Assessment and modeling of dispersal contamination incoming with submarine groundwater discharge (SGD) in tsunami affected coastal areas

Abstract

The submarine groundwater discharge (SGD) transports a significant amount of various contaminants into the coastal zone especially in tsunami affected areas. An assessment of the impact of intruded pollutants in the coastal ecosystems requires understanding the fate of the pollutants and processes of their dispersal in ambient waters. In this paper, we proposed a methodology for SGD data collection and data assessment, using different methods, technology, techniques and instruments as well as the 3-D coupled ocean circulation/particle-tracking model for assessment and predicting the transport and dispersal of pollution-containing SGD into a coastal environment. Among the proposed methods to use for data collection and the SGD assessment primary attention was paid to geophysical, hydrologic, remote sensing and hydro-geologic measurements, using natural radiotracers, measurements by seepage meters and benthic chambers, biogeochemical and biological measurements. Also, several new modeling approaches were considered in particular those which use the particle-tracking model. The particle-tracking model takes currents and turbulent diffusivities predetermined by the ocean circulation model and uses the Lagrangian approach to predict the motion of individual droplets, the sum of which constitutes a contaminant plume which is the result of discharge of contaminant-rich submarine groundwater. Presently, we limited our simulations to elucidate the effect of tides on the SGD/nitrate plume formation. The model predicts behaviour of a nitrate plume, its shape and variation during a tidal cycle in the shallow waters. The model can be used to predict contamination of coastal waters with various pollutants incoming with SGD in the aftermath of a tsunami when impact of the latter on aquifers can be significant.