Biochar is a pyrogenous, organic material synthesized through pyrolysis of different biomass (plant or animal waste). The potential biochar applications include: (1) pollution remediation due to high CEC and specific surface area; (2) soil fertility improvement on the way of liming effect, enrichment in volatile matter and increase of pore volume, (3) carbon sequestration due to carbon and ash content, etc. Biochar properties are affected by several technological parameters, mainly pyrolysis temperature and feedstock kind, which differentiation can lead to products with a wide range of values of pH, specific surface area, pore volume, CEC, volatile matter, ash and carbon content. High pyrolysis temperature promotes the production of biochar with a strongly developed specific surface area, high porosity, pH as well as content of ash and carbon, but with low values of CEC and content of volatile matter. This is most likely due to significant degree of organic matter decomposition. Biochars produced from animal litter and solid waste feedstocks exhibit lower surface areas, carbon content, volatile matter and high CEC compared to biochars produced from crop residue and wood biomass, even at higher pyrolysis temperatures. The reason for this difference is considerable variation in lignin and cellulose content as well as in moisture content of biomass. The physicochemical properties of biochar determine application of this biomaterial as an additive to improve soil quality. This review succinctly presents the impact of pyrolysis temperature and the type of biomass on the physicochemical characteristics of biochar and its impact on soil fertility.

The main aim of this study was the analysis of the interaction between humic acids (HAs) from different soils and Zn(II) ions at wide concentration ranges and at two different pHs, 5 and 7, by using fluorescence and FTIR spectroscopy, as well as potentiometric measurements. The presence of a few areas of HAs structures responsible for Zn(II) complexing was revealed. Complexation at α-sites (low humified structures of low-molecular weight and aromatic polycondensation) and β-sites (weakly humified structures) was stronger at pH 7 than 5. This trend was not observed for γ-sites (structures with linearly-condensed aromatic rings, unsaturated bonds and large molecular weight). The amount of metal complexed at pH5 and 7 by α and γ-structures increased with a decrease in humification and aromaticity of HAs, contrary to β-areas where complexation increased with increasing content of carboxylic groups. The stability of complexes was higher at pH 7 and was the highest for γ-structures. At pH 5, stability decreased with C/N increase for α-areas and -COOH content increase for β-sites; stability increased with humification decrease for γ-structures. The stability of complexes at α and β-areas at pH 7 decreased with a drop in HAs humification. FTIR spectra at pH 5 revealed that the most-humified HAs tended to cause bidentate bridging coordination, while in the case of the least-humified HAs, Zn caused bidentate bridging coordination at low Zn additions and bidentate chelation at the highest Zn concentrations. Low Zn doses at pH 7 caused formation of unidentate complexes while higher Zn doses caused bidentate bridging. Such processes were noticed for HAs characterized by high oxidation degree and high oxygen functional group content; where these were low, HAs displayed bidentate bridging or even bidentate chelation. To summarize, the above studies have showed significant impact of Zn concentration, pH and some properties of HAs on complexation reactions of humic acids with zinc.

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We apply recently developed version of a density functional theory [Z. Wang, L. Liu, and I. Neretnieks, J. Phys.: Condens. Matter 23, 175002 (2011)] to study adsorption of a restricted primitive model for an ionic fluid in slit-like pores in the absence of interactions induced by electrostatic images. At present this approach is one of the most accurate theories for such model electric double layers. The dependencies of the differential double layer capacitance on the pore width, on the electrostatic potential at the wall, bulk fluid density, and temperature are obtained. We show that the differential capacitance can oscillate as a function of the pore width dependent on the values of the above parameters. The number of oscillations and their magnitude decrease for high values of the electrostatic potential. For very narrow pores, close to the ion diameter, the differential capacitance tends to a minimum. The dependence of differential capacitance on temperature exhibits maximum at different values of bulk fluid density and applied electrostatic potential.

Fractal parameters of soils become increasingly important in understanding and quantifying transport and adsorption phenomena in soils. It is not known yet how soil degradation affects fractal characteristics of soil pores. We estimated pore surface area fractal parameters from Hg porosimetry data on samples of a Udic Argiboroll, a Typic Haploboroll, and a Ustolic Orthid before and after simulated soil degradation. Three or four distinct intervals with different fractal dimensions were found in the range of pore radii from 4 nm to 5 µm. This was attributed to differences in composition of soil particles of different sizes. The simulated degradation caused an increase in fractal dimensions in one or more fractal intervals, thus manifesting the increased roughness and irregularity of the pore surfaces. The interval of the smallest radii had the highest average fractal dimension, close to 3; some estimated values were >3, probably due to the compressibility of bulk material and air entrapment. Values of the fractal dimension in this interval increased after cyclic wetting‐drying but were not affected by organic matter oxidation. Smaller fractal dimensions were found in the next interval of radii. Here average fractal dimension increased markedly after organic matter oxidation and grew slightly after cyclic wetting‐drying, reflecting the loss of bonds between particles. The range of largest radii included two fractal intervals after cyclic wetting‐drying and one fractal interval for all other samples. Neither organic matter oxidation nor cyclic wetting‐drying significantly affected the boundaries between the fractal intervals.

The database of Polish arable mineral soils is presented. The database includes a lot of information about the basic properties of soils and their dynamic characteristics. It was elaborated for about 1 000 representative profiles of soils in Poland The database concerns: particle size distribution, organic carbon content, acidity-pH, specific surface area, hydrophobicity - solidliquid contact angle, static and dynamic hydrophysical properties, oxidation-reduction properties and selected biological (microbiological) properties of soils. Knowledge about soil characteristics is indispensable for description, interpretation and prediction of the course of physical, chemical and biological processes, and modelling these processes requires representative data. The utility of simulation and prediction models describing phenomena which take place in the soil-plant-atmosphere system greatly depends on the precision of data concerning characteristics of soil. On the basis of this database, maps of chosen soil properties are constructed. The aim of maps is to provide specialists in agriculture, ecology, and environment protection with an opportunity to gain knowledge of soil properties and their spatial and seasonal variability.

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Fractal theory has been applied to the characterization of particle‐ and aggregate‐size distributions in soils. We used a number‐based method for estimating fragmentation fractal dimensions from these distributions. This method has several inconsistencies. The objectives of our study were to: (i) propose a modified number‐based method, (ii) evaluate the modified method using published data on particle‐ and aggregate‐size distributions, and (iii) apply the modified method to a large particle‐size distribution data base to analyze the validity of fractal scaling. Assuming scale‐invariant fragmentation to be a valid model of particle‐size distribution within size ranges of fractions, we derived a formula expressing the characteristic grain size as a function of the fractal dimension and limits of the grain size range. Parameters of Turcotte's fractal fragmentation model were found by minimizing the sum of squares of differences between measured and calculated masses of grain fractions. Comparison between original and modified number‐based methods showed that the modified method generally resulted in lower fragmentation fractal dimensions than the original method. The modified method was applied to a data set of particle‐size distributions of 2600 soil samples. In 80% of samples, the fractal scaling was not applicable across the whole range of particle size between 0.002 and 1 mm, since errors of the fractal fragmentation model were statistically significantly larger than measurement errors, and estimates of the fractal dimension were larger than 3. It appears that models more sophisticated than scale‐invariant fragmentation are required to simulate soil particle‐size distributions.