The sixth edition of the Polish Soil Classification (SGP6) aims to maintain soil classification in Poland as a modern scientific system that reflects current scientific knowledge, understanding of soil functions and the practical requirements of society. SGP6 continues the tradition of previous editions elaborated upon by the Soil Science Society of Poland in consistent application of quantitatively characterized diagnostic horizons, properties and materials; however, clearly referring to soil genesis. The present need to involve and name the soils created or naturally developed under increasing human impact has led to modernization of the soil definition. Thus, in SGP6, soil is defined as the surface part of the lithosphere or the accumulation of mineral and organic materials permanently connected to the lithosphere (through buildings or permanent constructions), coming from weathering or accumulation processes, originated naturally or anthropogenically, subject to transformation under the influence of soil-forming factors, and able to supply living organisms with water and nutrients. SGP6 distinguishes three hierarchical categories: soil order (nine in total), soil type (basic classification unit; 30 in total) and soil subtype (183 units derived from 62 unique definitions; listed hierarchically, separately in each soil type), supplemented by three non-hierarchical categories: soil variety (additional pedogenic or lithogenic features), soil genus (lithology/parent material) and soil species (soil texture). Non-hierarchical units have universal definitions that allow their application in various orders/types, if all defined requirements are met. The paper explains the principles, classification scheme and rules of SGP6, including the key to soil orders and types, explaining the relationships between diagnostic horizons, materials and properties distinguished in SGP6 and in the recent edition of WRB system as well as discussing the correlation of classification units between SGP6, WRB and Soil Taxonomy.

Despite 30 years of work on the issue of urban soils, there are still differences in opinions on the real significance of soil diversity for the functionality of urban areas. This also reflects a significant difference in the perception of the environment itself by representatives of natural sciences and engineering. The research was carried out in the town and administrative commune of Zielona Góra—a medium-sized town located in the western part of Poland (51°56′07″ N, 15°30′13″ E). This paper is a synthesis of more than a decade of research on soils covering the Zielona Góra urban area. A total of 562 samples were analysed from 105 soil profiles (to a depth of 150 cm) and 32 additional surface samples. Soils were classified according to the WRB 2007. Laboratory tests were conducted using standard procedures for soil investigation. As a result of the research, several soil groups were identified in a relatively small area—Podzols, Brunic Arenosols, Luvisols, Albeluvisols, Gleysols, Phaeozems as well as large areas covered by Hortic Anthrosols, Technic Regosols, Technic Arenosols, Mollic Technosols, Urbic Technosols and Ekranic Technosols. It was found that the transformation of soil under different land use forms was diversified, which was especially connected with soil profile decapitation, building rubble admixture, admixture of wastes, soil covering and compacting. As a consequence of this, different soil properties were noted, especially calcium carbonate content, pH, EC and concentrations of Cu, Pb and Zn. Urban soils are frequently characterized by a strong horizontal and vertical heterogeneity. The differentiation of the soil sites is significantly related to the site age, human impact intensity and the form of land use. Not all properties of soils within urban areas are spatially strongly diversified when areas with a similar construction and use are taken into account. pH values and particle size distribution are unified over large areas of the city.

Purpose Despite the many studies of urban soils, a comparative analysis for cities of a similar size has not yet been conducted. Thus, the aim of this review paper was to compare the soil distribution patterns in the area of two medium-sized Polish cities (Toruń and Zielona Góra). The authors attempted to answer the question of how natural and technogenic factors contributed to the transformation of urban soils and what the similarities and differences are between these two studied cities. Materials and methods First, both the natural and the human-related (including historical) factors influencing the soil formation in the studied cities were analysed. Then, a comparison of the degree of transformation of the urban soil environment was presented. The data obtained by the authors during nearly two decades of research (over 200 soil profiles) were used. Results and discussion Intensive development of the built-up areas in Toruń brought heavy and long-term transformations of soils, which demonstrate the typical properties of Urbic Technosols, Ekranic Technosols and other technogenic soils. Zielona Góra showed a similar state of soil transformation over a considerably smaller area. Currently, the differences in the soil properties in many built up areas have been blurred, despite the habitat and historical base. The similarities of the soil properties concerned, in particular, a high content of skeletal remains (from a few to over 30%), elevated pH (in KCl) values (even above 8.0) and the artificial soil horizons formation. Both cities struggle with similar problems regarding the changes in the land use within the areas covered by these soils. Conclusions It was found that, despite the significant habitat and historical differences between the two studied cities, most of the urban soils, especially Urbic Technosols, Ekranic Technosols and Regosols (Relocatic and Technic), are characterised by similar morphology and properties. The most important differences are the time and scale of the area transformation, which influence the extent of Technosols and Anthrosols within the city borders. The most distinct differences concern the natural and slightly transformed soils, which are the results of various soil-forming factors.

Biomass can be used for the production of energy from renewable sources. Because of social resistance to burning crop plants, mixtures and pellets made from or including waste materials are a good alternative. The mixtures analyzed, prepared from wood and municipal waste, were characterized for their calorific values, 7.4–18.2 MJ·kg⁻¹. A result, over 15 MJ·kg⁻¹ was obtained for 47% of the quantities of mixtures being composed. It has been demonstrated that wood shavings and sewage sludge have a stabilizing effect on the durability of pellets. The emissions of acidic anhydrides into the atmosphere from the combustion of pellets from waste biomass were lower for NO, NO₂, NOx and H₂S than emissions from the combustion of willow pellets. Obtained emission results suggest the need to further optimize the combustion process parameters.

Biomass combustion is technologically difficult. It is also problematic because of the necessity to manage the ash that is generated in the process. The combustion of biomass pellets is optimum when their moisture is 6–8%. The calorific value of pellets made from straw and willow wood (4:1) was 17.3–20.1 MJ∙kg⁻¹. There were serious problems with burning this material caused by the accumulation and melting of bottom ash on the grate, which damaged the furnace. These problems with optimizing the biomass combustion process resulted in increased CO emissions into the atmosphere. It was shown that pelletization could also be used to consolidate the ash generated during the combustion process, which would eliminate secondary dust during transport to the utilization site. For this purpose, it was suggested to add binding substances such as bentonite and bran. The analysis showed that an optimum material for pelletization should contain, on average, 880 g of ash, 120 g of bentonite, 108 g of bran, and 130 g of water.

Technosols are relatively young soil group in WRB soil system, and there is still a lot of to do to better understand processes taking place in these soils and to classify them in a proper way. The objectives of this paper were to (1) evaluate Technosol and 'technogenic' qualifiers for other Reference Soil Groups, and (2) propose new solutions which would improve the classification of technogenic soils in WRB. New qualifiers . Edific, Nekric, Misceric, Artefactic, Radioactivic and new specifier . Technic . are proposed to be added to keys to Technosols. Moreover, Salic and Sodic qualifiers should be also available for Technosols. Furthermore, the supplementation of definitions of thionic horizon and sulphidic material with reference to Technosols is also suggested