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对珠江口淇澳岛海岸带沉积物间隙水中甲烷、硫酸盐、CH4-δ13C和ΣCO2-δ13C的地球化学参数垂直剖面特征的研究结果显示:甲烷浓度梯度在硫酸盐还原带底部急剧增大,而间隙水硫酸盐浓度随深度呈线性降低;在硫酸盐-甲烷转换带(SMT)中,甲烷碳同位素逐渐变重,并引起间隙水ΣCO2-δ13C值变为极负.间隙水地球化学参数的变化特征提供了该区域沉积物中存在AOM作用的证据.根据数学模型计算出的三个站位甲烷厌氧氧化速率和硫酸盐还原速率,可知AOM消耗的硫酸盐占总硫酸盐损耗的比例分别为9.0%,84%和45.5%,对应的AOM产生的ΣCO2占总CO2的比例分别为4.7%,72.4%和29.45%.有机质的输入量的大小影响沉积物底部甲烷浓度、扩散通量及SMT分布.较高的有机质输入量一方面有利于加速间隙水硫酸盐通过有机质矿化分解作用损耗,另一方面引起进入SMT的甲烷扩散通量增大,使得AOM过程硫酸盐的消耗量相应增大,结果造成SMT向沉积物表层上移.
The results of vertical geochemical profiles of methane, sulfate, CH4-δ13C and ΣCO2-δ13C in the sediment interstitial water in the coastal area of Qi’ao Island in the Pearl River estuary show that the methane concentration gradient sharply increases at the bottom of the sulfate reduction zone, The concentration of sulfate in interstitial water decreases linearly with depth. In the sulfate-methane conversion zone (SMT), the carbon isotopes of methane gradually become heavier and cause the ΣCO2-δ13C value of interstitial water to become extremely negative. The variation of geochemical parameters of interstitial water Features provide evidence of the presence of AOM in the sediments of the region.According to the mathematical model of methane anaerobic oxidation rate and sulfate reduction rate calculated at three stations, we can see AOM consumption of sulfate in total sulfate loss ratio were 9.0%, 84% and 45.5%, respectively, and the proportion of ΣCO2 to total CO2 in the corresponding AOM was 4.7%, 72.4% and 29.45%, respectively.The input of organic matter affected the methane concentration, flux and SMT distribution The higher input of organic matter facilitates the depletion of interstitial water sulfate through the mineralization and decomposition of organic matter on the one hand and the increase of methane diffusion flux into SMT on the other hand, The consumption increase accordingly, resulting in a shift to the SMT surface sediments.