不同收割时间下人工湿地芦苇根系分泌物的组成和特征

Composition and Characteristics of Reed(Phragmites australis)Root Exudates in Constructed Wetlands at Different Harvest Time

为探讨亚热带地区枯萎期湿地有机物和氮去除效果与芦苇根系分泌物对收割时间的响应,运用水平潜流湿地开展了2年(第1年为2017年7月—2018年3月,第2年为2018年8月—2019年4月)不同收割时间(W1为不收割、W2为枯萎前收割、W3为枯萎中期收割、W4为枯萎末期收割)试验,监测了不同处理下芦苇根系分泌物的组成特征及湿地中有机物和氮浓度的变化.结果表明:①2年试验均表现为枯萎前收割处理湿地TOC去除率降低,枯萎末期收割处理湿地TOC去除率增加的特征.②芦苇根系分泌物中烷烃类数量占比最高,2年试验收割处理后根系分泌物数量均呈降低趋势.③进水ρ(TN)较高的年份,根系分泌物中烷烃类相对含量最高,收割处理后烷烃类相对含量增加;进水ρ(TN)较低的年份,酸类相对含量最高,枯萎前和中期收割后酸类相对含量增加,枯萎末期收割后酸类相对含量降低.④进水ρ(TN)较高的年份,湿地TOC和TN去除率的变化整体上由烷烃类含量主导,二者与烷烃类含量均呈正相关;进水ρ(TN)较低的年份,湿地TOC和TN去除率的变化整体上由酸类含量主导,二者与酸类含量均呈负相关.研究显示,枯萎期芦苇湿地污染物去除效果与根系分泌物的组成和特征存在一定的相关性,在枯萎末期收割能增加芦苇湿地的有机物去除效果.

In order to investigate the response of organic matter and nitrogen removal efficiency of wetlands and characteristics of reed root exudates to different harvest time in the subtropical region,a two-year experiment(the first year from July 2017 to March 2018,and the second year from August 2018 to April 2019)was carried out in horizontal subsurface constructed reed wetlands at four different reed harvest time:W1(un-harvest),W2(harvest before wilting),W3(harvest at mid-wilting),and W4(harvest at late wilting),and the composition and characteristics of reed(Phragmites australis)root exudates and TOC concentration in wetlands was monitored.The results showed that:(1)Wetland TOC removal efficiency decreased when reeds were harvested before wilting,and increased when harvest at late wilting stage in the two experimental years.(2)The number of alkanes in the reed root exudates was the highest,the root exudates decreased after the reeds were harvested,and the results were similar in the two experimental years.(3)The relative content of alkanes in reed root exudates was the highest in the year with higher influent TN concentration,and increased after the reeds were harvested;In the year with lower influent TN concentration,the relative content of acids in root exudates was the highest,it increased under harvest before wilting and in mid-wilting treatments,but decreased under harvest at late wilting treatment.(4)The wetland TOC and TN removal efficiency were positively correlated with content of alkanes,and alkanes were the main factor in the year with higher influent TN concentration;In the year with lower influent TN concentration,acid content was the main influence factor,which negatively correlated with the wetland TOC and TN removal efficiency.The results indicated that the composition and characteristics of reed root exudates were related to the pollutant removal efficiency in reed wetlands,and reeds harvested at late wilting stage could increase the wetland organic removal.