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91.
对南海东沙海域冷泉区DH-CL10和DH-CL5柱状样开展AMS14C年代学、高分辨率底栖有孔虫和沉积物同位素以及沉积学研究。结果表明:DH-CL10柱状样在全新统底部574 cm处出现沉积间断,间断面相邻沉积物AMS14C年龄分别为9 850/(9 680~9 950) cal.aBP和27 610/(27 500~27 700) cal.aBP,相当于MIS2期和部分MIS3期的沉积缺失。底栖有孔虫Uvigerina bifurcata的δ13C值为-0.37‰~-1.91‰,平均值为-1.11‰,沉积物全岩碳同位素值为-22.7‰~-23‰,均为正常的碳同位素值。尽管该柱状样未发现天然气水合物分解释放的地球化学证据,但相邻的DH-CL5柱状样相当于其所缺失的部分沉积中的自生碳酸盐岩和沉积物的δ13C负偏明显,分别为-55.24‰和-25.9‰~-27.9‰,表明与天然气水合物分解有关。推断DH-CL10柱状样沉积间断所缺失的沉积物可能记录了天然气水合物分解的证据,且沉积间断主要出现在末次盛冰期低海平面,与天然气水合物易分解的时间相吻合,因此,沉积间断的形成可能主要与下伏天然气水合物的分解导致沉积物的滑塌有关。 相似文献
92.
湿地甲烷氧化是控制湿地甲烷通量的重要因子.本文对湿地甲烷氧化的测定方法与主要控制因子进行了综述.湿地甲烷氧化的测定方法主要包括未添加甲烷氧化抑制剂培养法和添加甲烷氧化抑制剂培养法.湿地甲烷氧化是诸多因子综合作用的结果,控制湿地甲烷氧化的因子包括湿地生态系统类型、温度、土壤湿度、底物、pH值等.比较而言,底物的浓度(甲烷和氧化性物质)以及土壤湿度是更为重要的环境因子. 相似文献
93.
《Polar Science》2014,8(2):156-165
Forest soils are generally sinks of CH4 and sources of N2O. To characterize the dynamics of these major greenhouse gases in central Siberia during the growing season, we measured fluxes from forest soil and assessed the relationships between CH4 and N2O fluxes and forest floor vegetation types, soil temperature, and moisture conditions. At the soil surface, both CH4 uptake and emission (−6.6 to 3.1 μg CH4–C m−2 h−1) were observed, and CH4 fluxes did not differ among vegetation types. CH4 flux was positively correlated with soil moisture, but not with soil temperature. The small CH4 uptake compared with previous reports was due to CH4 production in response to high precipitation. N2O was also emitted and taken up by soil (−0.2 to 0.4 μg N2O–N m−2 h−1), and N2O fluxes did not differ among vegetation types. N2O flux was negatively correlated with soil moisture and not correlated with soil temperature. Our findings suggest that high soil moisture and low availability of mineral nitrogen resulted in N2O uptake due to denitrification. Furthermore, both CH4 and N2O were emitted from a river at the site; these were produced in the basin of the riverbank rather than deep in the soil. 相似文献
94.
95.
The concentrations of two greenhouse gases, nitrous oxide (N2O) and methane (CH4), and the bacterial processes involved in their production (nitrification and denitrification for N2O, and methanogenesis for CH4), were determined in surface waters of two coastal areas under the influence of freshwater inputs, on one part in the Gulf of Lions and the Rhone River plume, in northwestern Mediterranean Sea, and on the other part in the inner Thermaikos Gulf, in Aegean Sea, eastern Mediterranean Sea. High concentrations of dissolved CH4 and N2O were recorded in the surface waters of Gulf of Lions and Gulf of Thermaikos, up to 1300 nM for CH4, and 40 nM for N2O. No direct relationship could be found between the concentration and production of the biogases, as they may also be produced in deep water or bottom sediment in shallow areas, or derived from anthropogenic activity or ship contamination in polluted areas. Irrespective of the origin of CH4 and N2O, the presence of extremely high concentrations of these two gases in superficial seawater implies that they can easily escape to the atmosphere; consequently, these nearshore waters enriched in greenhouse gases may play an important role in the increase in atmospheric concentration of both CH4 and N2O. 相似文献
96.
琼东南盆地与甲烷渗漏有关的早期成岩作用和孔隙水化学组分异常 总被引:1,自引:0,他引:1
X-射线衍射和扫描电镜观察表明,采自南海北部琼东南盆地的沉积物样品中有天然气水合物和甲烷渗漏指示意义的自生碳酸盐、硫酸盐和草莓状framboids黄铁矿,自生矿物组合和显微结构特征与冷泉沉积物类似,属微生物成因。沉积物孔隙水化学组分分析结果显示,随着埋藏深度加深,SO42-,Ca2+,Mg2+和Sr2+浓度明显降低,Mg2+浓度与Ca2+浓度和Sr2+浓度与Ca2+浓度的比值急剧增加,这些地球化学特征与世界上天然气水合物产区的浅表层沉积物孔隙水中离子浓度异常吻合较好,暗示采样站位深部可能有油气或天然气水合物藏。 相似文献
97.
C. R. Fisher J. M. Brooks J. S. Vodenichar J. M. Zande J. J. Childress R. A. Burke Jr. 《Marine Ecology》1993,14(4):277-289
Abstract. In April 1990 a new species of mytilid containing bacterial endosymbionts was discovered at a deep-water seep site within Alaminos Canyon in the Gulf of Mexico. Activities of ribulose bisphosphate carboxylase/oxygenase and ATP sulfurylase, as well as the presence of substantial levels of elemental sulfur in the gill tissues indicate the presence of chemoautotrophic sulfur-oxidizing symbionts in the gills. Methanol dehydrogenase activity and the tissue stable carbon isotope ratios indicate the presence of methanotrophic bacteria in the gills of the same animals. Two distinct size classes and morphological types of gram negative bacteria are visible in transmission electron micrographs of the gill tissue, one of which contains the complex internal membranes typical of methanotrophs. Both general types of symbionts have been demonstrated singly in related species of deep-sea mytilids. In this species, however, both types are found in single individuals, often within the same cell vacuole. 相似文献
98.
Although the methane in marine methane hydrates is mainly of microbial origin, information about the distribution of methanogens in subseafloor sediments is limited. To address this issue, we analyzed sediment core samples from two sites in the Nankai Trough, off the Pacific coast of central Japan, including those bearing methane hydrates from depths > 100 m below the seafloor (mbsf), for isopranyl ether-linked polar lipids (i.e. with polar head groups of phosphate, sugar, or both) as biomarkers of archaea, including methanogens. In most samples, including the deepest (381 mbsf), archaeol, and sn-2- and sn-3-hydroxyarchaeols were detected as their hydrolyzed derivatives. Concentrations of these three archaeal lipids correlated strongly with each other, suggesting a common biological source. The δ13C values of phytane derived from the phytanyl groups in the archaeal lipids were distinctly higher than those of methane, indicating that methanogens rather than anaerobic methanotrophic archaea were the major biological source. Depth profiles of polar sn-2-hydroxyarchaeol concentration were consistent with those of the potential methane production activity previously estimated from incubation of core sediments from the same sites. This observation, together with results of previous studies showing the presence of sn-2-hydroxyarchaeol mainly in shallow young sediments, strongly suggests that this polar lipid is a valid biomarker for in situ methanogens in sediments. There was a strong correlation between the concentration of polar sn-2-hydroxyarchaeol and that of total organic carbon, suggesting that bulk organic matter concentration is a primary control on the distribution of methanogens in sediments. 相似文献
99.
100.
14C measurements of CH4 in environmental samples (e.g. soil gas, lake water, gas hydrates) can advance understanding of C cycling in terrestrial and marine systems. The measurements are particularly useful for detecting the release of old C from climate sensitive environments such as peatlands and hydrate fields. However, because 14C CH4 measurements tend to be complex and time consuming, they are uncommon. Here, we describe a novel vacuum line system for the preparation of CH4 and CO2 from environmental samples for 14C analysis using accelerator mass spectrometry (AMS). The vacuum line is a flow-through system that allows rapid preparation of samples (1 h for CH4 and CO2, 30 min for CH4 alone), complete separation of CH4 and CO2 and is an easy addition to multipurpose CO2 vacuum lines already in use. We evaluated the line using CH4 and CO2 standards with different 14C content. For CH4 and CO2, respectively, the total line blank was 0.4 ± 0.2 and 1.4 ± 0.6 μg C, the 14C background 51.1 ± 1.2 and 48.4 ± 1.5 kyr and the precision (based on pooled standard deviation) 0.9‰ and 1.3‰. The line was designed for sample volumes of ca. 180 ml containing 0.5–1% CH4 and CO2, but can be adjusted to handle lower concentration and larger volume samples. This rapid and convenient method for the preparation of CH4 and CO2 in environmental samples for 14C AMS analysis should provide more opportunities for the use of 14C CH4 measurements in C cycle studies. 相似文献