Colloids and organic matter complexation control trace metal concentration‐discharge relationships in Marshall Gulch stream waters
Colloids and organic matter complexation control trace metal concentration‐discharge relationships in Marshall Gulch stream waters
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DOI：
10.1002/2016wr019072
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发表时间：
2016-10
影响因子：
5.4
通讯作者：
Kyle D. Trostle;J. Ray Runyon;M. Pohlmann;S. Redfield;J. Pelletier;J. McIntosh;J. Chorover
中科院分区：
文献类型：
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作者：
Kyle D. Trostle;J. Ray Runyon;M. Pohlmann;S. Redfield;J. Pelletier;J. McIntosh;J. Chorover
本研究结合了浓度-排放分析（0.45 μm 过滤）、级联过滤（1.2、0.4 和 0.025 μm）和不对称流场流动分级（AF4），探讨了胶体载体（溶解的有机物和无机纳米颗粒）对圣卡塔利娜山关键区观测站 (SCM) 155 公顷森林流域中痕量金属观测到的浓度-排放关系的影响。 CZO），亚利桑那州。许多主要元素（Na、Mg、Si、K、Ca）没有表现出胶体影响，并且这些物质的浓度-排放关系已由先前的工作解释。然而，大多数痕量金属（Al、Ti、V、Mn、Fe、Cu、Y、REE、U）在标准 0.45 μm 截止过滤时至少显示出胶体对化学的一些影响。具有适度胶体影响的痕量金属的浓度-排放斜率很浅（~0.3），与溶解有机碳（DOC，0.24）测量的相似，而具有较大胶体影响的元素具有更陡的浓度-排放斜率，接近本研究中胶体影响最大的元素铝（0.76）（平均68％）。这些发现得到了 AF4 测量的进一步支持，AF4 测量显示了明显且可解析的低流体动力学直径 DOC 尺寸材料与较大直径无机胶体共存的池，并且这些载体的比例随着放电而系统地变化，因为 DOC 池具有比无机胶体池更浅的浓度-排放关系。这些数据集共同表明，溪流水中痕量金属的正浓度-排放斜率可以解释为微量金属在 DOC 和无机胶体之间的相对分配，而后者的贡献可能由于大孔流动普遍性的增加而增加。
This study combined concentration‐discharge analyses (filtration at 0.45 μm), cascade filtrations (at 1.2, 0.4, and 0.025 μm) and asymmetrical flow field flow fractionation (AF4) to probe the influence of colloidal carriers (dissolved organic matter and inorganic nanoparticles) on observed concentration‐discharge relationships for trace metals in a 155 ha forested catchment of the Santa Catalina Mountains Critical Zone Observatory (SCM CZO), Arizona. Many major elements (Na, Mg, Si, K, Ca) show no colloidal influence, and concentration‐discharge relationships for these species are explained by previous work. However, the majority of trace metals (Al, Ti, V, Mn, Fe, Cu, Y, REE, U) show at least some influence of colloids on chemistry when filtered at the standard 0.45 μm cutoff. Concentration‐discharge slopes of trace metals with modest colloidal influence are shallow (∼0.3) similar to that measured for dissolved organic carbon (DOC, 0.24), whereas elements with greater colloidal influence have steeper concentration‐discharge slopes approaching that of Al (0.76), the element with the largest colloidal influence in this study (on average 68%). These findings are further supported by AF4 measurements that show distinct and resolvable pools of low hydrodynamic diameter DOC‐sized material coexistent with larger diameter inorganic colloids, and the ratio of these carriers changes systematically with discharge because the DOC pool has a concentration‐discharge relationship with shallower slope than the inorganic colloidal pool. Together these data sets illustrate that positive concentration‐discharge slopes of trace metals in stream waters may be explained as the relative partitioning of trace metals between DOC and inorganic colloids, with contributions of the latter likely increasing as a result of increased prevalence of macropore flow.