English Abstract Particulate ions in air are collected by low volume
samplers on filters containing low levels of these ions. The mean
concentration found in extracts of blank filters compared to the mean
concentration of loaded filters, collected largely in 1990, is 37% for
chloride, 6% for nitrate, 7% for sulphate and 31% for ammonium. Three blank
correction methods are evaluated. The correction method with the mean of 8
blank filters of the adjacent period gives a trend compensation with an
negligible increase of the random error. Comparison of the ion
concentrations found in field blanks (A), with ion concentrations found in
blank filters itselves (B) showed no differences. Contamination caused by
the extraction procedure could not be demonstrated.