白洋淀入淀河流影响区水体综合耗氧特征及影响因素

Integrated oxygen consumption characteristic and influencing factors in inflow river impact zone of Baiyangdian Lake

针对白洋淀入淀河流影响区夏季溶解氧(DO)浓度过低的现象,综合采用水质数据时间序列分析、水体综合耗氧实验模拟和相关性统计分析等方法深入研究了府河影响区的南刘庄国控断面溶解氧逐时变化规律、不同下垫面类型水体耗氧速率以及其影响因素。结果表明:1)南刘庄断面DO质量浓度呈现出春秋季高夏季低的趋势,在水质逐年改善的背景下2022年夏季DO质量浓度仍低至1.5 mg∙L^(−1)左右;DO质量浓度日变幅在0.5~5.7 mg∙L^(−1)之间,均值为2.3 mg∙L^(−1),呈现出夏季>春季>秋季的状态;2)府河影响区水体耗氧速率在0.0240~0.0499 mg∙(L∙h)^(−1)之间,不同下垫面水域类型水体呈现水道≈淀面>沟壕的状态;不同深度水体基本呈现下层>上层和中层的趋势;水体综合耗氧速率中沉积物耗氧速率与水体耗氧速率的比值为1.55,水体和沉积物耗氧均是水体DO较低的重要原因;3)南刘庄断面DO质量浓度年内变化趋势与叶绿素a(Chla)(p<0.01)、浊度(p<0.01)和CODMn质量浓度(p<0.01)呈显著负相关关系;水体耗氧速率与叶绿素a(Chla)(p<0.01)、DOC(p<0.05)和CODMn质量浓度(p<0.05)呈显著正相关关系。降低河流来水浊度、抑制入淀河流影响区域夏季浮游藻类爆发增长、阶段开展生态清淤降低沉积物本身和孔隙水污染物扩散带来的高耗氧本底问题是白洋淀水质稳定达到Ⅲ类的根本保障。

Regarding the phenomenon of low dissolved oxygen(DO)concentration in the affected area of the Baiyangdian River during summer,this study employed time series analysis of water quality data,comprehensive oxygen consumption experiments on water bodies,and correlational statistical analysis to research the diurnal variation patterns of dissolved oxygen(DO)concentration at the Nanliuzhuang national control section within the Fu River's influence zone,the water oxygen demand over different underlying surface types,and their influencing factors during summer.The results showed that the DO concentration at the Nanliuzhuang section exhibited a seasonal pattern of higher levels in spring and autumn and lower levels in summer,with the concentration dropping to around 1.5 mg∙L^(−1) in summer of 2022 despite overall improvements in water quality over the years.The daily fluctuation range of DO concentration varied between 0.5~5.7 mg∙L^(−1),with an average of 2.3 mg∙L^(−1),showing a trend of summer>spring>autumn.The water oxygen demand in the Fu River's influence zone ranged from 0.0240 to 0.0499 mg∙(L∙h)^(−1),with the water bodies showing a pattern of canal≈lake surface>ditch in terms of different underlying surface water types.The water oxygen demand generally exhibited a trend of bottom layer>surface layer and middle layer across different depths.The ratio of sediment oxygen demand to water oxygen demand in the comprehensive oxygen consumption rates of water bodies was 1.55,indicating that both water and sediment oxygen demand significant reasons for the low DO concentration.The annual variation trend of DO concentration at the Nanliuzhuang section showed a significant negative correlation with chlorophyll a(Chla)content(p<0.01),turbidity(p<0.01),and CODMn concentration(p<0.01),and the water oxygen demand was significantly positively correlated with chlorophyll a(Chla)content(p<0.01),DOC concentration(p<0.05),and CODMn concentration(p<0.05).Reducing the turbidity of river inflows,suppressing the explosive growth of phytoplankton in the river inflow influence area during summer,and periodically conducting ecological dredging to reduce the high oxygen consumption background caused by sediment and pore water pollutant diffusion were fundamental to ensuring the stable achievement of Class III water quality standards in Baiyangdian Lake.