Behavior of dissolved cadmium in surface water of Urasoko Bay, Ishigaki Island, Japan

Abstract

The concentrations of dissolved cadmium (Cd) were monitored in the surface water of Urasoko Bay and the mouth of the stream that runs into the bay. Urasoko Bay is located on the northern coast of Ishigaki Island, Okinawa, which is surrounded by a fringing reef. Water samplings were carried out from August 2006 to August 2007, and adding to these samplings, freshwater from the upper stream and brackish water that exudates at the beach site were collected from April to June 2007. The concentration of dissolved Cd showed no tendency to decrease from the upper stream to the bay site. The results of Cd behaved non-conservatively in the Cd-salinity plot, which was attributed to daily variations in the Cd concentrations of upper stream water and the irregular input of Cd possibly adsorbed particles into the stream and beach water (the mixture of groundwater and seawater before exudation on the beach).