Reexamination of the fractionation of total dissolved phosphorus in seawater using a modified UV-irradiation procedure, and its application to samples from Suruga Bay and Antarctic

• Main Authors: Katsumi Yanagi, Masayoshi Yasuda, Fukashi Fukui
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 1992
• Subjects: Antarctic; Antarctic Ocean; Riley; Antarc*
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.464.9609; http://www.terrapub.co.jp/journals/JO/pdf/4803/48030267.pdf

Application of a modified UV-irradiation procedure to the fractionation of total dissolved phosphorus (TDP) in seawater was examined. By using a peristaltic pump, a sample solution was passed through a quartz column which was coiled around the three Hg-lamps and thus consistently exposed to a controlled UV-irradiation flux. The UV-flux was much lower than that historically employed to hydrolyze total dissolved organic phosphorus (DOP). Before and after the UV-irradiation, colorimetric measurements of soluble reactive phosphorus (SRP) were made by the method of Murphy and Riley (1962) to determine the liberation rate of orthophosphate from P-compounds in the sample. Experiments using 19 different P-compounds indicated that organic phosphate-esters containing only monomers of phosphate were readily decomposed by a 20-minute UV-irradiation period. Release of SRP from organic polyphosphates was minimal. The P released by this procedure is operationally referred to as “UV-P”. The procedure described herein was employed for fractionation of TDP in seawater. These studies defined several classes of dissolved P: (1) PO4–P (inorganic phosphate-P), (2) UV-P (Photo-decomposable organic-P, most of which consists of organic monophosphate-P), and (3) Org-Poly-P (organic polyphosphate-P). Vertical profiles of DOP and UV-P observed in the oligotrophic regions of Suruga Bay and Antarctic Ocean indicated that UV-P was a major part of total dissolved phosphorus (TDP) in euphotic layers, where inorganic nutrients were probably limiting the active growth of phytoplankton. It is probable that UV-P can be utilized as a source of nutrient-P, in place of PO4–P.