Abstract
Strong organic ligand in oceanic Particulate Matter (PM), as determined from amount of thorium adsorption onto PM in 0.1 M HCl, was measured for surface waters of mid-latitude region (ca. 32.5°S) in the South Pacific Ocean. The Particulate Organic Ligand (POL) concentrations in surface waters of the South Pacific, ranging from 2.6 to 13.3 nM, showed a longitudinal variation with low concentrations in the South Pacific subtropical gyre (180°-100°W) and high in the eastern South Pacific. The POL concentrations in the South Pacific surface waters increased with increasing nutrients (nitrate and phosphate) and chlorophyll concentration, which means that POL in surface waters is closely related to biological activity in the ocean; the high POL occurs in highly productivity region, whereas the low POL appears in the oligotrophic ocean. This is a first basin-scale measurement of POL in surface waters of the South Pacific. POL is a useful tool for better understanding of biological activity, particle dynamics and trace metal cycling in surface layer, if we have more detail knowledge on chemical and biogeochemical properties of POL, as do factors controlling spatial and temporal variability.
Highlights
Particulate Matter (PM), which consists of suspended and sinking particles, is one of the most important constituents in seawater because it is related to carbon export flux and cycling of trace elements in the ocean [1,2,3,4,5]
We have proposed that the concentration of Particulate Organic Ligand (POL), which is a peculiar functional group as a complexant defined by measuring the amount of thorium adsorbed onto PM in a 0.1 M solution of HCl [6], is an important factor for characterizing PM because the POL concentration is closely related to concentrations of particulate trace metals such as Fe, Cu, U, Th and Pu bound to PM [7,8,9,10,11]
The previous studies [8,9,12] revealed that the POL concentrations in surface waters of the western North Pacific, subarctic Pacific and the Japan Sea were in the ranges of 1.08 to 9.47, 9.9 to 13.5, and 10 to 21 nM, respectively
Summary
Particulate Matter (PM), which consists of suspended and sinking particles, is one of the most important constituents in seawater because it is related to carbon export flux and cycling of trace elements in the ocean [1,2,3,4,5]. To better understand production and fate of PM, and its biogeochemical roles such as trace metal-particle interactions, characterization of PM from different geochemical aspects is important; ex. We have proposed that the concentration of Particulate Organic Ligand (POL), which is a peculiar functional group as a complexant defined by measuring the amount of thorium adsorbed onto PM in a 0.1 M solution of HCl [6], is an important factor for characterizing PM because the POL concentration is closely related to concentrations of particulate trace metals such as Fe, Cu, U, Th and Pu bound to PM [7,8,9,10,11]. Measurements of the POL are acquired by filtration of small volumes of seawater, making these measurements advantageous from an experimental viewpoint [6]
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