西宁市湿地不同界面温室气体排放通量及影响因素研究

Characterization of greenhouse gas emission fluxes at different interfaces and influencing factors in Xining wetlands

关键词:  高原城市湿地  温室气体  排放通量  冗余分析

Key words:  Plateau urban wetlands  greenhouse gas  emission fluxes  redundancy analysis

摘要:

城市湿地作为区域碳氮循环的重要成分，研究城市湿地不同界面的温室气体排放通量，可为区域碳收支估算和温室气体减排提供依据。通过静态暗箱法采集西宁市湿地不同时期、不同界面的温室气体并测定，分析湿地不同界面温室气体排放通量特征，通过采集样点内的表层土壤、水体和沉积物并测定，分析理化性质与温室气体排放通量的相关关系。结果表明：海湖湿地土-气界面平均CH4排放通量最大，为6.25-16.48 μg·m-2·h-1，宁湖湿地水-气界面平均CH4排放通量最大，为27.36-86.41 μg·m-2·h-1。海湖湿地两种界面的平均CO2排放通量都为最大值，分别为7.95-35.55 mg·m-2·h-1和3.95-22.49 mg·m-2·h-1，宁湖湿地N2O排放通量为土-气界面最大和水-气界面最小。湿地理化性质方差分析结果中，受到不同湿地和时期影响的指标主要有土壤pH、TN（Total nitrogen）、TOC（Total organic carbon）与沉积物和水体的NH3-N（Ammonia nitrogen）、TP（Total phosphorus）、TN和TOC等。冗余性分析结果显示，影响湿地温室气体排放的主要因子为温度、容重、pH、TOC、TP和TN等。此外，研究发现温室气体排放通量大小为海湖湿地>宁湖湿地>北川河湿地，不同湿地水-气界面CH4排放通量均高于土-气界面，而水-气界面CO2排放通量低则于土-气界面，N2O排放通量则是土-气界面略大于水-气界面，不同时期的温室气体排放通量丰水期均要大于平水期和枯水期，温室气体的排放主要受到湿地内水热条件的影响。

Abstract:

Urban wetlands are important components of the regional carbon and nitrogen cycles, and the study of greenhouse gas emission fluxes at different interfaces of urban wetlands can provide a basis for the estimation of regional carbon balance and greenhouse gas emission reduction. The greenhouse gases at different interfaces in Xining wetland in different periods were collected and measured by static dark box method to analyse the characteristics of greenhouse gas emission fluxes at different interfaces in the wetland, and the correlation between the physicochemical properties and greenhouse gas emission fluxes was analysed by collecting and measuring the surface soils, water bodies and sediments within the sample sites. The results showed that the average CH4 emission flux at the soil-gas interface of Haihu Wetland was the largest, ranging from 6.25 to 16.48 μg·m-2·h-1, while that at the water-gas interface of Ninghu Wetland was the largest, ranging from 27.36 to 86.41 μg·m-2·h-1. The average CO2 emission fluxes at both interfaces in the Haihu wetland were the maximum, 7.95-35.55 and 3.95-22.49 mg·m-2·h-1, respectively, and the N2O emission fluxes in the Ninghu wetland were the maximum at the soil-gas interface and the minimum at the water-gas interface. In the ANOVA results of wetland physicochemical properties, the indicators that were affected by different wetlands and periods were mainly soil pH, TN (Total nitrogen), TOC (Total organic carbon) with sediment and water body NH3-N (Ammonia nitrogen), TP (Total phosphorus), TN and TOC, etc. The results of redundancy analyses showed that the main factors affecting GHG emissions from wetlands were temperature, bulk density, pH, TOC, TP and TN. In addition, it was found that the magnitude of GHG emission fluxes was Haihu Wetland>Ninghu Wetland>Beichuan River Wetland, CH4 emission fluxes were higher than those at the soil-gas interface in different wetlands, while CO2 emission fluxes at the water-gas interface were lower than those at the soil-gas interface, and the emission fluxes of N2O were slightly larger than those at the soil-gas interface than those at the water-gas interface, and the emission fluxes of GHGs in different periods of time were larger than those in the flat water period and the dry water period. The emission of greenhouse gases is mainly affected by the hydrothermal conditions in the wetland.