Wind-induced sediment resuspension as a potential factor sustaining eutrophication in large and shallow Lake Peipsi   总被引：1，自引：0，他引：1  

Olga Tammeorg  Juha Niemistö  Tõnu Möls  Reet Laugaste  Kristel Panksep  Külli Kangur 《Aquatic Sciences - Research Across Boundaries》2013,75(4):559-570

Using sediment traps, we aimed to elucidate the temporal and spatial variations in sediment fluxes in large and shallow Lake Peipsi, over the May to October 2011 period, and analyze the factors behind those variations. The effects of weather factors (mean and maximum wind velocity, water level and water temperature) on sediment resuspension and the concentrations of suspended solids (SS), total phosphorus (TP), soluble reactive phosphorus (SRP), and chlorophyll a (Chl a) were investigated. Moreover, the internal loading of TP due to sediment resuspension was determined. The sediment resuspension rates were significantly higher in the shallower waters than in the deeper parts of the lake. Resuspension was a major factor in sedimentation dynamics of the lake, which is presently subject to eutrophication. The rates of sediment resuspension followed the same pattern as gross sedimentation during the study period, and their respective values differed significantly between sampling dates. The highest resuspension rates were observed in September (mean 55.4 g dw m^?2 day^?1), when the impacts of wind events were particularly pronounced. Weather factors that were recorded approximately 2 weeks before water and sediment sampling affected the gross sedimentation and sediment resuspension. The water quality variables of SS, TP, SRP, Chl a were similarly affected. During the study, TP concentrations of the water were mainly determined by the resuspension of sediments containing a large pool of organic material. Although internal loading of TP due to resuspension was several times greater than external loading, external loading determines the amount of phosphorus that enters the lake and can be resuspended.  相似文献   

Geomorphic controls on floodplain sediment and soil organic carbon storage in a Scottish mountain river     

Ward Swinnen  Teun Daniëls  Eline Maurer  Nils Broothaerts  Gert Verstraeten 《地球表面变化过程与地形》2020,45(1):207-223

River floodplains constitute an important element in the terrestrial sediment and organic carbon cycle and store variable amounts of carbon and sediment depending on a complex interplay of internal and external driving forces. Quantifying the storage in floodplains is crucial to understand their role in the sediment and carbon cascades. Unfortunately, quantitative data on floodplain storage are limited, especially at larger spatial scales. Rivers in the Scottish Highlands can provide a special case to study alluvial sediment and carbon dynamics because of the dominance of peatlands throughout the landscape, but the alluvial history of the region remains poorly understood. In this study, the floodplain sediment and soil organic carbon storage is quantified for the mountainous headwaters of the River Dee in eastern Scotland (663 km²), based on a coring dataset of 78 floodplain cross-sections. Whereas the mineral sediment storage is dominated by wandering gravel-bed river sections, most of the soil organic carbon storage can be found in anastomosing and meandering sections. The total storage for the Upper Dee catchment can be estimated at 5.2 Mt or 2306.5 Mg ha^-1 of mineral sediment and 0.7 Mt or 323.3 Mg C ha^-1 of soil organic carbon, which is in line with other studies on temperate river systems. Statistical analysis indicates that the storage is mostly related to the floodplain slope and the geomorphic floodplain type, which incorporates the characteristic stream power, channel morphology and the deposit type. Mapping of the geomorphic floodplain type using a simple classification scheme shows to be a powerful tool in studying the total storage and local variability of mineral sediment and soil organic carbon in floodplains. © 2019 John Wiley & Sons, Ltd.  相似文献   

Environmental responses to Lateglacial climatic fluctuations recorded in the sediments of pre‐Alpine Lake Mondsee (northeastern Alps)     

Stefan Lauterbach  Achim Brauer  Nils Andersen  Dan L. Danielopol  Peter Dulski  Matthias Hüls  Krystyna Milecka  Tadeusz Namiotko  Milena Obremska  Ulrich Von Grafenstein  Declakes Participants 《第四纪科学杂志》2011,26(3):253-267

Investigation of the sedimentary record of pre‐Alpine Lake Mondsee (Upper Austria) focused on the environmental reaction to rapid Lateglacial climatic changes. Results of this study reveal complex proxy responses that are variable in time and influenced by the long‐term evolution of the lake and its catchment. A new field sampling approach facilitated continuous and precisely controlled parallel sampling at decadal to sub‐annual resolution for µ‐XRF element scanning, carbon geochemistry, stable isotope measurements on ostracods, pollen analyses and large‐scale thin sections for microfacies analysis. The Holocene chronology is established through microscopic varve counting and supported by accelerator mass spectrometry ¹⁴C dating of terrestrial plant macrofossils, whereas the Lateglacial age model is based on δ¹⁸O wiggle matching with the Greenland NGRIP record, using the GICC05 chronology. Microfacies analysis enables the detection of subtle sedimentological changes, proving that depositional processes even in rather large lake systems are highly sensitive to climate forcing. Comparing periods of major warming at the onset of the Lateglacial and Holocene and of major cooling at the onset of the Younger Dryas reveals differences in proxy responses, reflecting threshold effects and ecosystem inertia. Temperature increase, vegetation recovery, decrease of detrital flux and intensification of biochemical calcite precipitation at the onset of the Holocene took place with only decadal leads and lags over a ca. 100 a period, whereas the spread of woodlands and the reduction of detrital flux lagged the warming at the onset of the Lateglacial Interstadial by ca. 500–750 a. Cooling at the onset of the Younger Dryas is reflected by the simultaneous reaction of δ¹⁸O and vegetation, but sedimentological changes (reduction of endogenic calcite content, increase in detrital flux) were delayed by about 150–300 a. Three short‐term Lateglacial cold intervals, corresponding to Greenland isotope substages GI‐1d, GI‐1c2 and GI‐1b, also show complex proxy responses that vary in time. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

An index to assess hydromorphological quality of Estonian surface waters based on macroinvertebrate taxonomic composition     

Henn Timm  Kairi Käiro  Tõnu Möls  Taavi Virro 《Limnologica》2011,41(4):398-410

We developed an index (MESH – Macroinvertebrates in Estonia: Score of Hydromorphology) to assess hydromorphological quality of Estonian surface waters based on macroinvertebrate taxonomic composition. The MESH is an average score based on the affinities of selected indicator taxa to flow velocity and bottom type. As both parameters were highly correlated (r = 0.65) indicator response to both parameters were combined. The list of MESH indicators includes 394 freshwater macroinvertebrate taxa derived from 3282 samples collected from rivers and lakes during 1985–2009. The indicators were selected out of 690 taxa, by applying the information-theoretical Kullback–Leibler divergence. The individual scores of macroinvertebrates range from 0 to 3, the higher scores indicating faster flow and/or solid bottom substrate. For standing waters, flow velocity was always considered zero. Among the reference waterbodies, mean MESH was the highest for small streams followed by middle streams, large streams, and lakes. In lakes with medium water hardness (the prevailing type in Estonia), the MESH decreased gradually from stony to muddy bottom. The highest MESH values for standing waters were observed in the stony surf zone of very large lakes (area > 100 km²). The lowest values occurred for small lakes with exceptional hydrochemical characteristics (soft- and darkwater, and calcareous types). Similarly, MESH indicated stream degradation by damming. Mean MESH in reservoirs with a muddy bottom was significantly lower than in reservoirs with a hard bottom, or in unregulated stream sections.  相似文献   

Evaluating centralized return centers in a reverse logistics network: An integrated fuzzy multi-criteria decision approach   总被引：3，自引：3，他引：0  

G. Tuzkaya M.Sc.  B. Gülsün Ph.D. 《International Journal of Environmental Science and Technology》2008,5(3):339-352

In this paper, the centralized return centers location evaluation problem in a reverse logistics network is investigated. This problem is solved via an integrated analytic network process-fuzzy technique for order preference by similarity to ideal solution approach. Analytic network process allows us to evaluate criteria preferences while considering interdependence between them. On the other hand, technique for order preference by similarity to ideal solution decreases the number of computational steps compared to simple analytic network process evaluation. An important characteristic of the centralized return centers location evaluation problem, vagueness, is adapted to the methodology via the usage of fuzzy numbers in the technique for order preference by similarity to ideal solution approach. Finally, a numerical example is given to demonstrate the usefulness of the methodology. The results indicate that, this integrated multi-criteria decision making methodology is suitable for the decision making problems that needs considering multiple criteria conflicting each other. Also, by using this methodology, the interdependences between the criteria may be considered for these kinds of problems in a flexible and systematic manner.  相似文献   

Multiphase chemistry and acidity of clouds at Kleiner Feldberg     

S. Fuzzi  M. C. Facchini  D. Schell  W. Wobrock  P. Winkler  B. G. Arends  M. Kessel  J. J. Möls  S. Pahl  T. Schneider  A. Berner  I. Solly  C. Kruisz  M. Kalina  H. Fierlinger  A. Hallberg  P. Vitali  L. Santoli  G. Tigli 《Journal of Atmospheric Chemistry》1994,19(1-2):87-106

The chemistry of cloud multiphase systems was studied within the Kleiner Feldberg Cloud Experiment 1990. The clouds encountered during this experimental campaign could be divided into two categories according to the origin of air masses in which the clouds formed. From the chemical point of view, clouds passing the sampling site during the first period of the campaign (26 October-4 November) were characterized by lower pollutant loading and higher pH, as compared to clouds during the final period of the experimental campaign (10–13 November). The study of multiphase partitioning of the main chemical constituents of the cloud systems and of atmospheric acidity within the multiphase systems themselves (gas + interstitial aerosol + liquid droplets) are presented in this paper. A general lack of gaseous NH₃ was found in these cloud systems, which caused a lack of buffer capacity toward acid addition. Evidence supports the hypothesis that the higher acidity of the cloud systems during this final period of the campaign was due to input of HNO₃. Our measurements, however, could not determine whether the observed input was due to scavenging of gaseous HNO₃ from the air feeding into the cloud, or to heterogeneous HNO₃ formation via NO₂ oxidation by O₃ to NO₃ and N₂O₅. Sulfate in cloud droplets mainly originated from aerosol SO ₄ ^2– scavenging, since S(IV) to S(VI) liquid phase conversion was inhibited due to both lack of H₂O₂ and low pH of cloud droplets, which made O₃ and metal catalyzed S(IV) oxidation inefficient.  相似文献