7Be、 210Po和210Pb适合于研究周年及年际时间尺度内上层海洋颗粒物的循环与输出过程，是GEOTRACES计划（全球海洋元素及其同位素生物地球化学循环研究计划）重点关注的同位素。综合早期的研究发现，对海洋中210Po、210Pb和7Be与颗粒物之间的相互作用认识很少，难以回答“210Po、210Pb和7Be示踪的是颗粒物中何种组分”这一问题。
我实验室杨伟锋教授等人之前研究发现大分子有机化合物可能是调控颗粒物清除210Po、210Pb的关键组分，并提出了开阔大洋和近岸海域调控210Po、210Pb清除的关键颗粒物组分可能不同的观点（Yang et al., GCA, 2013）。近期，杨伟锋等人进一步研究了有机胶体粒子和无机胶体粒子与210Po、210Pb和7Be相互作用，发现蛋白质、腐殖酸、多糖使无机胶体粒子吸附210Po、210Pb和7Be的能力增强，并就颗粒物组分对210Po与210Pb的分馏作用以及对210Pb与7Be的分馏作用进行了初步量化，形成了胶体粒子与三种核素相互作用的框架性认知，为将来把分馏效应纳入这些同位素指标的地球化学模型奠定了基础。
本成果近期发表在地学一区期刊Earth and Planetary Science Letters上: Yang W., Guo L., Chuang C.-Y., Santschi P.H., Ayranov M., Schumann D. Influence of organic matter on the adsorption of 210Pb, 210Po and 7Be and their fractionation on nanoparticles in seawater. Earth and Planetary Science Letters, 2015, 423, 193-201.
Abstract:
Improved applications of 210Po, 210Pb and 7Be as geochemical proxies require more detailed understanding of their interactions with particles. Here, laboratory sorption experiments were carried out to examine the adsorption of 210Po, 210Pb and 7Be and their fractionation on inorganic nanoparticles, including SiO2, CaCO3, Al2O3, TiO2 and Fe2O3, in the presence or absence of macromolecular organic compounds (MOCs) that include humic acids (HA), acid polysaccharides (APS) and proteins (BSA), in natural seawater. Results showed that nanoparticle sorption was not greatly enhanced over that of microparticles as would be expected from their much higher specific surface areas, likely indicating their aggregation in seawater. It was found that synergistic interactions between inorganic nanoparticles, MOCs, and radionuclides determined the sorption, although their adsorption was particle composition-dependent. MOCs enhanced the sorption of selected nuclides on most nanoparticles. On average, in the presence of MOCs, partition coefficients (Kc) of 210Po, 210Pb, and 7Be on nanoparticles increased 2.9-, 5.0- and 5.9-fold, respectively. The effect of MOCs could be explained for 210Po and 210Pb from their different log Kc values on inorganic nanoparticles. In addition, fractionation effects between 210Po and 210Pb (or between 210Pb and 7Be) could be quantified from their relative log Kc values on end-member sorbent components. Applications of both 210Po–210Pb and 7Be–210Pb pairs as particle dynamics tracers could be more quantitative when the nature of the organic coatings is taken into account.
Link to full text: http://www.sciencedirect.com/science/article/pii/S0012821X15002964
延伸阅读：
Weifeng Yang, Laodong Guo, Chia-Ying Chuang, Dorothea Schumann, Marin Ayranov, Peter H. Santschi. Adsorption characteristics of 210Pb, 210Po and 7Be onto micro-particle surfaces and the effects of macromolecular organic compounds. Geochimica et Cosmochimica Acta, 2013, 107: 47-64.
Link: http://www.sciencedirect.com/science/article/pii/S0016703713000021
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