汚濁感潮河川における底泥の巻き上げと懸濁態リン・重金属元素の挙動

Abstract

Concentrations of phosphorus and heavy metals in water and suspended matter (SM) were examined in a polluted tidal river during tidal sediment transportation.The increases in concentrations of phosphorus and heavy metals in the Shonai River water following sediment transportation were attributed mainly to increases of phosphorus and metals in particulate form. Among various forms of phosphorus and heavy metals in SM, hydroxylamine-acetic acid (HA) soluble phosphorus and metals and hydrogen peroxide (HO) soluble phosphorus, whose concentrations in SM varied with the organic contents, were thought to be easily movable. Relationships among parameters suggested that the phosphorus and metals were mainly attached or adsorbed onto organic matter (HO soluble phosphorus, HA soluble zinc, copper, and lead), or adsorbed on iron hydroxide (HA soluble phosphorus). Their concentrations in SM decreased when sediment transportation was frequent, and were higher after the long meteorologically stable days compared to just after a storm. Thus, it was suggested that the movable phosphorus and heavy metals were lost partially from SM during the stage in which they scaled onto the bottom, but during meteorologically stable days, were more liable to be accumulated in bottom sediments owing to the fact that supply was greater than loss. Because of the considerable reduction to soluble form, manganese did not accumulate in SM or bottom sediments in the semireductive environment under study.