The flux of soluble organic-iron(III) complexes from sediments represents a source of stable iron(III) to estuarine waters and to the continental shelf
The flux of soluble organic-iron(III) complexes from sediments represents a source of stable iron(III) to estuarine waters and to the continental shelf
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DOI：
10.4319/lo.2011.56.5.1811
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发表时间：
2011-09-01
影响因子：
4.5
通讯作者：
Taillefert, Martial
中科院分区：
文献类型：
--
作者：
Jones, Morris E.;Beckler, Jordon S.;Taillefert, Martial
以1-亚硝基-2-萘酚(1N2N)为配体，采用竞争配位平衡-吸附阴极溶出伏安法(CLE-ACSV)研究了萨提拉河口水中铁的形态分布。黑水Satilla河含有高浓度的溶解有机物和铁，这表明它可能为大陆架提供溶解铁的来源。河口沿岸水体中的总溶解铁减少，这可能是由于与盐度增加相关的絮凝和降水过程所致。同时，CLE-ACSV测得的沉积物上覆水中溶解的有机-Fe(III)络合物的百分比随着盐度的增加而增加。孔隙水中溶解铁的形态表明，这些络合物起源于下伏的沉积物。根据沉积物深度剖面计算的扩散通量表明，在河流低流量时，只有8%的Fe(III)沉积通量被输送到大陆架。在正常水流条件下，Fe(III)的泥沙通量占河流总Fe(III)通量的63%。这些发现表明，溶解铁进入大陆架的通量是由河口铁的沉积和沉积物中铁还原或Fe(II)氧化形成的可溶性有机-Fe(III)络合物的再动员控制的。萨蒂拉河河口产生的溶解Fe(III)浓度是世界平均主要河流的五到八倍，这表明它与其他小黑水河流一样，目前在世界平均河流流量计算中的比例较低。
Iron speciation in the Satilla River Estuary was investigated using competitive ligand equilibration-adsorptive cathodic stripping voltammetry (CLE-ACSV) with the ligand 1-nitroso-2-naphthol (1N2N). The blackwater Satilla River contains high concentrations of dissolved organic matter and iron, suggesting that it could provide a source of dissolved iron to the continental shelf. Total dissolved iron in the water column decreases along the estuary, likely due to flocculation and precipitation processes associated with the increase in salinity. Simultaneously, the percentage of dissolved organic-Fe(III) complexes measured by CLE-ACSV in overlying waters of sediment cores increases with salinity. The speciation of dissolved iron in the pore waters indicates that these complexes originate in the underlying sediments. Diffusive fluxes calculated from depth profiles in the sediments indicate that only 8% of the sedimentary flux of Fe(III) is delivered to the continental shelf during low riverine discharge. During normal flow conditions, however, the sediment flux of Fe(III) represents 63% of the total riverine flux of Fe(III). These findings suggest that the flux of dissolved iron to the continental shelf is controlled by the sedimentation of iron in the estuary and the remobilization of soluble organic-Fe(III) complexes produced either during iron reduction deep in the sediment or oxidation of Fe(II) close to the sediment-water interface. The Satilla River Estuary generates five to eight times higher concentrations of dissolved Fe(III) than the average major world rivers, suggesting that it is, along with other small blackwater rivers, currently underrepresented in world average river flux calculations.