Li Lei, Chen Hao, Zhu Yi, Wang Yu-Hui, Nie Yun-Han, Zhao Xin, Jia Qi-Long, Ye Jian-Feng
College of Environmental Science and Engineering, Donghua University, Shanghai 201620, China.
Shanghai Academy of Environmental Sciences, Shanghai 200233, China.
Huan Jing Ke Xue. 2020 Jul 8;41(7):3392-3401. doi: 10.13227/j.hjkx.201912080.
The increasing carbon emission of polluted rivers in urban areas is an environmental problem commonly faced by many cities in China, especially the megacities with vast populations. In this study, two typical rivers located in the megacity of Shanghai, including the suburban river network R1 and urban river R2 (in the central city), were investigated for their emission characteristics of CO and CH in dry and wet weather. We also analyzed the relationship between the state and type of river pollution and CO and CH emissions, and further explained the mechanisms of CO and CH emissions in urban rivers impacted by sewage discharged from the municipal drainage network. The results show that:① In dry weather, the average fluxes of CO and CH emitted from the river in the central city (R2) were (2.48±1.02) mmol·(m·h) and (1.21×10±0.71×10) mmol·(m·h), respectively. The average fluxes of CO and CH from the suburban river (R1) network were (1.53±0.39) mmol·(m·h) and (9.26×10±9.18×10) mmol·(m·h), respectively. In wet weather, affected by sewage from the municipal drainage network, CH flux emitted from the surface water of the R2 river downstream of the pump station P increased by up to 119 times that in dry weather. ② Global carbon emission statistics, involving the data from our study and from other rivers around the world, seemed to imply a relationship between the carbon emission flux and the pollution state of an urban river, i.e., the rivers with high pollution showed significant carbon emission intensity. ③ According to the results of PCA, organic matter can be an essential factor in driving the variation of carbon emissions, and this trend is evident in all the rivers in urban and suburban areas. The relationship between carbon emissions and nitrogen pollution in a river varies with different types of underlying riparian surface. In the less polluted urban rivers, the aquatic physical factor can also be an essential factor. ④ In the short term, with massive quantities of sewage discharged into urban rivers, a large amount of CH flux can be emitted. In contrast, in the long run, the carbon cycle can be strengthened when the carbon storage is increased, and thus the emission potential of CO and CH is improved.
城市地区污染河流碳排放增加是中国许多城市，尤其是人口众多的特大城市普遍面临的环境问题。本研究以上海这座特大城市中的两条典型河流为研究对象，包括郊区河网R1和市区河流R2（位于市中心），调查了它们在干、湿天气条件下的CO和CH排放特征。我们还分析了河流污染状态和类型与CO和CH排放之间的关系，并进一步解释了受市政排水管网排放污水影响的城市河流中CO和CH排放的机制。结果表明：①在干燥天气下，市中心河流（R2）的CO和CH平均排放通量分别为(2.48±1.02) mmol·(m·h)和(1.21×10±0.71×10) mmol·(m·h)。郊区河网（R1）的CO和CH平均排放通量分别为(1.53±0.39) mmol·(m·h)和(9.26×10±9.18×10) mmol·(m·h)。在潮湿天气下，受市政排水管网污水影响，泵站P下游R2河地表水的CH通量增加，最高可达干燥天气下的119倍。②全球碳排放统计数据，包括我们的研究数据和世界其他河流的数据，似乎暗示了碳排放通量与城市河流污染状态之间的关系，即污染程度高的河流碳排放强度显著。③根据主成分分析结果，有机物可能是驱动碳排放变化的一个重要因素，这种趋势在城市和郊区的所有河流中都很明显。河流中碳排放与氮污染的关系因不同类型的河岸底层表面而异。在污染较轻的城市河流中，水生物理因素也可能是一个重要因素。④短期内，大量污水排入城市河流会排放大量的CH通量。相比之下，从长期来看，当碳储存增加时，碳循环可以得到加强，从而提高CO和CH的排放潜力。
