ABSTRACT Icelandic Andosols form in climatic and geological conditions that are different from th... more ABSTRACT Icelandic Andosols form in climatic and geological conditions that are different from those common for Andosol formation, namely a frigid oceanic climate and the steady aeolian addition of fresh and reworked tephra material. Three representative profiles were sampled in different ecological zones of Iceland for -micromorphological studies. They are classified as Orthidystri-Vitric Andosol, -Dystri-Vitric Andosol and Thaptohistic-Vitric Andosol. The parent material consists entirely of relatively young volcanic ashes, and organic layers. Multiple lithological discontinuities are recognised. Microstratification is observed in thin sections, both in organic and inorganic horizons. The coarse mineral fraction is characterised by variable proportions of pumice, different types of glass, hypo- and holocrystalline pyroclasts and euhedral and subhedral crystals of feldspar and augite. Locally, green-grey volcanic glass shows pellicular alteration to an orange component, considered as palagonite. Some more clayey horizons (described as B horizons in the field) consist of soil aggregates or nodules of various compositions, mixed with pyroclasts covered by a coating of micromass. They may represent locally transported material of older, more evolved soils. The microstratification of both organic and mineral material and the (sub)-horizontal orientation of organ and tissue residues points to a gradual deposition of material, with short interruptions, not disturbed by pedoturbation, especially bioturbation. It means that every sub-layer corresponds to a former soil surface in a temporarily relatively stable environment. A weakly developed lenticular or isoband microstructure, pointing to freeze-thawing phenomena, is observed in several -horizons. Capping, often with reverse sorting, observed between 100-230 cm depth on organ residues in one of the profiles are signs of former frost activity. It is perhaps the first time that such cappings are reported on organic components. The relative pureness of most mineral layers, the freshness of the volcanic components and their sorting indicate in many cases direct deposition during eruptions, rather than a water or air transport over land.
Fallout 137Cs levels in soil were measured at 11 diverse sites throughout Montana. Concentrations... more Fallout 137Cs levels in soil were measured at 11 diverse sites throughout Montana. Concentrations in near-surface samples ranged from 20-200 mBq g-1 (0.51-5.41 pCi g-1). Most of the 137Cs was in the top 10 cm of soil. Deeper occurrences were attributed to disturbances by animals and to interstitial flow of small sediment particles within saturated soils. The areal concentrations ranged from 130-748 mBq cm-2 (3.6-20.2 pCi cm-2) and were highly correlated with annual precipitation.
The extensive soil erosion in Iceland during the past millennium has led to an irregular distribu... more The extensive soil erosion in Iceland during the past millennium has led to an irregular distribution of soil organic carbon (SOC). Intact and fully vegetated areas typically have Andosols with large amounts of organic carbon, whereas eroded areas are barren deserts with little organic carbon. We estimate the amount of organic carbon eroded during the past millennium is 120–500×106 t,
Iceland has the largest area of volcaniclastic sandy desert on Earth or 22,000 km2. The sand has ... more Iceland has the largest area of volcaniclastic sandy desert on Earth or 22,000 km2. The sand has been mostly produced by glacio-fluvial processes, leaving behind fine-grained unstable sediments which are later re-distributed by repeated aeolian events. Volcanic eruptions add to this pool of unstable sediments, often from subglacial eruptions. Icelandic desert surfaces are divided into sand fields, sandy lavas and sandy lag gravel, each with separate aeolian surface characteristics such as threshold velocities. Storms are frequent due to Iceland’s location on the North Atlantic Storm track. Dry winds occur on the leeward sides of mountains and glaciers, in spite of the high moisture content of the Atlantic cyclones. Surface winds often move hundreds to more than 1000 kg m-1 per annum, and more than 10,000 kg m-1 have been measured in a single storm. Desertification occurs when aeolian processes push sand fronts and have thus destroyed many previously fully vegetated ecosystems since ...
Icelandic topsoil sediments, as confirmed by numerous scientific studies, represent the largest a... more Icelandic topsoil sediments, as confirmed by numerous scientific studies, represent the largest and the most important European source of mineral dust. Strong winds, connected with the intensive cyclonic circulation in the North Atlantic, induce intense emissions of mineral dust from local sources all year and carry away these fine aerosol particles for thousands of kilometers. Various impacts of airborne mineral dust particles on local air quality, human health, transportation, climate and marine ecosystems motivated us to design a fully dynamic coupled atmosphere–dust numerical modelling system in order to simulate, predict and quantify the Icelandic mineral dust process including: local measurements and source specification over Iceland. In this study, we used the Dust Regional Atmospheric Model (DREAM) with improved Icelandic high resolution dust source specification and implemented spatially variable particle size distribution, variable snow cover and soil wetness. Three case s...
ABSTRACT Icelandic Andosols form in climatic and geological conditions that are different from th... more ABSTRACT Icelandic Andosols form in climatic and geological conditions that are different from those common for Andosol formation, namely a frigid oceanic climate and the steady aeolian addition of fresh and reworked tephra material. Three representative profiles were sampled in different ecological zones of Iceland for -micromorphological studies. They are classified as Orthidystri-Vitric Andosol, -Dystri-Vitric Andosol and Thaptohistic-Vitric Andosol. The parent material consists entirely of relatively young volcanic ashes, and organic layers. Multiple lithological discontinuities are recognised. Microstratification is observed in thin sections, both in organic and inorganic horizons. The coarse mineral fraction is characterised by variable proportions of pumice, different types of glass, hypo- and holocrystalline pyroclasts and euhedral and subhedral crystals of feldspar and augite. Locally, green-grey volcanic glass shows pellicular alteration to an orange component, considered as palagonite. Some more clayey horizons (described as B horizons in the field) consist of soil aggregates or nodules of various compositions, mixed with pyroclasts covered by a coating of micromass. They may represent locally transported material of older, more evolved soils. The microstratification of both organic and mineral material and the (sub)-horizontal orientation of organ and tissue residues points to a gradual deposition of material, with short interruptions, not disturbed by pedoturbation, especially bioturbation. It means that every sub-layer corresponds to a former soil surface in a temporarily relatively stable environment. A weakly developed lenticular or isoband microstructure, pointing to freeze-thawing phenomena, is observed in several -horizons. Capping, often with reverse sorting, observed between 100-230 cm depth on organ residues in one of the profiles are signs of former frost activity. It is perhaps the first time that such cappings are reported on organic components. The relative pureness of most mineral layers, the freshness of the volcanic components and their sorting indicate in many cases direct deposition during eruptions, rather than a water or air transport over land.
Fallout 137Cs levels in soil were measured at 11 diverse sites throughout Montana. Concentrations... more Fallout 137Cs levels in soil were measured at 11 diverse sites throughout Montana. Concentrations in near-surface samples ranged from 20-200 mBq g-1 (0.51-5.41 pCi g-1). Most of the 137Cs was in the top 10 cm of soil. Deeper occurrences were attributed to disturbances by animals and to interstitial flow of small sediment particles within saturated soils. The areal concentrations ranged from 130-748 mBq cm-2 (3.6-20.2 pCi cm-2) and were highly correlated with annual precipitation.
The extensive soil erosion in Iceland during the past millennium has led to an irregular distribu... more The extensive soil erosion in Iceland during the past millennium has led to an irregular distribution of soil organic carbon (SOC). Intact and fully vegetated areas typically have Andosols with large amounts of organic carbon, whereas eroded areas are barren deserts with little organic carbon. We estimate the amount of organic carbon eroded during the past millennium is 120–500×106 t,
Iceland has the largest area of volcaniclastic sandy desert on Earth or 22,000 km2. The sand has ... more Iceland has the largest area of volcaniclastic sandy desert on Earth or 22,000 km2. The sand has been mostly produced by glacio-fluvial processes, leaving behind fine-grained unstable sediments which are later re-distributed by repeated aeolian events. Volcanic eruptions add to this pool of unstable sediments, often from subglacial eruptions. Icelandic desert surfaces are divided into sand fields, sandy lavas and sandy lag gravel, each with separate aeolian surface characteristics such as threshold velocities. Storms are frequent due to Iceland’s location on the North Atlantic Storm track. Dry winds occur on the leeward sides of mountains and glaciers, in spite of the high moisture content of the Atlantic cyclones. Surface winds often move hundreds to more than 1000 kg m-1 per annum, and more than 10,000 kg m-1 have been measured in a single storm. Desertification occurs when aeolian processes push sand fronts and have thus destroyed many previously fully vegetated ecosystems since ...
Icelandic topsoil sediments, as confirmed by numerous scientific studies, represent the largest a... more Icelandic topsoil sediments, as confirmed by numerous scientific studies, represent the largest and the most important European source of mineral dust. Strong winds, connected with the intensive cyclonic circulation in the North Atlantic, induce intense emissions of mineral dust from local sources all year and carry away these fine aerosol particles for thousands of kilometers. Various impacts of airborne mineral dust particles on local air quality, human health, transportation, climate and marine ecosystems motivated us to design a fully dynamic coupled atmosphere–dust numerical modelling system in order to simulate, predict and quantify the Icelandic mineral dust process including: local measurements and source specification over Iceland. In this study, we used the Dust Regional Atmospheric Model (DREAM) with improved Icelandic high resolution dust source specification and implemented spatially variable particle size distribution, variable snow cover and soil wetness. Three case s...
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Papers by Olafur Arnalds