Abstract
PurposeThe impacts of fly ash on the chemistry of forest floors were previously described in literature, while impacts on soil properties were less recognised. Soil investigations were focussed mainly on increases of pH and base saturations in surface horizons. The purpose of this study was to describe the influence of alkaline fly ash blown out from the dumping site of a lignite-fired power plant on pH changes of ectohumus horizons of Podzols and the morphology of deeper horizons.Materials and methodsWe investigated the soil profiles of Podzols derived from loose quartz sand and developed under pine forest surrounding the dumping site of the power plant Bełchatów, central Poland. In the vicinity of the fly ash dumping site, five Podzol profiles located at a distance of 50 m from the dumping site were investigated, as well as soil profiles located along the transect set at distances of 50, 300, 800 and 2000 m from the dumping site. Control profiles were located at a distance of 7.3 km from the dumping site. Soil morphology was described in the field and the following properties were determined: soil texture, hydrolytic acidity, exchangeable cations, total organic carbon and total nitrogen content.Results and discussionThe pH values of Podzol ectohumus horizons located close to the dumping site ranged from 6.01 to 7.34 compared to a range of 3.08–3.72 in the control. Ectohumus horizon located 300 m from the dumping site showed a pH range of 4.13–4.26, while at a distance of 800 m, the pH values did not differ from those of the control site. The upper part of the eluvial soil horizons located close to the dumping site had been transformed into transitional AE horizons in which humic substances translocated from ectohumus horizons were accumulated. Moreover, the organic carbon content of this horizon increased compared to the carbon content of the illuvial Bs horizon located below it. Under the influence of alkalisation of upper horizons, the illuvial Bhs horizons vanished and were transformed into Bs horizons.ConclusionsChanges in soils affected by fly ashes are connected with alkalinisation of ectohumus horizons. Podzolisation processes can be reduced or even completely stopped regarding the distance from the dumping site. Eluvial Podzol horizons located close to the dumping site may be transformed into AE horizons in which humic substances translocated from ectohumus horizons are accumulated. Due to transformation and translocation of organic components, Bhs horizons can be transformed into Bs horizons.
Highlights
Anthropogenic factors strongly modify soil properties; their impacts on chemical, physical and biological properties have been reported widely
Changes in soils affected by fly ashes are connected with alkalinisation of ectohumus horizons
Our results show that pH values of Podzol ectohumus horizons located close to a dumping site ranged between 6.01 and 7.34 (Table 2), which is a considerable increase when compared to the control with a range of 3.08–3.72 (Table 1)
Summary
Anthropogenic factors strongly modify soil properties; their impacts on chemical, physical and biological properties have been reported widely. The acidification of the soil environment has been described for many locations, while the opposite effect—an increase of soil pH caused by anthropogenic activity—has rarely been studied (Van Breemen et al 1983; Mandre and Ots 1999; Mandre et al 2008; Pichler et al 2009). Alkalisation is a problem frequently associated with the cement industry, limestone quarrying, production of phosphorus compounds and emission of fly ashes. Almost 70% of ashes are collected as landfills or on dumping sites (Haynes 2009) from where they may be blown out, contributing to alkalisation of the surrounding environment (Jala and Goyal 2006)
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