Extractable lead concentrations in Scottish soils

The distribution of acetic acid-extractable lead concentration levels in 3764 samples from 751 Scottish soil profiles is reported. The relation of extractable lead concentration to that of total lead and to some other soil variables is also examined.Because the frequency distribution of concentration levels is approximately lognormal, a logarithmic transformation of the data has been performed to provide a more satisfactory means of describing the distribution. The derived mean for the full set of data is 0.24 mg/kg and the normal range 0.016?3.4 mg/kg.Total lead concentration was found to be the dominant factor in determining the level of extractable lead in these soils and it was concluded that it would be more meaningful to consider the extractability of lead (i.e., the percentage of total lead extractable by acetic acid) rather than the absolute level of extractable lead in relation to the various other soil variables which are of interest in this connection.There is evidence that extractability is enhanced under conditions of impeded drainage but none to indicate that it is related to clay or ash content.Extractable lead was found to be generally higher in surface horizons than at depth thus reflecting the pattern of variation exhibited by total lead concentration. Extractability of lead shows little evidence of variation with depth.