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Fig. 1. The main result of the Grimsel Colloid Exercise interlaboratory comparison of the cumulative size distribution of colloidal particles recovered at the Grimsel Test Site. Laboratories that contributed to this exercise included: Atomic Energy of Canada, Limited (AECL); British Geological Survey (BGS); Commissariat de l'Energie Atomique (CEA); Paul Scherrer Institute (PSI); Harwell Laboratory Nuclear Physics Division (UKNP); and the University of Norway (UNOS). Techniques used to characterize colloids includes gravimetry (GRAV), scanning electron microscopy (SEM), single-particle counting (PC), and transmission electron microscopy (TEM). The cumulative contribution of different sized particles to the total colloid concentration in Grimsel groundwater (particles [pt] L–1) is indicated. The cumulative size distribution follows Pareto's power law: logCn = 15.8(±0.4) – 3.2(±0.2) log(d), where Cn is the cumulative particle concentration for sizes ranging from 25000 nm to d (Degueldre et al., 1989).
