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Friese K. Wendt-Potthoff K. Zachmann D.W. Fauville A. Mayer B. Veizer J. 《Water, air, and soil pollution》1998,108(3-4):231-247
Chemical, microbiological and stable isotope analyses of sediments from an acidic mining lake were used to evaluate whether biogeochemical processes, such as iron and sulfate reduction, are extant, because such processes can potentially generate alkalinity. Sediment cores were sliced in cm intervals to achieve a high resolution for spatial distribution of organic and inorganic components. Iron, sulfur, carbon, nitrogen and phosphorus as well as the most probable number (MPN) of iron reducing bacteria, the amount of lipid phosphate and the stable isotope compositions of various sedimentary sulfur compounds were measured. Accumulation of degradable organic material, reduced mass fractions of iron, enhanced concentrations of lipid phosphate, high concentrations of DOC and ferrous iron in the pore water and a drastic change of sulfur isotope ratios in the upper 3 cm of the sediment all indicated a highly reactive zone of biogeochemical transformations. The data provide clear evidence for iron and sulfate reducing processes in the sediments that result in an increase of pH with depth. 相似文献
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The lead smelting site near Clausthal-Zellerfeld (Harz Mountains, Germany) was in operation for 700 years. As a result of this long operating time, the soil and stream sediments in the vicinity of the site are highly contaminated due to airborne pollution and dumping of slags. The knowledge of bulk concentrations does not give sufficient information for an estimate of the hazard potential stored in the contaminated materials. Therefore, as a first step, the element speciation in the three sample populations was determined. As the extractability (availability) of the speciations varies significantly for the different elements, a second step was used to test for the availability. The investigations on the availabilities yield a very high hazard potential for lead, followed by Cu and Zn. 相似文献
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R. Zachmann 《American Journal of Potato Research》1977,54(6):253-260
Nine basidiospore populations ofRhizoctonia solani were collected in four different environments: The Peruvian tropical lowlands, the Peruvian Andes, Mexico, and in a greenhouse experiment, totalling 328 individual isolates. Visually these isolates showed high variability on agar media and considerable overlapping of morphological characteristics between populations was observed. Nevertheless, some grouping was suspected. Discriminant and cluster analyses confirmed a discontinuity of variation among all populations, except in those from the Peruvian tropics. The Peruvian tropical isolates were found to be more or less similar to each other, but different from the other populations. 相似文献
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The frequency and size of wildfires within the Mojave Desert are increasing, possibly due to climate and land cover changes and associated increases in non-native invasive plant biomass, as measured by normalized difference vegetation index (NDVI). These patterns are of particular concern to resource managers in regions where native plant communities are not well adapted to fire. We used an information-theoretic and mixed-model approach to quantify the importance of multiple environmental variables in predicting, separately, the probabilities of occurrence of all fires and the occurrence large (>20 ha) fires in five management units administered by the National Park Service in the Mojave Desert Network and based on fire ignition data obtained for the period 1992–2011. Fire occurrence was strongly associated with areas close to roads, high maximum NDVI values in the year preceding ignition, the desert montane ecological zone, and high topographic roughness. Large fire probability was strongly associated with lightning-caused ignition events, high maximum NDVI values in the spring preceding ignition, high topographic roughness, the middle-elevation shrubland ecological zone, and areas further from roads. Our probabilistic models and maps can be used to explore patterns of fire occurrence based upon variability in NDVI values and to assess the vulnerability of Mojave Desert protected areas to undesirable fire events. 相似文献
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