闽江感潮河段2018—2020年枯水期DOM图谱及特征参数影响

Changes of DOM Spectrum and Characteristic Index in the Tidal Reach of Minjiang River during Dry Season from 2018 to 2020

选取闽江感潮河段,进行2018—2020年连续3年枯水期溶解性有机物(DOM)监测实验,获取不同河段涨落潮DOM的三维荧光图谱,并对DOM荧光特征参数进行相关性和主成分分析(PCA),得到如下结果。1)研究区域三年枯水期的DOM由人为源腐植酸C1(Ex/Em=220~240nm/330~370 nm)、陆地源腐殖质C2(Ex/Em=220~240nm/405~445 nm)及游离氨基酸与蛋白质结合类物质C3(Ex/Em=255~285nm/310~360 nm)组成。上游河流段DOM受水库调度和人为输入影响,中游河流段DOM与组分性质和内外源输入有关,下游河口段DOM则表现为外海稀释和污染阻滞两种作用特点。C1为研究区域的特征污染物。2)荧光特征参数FI,BIX和Fn(355)呈现逐年下降的趋势,HIX指数先降低后升高;沿水流方向,FI和HIX呈上升趋势,BIX和Fn(355)呈下降趋势,越接近河口水体,外源性和自生源特征越明显。3)相关性分析发现,研究区域DOM荧光特征参数可能受到盐度和溶解氧(DO)的影响,当下泄流量较大时,溶解性总氮(DTN)和溶解性总磷(DTP)也有较大的影响;PCA结果显示,2020年研究区域DOM荧光特征参数组成与2018和2019年有较大的差异,可能与2020年下泄流量较高有关。

Three in-field investigations of dissolved organic matter(DOM)in the dry seasons from 2018 to 2020 were conducted in the Minjiang tidal reach.Three-dimensional fluorescence spectra of DOM of ebb and flow tides in different river sections were obtained.The correlation and principal component analysis(PCA)were used to assess the DOM fluorescence characteristic index.The results suggested that there were three types of fluorescence components in the research area including human-derived humic acid C1(Ex/Em=220–240 nm/330–370 nm),terrestrial humic acid C2(Ex/Em=220–240 nm/405–445 nm)and free amino acid and protein substance C3(Ex/Em=255–285 nm/310–360 nm).DOM in the upstream river reach was influenced by the reservoir operation and the human input.while in the middle river segment it was related to DOM component properties and the internal and external source input.The dilution and pollution block of sea water played important roles in the downstream estuary area.Besides,C1 was the characteristic pollutant in the research area.The FI,BIX and Fn(355)fluorescence characteristic index showed a decreasing trend year by year,while the HIX index decreased first and then increased.The FI and HIX index increased along the flow direction while BIX and Fn(355)decreased.Meanwhile,the exogenous and autogenic characteristics of the water close to the estuary were more obvious.Correlation analysis suggested that the DOM fluorescence characteristic index could be affected by the salinity and DO in the research area.Besides,dissolved total nitrogen and dissolved total phosphorus also had a great impact on the DOM fluorescence characteristic index when the upstream discharge flow was large.In addition,the PCA results indicated that the DOM fluorescence characteristics in 2020 were quite different from that in 2018 and 2019,which may also be related to the higher discharge from upstream.