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首页> 美国卫生研究院文献>International Journal of Environmental Research and Public Health >Nitrogen along the Hydrological Gradient of Marsh Sediments in a Subtropical Estuary: Pools Processes and Fluxes
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Nitrogen along the Hydrological Gradient of Marsh Sediments in a Subtropical Estuary: Pools Processes and Fluxes

机译：亚热带河口沼泽沉积物水文梯度上的氮：池过程和通量

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摘要

Knowledge on the distribution of nitrogen (N) pools, processes, and fluxes along hydrological gradients provides a comprehensive perspective to understand the underlying causal mechanisms in intertidal flats, and thus improve predictions and climate adaptation strategies. We used a space-for-time substitution method to quantify N pools, processes, and fluxes along a hydrological gradient. Further, we linked N pools and processes and investigated not only surface but also subsurface sediments. Our results showed a gradual decrease in total N (TN) and mineralization rates (PNmin), but an increase in potential rates of nitrification (PNR) and denitrification (PDNR) under an elevated hydrological gradient, except for TN and PNmin in the subsurface sediment, which accumulated on the interaction zone between the high and middle tidal flats. Most sedimentary ammonium N (NH4+) and nitrate N (NO3−) concentrations were similar; however, NH4+ accumulated on the subsurface of the middle tidal flat. NO3− fluxes (from −0.54 to −0.35 mmol m−2 h−1) were uptake fluxes in the intertidal flats, but NH4+ fluxes (−2.48–3.54 mmol m−2 h−1) changed from uptake to efflux in the seaward direction. Structural equation modeling of the effects of inundation frequency, underground biomass, total carbon (TC), electrical conductivity (EC), and clay proportion on the N processes revealed that these accounted for 67%, 82%, and 17% of the variance of PDNR, PNmin, and PNR, respectively. Inundation frequency, underground biomass, TC, EC, and PNmin effects on N pools accounted for 53%, 69%, and 98% of the variance of NH4+, NO3−, and TN, respectively. This suggests that future sea level rise may decrease N storage due to increase in coupled nitrification–denitrification and decrease in N mineralization, and the NH4+ flux may change from sink to source in intertidal ecosystems.
机译：关于氮（N）池，过程和通量沿水文梯度的分布的知识为了解潮间带滩涂的潜在因果机制提供了一个全面的视角，从而改善了预测和气候适应策略。我们使用了一种时空替代方法来量化沿水文梯度的N个池，过程和通量。此外，我们将N个水池和过程联系起来，不仅调查了地表沉积物，而且还调查了地下沉积物。我们的结果表明，在水文梯度升高的情况下，总氮（TN）和矿化速率（PNmin）逐渐降低，但潜在的硝化（PNR）和反硝化（PDNR）速率增加，但地下沉积物中的TN和PNmin除外堆积在高潮滩和中潮滩之间的相互作用带上。大部分沉积铵态氮（NH4 + ）和硝酸盐氮（NO3 -）的浓度相似。但是，NH4 + 积累在中潮滩的地下。 NO3 -通量（从-0.54至-0.35 mmol m -2 h -1 ）是潮间带的通量，而NH4 < sup> + 通量（−2.48–3.54 mmol m −2 h -1 ）在向海的方向上从吸收变为流出。对淹没频率，地下生物量，总碳（TC），电导率（EC）和黏土比例对N过程影响的结构方程模型表明，这些因素分别占N方差的67％，82％和17％。 PDNR，PNmin和PNR。淹水频率，地下生物量，TC，EC和PNmin对N池的影响分别占NH4 + ，NO3 -变化的53％，69％和98％和TN。这表明未来的海平面上升可能会由于硝化-反硝化作用的耦合和氮矿化的减少而减少氮的储存，潮间带生态系统中的NH4 + 通量可能会从汇变为源。

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