THE MIXING BEHAVIOR OF TRACE METALS AND NUTRIENTS IN THE FRESH SPRING WATER ESTUARY OF JEJU, KOREA

Abstract:

Unlike the riverine estuary, the fresh groundwater estuary has rarely been studied, even though recent studies report that the amount of fresh water fluxes from groundwater could rival the riverine inputs to the world oceans. I hypothesized that the mixing behaviour of chemical constituents between fresh groundwater and seawater water quite different from that in typical river estuary. Here, we investigated the groundwater-borne major- (Nitrate, Phosphate, and Silicate)/micro nutrients (trace metals) in the two coastal mixing zones (Hwasun Bay and Gwakji Beach) in Jeju Island, Korea, where the large amount of fresh groundwater occurred. The trace metals showed 3 different mixing patterns, i) Sink type (decrease during mixing), ii) Source type (increase during mixing), and iii) No clear trend type. Interestingly, V and Cd showed conservative mixing trends whereas other trace metals showed non-conservative mixing. All the major nutrients (DIN, DIP, DSi, and TDN) showed conservative mixing trends and decreased with increasing salinity, while the DOC (dissolved organic carbon) increased with increasing salinity. These results indicated that fresh groundwater estuaries showed the different behavior from the riverine estuary. Moreover, the fresh groundwater estuaries might be more important the budgets of terrestrial chemical constituents since the riverine estuary played a role as a sink of most trace metal and nutrients.