The total amount of organic carbon in the MSWI bottom ash decreased during open-air storage. Concentrations of organic carbon in aqueous extracts of the ash were similar; though; resulting in increasing percentage of organic carbon over the course of time. The composition of the water leachable organic carbon changed during the open-air weathering towards an increasing amount of hydrophilic organic acids.
Levels of PAHs in the different ashes varied widely. In the MSWI bottom ash and the heating plant ash the levels were low; but in the biofuel and papermill ash mixture; the PAH levels exceeded the Swedish generic guidelines for PAHs in soil. The distribution of PAHs was similar in all ashes and was dominated by the low molecular weight PAHs naphthalene and phenanthrene.