Linking Seasonal Changes in Organic Matter Composition and Nutrients to Shifting Hydraulic Gradients in Coastal Urban Canals
Linking Seasonal Changes in Organic Matter Composition and Nutrients to Shifting Hydraulic Gradients in Coastal Urban Canals
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DOI：
10.1029/2022wr033334
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发表时间：
2023-01
影响因子：
5.4
通讯作者：
M. A. Smith;J. Kominoski;R. Price;O. Abdul‐Aziz;T. Troxler
中科院分区：
文献类型：
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作者：
M. A. Smith;J. Kominoski;R. Price;O. Abdul‐Aziz;T. Troxler
沿海河网对溶解性有机物（DOM）的迁移转化能力已被广泛接受。然而，气候引起的暴雨径流和潮汐扩展的变化改变了淡水和海洋水源的贡献，相关的DOM以及进入沿海运河的营养物质的处理速率。我们研究了沿海水源贡献之间的时变相互作用如何影响城市运河中溶解有机碳（DOC），营养盐和DOM组成的浓度。我们量化的DOM质量和营养盐浓度的时空变异，以确定潮汐海水，雨水，雨水径流，地下水的贡献，三个沿海城市运河的迈阿密，佛罗里达（美国）。我们使用荧光DOM（fDOM）、DOC浓度、δ 18 O和δ 2 H同位素特征以及氯化物（Cl−）的测量值创建了贝叶斯蒙特卡罗混合模型。地下水的贡献率平均为17%，在旱季和26%的高峰高潮在亚热带雨季（9月至11月）。运河与海洋水头差（CMHD）是地下水对沿海城市运河和fDOM/DOC月度模式贡献的主要驱动力。涨潮（>1米）和放电事件被发现连接渠道的上游来源的陆地DOM。负载的terrestrially来源的DOC和DOM脉冲到城市运河，分流下游和补充微生物来源的DOM在雨季涨潮。总体而言，我们证明，同位素和fDOM的联合示踪方法可以帮助确定地下水对沿海水道的贡献，并且随着CMHD向内陆推进，本地fDOM可能会引发碳或营养物质的降解。
The capacity for coastal river networks to transport and transform dissolved organic matter (DOM) is widely accepted. However, climate‐induced shifts in stormwater runoff and tidal extension alter fresh and marine water source contributions, associated DOM, and processing rates of nutrients entering coastal canals. We investigate how time‐variable interactions among coastal water source contributions influence the concentrations of dissolved organic carbon (DOC), nutrients, and DOM composition in urban canals. We quantified the spatiotemporal variability of DOM quality and nutrient concentrations to determine contributions of tidal marine water, rainwater, stormwater runoff, and groundwater to three coastal urban canals of Miami, Florida (USA). We created a Bayesian Monte Carlo mixing model using measurements of fluorescent DOM (fDOM), DOC concentrations, δ18O and δ2H isotopic signatures, and chloride (Cl−). Fractional contributions of groundwater averaged 17% in the dry season and 26% at peak high tide during the subtropical wet season (September–November). The canal‐to‐marine head difference (CMHD) was a primary driver of groundwater contributions to coastal urban canals and monthly patterns of fDOM/DOC. High tide (>1 m) and discharge events were found to connect canals to upstream sources of terrestrial DOM. Loading of terrestrially sourced DOC and DOM is pulsed to urban canals, shunted downstream and supplemented by microbially sourced DOM during the wet season at high tide. Overall, we demonstrate that a combined tracer approach with isotopes and fDOM can help identify groundwater contributions to coastal waterways and that autochthonous fDOM may prime the degradation of carbon or nutrients as the CMHD pushes inland.