Research paper Elements availability in soil fertilized with pelletized fly ash and biosolids Evelina Br € annvall a, * , Martin Wolters a , Rolf Sj € oblom a, b , Jurate Kumpiene a a Waste Science & Technology, Luleå University of Technology, 97187 Luleå, Sweden b Tekedo AB, Spinnarv€ agen 10, 611 37 Nyk€ oping, Sweden article info Article history: Received 5 February 2014 Received in revised form 15 May 2015 Accepted 23 May 2015 Available online 29 May 2015 Keywords: Sequential extraction Rhizosphere Pore water Plant uptake Fly ash Pellets abstract The aim of the study was to evaluate the impact of combined and pelletized industrial residues on availability and mobility of nutrients and potentially toxic elements in soil, plant growth and element uptake. Plant pot experiments were carried out using soil to which 2% of pelletized residue containing biosolids mixed with either municipal solid waste incineration fly ash (MFA) or biofuel fly ash (BFA) was added. The tests showed that the plant growth did not correspond to the content of available nutrients in fertilised soil. MFA application to soil resulted in elevated concentrations of P (506 mg/kg), As (2.7 mg/ kg), Cd (0.8 mg/kg) and Pb (12.1 mg/kg) in soil, lower plant uptake of Al (25 mg/kg) and Ba (51 mg/kg), but higher accumulation of As (4.3 mg/kg) and Cd (0.3 mg/kg) in plants compared to the unamended soil and soil amended with BFA. On average, the biomass of the plants grown in the soil containing MFA was larger than in other soils. Considering the use of industrial residue mixtures as soil amendments or fertilizers, the amount of added elements should not exceed those taken up by plants, by this preventing the increase of soil background concentrations. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction Currently, the recycling of industrial residues such as biofuel fly ash, an air pollution control residue from combustion of wood- based fuel and municipal sewage sludge (biosolids) to soil as the source of nutrients is encouraged (Swedish Forest Agency, 2008; Swedish EPA, 2002). However, due to a very high alkalinity of fresh ash (pH z 12), a direct application to soil is not recom- mended. Application of the powdered residue to soil may lead to phytotoxic effects and suppressed plant growth (Br€ annvall et al., 2014a). Results of this study showed that powdered residues such as fly ash could be toxic to the plants, especially those fly ashes from the municipal solid waste incineration. Taking into account the results from the previous studies by Br€ annvall et al., 2014a and Br€ annvall et al., 2014b industrial residue mixtures (biosolids and fly ashes) have been further treated. It is known that processing of the residues, e.g. through pelletization, granulation and ageing, might transform the residues into a product that has a lower pH and is easier to handle. Granulated/pelletized residues have a smaller specific surface area compared to powdered ones, which leads to a reduced reactivity and a slower release of constituents (Eriksson, 1998; Larsson and Westling, 1998; Steenari et al., 1998; Nieminen et al., 2005). This is advantageous for the release of potentially toxic elements, which is expected to be smaller than from fresh residues. A slow release of P and N might also reduce the loss of nutrients from the fertilised areas. The aim of this study was to evaluate the impact of combined and pelletized industrial residues containing biosolids mixed with either municipal solid waste incineration fly ash or biofuel fly ash on availability and mobility of nutrients and potentially toxic ele- ments in soil and their uptake by plants. Detail characterisation of raw residues and their mixtures was performed are presented in Br€ annvall et al., 2014b. Also element availability for plants when powdered i.e. not pelletized fly ash and biosolid mixtures were used and are described in Br€annvall et al., 2014a. In this paper pelletized residue mixtures as soil fertilizers and element availability for plants is evaluated. * Corresponding author. E-mail address: evelina.brannvall@ltu.se (E. Br€annvall). Contents lists available at ScienceDirect Journal of Environmental Management journal homepage: www.elsevier.com/locate/jenvman http://dx.doi.org/10.1016/j.jenvman.2015.05.032 0301-4797/© 2015 Elsevier Ltd. All rights reserved. Journal of Environmental Management 159 (2015) 27e36