College of Geography and Tourism, Chongqing Normal University, Chongqing 400047, China; Wetland Science Research Center of the Upper Reaches of the Yangtze River, Chongqing Normal University, Chongqing 400047, China.
Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration Biodiversity Conservation, Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, China; Zoige Peatland and Global Change Research Station, Chinese Academy of Sciences, Hongyuan 624400, China.
Sci Total Environ. 2018 May 1;622-623:1079-1089. doi: 10.1016/j.scitotenv.2017.12.054. Epub 2017 Dec 13.
Urbanization and greenhouse gas emissions are of great global concern, especially in developing countries such as China. However, little is known about the relationship between the two. In this study, we examined the influences of the urbanization of Chongqing Municipality, which covers an area of 5494km, in China, on the CH emissions of in its metropolitan river network. The results from 84 sampling locations showed an overall mean CH concentration of 0.69±1.37μmol·L and a CH flux from the river network of 1.40±2.53mmolCHmd. The CH concentrations and fluxes presented a clear seasonal pattern, with the highest value in the spring and the lowest in the summer. Such seasonal variations were probably co-regulated by the dilution effect, temperature and supply of fresh organic matter by algal blooms. Another important result was that the CH concentrations and fluxes increased with the degree of urbanization or the proportion of urban land use, being approximately 3-13 times higher in urban and suburban areas than in rural ones. The total nitrogen, dissolved oxygen (O%) and possible sewage discharge, which could affect the in situ CH production and exogenous CH input respectively, were important factors that influenced the spatial patterns of CH in human-dominated river networks, while the nitrogen (N) and phosphorus (P) could be good predictors of the CH emissions in urban watersheds. Hydrologic drivers, including bottom sediment type, flow velocity and river width, were strongly correlated with the CH concentrations and could also affect the spatial variance and predict the CH hotspots in such metropolitan river networks. With increasing urbanization, we should pay more attention to the increasing greenhouse gas emissions associated with urbanization.
城市化和温室气体排放是全球关注的重大问题，特别是在中国等发展中国家。然而，人们对这两者之间的关系知之甚少。在本研究中，我们考察了中国重庆市（面积 5494km）的城市化对其大都市区河流网络中 CH 排放的影响。来自 84 个采样点的结果显示，CH 浓度的总体平均值为 0.69±1.37μmol·L，河流网络的 CH 通量为 1.40±2.53mmolCHmd。CH 浓度和通量呈现出明显的季节性模式，春季最高，夏季最低。这种季节性变化可能受到稀释效应、温度和藻类大量繁殖提供的新鲜有机物质供应的共同调节。另一个重要的结果是，CH 浓度和通量随城市化程度或城市土地利用比例的增加而增加，城市和郊区的 CH 浓度和通量大约比农村地区高 3-13 倍。总氮、溶解氧（O%）和可能的污水排放，分别可能影响原位 CH 产生和外源 CH 输入，是影响人为主导的河流网络中 CH 空间格局的重要因素，而氮（N）和磷（P）可以很好地预测城市流域的 CH 排放。水文驱动因素，包括底泥类型、流速和河宽，与 CH 浓度密切相关，也可以影响空间变异性，并预测大都市区河流网络中的 CH 热点。随着城市化的推进，我们应该更加关注与城市化相关的温室气体排放的增加。
