RESUMO
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.
RESUMO
We have designed a laboratory bioassay to expose fish to kinetically determined differences in aluminium hydroxide solution chemistry. We have used this system to demonstrate the hitherto unexpected result of an acute aluminium toxicity in the fish at a pH of 6.5. Supporting experiments have demonstrated that the mechanism of toxicity at this pH was probably an asphyxiation brought about by aluminium-induced changes in the rheological and diffusional properties of the mucus lining of the gill epithelium.