Carbone organique total (COT) et magnésium (Mg2+) : deux traceurs complémentaires du temps de séjour dans l'aquifère karstique

The Total Organic Carbon (TOC) is an interesting tracer of fast infiltration within karstic systems [3,7]. Regular sampling on several aquifers, from the experimental site of Vaucluse, made it possible to demonstrate the high sensitivity of this tracer compared with other commonly used chemical and isotopic tracers in karstic hydrogeology. The complementarity of magnesium, indicator of the residence time of water within the system, and TOC appears as a relevant tool in order to characterize the behaviour of the aquifer, to differentiate the water types which participate to the karstic flow (fast infiltration, unsaturated zone, saturated zone) and then, to evaluate their vulnerability.     

The Geochemical Context of Gas Hydrate in the Eastern Nankai Trough

Abstract. Geochemical studies for gas hydrate, gas and organic matter collected from gas hydrate research wells drilled at the landward side of the eastern Nankai Trough, offshore Tokai, Japan, are reported. Organic matter in the 2355 m marine sediments drilled to Eocene is mainly composed of Type III kerogen with both marine and terrigenous organic input. The gas hydrate-bearing shallow sediments are immature for hydrocarbon generation, whereas the sediments below 2100 mbsf are thermally mature. The origins of gases change from microbial to thermogenic at around 1500 mbsf.
Carbon isotope compositions of CH₄ and CO₂, and hydrocarbon compositions consistently suggest that the CH₄ in the gas hydrate-bearing sediments is generated by microbial reduction of CO₂. The δ¹³C depth-profiles of CH₄ and CO₂ suggest that the microbial methanogenesis is less active in the Nankai Trough sediments compared with other gas hydrate-bearing sediments where solid gas hydrate samples of microbial origin were recovered. Since in situ generative-potential of microbial methane in the Nankai Trough sediments is interpreted to be low due to the low total organic carbon content (0.5 % on the average) in the gas hydrate-bearing shallow sediments, upward migration of microbial methane and selective accumulation into permeable sands should be necessary for the high concentration of gas hydrate in discrete sand layers.     

TOC-Bestimmung in Schlämmen,Sedimenten und Schwebstoffen — Beschreibung des Verfahrens und begleitender Qualitätssicherungsmaßnahmen Determination of TOC in Sludge,Sediment and Suspended Solids — Description of the Analytical Procedure and Accompanying Quality Control Procedures

The total organic carbon (TOC) is calculated by subtracting the inorganic carbon (IC) from the total carbon (TC). For TC determination, the carbon in a sample is completely converted to CO₂ by decomposition/combustion in an oxygen stream. To determine IC, inorganic carbon (carbonate) is liberated by adding acid and by heating in an oxygen stream. In both cases, CO₂ is quantified by infrared spectrometry. To gain reliable and reproducable results for sludge, sediment and suspended solids, at least the following conditions have to be met: particle size has to be smaller than 200 μm; weightout has to be selected in such a way, that the signal area is not below and the signal maximum is not above specific instrument dependent parameters; combustion/decomposition has to be complete (TC: ≥ 1300 °C, no soot) and rules for analytical quality assurance must be followed. The TC quantification of calcium carbonate is used for system calibration. Daily working procedures include calibration checks by mean control charts for TC determination of calcium carbonate and IC determination of sodium carbonate as well as for control sediment TC and IC quantifications.     

滇池流域宝象河水库沉积物中有机碳的来源

通过对滇池流域宝象河水库沉积物TOC、TN、C/N、δ13C及粒度等指标的测定,分析了沉积物中有机碳的主要来源及其变化趋势。结果表明:水体中不同位置沉积物有机碳来源并不相同,距三岔河入库河口相对较近的沉积柱芯A中C/N比值介于2.93~11.73,δ13C值介于-23.66‰~-21.78‰,有机碳主要来源于水生生物,陆源输入贡献较小,有机碳含量受粒径大小影响显著;距三岔河入库河口相对较远的沉积柱芯B中,其TOC和TN含量较高,分别介于14.62~24.93 g?kg-1和2.11~3.3 g?kg-1,δ13C值变化范围为-28.36‰~-26.36‰,粒度以黏土和细粉砂为主,有机碳主要来源于水库周边陆源输入,受人类活动影响强烈。     

The Effects of Nutrients on Natural Organic Matter (NOM) Removal in Biological Activated Carbon (BAC) Filtration

Effective biodegradation of organic compounds is one of the major objectives while optimizing biological drinking water treatment processes. Enhancing the biological activated carbon (BAC) filter performance with nutrient addition was studied using chemically pre-treated and ozonated lake water. Three parallel pilot-scale biofilters were operated: one with phosphorus addition, one with a mixture of inorganic nutrients addition, and one as a reference. The addition of nutrients had no statistically significant influence on the natural organic matter (NOM) removal when monitored by total organic carbon (TOC), UV absorbance, and assimilable organic carbon (AOC). However, the addition of nutrients significantly increased the heterotrophic plate count (HPC) bacteria of the filter effluent, while the adenosine triphosphate (ATP) analysis of the attached bacteria did not show any increase in BAC filters. It seemed that in BAC filters the bacterial growth was limited by phosphorus, but the increased bacteria could not attach themselves during the relatively short acclimatization period.     

鸭绿江河口西岸潮滩沉积物有机质对流域变化的响应

河流颗粒有机质提供了陆地碳循环的重要信息以及人类活动的记录,通过河口地区沉积物有机质组成,可反映流域变化及海陆间相互作用。2010-2011年分两次于鸭绿江河口西岸潮滩采集柱样4根及表层样23个。对样品进行有机质碳氮总量(TOC、TN)、碳氮同位素(δ13C、δ15 N)及沉积物粒度测试。分析结果表明,由河口向西,有机质受改造程度加深且来源逐渐复杂化,致TOC/TN与δ13C的相关性逐渐降低,δ15 N与沉积物粒度的相关性也随之降低。文中以δ13C为主线探讨沉积物有机质的来源及运移,TOC/TN作为辅助,δ15 N则用于指示生化条件的改变。柱样的δ13 C分布与河流入海输沙密切相关,水库对入海泥沙的拦截,致河口潮滩沉积速率减缓,从而增加了沉积物中海源有机质的含量,δ13C随之增加。潮滩西侧柱样的δ15 N增加指示了生活工业污水的大量排放。此外,表层样δ13C分布的方向性,指示了西水道门口处的快速堆积及潮下带物质的向岸运移,并在西岸潮滩向岸一侧富集。     

Dynamics and fluxes of organic carbon and nitrogen in two Guiana Shield river basins impacted by deforestation and mining activities

Deforestation and mining activities have proven to be very damaging to rivers because these activities disturb the environmental characteristics of rivers. Thus, the concentrations of dissolved organic carbon (DOC), particulate organic carbon (POC), particulate nitrogen (PN), and Chlorophyll‐a (Chl‐a) were measured monthly during 2 hydrological years in the Maroni and Oyapock Rivers to assess the dynamics and fluxes of organic carbon and nitrogen in these 2 Guiana Shield basins, which have been strongly (Maroni) and weakly (Oyapock) impacted by deforestation and mining activities. The 2‐year time series show that DOC, POC, PN, and Chl‐a concentrations vary seasonally with discharge in both rivers, indicating a hydrologically dominated control. Temporal patterns of DOC, POC, and PN indicate that these variables show maximum concentrations in rising waters due to the yield of organic matter and nitrogen accumulated in soils, which are incorporated into the rivers during rainfall. However, the Chl‐a concentrations were at a maximum during low‐water stages. The C/N and C/Chl‐a ratios also showed a seasonal trend, with lower values during the low water periods due to an increase in algal biomass. During high water, the POC in both rivers is the result of terrestrial organic matter, whereas during low‐water autochthonous organic matter can reach up to 34% of the POC. The mean annual fluxes of TOC and PN were higher (4.56 × 10⁵ tonC year^?1 and 1.77 × 10⁴ tonN year^?1, respectively) in the Maroni River than those (1.84 × 10⁵ tonC year^?1 and 0.54 × 10⁴ tonN year^?1, respectively) in the Oyapock River. However, the specific fluxes of DOC, POC, and PN from both basins were nearly the same. Although gold mining activities are performed in both basins, there is no conclusive evidence regarding the impact of these activities on the dynamics of organic matter and particulate nitrogen in the Maroni and Oyapock Rivers.     

东海典型港湾表层沉积物中主要生源要素分布及污染状况分析

分别于2016年11月、2018年4月、2016年7月、2014年11月采集了福建东山湾、福宁湾、浙江象山港以及江苏大丰港52个表层沉积物样品,分析了表层沉积物中总有机碳(TOC)、总氮(TN)、总磷(TP)、生物硅(BSi)、有机质(OM)及含水率(MC)的含量。TOC、TN、TP、BSi、OM及MC含量分别为:0.35%～1.52%,0.08%～0.32%,0.020%～0.074%,0.28%～1.89%,1.86%～9.53%,19.55%～52.55%。福宁湾TN和BSi含量较高,东山湾TP含量较高,而象山港TOC含量较高。从元素之间的摩尔比来看,本研究中各港湾沉积物中的TOC均主要来自浮游植物等水生生物,而TOC的分解和再生速率应远高于BSi的溶解速率。根据主要生源要素污染评价标准,东山湾海域污染较严重,TN、TP、TOC均达到Ⅱ级污染标准。福宁湾及象山港TN、TOC均为Ⅱ级污染。而大丰湾海域总体污染较轻,只有TN超过Ⅱ级标准。     

印度页岩气发展现状及勘探方法综述

印度作为亚洲少数几个发现了页岩气的国家之一,有着较大的资源潜力。据EIA估算,印度页岩气原地总储量为8.3×1012m3,可采储量为1.8×1012 m3。页岩气勘探工作主要分为六个步骤,其中尤为注重地球化学、地球物理和力学性质的研究。干酪根成熟度的确定主要采用镜质体反射率与声波时差的经验关系计算,TOC值的计算综合运用干酪根体积法、电阻率-孔隙度交会法,核磁共振和密度测井相结合的方法。