古运河局部河段水质时间变化特性——以运河三湾风景区河段为例

Temporal Change Characteristics of Water Quality in a Designated Reach of the Ancient Canal

为揭示扬州城区古运河三湾风景区河段的水质时间变化特性,自2018年10月至2019年6月,选取该河段的上下游两个断面及支流入口断面对其水质参数水温(WT)、pH、电导率(EC)和溶解氧浓度(DO)以及NH4+浓度进行观测,采用变异系数法、单因子水质标识指数法与多元线性回归法分析水质参数的时间变化特性,并构建NH4+浓度随流分散模型对河段NH4+的运移过程进行模拟。结果表明:研究期间内,各断面的WT呈季节性变化;2019年4月之前pH与EC呈上升趋势,之后pH与EC有所下降;大部分时段支流同期的DO低于干流,EC高于干流;各水质参数的总变异系数与权重从大到小依次为DO 】WT 】EC 】pH;下游断面以DO为指标的水质类别受支流排水影响较大,水质劣于上游断面,支流断面的pH与水质标识指数变化随机性较强;多元线性回归分析结果表明:DO与WT、pH均呈负相关,且pH的变化对DO的影响比WT更大;NH4+随流分散模型的模拟结果显示,当WT较低且变化较小时,模型的模拟精度较高,单日河段上游NH4+浓度逐渐降低,下游逐渐增大,各断面的NH4+浓度逐渐趋于同一水平。

The main objective of the current research is to reveal the temporal change characteristics of water quality for a designated reach of the Sanwan Scenic Area of Ancient Canal in Yangzhou City. The observation of the water quality parameters such as water temperature (WT), pH, electrical con-ductivity (EC), dissolved oxygen (DO), and concentration of NH4+ had been carried out on the two sections of the main stream and two tributary inflow sections in the period from October 2018 to May 2019. Coefficient of variation method, single factor water quality index method and multiple linear regression method were adopted for data analysis. A flow-following dispersion model for NH4+ calculation was developed and simulation for concentration of NH4+ changed process was carried out in the designated reach. The result indicates that during the study period, the WT sea-sonally changed in each section;the pH and EC represented an upward trend before April 2019 and then decreased;the DO in the tributaries was lower than that in the main stream, but the EC was higher than main stream;the order of the variability and weight coefficient of water quality parameters was DO >WT >EC >pH;the single factor water quality identification index of DO in the downstream was significantly affected by the sewage discharge from the tributaries, the pH and single factor water quality identification index in the tributaries changed randomly. According to results of the multiple linear regression analysis, DO is negatively correlated with WT and pH, the effect of pH change on DO is greater than that of WT;a proper simulation result is achieved for the concentration of NH4+ simulation by using the developed numerical model, and the concentration of NH4+ in the upstream sections decreases gradually, but increases in the downstream sections, the concentration of NH4+ in each section approaches the same level gradually.