hot-spots in the coastal area.