Estimation of Boron Contamination Sources of Groundwater in the Central Boso Peninsula, Chiba Prefecture, Japan.

Abstract

The purposes of this study are (1) to describe the extent of boron contamination of groundwater in the Central Boso Peninsula and (2) to identify possible sources of the contamination. Out of 147 samples, boron concentrations of 21 samples exceeded the former guideline value of 0.2 mg/L. The contaminated wells are distributed locally. The groundwater with high boron concentrations has characteristics of higher values of Na, K, and HCO₃ concentrations, pH and EC, extremely lower value of Ca concentration and brownish colored water. The contaminated water is classified into two types of water, noncarbonate alkali and carbonate alkali types, whose contaminant sources are estimated as fossil water and marine sediments of deep layers, respectively.