共查询到20条相似文献，搜索用时 859 毫秒
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M.M. Mortland 《Geoderma》1980,23(3):225-226
Weathering products of Vitrandept profiles on the Kaingaroa plateau, central North Island, New Zealand, were investigated by analysis of oxalate extracts and by chemical and mineralogical analysis of clays of selected soil horizons. Comparisons were made between profiles under a Pinus radiata (D. Don) stand and profiles under an adjacent area of manuka native scrub, Leptospermum scoparium (Myrtaceae).Clay fractions (< 2 μm) of A11 horizon under pine had significantly higher SiO2/Al2O3 mole-ratios (mean SiO2/Al2O3 = 12.2) than A11 horizon under manuka (mean SiO2/Al2O3 = 7.1). No effect of vegetation on clay fractions of B horizon was evident, these clays having much lower SiO2/Al2O3 mole-ratio (1.5). Oxalate-extractable Al, Fe and Si values of < 8-mm fractions of A, B and C horizons showed no differences attributable to present vegetative cover.SiO2/Al2O3 mole-ratios of oxalate extracts increased with increasing depth, and paleosols at > 2 m depth under pine had significantly higher SiO2/Al2O3 mole-ratios in oxalate extracts (mean SiO2/Al2O3 = 2.0) than paleosols under manuka (mean SiO2/Al2O3 = 1.6). That soil horizons at > 2 m depth are in the zone of resilication is indicated by: (1) the greater SiO2/Al2O3 mole-ratios of oxalate extracts of paleosols than surface horizons; (2) lysimeter leachate composition; and (3) the presence of authigenic halloysite at > 2 m depth in soil profiles. 相似文献
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Detailed soil mapping in the Ransdalerveld area pointed to the occurrence of clay soils of different ages, characteristics and genesis. Three representative soil profiles were therefore selected and studied in detail.In this first of three articles, some observations and conclusions on the distribution, age and characteristics of these soils are presented. The “old” soils, developed on the plateaus in predominantly limestone-weathering residues, are classified as Lithic Hapludalfs, whereas the “young” soils on the valley slopes are classified as Rendollic Eutrochrepts if they lack a loess cover and as Typic Hapludalfs if they have a loess cover. Weathering and soil formation are discussed in the second and third parts. 相似文献
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W A Pons 《Journal of the Association of Official Analytical Chemists》1976,59(1):101-105
Aflatoxins were completely resolved as sharp peaks in the order BU-B2-G1-G2 by high-pressure liquid chromatography on a small particle (10 mum) porous silica gel column in 7-13 min (B1 through G2) by a water-saturated chloroform-cyclohexane-acetonitrile elution solvent (25+7.5+1.0), with detection by ultraviolet absorbance at 360 nm. The relationship between peak height and amount injected was linear over a 5-400 ng range for each aflatoxin. Both retention times and peak heights were highly reproducible, multiple injections of mixed standards giving coefficients of variation of 1.0-1.4% (retention time) and 1.6-2.8% (peak height) for the 4 aflatoxins. Detection was highly sensitive, with mean peak height, mm/ng, of 7.1 (B1), 6.4 (B2), 4.5 (G1), and 4.1(G2), allowing detection of 1-2 ng of each aflatoxin. 相似文献
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Tepetates are common in the Mexican highlands, and are classified as fragipan, duripan, pedosediments or saprolite. A common feature is the abundance of clay coatings. Three pedons with red tepetate and grey tepetate were selected at different altitudes and slopes in a small watershed in Texcoco, Mexico. Physical, chemical, mineralogical and micromorphological analyses were carried out in soil, tepetate and separated clay coatings. Clay illuviation and neoformation indexes were calculated using micromorphometric techniques. Red tepetate is composed of basic volcanic glass dust (andesitic vitric tuff), and has a high clay neoformation and illuviation index. In contrast, grey tepetate is composed of acid volcanic glass (acid vitric tuff) and only clay neoformation takes place, leading to the formation of a clayey soil. Although all the tepetates were subject to pedogenesis, the intensity and variation of the processes increases on the lower slope and different diagnostic horizons are formed, due to tepetate erosion. The laterally running waters containing suspensions of particles and soluble silica were deposited or precipitated in sediments or tepetates on the lower slopes, giving rise to compound coatings. These processes must be older than 20,000 years. Tepetates from Texcoco present several variants which were recognised since pre-Hispanic times. 相似文献
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Hans Ruppert 《Water, air, and soil pollution》1975,4(3-4):447-460
The concentration of 27 elements was investigated in 10 samples of precipitation from Göttingen, collected during May and September 1972. Göttingen is a non-industrial town of 130000 inhabitants, situated in a rural area, and essentially all the dissolved and undissolved material in rainwater is locally derived. Elemental concentrations in freshwater and shale are used for comparison with the dissolved elements in precipitation and the undissolved residue. The two phases have been separated after evaporation (concentration factors: 15 to 25-times). Phosphorous, Zn, Mn, and Pb are enriched in rainwater, while Si, Mg, Na, Ca, Cl, Fe, Hg, K, Li, and Al are depleted relative to average freshwater. Sulfate, Cd, and Cu have similar concentrations in rain and freshwater. The factors of accumulation between elements in residue and average shale are calculated after normalization to the Al-value. They are: ? 100 for Ag, Hg, Pb; between 10 and 20 for Zn, Cd, P, Cu, Mo; > 2 for Cr, Bi, Ni, Ba, Ti, V ; between 0.9 and 2.0 for Rb, K, Na, Li, Mg, Mn, Fe, Si, Ca; and 0.5 for Tl. The trace element accumulation is due to different anthropogenic sources: combustion of liquid petroleum fuels contributes to Ph, V, Ni, Mo, Hg, and sulfate, combustion of coal to Ba, sulfate, and chloride, and to the. readily volatile elements such as Hg, Cd, Tl, Bi, and Ag, combustion of refuse to Ag, Bi, Pb, Cd, Hg, Zn, Cr, Cu, Ba, and Mo in highly variable amounts. Fertilizers and road salts change the chemistry of soils and indirectly supply P, alkali and alkaline-earth metals to the fly dust. Modest industrial activity is responsible for high Cu and Cr concentrations. Despite the appreciable accumulation of some toxic elements, the precipitation in Göttingen is relatively pure compared to other areas. Favorable geologic conditions around Göttingen decrease the negative influences of potentially harmful airborne elements. The high carbonate content in the dust neutralizes the anthropogenic acids in the rainwater. Furthermore, the toxic trace elements are diluted, especially in the center of Göttingen, by a large amount of airborne dust. 相似文献
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Water, Air, &; Soil Pollution - 相似文献
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E.G. Youngs 《Soil & Tillage Research》1984,4(5):485-486