湖泊科学   2019, Vol. 31 Issue (5): 1344-1356.  DOI: 10.18307/2019.0509.
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研究论文

引用本文 [复制中英文]

周石磊, 孙悦, 张艺冉, 战江, 王函, 黄廷林, 丛海兵, 崔建升, 李再兴, 山东省周村水库季节演替中沉积物上覆水溶解性有机物的紫外-可见与三维荧光光学特征. 湖泊科学, 2019, 31(5): 1344-1356. DOI: 10.18307/2019.0509.
[复制中文]
ZHOU Shilei, SUN Yue, ZHANG Yiran, ZHAN Jiang, WANG Han, HUANG Tinglin, CONG Haibing, CUI Jiansheng, LI Zaixing. Seasonal variations of ultraviolet-visible and excitation emission matrix spectroscopy characteristics of overlying water dissolved organic matter in Zhoucun Reservoir, Shandong Province. Journal of Lake Sciences, 2019, 31(5): 1344-1356. DOI: 10.18307/2019.0509.
[复制英文]

基金项目

国家自然科学基金项目(51478378)和河北科技大学引进人才科研启动基金项目(1181278)联合资助

作者简介

周石磊(1987~), 男, 讲师, E-mail:ZSLZhouShilei@126.com

通信作者

黄廷林, E-mail:huangtinglin@xauat.edu.cn

文章历史

2018-12-18 收稿
2019-03-06 收修改稿

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山东省周村水库季节演替中沉积物上覆水溶解性有机物的紫外-可见与三维荧光光学特征
周石磊1 , 孙悦1 , 张艺冉1 , 战江1 , 王函1 , 黄廷林2 , 丛海兵3 , 崔建升1 , 李再兴1     
(1: 河北科技大学环境科学与工程学院, 河北省污染防治生物技术实验室, 石家庄 050018)
(2: 西安建筑科技大学环境与市政工程学院, 西安 710055)
(3: 扬州大学环境科学与工程学院, 扬州 225009)
摘要:运用三维荧光光谱(EEMs)技术结合平行因子分析法(PARAFAC)以及紫外-可见光谱技术(UV-vis),对周村水库季节演替过程中沉积物上覆水溶解性有机物(DOM)的紫外-可见以及三维荧光光谱特征进行分析.结果表明:周村水库上覆水的总氮、溶解性总氮、总有机碳和溶解性有机碳的季节性差异显著,并且冬季总氮浓度最高、夏秋季总有机碳浓度较高;夏秋季上覆水DOM的吸收系数a254a355均高于冬春季,与有机物的分布相一致;4个季节上覆水DOM的E3/E4均大于3.5,说明DOM以富里酸为主,E2/E3(富里酸占DOM的比例)在夏秋季低于冬春季,而且各季节SR均大于1,表明DOM主要为生物源;三维荧光通过PARAFAC解析出3种组分:类腐殖质(C1)、可见区富里酸(C2)和类蛋白(C3);对3个组分进行相关性分析,结果显示C1、C2、C3之间具有显著的相关性;DOM的总荧光强度以及各组分的荧光强度均呈现出夏秋季高、冬春季低的特征,且各季节间差异显著;周村水库4个季节的DOM生物源指数(BIX)在0.8~1.0之间,表明水库DOM具有较强的自生源特征,与腐殖程度指标(HIX)的结果相吻合;主成分分析显示周村水库上覆水DOM的光谱特征差异明显,夏秋季的DOM光谱特征相近、冬春季的水体DOM特征相似;并且组分C1、C2、C3与DOM特征参数(a254、SUVA280HIXFIBIX)以及溶解性有机碳呈显著相关.各荧光组分与水质参数(溶解性总氮和溶解性有机碳)的多元线性回归呈现很好的拟合,通过建立回归方程可以为以后研究周村水库水体四季的DOM光谱特征,分析水库水体的有机物污染特征,并为水库水质管理提供技术支持.
关键词溶解有机质    周村水库    光谱特征    紫外-可见光谱    三维荧光光谱    
Seasonal variations of ultraviolet-visible and excitation emission matrix spectroscopy characteristics of overlying water dissolved organic matter in Zhoucun Reservoir, Shandong Province
ZHOU Shilei1 , SUN Yue1 , ZHANG Yiran1 , ZHAN Jiang1 , WANG Han1 , HUANG Tinglin2 , CONG Haibing3 , CUI Jiansheng1 , LI Zaixing1     
(1: Pollution Prevention Biotechnology Laboratory of Hebei Province, School of Environmental Science and Engineering, Hebei University of Science and Technology, Shijiazhuang 050018, P. R. China)
(2: School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, P. R. China)
(3: Department of Environmental Science and Engineering, Yangzhou University, Yangzhou 225009, P. R. China)
Abstract: Based on excitation emission matrix spectroscopy (EEMs) technology combined with the parallel factor analysis (PARAFAC), and UV-vis spectra, we analyzed the impact of seasonal variations on distribution and spectral characteristics of dissolved organic matter (DOM) in Zhoucun Reservoir. Results showed that the concentration of nitrogen and organic matter exhibited significant seasonal differences, and the reservoir has more total nitrogen and less total organic carbon in winter. The a254 and a355 in summer and autumn were both higher than those in winter and spring, which was consistent with the changes of organic matter. The E3/E4>3.5 showed that the fulvic acid accounted for the majority proportion in DOM; the concentrations of fulvic acid in summer and autumn were higher than those in winter and spring based on E2/E3. Moreover, the SR>1 indicated the DOM exhibited autochthonous characteristics. One humic-like substances (C1), one fulvic-like substances (C2) and one protein-like substance (C3) were identified by PARAFAC model, and there exhibited significantly correlation coefficient in C1 & C2 & C3; Total fluorescence intensity and the fluorescence intensity of each component exhibited high concentration for summer and autumn and low concentration for winter and spring distribution characteristics. Total fluorescence intensity and the fluorescence intensity of each component exhibited significant seasonal difference. The DOM exhibited strong autochthonous component characteristics based on BIX and HIX indexes; Principal component analysis showed that the spectral characteristics exhibited obvious difference in the whole year, and the DOM spectral characteristics of summer and autumn are similar, and the DOM characteristics of water in winter and spring are similar. Moreover, the C1, C2 and C3 exhibited significantly correlation coefficient with DOM indices (FI, β/α) and dissolved organic carbon. Those three components and water quality (dissolved total nitrogen and dissolved organic carbon) of overlying water could be connected with spectral characteristic by nonlinear multiple. From all the results, it could contribute to explore and control the organic carbon pollution sources for the managers of Zhoucun Reservoir in the future.
Keywords: Dissolved organic matter    Zhoucun Reservoir    spectral characteristic    UV-visible spectrum    excitation emission matrix spectroscopy (EEMs)    

溶解性有机质(DOM)主要包括亲水性有机酸、类蛋白、类氨基酸、类腐殖酸和碳水化合物等[1],含有丰富的碳、氮、磷等要素;DOM演变过程涉及到水体污染物质的转化,因此会对水体水质演变有重要影响[2];而且水厂在水处理过程中一些含氮DOM还会与消毒剂发生反应,产生消毒副产物,进而给水质安全带来潜在的危害[3-4].因此,近年来在天然环境水体中有关DOM组分、特性以及演变特征的研究成为热点[5].

紫外-可见以及三维荧光结合平行因子分析技术因其灵敏高效的特征,被广泛用于表征河流[6-7]、河口[8-9]、湖泊[10-11]、水库[12-15]和湿地[16]等不同来源DOM的组成和来源.然而,目前大多研究往往集中于某一特定时期或特定区域的DOM光谱特征解析.比如:乔煜琦等[17]利用平行因子分析(PARAFAC)技术对藻华暴发季节太湖梅梁湾和开敞区水样中有色可溶性有机物进行三维荧光光谱分析,发现藻华的长期暴发可以显著改变湖泊有色可溶性有机物(CDOM)的组成,导致类腐殖酸物质比例提高;聂明华等[18]利用三维荧光光谱技术,结合平行因子分析法及自组织映射神经网络,对南昌市典型湖泊水体中不同粒径胶体的荧光物质组分、来源及结构等进行分析;张博等[19]采用化学连续提取与三维荧光光谱相结合的方法研究了蠡湖沉积物中可提取有机质的组成、结构和空间分布特征,并探讨了可提取态有机质组分与可交换态氮和弱吸附态磷之间的相关关系;文杨等[20]以沈阳市新开河为研究对象, 考察了冰封期前、后河流底泥中DOM组分荧光特性的变化.但是,关于水库季节演替中沉积物上覆水DOM光谱特征的研究却鲜有报道.

众所周知,水库不同于一般的天然水体,因其作为城市的供水水源,担负着保障城市供水水质安全的重任,其水质安全影响人民的切身利益[21-22].众所周知,水库沉积物上覆水作为水库沉积物和水体交换的活跃地带,其水体的水质特征在水库碳、氮、磷等元素的循环中扮演重要角色;加之水库水体存在热分层现象,使沉积物上覆水的DOM变化特征更不同于一般的水体.因此,在季节演变的时间尺度下开展周村水库沉积物上覆水平面空间的DOM光谱解析十分必要.基于此,本研究利用紫外-可见吸收光谱以及三维荧光光谱分析技术,分析2015-2016年四季演替过程中周村水库沉积物上覆水水体的DOM组成和光谱特征.旨在通过该研究,了解沉积物上覆水DOM的结构、来源以及对其生态环境效应的影响,以期为周村水库水体水质污染防治以及运行管理提供必要的科学依据.

1 材料与方法 1.1 采样地点和时间

周村水库位于山东省枣庄市孟庄镇周村南,总库容8404万m3,是枣庄市主要的城市供水水源地.本研究选取2015年的9月(秋季)、12月(冬季),2016年的3月(春季)、6月(夏季)周村水库24个点位的沉积物上覆水为研究对象,采样点分布如图 1所示.

图 1 周村水库沉积物上覆水采样点分布 Fig.1 Location of overlying water sampling sites in Zhoucun Reservoir
1.2 样品提取及测定

将收集到的沉积物上覆水水样用0.45 μm玻璃纤维滤膜(预先450℃灼烧5 h)过滤得到溶解性有机物水体样品,并保存在4℃的冰箱内,在72 h之内完成DOM的光谱分析. 24 h内完成水样中溶解性总氮(DTN)、总氮(TN)、总有机碳(TOC)和溶解性有机碳的测定,其中DTN和TN浓度依据《水和废水监测分析方法》测定[23],TOC和溶解性有机碳浓度用有机碳分析仪测定[24].

1.3 紫外-可见吸收光谱的测定

紫外-可见光谱采用DR6000分光光度计(美国HACH公司)测定,以Mill-Q水为空白,用1 cm石英比色皿,以1 nm为扫描间隔,在200~700 nm范围内进行吸光度测定.吸收系数计算公式为[25-26]

$ {a^*}(\lambda ) = 2.303D(\lambda )/r $ (1)
$ a(\lambda ) = {a^*}(\lambda ) - {a^*}(700) \cdot \lambda /700 $ (2)
$ a(\lambda ) = a(440)\exp [S(440 - \lambda )] $ (3)

式中,λ为波长,nm;a*(λ)为未经散射校正的波长为λ处的吸收系数,m-1a(λ)为经过散射校正过后的波长为λ处的吸收系数,m-1D(λ)为波长λ处的吸光度;r为光程路径,m.本文选取a254a355来表示DOM的相对浓度. SR为光谱斜率比,为S275-295/S350-400.与a*(λ)相比,SR更能反映出DOM的来源与分子量信息[27]. E2/E3是250 nm和365 nm处的紫外吸光度之比,其值与相对分子质量大小呈反比[28-29]. E3/E4是300 nm和400 nm处的紫外吸光度之比,用来衡量腐殖质的腐殖化程度和芳香性. SUVA260(a260/DOC)[27]用来表征DOM疏水组分的含量,SUVA280(a280/DOC)[30]用来表征DOM芳香性的强弱.

1.4 三维荧光光谱的测定

三维荧光光谱采用F97荧光分光光度计进行测定.设备的激发波长、发射波长以及扫描速度等参数设置同黄廷林等[13]的研究.利用超纯水做空白扣除散射影响,并结合Delaunnay三角形内插值法修正去除拉曼峰散射和瑞利散射[31].利用MATLAB 2014a软件把96个样品的荧光矩阵组合, 采用N-way和DOMFluor工具箱进行平行因子分析[32],并通过核一致性分析确定荧光组分数,利用折半分析来分析结果的可靠性[33].

1.5 三维荧光光谱的特征指数

荧光指数(FI=F470/F520)可以评价有机质来源和降解程度,计算方法见文献[34-35];腐殖程度指标HIX[36]为254 nm激光波长下435~480 nm间荧光峰值与300~345 nm间荧光峰值积分值之商(F435~480/F300~345),HIX指数越高则表示DOM腐殖化程度越高[37];生物源指数指标(BIX=F380/F430)反映有机质自生源相对贡献率,同时可以评价生物可利用性的高低[38];新鲜度指数(β :α)为激发波长为310 nm时荧光发射波长在380 nm处荧光强度与荧光发射波长在420~435 nm区间最大荧光强度的比值,是评估水体生物活性的重要依据.

1.6 数据分析

实验数据采用SPSS (22.0)软件进行Pearson相关性分析和单因素方差分析.应用Surfer (12.0)软件进行水库沉积物上覆水水体水质及荧光强度分布的绘制.

2 结果与讨论 2.1 水库沉积物上覆水中氮和有机碳的分布特征

夏、秋季周村水库大部分区域沉积物上覆水水体的溶解性有机碳浓度要低于冬、春季(图 2),并且各季节间均呈显著差异(P < 0.01),最高值出现在夏季(3.16±0.42 mg/L)(图 2d),最小值出现在春季(1.27±0.31 mg/L)(图 2c).而且靠近入库支流(西北部)和库湾的部分浓度相对较高.周村水库中沉积物上覆水中TN(图 3a)和DTN(图 3b)浓度均在冬季出现最高值,并且与其他各季节呈显著差异(P < 0.001).沉积物上覆水中TOC浓度的最大值出现在秋季(4.49±1.41 mg/L),最小值出现在春季(1.80±0.32 mg/L),并且与其他各季节呈显著差异(P < 0.001) (图 3c).

图 2 周村水库不同季节溶解性有机碳(DOC)的分布特征 Fig.2 Characteristics of distribution of dissolved organic carbon(DOC) in Zhoucun Reservoir in different seasons
图 3 周村水库不同季节总氮、溶解性总氮和总有机碳的分布特征 Fig.3 Characteristics of distribution of TN, DTN and TOC in Zhoucun Reservoir in different seasons
2.2 紫外-可见吸收光谱特征参数分析

本研究用a254a355表示DOM的相对浓度,夏、秋季水库水体的a254a355明显高于冬、春季(图 4ab),与溶解性有机碳的分布特征相一致,并且各季节间的a254a355呈显著差异(P < 0.001).有研究表明[29, 39]SR>1时,表征DOM主要为生物源;SR < 1时,表征DOM主要为外源.本研究中上覆水的SR值为1.09~1.30,但是4个季节的SR值均大于1(图 4c),表明该时期间隙水中的DOM主要是生物源.

图 4 周村水库上覆水水体DOM的a254a355SR(* * *表示P < 0.001) Fig.4 The a254, a355 and SR values of DOM in overlying water of Zhoucun Reservoir

冬、春季周村水库上覆水DOM的E2/E3值较大,夏、秋季分布较集中;各季节间E2/E3呈显著差异(图 5a);从整体上看,冬、春季上覆水中的富里酸占比较大.一般而言,当E3/E4 < 3.5时腐殖质以腐殖酸为主,E3/E4>3.5时以富里酸为主.本研究中E3/E4的均值均大于3.5(图 5b),说明水库上覆水中DOM以富里酸为主;冬、春季上覆水的E3/E4比夏、秋季高,表明夏、秋季的腐殖化程度较高;冬季上覆水的E3/E4与春、夏、秋季呈显著差异(图 5b).

图 5 周村水库上覆水DOM的E2/E3、E3/E4、SUVA260和SUVA280 (* * *表示P < 0.001, * *表示P < 0.01, *表示P < 0.05) Fig.5 E2/E3, E3/E4, SUVA260 and SUVA280 values of overlying water DOM in Zhoucun Reservoir

春季上覆水DOM的SUVA260最高(图 5c),表明春季样品的疏水性组分最高;春季SUVA280同样是最高的,其次依次为夏季、冬季和秋季,表明芳香化程度逐渐减弱(图 5d);各季节上覆水DOM的SUVA260和SUVA280呈显著正相关(P < 0.01),相关系数达到0.911,表明疏水性和芳香性结构关系密切,即芳香性结构主要存在于疏水组分中,与高洁等[27]研究三峡库区DOM的结论相一致.

2.3 沉积物上覆水的DOM三维荧光光谱及荧光组分分析 2.3.1 沉积物上覆水DOM的三维荧光光谱

为考察水库沉积物上覆水DOM的分布特征和组成情况,选取了水库主库区22#采样点4个季节的样品进行了三维荧光扫描(图 6), 可以看出,主库区秋季荧光峰有3个:长波类腐殖质(Ex/Em=355 nm/460 nm)、富里酸峰(Ex/Em=340 nm/415 nm)和类蛋白峰(Ex/Em=280 nm/315 nm).但是随着季节的演替峰的强弱发生变化,不同季节间差异明显,因此,很有必要进一步分析其变化原因.

图 6 周村水库主库区不同季节水体的三维荧光光谱 Fig.6 EEM spectra of DOM in the main area of Zhoucun Reservoir in different seasons
2.3.2 沉积物上覆水DOM的荧光组分分析

通过平行因子分析对四季水体样品进行三维荧光解析,分析DOM的成分构成.因为PARAFAC对组分数很敏感,只有选择正确的组分数目,解析的结果才能反映真实的谱图.从图 7可以看到,荧光组分从2变为3时,核一致函数值急剧变小,而组分从3变成4时,核一致函数值变化程度减弱,初步确定成分F=3最合适.与此同时,组分为3时核一致性系数为75.88 %,位于80 %附近,并且处于急剧下降段,因此建立因子数为3的PARAFAC模型.与乔煜琦等[17]解析太湖溶解性有机物荧光组分的分析相一致.

图 7 周村水库水体荧光组分的核一致性检验 Fig.7 Core consistency of EEM samples in Zhoucun Reservoir

周村水库四季沉积物上覆水DOM的荧光光谱图如图 8所示,共解析得到3种组分,类腐殖质(C1)、类富里酸(C2)以及类蛋白(C3).结合前人研究成果(表 1),综合分析得到:C1的荧光峰位置是355 nm/460 nm (Ex/Em),为长波类腐殖质(C峰);C2的荧光峰位置是340 nm/415 nm (Ex/Em),为长波类可见区富里酸;C3的荧光峰位置是280 nm/315 nm (Ex/Em),为类色氨酸.

图 8 PARAFAC解析出的DOM中3个荧光组分及其激发发射波长位置 Fig.8 Fluorescence spectra of three components identified by PARAFAC model
表 1 周村水库沉积物上覆水DOM的荧光组分特征 Tab. 1 Characteristics of components in overlying water of Zhoucun Reservoir
2.3.3 DOM的荧光组分强度及分布特征

周村水库沉积物上覆水水体总荧光强度和各组分的荧光强度呈现夏秋季高于冬春季的特征(图 9),并且各季节间均呈现显著差异(P < 0.01).就荧光组分类腐殖质(C1)而言,夏季水库上覆水的荧光强度最大,为885.43±93.72 A.U.,最小值为春季的398.32±24.86 A.U.,夏季的C1荧光强度约为春季的2.22倍,可能与夏季底层沉积物释放以及径流输入有关;就荧光组分富里酸(C2)而言,秋季水库上覆水样品的荧光强度最大,为701.97±17.74 A.U.,最小值为春季的359.11±36.84 A.U., 秋季的C2荧光强度约为春季的1.95倍;就荧光组分类蛋白(C3)而言,夏季水库底层上覆水水体样品的荧光强度最大,达到661.47±44.21 A.U.,最小值为春季的342.26±57.27 A.U.,夏季的C3荧光强度约为春季的1.93倍;总荧光强度最高的为夏季,达到2204.81±157.52 A.U.,最低的为春季的1099.69±112.97 A.U.,夏季的总荧光强度约为春季的2倍.经平行因子分析得到的3种荧光组分中,各个荧光组分在同一季节的相对含量差异不大,夏、秋季的C1在DOM总荧光强度中的占比达到38.69 % ~40.07 %,高于冬、春季的36.42 % ~36.64 %;冬季C2在总荧光强度的占比最大,达到38.51 % ±1.03 %,远高于夏季的29.78 % ±1.63 %;夏季的C3在DOM总荧光强度中的占比达到30.14 % ±2.82 %,高于冬季的24.85 % ±1.22 %.

图 9 周村水库沉积物上覆水DOM组分荧光强度的季节变化 Fig.9 Seasonal variations of fluorescence intensity of DOM in overlying water of Zhoucun Reservoir

Pearson相关性分析表明,周村水库沉积物上覆水DOM中类腐殖质(C1)与可见光区富里酸(C2)以及类蛋白(C3)两两间存在显著正相关性(表 2),表明3种组分具有同源性.其中组分C1与组分C2的相关系数最高,达到0.940(P < 0.01),预示着C1与C2来源及物质组分有着较高的相似性.

表 2 周村水库沉积物上覆水DOM中3个荧光组分的Pearson相关性 Tab. 2 Pearson correlation of three components of DOM in overlying water of Zhoucun Reservoir
2.4 DOM的荧光特征参数分析

Huguet等[38]指出BIX在0.7~0.8之间时,具有中度新近自生源特征;BIX在0.8~1.0之间时,具有较强的自生源特征;BIX大于1.0时,为生物活动产生.本实验中BIX在0.8~1.0之间(图 10a),表明周村水库各季节的DOM呈现较强的自生源特征. Lavonen等[35]提出FI可以作为物质的来源以及DOM降解程度的指示指标,FI>1.8表示以自生源为主,FI < 1.2表示以陆源输入为主.冬、春、夏、秋季周村水库上覆水DOM的FI分别为1.87±0.05、1.76±0.06、1.63±0.04和1.72±0.04,冬季最高,表明冬季呈现自生源为主的特征,这与冬季水库径流少、外源输入贡献量低相一致,并且与张博等[46]研究发现太湖五里湖水体悬浮物中水溶性有机质FI均值为1.83、生物源大于陆源输入的结论相一致.

图 10 周村水库不同季节沉积物上覆水中DOM的FI-BIXFI-HIXFI-β :α分布 Fig.10 FI-BIX, FI-HIX, and FI-β:α distributions of DOM in overlying water of Zhoucun Reservoir in different seasons

Huguet等[38]指出4<HIX < 6代表弱腐殖化特征及较强的自生源特征;HIX < 4表示以自生源为主.本研究中周村水库沉积物上覆水DOM的HIX指数都小于4(图 10b),并且春、夏季水体HIX指数要低于秋、冬季;表明春、夏季沉积物上覆水DOM的自生源特征更明显,与BIX指数以及紫外-可见吸收光谱SR的结论非常吻合;与张海威等[47]研究得到的新疆艾比湖入湖河流DOM的HIX < 4,主要受到人类活动和微生物活动影响的结果相一致.不同季节间HIX的差异显著(P < 0.001),表明不同季节沉积物上覆水的DOM来源存在差异.新鲜度指数(β :α)反映了新产生的DOM在整体DOM中所占的比例,是评估水体生物活性的重要依据.周村水库β :α分布在0.80~1.05之间(图 10c),除春、秋季以及秋、冬季样品的β :α不存在显著差异(P>0.05)外,其他各季节间均存在显著差异(P < 0.01).

2.5 DOM的荧光组分与环境因子的相关分析

为了进一步研究周村水库四季演变过程中DOM荧光组分和环境因子的关系,本研究进行了主成分分析(PCA)和Pearson相关性分析. PCA分析结果(图 11)表明,PC1和PC2分别解释了71.27 %和13.72 %,总共解释84.99 %的变化,PCA分析都能够很好地反映总体的变化.同一季节的水体样本点分布相对集中,不同季节间分布差异明显;冬、春季的样本点位于PCA1的正半轴,而夏、秋季的样本点位于PCA1的负半轴. a254a355HIX和DOC与C1、C2、C3呈正相关,DTN、FIBIXβ :α、SUVA260以及SUVA280与C1、C2、C3呈负相关.综上,可以侧面解释周村水库不同季节沉积物上覆水水体DOM组分和特征差异.

图 11 周村水库不同季节沉积物上覆水DOM特征及水质参数的主成分分析 Fig.11 Principal component analysis DOM and water quality parameters in overlying water of Zhoucun Reservoir in different seasons

从周村水库4个季节上覆水水体样品的3个荧光组分与DOM特征参数以及水质参数的相关性(表 3)可以看出,腐殖质组分C1与a254a355、SUVA260、SUVA280FIBIXβ :α、DTN以及DOC呈显著相关(P < 0.01);富里酸组分C2与a254a355、SUVA260、SUVA280BIXβ :α(P < 0.05)、HIX以及DOC呈显著相关(P < 0.01);类蛋白C3与a254a355、SUVA260、SUVA280FIBIXβ :αHIX、DTN以及DOC呈显著相关(P < 0.01).同时基于主要的相关性指标(R2>0.5)对荧光组分(C1、C2、C3)和水质指标(DTN和DOC)进行了多元线性回归,结果显示多元线性回归拟合的方程很好(表 4),将来可以通过水体的DOM特征参数和水质参数对水体DOM组分以及水质进行分析,有利于评估季节演变过程中溶解性有机物以及水质的特征,便于水库管理人员对有机污染物和水质进行评价.

表 3 周村水库沉积物上覆水水体中3个荧光组分与特征参数及水质的相关性 Tab. 3 Correlation analysis of DOM indices-water quality parameters and three fluorescence components of overlying water in Zhoucun Reservoir
表 4 荧光组分与特征参数及水质多元线性回归 Tab. 4 Multiple linear regression for DOM indices-water quality parameters and fluorescence components
3 结论

1) 紫外-可见光谱特征显示夏、秋季周村水库上覆水DOM的吸收系数a254a355均高于冬、春季,与有机物的分布相一致;全年上覆水DOM以富里酸为主,主要表现为生物源;SUVA260和SUVA280呈显著正相关(P < 0.01),表明水体样品中DOM的芳香性结构主要存在于疏水组分中.

2) 三维荧光光谱解析得到类腐殖质(C1)、富里酸(C2)和类蛋白(C3)各1种. 3种荧光组分具有显著的相关性(P < 0.01);DOM总荧光强度以及各组分荧光强度存在显著的季节性差异(P < 0.001);结合三维荧光特征指数FIBIX以及HIX得到周村水库上覆水水体DOM具有以自生源为主、低腐殖化的特点.

3) PCA分析显示周村水库沉积物上覆水DOM荧光特征季节差异明显,并且组分C1、C2和C3与DOM特征参数(a254、SUVA280HIXFIBIX)以及水质参数(DOC)存在显著相关性(P < 0.01);多元线性回归分析能够很好地预测荧光组分和水质(DTN和DOC)的变化.

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