RESUMEN
A field experiment to investigate the formation of nitrate as an airstream passes through a hill cap cloud has been performed at the UMIST field station on Great Dun Fell. It has been shown that the aerosol nitrate concentration increased by about 0.5 microg m(-3) as the airstream passed through the cloud during the night. At sunrise the nitrate production disappeared. It is suggested that the most likely mechanism for this nitrate production was due to the solution of N2O5 and NO3 formed from the reaction of NO2 with O3. These higher oxides build up overnight in the absence of short wave radiation to photolyse them. Other possible mechanisms of nitrate production are also discussed.
RESUMEN
A retrospective, multi-source screening study has detected 148 users (110 males, 38 females) of intravenous drugs who presented to all relevant agencies between 1971 and 1973 in Bristol, a city where maintenance therapy is a very infrequent practice. The peak prevalence was found in the age group 20-24 years, and it appeared that the chief sources of drugs were burglaries of chemists' shops and general practitioner prescriptions. Sixty-four per cent of our users had not been notified to the Home Office. Suggestions are made for the future monitoring and development of services.
