中文关键词温室气体快速城市化区污染性河流时空特征影响因素 英文关键词greenhouse gasesrapidly urbanization areaspolluted riverspatial-temporal characteristicsinfluence factors

作者	单位	E-mail
刘婷婷	长江上游湿地科学研究重庆市重点实验室, 重庆 401331 重庆师范大学地理与旅游学院, 重庆 401331	liuting4501@163.com
王晓锋	长江上游湿地科学研究重庆市重点实验室, 重庆 401331 重庆师范大学地理与旅游学院, 重庆 401331	xiaofeng6540@163.com
袁兴中	长江上游湿地科学研究重庆市重点实验室, 重庆 401331 重庆师范大学地理与旅游学院, 重庆 401331 重庆大学煤矿灾害动力学与控制国家重点实验室, 重庆 400030 重庆大学资源及环境科学学院, 重庆 400030
龚小杰	长江上游湿地科学研究重庆市重点实验室, 重庆 401331 重庆师范大学地理与旅游学院, 重庆 401331
侯春丽	长江上游湿地科学研究重庆市重点实验室, 重庆 401331 重庆师范大学生命科学学院, 重庆 401331

中文摘要 河流是大气温室气体重要的排放源，近十多年来全球城市化导致河流生态系统各要素发生改变，对河流水体温室气体排放产生影响.为研究快速城市化区不同土地利用方式下河流温室气体排放的时空特征及其影响因素，采用薄边界层模型法，于2014年9月（秋季）和12月（冬季）及2015年3月（春季）和6月（夏季）的晴天对重庆市区内梁滩河干、支流水体pCO₂、CH₄、N₂O溶存浓度进行监测.结果表明，梁滩河干、支流水体pCO₂范围为（23.38±34.89）~（1395.33±55.45）Pa、CH₄溶存浓度范围（65.09±28.09）~（6021.36±94.36）nmol·L^-1、N₂O溶存浓度范围为（29.47±5.16）~（510.28±18.34）nmol·L^-1；CO₂、CH₄和N₂O排放通量分别为-6.1~786.9、0.31~27.62和0.06~1.08 mmol·（m²·d）^-1；流域水体温室气体浓度空间格局与快速城市化带来的污染负荷空间梯度吻合，干流温室气体浓度与通量从上游向下游均呈先增加后降低，在城市化速度最快的中游出现峰值，其中城市河段CO₂和CH₄浓度约为非城市河段的2倍，同时支流水体自上游农业区向下游城市区呈显著增加；由于受到降雨、温度、外源输入的综合影响，河流CO₂排放通量呈秋季>冬季>夏季>春季的季节模式，CH₄排放通量春季最高夏季最低，N₂O排放通量季节差异不显著.流域水体碳、氮含量均较高，水体CO₂的产生和排放不受生源要素限制，但受水温、pH、DO、叶绿素a等生物代谢因子影响；CH₄的产生和排放受水体碳、氮、磷含量和外源污水输入的共同驱动；N₂O的产生和排放主要受高N₂O浓度的城市污水排放影响.本研究认为流域快速城市化加快了河流水体温室气体排放，形成排放热源，因此城市河流温室气体排放对全球河流排放通量的贡献可能被忽视，在未来研究中应受到更多关注. 英文摘要 Rivers play an important role in greenhouse gas emissions. Over the past decade, because of global urbanization trends, rapid land use changes have led to changes in river ecosystems that have had a stimulating effect on the greenhouse gas production and emissions. Presently, there is an urgent need for assessments of the greenhouse gas concentrations and emissions in watersheds. Therefore, this study was designed to evaluate river-based greenhouse gas emissions and their spatial-temporal features as well as possible impact factors in a rapidly urbanizing area. The specific objectives were to investigate how river greenhouse gas concentrations and emission fluxes are responding to urbanization in the Liangtan River, which is not only the largest sub-basin but also the most polluted one in Chongqing City. The thin layer diffusion model method was used to monitor year-round concentrations of pCO₂, CH₄, and N₂O in September and December 2014, and March and June 2015. The pCO₂ range was (23.38±34.89)-(1395.33±55.45) Pa, and the concentration ranges of CH₄ and N₂O were (65.09±28.09)-(6021.36±94.36) nmol·L^-1 and (29.47±5.16)-(510.28±18.34) nmol·L^-1, respectively. The emission fluxes of CO₂, CH₄, and N₂O, which were calculated based on the method of wind speed model estimations, were -6.1-786.9, 0.31-27.62, and 0.06-1.08 mmol·(m²·d)^-1, respectively. Moreover, the CO₂ and CH₄ emissions displayed significant spatial differences, and these were roughly consistent with the pollution load gradient. The greenhouse gas concentrations and fluxes of trunk streams increased and then decreased from upstream to downstream, and the highest value was detected at the middle reaches where the urbanization rate is higher than in other areas and the river is seriously polluted. As for branches, the greenhouse gas concentrations and fluxes increased significantly from the upstream agricultural areas to the downstream urban areas. The CO₂ fluxes followed a seasonal pattern, with the highest CO₂ emission values observed in autumn, then successively winter, summer, and spring. The CH₄ fluxes were the highest in spring and the lowest in summer, while N₂O flux seasonal patterns were not significant. Because of the high carbon and nitrogen loads in the basin, the CO₂ products and emissions were not restricted by biogenic elements, but levels were found to be related to important biological metabolic factors such as the water temperature, pH, DO, and chlorophyll a. The carbon, nitrogen, and phosphorus content of the water combined with sewage input influenced the CH₄ products and emissions. Meanwhile, N₂O production and emissions were mainly found to be driven by urban sewage discharge with high N₂O concentrations. Rapid urbanization accelerated greenhouse gas emissions from the urban rivers, so that in the urban reaches, CO₂/CH₄ fluxes were twice those of the non-urban reaches, and all over the basin N₂O fluxes were at a high level. These findings illustrate how river basin urbanization can change aquatic environments and aggravate allochthonous pollution inputs such as carbon, nitrogen, and phosphorus, which in turn can dramatically stimulate river-based greenhouse gas production and emissions; meanwhile, spatial and temporal differences in greenhouse gas emissions in rivers can lead to the formation of emission hotspots.

PDF全文下载地址:

https://www.hjkx.ac.cn/hjkx/ch/reader/create_pdf.aspx?file_no=20190640&flag=1&journal_id=hjkx&year_id=2019