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水资源是人类赖以生存的必需品和维持经济发展的命脉[1]。流经城镇的河段会因接纳沿岸较为密集的生活、工业、农牧业等污染源,若产生的污染负荷超过水体自净能力将对水生态造成冲击,影响其为沿岸居民提供观赏休憩的功能。河流水体有机物污染是河流综合治理的关键,对河流有机物进行溯源有助于定位污染源头,可有针对性地采取有效的治理措施。因此,为保障水安全、推动经济社会高质量发展、保持稳生态稳定,对河流污染物进行溯源具有重要意义。
可溶性有机物(dissolved organic matter,DOM)是由多种有机物组成的一种复杂混合物,包含单分子和小分子物质(氨基酸、单糖、低分子量有机酸等)和高分子量物质(腐殖物质、蛋白质、多糖等),表现出高度多样性,常被用来评估水质和预测潜在污染[2]。DOM普遍存在于自然水体和废水中,即使是经过深度处理的工业废水仍残留大量DOM。水生生态系统中的DOM来源分为内源(原位水生植物、浮游植物和微生物的生产和分解等)和外源(污水、降水、径流等)[3]。人类活动导致DOM的外源输入显著增加[4]。而不同来源的DOM的化学成分和生物有效性可能存在较大差异[5]。
常规的水质指标如化学需氧量(COD)、生化需氧量(BOD)和总有机碳(TOC)能反映水体有机污染物的总量,但无法表示有机物质结构组成[6]。傅立叶红外变换光谱(FTIR)、气相-质谱联用(GC-MS)、高效液相色谱 (HPLC) 等技术能表征有机物的结构,但通常需要耗费时力对样品进行提取和纯化[3,7]。三维荧光光谱(3D-EEM)技术可用以研究水生环境中DOM的有色和荧光组分,能获得水质样品中DOM荧光团数量、性质和丰度信息,具有快速、灵敏度高、无损样品、成本低等优点。结合平行因子分析(PARAFAC),还可科学地识别水体中相互干扰与叠加的DOM,促进了3D-EEM在DOM结构分析中的应用[8]。
水体3D-EEM的图谱形状、荧光峰位置、荧光峰强度、荧光峰个数信息及荧光参数可以作为荧光特征被用于污染源追溯。TANG等[9]运用三维荧光结合平行因子法(EEM-PARAFAC)分析城市流域和城市周边流域的DOM组成,揭示了流域之间独特的DOM组成归因于不同的人类活动。WANG等[10]运用EEM-PARAFAC对太湖水体中污染物进行溯源,识别出的荧光组分与纺织废水、农业活动和生活废水高度相关,从而发现研究区域受到多种污染源影响。宋庆斌等[11]利用EEM-PARAFAC快速有效地识别出东海区域中有色溶解性有机质(CDOM)的来源,研究结果说明了长江冲淡水等陆源输入对CDOM的显著影响。
本研究拟采用三维荧光及平行因子分析对南昌市某河流进行研究,以期了解水体中DOM的荧光光谱特征,分析水体DOM荧光物质组分组成、类型及对污染物的指征特性,并通过分析不同DOM成分的相对贡献和荧光特征参数对水体DOM溯源,进而诊断该河流存在的主要问题,为城市内地表水的生态环境改善和保护提供参考。
基于三维荧光及平行因子分析的南昌市某河可溶性有机物溯源及治理策略
Dissolved organic matter source identification and treatment strategies of a river in Nanchang based on three-dimensional excitation emission matrix fluorescence spectroscopy and parallel factor analysis
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摘要: 地表河流污染物溯源对污染物防治及河流生态环境改善具有重要意义。三维荧光光谱(3D-EEM)的图谱形状、荧光峰位置、荧光峰强度、荧光峰个数信息和荧光参数可作为水体中可溶性有机物(DOM)的荧光特征。结合平行因子分析(PARAFAC)对南昌市某河的3D-EEMs进行分析并进行DOM溯源研究,结果表明,该河DOM主要包含3个荧光组分,分别为类腐殖质荧光组分C1(λEx/λEm=245 nm/430 nm)、类氨基酸和类腐殖质组分的混合物C2(λEx/λEm=240,300 nm/365 nm)和类色氨酸荧光组分C3(λEx/λEm=225,275 nm/335 nm),分别占总荧光组分的35.93%,26.62%和37.45%。该河基本满足地表水环境质量标准(GB 3838-2002)III类水标准,浮游植物主要为蓝绿藻,河流中磷的来源复杂。污染物溯源结果表明,该河DOM腐殖化程度较低,生物活性较强,主要来源于浮游植物和微生物代谢降解和沉积物在冲击和水力作用下产生的内源污染。建议该河采用生态修复技术并辅助水体曝气系统治理DOM污染,并持续防止河流引入外源污染。Abstract: Pollution source identification of surface river is of great significance for pollution control and improving river ecological environment. The shape, fluorescence peak position, peak intensity, peak number of the there-dimensional excitation emission matrix (3D-EEM) and fluorescence indices are the fluorescence characteristics of dissolved organic matter (DOM). 3D-EEMs of a river in Nanchang were analyzed coupled with parallel factor analysis (PARAFAC) and DOM source identification was conducted. Results showed that the DOM mainly contained three fluorescent components. The components were humic-like component C1 (λEx/λEm=245 nm/430 nm), mixture of amino acid-like and humic-like components C2 (λEx/λEm=240, 300 nm/365 nm) and tryptophan-like component C3 (λEx/λEm=225, 275 nm/335 nm). The contribution rates of the three components to the total fluorescence intensity were 35.93%, 26.62% and 37.45%, respectively. The quality of the river basically reached the class III level of the surface water environmental quality standard (GB 3838-2002). The phytoplankton were mainly blue-green algae, and the sources of phosphorus were complex. The results of pollution source identification showed that DOM in the river had low humification degree and strong biological activity. DOM in this river mainly came from endogenous pollution generated by the metabolic degradation of phytoplankton and microorganisms and sediments under shock and hydraulic action. Results suggested that ecological restoration technology and auxiliary aeration system could be adopted for pollution control of the river, and the exogenous pollution should be prevented continually.
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表 1 水质指标及富营养化指数间的相关性分析
Table 1. Correlation analysis based on water quality parameters and EI
[NH3−N] TN TP N/P 蓝绿藻 Chla EI CODMn −0.240 −0.019 −0.053 −0.041 0.271 0.274 0.127 [NH3−N] 0.282 0.183 0.176 −0.187 −0.186 0.633** TN 0.042 0.938** −0.238 −0.311 0.598** TP −0.173 0.471* 0.383 0.526* N/P −0.282 −0.319 0.470* 蓝绿藻 0.747** 0.171 Chla 0.144 注:**表示0.01级别,相关性极显著;*表示0.05级别,相关性显著。 表 2 4个河段的水质指标情况
Table 2. Water quality indexes of 4 river segments
河段 pH DO/
(mg·L−1)COD/
(mg·L−1)[NH3-N]/
(mg·L−1)TN/
(mg·L−1)TP/
(mg·L−1)蓝绿藻/
(μg·L−1)Chla/
(μg·L−1)上游段 7.28±0.12a 7.87±0.25ab 11.25±4.92a 0.18±0.03a 1.12±0.67a 0.10±0.03b 0.31±0.08b 7.25±0.58a 支流段 6.86±0.19a 8.31±0.07a 12.67±2.31a 0.25±0.17a 1.67±0.40a 0.18±0.03a 1.09±0.63a 9.83±2.56a 中游段 7.04±0.32a 7.91±0.54ab 9.40±3.03b 0.64±0.72a 2.84±2.61a 0.12±0.03b 0.41±0.37b 4.75±1.94b 下游段 6.90±0.22a 7.54±0.17b 15.00±2.65a 0.19±0.04a 4.20±5.20a 0.09±0.03b 0.17±0.06b 4.44±1.39b 注:同列数据后不同小写字母表示同一指标不同河段之间差异达到显著水平(p<0.05)。 表 3 水质指标、荧光组分及荧光参数间的相关性分析
Table 3. Correlation analysis based on water quality parameters, fluorescence components and indices
参数 DO COD [NH3−N] TN TP N/P 蓝绿藻 Chla FI BIX HIX FC1 −0.115 −0.156 0.220 −0.133 0.056 −0.272 −0.007 −0.262 −0.527* −0.913** 0.761** FC2 −0.262 0.265 −0.060 0.346 0.001 0.197 −0.061 0.293 −0.452* −0.575** 0.224 FC3 0.354 −0.036 −0.022 0.138 0.265 0.153 0.392 0.224 0.114 0.021 −0.408 C1% −0.140 −0.213 0.228 −0.476* −0.136 −0.569** −0.176 −0.220 −0.341 −0.699** 0.934** C2% −0.313 0.297 −0.112 0.275 −0.132 0.170 −0.155 −0.302 −0.393 −0.410 0.212 C3% 0.333 −0.078 −0.073 0.120 0.193 0.263 0.238 0.380 0.531* 0.791** −0.803** 注:**表示0.01级别,相关性极显著;*表示0.05级别,相关性显著。 -
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