苦草在生态修复中的水质提升与气味物质(Azulene)释放风险

Enhancement of water quality and odor substance (Azulene) release risks in ecological restoration using Vallisneria natans

  • 摘要: 苦草作为湖泊生态修复的常用沉水植物,在改善水质的同时可能释放气味物质,但关于苦草释放气味物质特征及其对水体的影响机制的研究尚不充分。以武汉某滨湖湿地修复工程中种植苦草的生态塘为研究对象,逐月监测(2023年4—12月)苦草生长过程中生态塘水体理化指标总氮(TN)、总磷(TP)、叶绿素a(Chla)的变化规律以及苦草释放的气味物质薁(Azulene)的特征,并运用结构方程模型探讨环境因子对气味物质释放的影响。结果表明:苦草种植后生态塘水质显著改善,TP、TN和Chla浓度分别下降84.5%、31.4%和55.6%,水体透明度(SD)提升315%,溶解氧(DO)浓度增加21.1%。同时,苦草在生长及代谢过程中释放多种气味物质,Azulene为主要成分,其峰值浓度(9月)达到(293.65±22.51)ng/L;随水温降低,Azulene浓度显著下降,12月相较9月下降了78.14%,仅为(64.19±15.23)ng/L。相关性及结构方程模型分析表明,水温对苦草盖度有极显著正向调控(路径系数0.97,P<0.001),苦草盖度直接促进叶片及水体中Azulene浓度升高(路径系数分别为0.95和0.96,P<0.001);Azulene浓度与氮、磷、Chla浓度均呈显著负相关(P<0.05),与SD、pH、苦草盖度呈正相关(P<0.05)。研究表明,苦草种植在显著提升水体水质的同时,也带来了气味物质释放所致的感官效应,尤其是Azulene的释放与苦草生长和水温密切相关;在水生态修复工程实践中,既要权衡水质改善与气味物质释放的双重效应,关注气味物质释放的感官效应,也应研究其对水质和生态系统的影响机制及生态功能。

     

    Abstract: Vallisneria natans (V. natans), a widely utilized submerged plant for lake ecological restoration, improves water quality but can release odorants. However, research on the characteristics of odorant release from V. natans and its mechanisms of impact on aquatic environments remains insufficient. This study investigated an ecological pond planted with V. natans in a lakeside wetland restoration project in Wuhan. Changes in physical and chemical indicators of total nitrogen (TN), total phosphorus (TP), and chlorophyll a (Chla) in the ecological pond water during the growth process of V. natans were monitored monthly (from April to December, 2023) to analyze the characteristics of the primary odorant, Azulene, released by V. natans. The influence of environmental factors on the release of odor substances was explored by using the structural equation model (SEM). The results showed that after the cultivation of V. natans, the water quality of the ecological pond was significantly improved. The concentrations of TP, TN and Chla decreased by 84.5%, 31.4% and 55.6%, respectively; the water transparency (SD) increased by 315%, and the dissolved oxygen (DO) concentration increased by 21.1%. Concurrently, V. natans released a range of volatile odorants during its growth and metabolism, with Azulene being the main component. The peak concentration of Azulene in the water column reached (293.65±22.51) ng/L in September. With the decrease of water temperature, the concentration of Azulene decreased significantly. Compared with September, it dropped by 78.14% in December, reaching a low of (64.19±15.23) ng/L. Correlation analysis and SEM revealed that water temperature exerted a highly significant positive effect on V. natans coverage (path coefficient=0.97, P<0.001), and increased coverage directly elevated the Azulene concentrations in both the leaf and water (path coefficients=0.95 and 0.96, respectively; P<0.001). Azulene concentrations in the water were significantly negatively correlated with TN, TP, and Chla (P<0.05), and positively correlated with SD, pH, and V. natans coverage (P<0.05). This study indicates that while the cultivation of V. natans significantly improves water quality, it also leads to sensory effects arising from the release of odorant compounds, especially the release of Azulene, which is closely related to the growth of V. natans and water temperature. In the practice of water ecological restoration projects, it is important to balance the dual effects of water quality improvement and the release of odorous compounds, giving consideration to their sensory impacts while also conducting in-depth research into their mechanisms of influence and ecological functions within water bodies and ecosystems.

     

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