ABSTRACT
We address here another, yet related, issue concerning the subsurface environment that has been largely ignored in urban settings: material (contaminant) transport to surface waters. Research over the last few years has shown that Submarine Groundwater Discharge (SGD) to the coastal zone is a significant water and material pathway from land to sea (e.g., Bokuniewicz, 1980; Moore, 1996; Taniguchi
et al., 2002). This flow may occur through the surficial aquifer or through breaches in deeper semi-confined coastal aquifers. While the overall flow of fresh groundwater into the ocean is likely no more than about 6% of global runoff, it has been estimated that the total dissolved salt contributed by terrestrially-derived SGD may be as much as 50% of that contributed by rivers (Zektser and Loaiciga, 1993). This process will thus affect the biogeochemistry of estuaries and the coastal ocean through the addition of nutrients, metals, and carbon (Moore, 1999). High dissolved N:P ratios in contaminated coastal groundwater relative to surface waters may drive the coastal ocean towards P-limitation within the coming decades, perhaps changing the present N-limited coastal primary production (Slomp and Van Cappellen, 2004; Hwang et al., 2005). In addition to inputs of terrestriallyderived groundwaters, recirculation of seawater through sediments by tidal pumping and other processes can provide significant biogeochemical inputs and is also considered “SGD” (Burnett et al., 2003).
