Acid sulfate soils cover approximately 17 million hectares globally, and their largest deposits in Europe are found in Finland. They cause a widespread environmental risk of metal pollution and acidity for surface waters, resulting in large-scale mass fish deaths and permanent damage to fish populations, water quality and aquatic ecosystems. Currently, metal export from acid sulfate soils is multiple times larger than that of the entire industry in Finland. Biochar is formed as a side product of biomass pyrolysis, with biogas bio-oils and heat as the main products. It has similar properties to activated carbon yet is much cheaper and easier to produce. Thus, it could be employed as a filter material for adsorbing acidity and metals from water on acidic sulfate sites. We tested the ability of biochar to adsorb metals and neutralize acidity with biochar or biochar-ash-filled reactors. Hundreds of liters of runoff water was circulated through the reactors, and we introduced dilutions to study the desorption of metals. The main research objectives were to study the neutralization of acidity and adsorption of metals with biochar in a setting that resembles field conditions and to determine how including ash alters this. Adsorption was confirmed for multiple metals, and acidity was neutralized. Biochar generally featured slower adsorption for fewer metals than biochar with ash, indicating the importance of the solution pH. If metal was adsorbed, the dilutions did not cause it to desorb back from the biochar. However, ash addition did introduce a release of aluminum.

Primary Presenter: Niko Kinnunen, University of Eastern Finland (niko.kinnunen1@uef.fi)

Authors:

Niko Kinnunen, University of Eastern Finland  (niko.kinnunen1@uef.fi)

Ari Laurén, University of Helsinki  ()

Jukka Pumpanen, University of Eastern Finland  ()

Tiina Nieminen, Natural Resources Institute Finland  ()

Marjo Palviainen, University of Helsinki  ()