若尔盖RM孔有机碳、总氮和碳氮比值的垂直分布     

钱君龙  吉磊  王苏民 《山地学报》1996,(4)

分析了ＲＭ孔岩心样５９５个．孔内总有机碳含量ＴＯＣ变动范围较大，低者１—２％，高者１０—２０％；总氮含量ＴＮ多０．１—０．２％，少数０．４—０．８％；碳氮比值Ｃ／Ｎ较低（≤８）段属浅湖沉积，Ｃ／Ｎ较高（＞８）段属湖滨沼泽沉积；ＴＯＣ，ＴＮ和Ｃ／Ｎ明显有四个波动段．  相似文献   

Limnological conditions in a subarctic lake (northern Québec, Canada) during the late Holocene: analyses based on fossil diatoms     

Karin Ponader  Reinhard Pienitz  Warwick Vincent  Konrad Gajewski 《Journal of Paleolimnology》2002,27(3):353-366

A fossil diatom record covering the past 3000 cal. years BP wasanalyzed from a small lake in northwestern Québec near the northernlimit of present-day tree-line. Fragilaria virescens var.exigua Grunow in Van Heurck was the dominant speciesthroughout the core with abundances ranging between 13–35% of thetotal valve count. There was a replacement of alkaliphilous taxa byacidophilous taxa beginning ca. 1300 cal. yr ago, probably reflectinglong-term, natural acidification processes. A diatom-based transfer functionwas used to provide quantitative estimates of variations in lakewater dissolvedorganic carbon (DOC). These inferred values showed that DOC concentrations haveremained stable over the past 3000 years (mean ± S.D. = 5 ± 0.43 mg C l^–1), suggesting relatively constant allochthonouscarbon inputs and underwater light conditions during the late Holocene. Thereconstructed DOC data were compared to the palynological record from the samelake. Our study indicates that, in contrast to paleolimnological records fromlakes in central and western Canada, climatic variations and associatedvegetational shifts have been too subtle to cause pronounced variations in DOCin this northern Québec site.  相似文献   

Zum Einfluß des gelösten organischen Kohlenstoffs (DOC) auf das Mobilitätsverhalten einiger Pestizide     

S. A. Huber  I. Scheunert  U. Drfler  F. H. Frimmel 《洁净——土壤、空气、水》1992,20(2):74-81

Interaction of Dissolved Organic Carbon (DOC) with some Pesticides in Aqueous Systems. Several independent methods (batch sorption studies, chromatography) were used to study interactions of natural organic matter with two pesticides (Terbutylazine, Pendimethaline). After 24 hrs contact time, significant amounts of pesticides were (in part irreversibly) associated with the colloidal and high molecular weight fraction. The interactions were observed for soil organic matter and groundwater-DOC. It is assumed that the mobility of pesticides in natural systems is strongly influenced by interactions of this kind. The hypothesis is supported by chromatographic measurements of DOC with ¹⁴C-labeled Pendimethaline in lysimeter leachates.  相似文献   

Release of dissolved organic carbon from upland peat     

F. Worrall  T. P. Burt  R. Y. Jaeban  J. Warburton  R. Shedden 《水文研究》2002,16(17):3487-3504

This study examines the release of dissolved organic carbon (DOC) from upland peat during the period of the autumn flushing. Hydroclimatic conditions were monitored in conjunction with measurements of absorbance and the E4/E6 ratio of the stream draining an 11·4 km² upland peat catchment in northern England. During two months of monitoring the effects of 67 separate rainfall events were examined showing that:

• The peat behaves hydrologically as if it were a two end‐member system consisting of old, interevent, and new, event, water. Runoff is initiated by percolation excess of new water at the acrotelm–catotelm interface.
• The discharge of dissolved organic matter behaves like a three end‐member system with the between‐event water being low in DOC and storm events being characterized by two types of water. Initial runoff being characterized by new water rich in DOC that gives way to new water depleted in DOC. This transition can be ascribed to the runoff progressing from throughflow within the acrotelm progressing to saturation‐excess overland flow.
• Depletion of DOC during storm events is accompanied by a change in the character of the DOC as the E4/E6 ratio changes. This suggests that the decrease in DOC during events is the result of exhaustion of reserves rather than changes in the flowpaths being utilized by runoff.
• The amount of carbon released in any event is critically dependent upon the time between events during which oxidation processes generate a reservoir of available carbon. Production of available carbon in the catchment is as high as 4·5 g C per day per m³ of peat, suggesting a turnover rate of peat of the order of 42 years. Copyright © 2002 John Wiley & Sons, Ltd.

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Controls on old and new water contributions to stream flow at some nested catchments in Vermont,USA   总被引：1，自引：0，他引：1  

James B. Shanley  Carol Kendall  Thor E. Smith  David M. Wolock  Jeffrey J. McDonnell 《水文研究》2002,16(3):589-609

Factors controlling the partitioning of old and new water contributions to stream flow were investigated for three events in four catchments (three of which were nested) at Sleepers River Research Watershed in Danville, Vermont. In the 1993 snowmelt period, two‐component isotopic hydrograph separations showed that new water (meltwater) inputs to the stream ranged widely from 41 to 74%, and increased with catchment size (41 to 11 125 ha) (with one exception) and with open land cover (0–73%). Peak dissolved organic carbon concentrations and relative alkalinity dilution in stream water ranked in the same order among catchments as the new water fractions, suggesting that new water followed shallow flow paths. During the 1994 snowmelt, despite similar timing and magnitude of melt inputs, the new‐water contribution to stream flow ranged only from 30 to 36% in the four catchments. We conclude that the uncommonly high and variable new water fractions in streamwater during the 1993 melt were caused by direct runoff of meltwater over frozen ground, which was prevalent in open land areas during the 1993 winter. In a high‐intensity summer rainstorm in 1993, new water fractions were smaller relative to the 1993 snowmelt, ranging from 28 to 46%, but they ranked in the identical catchment order. Reconciliation of the contrasting patterns of new–old water partitioning in the three events appears to require an explanation that invokes multiple processes and effects, including:

• 1. topographically controlled increase in surface‐saturated area with increasing catchment size;
• 2. direct runoff over frozen ground;
• 3. low infiltration in agriculturally compacted soils;
• 4. differences in soil transmissivity, which may be more relevant under dry antecedent conditions.

These data highlight some of the difficulties faced by catchment hydrologists in formulating a theory of runoff generation at varying basin scales. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Origin of Dissolved Organic Carbon Studied by UV‐vis Spectroscopy     

Snia Regina Giancoli Barreto  Jorge Nozaki  Wagner J. Barreto 《洁净——土壤、空气、水》2003,31(6):513-518

Dissolved organic carbon (DOC) distributions in water from Lake Ipê, MS, Brazil, were investigated. The samplings were performed monthly (surface, 1 m depth, and bottom) from June 1999 to June 2000. Absorbance at 285 nm and DOC concentrations in mg dm^—3, p(DOC), were highly correlated for the three depths. 77% of the surface, 85% for 1 m and bottom samples presented a variation between 20 dm³ g^—1 cm^—1 and 50 dm³ g^—1 cm^—1 of A(285 nm)/p(DOC), that characterizes the dissolved organic matter in lake water as essentially fulvic. The ratio A(254 nm)/p(DOC) was also sensitive for fulvic matter, and an A(250 nm)/A(365 nm) = 4 ratio was characteristic of strongly colored waters. The ratios A(436 nm)/p(DOC) for the three depths also showed a significant correlation. The predominance of fulvic acid is explained by environmental characteristics such as the tropical climate, temperatures above 18 °C, and the lake environment. It was demonstrated that the variation in the water carbon content due to different compartments in the lake can be monitored by UV‐vis spectroscopy ratios.  相似文献   

Seasonal changes in iron transport and nature of dissolved organic matter in a humic river in northern Finland     

Kaisa Heikkinen 《地球表面变化过程与地形》1990,15(7):583-596

Changes in the concentration of iron and dissolved organic matter (DOM), and in the colour and fluorescence properties in the River Kiiminkijoki were investigated as functions of the seasonal flow regime over a two-year period. The iron concentration in filtrates and the ratio of Fe to DOC in the river increased under low flow conditions and decreased during the flood periods. The colour of the dissolved organic matter increased with increasing iron content, the effect being more pronounced during the warm period of the year than in winter. The ratio of fluorescence to DOC increased during the warm period of the year but not in winter, and decreased rapidly with discharge at the beginning of the flood period in autumn. The results give indications of the origin, formation, nature, and fate of the DOM in the river water. Temperature-dependent microbiological processes in the formation and sedimentation of iron-organic colloids seem to be important. Estimates are given for the amounts and transport rates of iron discharged into the Gulf of Bothnia by the river.  相似文献   

Chemical characterization of DOM in channels of a seasonal wetland   总被引：3，自引：0，他引：3  

Natalie Mladenov  Diane M. McKnight  Stephan A. Macko  Marnie Norris  Rose M. Cory  Lars Ramberg 《Aquatic Sciences - Research Across Boundaries》2007,69(4):456-471

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大兴安岭秋季冻结期土壤水热变化对多年冻土泥炭地可溶性有机碳的影响北大核心CSCD     

孙超峰  宋立全  臧淑英  焦亚青  鲁博权 《冰川冻土》2022,44(2):402-414

土壤温度和含水量是影响可溶性有机碳(DOC)变化的重要因素。然而,多年冻土泥炭地土壤DOC变化对秋季冻结期土壤水热变化的响应尚不明确。本研究选取大兴安岭3种多年冻土泥炭地[小叶章泥炭地(CP)、兴安落叶松-泥炭藓泥炭地(LP)、白毛羊胡子苔草泥炭地(EP)]作为研究对象,开展野外原位试验探究秋季冻结期土壤水热变化对多年冻土泥炭地土壤DOC变化的影响。结果表明:秋季冻结期土壤DOC含量表现为EP>CP>LP,平均含量分别为83.99、45.75和43.13mg·L^(-1)。在秋季冻结前期3种类型多年冻土泥炭地土壤DOC含量均呈波动下降趋势,中、后期CP,LP土壤DOC变化较平缓。在秋季冻结前期,CP整体土壤DOC含量随浅层土壤温度的降低而减少;在后期CP浅层和整体土壤DOC含量随浅层土壤含水量的增加而增加。在秋季冻结中期,LP浅层土壤温度升高和含水量的减少,降低了土壤DOC含量;LP整体土壤DOC的变化随着浅层温度的升高逐渐降低。在秋季冻结后期,EP深层和整体土壤DOC含量随深层含水量增加而增加。在整个秋季冻结期,LP浅层土壤DOC主要受地表温度驱动,深层土壤DOC则主要受深层含水量的影响;整体土壤DOC则受地表温度影响较大。研究表明秋季冻结期多年冻土泥炭地土壤水热变化驱动土壤DOC含量的变化。研究结果为多年冻土区碳循环和“双碳”背景下的碳排放研究提供基础科学数据。  相似文献   

海水中溶解有机碳（DOC）的测定   总被引：18，自引：0，他引：18  

宋金明  詹滨秋 《海洋湖沼通报》1992,(1):21-27

本文论述了海水中溶解有机碳(DOC)的测定方法,对DOC的测定原理及氧化方法进行了讨论,并提出了妨碍海水中DOC测定准确度提高的因素,这对于建立高准确度和精密度的新分析方法具有重要的意义。  相似文献