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1.
This study assesses a simple sediment source tracing method using major- (Al, Ca, Fe, K, Mg, Mn, Na, P, Si, Ti) and trace-element (Ba, Be, Ce, Co, Cr, Mo, Nd, Pb, Sr, Th, V, Y, Zn) signatures of stream suspended particulate matter (SPM), bed sediments and soils in a small agricultural catchment in NE Scotland. Whilst most erosion studies characterise the large amounts of material mobilised at the highest flows, this study aimed to assess properties of sediments during moderate to low flow periods. These occur more frequent than intense storms and are important in linking stream sediments, near-channel sources and aquatic ecosystem impacts. Data were transformed by multivariate statistical methods to compare elemental signatures of SPM (ranging from 3 to 53 mg L−1 in the stream) and stream bed sediments with a limited number of near-channel source soils. Increased concentrations of Ce, Nd, Th and Y in subsoils contributed to the ability to discriminate between surface fieldslope and stream bank erosion sources. Stream bed sediments showed close matches with compositions of stream bank and arable surface soils, but signatures of SPM differed greatly from any of the sources. Large concentrations of Cr, Pb and Zn in SPM, particularly during summer (677, 177 and 661 mg kg−1, respectively) exceeded water quality standards and were linked to an accumulation of trace elements associated with biological material. The potential for within-stream alteration of SPM in relation to erosion sources was confirmed by changes in the nature of the SPM organic matter observed by IR spectroscopy. Thus the potential is shown for multi-element signatures to give information on catchment sediment sources to aid land management decisions, given careful consideration of the effects of in-stream alteration of eroded material. However, this combined information may be beneficial to process understanding linking land use and stream ecosystems at critical ecological periods. 相似文献
2.
Urbanisation and industrial development lead to contamination of estuaries and streams with dispersed loadings of heavy metals and metalloids. Contributions of these elements also occur from natural sources. This study provides baseline geochemical data on the respective natural and anthropogenic inputs of Cu, Pb, Zn, Cd, As, Sb, Cr, Ni, Mn and S to estuarine, fluvial and wetland sediments, and adjacent soils, in the Kooloonbung Creek catchment that drains the Port Macquarie urban area in north coastal New South Wales. There have been anthropogenic additions of Cu, Pb, Zn and As from dispersed urban sources at Port Macquarie, but they are restricted to the local catchment and do not impact on the adjacent Hastings River estuary. The most contaminated sediments display enrichment factors up to 20 × for Cu and Pb, 9 × for Zn and 5 × for As relative to local background values. However, only one value (for Pb) exceeds National Water Quality Management Strategy interim sediment quality guideline (high) values. On the other hand, sediments and local soils are commonly strongly enriched in Cr, Ni and Mn, reflecting adjacent ultramafic and mafic rock substrate and lateritic regolith. Concentrations of Cr and Ni are commonly well above interim sediment quality guideline (high) values for sediments, but are in mineralogical forms that are not readily bioavailable. Sediment and soil quality guideline values consequently need to recognise natural enrichments and the mineralogical siting of heavy metals. Although dissolved concentrations of heavy metals in stream waters are commonly low, there is evidence for mobility of Cu, Zn, Fe and Al. Parts of the Kooloonbung Creek wetland area lie on sulfidic estuarine sediments (potential acid sulfate soils). Experimental oxidation of uncontaminated and contaminated sulfidic sediments leads to substantial dissolution of heavy metals under acid conditions, with subsequent aquatic mobility. The results warn about disturbance and oxidation of potential acid sulfate soils that have been contaminated by urban and natural heavy-metal sources. 相似文献
3.
Loose sediments like loess are easily erodable especially on hillslopes used for agriculture. Erosion contributes to the sedimentation and pollution of lakes such threatening quasi-natural ecosystems. On the other hand soil erosion damages fertile soils.The aim of the present paper is the assessment of soil and nutrient loss in a tributary catchment of Lake Balaton, including geoecological aspects of the lake ecosystem and of the slopes mantled by loess.The USLE is applied for small topological units, for the so called erotops. Rainfall simulation experiments were applied for the determination of the erodibility of soils. The calculation is based on a new, GIS aided method. Control measurements have been going on for four years at a gauging station to check how much sediment and water actually leaves the catchment.Results of sediment yield measurements were compared with the results obtained by the application of USLE for the whole catchment. According to this comparison only 2% leaves the catchment so that redeposition processes within the catchment are very important whereas the contribution of soil erosion to the eutrophication of the lake is not very significant in the small tributaries in the northern part of Lake Balaton catchment. 相似文献
4.
Suspended sediments in the Kharaa River catchment (Mongolia) and its impact on hyporheic zone functions 总被引:2,自引:2,他引:0
Melanie Hartwig Philipp Theuring Michael Rode Dietrich Borchardt 《Environmental Earth Sciences》2012,65(5):1535-1546
A previous study investigating the ecological status of the Kharaa River in Northern Mongolia reported fine-grained sediments
as being a major stress factor causing adverse impacts on the benthic ecology. However, the source of these sediments within
the catchment as well as the specific impact on hyporheic zone functions in the Kharaa River remained unclear. Therefore,
the objective of the current study was to investigate the underlying source–receptor system and implement an integrated monitoring
approach. Suspended sediment sources within the Kharaa catchment were identified by using extensive spatially distributed
sediment sampling and geochemical and isotope fingerprinting methods. On the receptor side, the ecological implications across
a gradient of fine-grained sediment influx were analyzed using a distinct hyporheic zone monitoring scheme at three representative
river reaches along the Kharaa River. Results of suspended sediment source monitoring show that during snowmelt runoff, riverbank
and gully erosion were the dominant sources. During the summer period, upland erosion contributed a substantial share of suspended
sediment. Fine-grained sediment influx proved to be the cause of habitat loss in the hyporheic zone and benthic oxygen production
limitation. This combined catchment and in-stream monitoring approach will allow for a better understanding and spatially
explicit analysis of the interactions of suspended sediment transport and hyporheic zone functioning. This information has
built the basis for a coupled modeling framework that will help to develop efficient management measures within the Kharaa
River basin with special emphasis on rapidly changing land-use and climatic conditions. 相似文献
5.
In recent decades, there have been discussions and predictions regarding the impact of climate on floods, due to its socioeconomic and environmental consequences. For accurate prediction of future flood events and their impacts, it is crucial to have an improved understanding on past flood events. Lacustrine sediments have been used as a natural archive to study the past flood events. Here, we study the impact of 1954 flood event on the lacustrine environment of Bengas and Rupa Lake in central Nepal based on X-ray fluorescence spectrometry (XRF) element analysis, magnetic susceptibility (MS), total organic carbon (TOC) and the biomarker molecular compositions. Results showed that 1954 flood event had significant impacts on the two lakes in terms of detrital input, organic matter deposition and aquatic production. Before the flood event, both two studied lakes had relatively lower catchment erosion rate, lower organic matter deposition and aquatic production. During the flood event, catchment erosion and aquatic production increased in both lakes due to mass transport deposits and the increased nutrition loading attributed to flood event. Following the flood event, Begnas Lake showed the sharp increase in organic matter deposition, whereas in the Rupa Lake organic matter deposition showed minor changes. The difference in organic matter deposition in lakes during flooding event is likely due to detrital material brought and deposited by the flood activity. Overall our results suggest that lacustrine sediments are sensitive to the extreme event and would be an ideal archive for the reconstruction of flood events. 相似文献
6.
László Ódor Richard B Wanty István Horváth Ubul Fügedi 《Journal of Geochemical Exploration》1998,65(1):47-60
Regional geochemical baseline values have been established for Hungary by the use of low-density stream-sediment surveys of flood-plain deposits of large drainage basins and of the fine fraction of stream sediments. The baseline values and anomaly thresholds thus produced helped to evaluate the importance of high toxic element concentrations found in soils in a valley downstream of a polymetallic vein-type base-metal mine. Erosion of the mine dumps and flotation dump, losses of metals during filtering, storage and transportation, human neglects, and operational breakdowns, have all contributed to the contamination of a small catchment basin in a procession of releases of solid waste. The sulfide-rich waste material weathers to a yellow color; this layer of `yellow sand' blankets a narrow strip of the floodplain of Toka Creek in the valley near the town of Gyöngyösoroszi. Contamination was spread out in the valley by floods. Metals present in the yellow sand include Pb, As, Cd, Cu, Zn, and Sb. Exposure of the local population to these metals may occur through inhalation of airborne particulates or by ingestion of these metals that are taken up by crops grown in the valley. To evaluate the areal extent and depth of the contamination, active stream sediment, flood-plain deposits, lake or reservoir sediments, soils, and surface water were sampled along the erosion pathways downstream of the mine and dumps. The flood-plain profile was sampled in detail to see the vertical distribution of elements and to relate the metal concentrations to the sedimentation and contamination histories of the flood plain. Downward migration of mobile Zn and Cd from the contaminated upper layers under supergene conditions is observed, while vertical migration of Pb, As, Hg and Sb appears to be insignificant. Soil profiles of 137Cs which originated from above-ground atomic bomb tests and the Chernobyl accident, provide good evidence that the upper 30–40 cm of the flood-plain sections, which includes the yellow sand contamination, were deposited in the last 30–40 years. 相似文献
7.
A Comparison of Fluvial Sediment Phosphorus (P) Chemistry in Relation to Location and Potential to Influence Stream P Concentrations 总被引:3,自引:0,他引:3
Fluvial sediments are subject to cyclic submersion during changes in stream flow, which can affect their phosphorus (P) sorptive capacity. As fluvial sediments play a major role in determining P concentrations in stream flow, we compared the P chemistry of exposed stream bank and submerged bed sediments from an agricultural catchment in central Pennsylvania, USA. Total P concentration was greater in bank (417 mg kg-1) than bed sediments (281 mg kg-1), but because bed sediments contained more sand-sized material, they could release more P and support a higher solution P concentration (0.043 mg l-1) than bank sediments (0.020 mg l-1). Phosphorus release was a function of Mehlich-3 soluble Fe in stream sediments (r > 0.65), reflecting redox processes in the fluvial system. In contrast, P sorption maxima of bank and bed sediments were related to Mehlich-3 soluble Al (r > 0.78) and organic matter concentration (r > 0.79). Overall, our research suggested that erosion of bank sediments should contribute less P and may be a sink for P in the stream system compared with resuspension of bed sediment. However, bank sediments may have the potential to be a large source of P in downstream reservoirs or lakes, where increased microbial activity and reducing conditions may solubilise sediment-bound P. 相似文献
8.
9.
Effect of widespread severely acidic soils on spatial features and abundance of trace elements in streams 总被引:1,自引:0,他引:1
In the coastal area of western Finland, a large number of streams are strongly acidic and contaminated with metals. The reason for this is not historical and present industrial, mining and urban activities, but a current high rate of weathering and leaching of widespread acid sulphate soils (pH 2.5–4.0) developed in artificially drained Holocene marine and lacustrine sulphide-bearing sediments. Evaluation of existing hydro- and geochemical field and experimental data revealed that: (1) cobalt, Ni and Zn are extensively leached from the acid sulphate soils and thus exist abundantly in streams affected by such soils, (2) copper and Tl are also leached abundantly from the acid sulphate soils, although not to the same extent as are Co, Ni and Zn, (3) vanadium is in general depleted and Cr only weakly enriched in streams draining ‘the average acid sulphate soil’, but they increase substantially in severely acidic streams in catchments underlain with particularly acidic soil, (4) arsenic and Pb are not leached more abundantly from the acid sulphate soils than from the common types of soils and sediments (till, glaciofluvial deposits, peat) resulting in aquatic abundance and distribution patterns unrelated to the acid sulphate soil occurrences. 相似文献
10.
Fresh flood deposits were sampled in the flood-plains of two river systems, the River Meuse, with a catchment area of 33,000
km2 and the River Geul, with a catchment area of 3,000 km2. As a result of industrial and mining activities, both rivers have a history of severe metal pollution, especially with zinc,
lead, and cadmium. The flood deposits of both rivers are heterogeneous mixtures of contaminated bottom sediments (with relatively
long residence times in the river) and clean sediments derived from soil erosion on agricultural cropland (with very short
residence times). An additional source of sediment is formed by erosion of older, locally highly contaminated streambank deposits.
These older sediments are polluted as a result of solid waste disposal containing metalliferous ore and tailings in the sand
fraction. This is especially the case in the River Geul, which drains an old zinc and lead mining area. The metal content
of the Meuse sediments, however, originates largely from liquid industrial wastes and occurs mainly in the clay fraction.
For this reason, the positive correlation between textural composition, organic matter content, and heavy metal concentration,
which is often reported, was not observed, and normalization of the metal content was not possible. Nevertheless, a clear
decrease of contamination was noticed along the River Geul; this trend was absent along the River Meuse. An attempt has been
made to model the longitudinal decay pattern for each of the investigated havey metals. 相似文献
11.
Stanley R. Riggs 《Estuaries and Coasts》1996,19(2):169-185
The analyses of 248 samples have revealed that the composition and distribution patterns of sediments within the Albemarle estuarine system (AES) represent a complex interaction between multiple sediment sources, basin morphology and evolution, and associated estuarine processes. Three sediment end-member types are dominant: sand, peat, and organic-rich mud (ORM). Throughout the AES, shallow perimeter platforms and associated sediment-bank shorelines are eroded into Pleistocene units. Shoreline recession supplies sand to the platforms and mud to the central basins; these sediments mix with suspended sediment from the fluvial drainages. Swamp forest-peat and marsh-peat shorelines are actively eroding and supply fine organic detritus to produce the dominant ORM sediment in the central basins. Perimeter platform sands grade into ORM on the platform slope. ORM constitutes about 70% of the benthic habitats within the AES and has an average composition of 76.2% inorganic mud, 13.1% sand, and 10.7% organic matter. The characteristics of ORM greatly affect the benthic community structure, chemical quality of the sediments, and the water quality of the estuary. ORM readily moves in and out of the water column in response to natural and anthropogenic activities, affecting water column turbidity and trace and major element geochemistry. Organic matter and clay minerals in ORM are chemically reactive and interact with the water column to adsorb or release contaminants, nutrients, and gases. Thus, ORM acts as both a sink and source for many different chemical constituents in the water column and plays important, but poorly understood, functions in the physical and chemical dynamics of estuarine ecosystems. 相似文献
12.
V. D. Strakhovenko V. G. Kabannik I. N. Malikova 《Lithology and Mineral Resources》2014,49(3):213-227
Regularities of the formation of bottom sediments down to a depth of 1.2 m, as well as factors governing the composition of sediments, waters, and soils in the catchment area of the lake, are discussed. It has been established that the chemical composition of lacustrine sediments is closely associated with the composition of soils in the ambient watersheds, and the soils, in turn, are associated with the composition of the soil-forming rocks. The available data suggest an extremely irregular contamination of the lake system by technogenic radionuclides within the water area. Maximum radiocesium contamination of lacustrine bottom sediments is 350 mCi/km2 (recalculated to year 2000). Concentrations of elements (Cu, Zn, Cr, Ni, Co, Mg, Be, Sb, Mn, and others) in bottom sediments, water, and soils in catchment areas of Lake Kolyvan do not exceed the background values (except for the Hg content in bottom sediments), suggesting that the area under consideration is not contaminated by inorganic technogenic components. 相似文献
13.
S.K. Acharyya 《Gondwana Research》2005,8(1):55-66
Late Quaternary stratigraphy and sedimentation in the Ganga Alluvial Plain and the Bengal Basin have influenced arsenic contamination of groundwater. Arsenic contaminated aquifers are pervasive within lowland organic rich, clayey deltaic sediments in the Bengal Basin and locally within similar facies in narrow, entrenched river valleys within the Ganga Alluvial Plain. These were mainly deposited during early-mid Holocene sea level rise. Arsenic was transported from disseminated sources as adsorbed on dispersed phases of hydrated-iron-oxide. These were preferentially entrapped as sediment coatings on organic-rich, fine-grained deltaic and floodplain sediments. Arsenic was released later to groundwater mainly by reductive dissolution of hydrated-iron-oxide and corresponding oxidation of sediment organic matter. Strong reducing nature of groundwater in the Bengal Basin and parts of affected middle Ganga floodplains is indicated by high concentration of dissolved iron (maximum 9-35 mg/l). Groundwater being virtually stagnant under these settings, released arsenic accumulates and contaminates groundwater. The upland terraces in the Bengal Basin and in the Central Ganga Alluvial Plain, made up of the Pleistocene sediments are free of arsenic contamination in groundwater. These sediments are weakly oxidised in nature and associated groundwater is mildly reducing in general with low concentration of iron (<1 mg/l), and thus incapable to release arsenic. These sediments are also flushed free of arsenic, released if any, by groundwater flow due to high hydraulic head, because of their initial low-stand setting and later upland terraced position. 相似文献
14.
The Wadi Mina Watershed, western area of Algeria is characterized by rare and irregular rains and a fragile and weak vegetable cover. The sediments resulting from erosion are transported and contributed to silting dam Sidi Mhamed Benaouda. The combination of the thematical maps of the various erosive factors according to the Revised Universal Soil Loss Equation (RUSLE) in SIG by ArcGIS 10.2 software provided a reliable forecast of the annual rates of soil loss by delimiting the areas prone to erosive risk in the catchment above mentioned. The estimated potential average annual soil loss is 11.2 t/ha/yr., and the potential erosion rates from recognized erosion classes ranged from 0.0 to plus 100 t/ha/yr. About 50% of the catchment area was predicted to have very low to low erosion risk, with soil loss between 0 and 7.4 t/ha/yr. Erosion risk is moderate over 13.9% of the catchment, where calculated soil loss is between 7.4 and 12 t/ha/yr. Erosion risk is high to dangerous over 36.1% of the catchment, where calculated soil loss is more than 12 t/ha/yr. According to this study, it appeared clearly that we must intervene quickly by using reliable and effective conservation techniques. 相似文献
15.
Sediments have been used to detect sources of contamination in a catchment of the Port Jackson (Sydney Harbour) estuary and
to evaluate the effects of different land-use practices on the fluvial environment. Mean enrichment (mean concentrations over
pre-anthropogenic background) of size-normalized (<62.5 μm) aquatic sediment is 10 × for Cu, 20× for Pb and 90× for Zn adjacent
to industrialized areas and 2×, 7× and 7×, respectively for these metals in highly urbanized subcatchments. Diffuse sources
contribute minor metals to fluvial sediment even in the most underdeveloped subcatchment (2×, 3× and 3× for Cu, Pb and Zn
respectively). Organochlorine pesticide residue concentrations parallel heavy-metal trends due to a common mixed industrial
base. Effects-based sediment criteria suggest that some adverse biological impacts are probably occurring in streams flowing
through the industrial areas. This interpretation is supported by sequential extraction data which show that a moderate proportion
of total heavy metals, especially Zn, is associated with the more bioavailable exchangeable/adsorbed phases in these aquatic
sediments. High total suspended solid loads in water downstream of one of the industrial centers, and high particle-bound
Cu and Pb concentrations, suggest that most contaminants exiting the catchment do so in association with the solid phase.
Received: 29 March 1999 · Accepted: 30 August 1999 相似文献
16.
The relative abundances and distributions of branched glycerol dialkyl glycerol tetraethers (brGDGTs) in marine and lacustrine sediments have been recently used as paleo-environmental proxies for the input of soil organic matter and past continental temperatures, respectively. The putative main source of brGDGTs is soil bacteria. Therefore, these biomarkers are also part of the soil organic matter stock that accumulates in the terrigenous environment. Here we present a method for isolating and purifying these compounds from lake sediments, soils and peat for radiocarbon (14C) measurement using a combination of normal and reversed phase high performance liquid chromatography, allowing complete separation of co-eluting compounds. Radiocarbon analysis was performed on an accelerator mass spectrometer system equipped with a gas ion source. We assessed the accuracy and the necessary corrections with modern and radiocarbon-dead procedural blanks. Blank assessment revealed that the reverse phase step introduced significant amounts of extraneous carbon, while the normal phase step did not. We show that with our method and instrumentation it is possible to obtain accurate and precise 14C analyses of brGDGTs with sample amounts as small as 10 μg C. Finally we demonstrate the application of the measurement of 14C concentrations of several brGDGTs isolated from lake sediments and peat soils. 相似文献
17.
Graham Bird Paul A. Brewer Mark G. Macklin Dan Balteanu Mihaela Serban Basarab Driga Sorin Zaharia 《Applied Geochemistry》2008,23(12):3498-3518
The River Vişeu catchment in Maramureş County, northwestern Romania, has a long history of base and precious metal mining. Between 1994 and 2003 waste from mining activity at Baia Borşa was stored in the Novaţ-Roşu tailings pond in the upper Vişeu catchment. However, in March 2000, the tailings dam failed releasing approximately 100,000 m3 of contaminated water and 20,000 t of mineral-rich solid waste, which was routed downstream through the Rivers Novaţ, Vaser and Vişeu into the River Tisa. Following the accident metal (Cd, Cu, Pb, Zn) concentrations in river water and river channel sediment were assessed in samples collected annually (July 2000, 2001, 2002 and 2003) from 29 sites in the Vişeu catchment, downstream of the tailings pond. Additionally, the speciation of sediment-associated metals was established using a 4-stage sequential extraction procedure (SEP) and Pb isotope analysis (206/204Pb and 207/204Pb) was carried out to establish the provenance of contaminated sediments. Metal concentrations in river water were found to comply with EU directive ‘target’ values within four months of the failure. However, the impact of the spill upon river channel sediments was found to be much longer-lasting, with evidence of the delayed downstream remobilization of tailings stored within the narrow Novaţ valley following the dam failure, as well as continued inputs of contaminated sediment to the River Vişeu from the River Tisla, another mining-affected tributary. Comparison with data from other recent tailings dam failures, indicates that river system recovery rates depend upon local geomorphological conditions, hydrological regimes, and the nature and scale of post-spill clean-up operations. 相似文献
18.
The geochemistry of oxic sediments was contrasted across a range of Canadian aquatic ecosystems; 7 freshwater lakes, (3 circumneutral and 4 acidic), 15 peatlands (5 mineral-rich, 5 moderately-poor and 5 mineral-poor), 9 wetlands (3 oligosaline, 3 mesosaline and 3 euryhaline), an estuary (deposited and suspended sediments) and an intertidal region. Sediments were characterized by a simultaneous extraction that separated sediments into easily reducible (ER) metal (oxyhydroxides of Mn and easily reducible amorphous oxyhydroxides of Fe) and reducible (R) metal (more crystalline forms of oxyhydroxides of Fe), organic matter, and, the concentrations and partitioning of Zn, Cu and Cd associated with these 3 sediment components. Ecosystems were distinct with respect to ER Fe and organic matter [canonical variate analysis (CVA)] with 53% of among system variation in geochemistry attributed to these 2 components. Sediments of peatlands and wetlands contained greater amounts of organic matter whereas sediments of lakes, intertidal and estuarine deposited and suspended sediments were characterized by greater amounts of ER Fe. A further 21% of among system variation could be ascribed to organically bound Fe that was greater in acidic lakes and mineral-rich peatlands as compared to other systems. Concentration and partitioning of Cd within sediments was regionally dependent with 41% of among system variation (CVA) attributed to differences in ER Cd and R Cd. Cadmium from peatlands and lakes located in Ontario was recovered from all 3 sediment components whereas sediment from wetlands, the estuary and the intertidal regions of British Columbia (BC) contained no organically bound Cd with amounts recovered occurring mostly as ER Cd. Lakes and peatlands located in Ontario contained 3–5-fold total Cd as compared to ecosystems located in BC. A further 21% of among ecosystem variation was attributed to Zn partitioning. Zinc in peatland and wetland sediments occurred as R Zn as compared to lake and estuarine deposited sediments where Zn was recovered both as ER and R Zn. Total Zn was also 3–5-fold greater in sediments of systems in Ontario as compared to those sampled in BC. Concentration and partitioning of Cu was similar across all systems with Cu recovered from the organic component of sediment. The geochemistry of surficial oxic sediments with respect to ER Mn, R Fe and organic matter and the geochemical associations among these sediment components is ecosystem and region dependent. For assessing impacts of metals on sediment dwelling biota the geochemical characteristics of the system under study should first be defined. 相似文献
19.
The Nepal Himalayas is the source of many glacial and spring-fed river systems crisscrossing the moun-tainous terrain.There 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 flux.We analyzed flu-vial sediments from two SMRs and compared the results with two large mountain rivers(LMRs)in Nepal.We 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 sterols.The SMRs indicated a similarity in lipid distribution and were affected by a strong seasonal variability.The LMRs showed a dis-tinct contrast in the distribution of lipids in suspended sediments.Bedload sediments in SMRs were derived from diverse sources with weak terrigenous dominance all-year-round compared to the sus-pended load.Functional lipids(n-alkanoic acids and n-alkanols)were the major constituents in SMR sed-iments,indicating better preservation.In contrast,n-alkane concentration dominated over other fractions in suspended sediments retrieved from LMRs.The 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 LMRs.Such an unusual trend is attributed to specific biomarker sources from the catchment and ongoing processes in fluvial systems.Topsoil colonized by fungal species under moist acidic condi-tions and autochthonous bacteria contributes to the organic matter pool in shallow SMRs.In LMRs,the contribution from thermally mature sedimentary hydrocarbons and the diagenetic reduction of n-alkanoic acids to n-alkanes are additional contributors to the allochthonous carbon pool.The differences in lipid concentrations,their distribution,seasonality,and the size of rivers suggest differential preserva-tion/degradation of the organic matter pool and their importance in contributing to the carbon budget. 相似文献
20.
We measured molecular distributions and compound-specific hydrogen (δD) and stable carbon isotopic ratios (δ13C) of mid- and long-chain n-alkanes in forest soils, wetland peats and lake sediments within the Dorokawa watershed, Hokkaido, Japan, to better understand sources and processes associate with delivery of terrestrial organic matter into the lake sediments. δ13C values of odd carbon numbered C23-C33n-alkanes ranged from −37.2‰ to −31.5‰, while δD values of these alkanes showed a large degree of variability that ranged from −244‰ to −180‰. Molecular distributions in combination with stable carbon isotopic compositions indicate a large contribution of C3 trees as the main source of n-alkanes in forested soils whereas n-alkanes in wetland soil are exclusively derived from marsh grass and/or moss. We found that the n-alkane δD values are much higher in forest soils than wetland peat. The higher δD values in forest samples could be explained by the enrichment of deuterium in leaf and soil waters due to increased evapotranspiration in the forest or differences in physiology of source plants between wetland and forest. A δ13C vs. δD diagram of n-alkanes among forest, wetland and lake samples showed that C25-C31n-alkanes deposited in lake sediments are mainly derived from tree leaves due to the preferential transport of the forest soil organic matter over the wetland or an increased contribution of atmospheric input of tree leaf wax in the offshore sites. This study demonstrates that compound-specific δD analysis provides a useful approach for better understanding source and transport of terrestrial biomarkers in a C3 plant-dominated catchment. 相似文献