In this study, concentrations of heavy metals and anions of natural origin were investigated using boring core obtained from the north bank of the Shin-yodogawa River in the northern part of Osaka City. A leaching test and a content test in compliance with Soil Contamination Countermeasures Law in Japan were applied. The leaching test is a method by which soil in ten times its volume of water is shaken for 6 hours, and considers the risk of ingestion of groundwater contaminated by hazardous substances eluted from contaminated soil. The content test is the method of eluting hazardous substances from 6 g of soil by shaking the sample in 200 mL of 1 mol/L hydrochloric acid for 2 hours, and considers the risk of the direct ingestion of contaminated soil. Concentrations of heavy metals obtained by the content test were lower than stipulated in the Japanese regulations, while some samples showed higher concentrations than stipulated in the regulations when using the leaching test.
Metal concentrations were also observed by a microwave extraction method (MEM), which approached those of the total content analysis. The relationships between ratios of leaching amounts to the concentrations obtained by MEM and solution pH were used to discuss leaching characteristics. Because there were good correlations among concentrations of heavy metals and anions obtained by the leaching test, boron concentration could also be estimated from Cl- concentration, and F- concentration could be estimated from both concentrations of SO42- and Ca. There is a possibility that total amounts of Pb and Cr of natural origin in soil could be estimated using relationships with total amounts of other metals such as Ni, V, Mn, Zn and Mg, because their concentrations obtained by MEM showed good correlations.
