[Outflows of trihalomethane precursors from soils]

Outflows of trihalomethane formation potential (THMFPs) which was chosen as an index of the amount and reactivity with chlorine of THMs precursors from soils were studied with soil column experiment. The results indicated that factors influencing THMFP concentrations of leacheates were the physicochemical properties of soils, especially contents, composition and reactivities with chlorine of humic substances, the pH value of feed solution and cumulative leaching volume. The THMFP concentrations of leachates rose with increases in amounts of humic substances with high solubility as well as reactivity with chlorine. The effluents of soil samples contained the lowest THMFP concentrations under the feed solution of the lowest pH value (pH 3.0). THMFPs appeared to more easily flow out from soils with the feed solution of lower pH value, which was properly due to the increases in solubility of humic substances under the lower pH value conditions. In most cases, THMFP concentrations of leachates showed decline with the increase of cumulative leaching volumes of feed solution.