QUANTIFICATION OF GROUNDWATER-DERIVED NUTRIENTS INTO BEACH RIDGE DRAINAGE USING RADON MASS BALANCE MODEL

Abstract

Groundwater discharge can be a significant pathway for dissolved nutrients to surface water and thus can bring forth important implications to the coastal biogeochemical cycles. Discrete sampling of radon concentrations at several locations along an interridge drainage off Setiu Wetlands were carried out to estimate the fluxes of groundwater discharge. The Rn mass balance results show that groundwater discharge in the drainage is estimated to be 6649 mday, made up of ~33% of total water discharge and has contributed 2.88×10 molday, 1.23×10 molday and 0.75molday of ammonium-nitrogen, nitrate-nitrogen and nitrite-nitrogen, respectively into the surface water drainage. Strong correlation between radon and ammonium suggested that the source of nutrient in drainage is groundwater-based, derived probably from the nearby damaged or leaking residential septic tanks and from agricultural practices of oil palm plantation.