Fractional distributions of major-to-ultratrace elements in coastal seawater and their partitionings in laboratory-made salts as investigated by inductively coupled plasma atomic emission spectrometry and inductively coupledplasma mass spectrometry with aid of membrane- and ultra-filtration techniques

The coastal seawater sample was filtered with a membrane filter (pore size 0.45 mu m), and the filtrate was further filtered with an ultrafiltration f ilter (molecular weight permeation limit of 10000 Da). Then, major-to-ultra trace elements in the particles which remained on the membrane filter, the membrane-filtered seawater, and the ultrafiltered seawater were determined by ICP-AES (inductively coupled plasma atomic emission spectrometry) and IC P-MS (inductively coupled plasma mass spectrometry). From these analytical results, the fractional distributions of each element in the particle, larg e molecule and small molecule fractions of seawater were estimated, where t he distributions of the elements in the large molecule fraction were obtain ed as the differences between the elemental concentrations in membrane-filt ered and ultrafiltered seawaters. Furthermore, laboratory-made salts (Salts I-III) were prepared from origina l, membrane-filtered, and ultrafiltered seawaters. The concentrations of ma jor-to-ultratrace elements in laboratory-made salts were also determined by ICP-AES and ICP-MS. It was found that alkali metals, alkaline earth metals , oxoanion-forming elements (V, Mo, W, U) and Cd were mostly contained in t he small molecule fraction of seawater, and ca. 95-100% of them in salt, ex cept for V, originated from those in the small molecule fraction. More than 50% of Al, Mn, Fe, Co, Ga, Y, rare earth elements (REEs) and Pb were conta ined as the particle constituents in seawater, but their intakes into salt were less than 50%. In addition, the fractional distributions of the follow ing elements in the large molecule fraction of seawater were: Al 10%, Mn 4% , Fe 2%, Cu 23%, Zn 7%, Y 5%, REEs 3-15%, and Pb 30%. On the other hand, th e intake factors of these elements in salt from the large molecule fraction were: Al 40%, Mn 5%, Fe 28%, Cu 20%, Zn 30%, Y 7%, REEs 5-30%, and Pb 55%. The results obtained in the present experiment suggest that the distributi ons of the elements in natural salt greatly depend on the chemical forms in seawater.