崇明岛富营养化河道溶解有机质的三维荧光光谱特征

Three-Dimensional Fluorescence Spectra of Dissolved Organic Matter in a Eutrophic River on Chongming Island

在掌握崇明岛典型富营养化河道—北横引河水体富营养化特征的基础上,结合三维荧光光谱技术与平行因子分析法,探究北横引河溶解有机质(Dissolved organic matter, DOM)荧光特征及其变化规律,揭示其富营养化进程中不同来源DOM的响应机制。结果表明,北横引河水体中营养盐水平较高,旱季和雨季营养状态指数(TSI_M)均值分别为(60.18±3.01)和(65.53±5.72),达到富营养状态和重富营养状态;水体中主要存在3个DOM荧光组分,包括2个类腐殖质组分(C1、C2)和1个类蛋白组分(C3);各组分含量都随着河道营养水平的提高而增加,其中微生物代谢降解来源C1组分比例的提升最为明显,雨季和旱季的C1组分占比分别由19.39%和25.70%提高至32.90%和34.40%;对DOM来源进行解析发现,旱季和雨季北横引河的腐殖化指数均值分别为(4.41±0.35)和(5.76±0.95),DOM荧光特征均以生物来源为主,且随着水体富营养化水平的提高,其生物来源特征逐渐增强。DOM组分与理化因子和营养状态的相关性分析结果显示,藻类的生长和降解过程与类腐殖质组分的生产和输入密切相关,腐殖质组分对营养状态变化的响应程度高于类蛋白组分;而河道中类蛋白组分的含量变化则主要受到了周边各类污水输入的影响。

Chongming Island is located in the Yangtze River estuary of Shanghai and is the third largest island in China.In recent years,eutrophication of rivers on Chongming Island has been reported and the primary contributors are high nutrient inputs and sluice-control of the river network.Beihengyin River is on the north side of Chongming Island and,based on its eutrophication characteristics,we investigated the fluorescence characteristics and spatio-temporal variation of dissolved organic matter(DOM)using a combination of three-dimensional fluorescence spectroscopy and factor analysis.The objective was to characterize DOM from different sources and investigate the effect of eutrophication on DOM dynamics.Fourteen sampling sites(B1 to B14)were established,from west to east,beginning at the Chongxi sluice(B1)in Beihengyin River.Water samples were collected at 0.5 m below the surface in January and August 2010 and analyzed for TN,TP,CODMn,NH3-N,Chl-a and the DOM fluorescence spectrum.The nutrient concentrations in Beihengyin River were high,with trophic state index(TSI)values of(60.18±3.01)(eutrophic)in dry season and(65.53±5.72)(highly eutrophic)in wet season.The fluorescence spectrum of DOM indicated three components,two humic-like substances(C1,C2)and one protein-like substance(C3).The concentration of all components and the trophic state index increased from B1 to B14 and C1,derived from biodegradation and metabolism,increased significantly.The proportion of C1 increased from 19.39%to 32.90%in wet season and from 25.70%to 34.40%in dry season.Source analysis of DOM gave mean humification index(HIX)values of(4.41±0.35)in dry season and(5.76±0.95)in wet season.DOM fluorescence characteristics indicated a biological source that intensified as TSI increased.Correlation analysis between DOM components and physical-chemical parameters showed that production and degradation of algae were closely associated with the humic-like substances and the protein-like substances were associated with inputs of domestic wastewater.This characterization of DOM and the influence of eutrophication on DOM dynamics support efforts to protect water quality in the rivers of Chongming Island.