盐分对河口淡水、微咸水沼泽湿地土壤甲烷产生潜力的影响

海平面上升导致河口区盐水入侵现象日益明显,深刻影响着河口潮汐淡水、微咸水湿地生物地球化学循环。采集闽江河口区淡水、微咸水短叶茳芏潮汐沼泽湿地表层土样,室内添加盐度为5,10,15,21 g/L的人造海水、Na Cl溶液及盐度为0的去离子水,通过室内泥浆厌氧培养试验,对比研究海水和Na Cl溶液对淡水、微咸水沼泽湿地土壤甲烷产生潜力的影响。与对照相比,1—12 d培养期内4个盐度的海水处理均显著抑制河口淡水、微咸水沼泽湿地甲烷产生潜力,抑制率在93%以上,盐度10—21 g/L的3个海水处理对于河口淡水、微咸水沼泽湿地甲烷产生潜力的抑制效应无显著差异。Na Cl溶液只有在盐度达到15和21 g/L才显著抑制淡水、微咸水沼泽湿地甲烷产生潜力,且抑制率最多为80.9%,盐度为5、10 g/L的Na Cl溶液对淡水、微咸水沼泽湿地甲烷产生潜力的抑制作用不显著,抑制率多小于30%。伴随着盐水入侵而发生的硫酸盐还原作用及离子胁迫作用对河口淡水、微咸水沼泽湿地甲烷产生具有显著的抑制效应。

Effects of seawater and NaCl solution pulses on methane production potential from laboratory-incubated tidal freshwater and brackish marsh soil

Sea level rise increases the frequency and intensity of saltwater intrusion events, and it affects the soil biogeochemical cycle in estuarine freshwater and brackish wetlands. A laboratory study measured the methane production potentials during from the topsoil of two freshwater Cyperus malaccensis marshes and two brackish C. malaccensis marshes during 12 days of incubation when exposed to varying salinities (0, 5, 10, 15, and 21 g/L of seawater or salt NaCl] solutions). Seawater addition with a salinity range from 5 to 21 g/L induced a progressive suppression of methane production potentials. For all levels of salinity, except the freshwater control, more than 93% of methane production potential was inhibited, whereas there was no significant difference of suppression effects on methane production potentials upon the addition of seawater with a salinity range from 10 to 21 g/L. Ionic stress (represented by NaCl) reduced methane production potentials in both 15 and 21 g/L NaCl addition treatments; 5 and 10 g/L NaCl treatments did not significantly reduce methane production potentials (percentage of inhibition was less than 30%). Our results indicate that SO₄^2- reduction, not osmotic stress by chloride ions, is the main process suppressing methane production in estuarine freshwater and brackish marshes following seawater intrusion.