Secondary Carbonate Accumulations Research Articles

Black soils in the southwest of the Brazilian Pantanal: Organic carbon and secondary carbonates accumulation in Phaeozems–Gleysol-Chernozem

The southwest of the Brazilian Pantanal contains areas formed by calcareous sediments, which give this hydromorphic environment special characteristics in the formation of soils such as Phaeozems, Chernozems and Gleysols. These soils have a dark surface horizon, enriched with organic matter, high natural fertility in the sorption complex and high clay activity. These soils are important because they store large amounts of organic carbon and can be used in carbon sequestration and greenhouse gases studies. However, despite their abundance in the Pantanal region and importance, these soils are few studied. Thus, our study aimed to characterize the morphology, physical, and chemical attributes of black soils in this region, identifying the main mechanisms of organic carbon and secondary carbonate accumulation. Three profiles located in the municipality of Corumbá-MS were studied, namely Phaeozem (profiles P1), Gleysol (profile P2) and Chernozem (profiles P3). In all profiles, high concentrations of Ca2+, Mg2+ and K+ elements were observed, mainly derived from the sediments of the Serra da Bodoquena and the Urucum-Amolar residual plateau, ion transport fluxes and secondary carbonate dissolution. The preservation of these elements and 2:1 clays is closely linked to the rainfall dynamics of the region, alternating between floods and droughts. The high 2:1 clays and exchangeable Ca2+ benefits the stabilization of organic carbon by means of organic–mineral interactions and promote the increase of humin content. In Phaeozem and Chernozem, the highest levels of secondary carbonates were observed at the top of the B horizons of these soils, where the pressure of CO2 is lower. Being a lowland area under the direct influence of flooding, the development of secondary carbonates is limited in the B horizons of the Gleysol, where access to the water table and root activity at depth increases the CO2 pressure and hinders the re-precipitation of carbonates in this soil, precipitating in the capillary bangs and in the upper zone (surface horizons).

Biogenic carbonates (queras) in loess-palaeosol sequences of the Ebro Basin and their potential use as a palaeoenvironmental proxy

Secondary carbonate accumulations are very common in arid and semi-arid soils but are often poorly described and classified. This is the case for queras that are observed in several loess-palaeosol sequences of the Ebro Basin. Micromorphologically, queras are complex pedogenic features basically consisting of infillings of calcified root cells in channels, surrounded by decarbonated hypocoatings. They apparently result from biologically mediated calcification/decalcification processes at a microscale. The aim of this study is to systematically characterize biocalcifications found in dated loess-palaeosol sequences, to determine the main factors of formation, and to discuss their possible use as a palaeoenvironmental proxy. Different queras show a similar number of biosparite layers (four to five) around a central channel, and a decarbonated hypocoating around the queras. This supports the hypothesis that queras originate from the calcification of root tips and are related to the acidification of surrounding soil for nutrient absorption. Under cathodoluminescence microscopy, biosparite has a different behaviour than non-biological calcite crystals: the latter appears reddish while biosparite remains black. The queras, with ages corresponding to Marine Isotope Stages 1–3, are younger than that of the loess where they are found in. The stable isotope values likely correspond to C3 plants, and the estimated temperatures of formation reflect a Mediterranean temperate climate. This suggests that the biocalcifications developed during short moist seasons amidst arid periods of the Quaternary.

Paleosol distribution and morphology along a late Cretaceous distributive fluvial system in the Bauru Basin, Brazil

Distributive Fluvial Systems (DFS) are fan-shaped landforms constituted by a radial system of channels that diverge downstream from an active apex, where the drainage emerges from the confinement valley. In such landforms, elevation, distance from fluvial channels, sedimentation rates, surface stability, and plant cover control weathering processes and soil development, but these features are obliterated within geological time. Thus, the micromorphological analysis of paleosols can be helpful for paleoenvironmental reconstruction of ancient DFS, improving the knowledge of soil genesis in these depositional landforms. Here, we describe macro and micromorphological features of twenty paleosols developed under arid to semiarid climates along the proximal to the medial zone of an Upper Cretaceous DFS in the Marília Formation, Bauru Basin, Brazil. Paleosols on the proximal zone typically showed features consistent with poor drainage, namely Bg, Btg and Bss horizons, and reddish Bt horizons in higher positions. Conversely, paleosols on the medial zone commonly showed reddish colours and pronounced secondary carbonate accumulation, consistent with a predominantly arid climate. Based on this distribution, we elaborated an evolution landscape model for the proximal and medial zone of the Bauru DFS, including allogenic and authigenic controls of soil development during the Campanian to the Maastrichtian epochs of southeastern Brazil.

Fate and migration of enhanced rock weathering products through soil horizons; implications of irrigation and percolation regimes

Terrestrial enhanced rock weathering (ERW) is reckoned as a robust method to contribute to stabilizing atmospheric carbon and combat global warming. The method is particularly a matter of interest in agricultural soil, offering a vast opportunity for the application of crushed silicate minerals and secondary carbonate accumulation and migration. Although the applicability of this practice is well acknowledged, its impact on the geochemical alteration of soil vertical profile, particularly deeper layers, is less discussed in the literature. Moreover, the effect of irrigation and percolation regimes, as influenced by ambient conditions, is also not well-reported and characterized. In the present study, we utilized a high amendment rate (50 t/ha) of wollastonite skarn, a fast-weathering silicate mineral, to uncover the alterations in topsoil and subsoil as well as effluent water over a through a soil column experiment over five months, under more controlled (indoor) and less controlled (outdoor) ambient and irrigation conditions. The results indicate more conspicuous modification of parameters in shallow layers of soil compared to deeper ones, explicitly in the rain-fed setup. Silicate amendment induced an increase of 6.53 and 2.85 tCO2/ha (in the form of pedogenic carbonate (PC)) over the profile of soil (0–60 cm) under periodic and rain-fed water regimes, respectively. The silicate treatment was also found to be effective toward rising pH and electrical conductivity of topsoil (0–15 and 15–30 cm layers) and leachate, and a measurably greater release of Ca2+ and Mg2+ in the column effluent. We estimate a carbon drawdown ratio (carbonate/bicarbonate) of ≈15:1 in this study, showing that PC formation is a more significant weathering indicator than leachate bicarbonate export in the shorter term for a fast-weathering mineral in pH-neutral soils and moderate irrigation regime. Such observations are valuable for developing carbon drawdown quantification methods suitable for a variety of agricultural lands and global regions.

Importance of substrate genesis for Mediterranean soil evolution – An example from a limestone hillslope in the Estremadura (W-Portugal)

Many land surfaces in the Mediterranean region are characterized by undulating to steep slopes. Nonetheless, geomorphological and soil-geographical research in the past has paid only little attention to such environments and soil-geographical knowledge is therefore largely based on investigation of rather flat landscapes. By studying a limestone hillslope in western Portugal, this study aims to recover information on soil substrate layering, assess the importance of substrate formation for Mediterranean soil genesis and present an allochthonous soil evolution model.The results provide clear evidence for stratified soil profiles showing lithological discontinuities. Natural and/or anthropogenic allochthonous substrate widely covers the autochthonous substrate and therefore decouples the in situ substrate from recent pedogenesis. Therefore, substrate formation and distribution is a major key for understanding soil evolution in Mediterranean hillslope environments, whereas existing autochthonous or aeolian allochthonous soil evolution concepts (A-B-C-models) do not provide plausible explanations. Based on pedogenetic models established mainly in the mid-latitudes and the tropics, our fully substrate-genetic, allochthonous soil evolution model states that the soil-geographical pattern and the soil evolutionary stage (pedogenic ageing) is regularly, ubiquitously and systematically determined by the horizontal and vertical substrate configuration. Substrate distribution is geologically and geomorphologically based and mainly takes place via aquatic processes along depressions and valleys during a reduction in the vegetation cover. Since Mediterranean hillslope environments are fragile landscape elements, progressive pedogenic aging is repeatedly interrupted by negative (erosion) or positive (coverage) regressive processes. Consequently, pedogenesis is restricted to relatively early-stage processes including decalcification, associated substrate reddening, the accumulation of secondary carbonates in lower profile sections and the formation of Ah horizons.

Late Pleistocene–Holocene pedogenesis and palaeoclimate in western Asia from palaeosols of the Central Iranian Plateau

The Late Pleistocene and Holocene in western Asia is characterized by frequent, millennial‐scale, high‐amplitude environmental climatic changes. However, little is known about palaeoclimate conditions on the arid Central Iranian Plateau and knowledge of palaeosols and past phases of pedogenesis in relation to climatic events is scarce. Nevertheless, these palaeosols contain important information on the Last Glacial–Interglacial cycle and Holocene climate and environmental changes in the region. Three representative pedons with eight argillic horizons from the interior of the Central Iranian Plateau, namely Isfahan, Jimabad and Bajestan are selected for micromorphological, mineralogical and submicroscopic analyses. The ages of these palaeosols are constrained using the optically stimulated luminescence (OSL) signal from quartz. Micromorphological observations show clay illuviation, carbonate leaching, accumulation of secondary carbonates, calcite depletion, and other characteristic pedogenic features. These characteristics, combined with the luminescence chronology, reveal the presence of well‐developed reddish‐brown palaeoargillic horizons (Btk/Btky) with intensive soil formation processes taking place during the Last Interglacial to Middle Holocene (~107–4.5 ka) in our study area. Pedogenic evidence from the palaeosols suggests steps of polygenetic formation in the argillic horizons in response to alternating wetter and drier phases during this period. Four distinct phases of pedogenesis resulting in Btk/Btky horizons are identified: (i) Marine Isotope Stage (MIS) 5, (ii) MIS 3, (iii) the Last Glacial–Interglacial Transition Holocene, and (iv) the Late Holocene.

Patterns of geochemical variability across weakly developed paleosol profiles and their role as regional stratigraphic markers (Upper Pleistocene, Po Plain)

Weakly developed paleosols from two distinct interfluve surfaces of Late Pleistocene age provide excellent keys to high-resolution stratigraphic correlation and may serve to trace large-scale genetic packages (systems tract equivalents) across the continental portion of the Po Basin. Twenty-four paleosol profiles from 17 sediment cores were identified and characterized for bulk-geochemical analysis. X-ray fluorescence data were used to trace the degree of weathering. Paleosols, 0.5–1.5 m thick, are pedogenically altered floodplain deposits, developed over time spans of a few thousand of years and mostly partitioned into A-Bk horizons. The most notable paleosol features are dark, organic-matter-rich and carbonate-free mineral surface horizons (A) that overlie bright calcic horizons (Bk) typified by the accumulation of secondary carbonates in the form of pedogenic nodules.Paleosol profiles exhibit a homogeneous geochemical signature that fingerprints a moderate degree of weathering, with little strike- and dip-oriented variability across the different study localities. Plots of Al-normalized calcification and base loss indices against depth reveal systematic increasing values from intensely altered A horizons to underlying Bk horizons. These trends reflect consistent patterns of Ca translocation from surface horizons deeper into the profile, with significant to almost complete Ca removal from A horizons through leaching and accumulation in Bk horizons. Selected trace element ratios (Ba/Sr, Rb/Sr), redox-sensitive trace elements and Zr contents display opposite, up-profile increasing trends that reflect Sr loss in A horizons, with selective Zr concentration in residual minerals.Vertical trends in element ratios are laterally extensive and consistent on a regional basis and represent key pedochemical/stratigraphic markers that can be traced over great distances (tens of kms) throughout the inland portion of the basin. Through quantitative assessment of the degree of weathering, geochemical profiling provides high potential for robust subsurface paleosol correlation that might not be captured by visual core descriptions alone.

Provenance, and environment context of pedogenic carbonates formation from MIS 3 to MIS 1 in the Teotihuacan Valley, Mexico

Pedogenic carbonates are considered important indicators of past climatic changes. Their formation is due to calcite accumulation through evaporation processes in arid or semi-arid regions. Over time, secondary carbonate accumulation results in the development of calcic and petrocalcic horizons in soil profiles. In this study, we conducted an analysis of pedogenic carbonates as records of paleoenvironmental characteristics in the Teotihuacan Valley, Basin of Mexico. Micromorphological, mineralogical, and geochemical characteristics of secondary carbonates from three paleosol profiles (Cerro Gordo 1, Cerro Gordo 2, and Maseca 1) were analyzed. Pedogenic carbonates were characterized by irregular and variable carbonate crystal sizes, inclusions of soil particles, and dark or light micrite and microsparite laminations. Micromorphology and scanning electron microscopy revealed weathered plagioclase minerals as a potential source of calcium for carbonate precipitation. The 87Sr/86Sr ratio of carbonate laminar crusts and nodules from the analyses pedons in the study area also indicated that rocks of the Transmexican Volcanic Belt were the principal source of Ca and Sr for carbonates, while contribution of a far-distance eolian input was minimal. The δ13C isotopic composition evidenced a mixture of C3 and C4 plants during the Pleistocene and a transition to a higher proportion of C4 vegetal cover during the Holocene. This agreed with an increase in modeled paleo-temperature from 10.9 °C to 13.7 °C based on 18O-temperature equations. Our results support those determined for the regional paleoenvironment during the Pleistocene, the Pleistocene-Holocene transition and Mid-Late Holocene.

Calcium carbonate accumulations in Technosols of Moscow city

Complex phenomena of the precipitation and accumulation of calcium carbonate in urban soils and sediments have been studied. They are linked to the interactions between the lithosphere, the biosphere, and the atmosphere. Calcium and its compounds are among the main elements determining soil’s morphological, physical, and chemical characteristics. This study was aimed at summarizing information about calcium carbonate concentrations in soils and finding evidence for the formation of carbonate micronodules by pedogenetic processes in Urbic Technosols under automorphic conditions. Moscow is located within the southern taiga belt, with a humid temperate climate and a percolative water regime. The city’s technogenic deposits contain significant amounts of carbonates due to inclusions of construction waste and additions of airborne dust. Contemporary humus-accumulative horizons of Urbic Technosols were found to contain carbonate accumulations (rounded or isomorphic nodules). Samples from such horizons were studied using a polarizing microscope (analysis of thin sections) and a scanning electron microscope with an energy-dispersive X-ray analyzer (element mapping to detect carbonate accumulations). Laboratory analyses of main chemical and physical soil properties were performed. The analyzed samples contained both primary (i.e., inherited from parent materials) and secondary (i.e., newly formed in soils) calcium carbonates in various forms. Inclusions of solidified mortar (carbonate building solutions) contained dolomite. Although the studied carbonates underwent recrystallization processes, they remained in soils for a long time. Fibrous Mg silicate films deposited at the surface of recrystallization areas were observed. The formation of carbonate micronodules at depths of 15–40 cm in slightly and moderately calcareous humus horizons was investigated. Newly formed calcite was distinguished by a homogeneous composition, a microsparitic size of crystals, and a compact packing within the groundmass. Newly formed calcite was observed within microzones that were free from carbonate inclusions with dissolution features. The dissolution of primary carbonates in soils under humid climate conditions triggers pedogenetic processes of the carbonate heritage redistribution and the mineral matrix transformation. Recrystallized carbonates are the main forms of secondary carbonate accumulations in automorphic Technosols. The presence of compact carbonate nodules composed of microsparitic calcite within the bulk of silicate material may be indicative of carbonate neoformation as a result of interactions between the dissolved CO2 from root respiration and the soil absorbing complex saturated by Ca from soil solution. This is confirmed by a number of studies on the carbonate isotopic composition in urban soils.

Carbonate Profile of Soils in the Baikal Region: Structure, Age, and Formation Conditions

The results of the study of the carbonate profiles of soils in the western (Cis-Baikal) and eastern (the Selenga middle mountains) Baikal region are presented. There is a similarity in their structure: numerous CaCO3 maxima in the soil profiles are typical, which is associated with the repeated redistribution of carbonates during different stages of pedogenesis. The carbonate profile of soils in the Baikal region is relatively ancient (the youngest accumulations date back to the Middle Holocene) and a rather conservative formation that does not undergo any noticeable rearrangements under modern climatic conditions. The accumulations of secondary carbonates are localized in the carbonate-accumulative horizons of the modern surface soils and buried Kargin (MIS-3) soils and Holocene soils. The exception is hypocoatings that are often found beyond the indicated horizons, which is associated with a more active redistribution of carbonates within the root system of vegetation. The solid-phase effect of carbonatization (carbonate neoformations) is observed in the study area mainly in the soils formed on calcareous rocks and products of their redeposition and does not depend on the type of soil and the nature of the growing vegetation. Based on the analysis of the composition of stable carbon and oxygen isotopes in secondary carbonate accumulations, it was found that carbonate precipitation in soils of the Cis-Baikal region occurs during the degassing of soil solutions in the course of freezing–thawing cycles, dynamic increase and decrease in the soil biological activity, and alternation of the soil moistening with snowmelt and rainwater with its subsequent freezing that can take place in spring and autumn seasons. Under these conditions, atmospheric CO2 has the main influence on the isotopic composition of carbon in pedogenic carbonates; the isotopic composition of oxygen is controlled by the fractionation of isotopes upon freezing of the soil solutions. Secondary carbonate accumulations in the Selenga middle mountains are formed during the soil drying as a result of active water consumption for plant transpiration, which is most pronounced in the first half of summer.

Suitability of World Reference Base for Soil Resources (WRB) to describe and classify chernozemic soils in Central Europe

Abstract Chernozemic soils are distinguished based on the presence of thick, black or very dark, rich in humus, well-structural and base-saturated topsoil horizon, and the accumulation of secondary carbonates within soil profile. In Central Europe these soils occur in variable forms, respectively to climate gradients, position in the landscape, moisture regime, land use, and erosion/accumulation intensity. “Typical” chernozems, correlated with Calcic or Haplic Chernozems, are similarly positioned at basic classification level in the national soil classifications in Poland, Slovakia and Hungary, and in WRB. Chernozemic soils at various stages of their transformation are placed in Chernozems, Phaeozems or Kastanozems, supplied with respective qualifiers, e.g. Cambic, Luvic, Salic/Protosalic, Sodic/Protosodic etc. Some primeval Chernozems thinned by erosion may still fulfil criteria of Chernozems, but commonly are shifted to Calcisols. Soils upbuilt (aggraded) with colluvial additions may also retain their original placement in Chernozems, getting supplementary qualifier Colluvic. “Hydromorphic” chernozemic soils, in many CE systems are placed as separate soil type (“czarne ziemie” or “čiernice”) at the same level with “typical” chernozems. Classification of these soils in WRB depends on the presence of chernic horizon, depth of secondary carbonate accumulation and depth of gleyic/stagnic properties, and may vary from Gleyic/Stagnic Chernozems/Phaeozems to Mollic Gleysols/Stagnosols. Although WRB classification differs from national classifications in the concepts and priorities of classification, it provides large opportunity to reflect the spatial variability and various stages of transformation/degradation of chernozemic soils in Central Europe.

First data on the age and formation conditions of secondary carbonate accumulations in upper pleistocene and holocene soils of Upper Angara region

The first data on the age of secondary carbonate pendants in the soils of the Upper Angara region are given. Based on the study of the conditions of occurrence, morphology, material and isotopic composition, three groups of carbonate kutans were identified. The direct 14C AMS dating of the coating’s microlayers allowed to determineintervals of their formation. Pendants of the first group were formed in the middle Holocene (3.6-3.3 kyr BP). The formation of coatings of the second and third groups took place in the second half of MIS-3 (24.1-23.3 and ~34-35 kyr BP, respectively). The paleoecological conditions reconstructed for the identified stages of the formation of carbonate pendants satisfactorily correlate with the climate changes in the region and the northern hemisphere as a whole, reflecting the influence of temperature and moisture fluctuations on the dynamics of soil formation processes. Comparison of the age of carbonate accumulations with the age of modern and buried soils shows that pedogenic carbonatecoatings in the soils of the Upper Angara region are a relict feature of previous stages of pedogenesis (MIS-3) and the first stages of modern soil formation, which began, apparently, in the middle Holocene. The close ratios of the composition of stable carbon and oxygen isotopes in mid-Holocene and Late Kargin (MIS-3) coatings suggest that there is a similarity of pedogenesis conditions in these time intervals, primarily due to the relatively low temperature of pedogenesis and the duration of the seasonally frozen of soils.

First Data on the Age and Formation Conditions of Secondary Carbonate Accumulations in Upper Pleistocene and Holocene Soils of Upper Angara Region

The first data on the age of carbonate cutans in soils of the Upper Angara Region are given. Three groups of them were identified on the basis of the conditions of their occurrence, morphology, and substance and isotopic composition. The direct 14C AMS-dating of microlayers of cutans enables us to determine the periods of their formation. Cutans of the first group were formed in the Middle Holocene Period (3600–3300 cal. yr BP). Neoformations of the second and third groups appeared in the second half of MIS-3 (24 100–23 300 and ~34 000–35 000 cal. yr BP, respectively). Paleoecological conditions reconstructed for the identified stages of formation of carbonate cutans correlate well with the trend of climatic changes in the region and in the Northern Hemisphere in general. They reflect the effect of temperature and moisture fluctuations on the dynamics of soil-forming processes. The comparison of the age of neoformations with the age of modern and buried soils shows that pedogenic carbonate cutans in soils of the Upper Angara Region are a relict feature of the previous epochs of pedogenesis (MIS-3) and of the first stages of modern soil formation, which apparently began in the Middle Holocene. The similar ratios between stable carbon and oxygen isotopes in the Middle Holocene and Late Kargin (MIS-3) cutans permit us to suggest that the pedogenic conditions in those periods were similar and were mainly determined by relatively low temperatures of pedogenesis and long-term seasonal soil freezing.

Carbonations and carbonate profile forming processes of rendzinas of the Podilski Tovtry

The peculiarities of content and profile distribution of carbonates in rendzinas and soil-forming rocks of the Podilski Tovtry are investigated. It has been determined that the predominant process of weathering of carbonate rocks is a chemical dissolution, in which carbonates are converted into bicarbonates and, in the case of washing water regime, are applied from the soil (the process of decarbonization) and mechanical grinding and destruction of the remaining carbonate inclusions in the process of soil cultivation. The dissolution of carbonate rocks causes accumulation in the soil profile of an insoluble residue, the intensity of which depends on the composition of carbonate rocks, the rate of filtration of aqueous solutions, their aggressiveness and the concentration of destructive substances. The most intensive such accumulation occurs in acidic medium, at a low rate of infiltration of solutions and at high concentrations of CO2. It was established that the highest proportion of CaCO3 is characterized by lithotamium limestone (up to 90–93 %), and the lowest – carbonate polygenetic loams (up to 35–40 %). The feature of the profile distribution of the content of carbonates in rendzinas is its gradual growth in the upper part of the soil profile and rapid in the middle and lower parts. It is determined that the rendzinas of the Podilski Tovtry carbonates are represented predominantly in the form of wreckage of initial soil-forming rocks of different sizes and shapes, as well as amorphous solid-phase crude and finely dispersed products of weathering in the form of powdery and powdery carbonate dusting. It is established that in dense crystallized lithotamium limestones of the main strand, the carbonate mass weakly passes moisture, and the main process of weathering occurs due to surface corrosion. The accumulation of secondary carbonates in the form of mycelium and veins is characteristic on the slopes of the Tovtry (mostly in brown rendzinas and pararendzinas), due to the vertical and lateral migration flows of the dissolved forms of CaCO3. Key words: rendzinas, Podilski Tovtry, carbonates, carbonate profile.

Карбонатные новообразования в почвах Байкальского региона: процессы формирования и значение для палеопочвенных исследований

Карбонатные новообразования в почвах Байкальского региона: процессы формирования и значение для палеопочвенных исследований

Classification and spatial distribution of soils in the foot and toe slopes of mountain Vukan, East-Central Serbia

This study describes and classifies the soils of the foot and toe slopes of the Vukan Mountain, Central Serbia, the contact point of two distinct geomorphological units, with a focus on their spatial distribution and their main soil-forming processes. The Vukan Mountain is formed of Jurassic limestones and dolomites, whereas the foot and toe slopes are of fluviatile-colluvial origin. A total of 42 soil profiles were examined. Soil profile locations were determined with respect to elevation differences, accounting for a set of six profiles for every 5-m elevation increase between 175 and 210ma.s.l. The area is characterized by the dominance of chernic and mollic topsoil horizons and the major part of the area is covered with Phaeozems. Five Reference Soil Groups were found in a very small area. Eleven soil profiles are Chernic Phaeozems, five are Cambic Phaeozems, and twelve are Rendzic Phaeozems. The central part of the study area is characterized by the accumulation of secondary carbonates and Chernozems were identified. The northern part of the study area is covered with Fluvisols, Calcisols, and Leptic Rendzic Phaeozems, whereas Chernic and Cambic Phaeozems and Eutric Cambisols cover the western part of the study area. The differences in the CaCO3 content in the gravels, the differences in the gravel content, and the different lateral and vertical distribution of CaCO3 are strong evidence of surface processes that occurred in the past. The presence of different geological layers and buried horizons suggests fluviatile processes. The spatial distribution of soils is related mainly to parent material occurrence, and colluvial and alluvial processes that occurred in the past. The soil map created in GIS has Reference Soil Group as central unit following Rule 1 for map legend creation, except in the case of Phaeozems, which are present as Phaeozems (Leptic) and Phaeozems (other) following Rule 5. This soil survey with approximately one soil profile per 4 ha has indicated considerable soil heterogeneity in the study area. Detailed surveys are therefore recommended for areas with pronounced heterogeneity of soil-forming factors.

Characterization of Some Calcareous Soils from Henan and Their Proposed Classification in Chinese Soil Taxonomy

Calcareous soils are those soils containing layers of carbonate accumulation formed by either secondary accumulation or inheritance of CaCO3 from calcareous parent materials. These soils are widely distributed in arid, semi-arid and even some humid climate environments. However, in the Chinese Soil Taxonomy (CST, 3rd version), the soils that contain large amounts of CaCO3 but do not meet requirements of Aridosols are classified as Hapli-Ustic Cambosols. This group also includes many non-calcareous soils and those soils strongly affected by secondary carbonate accumulation together with quite dissimilar soils in terms of their morphology and properties. This study was conducted to determine calcification patterns and calcic processes occurring in representative pedons of calcareous soils in northwestern Henan Province, China and to classify these soils in CST. A Calcic subgroup was proposed to add within the Hapli-Ustic Cambosols. A diagnostic key was also provided to separate this subgroup from the Typic subgroup. In this way the different calcification degrees of soils were better reflected in the classification, which should lead to more uniform interpretive groups for better soil management.

Szekunder karbonátok mennyisége és vertikális eloszlása tokaji talajszelvényekben

The forms and stocks of secondary carbonate accumulations and the distribution of secondary carbonate content were investigated in 20 soil profiles from Nagy-hegy, Tokaj. The secondary carbonate content varied to a great extent under different lithological conditions. The frequency of carbonate crusts coating the coarse fragments to a thickness of 1–7 mm was especially conspicuous. In selected profiles the amount of secondary carbonates was analysed separately for three carbonate pools: in the fine earth (<2 mm), in carbonate crusts and other concentrations, and in the skeletal part of the soils (dominantly dacite blocks and boulders). In one profile a calculation was made of the calcium carbonate stocks (in kg m−2) in the separate fractions of the fine earth, the skeletal fraction and the carbonate crusts and concentrations. The values obtained for the distinct soil horizons were then summed for the whole profile above the continuous hard rock. The loess deposits can be regarded as the primary source of calcium carbonate, but many types of secondary carbonate accumulations occurred in places where the loess deposits were completely eroded or the original surface of the soil was only preserved on terraces with retaining walls. The results suggest that the highest accumulation of calcium carbonate occurs in profiles where loess, redeposited loess or colluvial deposit covers weathered volcanic rocks (pyroxene dacite), resulting in lithological discontinuity. The carbonate crusts consisted of 55–96 % (m/m) CaCO3, and the coarse fraction (dacite boulders and blocks) also had a higher calcium carbonate content (5–10 % m/m) than the non-weathered pyroxene dacite. The calcium carbonate stocks in Calcic accumulation horizons proved to be 2.5 times higher than in the overlying soil horizons. The accumulation forms of carbonates in the soil profiles and the lack of loess deposits on the top of the soil profiles suggest that the calcium carbonate was accumulated in the transitional zone between the loess and the weathered volcanic rocks. This appears to have taken place under humid climatic conditions, unlike the recent climate, and can thus be regarded at least partially as the result of paleoecological processes.

Flux estimation of fugitive particulate matter emissions from loose Calcisols at construction sites

A major source of airborne pollution in arid and semi-arid environments (i.e. North Africa, Middle East, Central Asia, and Australia) is the fugitive particulate matter (fPM), which is a frequent product of wind erosion. However, accurate determination of fPM is an ongoing scientific challenge. The objective of this study is to examine fPM emissions from the loose Calcisols (i.e. soils with a substantial accumulation of secondary carbonates), owing to construction activities that can be frequently seen nowadays in arid urbanizing regions such as the Middle East. A two months field campaign was conducted at a construction site, at rest, within the city of Doha (Qatar) to measure number concentrations of PM over a size range of 0.25–32 μm using light scattering based monitoring stations. The fPM emission fluxes were calculated using the Fugitive Dust Model (FDM) in an iterative manner and were fitted to a power function, which expresses the wind velocity dependence. The power factors were estimated as 1.87, 1.65, 2.70 and 2.06 for the four different size classes of particles ≤2.5, 2.5–6, 6–10 and ≤10 μm, respectively. Fitted power function was considered acceptable given that adjusted R2 values varied from 0.13 for the smaller particles and up to 0.69 for the larger ones. These power factors are in the same range of those reported in the literature for similar sources. The outcome of this study is expected to contribute to the improvement of PM emission inventories by focusing on an overlooked but significant pollution source, especially in dry and arid regions, and often located very close to residential areas and sensitive population groups. Further campaigns are recommended to reduce the uncertainty and include more fPM sources (e.g. earthworks) and other types of soil.

Geochronology and Geomorphology of the Pioneer Archaeological Site, Upper Snake River Plain, Idaho, USA

Pioneer is an open‐air, stratified, multicomponent archaeological site located in the upper Snake River Plain of southeastern Idaho, USA. Block excavations provided an opportunity to contribute to the Late Quaternary geomorphic history of the Big Lost River drainage and provide geochronological context of archaeological components at the site. The stratigraphic sequence is interpreted as reflecting multiple depositional episodes and five soil‐formation periods beginning pre‐7200 cal. yr B.P. and lasting to the historic period. The stratigraphic sequence contains an archaeological component dated to ∼3800 cal. yr B.P. and several other components post‐800 cal. yr B.P. Major site formation processes include fluvial deposition and erosion, pedogenesis (accumulation of secondary carbonates), and bioturbation. Periods of increased deposition at Pioneer and elsewhere along the Big Lost River are inferred to have occurred between ∼8400–6500 cal. yr B.P. and ∼2700–400 cal. yr B.P., potentially related to cooler/wetter episodes of the mid‐to‐late Holocene, including increased precipitation during the Medieval Climatic Anomaly (post‐750 cal. yr B.P.). There is also evidence of a high‐energy erosional event at ∼3800 cal. yr B.P. indicating a large middle Holocene flood. Pioneer provides an example of the archaeological and paleoclimatic value of studying alluvial buried soil stratigraphic sequences in arid environments.