7Be、 210Po和210Pb適合于研究周年及年際時間尺度內上層海洋顆粒物的循環與輸出過程，是GEOTRACES計劃（全球海洋元素及其同位素生物地球化學循環研究計劃）重點關注的同位素。綜合早期的研究發現，對海洋中210Po、210Pb和7Be與顆粒物之間的相互作用認識很少，難以回答“210Po、210Pb和7Be示蹤的是顆粒物中何種組分”這一問題。
我院楊偉鋒教授等人先前已研究發現大分子有機化合物可能是調控顆粒物清除210Po、210Pb的關鍵組分，并提出了開闊大洋和近岸海域調控210Po、210Pb清除的關鍵顆粒物組分可能不同的觀點（Yang et al., GCA, 2013）。近期，楊偉鋒等人進一步研究了有機膠體粒子和無機膠體粒子與210Po、210Pb和7Be相互作用，發現蛋白質、腐殖酸、多糖使無機膠體粒子吸附210Po、210Pb和7Be的能力增強，并就顆粒物組分對210Po與210Pb的分餾作用以及對210Pb與7Be的分餾作用進行了初步量化，形成了膠體粒子與三種核素相互作用的框架性認知，為將來把分餾效應納入這些同位素指標的地球化學模型奠定了基礎。
本成果近期發表在地學一區期刊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.
Full text link: http://www.sciencedirect.com/science/article/pii/S0012821X15002964
延伸閱讀：
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
