Most of the processes occurring in soil are catalysed by enzymes. As a result of their sensitivity towards heavy metals, enzymes in contaminated soils are usually less active. The purpose of this paper was to assess the influence of bioavailable forms of Cd, Cu, Pb and Zn on the activity of dehydrogenases, urease, acid and alkaline phosphatase, and to compare the results obtained from naturally and artificially contaminated soils. A pot experiment was carried out on two loamy sand soils, naturally and artificially contaminated with Cd, Cu, Pb and Zn. The total content of heavy metals classified these soils as very heavily contaminated with Cu, heavily contaminated with Pb and contaminated with Cd and Zn, all according to the IUNG system (1995). One of the following organic materials: swine manure or triticale straw, was added to the soil batches. The experiment was carried out in three replications, in two pH ranges: slightly acid and acid. Soil samples for analyses were taken after 14, 28, 165 and 450 days of incubation. The results of the experiment showed that the activity of soil enzymes depended on the content of bioavailable heavy metals; the total concentration of trace elements and H + were less important. However, considerable differences were found in enzyme activity between naturally and artificially contaminated soils. This indicates that results obtained from other research conducted on freshly contaminated soils cannot be easily transferred to field conditions. The analysed enzymes responded differently to the concentration of bioavailable forms of heavy metals. Alkaline phosphatase was the least tolerant to bioavailable forms of heavy metals, unlike urease, which was the most tolerant soil enzyme. A similar pattern of sensitivity toward trace elements, which could be ordered as Zn > Cd > Cu > Pb, was noticed for dehydrogenases, acid and alkaline phosphatases. Urease was found to be more tolerant to Zn.

The light fraction of soil organic matter (LF) has a rapid turnover and may be potentially metal-enriched, but the interaction between this pool of organic matter and trace elements has not been well studied. The present study aimed to investigate changes in LF content and its effect on heavy metals distribution and extractability in long-term contaminated soil by smelting activity. An incubation experiment was conducted on a surface horizon of Brunic Arenosol sampled from the previously-existing sanitary zone of Głogów smelter, for 450 days. The contaminated soil was divided into three combinations: with the addition of either triticate straw (at the dose of 4.5 Mg ha -1 ) or pig manure (at the dose of 40 Mg ha -1 ) or without any “foreign” organic materials (nil). The LF (ρ > 1.7 g cm -3 ) occurred to be metal-enriched and despite its low content (5.49%—nil, 7.18%—straw and 7.29%—manure combination) in the bulk soil, it was observed that initially Cd, Cu, Pb and Zn stock reached 16.2%, 11.9%, 18.0% and 32.3%, respectively. Incubation conditions where mineralization processes dominate led to a decrease in the LF share by about 12.6% in nil and 31.4–39.8% in the combinations with organic amendments. In consequence, the DOC (dissolved organic carbon) concentration doubled and metal distribution had changed. The increase in water-soluble (F1) fraction was observed for all metals, additionally for Cu, Pb, Zn in exchangeable fraction (F2) and in carbonate bound (F3) fraction for Cd and Zn. These results support the view that changes in the LF content may play a key role in controlling trace metals mobility, especially in long-term contaminated soil.

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Temperate forest soils of Europe are regarded as an important sink of carbon and thought to have potential to sequester CO2 from atmosphere. However, there are insufficient data not only on organic carbon (OC) content in forest soils and its temporal changes but also on microbiological activity and especially their relationship to carbon turnover. In this study seven research plots were located on afforested land in the north-western part of Poland in Tuczno Forest District (Western Pomerania) in order to examine seasonal variation in OC content and dehydrogenases activity (DHA) during 2012–2016. Based on the studies conducted, statistically significant seasonal variation of the OC content was observed. Higher amounts of OC in the A horizon were observed during spring and autumn seasons and lower in summer. However, no seasonal variation on OC content was observed in the organic horizon (O horizon). Although DHA is thought to exhibit strong seasonal variability, no seasonal variation on DHA was observed. However, a statistically significant difference was observed among studied years (2012–2016), a sharp drop of DHA was noted from spring 2014. Statistical analyses revealed that OC content in soils was a function of forest stand age and progressing acidification of soil. Moreover, OC content in O horizon was negatively correlated with soil moisture and DHA, suggesting that periods with higher microbial activity lead to lower accumulation of carbon in the O horizon. During 2012–2016 only for the O horizon was an increase in OC content was observed.

The objective of this study was to examine whether the Polish soil textural classification is useful for evaluation of soil water retention and hydraulic properties and, furthermore, for determining which textural classes are characterized by the highest diversity of soil water retention and hydraulic properties. The texture triangle was divided into a 1% grid of particle-size classes resulting in 5151 different data points. For each data point, soil water retention parameters and saturated hydraulic conductivity were obtained using the ROSETTA program. The silt classes showed the highest uncertainty in the estimation of the saturated water content based on the soil texture. These classes are characterized by high variations of saturated water content within the class. Estimations of field capacity and permanent wilting point on the basis of textural classes are encumbered with highest errors for gp, pg, pl and pyg soils, which are characterized by the highest values of coefficient of variation. Saturated soil hydraulic conductivity is better classified into homogeneous classes by the Polish texture classes than by the clusters obtained by the k-means cluster analysis based on the soil hydraulic and retention properties. Soil water retention parameters are better classified into homogeneous groups by the k-means cluster analysis than by the traditional textural classes. Cluster analysis using the k-means can be helpful for grouping similar soils from the point of view of their retention properties.

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Abstract:The investigation was carried out in the catena of Retisols within the Opalenica Plain. The aim of the study was to characterize the variation in texture of selected Retisols formed from ground moraine glacial till of Leszno Phase of Vistulian glaciation. The analyzed soils are characterized by a similar degree of soil material segregation, which is characteristic for the typical glacial till. Particle size distribution and granulometric indices lead to conclusion that soils located in the catena on summit and shoulder positions, have vertical texture distribution formed primarily by lessivage process. Sandy texture of eluvial horizons noted in the Retisol of the slope pediment can be a consequence of not only lessivage but also of slope forming processes that led to the appearance of lithic discontinuity. The cluster analysis using Ward's method and 1-rPearson as the distance measure can be helpful for identification the lithogenic uniformity and/or non-uniformity of soil parent material.

The paper presents results of determination of temporal changes in water table depths in the toposequence of Retisols/Luvisols and Phaeozems/Gleysols. Assessment of temporal trends in the water table depth was made with the use of the linear regression analysis. The results obtained indicate that the mean water table depth and mean high and low water table depths were deeper in the soil at the upper part of the slope in comparison with soil located at the footslope. A higher amplitude of water table was observed in Retisols than in Gleysols but the highest variability of water table level was noted in the soils at the footslope compared to those at the slope summit. In Retisols, with each month of observation from 1993 to 2012, the water table showed a tendency to increase. These trends were the highest from January to April, which may be related to the tendency of increasing monthly sums of precipitation in December, January and February. In the Gleysol at the footslope, in the period 1993–2012 and in the vegetation season, the water table depth showed a tendency to decrease. This trend may be due to the impact of water table on the soil water content at the root zone, which is used in the process of evapotranspiration.