Halocarbon Emissions from a Degraded Forested Wetland in Coastal South Carolina Impacted by Sea Level Rise
Halocarbon Emissions from a Degraded Forested Wetland in Coastal South Carolina Impacted by Sea Level Rise
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DOI：
10.1021/acsearthspacechem.8b00044
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发表时间：
2018-10-01
影响因子：
3.4
通讯作者：
Rhew, Robert C.
中科院分区：
文献类型：
--
作者：
Jiao, Yi;Ruecker, Alexander;Rhew, Robert C.
热带和亚热带风暴潮加上海平面上升导致盐水侵入美国东南部沿海沿着的低洼沿海生态系统，逐渐将淡水森林湿地转化为盐沼。淡水和咸水生态系统之间的过渡区变成了退化的森林湿地，在那里，高水平的土壤有机质和高浓度的卤离子的组合创造了一个动态的生物地球化学环境，可能是一个潜在的热点卤烃形成，如氯仿，氯甲烷和甲基溴。本研究进行了实地测量，在沿海的过渡带南卡罗来纳州，以量化卤化碳的交换率和实验室土壤培养，以确定生物与非生物过程的贡献。退化的森林湿地表现出明显的氯仿排放率（146 +/- 129 nmol m（-2）d（-1））。退化的森林湿地仍然是甲基氯的净吸收汇，而甲基溴的源/吸收汇则可以忽略不计，这与盐沼不同，盐沼是这两种物质的重要来源。实验室培养强烈表明，在现场土壤中的卤甲烷消费是生物的，而卤甲烷和氯仿的生产主要是非生物和温度依赖性，虽然需要额外的实验来排除可能的生物生产涉及耐热微生物。研究结果表明，从长远来看，全球气候变化导致的海平面上升和更频繁的风暴潮可能会增加沿海退化森林湿地的氯仿排放量，如果盐沼扩大，可能会增加甲基卤化物的排放量，从而对平流层臭氧消耗产生潜在影响。
Tropical- and subtropical-storm surges combined with sea level rise cause saltwater intrusions into low-lying coastal ecosystems along the southeastern coast of the United States, gradually converting freshwater forested wetland into saltmarsh. The transition zone between freshwater and saltwater ecosystems becomes a degraded forested wetland, where the combination of high levels of soil organic matter and elevated concentrations of halide ions creates a dynamic biogeochemical environment that may be a potential hotspot for halocarbon formation such as chloroform, methyl chloride, and methyl bromide. This study conducted field measurements at a transition zone in coastal South Carolina to quantify halocarbon exchange rates and laboratory soil incubations to determine the contributions of biotic versus abiotic processes. The degraded forested wetland showed significant chloroform emission rates (146 +/- 129 nmol m(-2) d(-1)). The degraded forested wetland remained a net sink for methyl chloride and a negligible source/sink for methyl bromide, unlike the saltmarsh which was a significant source for both. The laboratory incubations strongly suggest that methyl halide consumption in soils at the field site was biotic and that production of methyl halides and chloroform was largely abiotic and temperature-dependent, although additional experiments are required to rule out possible biotic production involving heat-resistant microbes. The results suggest that sea level rise and more frequent storm surges derived from global climate change, in the long term, may increase emissions of chloroform from coastal degraded forested wetlands and of methyl halides if salt marshes expand, with potential impacts for stratospheric ozone depletion.