The characteristics of Cu2+ adsorption-desorption by soils in the Yellow River Delta were studied using isothermal equilibrium adsorption method.Differences in the adsorption-desorption capacity of soils in farmland and unused land were compared and the reasons for the differences were analyzed. Results showed that the adsorption capacity for the two types of soils increased with Cu2+ equilibrium concentration. he adsorption characteristics could be simulated by Langmiur

Freundlich and Temkin models.Langmuir model was found to be the best one. The maximum adsorption capacity of soil was 3961mg/kg for farmlandand 3 521mg/kg for unused land

respectively. The Cu2+ adsorption capacity of soil in farmland was much higher than that in unused land. The Cu2+ desorption capacity was far lower than the Cu2+adsorption capaci-ty. There was an obvious lag period of the Cu2+ desorption by soil in unused land

as compared with that in farmland. The Cu2+ desorption ratio for soil in unused land was greater than that in farmland

and the de-sorption ratio was between 0.1% and 0.35%in farmland and between 0.15% and 1.8%in unused land

respectively. The results from the comprehensive analysis suggest that the differences in the adsorption-desorption for the two types of soils are related with soil organic matter content which leads to more adsorp-tion points on the soil colloid surface in farmland.