Derek C. Bain

The podzolization process. A review.

Abstract This paper reviews the major mechanisms proposed to explain podzolization. These include the production of organic acids that form soluble complexes with aluminium/iron thereby enhancing weathering, followed by illuviation by precipitation/adsorption processes occurring at greater depth. Precipitation of aluminium and iron is explained by decreasing solubility of increasingly metal-rich complexes, or by microbial degradation of the organic ligand. We also discuss proposed role of inorganic hydroxy-aluminium–silicate sols in podzolization. The paper is introductory to a multidisciplinary study of podzolization performed in the Nordic Countries presented in this volume.

Advances in understanding the podzolization process resulting from a multidisciplinary study of three coniferous forest soils in the Nordic Countries

Advances in understanding the podzolisation process resulting from a multidisciplinary study at three coniferous forest soils in the Nordic countries

SUMMARY OF RECOMMENDATIONS OF NOMENCLATURE COMMITTEES RELEVANT TO CLAY MINERALOGY: REPORT OF THE ASSOCIATION INTERNATIONALE POUR L'ETUDE DES ARGILES (AIPEA) NOMENCLATURE COMMITTEE FOR 2006

Brindley et al. (1951) reported the earliest efforts to obtain international collaboration on nomenclature and classification of clay minerals, initiated at the International Soil Congress in Amsterdam in 1950. Since then, national clay groups were formed, and they proposed various changes in nomenclature at group meetings of the International Clay Conferences. Most of the national clay groups have representation on the Nomenclature Committee of the Association Internationale pour l’Etude des Argiles (AIPEA, International Association for the Study of Clays), which was established in 1966. The precursor committee to the AIPEA Nomenclature Committee was the Nomenclature Subcommittee of the Comite International pour l’Etude des Argiles (CIPEA, International Committee for the Study of Clays). The AIPEA Nomenclature Committee has worked closely with other international groups, including the Commission on New Minerals and Mineral Names (CNMMN) of the International Mineralogical Association (IMA), which is responsible for the formal recognition of new minerals and mineral names, and the International Union of Crystallography (IUCr), which considered extensions to the nomenclature of disordered, modulated and polytype structures (Guinier et al. , 1984) published earlier by a joint committee with the IMA (Bailey, 1977). In contrast to the other national clay groups, however, The Clay Minerals Society (CMS) Nomenclature Committee, which was established in 1963 at the same time as the CMS and predates the AIPEA Nomenclature Committee, remains in existence and occasionally produces recommendations. The precursor to this committee was the Nomenclature SubCommittee, which was organized in 1961 by the (US) National Research Council. The Chair of the AIPEA Nomenclature Committee is a standing member of the CMS Nomenclature Committee so that the committees are in close contact. The purpose of the AIPEA Nomenclature Committee has been to make general and specific recommendations concerning: (1) definitions of mineralogical and crystallographic clay-related terms; (2) classification and terminology …

REPORT OF THE ASSOCIATION INTERNATIONALE POUR L’ÉTUDE DES ARGILES (AIPEA) NOMENCLATURE COMMITTEE FOR 2001: ORDER, DISORDER AND CRYSTALLINITY IN PHYLLOSILICATES AND THE USE OF THE “CRYSTALLINITY INDEX”

The purpose of this report is to describe the appropriate use of indices relating to crystallinity, such as the ‘crystallinity index’, the ‘Hinckley index’, the ‘Kubler index’, and the ‘Arkai index’. A ‘crystalline’ solid is defined as a solid consisting of atoms, ions or molecules packed together in a periodic arrangement. A ‘crystallinity index’ is purported to be a measure of crystallinity, although there is uncertainty about what this means (see below). This report discusses briefly the nature of order, disorder and crystallinity in phyllo-silicates and discusses why the use of a ‘crystallinity index’ should be avoided. If possible, it is suggested that indices be referred to using the name of the author who originally described the parameter, e.g. ‘Hinckley index’ or ‘Kubler index’, or in honor of a researcher who investigated the importance of the parameter extensively, e.g. ‘Arkai index’. In contrast to a crystalline solid, an ‘amorphous’ solid is one in which the constituent components are arranged randomly. However, many variations occur between the two extremes of crystalline vs. amorphous. For example, one type of amorphous material might consist simply of atoms showing no order and no periodicity. Alternatively, another amorphous material may consist of atoms arranged, for example, as groups of tetrahedra ( i.e. limited order) with each group displaced or rotated ( e.g. without periodicity) relative to another. Thus, this latter material is nearly entirely amorphous, but differs from the first. Likewise, disturbance of order and periodicity may occur in crystalline materials. The terms ‘order’ and ‘disorder’ refer to the collective nature or degree of such disturbances. Although seemingly simple notions, ‘crystalline’ and ‘amorphous’ are complex concepts. Crystalline substances may show a periodic internal structure based on direction. For example, two-dimensional periodicity is common in phyllosilicates where two adjacent sheets or layers must mesh. For example, in serpentine, …

Podzolisation mechanisms and the synthesis of imogolite in northern Scandinavia

Abstract The nature of the short-range ordered Al and Fe minerals of the spodic B horizons of northern Scandinavia was studied by selective dissolution, transmission electron microscopy, infrared absorption and sulphate adsorption experiments. Imogolite-type materials (proto-imogolite allophane and well-developed imogolite) were the predominant oxalate-extractable Al minerals. Minor amounts of gibbsite and kaolinite were also found. The Fe oxides were less abundant and relatively well crystallized. Imogolite-type materials were the predominant source of positive charge, as evidenced by the amount of sulphate adsorbed. The Fe:AI ratio of the pyrophosphate extracts was positively correlated with the ratio of pyrophosphate-C to oxalate-extractable Al—this observation provides field evidence that imogolite-type materials were particularly unstable in the presence of organic substances. It is hypothesized that most accumulated Al and Fe originated from the congruent dissolution of primary minerals followed by the downward migration and degradation of metal-organic complexes, but incongruent weathering within the B horizon might have made additional contributions to the precipitation of the short-range ordered minerals. Historical climatic change might, to some extent, explain why metal-organic complexes were almost absent in many B horizons.

Variations in weathering processes and rates with time in a chronosequence of soils from Glen Feshie, Scotland

Chemical and mineralogical characteristics have been determined for a chronosequence of six soil profiles ranging in age from 80–13,000 years BP developed on river terraces in the western Cairngorms of Scotland. The C horizons are similar chemically and mineralogically, and the soils have similar pedogenetic histories. Exchangeable Ca and Mg decrease with time and base saturation decreases exponentially from 24.6% in the Ah horizon of the youngest profile to 2.8% in the comparable horizon of the 10,000 year old profile according to the chronofunction y=3.372+22.612 exp(−0.0007365t). Long-term weathering rates of base cations, calculated from the loss of these cations relative to Zr, appear to decrease exponentially with time but this may be due to the method of calculation. The magnitude of loss of base cations decreases in the sequence Na>K>Mg>Ca but when the relative mobilities of these elements are considered, the loss is in the order Mg>Na>Ca>K; this reflects the dissolution of chlorite and loss of Mg, and the more rapid weathering of plagioclase feldspar and loss of Na and Ca (particularly in the coarse sand fraction) than K-feldspar. The clay fractions, although <2% of all horizons, also show distinct patterns with age in that chlorite and mica are less abundant in older soils and vermiculite is more abundant, the latter phase often having hydroxyaluminium polymers in the interlayer region. The chemical and mineralogical trends in the soil sequence are closely associated and are induced by pedogenic weathering.

Composition of some smectites and diagenetic illitic clays and implications for their origin

Chemical analysis by X-ray fluorescence (XRF) and calculated structural formulae of clay-size fractions of smectites from Cretaceous bentonites and illitic clays from Cretaceous, Devonian, and Ordovician bentonites and Jurassic and Permian sandstones indicate the nature and extent of various types of ionic substitution. The determination of tetrahedral (Al, Si) and octahedral (Al, Mg, Fe) composition shows the variable chemistry of these materials. Structural formulae of the illitic clays show that they have tetrahedral charges between 0.4 and 0.8 per half unit cell, and can be divided into phengitic types having octahedral charges of 0.2-0.4 and muscovitic types having octahedral charges <0.2. Evaluation of the formulae in the light of X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) data shows that the occupancy of non-exchangeable interlayer sites (predominantly K) varies from 47% to 90% of that of ideal muscovite. In some minerals as much as 20% of these sites is occupied by ammonium ions (determined independently). The amount of surface silicate charge balanced by non-exchangeable cations versus that balanced by exchangeable cations has been examined in conjunction with TEM data and suggests that in most samples the charges are about equal. The octahedral composition of smectites in Cretaceous bentonites precludes their having served as transformation precursors for most of the Cretaceous illitic bentonites. The results suggest that these illitic clays originated by neoformation.

Effects of Acidification and its Mitigation with Lime and Wood Ash on Forest Soil Processes: A Review

Anthropogenic acid deposition causes forest soil acidification and perturbation of the soil forming processes. The impact of soil acidification on tree growth is discussed in view of the role of mycorrhizal fungi in weathering and nutrient uptake. A review has been carried out of experiments involving treatments of forest soil by lime and wood ash, where soil properties and soil solution composition have been investigated. Results from these experiments in Europe and North America are summarized. In general, the content of C in the mor layer decreased as a result of treatment due to higher microbial activity and soil respiration as well as increased leakage of DOC. In addition, the content of N in the mor layer, in general, decreased after treatment and there are occasional peaks of high NO3concentrations in soil solution. In nearly all reviewed investigations the pH of the deep mineral soil solution decreased and Al, SO4and NO3concentrations increased after treatment. These effects are probably due to the high ionic strength and increased microbial activity as a consequence of the treatments. In the soil, pH, CEC and base saturation increased in the upper horizons, but decreases in the upper mineral soil are also reported. In general, there was no increase in tree growth as a result of these treatments. The positive effects of the treatments on soil processes and tree growth are therefore questionable. In view of these conclusions, an investigation was carried out on the soil and soil solution chemistry and the role of mycorrhizal fungi in a spruce stand treated with two doses of lime and another treated with lime/ash in southern Sweden. The results of this investigation is reported in this volume.

Report of the Association Internationale pour l’Etude des Argiles (AIPEA) Nomenclature Committee for 2001: Order, disorder and crystallinity in phyllosilicates and the use of the ‘Crystallinity Index’

The purpose of this report is to describe the appropriate use of indices relating to crystallinity, such as the ‘crystallinity index’, the ‘Hinckley index’, the ‘Kubler index’, and the ‘Arkai index’. A ‘crystalline’ solid is defined as a solid consisting of atoms, ions, or molecules packed together in a periodic arrangement. A ‘crystallinity index’ is purported to be a measure of crystallinity, although there is uncertainty about what this means (see below). This report discusses briefly the nature of order, disorder and crystallinity in phyllosilicates and discusses why the use of a ‘crystallinity index’ should be avoided. If possible, it is suggested that indices be referred to using the name of the author who originally described the parameter, as in ‘Hinckley index’ or ‘Kubler index’, or in honour of a researcher who investigated the importance of the parameter extensively, as in ‘Arkai index’. In contrast to a crystalline solid, an ‘amorphous’ solid is one in which the constituent components are arranged randomly. However, many variations occur between the two extremes of crystalline vs. amorphous. For example, one type of amorphous material might consist simply of atoms showing no order and no periodicity. Alternatively, another amorphous material may consist of atoms arranged, for example, as groups of tetrahedra (i.e. limited order) with each group displaced or rotated (e.g. without periodicity) relative to another. Thus, this latter material is nearly entirely amorphous, but differs from the first. Likewise, disturbance of order and periodicity may occur in crystalline materials. The terms ‘order’ and ‘disorder’ refer to the collective nature or degree of such disturbances. Although seemingly simple notions, ‘crystalline’ and ‘amorphous’ are complex concepts. Crystalline substances may show a periodic internal structure based on direction. For example, two-dimensional periodicity is common in phyllosilicates where two adjacent sheets or layers must mesh. For example, …

Surface reactivity of poorly-ordered minerals in podzol B horizons

The surface reactivity of mineral soil horizons from three podzolised forest soils in Scandinavia was examined. The amount of accumulated C was low, between 1.8 and 2.3% in the top of the B horizon ...