Pedological Maps Research Articles

Espectros Vis-NIR do Solo e Fuzzy K-Médias Aplicados na Delimitação de Unidades de Mapeamento de Solos em Topossequências

RESUMO O conhecimento dos solos é cada vez mais importante para que o uso dele seja realizado corretamente na agropecuária, no crescimento urbano, na conservação dos recursos naturais, entre outros. Entretanto, verifica-se carência de profissionais qualificados para a caracterização e os mapeamentos pedológicos, particularmente em escalas de maior detalhamento. Essa carência, aliada aos avanços das ferramentas computacionais e do sensoriamento remoto, promoveu o surgimento do Mapeamento Digital de Solos (MDS), que busca auxiliar e agilizar as atividades de levantamento pedológico. Assim, este trabalho objetivou desenvolver uma metodologia de delimitaçao de unidades de solos em topossequências por meio do comportamento espectral dos solos no comprimento de onda do Visível-Infravermelho Próximo (Vis-NIR). A metodologia espectral consistiu na obtenção das curvas espectrais dos solos por meio do espectrorradiômetro FieldSpecPro e da redução do número de informações espectrais por meio da análise de Componentes Principais, seguida de agrupamento das amostras mediante método fuzzy k-médias. Foram selecionadas cinco topossequências com pontos equidistantes de 30 m para caracterizar as classes de solos e amostragens. Foram descritas oito classes de solos distintas, que tiveram caracterização detalhada e classificação em perfis pedológicos. No restante dos pontos, a caracterização das classes de solos foi feita com base na classificação dos solos realizada nos perfis pedológicos, com coleta de amostras por meio de tradagens nas profundidades de 0,00-0,20 e 0,80-1,00 m, perfazendo o total de 162 amostras ao longo das cinco topossequências. As amostras foram analisadas pelas metodologias convencional e espectral, para que os resultados pudessem ser comparados e avaliados. Dessa forma, foram realizadas análises morfológicas, físicas (textura) e químicas nas amostras de solo. Das cinco topossequências estudadas, os resultados foram satisfatoriamente semelhantes; alguns solos não foram perfeitamente individualizados pela metodologia espectral, em razão da grande semelhança em seus comportamentos espectrais, como demonstrado pelo Latossolo Vermelho Férrico e Nitossolo Vermelho Férrico. A metodologia espectral foi capaz de diferenciar solos com resposta espectral distinta e estabelecer limites nas topossequências, apresentando grande potencial para ser implementada em levantamentos pedológicos.

Multiple Geotechnological Tools Applied to Digital Mapping of Tropical Soils

ABSTRACT In recent years, geotechnologies as remote and proximal sensing and attributes derived from digital terrain elevation models indicated to be very useful for the description of soil variability. However, these information sources are rarely used together. Therefore, a methodology for assessing and specialize soil classes using the information obtained from remote/proximal sensing, GIS and technical knowledge has been applied and evaluated. Two areas of study, in the State of São Paulo, Brazil, totaling approximately 28.000 ha were used for this work. First, in an area (area 1), conventional pedological mapping was done and from the soil classes found patterns were obtained with the following information: a) spectral information (forms of features and absorption intensity of spectral curves with 350 wavelengths -2,500 nm) of soil samples collected at specific points in the area (according to each soil type); b) obtaining equations for determining chemical and physical properties of the soil from the relationship between the results obtained in the laboratory by the conventional method, the levels of chemical and physical attributes with the spectral data; c) supervised classification of Landsat TM 5 images, in order to detect changes in the size of the soil particles (soil texture); d) relationship between classes relief soils and attributes. Subsequently, the obtained patterns were applied in area 2 obtain pedological classification of soils, but in GIS (ArcGIS). Finally, we developed a conventional pedological mapping in area 2 to which was compared with a digital map, ie the one obtained only with pre certain standards. The proposed methodology had a 79 % accuracy in the first categorical level of Soil Classification System, 60 % accuracy in the second category level and became less useful in the categorical level 3 (37 % accuracy).

Remote sensing for mapping soil moisture and drainage potential in semi-arid regions: Applications to the Campidano plain of Sardinia, Italy

The aim of this study is to investigate the potential of radar (ENVISAT ASAR and RADARSAT-2) and LANDSAT data to generate reliable soil moisture maps to support water management and agricultural practice in Mediterranean regions, particularly during dry seasons. The study is based on extensive field surveys conducted from 2005 to 2009 in the Campidano plain of Sardinia, Italy. A total of 12 small bare soil fields were sampled for moisture, surface roughness, and texture values. From field scale analysis with ENVISAT ASAR (C-band, VV polarized, descending mode, incidence angle from 15.0° to 31.4°), an empirical model for estimating bare soil moisture was established, with a coefficient of determination (R2) of 0.85. LANDSAT TM5 images were also used for soil moisture estimation using the TVX slope (temperature/vegetation index), and in this case the best linear relationship had an R2 of 0.81. A cross-validation on the two empirical models demonstrated the potential of C-band SAR data for estimation of surface moisture, with and R2 of 0.76 (bias +0.3% and RMSE 7%) for ENVISAT ASAR and 0.54 (bias +1.3% and RMSE 5%) for LANDSAT TM5. The two models developed at plot level were then applied over the Campidano plain and assessed via multitemporal and spatial analyses, in the latter case against soil permeability data from a pedological map of Sardinia. Encouraging estimated soil moisture (ESM) maps were obtained for the SAR-based model, whereas the LANDSAT-based model would require a better field data set for validation, including ground data collected on vegetated fields. ESM maps showed sensitivity to soil drainage qualities or drainage potential, which could be useful in irrigation management and other agricultural applications.

Modelling soil salinity across a gilgai landscape by inversion of EM38 and EM31 data

SummaryThe soil in arid and semi‐arid areas is often markedly saline, which can severely limit agricultural productivity. Increasingly, geophysical methods are being implemented to map the levels and areal extent of soil salinity. One of the most effective methods is electromagnetic (EM) induction with instruments designed to measure apparent soil electrical conductivity (ECa). This study describes the generation of electromagnetic conductivity images (EMCIs) by inverting ECa data obtained with the EM38 and EM31 devices along two closely‐spaced transects by the EM inversion approach in the EM4Soil package. The EM38 ECa data are shown to be a more effective predictor of soil ECe. Calibration equations based on calculated true electrical conductivity (σ) and measured electrical conductivity of a saturated soil‐paste extract (ECe) provide reliable estimates of ECa. The patterns of σ in a test of the method in soil developed over thick alluvium on a clay plain in central New South Wales, Australia, compare favourably with existing pedological mapping; the mounds and depressions of gilgai were strongly differentiated from the more sandy alluvial sediments that characterize prior stream channels. The overall approach is potentially useful for generating a single calibration equation that can be used to predict ECe at various depths in the soil. Improvements in EMCI modelling can also be sought by joint inversion of EM with other geophysical datasets.

Pedological mapping through integration of digital terrain models spectral sensing and photopedology

New tools for soil mapping are needed to increase speed and accuracy of pedological mapping processes. This study integrated various technologies to map soils of the Piracicaba region in São Paulo State, Brazil. Each technology was expected to provide different information to design a detailed map. We carried out field survey and soil sampling for laboratory analysis. Initially, we conducted field visits to obtain soil patterns of a reference site. We applied the acquired patterns to an validation site, based solely on information obtained from remote sensing and cartographic databases, namely LANDSAT 7/ETM, digital elevation models (DEM) and aerial photographs. We integrated the information from each product to generate the map of the validation site, which was validated by field inspection. Textural classification using satellite imaging ranged from 21-51% of accuracy. Band 5 in the sensor showed the best performance to discriminate between clayey and sandy soils. Aerial photographs provided the best information because, besides their own inherent characteristics, they operate on a larger scale and result in a map with up to 50 polygons, while DEM reached a maximum of 30 polygons. The digital mapping technology generated 45 mapping units. Finally, the mapping efficiently separated the Latosols from the other classes; however, in some cases there was confusion in the identification of Cambisols and litholic Neosols.

Relief-Rock-Soil relationship in the transition of Atlantic Plateau to Peripheral Depression, Sao Paulo, Brazil

This paper presents an atlas of physical geography at a detailed scale for an area located between two large morphostructural units: the Atlantic Plateau, a crystalline shield of rough landforms, and the Peripheral Depression, a transition unit from Plateau to the Parana Sedimentary Basin, whose smooth landforms are generally sculpted over sedimentary terrain. The transition between these two land systems creates contrasting landforms as a function of bedrock structure and soil type. Smooth landforms underlain by sedimentary rocks and reddish clayey soils alternate with small hills with abrupt slopes sustained by igneous or metamorphic rocks. These soils, developed from weathering of siltstones can rapidly change to brownish and pale colors indicating leaching and weathering of stratified sandstones or massive structured quartzites. A geomorphopedological classification at 1:10,000 scale was performed initially by delimiting units according to landforms. Secondly, other themes were added by combining them with different types of rocks and soils. The geomorphological map was produced by using thematic maps including a topographic base map, hypsometric map, slope map and morphological map. Also the geological and pedological maps were created based on field data collection, morphological analysis of soil profiles and physical, chemical and mineralogical laboratory analysis. Finally, the geomorphopedological units were defined using all the mapped data. Each of these units has peculiar features concerning developed or undeveloped soil formation, with mineralogy and structure very often linked to underlying rock. The landform shape is either controlled by geologic structure or originated from weathering processes that make the relief flatter.

SOLOS COESOS COMO FATOR DE RESISTÊNCIA À AGRICULTURA MODERNA NO OESTE BAIANO: UMA ABORDAGEM ESCALAR

This paper aims to discuss how natural factors, in this case the soil, even with the technology available nowadays,can be a resistance factor to the insertion of new areas to the process of agriculture modernization. To meetthis purpose, it is necessary to address the pedological maps scale appropriateness in Brazil and the possibilityof masking, depending on the peculiarities or pedological anomalies scale. For this discussion, the space usedwill be an experimental farm, located in the west of Bahia State, that presented problems with the eucalyptusplantation, due to the presence of the Cohesive soil. This type of soil is characterized for having an extremelycompact layer, with high consistence degree, when dry, and friability, when it is humid. This characteristic canmake it more difficult for root development and cause problems of soil aeration. So, it is expected that this papercan contribute to the discussion on actual soil mappings in Brazil and maps approach scale, considering that thelatter is directly related to the intention and intervention in geographic space.

Relações pedomorfogeológicas e distribuição de pedoformas na estação ecológica de águas emendadas, Distrito Federal

O Distrito Federal (DF) apresenta um modelo de distribuição de solos na paisagem condicionado pela compartimentação geomorfológica e substrato geológico. A perfeita compreensão das pedoformas auxilia o levantamento e mapeamento de detalhe ou semidetalhe dos solos de uma região. O mapeamento pedológico disponível do DF, realizado em 1978, em escala 1:100.000, ainda é a principal fonte de informações pedológicas do DF; no entanto, muitas vezes não atende aos diversos estudos pedológicos, em razão da escala reduzida. Assim, o objetivo deste trabalho foi estudar as relações solos-paisagem em uma topossequência na Estação Ecológica de Águas Emendadas - ESECAE, considerada representativa das relações entre feições do relevo, material de origem e classes de solos, em áreas com exposição das três unidades geomorfológicas definidas no Distrito Federal, incluindo as Chapadas Elevadas, bem como elaborar um mapa de pedoformas da área estudada, utilizando técnicas de geoprocessamento. Realizou-se um estudo da distribuição de solos na paisagem, por meio de avaliação das relações entre pedologia, geomorfologia e geologia. Para o desenvolvimento do trabalho, utilizaram-se os mapas geológicos e geomorfológicos disponíveis da ESECAE, além de geração do Modelo Digital do Terreno (MDT) e mapas de unidades geomorfológicas, de classes de declividade e de distribuição de geoformas. Por meio de dados da literatura e atividades de campo, com a caracterização dos solos nos perfis representativos ao longo da topossequência em estudo, estabeleceu-se o modelo de relação pedomorfogeológica da região, que permitiu estabelecer as relações entre os solos e as formas da paisagem e a elaboração do mapa de pedoformas da Estação Ecológica de Águas Emendadas. O mapa de pedoformas gerado fornece dados para atividades de levantamento e mapeamento pedológico de detalhe e semidetalhe em áreas com exposição das unidades geomorfológicas de ocorrência no Distrito Federal.

Simulation of soil types in Teramo province (Central Italy) with terrain parameters and remote sensing data

Soil surveys are an essential source of information for land management although a limited budget often reduces the amount of data available. Even if the dataset is limited, geostatistics can provide a valid estimation tool through a weighted moving average interpolation (kriging). Often, however, the spatial variability of soil properties appears smoothed and short range variability is underestimated by this kind of interpolation technique. A more realistic distribution of a given variable on the territory can be obtained through models based on stochastic simulation. The study area was located in Abruzzo region, Central Italy, in the Soil Region 61.3 as defined by the European Soil Bureau, and includes an economically relevant viticulture district (Controguerra “DOCG area of Colline Teramane”). Relationships between soil type distribution and terrain attributes – slope, incoming solar radiation, NDVI, TWI, etc. – were established, and the most significant were used in a multinomial logistic regression to generate simulated maps. These maps, derived from a set of measured point data, auxiliary information from a Digital Terrain Model and Landsat images, were compared with the soil subsystem map 1:250,000, realized by ARSSA. The comparison indicated that the simulated distribution of the soil classes is consistent with the pedological map and fits better with the local morphology.

Scaling-up leaf monoterpene emissions from a water limited Quercus ilex woodland

Mediterranean ecosystems are large emitters of biogenic volatile organic compounds (BVOC), and recent studies illustrate how water stress can decrease these emissions even during hot summer. We present here a spatially explicit modelling experiment of BVOC emissions in a water-limited Mediterranean Region in Southern France dominated by Quercus ilex forests. Emission rates were estimated daily using a leaf-level emission model with appropriate up-scaling procedures. The model was based on Guenther’s empirical equations, where we inserted effects for water limitation and seasonality observed from field measurements. Up-scaling from leaves to canopy was performed using Sellers’ theory. For each grid cell, climate variables were interpolated daily from meteorological stations. Incoming solar radiation was measured at one site and extrapolated for the all region based on slope and aspect. Soil properties were derived from pedological maps as well as a digital elevation model , while soil water content was evaluated daily using a bucket-type model. We estimated monoterpene emissions from Q. ilex woodlands to be 16 kt yr −1 (on average), with most emissions occurring in the summer. When including the water-limitation module, yearly emissions were 50% of the initial estimates, with a significant decrease in the number of days with BVOC high emission peaks. This result highlights the importance of water control on determining air pollution peaks in Mediterranean areas and the need for scaling procedure in this area with its large range of strong emitter species. ► Guenther’s algorithm was improved in order to include water-limitation effect on MT emissions. ► Model improves were based on field measurements. ► Considering water limitation in model decreased by two regional MT simulations. ► Yearly MT emission rate depended on drought period (precocious versus late). ► Considering water limitation decreased the number of days with high emission peaks.

Late pleistocene evolution of the Venetian–Friulian Plain

In the last decade, large geological, geomorphological and pedological mapping projects have been investigating the Venetian–Friulian Plain, strongly improving the available information about late Pleistocene sedimentary processes. This paper presents an overview of the evolution of the alluvial and costal plain since the end of middle Pleistocene to the Lateglacial. This was mainly possible through detailed field surveys and 20 stratigraphic cores of 50–270 m of depth. A strong relation between alluvial aggrading phases and glacial periods (final part of MIS 6 and Last Glacial Maximum) is evidenced, whereas during the last interglacial the sedimentation mainly occurred in the coastal sectors. During the Tyrrhenian transgression (MIS 5e) the lagoons reached a more landward position than the present. The deposits of middle Wurm are represented by thin alluvial sequences and an important depositional hiatus lasted tens of thousand of years ended around 35–30,000 years cal bp. The LGM is characterized by a strong phase of deposition until 20,000 years cal bp, then the sedimentary rate lowered and in the Friulian Plain led to apical incision of alluvial systems. Since Lateglacial an important erosive phase affected the whole plain and brought to the formation of deep and wide incision up to the present coast.

Integrating pedological and geophysical methods to enhance the informative value of an archaeological prospection – The example of a Roman villa rustica near Regensburg, Germany

Geophysical prospection techniques are widely used to visualize the buried past. Various methods such as magnetometry, electric resistance mapping and electric resistivity tomography and ground penetrating radar yield different results. The use of all three techniques in combination with aerial photography interpretation and pedological mapping is highly effective, but it requires a multi-layer approach. This paper presents such a multi-layer approach carried out at a site with buried remnants of a Roman villa rustica in southern Germany. The integration of the various results into a geographical information system leads to a geocodation of all outcomes and a final archaeological interpretation. Several buildings in different states of preservation, different kinds of ground floors both with and without hypocausts, perimeter walls and kilns could all be detected. The soil mapping results helped in the geophysical interpretation by outsourcing soil erosion and accumulation areas. It is shown that none of the employed methods could have supplied all the compiled information on their own, and the strengths and weaknesses of each method is discussed in order to point out the implications for archaeologists.

Mass movement mapping for geomorphological understanding and sustainable development: Tigray, Ethiopia

Mass movement topography characterises the escarpments and piedmont zones of the tabular ridges in the western part of the Mekelle outlier, Tigray, Ethiopia. Several types of mass movements can be distinguished. The first type is rockfall produced by 357 km rocky escarpments and cliffs during the rainy season. In the study area, every current kilometer of Amba Aradam sandstone cliff annually produces 3.7 m 3 of rock fragments. However, this is an under-estimation of the actual cliff and escarpment evolution, which is also characterised by debris slides and small rock slides. In the debris flow class, three dormant flow types are recognised. The first type comprises preferential or undifferentiated mobilisations of the so-called plateau layers, the whitish sandy-clayey lacustrine deposits and the lower and upper basalts, and more especially, the swelling clays, derived from the basalts. These debris flows start on the nearly horizontal Amba Aradam Sandstone tabular extensions, jump over cliff recessions or even spurs, and go very far into the valley. In some instances parts of Amba Aradam sandstone and Antalo limestone cliffs are transported. Secondly, some debris flows take their origin in the Antalo limestone supersequence. It concerns deeply weathered layers resting upon aquicludes/aquitards. Finally, gigantic debris flows and rock slides occur around dolerite dyke ridges. About 20% of the total surface of the study area is occupied by landslide topography. Most of the landslides affect the steep edges of the table mountains or the dykes/sills. Mapping and listing of active and dormant mass movements increases knowledge in three domains which are crucial for sustainable development of the study area. The first one is geomorphological risk assessment. The distribution map of active rockfall and dormant landslides shows the areas where potential risks are located. Land use changes which improve the water infiltration capacity of dormant landslides, should be followed up. Secondly, the impact of global climate change on these risk areas can be assessed. The second domain is the water sector, which needs attention in the study area and in many parts of Africa. Landslides mobilised by hydrostatic pressures are related to the occurrence of aquicludes and aquifers. In the study area, landslide mapping led to the location of three aquitards, not described before. The third domain is the pedological mapping. In the study area, soil distribution is very well explained by the morphology and extension of dormant landslides. Finally, mapping of dormant landslides stimulates the academic debate on the geomorphological significance of mass movements in hillslope retreat in tropical areas.

Engineering geological mapping of Dar es Salaam city, Tanzania

Engineering geological mapping of Dar es Salaam city in Tanzania has been carried out using desk studies supplemented by field reconnaissance as well as limited laboratory tests. Desk studies involved interpretation of medium to large-scale topographical maps, Landsat imagery and sequential aerial photographs from 1953-1990. These studies also evaluated small to medium scale geological, pedological maps together with ground water data from 50 boreholes. Two basic maps were prepared, namely, geomorphological and geological map depicts the spatial extent of the Neogene geological formations. Three distinct sandstone terraces could be distinguished in Dar es Salaam region at 0-15 m and 30 – 40 m above sea level. The terraces comprised sandstones fringed by coral reefs and were backed on their west by uplifted weathered clayey sandstones. Three synoptic construction maps were also prepared:- hazard, resources and land use maps. The hazard map classifies the terrain according to slope steepness, delineates areas susceptible to soil erosion, beach erosion, landslides, flooding, as well as expansive, karstic and saline grounds. The resources map delineates areas with respect to soil fertility as well as the occurrence of sand and gravel, limestone, kaolin, brick clays, heavy minerals and ground water deposits. With respect to light construction of foundations, the middle terrace appeared to be the most suitable in comparison to other terrains. Tanz. J. Sci. Vol. 28(2) 2002: 83-96

Use of pedological maps in the identification of sensitivity of soils to acidic deposition: application to Brazilian soils

The pedogeochemical maps present the spatial distribution of soils according to crystalochemical parameters (clay fraction) and physic-chemical aspects of the sorting complex (CEC and BS). These maps are adequate tool for environmental studies and particularly, for the analysis of the terrestrial ecosystem sensibility to acidic deposition. The pedogeochemical maps of the Brazilian soils, elaborated using FAO SoilWorld Map, allowed establishing the soil distribution according to 5 classes of vulnerability to acidic deposition, as defined by Stockholm Environmental Institute (SEI). From these maps, it is observed that about 50% of the Brazilian soils are high vulnerable to acidic deposition and can be included within the most sensitive class. This group is formed by well-developed and mature soils, constituted by clay minerals of kaolinite type associated with variable amount of gibbsite. About 8% of the soils can be considered as the least sensitive class. They correspond to Topomorphic Vertisols (Vertissolo, Embrapa 1999), Planosols (Planossolo, Embrapa 1999) and saline soils. Finally, the remaining soils represent the balanced media that dominate the northeastern semiarid zones and the south and northeastern subtropical zones.

Impacts of Human Activity on Landscapes in Central Brazil: a Case Study in the Araguari Watershed

This paper outlines the main geomorphological characteristics of the Araguari River Basin and describes the human‐induced changes to the landscapes. This region, naturally occupied by savannas, has been strongly altered by human activities over the previous 40 years. Summarised information is derived from geomorphological, geological and pedological maps, supported by field work. The paper is divided into two main parts. The first shows the natural arrangement of the landscapes in the hydrographic basin, demonstrating the relationships between structural and geomorphic units. Information about superficial materials and current processes and some observations on the evolution of these landforms are presented here. The second part describes the changes in the basin due to anthropic activities, considering types of erosion, channel changes and urban problems. These activities are divided between rural and urban areas, showing the differences between the operations of these sensitive systems. The paper also notes the main research in progress in this basin, presents some partial results and comments on future perspectives.

Relações solo-superfície geomórfica e evolução da paisagem em uma área do Planalto Central Brasileiro

Com base em levantamento pedológico de reconhecimento de alta intensidade, foram investigadas relações pedogeomorfológicas em uma área do Planalto Central Brasileiro, com vistas à predição de atributos e distribuição dos solos em áreas vizinhas carentes de mapas pedológicos. Três superfícies geomórficas, com distintos padrões de espacialização de solos, foram identificadas. Na mais elevada, a distribuição dos solos é estreitamente relacionada à variação do regime hídrico ao longo das encostas. Ocorrem Latossolo Vermelho (LV), Latossolo Vermelho-Amarelo (LVA), Latossolo Amarelo (LA), Latossolo Amarelo plíntico, Latossolo Amarelo petroplíntico (concrecionário) e Plintossolo Háplico, todos muito argilosos, com teores de Fe2O3 e TiO2 relativamente homogêneos e índices Ki e Kr indicativos de mineralogia oxídica. Na segunda superfície, os solos apresentam maior variação quanto à textura e teores de Fe e Ti. Predominam LV e LV acriférrico, além de LVA e LA. Nos limites com as chapadas, observa-se a ocorrência de LVA e LA acriférricos endopetroplínticos. Na terceira superfície, que disseca as anteriores, predominam solos menos intemperizados, com atributos muito variáveis, como Cambissolo Háplico, Argissolos Vermelho e Vermelho-Amarelo, Nitossolo Vermelho eutroférrico, Neossolo Litólico e Neossolo Flúvico. O trabalho inclui a proposição de um modelo de evolução para a paisagem regional.

Use of Soil Data for the Description of Agrarian Landscapes

The activities for post-processing (unification, harmonization) and integrated use of the "Medium Scaled Agricultural Soil Map" (MMK) of the former GDR implemented by BGR (Federal Institute for Geosciences and National Resources) are presented in an overview. From these works the present investigations are described for determination of the pedological map units heterogeneity of the "Soil Map of the Federal Republic of Germany 1:1,000,000" (BÜK 1000) and their effects on the field capacity. Many differences between BÜK 1000 and MMK, which result from the different nomenclatures and content data structures, require a gradual data preparation. The pedological heterogeneity of a BÜK 1000 unit, analysed as example, is shown by comparison with the corresponding MMK data in view to soil texture and field capacity and can be evaluated. In methodical regard hints result to a necessary critical examination of used tables of classification.

Environmental tracer transport ( 3H and SF 6) in the saturated and unsaturated zones and its use in nitrate pollution management

An important quantity in groundwater protection is the residence time of water in an aquifer. It relates to both the travel time of a pollutant to arrive at a well and the time span required for self-purification of a polluted aquifer after removal of pollutant inputs. Time scales for aquifers can be gained from artificial tracer experiments or from environmental tracer data, the latter offering the only realistic alternative if time scales of years or decades have to be taken into account. Different tracers show different time scales due to their different transport mechanisms especially in the unsaturated zone. While solute tracers are moved advectively with the seepage water, gas tracers pass the unsaturated zone diffusively through the air phase. Depending on the properties of the unsaturated zone (hydraulic properties, thickness) this difference in behavior can be used to separate the subsurface transport process into the unsaturated and the saturated parts. In a field study in Germany, SF 6 and 3H were used as environmental tracers. Both have a relatively well-known input function. Interpretation of data from observation wells by a box model approach led to spatially and temporally varying residence times. This was an indication that the influence of the unsaturated zone could not be neglected. While the gas tracer SF 6 shows only residence times in the saturated zone, the tracer 3H reflects the whole travel time of water including both the unsaturated and saturated zones. Using a one-dimensional plug-flow model for the unsaturated zone combined with a detailed two-dimensional flow and transport model for the saturated zone leads to a holistic and consistent interpretation of the measured tracer concentrations. The observed pattern of old water under thick loess cover and younger water under areas where the fractured basalt aquifer crops out is reproduced after adjusting only two parameters: the effective porosity of the saturated aquifer and the product of field capacity and thickness of the unsaturated zone. While the effective porosity of the saturated zone is adjusted by means of the SF 6 data, the field capacity of the loess layer is adjusted by means of the 3H observations. The thickness of the unsaturated zone is deduced from geological and pedological maps. All flow data are obtained from a calibrated flow model, which is based on geological data, observed heads and pumping tests only. The transport model for the saturated zone was calibrated by fitting the porosity by means of gaseous tracer concentrations (SF 6). The combined saturated–unsaturated zone model was then calibrated by fitting the field capacity of the unsaturated zone by means of 3H concentrations. With this model it was possible to verify the observed NO 3 concentrations at the drinking water wells and to develop predictions for their future development under various scenarios of fertilizer input reduction in specific areas.

Analyse de cartes pédologiques pour identifier le rôle du régime tectonique sur la répartition régionale de la perméabilité des altérites

Soil maps analysis to identify the role of the tectonic regime on saprolite permeability regional distribution. For applied geology, e.g., geotechnics or hydrogeology, it is of prime interest to know the spatial distribution of the saprolite permeability. This study focuses on the role of the tectonic regime on saprolite permeability regional distribution. Comparison of data concerning the uplift regime and soil organisation data from several pedological maps of the Armorican Massif (France) showed that blocks in relative uplift were characterized by a low proportion of hydromorphic soils, whereas a higher proportion marked blocks in relative downlift. Such differences can be related to the denudation regime, which affects the saprolite permeability.