Geochemical behavior of phosphorus and iron in porewater in a mangrove tidal flat and associated phosphorus input into the ocean
Geochemical behavior of phosphorus and iron in porewater in a mangrove tidal flat and associated phosphorus input into the ocean
复制标题
红树林滩涂孔隙水中磷和铁的地球化学行为以及相关磷输入海洋
DOI：
10.1016/j.csr.2017.09.012
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发表时间：
2017-11-01
影响因子：
2.3
通讯作者：
Gao, Aiguo
中科院分区：
文献类型：
--
作者：
Pan, Feng;Liu, Huatai;Gao, Aiguo
深入了解沉积物-水界面上磷（P）和铁（Fe）的分布和地球化学行为是估算沉积物孔隙水与上覆海水交换通量的基础。采用原位高分辨率薄膜扩散梯度技术（ZrO-Chelex DGT）对九龙江口红树林潮滩沉积物间隙水中溶解态活性磷（DRP）和亚铁离子（Fe 2+）的深度分布进行了研究。DRP和Fe 2+的浓度范围分别为0.014 - 0.288 mg L-1和0.003-0.619 mg L-1，在这些配置文件中具有高度异质性。绝大多数剖面的DRP与Fe ~（2+）浓度呈正相关，说明Fe ~（2+）的氧化还原循环在控制DRP变化中起着重要作用。然而，在某些剖面中，这种耦合关系受到红树林有机质或生物活动（如大型底栖动物和微生物）的富集的干扰。由潮汐和波浪设置驱动的再循环海水通量分别计算为23.15 m（3）m（-1）d（-1）和1.49 x 10（-3）m（-1）d（-1）。根据这些计算的通量和端元浓度，计算出进入海洋的净DRP通量约为1.57 mmol m（-2）d（-1），这比DRP的分子扩散通量（1.79 x 10（-3）mmol m（-2）d（-1））大得多。这些结果表明，回流海水的平流输送是将DRP输送到海洋的重要途径，在未来的河口或近海营养盐收支中，应考虑来自红树林潮滩或淤泥质海岸带的这种内源磷。
A thorough understanding of the distribution and geochemical behavior of phosphorus (P) and iron (Fe) across the sediment-water interface (SWI) is essential for estimating the exchange flux between sediment porewater and overlying seawater. In this study, in situ high-resolution diffusive gradients in thin films (DGT) technique, ZrO-Chelex DGT, were applied to investigate the depth profiles of dissolved reactive phosphorus (DRP) and ferrous iron (Fe2+) in sediment porewater in a mangrove tidal flat of the Jiulong River estuary, China. The concentrations of DRP and Fe2+, which ranged from 0.014 to 0.288 mg L-1 and 0.003-0.619 mg L-1, respectively, were highly heterogeneous across these profiles. The positive correlation between DRP and Fe2+ concentrations in most parts of the profiles verified the key role of Fe-redox cycling in controlling DRP variations. However, in some parts of the profiles, this coupling relationship was disturbed by the enrichment of mangrove organic matter or biological activity, such as that of macrobenthos and microorganisms. The recirculated seawater fluxes driven by tides and wave setups were calculated to be 23.15 m(3) m(-1) d(-1) and 1.49 x 10(-3) m(3) m(-1) d(-1), respectively. Based on these calculated fluxes and end-member concentrations, the net DRP flux into the ocean was calculated to be approximately 1.57 mmol m(-2) d(-1), which is much larger than the molecular diffusion flux of DRP (1.79 x 10(-3) mmol m(-2) d(-1)). These results indicate that the advection of recirculated seawater is a significant pathway to deliver DRP into the ocean and that this kind of internal phosphorus from mangrove tidal flats or muddy coastal zones should be considered in future nutrient budgets of estuaries or coastal oceans.