Bezbaruah Achintya N, Zhang Tian C
URS Corporation, 12120 Shamrock Plaza, Suite 300, Omaha, Nebraska 68154, USA.
Biotechnol Bioeng. 2005 Feb 5;89(3):308-18. doi: 10.1002/bit.20332.
Amount of oxygen released by bulrush (Scirpus validus) roots has been quantified based on the radial oxygen loss (ROL) exhibited by the roots, the number and the length of active lateral roots, and the field plant density. It was found that wetland bulrush contains two types of active lateral roots (showing ROL), viz., laterals of brown and white main roots. The two laterals have distinct oxygen release characteristics. Based on the dissolved oxygen (DO) microprofiles of brown and white laterals, the ROLs were found to be approximately 61 ng O2 cm(-2) root surface min(-1) and approximately 68 ng O2 cm(-2) root surface min(-1), respectively, at bulk 5-day biochemical oxygen demand (BOD5) of 76 mg L(-1). The respective average active root lengths of the brown and the white laterals were approximately 40 and approximately 1676 microm. Based on field and laboratory measurements, the average amount of oxygen released by bulrush was found to be 2.30 mg O2 m(-2) wetland surface d(-1); of this approximately 71% is from the white roots. The results of this study indicate that plants do not release enough oxygen to meet the total oxygen demand of bulk wastewater, and therefore, constructed wetlands should be designed as an anaerobic or an aerobic-anaerobic hybrid system rather than as an aerobic system. However, the results of this study should be viewed in the background of possible errors (including a reactor design flaw), which might have made the measured oxygen release significantly lower than what plant roots actually release. Further studies are needed to quantify wetland plant oxygen release based on micro-scale measurements.
基于芦苇（Scirpus validus）根系表现出的径向氧损失（ROL）、活性侧根的数量和长度以及田间植物密度，对芦苇根系释放的氧量进行了量化。研究发现，湿地芦苇含有两种类型的活性侧根（表现出ROL），即棕色主根和白色主根的侧根。这两种侧根具有不同的氧释放特征。根据棕色和白色侧根的溶解氧（DO）微剖面，发现在5日生化需氧量（BOD5）为76 mg L(-1)时，ROL分别约为61 ng O2 cm(-2)根表面min(-1)和约68 ng O2 cm(-2)根表面min(-1)。棕色和白色侧根各自的平均活性根长度分别约为40微米和约1676微米。基于田间和实验室测量，发现芦苇释放的平均氧量为2.30 mg O2 m(-2)湿地表面d(-1)；其中约71%来自白色根系。本研究结果表明，植物释放的氧气不足以满足大量废水的总需氧量，因此，人工湿地应设计为厌氧或好氧-厌氧混合系统，而不是好氧系统。然而，本研究结果应在可能存在误差（包括反应器设计缺陷）的背景下看待，这些误差可能使测得的氧释放量显著低于植物根系实际释放的量。需要进一步研究基于微观尺度测量来量化湿地植物的氧释放。
