Can root exudates from emergent wetland plants fuel denitrification in subsurface flow constructed wetland systems
Can root exudates from emergent wetland plants fuel denitrification in subsurface flow constructed wetland systems
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DOI：
10.1016/j.ecoleng.2013.02.014
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发表时间：
2013-12
影响因子：
3.8
通讯作者：
Xu Zhai;Narumol Piwpuan;C. Arias;T. Headley;H. Brix
中科院分区：
文献类型：
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作者：
Xu Zhai;Narumol Piwpuan;C. Arias;T. Headley;H. Brix
在潜流人工湿地系统中，根系萌发的湿地植物可以通过根系分泌物释放有机碳，促进富含硝酸盐和低碳废水的微生物反硝化过程。以人工湿地中常用的芦苇、黄菖蒲和灯心草3种湿地植物为研究对象，对植物根系释放的溶解有机碳（DOC）进行了定量研究。在2种温度（10和20 °C）和3种光照条件（正常14 h：10 h光：暗循环、连续光照和连续黑暗）下水培植物，分析根系DOC释放速率以及NH 4-N、NO3-N、PO 4-P和K的吸收速率。3种植物的DOC释放速率存在显著差异，并受温度和光照条件的影响。在20 °C时，根系分泌物中DOC的释放量通常高于10 °C时。三种植物的DOC平均释放速率在光照下（10.2 ± 0.7 μg g− 1 root DM h−1）比在黑暗中（6.8 ± 0.7 μg g g− 1 root DM h −1）高近两倍。正如预期的那样，DOC释放速率与相对生长速率（RGR）和养分吸收速率呈正相关。DOC释放速率占净光合固定碳的0.6-4.8%。将实验室测量结果外推到野外条件表明，植物根系分泌物可能会在潜流人工湿地中产生94-267 kg N ha− 1 year − 1的反硝化速率。因此，根分泌物是潜在的重要的有机碳源，在轻负荷潜流人工湿地系统接收富含硝酸盐的水与低含量的BOD（如硝化废水或农业排水）的反硝化作用。
Rooted emergent wetland plants may deliver organic carbon via root exudates to fuel the microbial denitrification process in subsurface flow constructed wetland systems receiving nitrate-rich and low-carbon wastewater. We quantified the amount of dissolved organic carbon (DOC) released from roots of three wetland species,Phragmites australis,Iris pseudacorusandJuncus effusus, which are commonly used in constructed wetlands. Plants were grown hydroponically at two temperatures (10 and 20 °C) and three light-regimes (a normal 14 h:10 h light:dark cycle, continuous light and continuous dark), and the release rates of DOC from the roots as well as the uptake rates of NH4-N, NO3-N, PO4-P and K were analyzed. DOC release rates were significantly different among the three species, and were also affected by temperature and light-regime. At 20 °C, higher amounts of DOC were generally released in the root exudates than at 10 °C. The average DOC release rate of the three species was nearly two times higher in the light (10.2 ± 0.7 μg g−1root DM h−1) than in the dark (6.8 ± 0.7 μg g−1root DM h−1). As expected, DOC release rates were positively related to the relative growth rate (RGR) and nutrient uptake rate. DOC release rates amounted to 0.6–4.8% of the net photosynthetically fixed carbon. Extrapolating the laboratory measurements to field conditions suggests that plant root exudates may potentially fuel a denitrification rate of 94–267 kg N ha−1year−1in subsurface flow constructed wetlands. Hence, root exudates are potentially important as an organic C source for denitrification in lightly loaded subsurface flow constructed wetland systems receiving nitrate-rich water with a low content of BOD (e.g. nitrified effluent or agricultural drainage).