Po, Pb and Be partition coefficients on nanoparticles from laboratory experiments

<p>Improved applications of 210Po, 210Pb and 7Be as geochemical proxies require more detailed understanding<br />
of their interactions with particles. Here, laboratory sorption experiments were carried out to examine<br />
the adsorption of 210Po, 210Pb and 7Be and their fractionation on inorganic nanoparticles, including SiO2,<br />
CaCO3, Al2O3, TiO2 and Fe2O3, in the presence or absence of macromolecular organic compounds (MOCs)<br />
that include humic acids (HA), acid polysaccharides (APS) and proteins (BSA), in natural seawater. Results<br />
showed that nanoparticle sorption was not greatly enhanced over that of microparticles as would<br />
be expected from their much higher specific surface areas, likely indicating their aggregation in seawater.<br />
It was found that synergistic interactions between inorganic nanoparticles, MOCs, and radionuclides<br />
determined the sorption, although their adsorption was particle composition-dependent. MOCs enhanced<br />
the sorption of selected nuclides on most nanoparticles. On average, in the presence of MOCs, partition<br />
coefficients (Kc ) of 210Po, 210Pb, and 7Be on nanoparticles increased 2.9-, 5.0- and 5.9-fold, respectively.<br />
The effect of MOCs could be explained for 210Po and 210Pb from their different log Kc values on inorganic<br />
nanoparticles. In addition, fractionation effects between 210Po and 210Pb (or between 210Pb and 7Be)<br />
could be quantified from their relative log Kc values on end-member sorbent components. Applications<br />
of both 210Po–210Pb and 7Be–210Pb pairs as particle dynamics tracers could be more quantitative when<br />
the nature of the organic coatings is taken into account.</p>