不同面源强度影响下城市河流溶解性有机质光谱特征变化

Spectral Characteristics Change in Dissolved Organic Matter in Urban River Under the Influences of Different Intensities of Non-point Source Pollution

采用紫外-可见吸收光谱(UV-vis)和三维荧光光谱结合平行因子法(EEMs-PARAFAC)研究两条面源输入强度不同的城市河流春夏两季水体中溶解性有机质(DOM)含量和组成变化.结果表明,两条河流夏季水体DOM腐殖化程度和相对分子质量均显著高于春季(P<0.01).PARAFAC模型共解析出C1(UVC类富里酸)、C2(类色氨酸)、C3(类胡敏酸)和C4(UVA类富里酸)这4个化学组分,C1[(31±6)%]和C2[(31±4)%]为水体DOM中主要荧光组分.高面源输入水平的河流春季各组分荧光强度均低于夏季,而低面源输入水平的河流与之相反.随机森林回归模型表明,C3%对河流水质变化敏感度最高(R^(2)=0.75,P<0.001),具有很好的指示作用;水面覆盖率(Cover)对C4%有显著预测重要性(P<0.001),C4%易受光化学氧化作用影响.主成分分析(PCA)和Adonis检验表明,氮和磷为水体自生源过程的重要推动力,面源输入强度和季节变化对城市河流水体状况有显著影响(R^(2)=0.775,P<0.001).城市河流水体DOM处于动态变化中,其含量和构成受多重因素综合影响,陆地面源输入在提升类腐殖质输入水平的同时也促进了水体自生源过程.

With the method of ultraviolet-visible absorption spectroscopy(UV-vis)and excitation-emission matrix spectroscopy combined with parallel factor analysis(EEMs?PARAFAC),this study analyzed the change in dissolved organic matter(DOM)content and composition in spring and summer of two non-point source urban rivers which had different input intensities.The results indicated that the level of humification and molecular weight of DOM in summer was significantly higher than that in spring in these two rivers(P<0.01).The PARAFAC model was used to analyze four chemical compositions,including C1(UVC fulvic-like),C2(tryptophan-like),C3(humic-like),and C4(UVA fulvic-like);furthermore,C1[(31±6)%]and C2[(31±4)%]were the main fluorescent contents of the water.The high non-point source input river had a higher fluorescence intensity of all four PARAFAC components in spring than in summer,contrary to the low non-point source input river.The random forest regression model showed that C3%had the highest sensitivity to the changes in water parameters(R2=0.75,P<0.001)and could be an effective indicator.Additionally,the coverage level of the water surface(Cover)had an essential effect on the prediction of C4%(P<0.001),and C4%was susceptible to photochemical oxidation.According to the principal component analysis(PCA)and Adonis test,nitrogen and phosphorus were the essential impetuses for the biological process of the river;non-point source inputs and seasonal changes had a significant impact on the urban river(R^(2)=0.775,P<0.001).The contents and compositions of urban river DOM were affected by many essential factors.Non-point source inputs improved the input level of terrestrial humus in the water and promoted the biological process at the same time,dynamically contributing to the changes in the DOM of the water body.