Effects of Organic Matter on Acceleration of the Iron Elution Rate from Steelmaking Slag

An iron (Fe) fertilization method using a mixture of steelmaking slag and compost for restoring seaweed beds in coastal areas of barren grounds has been developed, and mixing of organic matter other than compost with steelmaking slag has been shown to accelerate the Fe elution rate. In this study, Fe elution tests under conditions close to that of the actual sea environment were conducted in Tsushima, Nagasaki Prefecture, Japan, to elucidate the effects of the addition of powdered bamboo on the promotion of Fe elution. We examined the characteristics of Fe elution for three samples: 1) the mixture of steelmaking slag and compost; 2) the mixture of slag and powdered bamboo; and 3) the mixture of slag, compost, and bamboo. Our results showed that addition of bamboo to the mixture of slag and compost was the most effective for accelerating the Fe elution rate, suggesting that the amount of eluted organic matter was important, as were the structural characteristic of the material. The safety of this method was also evaluated by investigating the accumulation of heavy metals in sea creatures. We confirmed that six heavy metals, i.e., cadmium, arsenic, lead, zinc, selenium, and chromium, were not accumulated in the sea cucumber and sea snails.