The study of cobalt leaching from soils, sewage sludges and composts using a one-step extraction

The study evaluated the leaching of cobalt (Co) in soils fertilized with sewage sludge (SS) and composts depending on the extractant used. SS came from rural, mechanical–biological treatment plant in Dobrzeń, Lower Silesia region. In addition, those SS were processed by composting. Sludges and composts were used to fertilise the energy plants during lysimeter experiment conducted during 2008–2013. The overall, as well as extracted by H₂O, 0.1M HCl and 1M HCl, 0.05M Na₂EDTA and 0.1M Na₂EDTA, content of Co in samples were analysed. Additionally, the impact of pH and organic matter (OM) content on the leachability of Co were researched. It was found that the soil samples were rich in Co. Its share slightly depended on fertilisation with SS and compost. Co leaching depends on the type and concentration of extractant. The highest content of Co were leched with 0.1 M Na₂EDTA, and the lowest content with 0.1M HCl. Co concentration in H₂O extracts was not determined as its content was below the limit of quantification. Leachability of Co in the analysed samples was influenced by the overall Co content as well as pH and OM content.