The Well Water Contamination by Mn Related to the Road Pavement Works

Chemical Properties of the Slag

Abstract

In the road pavement works at Yame in Fukuoka prefecture in 1975, the well water along the work area were suddenly contaminated by Mn.
Since there were no obvious sources of Mn, the origin of Mn and the cause of Mn elution were studied with respect to the interaction between the soil and the road construction materials.
It was found that Mn was eluted neither from the road construction materials nor from the soil alone. However, Mn was eluted out from the soil when it was treated with the water contacted with the slag. The following results were found in relation to the mechanism of Mn elution.
(1) When the slag was extracted with water a considerable amounts of Ca²⁺, Na⁺, K⁺ and S^2-_ were eluted out.
(2) A model “slag-water” prepared by dissolving an appropriate salt of Ca²⁺, Mg²⁺, Na⁺ or S^2- in distilled water showed a remarkable ability to elute Mn from the soil.
(3) The slag used in the pavement works was the “fresh” one that was obtained just after production.
The “fresh” slag gave much more amounts of those ions mentioned in (1) than the “aged” slag. It was concluded that the Mn elution in the road pavement works involved the following sequence of events : elution of Ca²⁺, Na⁺, K⁺ and S^2- from the slag, reduction of Mn³⁺ to Mn²⁺ in the soil, and the elution of Mn²⁺ into solution through ion-exchange with Ca²⁺, Na⁺ and K⁺.