Indicators of pedogenesis of Technosols developed in an ash settling pond at the Bełchatów thermal power station (central Poland)

Abstract

Technogenic soils (Technosols) developed in an ash settling pond at the Bełchatów thermal power station, central Poland, were studied in order to identify soil property transformations over 30 years of pedogenesis. Standard pedological methods were applied in order to determine the properties of the studied samples. All investigated soils were classified according to WRB as Spolic Technosols with various supplementary qualifiers (Alcalic/Hypereutric, Arenic/Loamic, Protocalcic, Hyperartefactic, Immisic, Laxic, Ochric, and Protosalic). The studied materials can be arranged into a chronosequence starting from fresh (unweathered) ashes, by young Technosol BE1 (age: several months), up to older Technosols BE2 (about 20 years) and BE3 (about 30 years). The studies showed that weathering and soil-forming processes changed properties of ash in soil environment. Fresh ash was characterized by high pH (11.0 – fly ash, 8.7 – bottom ash), low content of carbonates (1.5% in both samples), variable concentrations of TOC (1.2% – fly ash, 6.9% – bottom ash), and very low total nitrogen content (0.04%). Electrical conductivity (ECe) was 2.6 and 2.1 dS·m−1 in fly ash and bottom ash respectively. Young Technosol BE1 had the pH 9.2–10.0, contents of carbonates were in the range 2.4–3.3%, TOC 1.3–1.7%, and total nitrogen less than 0.03%. ECe in young Technosol was in the range 2.7–4.0 dS·m−1. There was no plant cover present on that soil and no well-developed genetic horizons were distinguished in the profile. Finally, old Technosols BE2 and BE3 had lower pH (from 7.9 up to 9.1), and, in general, higher contents of carbonates (from 1.5 to 7.9%) than fresh ash and young Technosol BE1. Old Technosols contained high concentrations of TOC (up to about 38% in Oi horizon) and total nitrogen (up to 0.9%) in the topsoil, where O and A horizons developed due to accumulation of soil organic matter. ECe in old Technosols was in the range 0.8–1.5 dS·m−1. All studied ashes and soils were characterized by very low or even absence of total potential acidity. Base cations predominated in the sorption complex of the investigated ash and soils and can be arranged in the following order according to the abundance: Ca>Mg>K>Na. Base saturation (BS) of fresh ashes and Technosols was nearly 100%. The study shows that the first indicators of pedogenesis of the studied technogenic soils within the first 30 years of formation are: (1) changes of consistence of ash material from firm to friable/very friable due to root action, (2) accumulation of soil organic matter in the topsoil and formation of O and A horizons, (3) decrease of pH, (4) formation of pedogenic carbonates in soils and (5) decrease in soil salinity.

Polish Soil Classification, 6th edition – principles, classification scheme and correlations

“…In this context, questions are increasingly asked about the soils of ecosystems artificially created by humans or created by natural forces in an environment that has been substantially altered or created by man; for example, soils of road or railway embankments, earth covers on bunkers and other constructions, on green roofs, in niches on buildings and ruins filled with "anthropogenic regolith" etc. (Charzyñski et al 2013a(Charzyñski et al , 2013b(Charzyñski et al , 2015Uzarowicz et al 2017Uzarowicz et al , 2018. In all these ecosystems, there are similar minerals that build natural soils, similar microorganisms enabling the circulation of matter and energy flow typical for soils, as well as enabling plant growth and soil fauna occurrence.…”

Morphological Features of Plants on Ash Settling Ponds. Case Study

“…W. Watson and C. winterianus Jowitt ex Bor. The role of the root system in breaking the compact ash layer and loosening its structure was explained by Uzarowicz et al [ 12 ].…”

“…Thus, a longer biomass of green parts, i.e., stems, leaves) indicates a better (wider/deeper) development of the root system [ 11 ]. However, in the experimental plots, the ash substrate contains not only nutrients, but also numerous heavy metals (HMs) [ 4 , 12 ] the presence of which negatively affects the biochemical processes taking place in the plants. This limitation especially applies to the development of seeds, associated with a significant energy expenditure for the plant.…”

Studies of technogenic soils in Poland: past, present, and future perspectives

“…Carbon and macronutrient budgets under alder plantation grown on a reclaimed ash landfill were examined by Woś et al (2020) and mercury concentration in the ash soils and in tissue of alder used to reclaim the combustion waste disposal site was determined by Woś et al (2019). Uzarowicz and Zagórski (2015), and Uzarowicz et al (2017Uzarowicz et al ( , 2018aUzarowicz et al ( , 2018b recognized physical and chemical properties of the Spolic Technosols developed from ash from coal and lignite combustion as the basis for soil classification. They determined morphological, physico-chemical and mineralogical indicators of Technosols transformation, as well as developed a concept of evolution of the Technosols developed from ash under existing environmental conditions.…”