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1.
An investigation of 25,000 samples of foodstuffs and feedstuffs in Czechoslovakia, contaminated by fall-out cesium after the accident in the Chernobyl nuclear power plant, performed from May 5, 1986 to March 31, 1988, revealed that both the values of cesium transfer-factors in food--animal tissues--milk transitions and the values of biological half-life of cesium are functions of internal and external conditions of contamination. Organism individuality as the main internal condition causes the variance of about +/- 50% of the mean value of the respective transfer-factor. Through the external conditions, mainly the environmental contamination level, type of ingested food and time of ingestion, the mean values of transfer-factors are influenced up to 500%, e.g. to the value of 0.5. But this value converges with growing up contamination of food and environment to the limit of 0.3. The first two to three biological half-lives after the last ingestion of contaminated food are up to ten-times shorter than those at stabilized state. 相似文献
2.
We investigated the role of water-extractable carbon (C-extr) as potential substrate for forest soil microorganisms by comparing
belowground C fluxes at a plot with the forest floor removed (no-litter) and at a control plot. One-third lower soil respiration
rates at the no-litter plot gave evidence that the forest floor was the source of considerable amounts of microbially degradable
C. Laboratory incubation of C-extr, fractionated into neutral and acid moieties, showed that part of the C-extr was degraded
rapidly, and that the high-molecular-weight acid fraction was much less degradable than the neutral C. To the extent that
the degradable portion of the water-extractable C can be regenerated quickly, it may supply much of the substrate for heterotrophic
soil respiration.
Received: 11 December 1995 相似文献
3.
Red cells coated with immunoglobulin G: binding and sphering by mononuclear cells in man 总被引：79，自引：0，他引：79
Human monocytes, macrophages, and certain lymphocytes bind firmly to red cells coated with immunoglobulin G, whether or not it is acting as antibody. Monocyte binding is specific for cells coated with immunoglobulin G and is inhibited specifically by this immunoglobulin or its Fc-fragment in solution. Although not involving serum complement and not usually a prelude to erythrophagocytosis, this binding causes rapid morphological injury to red cells, as manifested by their sphering, increased osmotic fragility, deformation, and fragmentation. It is inferred that mononuclear cells have specific surface receptors for immunoglobulin G and that these provide a critical phase of the mechanism in vivo, whereby red cells or other particles coated with antibody are apprehended and destroyed. 相似文献
4.
Eugenio Díaz-Pinés Andreas Schindlbacher Michael Pfeffer Robert Jandl Sophie Zechmeister-Boltenstern Agustín Rubio 《European Journal of Forest Research》2010,129(1):101-109
We conducted a trenching experiment in a mountain forest in order to assess the contribution of the autotrophic respiration
to total soil respiration and evaluate trenching as a technique to achieve it. We hypothesised that the trenching experiment
would alter both microbial biomass and microbial community structure and that fine roots (less than 2 mm diameter) would be
decomposed within one growing season. Soil CO2 efflux was measured roughly biweekly over two growing seasons. Root presence and morphology parameters, as well as the soil
microbial community were measured prior to trenching, 5 and 15 months after trenching. The trenched plots emitted about 20
and 30% less CO2 than the control plots in the first and second growing season, respectively. Roots died in trenched plots, but root decay
was slow. After 5 and 15 months, fine root biomass was decreased by 9% (not statistically different) and 30%, (statistically
different) respectively. When we corrected for the additional trenched-plot CO2 efflux due to fine root decomposition, the autotrophic soil respiration rose to ~26% of the total soil respiration for the
first growing season, and to ~44% for the second growing season. Soil microbial biomass and community structure was not altered
by the end of the second growing season. We conclude that trenching can give accurate estimates of the autotrophic and heterotrophic
components of soil respiration, if methodological side effects are accounted for, only. 相似文献
5.
Kobler Johannes Zehetgruber Bernhard Dirnböck Thomas Jandl Robert Mirtl Michael Schindlbacher Andreas 《Landscape Ecology》2019,34(2):325-340
Context
Varying altitudes and aspects within small distances are typically found in mountainous areas. Such a complex topography complicates the accurate quantification of forest C dynamics at larger scales.
ObjectivesWe determined the effects of altitude and aspect on forest C cycling in a typical, mountainous catchment in the Northern Limestone Alps.
MethodsForest C pools and fluxes were measured along two altitudinal gradients (650–900 m a.s.l.) at south-west (SW) and north-east (NE) facing slopes. Net ecosystem production (NEP) was estimated using a biometric approach combining field measurements of aboveground biomass and soil CO2 efflux (SR) with allometric functions, root:shoot ratios and empirical SR modeling.
ResultsNEP was higher at the SW facing slope (6.60?±?3.01 t C ha?1 year?1), when compared to the NE facing slope (4.36?±?2.61 t C ha?1 year?1). SR was higher at the SW facing slope too, balancing out any difference in NEP between aspects (NE: 1.30?±?3.23 t C ha?1 year?1, SW: 1.65?±?3.34 t C ha?1 year?1). Soil organic C stocks significantly decreased with altitude. Forest NPP and NEP did not show clear altitudinal trends within the catchment.
ConclusionsUnder current climate conditions, altitude and aspect adversely affect C sequestering and releasing processes, resulting in a relatively uniform forest NEP in the catchment. Hence, including detailed climatic and soil conditions, which are driven by altitude and aspect, will unlikely improve forest NEP estimates at the scale of the studied catchment. In a future climate, however, shifts in temperature and precipitation may disproportionally affect forest C cycling at the southward slopes through increased water limitation.
相似文献6.
The efficiency of an active substance (AL) prepared in our laboratory as a composite sorbent on the basis of hexacyanoferrates (II) bound on pearl cellulose, in affecting the radiocesium (Cs-137) retention in white miniature pigs was investigated. The function of the composite sorbent in dependence on the way of administration, i.e. its effect on a decrease of primary resorption and its ability to interrupt the enteral cycle was studied, too. The efficiency of stable cesium administration in the form of CsCl in the same process was also determined. It was proved that AL accelerated significantly the excretion through its effect both on primary resorption causing an approx. 11-fold reduction of resorption when administered simultaneously with radiocesium and on the enteral cycle, causing an approx. 3.5-fold increase of excretion of Cs-137 when administered daily. Thus the composite sorbent (AL) administered at long-term along with contaminated feed reduced the equilibrium concentration of radiocesium in meat 30-40 times. This might be of great importance in the time of nuclear emergencies. On the other hand, administration of non-active Cs at a level up to 1 mg Cs/1 kg of liveweight had no significant effect on Cs-137 elimination. 相似文献
7.
The concentrations of fatty acids in organo-mineral particle-size fractions of a Chernozem 总被引：3，自引：0，他引：3
G. Jandl P. Leinweber H.-R. Schulten & K. Eusterhues 《European Journal of Soil Science》2004,55(3):459-470
Fatty acids, the most abundant class of soil lipids, indicate pedogenetic processes and soil management. However, their quantitative distribution in organo‐mineral particle‐size fractions is unknown. The concentrations of n‐C10:0 to n‐C34:0 fatty acids both in whole soil samples and in the organo‐mineral particle‐size fractions of the Ap horizon of a Chernozem were determined (i) to evaluate the effects of long‐term fertilization and (ii) to investigate their influence on the aggregation of organo‐mineral primary particles. Quantification by gas chromatography/mass spectrometry (GC/MS) showed that long‐term fertilization with nitrogen, phosphorus and potassium (NPK) and farmyard manure (FYM) led to larger concentrations (25.8 µg g?1) of fatty acids than in the unfertilized sample (22.0 µg g?1). For particle‐size fractions of the unfertilized soil, the fatty acid concentrations increased from the coarse silt to the clay fractions (except for fine silt). Fertilization with NPK and FYM resulted in absolute enrichments of n‐C21:0 to n‐C34:0 fatty acids with a maximum at n‐C28:0 in clay (×2.2), medium silt (×2.0), coarse silt (×1.8) and sand (×2.9) compared with the unfertilized treatment (the factors of enrichment are given in parentheses). New evidence for the aggregate stabilizing function of n‐C21:0 to n‐C34:0 fatty acids was shown by the characteristic pattern in size‐fractionated, disaggregated and aggregated samples. Highly significant correlations of fatty acid concentrations with organic C concentrations and specific surface areas are interpreted as indicators of (i) trapping of fatty acids in organic matter macromolecules and (ii) direct bonding to mineral surfaces. This interpretation was supported by the thermal volatilization and determination of fatty acids by pyrolysis‐field ionization mass spectrometry (Py‐FIMS). 相似文献
8.
Fatty acids as major compounds of soil lipids may affect many soil properties, but the input and turnover rates in soil are largely unknown. The objective of this study was to identify and quantify fatty acids in soils as a result of input from primary sources such as plant residues, farmyard manure and soil organisms, and to evaluate the corresponding turnover- and stabilization processes. The concentrations of n-C10:0 to n-C34:0 fatty acids were determined in the Ap horizon of a Phaeozem with long-term cropping of rye and maize and the treatments ‘Unfertilized’ (‘U’) and fertilized with ‘Farmyard manure’ (‘FYM’). The most important primary sources of fatty acids such as rye and maize stubble and roots, soil micro- and mesofauna, and the applied FYM were also investigated. The quantification of fatty acids by gas chromatography/mass spectrometry (GC/MS) showed that long-term FYM application led to larger concentrations of n-alkyl fatty acids in the plots grown with rye (‘U’: 48.1 μg g−1, ‘FYM’: 57.7 μg g−1, **P≤0.01, n=3) and maize (‘U’: 17.0 μg g−1, ‘FYM’: 23.4 μg g−1, ***P≤0.001, n=3). The observed bimodal fatty acid distribution in soils from n-C10:0 to n-C21:0 and from n-C21:0 to n-C34:0 with a predominance at n-C16:0 and at n-C28:0 was apparently due to input from crop residues, soil organisms and FYM. The short-chain lengths may have originated from the investigated primary sources. The major contributors to the long-chain lengths, with a maximum at n-C28:0, were rye stubble and FYM. A change in mono-culture from rye to maize, 38 years prior to sampling, led to a decrease in fatty acid concentrations by factors of about 2.8 (‘U’) and 2.5 (‘FYM’). Therefore, rye-derived fatty acids and soil tillage had a larger impact on fatty acid pools than the input of primary organic matter. The changes in fatty acid distributions and pools under the consideration of the quantified input of primary organic matter led to the conclusion that the short-chained fatty acids were more rapidly decomposed than the long-chains. 相似文献
9.
10.
Robert Jandl Gerhard Glatzel Klaus Katzensteiner Otto Eckmüllner 《Water, air, and soil pollution》2001,125(1):1-17
Norway spruce has shown needle yellowing and defoliation symptoms on manysites of the Bohemian Forest in north central Austria since theearly 1980s. A forest amelioration experiment was set up toevaluate the response of spruce to magnesite based fertilizerswith different solubilities. Response variables were a crownvigor index, diameter growth, nutrient contents in needles,soil solution chemistry, and soil chemistry. Soil solution atfertilized plots showed an immediate response in base cationconcentrations, nitrate concentrations and pH-values.Fertilization increased the pool of exchangeable cations in theupper 15 cm of the soil and reduced levels of exchangeable Al. Themagnesium and calcium content of the needles of dominant trees wasgreatly improved. Fertilization has increased the mineralizationrate of soil organic matter. Diameter growth, as a measure of treevigor, showed a pronounced positive response with a time delay of5 years. Our results demonstratethat magnesite based fertilizers are a viable option to improvethe nutritional status of spruce forests on granitic bedrock. 相似文献