潮滩沉积物-水界面磷、铁的高分辨率分布特征及生物地球化学行为

High-Resolution Distribution and Biogeochemical Behavior of Phosphorus and Iron at Sediment-Water Interface of Tidal Flat

为了解潮间带微环境中磷、铁元素的分布和耦合规律及对磷释放的影响,借助薄膜扩散梯度技术(ZrO-Chelex DGT)原位高分辨率获取九龙江口红树林潮滩孔隙水剖面的溶解活性磷(DRP)、Fe^(2+)浓度,并测定沉积物相应的理化参数.研究结果表明:(1)在表层孔隙水中,DRP、Fe^(2+)浓度呈现显著的正相关性,证实了磷、铁元素的耦合关系以及沉积物铁氧化物对磷吸附/解吸附的控制作用;(2)在深部还原带,DRP浓度相对Fe^(2+)浓度具有较大的波动,主要受到沉积物异质性以及红树植物吸收等的影响;(3)根据表层孔隙水中DRP的浓度梯度计算获得磷的分子扩散通量为0.000 64～0.006 00μg·cm^(-2)·d^(-1),结果远低于一般湖泊沉积物内源磷的扩散通量,原因是富铁且具较深氧化带的潮滩沉积物中的磷-铁耦合关系有效地抑制了磷的释放.

To find out distribution and coupling pattern of iron and phosphorus, as well as impact on phosphorus release in microenvironment of intertidal region, with the help of diffusive gradients in thin films technique （ZrO-Chelex DGT）, we obtained in-situ high-resolution DRP and Fe2＋ concentrations in porewater profiles of mangrove tidal flat in Jiulong River estuary, as well as the corresponding sediment properties in this study. The results show： （1） In surface porewater, the remarkable positive correlation between DRP and Fe2＋ verified the coupling relationship of these two elements and the crucial effects of sediment iron （Ⅲ） （oxyhydr） oxides on the absorption/desorption of phosphorus; （2） in deep anoxic porewater, on account of sediment heterogeneity and absorption by mangrove plants, DRP concentrations presented obvious fluctuations compared with Fe2＋ ; （3） the molecular diffusion flux was estimated ranging from 0.000 64 to 0.006 00μg · cm-2 · d-1 based on DRP concentrations gradient in surface porewater, which are much lower than results of general lake research. The main reason is P-Fe coupling in this iron-rich tidal flat sediment with deep oxidation zone which effectively restrains phosphorus release,