辽河口芦苇湿地有色溶解有机物的光谱特征研究

Absorbance and Fluorescence Spectrums of Chromophoric Dissolved Organic Matter in the Reed Wetland of Liaohe Estuary

为深入认识芦苇湿地溶解有机碳的生物地球化学过程,分别于2015年5、6和9月,对辽河口湿地芦苇生长密集区和稀疏区积水进行24h连续监测,通过分析有色溶解有机物(CDOM)的吸收光谱和荧光光谱,来揭示芦苇生长初期、快速生长期和成熟期湿地积水CDOM的组成、性质和转化特征。研究结果表明,CDOM相对含量以5月最高,其吸收系数a(280)约是9和6月的2倍;5和6月CDOM平均分子粒径相当,略高于9月。CDOM荧光组分由高到低依次包括类富里酸、类色氨酸、类腐殖酸、微生物代谢产物和类酪氨酸五大类,其中类腐殖质组分占50%以上。DOC含量、CDOM相对含量和CDOM荧光强度间均呈现极显著正相关关系,说明研究区域CDOM的来源或产生过程具有相似性,或者相伴发生。CDOM吸收光谱和荧光光谱特征与环境理化因子的CCA分析结果表明,芦苇湿地积水中的初级生产是9月CDOM的初始来源,温度和光照是促进CDOM降解和转化的主要因素。芦苇生长初期和快速生长期苇田积水中CDOM主要为自生源,5月主要来自河水与苇田冬季留存有机物再溶解后的混合,6月积水中初级生产活动对溶解有机物有一定程度的添加;9月芦苇生长成熟期苇田积水中初级生产活动最为旺盛,带来旺盛的微生物活动。

In order to investigatebiogeochemistry of dissolved organic matter in reed wetland at Liaohe estuary,diurnal monitoring was carried out in overlying waters at both dense and sparse areas in May,June and September,2015.Absorbance and fluorescence spectrums of chromophoric dissolved organic matter（CDOM）were studiedand the composition,characteristicsand transformation of CDOM were discussed as well.Results showed that,therelative contents of CDOM werehigher in May,and the absorbance coefficient a（280）was about twice as much as those in June and September.Fluorescence components decreased from fulvic-like,tryptophan-like,humic acid-like,and bacteria products totyrosine-like matters in term of fluorescence regional integration（FRI）,in which humic-like matters accounted for over 50 %in the total normalized FRI.It was suggested that a similar source and producing pattern existed among DOC,CDOM and its fluorescence components,based on the statistical analysis results.CCA analysis on the absorbance and fluorescence spectrums of CDOM and environmental factors indicated that,temperature and irradiance played key roles in CDOM transformation and degradation.CDOM in May were abttributed to irrigating water and soil re-dissolving processes,and presented low ratios of protein-like to humic-like matters.CDOM in June were mostly transformed from primary products in overlying water,and presented higher ratios of protein-like to humic-like matters.CDOM in September was dominated by organic matters fromboth primary production and bacterial reproduction,in which more protein-like matters contained in CDOM.