Huang Lei, Chen Yu-Cheng, Zhao Ya-Qi, Xiao Guang-Quan, Yang Zhi-Min
College of Resources and Environment, Southwest University, Chongqing 400715, China.
Chongqing Engineering Research Center of Rural Cleaning, Chongqing 400716, China.
Huan Jing Ke Xue. 2018 Jun 8;39(6):2904-2910. doi: 10.13227/j.hjkx.201801061.
Constructed wetlands (CWs) have high potential for wastewater treatment in developing countries because of their operational convenience and low maintenance costs. However, rapid accumulation of macrophytes in these wetlands, as a result of plant litter recycling, can lead to lower removal efficiencies. Periodic harvesting is consider to be the effective measure to maintain the wastewater treatment performance, and so a lot of harvested plant waste needs to be properly disposed of. However, in China, plant waste is usually used for agricultural burning and the greenhouse gas emissions bring adverse effects on the atmospheric environment. In the traditional subsurface flow CW, the dissolved oxygen (DO) concentration is low, resulting in long-term anoxic or anaerobic conditions, which will bring damages to plant body, such as membrane lipid peroxidation and protein and DNA damage. Generally, the addition of biochar to CWs is beneficial for aeration, and improves the internal environment of wetlands. Hence, the effects of plant biochar on the pollutant purification efficiencies in CWs were studied, and the role of biochar in macrophyte growth and antioxidative response was investigated. Based on the results of biochar application in agricultural fields, the harvested wetland plant straw was pyrolyzed to biochar at 500 ℃ under a dynamic high-purity nitrogen atmosphere. The wetland plant L (AC) was chosen for this study. The impact characteristics of biochar on AC were studied in five independent CWs built in a greenhouse, by combining the analyses of growth and antioxidative responses of plants. Results showed that the removals of ammonium (NH-N) and total nitrogen (TN) were significantly enhanced when biochar was added to CWs and that higher long-term nitrogen removal rates were achieved when the biochar application rate was increased. The photosynthetic pigment content in AC increased significantly with increasing biochar application rate. This stimulated photosynthesis and increased the soluble protein (SP) and plant biomass amounts. Further, glutamine synthetase (GS) activity was strengthened with the addition of biochar. This helped enhance the NH-N metabolism and increased the relative uptake rate of AC. This study confirmed that long-term anoxic or anaerobic conditions in CWs cause membrane lipid oxidation in plants. However, the activity of the antioxidative response system was promoted with the addition of biochar, significantly decreasing the malonic dialdehyde (MDA) content in the plants.
人工湿地（CWs）因其操作简便且维护成本低，在发展中国家具有很高的废水处理潜力。然而，由于植物残体的循环利用，这些湿地中大型植物的快速积累会导致去除效率降低。定期收割被认为是维持废水处理性能的有效措施，因此大量收割的植物废弃物需要妥善处理。然而，在中国，植物废弃物通常用于农业焚烧，而温室气体排放会对大气环境带来不利影响。在传统的潜流人工湿地中，溶解氧（DO）浓度较低，导致长期处于缺氧或厌氧状态，这会对植物机体造成损害，如膜脂过氧化以及蛋白质和DNA损伤。一般来说，向人工湿地添加生物炭有利于通气，并改善湿地的内部环境。因此，研究了植物生物炭对人工湿地中污染物净化效率的影响，并探讨了生物炭在大型植物生长和抗氧化反应中的作用。基于生物炭在农业领域的应用结果，将收割的湿地植物秸秆在动态高纯氮气氛下于500℃热解为生物炭。本研究选用了湿地植物L（AC）。通过结合植物生长和抗氧化反应的分析，在温室中建造的五个独立人工湿地中研究了生物炭对AC的影响特性。结果表明，向人工湿地添加生物炭时，铵（NH-N）和总氮（TN）的去除率显著提高，且随着生物炭施用量的增加，长期氮去除率更高。AC中的光合色素含量随着生物炭施用量的增加而显著增加。这刺激了光合作用，增加了可溶性蛋白（SP）和植物生物量。此外，添加生物炭后谷氨酰胺合成酶（GS）活性增强。这有助于增强NH-N代谢，提高AC的相对吸收速率。本研究证实，人工湿地中的长期缺氧或厌氧条件会导致植物膜脂氧化。然而，添加生物炭促进了抗氧化反应系统的活性，显著降低了植物中的丙二醛（MDA）含量。
