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A.j Melfi - One of the best experts on this subject based on the ideXlab platform.
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Podzolization as a deferralitization process: dynamics and chemistry of ground and surface waters in an Acrisol – Podzol sequence of the upper Amazon Basin
European Journal of Soil Science, 2008Co-Authors: N.r Do Nascimento, E. Fritsch, G.t. Bueno, M. Bardy, A.j Melfi, C. GrimaldiAbstract:Hydrochemical processes involved in the development of hydromorphic Podzols are a major concern for the upper Amazon Basin because of the extent of the areas affected by such processes and the large amounts of organic carbon and associated metals exported to the rivers. The dynamics and chemical composition of ground and surface waters were studied along an Acrisol-Podzol sequence lying in an open depression of a plateau. Water levels were monitored along the sequence over a period of 2 years by means of piezometers. Water was sampled in zero-tension lysimeters for groundwater and for surface water in the drainage network of the depression. The pH and concentrations of organic carbon and major elements (Si, Fe and Al) were determined. The contrasted changes reported for concentrations of Si, organic carbon and metals (Fe, Al) mainly reflect the dynamics of the groundwater and the weathering conditions that prevail in the soils. Iron is released by the reductive dissolution of Fe oxides, mostly in the Bg Horizons of the upslope Acrisols. It moves laterally under the control of hydraulic gradients and migrates through the iron-depleted Podzols where it is exported to the river network. Aluminium is released from the dissolution of Al-bearing minerals (gibbsite and kaolinite) at the margin of the podzolic area but is immobilized as organo-Al complexes in Spodic Horizons. In downslope positions, the quick recharge of the groundwater and large release of organic compounds lead to acidification and a loss of metals (mainly Al), previously stored in the Podzols.
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Podzolization as a deferralitization process: a study of an Acrisol–Podzol sequence derived from Palaeozoic sandstones in the northern upper Amazon Basin.
European Journal of Soil Science, 2004Co-Authors: N.r.-do Nascimento, A J Herbillon, E. Fritsch, G.t. Bueno, A.j Melfi, Th. Allard, R. Astolfo, H. BoucherAbstract:Morphological, geochemical and mineralogical studies were carried out in a representative soil catena of the low-elevation plateaux of the upper Amazon Basin to interpret the steps and mechanisms involved in the podzolization of low-activity clay soils. The soils are derived from Palaeozoic sandstones. They consist of Hydromorphic Podzols under tree savannah in the depressions of the plateaux and predominantly of Acrisols covered by evergreen forest elsewhere. Incipient podzolization in the uppermost Acrisols is related to the formation of organic-rich A and Bhs Horizons slightly depleted in fine-size particles by both mechanical particle transfer and weathering. Weathering of secondary minerals by organic acids and formation of organo-metallic complexes act simultaneously over short distances. Their vertical transfer is limited. Selective dissolution of aluminous goethite, then gibbsite and finally kaolinite favour the preferential cheluviation of first Fe and secondly Al. The relatively small amount of organo-metallic complexes produced is related to the quartzitic parent materials, and the predominance of Al over Fe in the Spodic Horizons is due to the importance of gibbsite in these low-activity clay soils. Morphologically well-expressed podzols occur in strongly iron-depleted topsoils of the depression. Mechanical transfer and weathering of gibbsite and kaolinite by organic acids is enhanced and leads to residual accumulation of sands. Organo-metallic complexes are translocated in strongly permeable sandy Horizons and impregnate at depth the macro-voids of embedded soil and saprolite materials to form the Spodic Bs and 2BCs Horizons. Mechanical transfer of black particulate organic compounds devoid of metals has occurred later within the sandy Horizons of the podzols. Their vertical transfer has formed well-differentiated A and Bh Horizons. Their lateral removal by groundwater favours the development of an albic E horizon. In an open and waterlogged environment, the general trend is therefore towards the removal of all the metals that have initially accumulated as a response to the ferralitization process and have temporarily been sequestrated in organic complexes in previous stages of soil podzolization.
G.t. Bueno - One of the best experts on this subject based on the ideXlab platform.
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Podzolization as a deferralitization process: dynamics and chemistry of ground and surface waters in an Acrisol – Podzol sequence of the upper Amazon Basin
European Journal of Soil Science, 2008Co-Authors: N.r Do Nascimento, E. Fritsch, G.t. Bueno, M. Bardy, A.j Melfi, C. GrimaldiAbstract:Hydrochemical processes involved in the development of hydromorphic Podzols are a major concern for the upper Amazon Basin because of the extent of the areas affected by such processes and the large amounts of organic carbon and associated metals exported to the rivers. The dynamics and chemical composition of ground and surface waters were studied along an Acrisol-Podzol sequence lying in an open depression of a plateau. Water levels were monitored along the sequence over a period of 2 years by means of piezometers. Water was sampled in zero-tension lysimeters for groundwater and for surface water in the drainage network of the depression. The pH and concentrations of organic carbon and major elements (Si, Fe and Al) were determined. The contrasted changes reported for concentrations of Si, organic carbon and metals (Fe, Al) mainly reflect the dynamics of the groundwater and the weathering conditions that prevail in the soils. Iron is released by the reductive dissolution of Fe oxides, mostly in the Bg Horizons of the upslope Acrisols. It moves laterally under the control of hydraulic gradients and migrates through the iron-depleted Podzols where it is exported to the river network. Aluminium is released from the dissolution of Al-bearing minerals (gibbsite and kaolinite) at the margin of the podzolic area but is immobilized as organo-Al complexes in Spodic Horizons. In downslope positions, the quick recharge of the groundwater and large release of organic compounds lead to acidification and a loss of metals (mainly Al), previously stored in the Podzols.
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Podzolization as a deferralitization process: a study of an Acrisol–Podzol sequence derived from Palaeozoic sandstones in the northern upper Amazon Basin.
European Journal of Soil Science, 2004Co-Authors: N.r.-do Nascimento, A J Herbillon, E. Fritsch, G.t. Bueno, A.j Melfi, Th. Allard, R. Astolfo, H. BoucherAbstract:Morphological, geochemical and mineralogical studies were carried out in a representative soil catena of the low-elevation plateaux of the upper Amazon Basin to interpret the steps and mechanisms involved in the podzolization of low-activity clay soils. The soils are derived from Palaeozoic sandstones. They consist of Hydromorphic Podzols under tree savannah in the depressions of the plateaux and predominantly of Acrisols covered by evergreen forest elsewhere. Incipient podzolization in the uppermost Acrisols is related to the formation of organic-rich A and Bhs Horizons slightly depleted in fine-size particles by both mechanical particle transfer and weathering. Weathering of secondary minerals by organic acids and formation of organo-metallic complexes act simultaneously over short distances. Their vertical transfer is limited. Selective dissolution of aluminous goethite, then gibbsite and finally kaolinite favour the preferential cheluviation of first Fe and secondly Al. The relatively small amount of organo-metallic complexes produced is related to the quartzitic parent materials, and the predominance of Al over Fe in the Spodic Horizons is due to the importance of gibbsite in these low-activity clay soils. Morphologically well-expressed podzols occur in strongly iron-depleted topsoils of the depression. Mechanical transfer and weathering of gibbsite and kaolinite by organic acids is enhanced and leads to residual accumulation of sands. Organo-metallic complexes are translocated in strongly permeable sandy Horizons and impregnate at depth the macro-voids of embedded soil and saprolite materials to form the Spodic Bs and 2BCs Horizons. Mechanical transfer of black particulate organic compounds devoid of metals has occurred later within the sandy Horizons of the podzols. Their vertical transfer has formed well-differentiated A and Bh Horizons. Their lateral removal by groundwater favours the development of an albic E horizon. In an open and waterlogged environment, the general trend is therefore towards the removal of all the metals that have initially accumulated as a response to the ferralitization process and have temporarily been sequestrated in organic complexes in previous stages of soil podzolization.
E. Fritsch - One of the best experts on this subject based on the ideXlab platform.
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Podzolization as a deferralitization process: dynamics and chemistry of ground and surface waters in an Acrisol – Podzol sequence of the upper Amazon Basin
European Journal of Soil Science, 2008Co-Authors: N.r Do Nascimento, E. Fritsch, G.t. Bueno, M. Bardy, A.j Melfi, C. GrimaldiAbstract:Hydrochemical processes involved in the development of hydromorphic Podzols are a major concern for the upper Amazon Basin because of the extent of the areas affected by such processes and the large amounts of organic carbon and associated metals exported to the rivers. The dynamics and chemical composition of ground and surface waters were studied along an Acrisol-Podzol sequence lying in an open depression of a plateau. Water levels were monitored along the sequence over a period of 2 years by means of piezometers. Water was sampled in zero-tension lysimeters for groundwater and for surface water in the drainage network of the depression. The pH and concentrations of organic carbon and major elements (Si, Fe and Al) were determined. The contrasted changes reported for concentrations of Si, organic carbon and metals (Fe, Al) mainly reflect the dynamics of the groundwater and the weathering conditions that prevail in the soils. Iron is released by the reductive dissolution of Fe oxides, mostly in the Bg Horizons of the upslope Acrisols. It moves laterally under the control of hydraulic gradients and migrates through the iron-depleted Podzols where it is exported to the river network. Aluminium is released from the dissolution of Al-bearing minerals (gibbsite and kaolinite) at the margin of the podzolic area but is immobilized as organo-Al complexes in Spodic Horizons. In downslope positions, the quick recharge of the groundwater and large release of organic compounds lead to acidification and a loss of metals (mainly Al), previously stored in the Podzols.
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Podzolization as a deferralitization process: a study of an Acrisol–Podzol sequence derived from Palaeozoic sandstones in the northern upper Amazon Basin.
European Journal of Soil Science, 2004Co-Authors: N.r.-do Nascimento, A J Herbillon, E. Fritsch, G.t. Bueno, A.j Melfi, Th. Allard, R. Astolfo, H. BoucherAbstract:Morphological, geochemical and mineralogical studies were carried out in a representative soil catena of the low-elevation plateaux of the upper Amazon Basin to interpret the steps and mechanisms involved in the podzolization of low-activity clay soils. The soils are derived from Palaeozoic sandstones. They consist of Hydromorphic Podzols under tree savannah in the depressions of the plateaux and predominantly of Acrisols covered by evergreen forest elsewhere. Incipient podzolization in the uppermost Acrisols is related to the formation of organic-rich A and Bhs Horizons slightly depleted in fine-size particles by both mechanical particle transfer and weathering. Weathering of secondary minerals by organic acids and formation of organo-metallic complexes act simultaneously over short distances. Their vertical transfer is limited. Selective dissolution of aluminous goethite, then gibbsite and finally kaolinite favour the preferential cheluviation of first Fe and secondly Al. The relatively small amount of organo-metallic complexes produced is related to the quartzitic parent materials, and the predominance of Al over Fe in the Spodic Horizons is due to the importance of gibbsite in these low-activity clay soils. Morphologically well-expressed podzols occur in strongly iron-depleted topsoils of the depression. Mechanical transfer and weathering of gibbsite and kaolinite by organic acids is enhanced and leads to residual accumulation of sands. Organo-metallic complexes are translocated in strongly permeable sandy Horizons and impregnate at depth the macro-voids of embedded soil and saprolite materials to form the Spodic Bs and 2BCs Horizons. Mechanical transfer of black particulate organic compounds devoid of metals has occurred later within the sandy Horizons of the podzols. Their vertical transfer has formed well-differentiated A and Bh Horizons. Their lateral removal by groundwater favours the development of an albic E horizon. In an open and waterlogged environment, the general trend is therefore towards the removal of all the metals that have initially accumulated as a response to the ferralitization process and have temporarily been sequestrated in organic complexes in previous stages of soil podzolization.
Jozef Deckers - One of the best experts on this subject based on the ideXlab platform.
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Retention and release of Zn and Cd in Spodic Horizons as determined by pHstat analysis and single extractions
Science of The Total Environment, 2007Co-Authors: Liesbeth Horckmans, Rudy Swennen, Jozef DeckersAbstract:Abstract In the northern Campine in Belgium, large areas are contaminated by heavy metals such as Zn and Cd due to the (former) non-ferro metal industry. In the sandy soils, the heavy metal adsorption/attenuation in the Spodic horizon represents the main retention mechanism of leached pollutants from the contaminated topsoils. In this study, the pH-dependent behaviour of the elements in these Spodic Horizons was tested by pH stat experiments and compared to sandy loam soils. Extractions with CaCl 2 0.01 M and EDTA 0.05 M provided a further insight into the binding mechanisms. The results indicate that organic matter is the main factor responsible for the mobility of Cd, Zn and Ca in the Spodic Horizons. The binding of elements is not very strong, however, and highly dependent on pH. A slight decrease in pH can cause a significant release of metals from the Spodic Horizons, with up to 60% of Cd and 90% of Zn being released within a 1.5 unit change in pH (starting from the naturally occurring pH). This pH change can happen rapidly in these soils, due to the low buffering capacity, and is realistic given the acidification in Flanders. For the sandy loam soils, a pH decrease of 3 units is needed to release 40% of Cd and 20% of Zn, and the acid neutralization capacity is exhausted more gradually, suggesting that slower buffering mechanisms take place. For the sandy loam soils, Cd retention is mainly governed by organic matter, while for Zn other factors such as the clay minerals also play an important role. Despite the high potential mobility and pH dependence of the heavy metal retention in the Spodic Horizons, the actual risk for groundwater pollution is limited. For the diffusely contaminated areas, where traditional remediation is not an option, Spodic Horizons may therefore contribute to a natural attenuation of the soil contamination.
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Retention and release of Zn and Cd in Spodic Horizons as determined by pH(stat) analysis and single extractions.
The Science of the total environment, 2007Co-Authors: Liesbeth Horckmans, Rudy Swennen, Jozef DeckersAbstract:In the northern Campine in Belgium, large areas are contaminated by heavy metals such as Zn and Cd due to the (former) non-ferro metal industry. In the sandy soils, the heavy metal adsorption/attenuation in the Spodic horizon represents the main retention mechanism of leached pollutants from the contaminated topsoils. In this study, the pH-dependent behaviour of the elements in these Spodic Horizons was tested by pH(stat) experiments and compared to sandy loam soils. Extractions with CaCl(2) 0.01 M and EDTA 0.05 M provided a further insight into the binding mechanisms. The results indicate that organic matter is the main factor responsible for the mobility of Cd, Zn and Ca in the Spodic Horizons. The binding of elements is not very strong, however, and highly dependent on pH. A slight decrease in pH can cause a significant release of metals from the Spodic Horizons, with up to 60% of Cd and 90% of Zn being released within a 1.5 unit change in pH (starting from the naturally occurring pH). This pH change can happen rapidly in these soils, due to the low buffering capacity, and is realistic given the acidification in Flanders. For the sandy loam soils, a pH decrease of 3 units is needed to release 40% of Cd and 20% of Zn, and the acid neutralization capacity is exhausted more gradually, suggesting that slower buffering mechanisms take place. For the sandy loam soils, Cd retention is mainly governed by organic matter, while for Zn other factors such as the clay minerals also play an important role. Despite the high potential mobility and pH dependence of the heavy metal retention in the Spodic Horizons, the actual risk for groundwater pollution is limited. For the diffusely contaminated areas, where traditional remediation is not an option, Spodic Horizons may therefore contribute to a natural attenuation of the soil contamination.
C. Grimaldi - One of the best experts on this subject based on the ideXlab platform.
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Podzolization as a deferralitization process: dynamics and chemistry of ground and surface waters in an Acrisol – Podzol sequence of the upper Amazon Basin
European Journal of Soil Science, 2008Co-Authors: N.r Do Nascimento, E. Fritsch, G.t. Bueno, M. Bardy, A.j Melfi, C. GrimaldiAbstract:Hydrochemical processes involved in the development of hydromorphic Podzols are a major concern for the upper Amazon Basin because of the extent of the areas affected by such processes and the large amounts of organic carbon and associated metals exported to the rivers. The dynamics and chemical composition of ground and surface waters were studied along an Acrisol-Podzol sequence lying in an open depression of a plateau. Water levels were monitored along the sequence over a period of 2 years by means of piezometers. Water was sampled in zero-tension lysimeters for groundwater and for surface water in the drainage network of the depression. The pH and concentrations of organic carbon and major elements (Si, Fe and Al) were determined. The contrasted changes reported for concentrations of Si, organic carbon and metals (Fe, Al) mainly reflect the dynamics of the groundwater and the weathering conditions that prevail in the soils. Iron is released by the reductive dissolution of Fe oxides, mostly in the Bg Horizons of the upslope Acrisols. It moves laterally under the control of hydraulic gradients and migrates through the iron-depleted Podzols where it is exported to the river network. Aluminium is released from the dissolution of Al-bearing minerals (gibbsite and kaolinite) at the margin of the podzolic area but is immobilized as organo-Al complexes in Spodic Horizons. In downslope positions, the quick recharge of the groundwater and large release of organic compounds lead to acidification and a loss of metals (mainly Al), previously stored in the Podzols.
