Heat–induced changes in soil properties: fires as cause for remobilization of chemical elements

Abstract

Exposure of soil constituents to elevated temperatures during wildfire can significantly affect their properties and consequently, increase the mobility of the bound contaminants. To estimate the potential of wildfires to influence metal remobilization from the burned soil due to the changes in cation exchange capacity (CEC) after organic matter combustion and mineral alteration and degradation, changes in soil properties after exposure to different temperatures was investigated. This was accomplished through analysis of geochemical, mineralogical and surface physicochemical properties of a soil sample exposed to different temperatures in a laboratory. Heating the soil sample at 200 °C, 500 °C and 850 °C resulted in an increase in pH (from 5.9 to 12.3), decrease in cation exchange capacity (from 47.2 to 7.3 cmol+kg−1) and changes in the specific surface area (observed only at 500 °C), that are associated with structural modifications of clay minerals and ferromagnetic minerals. Extraction analysis showed the increase in the concentration of almost all analysed elements (Al, Cd, Co, Cr, Fe, Mn and Zn) in soil eluates. The observed increase, following high– temperature heating (500 °C and 850 °C), was as much as 15 times higher (e.g., Al), compared to the native soil sample (25 °C). This strongly indicates that wildfire can act as a trigger for remobilization of heavy metals.

Influence of meteorological factors on the moisture content of fine forest fuels: responses of fire danger class to different microclimates on the example of European beech (Fagus sylvatica L.) stands

“…Fires in the natural environment and forests primarily affect middle-earth areas, resulting in damage or destruction of the productive and non-productive functions of the forest and endangering human life (Cerdà et al, 2022;Fajković et al, 2022;Hološ et al, 2022). Climate, topographical conditions, and vegetation cover are among the main factors that influence the occurrence and spread of fire.…”

Alterations in aggregate characteristics of thermally heated water-repellent soil aggregates under laboratory conditions

“…Wildfires disrupt forests altering the physical, chemical, and biological characteristics of the underlying soils. The heat generated during a wildfire increases the soil temperature (Fajković et al, 2022;Li et al, 2022;Neary et al, 1999 and references therein), which has a significant influence on the SWR (Caltabellotta et al, 2022;Doerr et al, 2004;García-Corona et al, 2004;Hološ et al, 2022;Novák et al, 2009;Plaza-Álvarez et al, 2018;Zavala et al, 2010). There are pieces of evidence available to show that the heat generated by wildfire can either increase, decrease, or eliminate the SWR conditions (Doerr et al, 2006;Zavala et al, 2010).…”

Introduction to the special issue on fire impacts on hydrological processes

“…Most of the special issue (Caltabellotta et al, 2022;Ebel et al, 2022;Godoy et al, 2022;Li et al, 2022;Lucas-Borja et al, 2022;Sanin et al, 2022) is devoted to the impact of wildfire or prescribed fire on hydrological processes. The remaining articles are devoted to the heat-induced changes in soil properties (Fajković et al, 2022;Hološ et al, 2022) and the impact of biochar (produced by pyrolysis/heating biomass in the total or partial absence of oxygen) amendment on soil organic molecular markers (Atanassova et al, 2022). Atanassova et al (2022) examined the post-effects of biochar application on biomarker signatures in a maize cultivated Fluvisol, which was treated with 5 and 10 t/ha biochar during the 3-year experiment.…”

“…Changes in soil properties after exposure to different temperatures were investigated by Fajković et al (2022) to estimate the potential of wildfires to influence metal remobilization from the burned soil due to the changes in cation exchange capacity (CEC) after organic matter combustion and mineral alteration and degradation. Heating the soil sample at 200 °C, 500 °C and 850 °C resulted in an increase in pH (from 5.9 to 12.3), decrease in cation exchange capacity (from 47.2 to 7.3 cmol+ kg -1 ) and changes in the specific surface area (observed only at 500 °C), that are associated with structural modifications of clay and ferromagnetic minerals.…”