Measurement of labile metal in soils. Chemical extraction and isotopic dilution data

Soils from four sites (0-20cm) were sampled, air dried and sieved to < 2mm. Soil pH was determined in soil-water suspensions and loss on ignition was used as an estimate of soil organic matter content. Three replicate soil samples were suspended in the extractants 0.43 M HNO3, 0.43 M CH3COOH, 0.05 M Na2H2EDTA and 1.0 M CaCl2. Extraction suspensions were centrifuged at 2200 G for 15 min, and supernatant solutions filtered to < 0.22µm and then acidified to 2% HNO3; samples were stored at 4°C prior to multi-element analysis by inductively coupled plasma mass spectrometry. For the determination of total soil metal concentration soil was agate ball-milled and two replicates digested with 2ml HNO3, 1ml HClO4 and 2.5ml HF. Analysis was carried out at the University of Nottingham, School of Biosciences, Division of Agricultural and Environmental Sciences, during the period 2010-1013, as part of a PhD project.