辽河口滨海湿地CH_4排放特征及其影响因素

Characteristics and impact factors of methane emission in coastal wetland of the Liaohe estuary

采用静态箱-气相色谱法,于2016年6—11月连续观测辽河口芦苇湿地、翅碱蓬湿地和裸滩湿地的CH_4排放速率,同时测定温度、氧化还原电位(Eh)、pH值和电导率(EC)等相关环境因子的动态变化。结果表明,3种类型湿地的CH_4排放具有明显的季节变化特征,均呈先上升后下降趋势。芦苇湿地、翅碱蓬湿地(涨潮前)和裸滩湿地(涨潮前)CH_4排放通量变化范围分别为0.447—10.40、0.045—0.509 mg m^(-2) h^(-1)和0.016—0.593 mg m^(-2) h^(-1),观测期内排放通量均值相应为(3.699±3.679)、(0.165±0.156) mg m^(-2) h^(-1)和(0.198±0.191) mg m^(-2) h^(-1),不同类型湿地之间差异显著(P<0.01),芦苇湿地>裸滩湿地(涨潮前)>翅碱蓬湿地(涨潮前)。涨潮过程中,翅碱蓬湿地和裸滩湿地的排放速率分别变化在0.009—0.353 mg m^(-2) h^(-1)和0.018—0.335 mg m^(-2) h^(-1),观测期间其排放速率均值分别为(0.119±0.132) mg m^(-2) h^(-1)和(0.131±0.103) mg m^(-2) h^(-1),明显低于涨潮前(P<0.01)。不同湿地类型间CH_4排放通量与电导率(EC)呈显著负相关(P<0.01)。研究结果表明,潮汐和电导率均为影响辽河口不同类型湿地中CH_4排放的关键因子。

A monthly investigation of methane flux in Phragmites australis wetland, Saline seepweed wetland, and mudflat at Liaohe Estuary was carried out from June to November in 2016, using an enclosed chamber technique. Simultaneously, environmental factors, including soil temperature, redox potential (Eh), electrical conductivity (EC), and pH values were measured to evaluate its influence on methane emission. The results showed that:(i) the methane flux in the three types of wetland showed obvious seasonal variations, which is higher in summer than that in spring and autumn;(ii) the methane flux was 0.447-10.40 mg m^-2 h^-1 with a mean of 3.699 ±3.679 in P. australis wetland. During ebb tides, methane flux was 0.045-0.509 and 0.016-0.593 mg m^-2 h^-1 with a mean of 0.165 ±0.156 and 0.198 ±0.191 mg m^-2 h^-1 in the Saline seepweed wetland and mudflat, respectively. The methane flux was significantly different among the three wetland types (P < 0.01), which is highest in P. australis, and followed by mudflat, Saline seepweed wetland;(iii) during flood tide, the methane flux ranged from 0.009 to 0.353 mg m^-2 h^-1 and 0.018 to 0.335 mg m^-2 h^-1 with means of 0.119 ±0.132 and 0.131 ±0.103 mg m^-2 h^-1 in Saline seepweed wetland and mudflat, respectively. The mean fluxes of methane during flood tides were significantly lower than that of ebb tide (P < 0.01);and (iv) furthermore, methane fluxes negatively correlated with the EC values in the three wetland types (P < 0.01). The results indicate that tide and salinity are the key factors to influence methane emission from the coastal wetlands of Liaohe estuary.