ABSTRACT

This observation was carried out on the surface seawater of Jinhae Bay, southeastern Korea during a red tide in July, 1991 in order to understand the removal processes of reactive trace elements using natural radionuclides of ²³⁴Th and ²¹⁰Po as co-tracers. Comparing the results of ²³⁴Th and ²¹⁰Po activities against chlorophyll a and TSM (total suspended matter), the two nuclides have different scavenging process in the surface coastal seawater during algal blooming. Particulate and dissolved ²³⁴Th and particulate ²¹⁰Po are subject to dilution by chlorophyll a and TSM, showing the negative correlation with ²³⁴Th and particulate ²¹⁰Po, while they are positively correlated with dissolved ²¹⁰Po. This suggests that scavenged ²¹⁰Po may be preferentially re-dissolved at the bottom waters and/or surface sediments and reappear at the surface by tidal current. The calculated distribution coefficients (K_d) of ²¹⁰Po to particle (TSM) relative to that of ²³⁴Th was relatively large, demonstrating that the affinity of ²¹⁰Po to TSM is greater than that of ²³⁴Th during algal blooming. These results suggest that particulate matter, especially biogenic matter, plays a significant role in controlling the scavenging of reactive trace metals in coastal seawater.