Abstract

Coastal acid sulfate soils are naturally generated sediments, mainly containing iron sulfides. This study investigated the natural distribution of acid sulfate soils at the mouth of a river, and their remediation ability of persistent organic chemicals. These soils were distributed on a small scale in southern Japan; Iriomote Island was used as the study site. Coastal acid sulfate soils were found to be restricted to the surface in the downstream portions but distribution depth increased upstream. The shallow, surficial portion of acid sulfate soils in upstream areas had already oxidized and leached sulfuric acid. The degradation ability of sampled acid sulfate soils for dieldrin was confirmed in laboratory experiments and the degradation ability was found to increase with iron sulfide content. These reactions were controlled by the chemical reactivity of iron sulfides in natural systems but independent of microbial activity.