Hydrochemistry of urban groundwater in Seoul, South Korea: effects of land-use and pollutant recharge

The ionic and isotopic compositions (delta D, delta O-18, and H-3) of urban groundwaters have been monitored in Seoul to examine the water quality in relation to land-use. High tritium contents (6.1 - 12.0 TU) and the absence of spatial/seasonal change of O - H isotope data indicate that groundwaters are well mixed within aquifers with recently recharged waters of high contamination susceptibility. Statistical analyses show a spatial variation of major ions in relation to land-use type. The major ion concentrations tend to increase with anthropogenic contamination, due to the local pollutants recharge. The TDS concentration appears to be a useful contamination indicator, as it generally increases by the order of forested green zone ( average 151 mg/l), agricultural area, residential area, traffic area, and industrialized area ( average 585 mg/ l). With the increased anthropogenic contamination, the groundwater chemistry changes from a Ca - HCO3 type toward a Ca - Cl(+ NO3) type. The source and behavior of major ions are discussed and the hydrochemical backgrounds are proposed as the basis of a groundwater management plan.