An intercomparison of sampling techniques among five European laboratories for measurements of radiocaesium in upland pasture and soil

An lntercomparison of sampling procedures used by five European laboraiories for the determination of radiocaesium in vegetation and peaty soil was carried out at two locations in Cumbria. The soil sampling procedures included the collection of depth profiles in order to obtain information on the vertical distribution of radiocaesium in addition to the total deposition. The number of samples taken by each laboratory varied from one to five. The multiple sampling has given information on the homogeneity of the parameters studied at each location. The parameters comprise soil bulk densities, total deposition of ¹³⁷Cs, deposition of ¹³⁷Cs in three soil layers, biomass densities, concentrations of ¹³⁷Cs in pasture, and activity ratios (¹³⁴Cs/¹³⁷Cs) in soil and vegetation. The determination of total deposition of ¹³⁷Cs gave no indication of differences between the laboratories. The total depositions of ¹³⁴Cs and ¹³⁷Cs observed at one site were compared with levels obtained from another study and the two
sets of data were found to be in good agreement. The results from the soil profiles do indicate significant differences between laboratories. This covers the vertical distributions of ¹³⁷Cs deposition including the ¹³⁴Cs/¹³⁷Cs-activity ratios as well as the soil bulk densities. One laboratory using a coring technique observed difficulties during sampling due to compression of the soil. The coring technique should thus be avoided or applied with extreme care for the sampling of depth profiles in peaty soil. The results from the sampling of pasture show no indication of differences between the laboratories. For the parameters studied the observed variabilities across soil depths and locations range from 10% to 81% in terms of relative standard deviations. A comparison across all results at the two locations indicate a 50% higher field variability at one of the sites relative to the other.