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Contrasting lipid biomarkers in mountain rivers in the Nepal Himalayas: Organic matter characteristics and contribution to the fluvial carbon pool

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Geoscience Frontiers 2021年第6期12卷 1-15页

作者： Rajendra Bhandari Joyanto Routh Subodh Sharma Rajendra Joshi Department of Thematic Studies–Environmental Change Linköping UniversitySweden Aquatic Ecology Center Kathmandu UniversityNepal Department of Environmental Science and Engineering Kathmandu UniversityNepal Department of Chemical Science and Engineering Kathmandu UniversityNepal

The Nepal Himalayas is the source of many glacial and spring-fed river systems crisscrossing the mountainous *** is an increasing recognition of small mountain rivers(SMRs)to have a significant combined export of dissolved and particulate organic carbon to the global carbon *** analyzed fluvial sediments from two SMRs and compared the results with two large mountain rivers(LMRs)in *** investigated the organic matter(OM),its compositional variability,and seasonal export using a suite of lipid biomarkers,namely n-alkanes,n-alkanoic acids,n-alkanols,and *** SMRs indicated a similarity in lipid distribution and were affected by a strong seasonal *** LMRs showed a distinct contrast in the distribution of lipids in suspended *** sediments in SMRs were derived from diverse sources with weak terrigenous dominance all-year-round compared to the suspended *** lipids(n-alkanoic acids and n-alkanols)were the major constituents in SMR sediments,indicating better *** contrast,n-alkane concentration dominated over other fractions in suspended sediments retrieved from *** biomarker trends differentiate SMRs from LMRs with lower transformed/degraded OM in SMRs.A common observation was the strong presence of even carbon compounds in short-chain n-alkanes in SMR bedload sediments and their predominance in suspended sediments in *** an unusual trend is attributed to specific biomarker sources from the catchment and ongoing processes in fluvial *** colonized by fungal species under moist acidic conditions and autochthonous bacteria contributes to the organic matter pool in shallow *** LMRs,the contribution from thermally mature sedimentary hydrocarbons and the diagenetic reduction of nalkanoic acids to n-alkanes are additional contributors to the allochthonous carbon *** differences in lipid concentrations,their distribution,seasonality,and the size of rivers suggest differential

关键词： fluvial sediments Bedload Suspended load Monsoon Biomarkers Biogeochemistry

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Chemical weathering in Malay Peninsula and North Borneo:Clay mineralogy and element geochemistry of river surface sediments

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Science China Earth Sciences 2011年第2期54卷 272-282页

作者： WANG Hao LIU ZhiFei Edlic SATHIAMURTHY Christophe COLIN LI JianRu ZHAO YuLong State Key Laboratory of Marine Geology Tongji University Shanghai 200092 China Institute of Oceanography University Malaysia Terengganu Kuala Terengganu 21030 Malaysia Laboratoire IDES Bat. 504 UMR 8148 CNRS Universite de Paris XI Orsay 91405 France

Weathering products of silicate rocks are particularly useful for evaluating the continental chemical weathering on the Earth's surface and its *** mineralogy and major-element geochemistry of surface sediment samples collected in major rivers of Malay Peninsula and North Borneo in the tropical Southeast Asian region are used to study the present chemical weathering process and its controlling factors of tropical *** results indicate that the clay mineral assemblage in Malay Peninsula consists dominantly of kaolinite(average 80%) and minor illite(average 17%),almost without chlorite and smectite,whereas in North Borneo it consists mainly of illite and chlorite,with minor amounts of kaolinite(average 14%) and no *** contents of illite and chlorite in both Northwest and Northeast Borneo are 84% and 87%,***-element geochemical results of both bulk and clay-fraction sediments show intensive chemical weathering degree for both ***,the chemical weathering degree is gradually strengthened from Northeast Borneo,Northwest Borneo,to Malay Peninsula,and it is extremely intensive in Malay *** results indicate that,in the tropical Southeast Asian region exampled by Malay Peninsula and Borneo,climatic condition of tropical warm temperature and East Asian monsoon rainfall is the first-order controlling factor on the chemical weathering,resulting in intensive chemical weathering throughout tropical areas,and tectonic activity and lithology of parent rocks are subordinate factors,which still have an important impact on the weathering products,forming completely different clay mineral assemblages between Malay Peninsula and Borneo.

关键词： clay minerals major elements fluvial sediments chemical weathering Malay Peninsula Borneo

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Variations in total organic carbon and grain size distribution in ephemeral river sediments in western India

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International Journal of Sediment Research 2011年第2期26卷 239-246页

作者： J.DINAKARAN N.S.R.KRISHNAYYA Ecology Laboratory Department of BotanyFaculty of ScienceM.S.University of Baroda

Total organic carbon(TOC) and grain size distribution(sand,silt,and clay) in the ephemeral Mahi River(western India) sediments were measured to look at their effectiveness in understanding the late Quaternary monsoon *** sites spread across the alluvial zone and three sites from the estuarine zone were *** concentration in the sediments of the alluvial and estuarine zone sites ranged between 0.04 and 0.39%and 0.04 and 0.23%,*** was observed that grain size differed significantly at the alluvial zone sites,whereas an uniform trend was found in the estuarine zone *** study indicated that low concentration of TOC and coarse size fractions(sand) in sediments were well correlated with available records of arid/weaker palaeomonsoon periods,whereas higher concentration of TOC and fine grain size fractions(silt + clay) in sediments were well correlated with available records of enhanced palaeomonsoon periods of the ephemeral Mahi *** concentrations of TOC and fine grain size particles in sediments at the estuarine zone sites are attributed to the backwater in the system,deeper sedimentation,and/or greater decomposition *** is concluded that,TOC and grain size distributions in the ephemeraL river sediments are simple and effective parameters to develop an understanding about late Quaternary monsoon conditions in ephemeral rivers.

关键词： Ephemeral river fluvial sediments Total organic carbon Particle size distribution Quaternary monsoon

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