Cleaning power of different surfactants was investigated using a model detergent system consisting of a PET film and stearic acid. Surfactants used were alcohol ethoxylates (AE, C12) and methyl ester ethoxylates (MEE, C12) with different ethylene oxide (EO) chain lengths. For comparison with these nonionic surfactants, anionic surfactant, sodium alkyl sulfate (AS, C12), was chosen. After depositing stearic acid, the PET film was cleaned in aqueous surfactant solutions by applying stirring as a mechanical action for soil removal. The amounts of stearic acid deposited on the PET film before and after the cleaning were obtained by binary processing of microscopic images of the PET film surface, from which the removal efficiency was calculated. The surface tension γ and the contact angle on the PET film θ of the surfactant solution were measured by the pendant drop and the sessile drop method, respectively. For the nonionic surfactants, critical micelle concentration, cmc, and γ and θ above cmc decreased with decreasing EO chain length. The removal efficiency of stearic acid increased with increasing surfactant concentration and further increase in the removal above cmc was observed in the cases of AE and MEE with EO chain length of 10. The removal efficiencies obtained in all systems had good relation with both γ and θ, indicating that the penetration of the surfactant solution between stearic acid and the PET film in the contact zone was a dominant factor in the soil removal in the present system.

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The removal of the carbon black (CB) particles from the polymer substrates was investigated in water/ethanol mixtures. As substrates, the films and the fibrous assemblies of polyethylene, nylon 6 and cellulose acetate were used. The ultrasonic wave was applied as a mechanical action for cleaning. The detergency of the CB particles for the films and the fibrous assemblies was assessed with the quartz crystal microbalance (QCM) technique and the reflectometry, respectively. The detergency for the films was discussed with the wetting force calculated from the experimentally determined contact angle on the substrate and surface tension of the water/ethanol mixture.

The 35S content in atmospheric deposition, aerosol and rain water was determined about every 10 days for a year with 7Be, 32p and some stable elements. Average 35S concentrations were l l0mBq-m-2-d -1 for atmospheric deposition, 0.078 mBq.m -3 for aerosol in surface air and 45 mBq-I -j for rain water. The ratios of 7Be/35S were abnormally low, although most of 32p/TBe showed the reasonable values corresponding to the residence times from 10 to 60 days. The excess 35S suggests an external source 0f35S or/and a faster cycle of 35S than that of TBe and 32p.

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