Study On Migration And Bioavailability Of Cd In Reclaimed Water-Soil-Vegetable System

Reclaimed water used for irrigation is an important measure to solve the water shortage in today's society.Long-term used recycled water for agricultural irrigation will have an impact on the quality of soil,vegetables and fruits in irrigated areas,so strict implementation of water quality standards to prevents the soil,vegetables,fruits pollution of Cd in the agricultural irrigation process.The study on the migration and bioavailability of Cd in the reclaimed water-soil-vegetable system can be used to accurately and scientifically evaluate the degree of Cd pollution in soils,vegetables and fruits by qualitative,quantitative and location studies of Cd in this system.The extensive use of recycled water and the safety of vegetables to provide a scientific basis.The study of Cd in the soil-vegetable system was studied by analyzing the morphology of Cd,the centrifugation of water samples,the special anion membrane test and the simulated in vitro gastrointestinal experiments.?1?In 2015,potted planting cabbage,radish and chilli experiment,washed with water,clean water+Cd,reclaimed water,reclaimed water+Cd(Cd²⁺=0.05 mg/L),and used the BCR method to detect the morphology of Cd in irrigation water,potted soil,pelvic floor leachate and vegetable dry sample.Analysis results:the main form of Cd in irrigation water is B0,the total did not exceed GB5084-2005 Irrigation Water Quality Standards.The main forms of Cd in soil samples and leachate were B4,B3 and B1,and the total amount of soils exceeded GB15618-1995 Soil Environmental Quality Standard.The main form of Cd in vegetables is B0,B2,B3,3 categories of vegetables edible part of the Cd content:pepper>cabbage>radish,and only pepper beyond GB2762-2012 Food Safety National Standard Pollutant Limit.?2?Water samples were centrifuged,the water samples were centrifuged after different gravity field,Kd value showed a rising trend,and water>reclaimed water;The particle size of the supernatant gradually decreases with the increase of the rotational speed,and the Cd content of the heavy metal decreases gradually,which indicates that Cd is easily adsorbed on the particles with smaller particle size,even if the particle size is larger Of the external disturbance,it is not easy to precipitate.?3?The results show that the migration of Cd in the soil is slow and sticky under the irrigation of reclaimed water.The results show that the migration of Cd is the same as that of the untreated water,The results showed that there were plant roots,Cd was easily enriched at the bottom of the potted soil,and the percentage of Cd in the soil near the plant roots was smaller.The migration rate of Cd was higher than that of reclaimed water.?4?The ZRS-8GD intelligent drug dissolution apparatus was used to simulate the human digestion process,and the concentration of Cd in the reaction solution was measured.and the edible safety of the vegetables was evaluated.The results showed that the Cd concentration in the stomach stage was smaller than that in the small intestine stage,but did not exceed the total amount of Cd in the edible part of the vegetable.The bioavailability of Cd in the gastric stage was also smaller than that in the small intestinal stage.Cd was more easily absorbed by the human body in the small intestinal stage.Experimental vegetable PTWI values are not exceeded,the safety of edible vegetables no threat.