Biological and granulometric controls on sedimentary organic matter of an intertidal mudflat

A variety of measures of organic matter concentration and quality were made on samples collected from the top few mm of intertidal mudflat sediment over the course of a year, in order to assess the relative importance of biological and sedimentological influences on sedimentary organic matter. Winter and summer were times of relatively fine-grained sediment accumulation, caused by biological deposition or stabilization processes and resulting in higher organic matter concentrations. Stable carbon isotope and Br:C ratios indicated a planktonic source of bulk organic matter. Ratios of organic carbon to specific surface area of the sediments were consistent with an organic monolayer coverage of sediment grains. Correction for changing grain size during the year showed no change in the organic concentration per unit surface area, in spite of organic matter inputs by in situ primary production, buildup of heterotroph biomass and mucus coatings, and biodeposition of organic-rich seston. There were also no indications of changes in bulk organic quality, measured as hydrolyzable carbohydrates and amino acids, in response to these biological processes. It is concluded that biological processes on a seasonal time scale affect the bulk organic matter of these sediments via a modulation of grain size rather than creation or decay of organic matter.     

The exchange of organic carbon in basin mangrove forests in a southwest Florida estuary

The magnitude and seasonality of organic carbon exchange was estimated for two basin mangrove forests in Rookery Bay, Florida. Runoff and tidal inundation in the forests were seasonal with half the annual total of each occurring from August to October. In each forest there were 152 tides yr^?1 with a cumulative depth of about 12 m. Total organic carbon increased in bay waters exporting from the mangroves following a flood tide and peak concentrations were associated with export due to rainfall. The amount of net export from each basin forest was similar, although the concentration of organic carbon in each were different. Monthly net organic carbon export was proportional to the cumulative tidal amplitude within the forest. Total organic carbon export was 64 gC m^?2 yr^?1 and DOC was 75% of the total. A comparison of organic carbon export among riverine, fringe and basin mangroves suggests that tidal hydrology influences the proportion of litter fall that is exported from mangroves; and the magnitude of this organic carbon export from mangroves is related to the cumulative tidal amplitude within the forests.     

Dissolved organic carbon dynamics in two streams draining forested catchments at loch ard,Scotland

Dissolved organic carbon (DOC) was measured at four or eight hour intervals between mid-1989 and mid-1991 in two catchments in west central Scotland. The experimental catchment had been recently clear-felled and the control remained under forest. The amount of DOC varied during individual storm events following the stream hydro-graph. Maximum variations were found in the summer half-year and in the clear-felled catchment. There was also evidence of the exhaustion of DOC in the later events of a sequence. Differences between the catchments were related to catchment characteristics and to land-use change. The reduced magnitude of variation in DOC with discharge in the control stream was due to the influence of a wetland area through which the stream flowed. The mean DOC concentrations were similar in the two streams and annual exports were 15 g m^?2 from the control and 16g m^?2 from the felled catchment. The stream draining the clear-felled catchment had greater high flow DOC concentrations in the summer half-year, probably due to the effect of greater mean summer temperatures on DOC release and of the greater supply of organic debris in the stream channel.     

载荷试验确定基床系数修正方法的讨论

Winkler地基模型是目前工程界应用最广的一种地基模型，但对其关键参数——基床系数k的确定，许多文献的表述并不一致。该文在大量试验资料的基础上，通过对该问题的深入研究，阐明了通过载荷试验确定基床系数修正方法的有关概念。对于砂性土地基，载荷板试验得出的基准基床系数仅需要进行基础大小修正，而对于粘性土地基，则需要进行基础大小和基础形状两项修正。     

有机碳同位素示踪古环境变化研究

对有机碳同位素示踪环境变化的原理、研究对象、取得的进展和存在的问题等进行了详细研究，认识到C～H键比C-O键有利于富集^12C，从而导致生物或有机碳δ^13C为极低的负值，使有机碳与无机碳之间存在显著的碳同位素差异。光合作用类型的不同使植物分为C3，C4和CAM3种类群，并导致不同类群的植物具有不同的碳同位素组成，C3植物δ^13C=-20‰～-32‰，平均-28‰，而C4植物δ^13C=-9‰～-17‰，平均-14‰。气候环境的差异影响了光合作用的类型和强度，使不同环境的植物类群特征不同，不仅造成植物组合的碳同位素组成不同，而且导致不同食性的动物牙齿等化石的碳同位素组成的差异，甚至相应的无机碳同位素的变化，因此生物链及其衍生物的碳同位素研究也就成为反演某一地区或某一时期气候环境的有效手段。被作为研究对象的地质记录可分为有机和无机两类，有机类主要包括树轮等植物化石、牙齿等动物化石、煤等陆相沉积有机质、海相沉积有机质、土壤(前者的衍生物)，这些研究对象分别适合于目的不同的环境研究，并获得了较好的效果。进而发现有机碳同位素在研究重大生物灭绝事件、C4植物起源、地球早期生命起源、地外生命存在与否、矿产资源形成时的有机质作用等问题上将有重要作为。     

Ecological significance of alkaline phosphatase activity and phosphatase-hydrolyzed phosphorus in the northern part of Gamak Bay, Korea

We investigated the ecological significance of alkaline phsophatase (APase) and alkaline phosphatase-hydrolyzable phosphorus (APHP) in the northern part of Gamak Bay, Korea. APase activity was detectable throughout the year, and dissolved inorganic phosphorus (DIP) concentration and APase activity are highly correlated and can be regarded as an indicator of DIP-limiting conditions. Also, a strong linear positive correlation between APase activity and Chl a concentration indicated that the major part of APase activity may have been induced by phytoplanktons. The APHP proportion in dissolved organic phosphorus (DOP) was above ca. 30% from winter to spring and below ca. 15% from summer to autumn due to freshwater discharge and uptake by phytoplankton. APHP may play an important role in species competition in coastal area such as northern part of Gamak Bay where DIP is limiting. Thus, APase induction by phytoplanktons may be ecologically significant, allowing dominance by these organisms under DIP-limiting conditions.     

湘、黔下寒武统黑色岩系型Ni、Mo矿床中有机质与PGE成矿作用研究

湘、黔地区张家界、遵义一带分布有黑色岩系型Ni-Mo-PGE矿床,测试分析表明黑色页岩样品铂族元素含量特征参数∑PGE、Ln(Pd/Pt)、(Ru/Ir)×(Pd/Pt)、Ln[(Ru/Ir)×(Pd/Pt)]均与有机质含量特征参数有较好的相关性.趋势分析显示,铂族元素含量特征参数Ln[(Ru/Ir)×(Pd/Pt)]与总有机碳含量特征参数Ln(Corg)有很好的线性相关,线性相关公式为y=0.4762x-1.1316,相关系数R为0.7584,说明该参数为一稳定性参数,主要受有机质总量决定,集中反映了生物制约性.而与湖南张家界样品有机碳含量Ln(Corg)与铂族元素含量∑PGE同步正消长关系不一样,即贵州遵义地区铂族元素总量∑PGE与有机碳含量的相关性表现出的不一致的规律,可以解释为后生期的热事件(印支海西期,Rb-Sr等时线年龄277±37Ma)导致有机质干酪根的高成熟化、大量生过气(C>2%)和石墨化趋势,或者说是芳构化效应改变了源岩有机质而导致了有机质的损耗.     

冀北—辽西早白垩世沉积有机质特征与古气候环境演变

本文对冀北—辽西地区早白垩世沉积盆地富有机质沉积岩进行了初步有机地球化学分析研究。结果显示,冀北—辽西沉积盆沉积有机质特征在时间和空间上存在很大差异,代表白垩系早期沉积的滦平盆地大北沟组有机质丰度低,这不仅显示其所代表的沉积相带不利于有机质的聚集,也反映了当时生物不够繁盛;大店子组时期沉积相带发生了变化,有机质类型随着发生了变化,丰度有所增高,但总体上显示环境条件不利于生物的发育和繁盛。到了桥头组和义县组沉积岩有机质丰度大幅升高,表明生物界非常繁盛,古气候环境有利于有机质的大量生成和堆积,总体上反映了温湿的气候条件;但同时也存在较为频繁或交替性寒冷气候波动,具体的古气候环境状态尚需进一步深入研究。     

南海东北部冷泉区沉积物中有机质来源的生物标志物分析与环境指示意义

Multi-biomarker indexes were analyzed for two piston cores from potential cold seep areas of the South China Sea off southwestern Taiwan. Total organic carbon(TOC) normalized terrestrial(n-alkanes) and marine(brassicasterol, dinosterol, alkenones and iso-GDGTs) biomarker contents and ratios(TMBR, 1/Pmar-aq, BIT) were used to evaluate the contributions of terrestrial and marine organic matter(TOM and MOM respectively) to the sedimentary organic matter, indicating that MOM dominated the organic sources in Core MD052911 and the sedimentary organic matter in Core ORI-_(86)0-22 was mainly derived from terrestrial inputs, and different morphologies were the likely reason for TOM percentage differences. BIT results suggested that river-transported terrestrial soil organic matter was not a major source of TOM of sedimentary organic matter around these settings.Diagnostic biomarkers for methane-oxidizing archaea(MOA) were only detected in one sample at 172 cm depth of Core ORI-_(86)0-22, with abnormally high iso-GDGTs content and Methane Index(MI) value(0.94). These results indicated high anaerobic oxidation of methane(AOM) activities at or around 172 cm in Core ORI-_(86)0-22.However in Core MD052911, MOA biomarkers were not detected and MI values were lower(0.19–0.38), indicated insignificant contributions of iso-GDGTs from methanotrophic archaea and the absence of significant AOM activities. Biomarker results thus indicated that the discontinuous upward methane seepage and insufficient methane flux could not induce high AOM activities in our sampling sites. In addition, the different patterns of TEX_(86) and U_(37)~(K′) temperature in two cores suggested that AOM activities affected TEX_(86)37 temperature estimates with lower values in Core ORI-_(86)0-22, but not significantly on TEX_(86) temperature estimates in Core MD052911.     

The potential of contribution of mangrove-derived organic matter in intertidal sediments as a proxy of mangrove development in the northern Beibu Gulf

University of Maryland, College Park