基于Logistic回归模型的低溶解氧风险因素与成因分析——以釜溪河(自贡段)为例

Risk Factors and Causes of Low Dissovled Oxygen Based on Logistic Regression Model-Taking Fuxi River(Zigong section)as an Example

釜溪河(自贡段)国控碳研所断面在春末及夏季容易发生季节性低DO现象。采用Logistic回归模型分析2017~2018年水质、水文、气象三方面条件,识别釜溪河国控碳研所断面发生低DO的危险因素,分析低DO成因。研究表明:(1)TP≥0.2mg/L、TN≥6.4mg/L、AT≥14.2℃、DI≤0.3 m3/s是碳研所断面发生低DO的危险因素,其中,较高的AT是首要危险因素,较高的TP和TN是重要危险因素,较低的DI增加了河道DO消耗。(2)低DO成因一方面由于气温升高,水体饱和溶解浓度下降。但更主要的是由于水体TP、TN浓度较高,随着气温升高,藻类大量繁殖,消耗河道DO。枯平水期河道低流量有利于藻类聚集增殖,增加了DO消耗。(3)恢复河道DO可以从控制TP、TN浓度,提高河道流量、流速着手。本文为河流低DO危险因素及成因研究提供新的方法,为釜溪河(自贡段)及我省重点小流域生态修复、恢复水体DO提出可行路径。

The concentration of dissolved oxygen is an important indicators of water quality and water ecosystem health.Deficiency of dissolved oxygen always occurs in late spring and summer in Fuxi River,Zigong City.Based on Logistic Regression Model,this paper analyzed the water quality,hydrologic condition and meteorological conditions from 2017 to 2018,identify the risk factors of low dissolved oxygen in the national control section Tanyansuo of Fuxi River from 2017 to 2018,and discussed the causes of low DO.The results showed that:(1)Total phosphorus≥0.2 mg/L,total nitrogen≥6.4 mg/L,air temperature≥14.2℃and discharge≤0.3 m3/s are risk factors of low dissolved oxygen in Fuxi River.High air temperature is the primary risk factor,high concentration of total phosphorus and total nitrogen are secondary risk factors,and low river discharge made dissolved oxygen consumption increased.(2)On the one hand,the low DO is caused by the increase of temperature and the decrease of saturated dissolved concentration of water.,However,it is more important that the concentration of TP and TN in water body is high.With the rise of temperature,algae blooms and consume DO in river channel.(3)The restoration of river DO can be started by controlling TP and TN concentration and improving river flow and velocity.