Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires (IGEBA), Intendente Güiraldes 2160, Pabellón II, Piso 1, CP 1428, Ciudad Universitaria, CABA, Argentina.
Instituto de Geocronología y Geología Isotópica, Intendente Güiraldes 2160, Pabellón INGEIS, CP 1428, Ciudad Universitaria, CABA, Argentina.
Environ Monit Assess. 2018 Oct 18;190(11):647. doi: 10.1007/s10661-018-7026-3.
Subsoil CH and CO concentrations, δC-CH and δC-CO signatures, total organic carbon (TOC) and δC-TOC, together with C/N ratio of organic matter, were evaluated throughout a soil profile up to the atmosphere to understand the dynamics of CH and CO in the waterlogged environment of an island of the Lower Delta of the Paraná River, Argentina. The analysis of the vertical profile showed that a significant fraction of CH exists as gas trapped within the sediment column, compared to CH dissolved in soil solution. CH concentration measurements in sub-saturated soils showed that free CH is 1 order of magnitude smaller than CH recovered from soil cores by ultrasonic degassing. The highest concentrations of CH occurred at the 90-120-cm layer. At this depth, δC-CH values resulting from methanogenesis were around - 71‰, which is well within the range of CH produced from CO reduction, and δC values of the associated CO were enriched (~ - 7‰). Isotope mass balance models used to calculate the fraction of oxidized CH indicated that around 30% of the CH produced was oxidized prior to atmospheric release. In contrast to methanogenesis, during oxidation processes δC-CH shifts to more positive values. The mineralogical, textural, isotopic, and geochemical characterization of subsoil sediments with abundant organic matter, like Paraná Delta, demonstrated that CH storage capacity of the soil, production, consumption, and transport are the main factors in regulating the actual flux rates of CH to the atmosphere.
对阿根廷巴拉那河下游三角洲岛屿湿地土壤剖面中地下 CH 和 CO 浓度、δC-CH 和 δC-CO 特征、总有机碳 (TOC) 和 δC-TOC 以及有机质的 C/N 比进行了评估，以了解 CH 和 CO 在该水饱和环境中的动态。垂直剖面分析表明，与溶解在土壤溶液中的 CH 相比，大量 CH 以气体形式被困在沉积物柱中。亚饱和土壤中 CH 浓度的测量表明，游离 CH 的浓度比通过超声脱气从土壤芯中回收的 CH 低 1 个数量级。CH 浓度最高的层出现在 90-120cm 层。在这一深度，由产甲烷作用产生的 δC-CH 值约为-71‰，这很好地处于由 CO 还原产生的 CH 范围内，并且相关 CO 的 δC 值也富集了（约-7‰）。用于计算氧化 CH 分数的同位素质量平衡模型表明，在大气释放之前，约有 30%的 CH 被氧化。与产甲烷作用相反，在氧化过程中，δC-CH 向更正值偏移。富含有机质的地下沉积物（如巴拉那三角洲）的矿物学、结构、同位素和地球化学特征表明，土壤的 CH 储存能力、生产、消耗和运输是调节 CH 向大气实际通量的主要因素。
