Geochemical and anthropogenic enrichments of Mo in sediments from perennially oxic and seasonally anoxic lakes in Eastern Canada
Geochemical and anthropogenic enrichments of Mo in sediments from perennially oxic and seasonally anoxic lakes in Eastern Canada
复制标题
DOI：
10.1016/j.gca.2007.10.014
复制
发表时间：
2008-01-01
影响因子：
5
通讯作者：
Tessier, Andre
中科院分区：
文献类型：
--
作者：
Chappaz, Anthony;Gobeil, Charles;Tessier, Andre
我们测量了垂直分布的钼，铁，锰，硫化物，硫酸盐，有机碳，主要离子，和pH值的沉积物孔隙水从一个常年好氧和三个季节性缺氧湖盆在加拿大东部，以及那些钼，酸挥发性硫化物，铁，锰，铝，有机碳，（210）铅和Cs-137沉积物芯从相同的网站。人类活动对这些湖泊的贡献仅来自大气沉积，三个季节性缺氧盆地孔隙水中Mo的分布相对单调，表明缺氧期间Mo在沉积柱中没有再分布。相比之下，孔隙水钼剖面在三个采样日期在常年好氧盆地显示尖锐的钼峰以下的沉积物-水界面，沉积后的再分配。用成岩反应-输运方程对这些孔隙水Mo剖面进行建模，并与各种孔隙水和固相剖面进行比较，结果表明，由于Fe羟基氧化物的还原溶解，Mo在1-2 cm深度处释放，并在沉积物-水界面附近通过再吸附到自生Fe羟基氧化物上而被清除，而在沉积物深处，溶解的硫化物浓度较高。Fe羟基氧化物吸附Mo的速率常数为36 +/- 45 cm（3）mol（-1）s（-1）。成岩模拟表明，在沉积物-水界面以下的第一cm，沉积物中自生Mo约占固相Mo总量的1/3，而在该层位以下仅占1/10。如果我们假设没有自生钼积累在季节性缺氧的湖泊沉积物中，我们的结论是，沉积物中的钼浓度，这是高达3-16倍高于平均的岩石成分，取决于湖泊，主要是由于大气沉积的人为钼，而不是形成自生钼相。重建的大气钼沉积的历史记录表明，在20世纪70年代和80年代的最大值和显着下降，自那时以来。与有色金属矿石冶炼和煤炭燃烧相关的大气排放似乎是人为钼的最重要来源。(c)2007爱思唯尔有限公司保留所有权利。
We measured the vertical distributions of Mo, Fe; Mn, sulfide, sulfate, organic carbon, major ions, and pH in sediment porewater from one perennially oxic and three seasonally anoxic lacustrine basins in Eastern Canada, as well as those of Mo, acid volatile sulfide, Fe, Mn, Al, organic C, (210) Pb and Cs-137 in sediment cores from the same sites. The only input of anthropogenic Mo to these lakes comes from atmospheric deposition.The relatively monotonous distribution of Mo in the porewater of three seasonally anoxic basins suggests that Mo is not redistributed in the sedimentary column during periods of anoxia. In contrast, porewater Mo profiles obtained at three sampling dates in a perennially oxic basin display sharp Mo peaks below the sediment-water interface, indicating redistribution subsequent to deposition. Modeling of these latter porewater Mo profiles with a diagenetic reaction-transport equation coupled to comparisons among the various porewater and solid phase profiles reveal that Mo is released at 1-2 cm depth as a consequence of the reductive dissolution of Fe oxyhydroxides and scavenged both at the vicinity of the sediment-water interface, by re-adsorption onto authigenic Fe oxyhydroxides, and deeper in the sediments where dissolved sulfide concentrations are higher. The estimated rate constant for the adsorption of Mo onto Fe oxyhydroxides is 36 +/- 45 cm(3) mol(-1) s(-1).Diagenetic modeling indicates that authigenic Mo in sediments of the perennially oxic basin represents about one-third of the total solid phase Mo in the first cm below the sediment-water interface and only one tenth below this horizon. If we assume that no authigenic Mo is accumulated in the seasonally anoxic lake sediments we conclude that the sediment Mo concentrations, which are up to 3-16 times higher than the average lithogenic composition, depending on the lake, are mainly due to atmospheric deposition of anthropogenic Mo and not to the formation of authigenic Mo phases. Reconstructed historical records of the atmospheric Mo deposition indicate maximum values in the 1970s and 1980s and significant decreases since then. Emissions to the atmosphere associated with the smelting of non-ferrous ores and coal combustion appear to be the most important sources of anthropogenic Mo. (c) 2007 Elsevier Ltd. All rights reserved.