Use of Water Quality Analysis for Groundwater Traceability

Abstract

Water contains various elements with different concentrations. The quality of terrestrial water varies spatially and temporally in accordance with the amount and quality of precipitation, geology, and artificial materials in the watershed. The overall characteristics of water quality are visualized as a hexadiagram, which is expressed by the concentration and proportion of the major cations and anions. Water quality of groundwater displays geographic variation in a basin, which is a function of the dissolution and precipitation of minerals, sorption–desorption at mineral surfaces, ion exchange with clays, and oxidation–reduction reactions in the aquifer. Stable isotopes of hydrogen and oxygen in groundwater are useful to identify the recharging area, whereas those of sulfate and nitrate are useful to evaluate the degree of oxidation–reduction resulting from bacterial activity. The strontium isotope ratio is known to be a powerful hydrogeological tracer, because the geochemical behavior of Sr is similar to that of Ca, which is the dominant cation derived from rocks. The geochemical and isotopic composition of water and its various constituents can be used as traceability data that reproduce the natural environment and human activities encountered along the path of groundwater.