Metla Project 3216

Environmental Impacts of Wood Ash and its Heavy Metals

[  Suomeksi  |  Objectives  |  Results  |  Project leader  |  Researchers  |  Publications  |  Metla Research  ]

Duration: 1997-2002   Keywords: ash fertilization, berries, cadmium, fungi, leaching, microbes, mineralization, mycorrhizae, nitrogen, phosphory

Objectives

The use of wood ash in forestry has been questioned because the potential risk associated with its cadmium (Cd) content (1-30 mg kg-1). In agriculture, wood ash is only allowed for use as fertilizer when its Cd content is below 3 mg kg-1. This restriction has not been applied to forest soils and there is a lack of knowledge about the potential harmful effects of the Cd in wood ash on forest ecosystems. This paper summarizes our recent studies on the microbial communities of boreal coniferous forest humus exposed to Cd-containing wood ash treatment. The main objectives of our studies were to test if the Cd in wood ash has the potential to affect the humus layer microflora of coniferous upland forests and if the Cd has the potential to enter the human food chain. These objectives were tested both in laboratory and field experiments with ash and ash spiked with Cd (in laboratory 400 or 1000 mg Cd kg-1 as CdO or CdCl2; in field 400 mg Cd kg-1 as CdO). In one study the dissolution of ash was accelerated by irrigating it with simulated acid rain (SAR).

Results

Wood ash increased humus layer pH and microbial activities (respiration or thymidine incorporation rates) and changed its microfloral community structure (Biolog®, PLFA, 16S or 18S rDNA PCR-DGGE) in both laboratory and field and experiments. Spiking ash with Cd induced no further changes in the above-mentioned variables as ash alone. The Cd added with wood ash did not become bioavailable as detected with a bacterial biosensor Bacillus subtilis BR151(pTOO24). The form and level of Cd added in the ash had no further effect on the microbiological variables studied. Irrigation of ash with SAR did not increase the amount of bioavailable Cd, although the dissolution rate of the ash was increased. The concentration of Cd in soil water and in the berries of Vaccinium uliginosum and V. vitis-idaea, and the amount of humus bioavailable Cd did not increase with the ash or ash spiked with Cd although the ash spiked with Cd increased the amount of humus total and extractable Cd in the 4 year field study. Only the ash spiked with Cd and not the unspiked "normal" wood ash resulted in significantly higher Cd concentrations in the mushroom Lactarius rufus and a slight increase in the berries of Empetrum nigrum (first year only).

Project leader: Fritze, Hannu
The Finnish Forest Research Institute, Vantaa Unit, PL 18, FI-01301 VANTAA, FINLAND
Phone: +358 29 532 5416
E-mail: hannu.fritze@metla.fi

Other researchers: Domisch, Timo, JO (2002), Jaatinen, Krista, VA (2000-02), Kiikkilä, Oili, VA (1999-2002), Kitunen, Veikko, ES (2001), Moilanen, Mikko, MU (1997-2003), Palviainen, Marjo (2002), Pennanen, Taina, VA (1997-98), Perkiömäki, Jonna (1999-2000), Piirainen, Sirpa, JO (1997-2001), Potila, Hannamaria (1997), Ruokolainen, Maija, ES (1998-2000,2002), Tatti, Leena (2000)


Top of page

Updated 12.06.2012
Comments