基坑排水对城市内河水体溶解性有机质的影响研究

工程施工时基坑排水是保障基坑安全的必要措施，排出水进入城市内河，对内河及下游水生态安全产生影响。该研究采集哈尔滨市何家沟欧亚之窗公园段建筑工程施工过程中基坑排出水(W1)、排水口上游100 m处(W2)、排水口处(W3)、排水口下游50 m处(W4)、排水口下游100 m处(W5)、排水口下游200 m处(W6)的水体样品，应用三维荧光光谱-平行因子分析方法，测定溶解性有机质(DOM)的荧光光谱特征，分析DOM的组成和来源，探究基坑排水对城市内河水体环境的影响。结果表明：内河水体腐殖化指数(HIX)在0.337~0.381范围内，腐殖化程度低，W1，W3～W6的HIX差异不显著，均显著低于W2，说明排水进一步降低了内河水体腐殖化程度。荧光指数(FI₃₇₀)介于2.330~2.900范围内，生物指数(BIX)在0.897~1.140范围内，W1和W2的FI₃₇₀和BIX均显著高于W3~W6，两者具有极强的自生源特征，说明排水使下游水体自生源特征降低。水体样品DOM中共识别出2类4种有机组分：可见类富里酸组分(C1)、类色氨酸组分(C2)、紫外类富里酸组分(C3)和类酪氨酸组分(C4)，即类富里酸物质(C1、C3)和类蛋白物质(C2、C4)，两者间成负相关关系。FI₃₇₀与4种有机组分间均呈极显著的相关性，说明DOM组成简单。W2具有相对较高的DOM浓度，而排水口下游水体DOM浓度低，基本保持稳定。类蛋白物质在上游水体中占有相对较高的比重，在W4中，4种有机组分相对比重差异不显著，W5和W6类富里酸物质的相对比重有升高趋势，同样说明基坑排水导致内河水体自生源特征降低。除pH值升高外，下游水体样品溶解氧(DO)、总氮、总磷等理化指标含量均降低，pH值与类富里酸物质呈正相关，与类蛋白物质呈负相关，而DO、化学需氧量及水体养分指标与之相反。水体DOM有机组分与理化指标的相关性不同，可直接或间接影响DOM组成。因此，工程施工基坑排水可降低城市内河水体DOM浓度，改变了水体DOM组成。

Study on the Effect of Foundation Pit Drainage on Water Dissolved Organic Matter in Urban River

In engineering construction, foundation pit drainage is a necessary measure to ensure the safety of the foundation pit. The water discharged into the urban inland river impacts the ecological safety of the inland rivers and downstream water. In this study, the drainage water from the foundation pit (W1), 100 m upstream of the drainage outlet (W2), the drainage outlet (W3), 50 m downstream of the drainage outlet (W4), 100 m downstream of the drainage outlet (W5) and 200 m downstream of the drainage outlet (W6) were collected in the process of construction in Eurasian Window Park reach of Hejia river, Harbin city. Three-dimensional fluorescence spectrum - parallel factor analysis method was used to determine the fluorescence spectrum characteristics of dissolved organic matter (DOM), analyze the composition and source of DOM, and explore the impact of foundation pit drainage on the urban inland water environment. The results showed that the humification index (HIX) of inland water was in the range of 0.337~0.381, and the humification degree was low. There was no significant difference in the HIX of W1, W3~W6, which was significantly lower than W2, indicating that drainage further reduced the humification degree of inland water. The fluorescence index (FI₃₇₀) was in the range of 2.330~2.900, and the biological index (BIX) was 0.897~1.140. The FI₃₇₀ and BIX of W1 and W2 were significantly higher than those of W3~W6.Both of them had strong autochthonous characteristics, which indicated that the drainage reduced the autochthonous characteristics of the downstream water. The water DOM identified two types of four organic components: visible fulvic-like component (C1), tryptophan-like component (C2), ultraviolet fulvic-like component (C3) and tyrosine-like component (C4), namely fulvic-like substance (C1, C3) and protein-like substance (C2, C4). There was a negative correlation between the two types of substance. The correlation between FI₃₇₀ and four organic components was very significant, indicating that DOM’s composition was simple. W2 had a relatively high DOM concentration, while the DOM concentration downstream of the outlet was low and stable. Protein-like substances occupied a relatively high proportion in the upstream water. In W4, there was no significant difference in the relative proportion of the four organic components. In W5 and W6, the relative proportion of fulvic-like substance increased later, which also indicated that the drainage of the foundation pit led to the decrease in the autochthonous characteristics of inland water. Except for the increase in pH value, the contents of dissolved oxygen (DO), total N, total P and other physicochemical indexes of downstream water samples decreased. pH value was positively correlated with fulvic-like substance and negatively correlated with protein-like substance, while DO, chemical oxygen demand and water nutrient indexes were contrary. The correlation between water DOM components and physicochemical indexes was different, directly or indirectly affecting the DOM composition. Therefore, in engineering construction, the drainage of the foundation pit reduced the DOM concentration and changed the DOM composition of urban inland water.