A study of purification capacity of vadose zone on pollutants from infiltration water in the Luohe alluvial plain

Vadose zone is the main channel of groundwater recharge and pollution. The nature of the vadose zone directly controls the velocity and extent of groundwater pollution.In this paper,lithology（mostly sand and gravel） and the vadose zone of the Luohe bed near Luoyang are examined.The Luohe bed is composed of sub-clay,sub-sand,medium fine sand and other media.The self-purification ability of pollutants of the river bed and the vadose zone is analyzed.The natural self-purification mechanism is briefly analyzed.The results show that the self-purification ability of pollutants of the Luohe bed is as high as 90%（except NO-3）.Sub-clay,sub-sand,medium fine sand and other dielectric layer of vadose zone have a strong capacity to purify heavy metal(Cu2+),but is weak to clean Cl-and Cr6+,because the media can reach saturation state and lose the capacity purification in a short time.Under the similar environmental conditions and the same basic hydrogeological conditions,the thickness of vadose zone has a negative correlation to groundwater pollution.Through the vadose zone can effectively remove the harmful substances in waste water and prevent groundwater pollution.