Division of Engineering and Applied Science, California Institute of Technology, Pasadena, California 91125, USA.
Environ Sci Technol. 2010 Jan 1;44(1):41-6. doi: 10.1021/es901572h.
In situ rates of reductive dissolution in submerged shoreline sediments at Lake Tegel (Berlin, Germany) were measured with a novel hydrous manganese (Mn) oxide-doped gel probe sampler in concert with equilibrium gel probe and sequential extraction measurements. Rates were low in the top 8 cm, then showed a peak from 8 to 14 cm, with a maximum at 12 cm depth. This rate corresponded with a peak in dissolved porewater iron (Fe) at 11 cm depth. Below 14 cm, the reductive dissolution rate reached an intermediate steady value. Lower rates at depth corresponded with increases in operationally defined fractions of carbonate-bound and organic- and sulfide-bound Mn and Fe as detected by sequential extraction. Observed rates of reductive dissolution, which reflect a capacity for Mn reduction rather than actual rates under ambient conditions, appear to correlate with porewater chemistry and sequential extraction fractions as expected in early sediment diagenesis, and are consistent with previous measurements of in situ reductive dissolution rates. Significant downward advection in this bank filtration setting depletes the Mn and Fe oxides in the sediments and enhances the transport of dissolved Fe and Mn into the infiltrating water.
在德国柏林的特格尔湖（Lake Tegel）水下岸线沉积物中，使用一种新型的水合氧化锰（Mn）掺杂凝胶探针采样器，与平衡凝胶探针和连续提取测量相结合，原位测量了还原溶解的速率。在顶部 8 厘米处的速率较低，然后在 8 到 14 厘米处出现峰值，最大深度为 12 厘米。这一速率与 11 厘米深处溶解的孔隙水中铁（Fe）的峰值相对应。在 14 厘米以下，还原溶解速率达到了一个中间稳定值。在深度上较低的速率与通过连续提取检测到的碳酸盐结合态、有机结合态和硫化物结合态 Mn 和 Fe 的操作定义分数的增加相对应。所观察到的还原溶解速率反映了 Mn 还原的能力，而不是在环境条件下的实际速率，与孔隙水化学和连续提取分数相关，这在早期的沉积物成岩作用中是预期的，并且与之前原位还原溶解速率的测量结果一致。在这种河岸过滤设置中，显著的向下对流会耗尽沉积物中的 Mn 和 Fe 氧化物，并增强溶解的 Fe 和 Mn 向渗透水中的传输。
