| In this paper,the effects of natural rainfall and cadmium contaminated water irrigation on the cadmium loss in soil and rice-soil system were studied under potted rice and plant-free conditions.The effects of loss of runoff and loss of sediment on the flux of cadmium were discussed.Finally,the characteristics of input and output fluxes of cadmium in irrigation water-soil system were summarized.In this study,CK(0?g?L-1)?Cd2(2?g?L-1)?Cd5(25?g?L-1)?Cd10(10?g?L-1)?Cd15(15?g?L-1)?Cd20(20?g?L-1)and Cd40(40?g?L-1)were used to analyze the results.The main results were as follows:?1?In the rice-soil system,the flux of cadmium in the water samples was positively correlated with the rainfall and the concentration of cadmium in the irrigation water.The flux of cadmium in the sediment was not significantly correlated with the rainfall and the concentration of cadmium in the irrigation.Compared with the control group,when the rice was planted,the amount of water loss and sediment loss decreased and the total flux of cadmium decreased,which indicated that the vegetation cover and root fixation had some buffering for the erosion of rain and runoff effect.?2?Adsorption of cadmium on the sediment concentration is much higher than the cadmium concentration in the water sample.In the rice-soil system,the flux of cadmium in the water sample accounts for more than 60%of the total flux of cadmium.Because cadmium water solubility is strong,and the loss of water is much larger than the amount of sediment,so the flux depends on the loss of cadmium in the water concentration.?3?Cadmium low concentration irrigation water promotes rice growth,cadmium high concentration irrigation water inhibits rice growth.With the increase of cadmium concentration in irrigation water,the contents of cadmium in various organs of rice were significantly increased.The overall distribution of cadmium in various organs of rice was:root>stem and sheath>leaf>rice husk>brown rice.?4?With the increase of the concentration of cadmium added in the irrigation water,the proportion of cadmium with the runoff gradually decreased.In the absence of plant cultivation,the exogenous cadmium added to the irrigation water is mainly accumulated in the soil.When the rice is planted,the runoff loss is very smal.The input of irrigation water is mainly absorbed by rice.Only when the concentration of cadmium in irrigation water is high(>20?g·L-1)only a small amount of exogenous cadmium accumulated in the soil.?5?Under the experimental conditions,the empirical model of the input and output flux of cadmium in the irrigation water-soil system is:????6?In this experimental condition,the empirical model of the input and output flux of cadmium in the irrigation water-rice-soil system:????7?Through the test of the model,it is found that the empirical model of CD flux loss is more in line with the actual situation.Under the condition of rice planting,the flux loss of cadmium is less than the measured value. |
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