南水北调中线总干渠典型渠段水体自净能力研究

Studyon water self-purification capacityin a typical section of middle route in the main channel of South-to-North Water Transfer Project

水体自净能力是影响水质指标变化的重要因素。以BOD5降解系数作为自净能力表征,选取南水北调中线总干渠河南段程沟、方城、沙河南、兰河北、新峰、苏张等6个监测断面2015年1月至2015年7月逐月BOD5监测数据和研究渠段各节制闸的流量、水深等数据,采用稳态一维BOD5降解模型对总干渠BOD5降解系数进行拟合。结果表明,研究渠段BOD5降解系数数值范围为0.024/d^0.054/d,与其他区域相比,总干渠的水体自净能力相对较小。研究渠段BOD5降解系数季节变化明显,1月-4月、7月的拟合k值分别为0.028/d(p<0.05),0.033/d(p<0.05),0.024/d(p<0.05),0.039/d(p<0.05),0.054/d(p<0.05);但5月、6月的拟合k值均不具有统计显著性(p>0.05),可能是由于桥面和路面降雨径流形成了外源有机物污染输入,造成渠道BOD5浓度波动较大。总干渠自净能力受温度影响显著,BOD5降解系数基本随温度的升高而增大,温度校正系数θ值为1.039。

Self-purification ability of the water body is an important factor affecting the change in water quality indicators.In this study,the self-purification capability was characterized by the BOD5 degradation coefficient.From January 2015 to July 2015,six monitoring sections(Chenggou,Fangcheng,Shahenan,Lanhebei,Xinfeng,and Suzhang)of the main canal in the middle route of the south to North Water Transfer Project were selected to monitor the BOD5 monthly data and to study the flow and water depth of each control gate in the canal section,the one-dimensional steady BOD5 degradation model was used to fit the BOD5 degradation coefficient of the main channel.The results showed that the degradation coefficients of BOD5 in the channel section between 0.024/d^0.054/d.The capacity of water self-purification of the main channel is relatively small compared to other areas.The seasonal change of the BOD5 degradation coefficient in the channel section was obvious.The fitting k values from January to April and July were 0.028/d(p<0.05),0.033/d(p<0.05),0.024/d(p<0.05),0.039/d(p<0.05),0.054/d(p<0.05),respectively.But the fitting k values of May and June were not statistically significant(p>0.05).The runoff from the bridge and the road formed the input of exogenous organic pollution may be the main cause behind this insignificant fluctuation of BOD5 concentration in the channel.The self-purification ability of the main channel was significantly affected by temperature.The degradation coefficient of BOD5 increased with the increase of temperature and the temperature correction coefficient was1.039,respectively.