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1.
Microbial mineralization and assimilation of black carbon: Dependency on degree of thermal alteration 总被引:4,自引:0,他引:4
Black carbon is degraded slowly in the environment and its formation can therefore be an effective sink for atmospheric CO2. This study examined whether charcoal is assimilated by microorganisms or not and estimated the rate of mineralization depending on the degree of thermal alteration of the black carbon. Charcoals were produced at three different temperatures from homogeneously 14C labelled plant material and incubated in soil, and 14C in the evolved CO2 and the microbial biomass was measured. Unlike parallel plant samples, CO2 evolution from the charcoals showed no lag phase, but a period of faster CO2 evolution for the first 5–8 days followed by a period of slow evolution. The mineralization of charcoal appeared to decrease with increasing temperature at which it was produced. This was also the case after the initial period of fast CO2 evolution. With the techniques used, it was not possible to observe any microbial assimilation of charcoal, either because it did not occur, or because the methods used were not sufficiently sensitive. However, the lack of a lag phase in the CO2 evolution from the charcoals is in line with earlier evidence that charcoal is initially oxidized at the surfaces by abiotic processes. 相似文献
2.
Hydrodynamics coefficients for vertical circular cylinders at finite water depth are obtained and presented for different depth to radius and draft to radius ratios. A summary of equations for computer application is presented. Limiting values for heave added mass for zero frequency are discussed. A matching technique is used to satisfy the continuity of pressure and normal velocities. 相似文献
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Coastal lagoons and beach ridges as complementary sedimentary archives for the reconstruction of Holocene relative sea‐level changes 下载免费PDF全文
Lasse Sander Mikkel U. Hede Mikkel Fruergaard Lars Nielsen Lars B. Clemmensen Aart Kroon Peter N. Johannessen Lars H. Nielsen Morten Pejrup 《地学学报》2016,28(1):43-49
Coastal lagoons and beach ridges are genetically independent, though non‐continuous, sedimentary archives. We here combine the results from two recently published studies in order to produce an 8000‐year‐long record of Holocene relative sea‐level changes on the island of Samsø, southern Kattegat, Denmark. The reconstruction of the initial mid‐Holocene sea‐level rise is based on the sedimentary infill from topography‐confined coastal lagoons (Sander et al., Boreas, 2015b). Sea‐level index points over the mid‐ to late Holocene period of sea‐level stability and fall are retrieved from the internal structures of a wide beach‐ridge system (Hede et al., The Holocene, 2015). Data from sediment coring, georadar and absolute dating are thus combined in an inter‐disciplinary approach that is highly reproducible in micro‐tidal environments characterised by high sediment supply. We show here that the commonly proximate occurrence of coastal lagoons and beach ridges allows us to produce seamless time series of relative sea‐level changes from field sites in SW Scandinavia and in similar coastal environments. 相似文献
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Evidence for the trapped liquid shift effect in the Mount Ayliff Intrusion,South Africa 总被引:1,自引:2,他引:1
R. Grant Cawthorn Bernhard K. Sander Ian M. Jones 《Contributions to Mineralogy and Petrology》1992,111(2):194-202
Postcumulus trapped liquid shift in layered complexes produces cumulate minerals with more fractionated compositions than the original primary phases. This effect is shown by olivine compositions from the base of the Mount Ayliff Intrusion, where varying proportions of olivine to interstitial liquid produce a suite of rocks which define a tight linear trend on a binary whole-rock plot of MgO versus FeO. Extrapolation of this trend constrains the composition of the primary cumulus olivine to the range Fo84–86, whereas olivine actually present have compositions Fo77–83. The magnitude of the discrepancy between the theoretical and observed olivine compositions correlates directly with the weight fraction of interstitial liquid. These observations are quantitatively predicted by the trapped liquid shift model. They also argue against significant migration of residual liquid. Trapped liquid shift is documented over a vertical interval of 60 m. It occurred in rocks lying only 1 m above the basal contact of the intrusion and hence must be a comparatively rapid process. 相似文献
8.
Dieter Kelletat Sander R. Scheffers Anja Scheffers 《Pure and Applied Geophysics》2007,164(2-3):413-431
The Andaman-Sumatra Tsunami of Dec. 26, 2004, was by far the largest tsunami catastrophe in human history. An earthquake of
9 to 9.3 on the Richter scale, the extension of waves over more than 5000 km of ocean and run-ups up to 35 m are its key features.
These characteristics suggest significant changes in coastal morphology and high sediment transport rates. A field survey
along the west coast of Thailand (Phuket Island, Khao Lak region including some Similan Islands, Nang Pha mangrove areas and
Phi Phi Don Islands) seven to nine weeks after the tsunami, however, discovered only small changes in coastal morphology and
a limited amount of dislocated sediments, restricted to the lower meters of the tsunami waves. This is in striking contrast
to many paleo-tsunami's events of the Atlantic region. Explanations for this discrepancy are sought in:
a. Mechanics of the earthquake. A rather slow shock impulse on the water masses over the very long earthquake zone,
b. Shallow water in the earthquake zone, and
c. Bathymetry of the foreshore zone at the impacted sites. Shallow water west of Thailand has diminished wave energy significantly.
The differences in geomorphological and sedimentological signatures of this tsunami compared with many paleo-tsunami worldwide
makes it unsuitable to be used as a model for old and future tsunami imprints by an event of this extreme energy and extension. 相似文献
9.
Sander Wijnhoven Vincent Escaravage Eugène Daemen Herman Hummel 《Estuaries and Coasts》2010,33(6):1261-1278
The former tidal inlet Lake Veere was turned into a stagnant brackish lake in 1961. Ever since, the system has shown a continuous
degradation. The current study shows the monitoring results for the macrozoobenthic communities and the abiotic conditions
for the period 1990–2008. This includes the first step to remediation, the restoration of the exchange between the tidal marine
Eastern Scheldt and Lake Veere in 2004. A continuous decline in water clearance co-occurring with decreasing macrofauna densities
and richness was observed till 2004. Water quality (e.g., secchi depth, nutrient levels, and oxygen conditions) improved significantly
after the measure at a higher salinity level with less variation. But the macrofauna densities, biomass, and diversity did
not improve yet. First indications of changes in the benthic communities by arrival of new and returning species are however
observed and show that restoration at macrofauna level follows the improved abiotic conditions with a delay of several years. 相似文献
10.
Losses of pelagic diatom production resulting from silica limitation have not only been blamed for toxic algal blooms, but for the reduction in ability of coastal food webs to support higher trophic levels. Recent research has shown the importance of advective seepage water fluxes of dissolved silica (DSi) from freshwater marshes to pelagic waters during moments of riverine Si-limitation. In this study, we investigated the potential impact of recently installed new tidal areas along the Schelde estuary, located in former polder areas and characterized by so-called controlled reduced tidal regimes (CRT). Nine mass-balance studies were conducted in a newly constructed CRT in the freshwater Schelde estuary. During complete tidal cycles both DSi and amorphous silica (ASi) concentrations were monitored at the entrance culverts and in different habitats in the marsh. A swift DSi-delivery capacity was observed despite the shifted spatiotemporal frame of exchange processes compared to reference marshes. As silica-accumulating vegetation is not yet present, and difference with reference marshes’ deliveries is surprisingly small, we indicate diatomaceous debris and phytoliths to be the main silica source. Although further research is necessary on the driving forces of the different processes involved, restoration of former agricultural areas under CRT-regime provide the potential to buffer silica in the estuary. 相似文献