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Podzols are soils that display a unique vertical distribution of soil organic matter (SOM). We hypothesise that podzolisation, as a pedogenetic process, influences or even controls content, allocation and quality of SOM. We determined soil organic carbon (SOC) and nitrogen (N) contents in six SOM fractions obtained from mineral horizons of five soils with increasing degree of podzolisation: sand and stable aggregates (S + A), particulate organic matter (POM) > 63 pm and Additional keywords: fractionation, infrared techniques, Podzols. Received 10 June 2020, accepted 11 August 2020, published online 25 September 2020, Introduction Podzols are soils characterised by transformation, mobilisation, vertical transport and subsequent partial precipitation of soil organic matter (SOM) together with iron (Fe), aluminium (Al) and other elements in subsoil [...]

Abstract. Wet-chemical extraction of soil is a standard procedure to characterise pedogenic aluminium (Al) and iron (Fe) species, especially oxides, allophanic minerals and metal-organic associations. This article critically reviews the [...]

Background: Glyphosate (GLP) is a widely used herbicide with possible adverse effects on human health and the environment. In soils, GLP strongly adsorbs on clay‐sized minerals, depending on pH, the amount of organic carbon, as well as the contents and properties of Al and Fe oxyhydroxides and clay minerals. Many clay‐sized minerals have already been investigated regarding GLP adsorption behavior, but information on minerals commonly found in volcanic soils is still lacking. Aim: The aim of this study was to investigate for the first time the pH‐dependent adsorption of GLP on allophane and halloysite, typical minerals found in volcanic soils. Methods: GLP adsorption was studied in batch experiments at three pH values (5, 6, and 7). Synthetic allophanes with two different initial Al:Si ratios (1.4 and 1.8) and a halloysite were used as adsorbents. Results: The adsorption capacity (AC) increased with rising Al:Si ratio and decreasing pH. The AC of allophane was significantly higher than that of halloysite. GLP adsorption on allophane was larger than that reported for other clay minerals and Al and Fe oxyhydroxides, especially at low pH. The AC of halloysite was higher than reported for most other clay minerals. Conclusion: Different mineral formation pathways in volcanic soils, notably the formation of halloysite versus allophanes, strongly affect the soils' retention capacity for GLP. The high AC of allophanes may induce the low mobility of GLP in allophane‐containing soils. Long‐term use of GLP may accumulate the herbicide in these soils with potential effects on biodiversity and ecosystem services. [ABSTRACT FROM AUTHOR]

The presence of geogenic C[O.sub.2] has been recently identified as a soil-forming factor in soil on mofette sites Topsoil samples (with a maximum C[O.sub.2] concentration of 52% at 10 cm depth) were studied along a transect on a mofette site in the NW Czech Republic to further understand the processes within soil and the soil properties induced by C[O.sub.2] in the soil atmosphere. Geogenic C[O.sub.2] negatively affected the cation exchange capacity, the ratio of exchangeable Ca and Mg and the total contents of Al, Mg and Mn. No effect was detected on a chemical index of weathering and the mineralogical composition of the clay fractions, which might be explained by the acidic parent material and the progress of soil development. Diffuse reflectance infrared spectroscopy indicated that the composition of particulate soil organic matter was partially affected by C[O.sub.2] concentrations: the higher the C[O.sub.2] concentrations, the smaller the extent of oxidative transformation and the smaller the abundance of carboxyl groups. In the clay fractions, stabilisation of transformed soil organic matter (SOM) was promoted by exchangeable Al. This study quantifies, for the first time, the correlation between geogenic C[O.sub.2] and several inorganic soil properties and the composition of SOM in physical fractions. Additional keywords: DRIFT spectroscopy, mofette, stabilisation, weathering., Introduction The gas budget in soil on mofette sites in seismic and volcanic areas is controlled by geogenic C[O.sub.2], which has ascended from the Earth's mantle together with Ar, [H.sub.2], [...]

This study focuses on optimising amorphous silica extraction from soils by using NaOH. Based on the results of this test series, a method for quantifying amorphous silica in soils from temperate-humid climate is proposed. All tests were carried out on materials of known composition (well-defined samples of feldspar, clay minerals, bio- opal, silica gel, and mixtures of these components) and on soil samples, to determine the optimum set of conditions, in terms of solid : solution ratio, temperature and extraction time, for dissolving amorphous silica without considerably attacking other solid silicon compounds. A solution of 0.2 m NaOH almost completely extracted amorphous silica, and when applied at room temperature and a solid: solution ratio of 1 :400, only slightly broke down crystalline Si compounds. The predictable and reproducible underestimation was considered more acceptable than the variable partial dissolution of silicates that occurs during extraction at higher temperatures. We therefore recommend using this method on soils from temperate-humid climate to estimate the amorphous Si fraction. Additional keywords: alkaline extraction, silica dissolution, bio-opal. Received 6 July 2014, accepted 10 February 2015, published online 30 June 2015, Introduction Silicon (Si) is the second most abundant element (28.8 mass%) in Earth's crust after oxygen (Wedepohl 1995). It takes part in buffer reactions in soils, thus decelerating soil acidification, [...]

Iron-cyanide complexes are present in soil and ground water because of anthropogenic inputs. We studied the sorption and the transport of the complexes ferrocyanide, [[Fe[(CN).sub.6]].sup.4-], and ferricyanide, [[Fe[(CN).sub.6]].sup.3-], in goethite-coated sand in column experiments under saturated conditions as influenced by flow velocity and flow interruption. Isotherm parameters obtained from batch experiments of Fecyanide complex sorption on goethite were used to simulate breakthrough curves in goethite-coated sand. The breakthrough curves of ferrocyanide were inversely modeled. The transport of both complexes was retarded and rate-limited. Only ferricyanide breakthrough curves revealed concentration drops after flow interruption. Simulations with batch parameters roughly reflected breakthrough curves of ferricyanide, but not of ferrocyanide. Ferricyanide sorption and desorption could not be described with the same isotherm indicating hysteresis. Since the sorption fronts of ferrocyanide breakthrough curves revealed the formation of a shoulder, it was concluded that ferrocyanide sorption in column experiments could not be described by a single isotherm, which is based on a singular sorption process. Therefore, sorption of ferrocyanide on goethite was assumed to be influenced by more than one sorption mechanism. Inverse modeling of ferrocyanide breakthrough data using the Langmuir isotherm resulted in erroneous sorption maxima.

The Fe-cyanide complexes ferricyanide, [[Fe[(CN).sub.6]].sup.3-], and ferrocyanide, [[Fe[(CN).sub.6]].sup.4-], are of an anthropogenic source in soils. As the complexes are largely charged, sorption on the soil matrix is a possible retention mechanism for these anions. To evaluate soil properties controlling Fe-cyanide complex sorption, experiments were performed with 17 uncontaminated soil horizons by a batch technique. Soil organic matter (SOM) was destroyed in six horizons. The experiments were conducted at soil pH, reaction time of 24 h, and an ionic strength of 0.01 (NaN[O.sub.3]). The affinity of the Fe-cyanide complexes for the soil matrix differed, because 14 samples sorbed higher amounts of ferrocyanide than of ferricyanide. Calculated sorption maxima were quantitatively explained by physical and chemical soil properties using multiple regressions. The regression equations were checked by variance analysis. The regression equations for all samples showed that the sorption of both complexes depended on organic C ([C.sub.org]), clay, and oxalate-extractable Fe ([Fe.sub.o]). The sorption of the complexes on soils containing