新丰江水库溶解氧分布特征及其影响因素分析

Spatio-temporal Variations and Influencing Factors of Dissolved Oxygen in Xinfengjiang Reservoir

新丰江水库是典型的南亚热带深水贫营养型水库,是粤港澳大湾区重要的饮用水水源。鉴于溶解氧(DO)作为决定水库水质类别的唯一关键指标,为了解其水库的DO变化特征,基于2018年4月—2022年11月连续5年的监测数据,采用连续小波变换、交叉小波变换、最大信息系数、相关系数和多元线性回归等方法分析DO时空变化特征及主要影响因素。结果表明,在时间分布上,DO月平均值为6.94~9.48 mg/L,均能达到国家《地表水环境质量标准》(GB 3838—2002)Ⅰ类水质标准值(7.5)或Ⅱ类(6.0 mg/L),总体呈“V”字型变化,夏末秋初(9—10月)DO值最低,水库DO主要在11~12个月和35~37个月的年周期下循环变化。空间分布上,DO平均值的空间差异性小,6个点位DO年平均值为7.95~8.16 mg/L,均能达到Ⅰ类水质标准值。不同点位间DO最大均值和最小均值相差仅为0.2 mg/L,DO值自上游入库口至下游出库口缓慢降低。最大信息系数、交叉小波变换、相关系数和多元线性回归分析结果表明,新丰江水库DO值受多个因素的综合影响,其中,水温是DO时空分布的关键因素,其次为pH值。该研究对于深入认识贫营养水体表层DO影响机制和规律提供参考依据。

As a typical subtropical oligotrophic reservoir,Xinfengjiang Reservoir is an important drinking water source for Guangdong-HongKong-Macao Greater Bay Area.Dissolved oxygen(DO)is usually considered as the only key indicator that determines the water quality type of Xinfengjiang Reservoir.To understand the monthly and seasonal variation characteristics of DO and its influencing factors,five approaches including continuous wavelet transform(CWT),cross wavelet transform(XWT),maximum information coefficient(MIC),correlation coefficient(CC)and multiple linear regression(MLR)were applied based on five consecutive years data obtained from Apr.2018 to Nov.2022.The results showed that DO monthly concentration were between 6.94 mg/L and 9.48 mg/L and all met classⅠor classⅡset by the“Surface Water Environmental Quality Standard”GB 3838—2002).The DO changed in a cycle of 11~12 months and 35~37 months from 2018 to 2022 a V-shaped change presented on temporal distribution,and the low DO values appeared in September or October.The DO spatial variation was small and all met classⅠset by the“Surface Water Environmental Quality Standard”(GB 3838—2002).The annual average concentration of DO was between 7.95 mg/L and 8.16 mg/L at six stations,the difference of maximum and minimum value was only 0.2 mg/L.DO concentration gradually decreased from upstream to downstream.MIC,XWT,CC and MLR analysis between DO and environmental factors showed that DO were subjected to a comprehensive influence of multiple factors,among them,water temperature was the key factor affecting DO,followed by pH value.The present study has great significance for further understanding the impacts and mechanisms of DO change in oligotrophic reservoir.