Abstract: Esterase and peroxidase isozymes of earthworms in polluted soils are studied with polyacrylamide gel disc electrophoresis.The results show that the heavy metal content in earthworms is increased with increasing pollution level, which is 2.27 and 7.30 times higher in heavy polluted soil than in medium and light polluted ones.The Cd, Ph and As contents of earthworms in heavy polluted soil are respectively 47.3, 35.2 and 16.32 μg·kg^-1, and their order coefficient is more than 0.66-0.77.The bands and the activity of esterase isozyme are decreased, and those of peroxidase isozyme are increased.

Key words: Heavy metal pollution, Pheretima californica, Esterase isozyme, Peroxidase isozyme, Enzyme activity, soil salinization, Mu Us desert-loess plateau transition zone, spatial heterogeneity, influencing factors