Abstract: By the methods of direct viable count and plate count,this paper studied the effects of different selective extractants on the bacteria,algae and protozoan on the biomembrane in natural water body.The results indicated that the stronger the extraction ability of selective extractant,the fewer the living microorganisms on the biomembrane after extraction.Compared with the control,the percentages of living microorganisms on the biomembrane were 27.6,14.1 and 0.01,respectively,after extracted by hydroxylamine hydrochloride (0.01 mol·L^-1 NH₂OH·HCl+0.01 mol·L^-1 HNO₃),sodium dithionite (0.4 mol·L^-1 Na₂S₂O₄,pH 6.0),and acidified ammonium oxalate.Very few bacteria was left after extracted by nitric acid (15% HNO₃),and no microorganisms could be detected after extracted by H₂O₂/HNO₃,suggesting that the use of selective extractants affected the activity of biomembrane.With the decreasing amount of microorganisms on the biomembrane after treated with selective extractants,the adsorption of heavy metals by the biomembrane was gradually depressed.

Key words: Forest edge, Air temperature, Surface temperature, Air minus soil temperature, Thermal active surface