Abstract: pHand CO₂ content differences between fish(Cyprinus carpio) gills micro-environment and the ambient environment were investigated using the technique developed by Playle.The effect of the pHchange on elutriation of copper sorbed on gibbsite was also studied in view of possible desorption of the metal within the gill micro-environment.It was found that there was no pHdifference around pH8.0 and 0.2～0.4 unit difference was observed between the gills' inspired and the expired water when the ambient pHvaried from 8 up to 9.5 or from 8 down to 7.0.Similar trend was detected for CO₂.More Cu adsorbed on the gibbsite can be removed by the acidified expired water from the fish gill micro-environment,comparing to the inspired water.

Key words: Fish, Gills micro-environment, Copper, Elutriation