Desorptive behavior of phosphate in the subtropical Miyara River, Ishigaki Island, Japan.

The desorption of phosphate-phosphorus (PO4) from riverine particles with a salinity increase in Miyara River water, Ishigaki Island, Japan, was examined in laboratory experiments involving mixing of unfiltered riverine water with coastal seawater filtered through a 0.4-μm Nuclepore filter and the addition of sodium chloride (NaCl) into unfiltered riverine water. The mixing experiment yielded a convex pattern in the dissolved PO4–salinity plot, and the dissolved riverine PO4 concentration increased with the NaCl addition. These results suggested PO4 desorption from riverine particles with a salinity increase. The pattern of desorption could vary according to the sample conditions, such as the concentrations of dissolved PO4 and suspended solids. However, the obtained results seemed to simulate the convex distribution pattern in the dissolved PO4–salinity plot observed at the mouth of the Miyara River in general. [ABSTRACT FROM AUTHOR]