Remediation of muddy tidal flat sediments using hot air-dried crushed oyster shells

In order to prove that hot air-dried crushed oyster shells (HACOS) are effective in reducing hydrogen sulfide in muddy tidal flat sediments and increasing the biomass, field experiments were carried out. The concentration of hydrogen sulfide in the interstitial water, which was 16 mg S L−1 before the application of HACOS, decreased sharply and maintained almost zero in the experimental sites (HACOS application sites) for one year, whereas it was remained at ca. 5 mg S L−1 in the control sites. The number of macrobenthos individuals increased to 2–4.5 times higher than that in the control site. Using a simple numerical model, the effective periods for suppression of hydrogen sulfide were estimated to be 3.2–7.6 and 6.4–15.2 years for the experimental sites with 4 and 8 tons per 10 × 10 × 0.2 m area, respectively. From these results, it is concluded that HACOS is an effective material to remediate muddy tidal flats.