Study On Purification Processes And Effects Of Cadmium Pollution In Irrigation Water

On account of cadmium pollution in irrigation water as the main source of cadmium pollution in rice and soil,it is of great significance to carry out the study of cadmium pollution in irrigation water.Cadmium purification efficiency in irrigation water and mechanism,including comparing the efficiency of different processes and exploring the best purification conditions,was studied in fields with ecological ditch,biological pond,constructed wetlands and the combination technology,to provide scientific basis and technical support for controlling soil and cadmium pollution from cultivated land.The results are as follows:(1)Cadmium purification efficiency would be more efficient with the more complex process and the higher vegetation coverage.Among the 14 kinds of purification processes,the two-stage ecological ditch + two-stage biological pond +one-stage constructed wetland had the most cadmium purification efficiency in irrigation water,while the two-stage ecological ditch got the most efficient of unit area.Comparing all factors,two-stage biological pond + one-stage constructed was the best purification process?The cadmium efficiency is positively correlated with the water temperature,and the increase of the water retention time decreases the cadmium efficiency(3)Myrtlea,Water hyacinth,Canna Hydrangea,Arundo were better cadmium accunulation plants.(4)The subcellular cadmium content in the each part of algae,arundin and water hyacinth was as follows: the cell wall > soluble components > protoplast ?mitochondria.In the three kinds of aquatic plant,main chemical forms of cadmium was sodium chloride extraction,2% acetic acid extraction states and hydrochloric acid extraction,other three forms including water extraction,80% ethanol extraction and residual states cadmium content was low,and there was no significant difference.