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Giovanny M. Mosquera Patricio Crespo Lutz Breuer Jan Feyen David Windhorst 《水文研究》2020,34(9):2032-2047
Andosol soils formed in volcanic ash provide key hydrological services in montane environments. To unravel the subsurface water transport and tracer mixing in these soils we conducted a detailed characterization of soil properties and analyzed a 3-year data set of sub-hourly hydrometric and weekly stable isotope data collected at three locations along a steep hillslope. A weakly developed (52–61 cm depth), highly organic andic (Ah) horizon overlaying a mineral (C) horizon was identified, both showing relatively similar properties and subsurface flow dynamics along the hillslope. Soil moisture observations in the Ah horizon showed a fast responding (few hours) “rooted” layer to a depth of 15 cm, overlying a “perched” layer that remained near saturated year-round. The formation of the latter results from the high organic matter (33–42%) and clay (29–31%) content of the Ah horizon and an abrupt hydraulic conductivity reduction in this layer with respect to the rooted layer above. Isotopic signatures revealed that water resides within this soil horizon for short periods, both at the rooted (2 weeks) and perched (4 weeks) layer. A fast soil moisture reaction during rainfall events was also observed in the C horizon, with response times similar to those in the rooted layer. These results indicate that despite the perched layer, which helps sustain the water storage of the soil, a fast vertical mobilization of water through the entire soil profile occurs during rainfall events. The latter being the result of the fast transmissivity of hydraulic potentials through the porous matrix of the Andosols, as evidenced by the exponential shape of the water retention curves of the subsequent horizons. These findings demonstrate that the hydrological behavior of volcanic ash soils resembles that of a “layered sponge,” in which vertical flow paths dominate. 相似文献
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Bergur Sigfusson Sigurdur R. Gislason Graeme I. Paton 《Journal of Geochemical Exploration》2006,88(1-3):321
Histic Andosol in Western Iceland was studied using laboratory based repacked microcosms conjointly with sampling of field soil solution. The main primary phase of the 205 cm thick soil profile was basaltic glass, allophane content ranged from 2 to 22 wt.% and the soil carbon content ranged from 11 to 42 wt.%. At constant temperature, the dissolution rate of the basaltic glass, and probably allophane and imogolite, was dictated by the aH+3 / aAl3+ activity ratio only, which in turn is governed by the pH, total dissolved Al and the anions capable of complexing Al3+; SO42−, F− and organic anions (DOC). Dissolution rate was slowed down by up to 20% by decreasing undersaturation in the field. Dissolution rate of basaltic glass was stable after an initial flushing event at the beginning of microcosm experiments. Predicted dissolution rates increased up to a factor of 7 and 30 by speciating Al3+ with oxalate in field and microcosms respectively. Speciation with oxalate generally had more effect in shallow horizons than deep horizons. 相似文献
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Landslides are a recognized but poorly studied phenomena in the eastern footslopes of the Aberdare ranges in central Kenya.
The Aberdare ranges traverse the Murang'a, Kiambu, Nyeri and Nyandarua districts of Kenya where fatal landslides have occurred
in the past. A detailed study of a major landslide which occurred at Maringa village in Murang'a district on 30 April 1997,
has been undertaken. The landslide buried three houses at the toe of a slope and killed all the 11 occupants in their sleep.
It is shown that the geology and climate of the study area contribute to the prevalence of landslides not only in Murang'a
but in all the andosol-covered areas throughout the eastern footslopes of Aberdare ranges. Rapid weathering of pyroclastic
rocks in a warm and wet climate create a regolith which is generally weaker than the underlying better-cemented basalt and
basaltic agglomerates. The landsliding occurred when the weathered pyroclastic regolith become saturated after a heavy rainstorm
on high mechanically unstable slope which slid over the more stable basalts. Over-saturation of clay soils (andosol) which
were also derived from weathering of pyroclastic rocks contributed to the slope failure. The results of the study show that
besides fatalities and injuries, the landslide destroyed homes, plantations and roads.
Received: 16 March 1998 · Accepted: 22 September 1998 相似文献
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In this article the effect of redistribution of rainfall by banana on local water fluxes and the possible impact of these fluxes on surface runoff has been studied. First the water redistribution by a banana canopy at three development stages (vegetative, flowering, and bunch stage) was measured. The results showed a considerable stemflow, proportional to the leaf area index (LAI), which represented 18 to 26% of the incident rainfall volume according to the age of the crop. Consequently, the rainfall rate was 28‐fold higher at the plant collar for a fully developed banana canopy. For the throughfall, on average, the higher the LAI, the lower the mean throughfall. In addition, the spatial distribution of the throughfall varied according to the distance from the pseudostem. Notably, for the earlier stages, the area between the pseudostem and 0·5 m from it received weak throughfall. Secondly, simulations were carried out with a simple two‐compartment model simulating the total surface runoff volume. The simulations showed stemflow combined with the agronomical practice of furrowing has an effect on runoff compared to bare soil. A relative increase in surface runoff volume of three‐fold was encountered on a plot with a fully developed banana and a infiltration rate of 60 mm h?1. However, the absolute increase was only a few percentage of the incident rainfall volume, although it represented large water volumes given the tropical rains. These features must be taken into account for hydrological management of such systems. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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Giovanny M. Mosquera Marín Franklin Feyen Jan Célleri Rolando Breuer Lutz Windhorst David Crespo Patricio 《水文研究》2021,35(1):e14011
Accurate determination of the water retention curve (WRC) of a soil is essential for the understanding and modelling of the subsurface hydrological, ecological, and biogeochemical processes. Volcanic ash soils with andic properties (Andosols) are recognized as important providers of ecological and hydrological services in mountainous regions worldwide due to their large fraction of small size particles (clay, silt, and organic matter) that gives them an outstanding water holding capacity. Previous comparative analyses of in situ (field) and standard laboratory methods for the determination of the WRC of Andosols showed contrasting results. Based on an extensive analysis of laboratory, experimental, and field measured WRCs of Andosols in combination with data extracted from the published literature we show that standard laboratory methods using small soil sample volumes (≤300 cm3) mimic the WRC of these soils only partially. The results obtained by the latter resemble only a small portion of the wet range of the Andosols' WRC (from saturation up to −5 kPa, or pF 1.7), but overestimate substantially their water content for higher matric potentials. This discrepancy occurs irrespective of site-specific land use and cover, soil properties, and applied method. The disagreement limits our capacity to infer correctly subsurface hydrological behaviour, as illustrated through the analysis of long-term soil moisture and matric potential data from an experimental site in the tropical Andes. These findings imply that results reported in past research should be used with caution and that future research should focus on determining laboratory methods that allow obtaining a correct characterization of the WRC of Andosols. For the latter, a set of recommendations and future directions to solve the identified methodological issues is proposed. 相似文献
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