The heterogeneous reactions leading to formation and loss of BrNO2 on salt solutions as a model substrate for atmospheric sea salt aerosol are investigated. Further to the reaction of ClNO2 with bromide solutions, the reaction of Br2 with nitrite solution was found to be a convenient method for the synthesis of BrNO2. We measured the temperature-dependent lifetime of BrNO2 in a quartz cell and obtained the activation energy E A = 89 ± 9 kJ/mol for the unimolecular decay at atmospheric pressure. The reactive uptake of BrNO2 and ClNO2 on water and aqueous solutions was determined using a wetted-wall flow tube technique. We observed the reactions Br2 + NO2 - ↔ BrNO2 + Br-, Cl2 + NO2 - → ClNO2 + Cl-, and the net reaction ClNO2 + Br- ↔ BrNO2 + Cl-. BrNO2 and ClNO2 both react with NO2 - to release NO2 into the gas phase. Observed concentration profiles in the gas phase and in solution can be described qualitatively by a numerical model of the diffusion and reaction processes in the experimental setup.

Positron annihilation phenomenon has been studied in chloropolystyrenes. PAL and ACAR measurements have been performed in air and at room temperature for amorphous samples of different chlorine content. The increase in the latter is followed by the decrease in both the intensity of the narrow component of ACAR curves and the intensity of the longest-lived component (I) in PAL spectra. The latter one, related to the ortho-posi troniurn intensity in polystyrene I: , changes according to the formula: 1~/ 1~1 1 + (1 9. 9 3 *~)~.~~1-~ where C denotes the number of C1 atoms per unit of the polymer. The inductive effect produced by the chlorine in chloropolystyrenes is assumed to be the reason of the inhibition of the positronium formation in them. In general the chlorine reactivity towards positrons seems to depend on its position in the polymer structure. The numerical Laplace inversion technique /1/ has been applied to PAL data to recover the radius distribution of free volumes for each sample of the second series. A tendency towards decrease in mean radius of free volumes is seen when chlorine content increases in studied samples. The only exception is the sample in which the highest amount of chlorine atoms has been substituted at a-carbons in the aliphatic chain.

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Results of angular correlation of annihilation radiation and positron annihilation lifetime measurements are presented for atactic polystyrene and chloropolystyrenes. The inhibition of positronium formation follows the chlorine introduction as the decrease in intensities of the narrow component in angular correlation of annihilation radiation curves and of the longest-lived component in positron annihilation lifetime spectra prove. In general, the chlorine "activity" towards positrons seems to depend on its position in the polymer structure. The annihilation rate distribution as well as the radius and volume distributions of free-volume sites where positronium is assumed to be formed obtained with the use of CONTIN program for the raw sample in the 2nd series are given additionally.