Compositions and constituents of freshwater dissolved organic matter isolated by reverse osmosis

Dissolved organic matter (DOM) from riverine and lacustrine water was isolated using a reverse osmosis (RO) system. Solid-state ¹³C nuclear magnetic resonance (¹³C NMR) was used to quantitatively evaluate the compositions and constituents of DOM, which are compared with previous investigations on marine DOM. Results indicated that concentration factor (CF) was a key metric controlling yield and sorption of DOM on the RO system. The sorption was likely non-selective, based on the ¹³C NMR and δ¹³C analyses. Carbohydrates and lipids accounted for 25.0–41.5% and 30.2–46.3% of the identifiable DOM, followed by proteins (18.2–19.8%) and lignin (7.17–12.8%). The freshwater DOM contained much higher alkyl and aromatic C but lower alkoxyl and carboxyl C than marine DOM. The structural difference was not completely accounted for by using structure of high molecular weight (HMW) DOM, suggesting a size change involved in transformations of DOM during the transport from rivers to oceans.     

Seasonal δ13CDIC sourcing and geochemical flux in telogenetic epikarst of south-central Kentucky

Telogenetic epikarst carbon sourcing and transport processes and their associated hydrogeochemical responses are complex and dynamic. Carbon dioxide (CO₂) transport rates in the epikarst zone are often driven by hydrogeochemical responses, which influence carbonate dissolution and conduit formation. This study examines the influence of land use on carbon sourcing and carbonate dissolution kinetics through a comparative analysis of separate, but similar, epikarst systems in south-central Kentucky. The use of high-resolution hydrogeochemical data from multiple data loggers and isotope analysis from collected water samples reflects the processes within these epikarst aquifers, which are estimated to contribute significantly to bedrock dissolution. Results indicate that, in an agricultural setting, long-term variability and dissolution is governed by seasonal production of CO₂ . In a more urbanized, shallower epikarst system, land cover may affect CO₂ transport between the soil and underlying bedrock. This concentration of CO₂ potentially contributes to ongoing dissolution and conduit development, irrespective of seasonality. The observed responses in telogenetic epikarst systems seem to be more similar to eogenetic settings, which is suggested to be driven by CO₂ transport occurring independent of high matrix porosity. The results of this study indicate site-specific responses with respect to both geochemical and δ¹³C_DIC changes on a seasonal scale, despite regional geologic similarities. The results indicate that further comparative analyses between rural and urban landscapes in other karst settings is needed to delineate the impact of land use and seasonality on dissolution and carbon sourcing during karst formation processes. © 2019 John Wiley & Sons, Ltd.     

13kaBP以来滇池地区古环境演化

根据DC93一1孔孢粉组合、总有机碳（TOC）、总氮（TN）、碳氮比（C／N）、有机碳同位素δ13Corg、磁化率（χ）、频率磁化率（χfd）等资料,结合14C、210Pb和137Cs测年,滇池地区13ka以来的古环境演化历史经历了以下几个阶段：13—10．2kaBP．气候偏凉湿,湖水深度不大;10．2－7．5kaBP,气候向暖湿过渡．湖水渐深;7．5－4．0kaBP,气候暖湿,出热条件达到最佳配制,湖水也最深．6．5kaBP前后,气温最高,这一时段古气候状况存在次级波动;4．0－2．7kaBP,气候突转干旱．湖水最浅;2．7－1．7kaBP,气候温湿,湖面扩大,湖水变深;1．7kaBP,人类活动影响的加剧,使湖泊环境的变化更为复杂．     

Alkaline rocks of Samchampi-Samteran, District Karbi-Anglong, Assam, India

The Samchampi-Samteran alkaline igneous complex (SAC) is a near circular, plug-like body approximately 12 km² area and is emplaced into the Precambrian gneissic terrain of the Karbi Anglong district of Assam. The host rocks, which are exposed in immediate vicinity of the intrusion, comprise granite gneiss, migmatite, granodiorite, amphibolite, pegmatite and quartz veins. The SAC is composed of a wide variety of lithologies identified as syenitic fenite, magnetite ± perovskite ± apatite rock, alkali pyroxenite, ijolite-melteigite, carbonatite, nepheline syenite with leucocratic and mesocratic variants, phonolite, volcanic tuff, phosphatic rock and chert breccia. The magnetite ± perovskite ± apatite rock was generated as a cumulus phase owing to the partitioning of Ti, Fe at a shallow level magma chamber (not evolved DI = O1). The highly alkaline hydrous fluid activity indicated by the presence of strongly alkalic minerals in carbonatites and associated alkaline rocks suggests that the composition of original melt was more alkalic than those now found and represent a silica undersaturated ultramafic rock of carbonated olivine-poor nephelinite which splits with falling temperature into two immiscible fractions—one ultimately crystallises as alkali pyroxenite/ijolite and the other as carbonatite. The spatial distribution of varied lithotypes of SAC and their genetic relationships suggests that the silicate and carbonate melts, produced through liquid immiscibility, during ascent generated into an array of lithotypes and also reaction with the country rocks by alkali emanations produced fenitic aureoles (nephelinisation process). Isotopic studies (δ¹⁸O and δ¹³C) on carbonatites of Samchampi have indicated that the δ¹³C of the source magma is related to contamination from recycled carbon.     

Latitudinal and downcore (0–750 ka) changes in n-alkane chain lengths in the eastern equatorial Pacific

The n-alkane C₃₁/(C₂₉ + C₃₁) ratios from surface sediments in the eastern equatorial Pacific (EEP) exhibit higher values to the north and lower values to the south across the southern edge (2–4°N) of the Intertropical Convergence Zone (ITCZ). Since plants tend to synthesize longer chain length n-alkanes in response to elevated temperature and/or aridity, the higher C₃₁/(C₂₉ + C₃₁) ratios at northern sites suggest a higher contribution of vegetation under hot and/or dry conditions. This is consistent with the observation that northern sites receive higher levels of plant waxes transported by northeasterly trade winds from northern South America, where hot and dry conditions prevail. Furthermore, from a sediment core covering the past 750 ka (core HY04; 4°N, 95°W) we found that C₃₁/(C₂₉ + C₃₁) ratios exhibit a long-term decrease from MIS (marine oxygen isotope stage) 17 to 13. During this period, the zonal SST (sea-surface temperature) gradient in the equatorial Pacific increased, suggesting an increase in Walker circulation. Such intensified Walker circulation may have enhanced moisture advection from the equatorial Atlantic warm pool to the adjacent northern South America, causing arid regions in northern South America to contract, which may explain long-term decrease in n-alkane chain lengths.     

A study of the chemistry of pore fluids and authigenic carbonates in methane seep environments: Kodiak Trench, Hydrate Ridge, Monterey Bay, and Eel River Basin

Analyses of the chemical and isotopic composition of carbonates rocks recovered from methane seepage areas of the Kodiak Trench, Hydrate Ridge, Monterey Bay Clam Flats, and the Eel River Basin, coupled with the studies of the chemistry of the pore fluids, have shown that these carbonates have grown within the sediment column. Geochemical profiles of pore fluids show that, in deep water seeps (Kodiak Trench—4450 m; Monterey Bay—1000 m; Hydrate Ridge—650 m), δ¹³C (DIC) values are low (isotopically light), whereas in the Eel River area ( 350–500 m), δ¹³C (DIC) values are much higher (isotopically heavier). In all cases, the δ¹³C values indicate that processes of methane oxidation, associated with sulfate reduction, are dominant in the shallow sediments. Data on the isotopic composition of authigenic carbonates found at sites in Kodiak Trench, Eel River Basin South, and Eel River Basin North indicate a variable composition and origin in different geochemical environments. Some of the authigenic carbonates from the study sites show a trend in their δ¹³C values similar to those of the pore fluids obtained in their vicinity, suggesting formation at relatively shallow depths, but others indicate formation at greater sediment depths. The latter usually consist of high magnesium calcite or dolomite, which, from their high values of δ¹³C (up to 23‰;) and δ¹⁸O (up to 7.5‰), suggest formation in the deeper horizons of the sediments, in the zone of methanogenesis. These observations are in agreement with observations by other workers at Hydrate Ridge, in Monterey Bay, and in the Eel River Basin.     

琼东南盆地崖13-1气田陵三段沉积微相对储层非均质性及流动单元划分的影响

崖13-1气田陵三段是河控与潮控的辫状三角洲,主要储层沉积微相为分流河道、水下分流河道、河口坝、远砂坝及席状砂,其中河口坝的储层物性比分流河道和水下分流河道微相好,席状砂与远砂坝的物性相对较差,而各类正韵律河道与反韵律的砂坝决定了各垂向流动单元储层韵律特征。气田内的隔夹层与不同规模的海泛面相关,隔层以前三角洲泥为主,分布稳定,而夹层以分流间湾与水下分流间湾泥为主,分布较局限。结合沉积微相分布、储层非均质性及断层的分布,可以把气田区分为两个大区及6个流动单元,而南II、南III区仍可有较好的储层,但由于构造上处于低部位,含气前景还需进一步论证。     

Correlation between the bedded chert sequence of southwest Japan and δ13C excursion of carbonate sequence, and its significance to the Permian-Triassic mass extinction

Abstract Stratigraphic productivity variations of radiolarians below the Permian-Triassic boundary are examined with Ishiga Diagrams in bedded chert sequences of southwest Japan. The diagrams of two different outcrops, drawn from the thickness variation of chert beds, show common stratigraphic variation, which indicates the diagram is a useful tool for correlation of bedded chert sequence. The common stratigraphic productivity variation is also well correlated to a compiled δ¹³C excursion of shallow carbonate sequences. Bedded chert records a dramatic extinction event in a shallow surface zone of oceans below the Permian-Triassic boundary. The Permian-Triassic mass extinction is divided into three intervals based on the Ishiga Diagrams, the stratigraphic lithological variation of bedded chert sequences, and the δ¹³C curve. The preceding extinction interval in the late Djulfian stage was not as serious an event and the biosphere soon recovered. The event of the main extinction interval commenced in the Dorashamian stage and caused a serious destruction of the biosphere. An event of the aftermath interval during the Early Triassic caused a delay in the recovery from the main extinction interval.     

计算机I／O端口病毒的诊断与消除

计算机 I/O 端口病毒破坏并行口和 RS232串行口,致使打印机无法工作,双机通讯无法进行。本文据处理邯郸台网286微机 I/O 端口病毒的实践,剖析了该病毒的机理,提供了快速诊断和消除该病毒的方法,对于保障台网特别是华北遥测台网联网系统的正常运行具有实用意义。     

Environmental records of carbon in recent lake sediments

Based on careful sampling and accurate analysis of recent sediments in Lake Chenghai, this paper discusses the staggered positive/negative correlation between organic carbon (OC) concentration and inorganic carbon (IC) concentration. The result indicates that temperature change, and its induced relative changes are the main factors affecting the relationship between IC concentration, δ¹³C of carbonate and OC concentration. When temperature and its induced photosynthesis strength change control autochthonous calcite precipitation, OC concentration is positively correlated with IC concentration and δ¹³C of carbonate. When temperature and its induced physical/chemical changes dominate, OC concentration displays negative correlation with IC concentration and δ¹³C of carbonate. IC concentration and δ¹³C of carbonate in sediments of Lake Chenghai are good proxies for climatic warm/cold changes.