Effects Of Different Application Ways Of Arsenic And Mercury On Uptake And Accumulation Characteristics Of Vegetables

Uptake, accumulation, translocation and distribution of arsenic (As) and mercury (Hg) in vegetables treated with different application ways including hydroponics nutrient solution, irrigation and folia spraying were studied. The edible safety was assessed according to the Hg and As standard tolerance limits and the concentration thresholds of extraneous As and Hg ensuring vegetable safety were proposed. All these results provide theory basis for the establishment and revision of pollutants limits criterion of agriculture input products in order to evade phytogenic agricultural products contamination. Main conclusions were as follows:(1) Diversity of uptake and accumulation characteristics of different vegetables was found. Celery and shallot had the highest ability of concentrating As. Water spinach, spinach, edible rape and carrot root were the second. Edible rape had the highest affinity of low concentration As. Carrot shoot had the highest capability of concentrating Hg. radish root and carrot root were the second. Spinach had the highest affinity of atmospheric Hg.(2) Uptake, accumulation and distribution characteristics of As, Hg in radish and carrot is obvious. As absorbed through roots of carrot was hard to be transported to shoots and 68% kept in root, while Hg absorbed through roots was easy to be transported to shoots and 67% kept in shoot. Hg absorbed through roots of radish was hard to be transported to shoots.(3) There was great difference of the apparent contribution rate of extraneous As to As in edible parts between irrigation application and folia spraying application. The range of the apparent contribution rate of irrigation application As was from 0.02% to 0.05%, while the folia spraying application As range was from 4.49% to 6.71% in the first cut and 9.91% to 17.00% in the second cut.(4) Difference of effect of irrigation application and folia spraying application on translocation characteristics of As in plant was found. Over 64% of As in plant was kept in root when extraneous As was applied through irrigation application. Over 83% of As in plant was kept in shoot under folia spraying application. The capability of transporting As from shoot to root after extraneous As absorbed in folia spraying was much greater than that of transporting As from root to shoot after extraneous As being absorbed in irrigation application. Translocation factor of the former was over 0.5 while the latter was below 0.1.(5) Safety evaluation for eating of vegetables treated with different concentration of extraneous As and Hg. As content in water spinach exceeded 0.5 mg/kg FW when concentration of extraneous As in hydroponics nutrient solution was over 0.4 mg/L. Hg content in radish root exceeded 0.01 mg/kg FW with small amplitude when concentration of extraneous Hg in hydroponics nutrient solution was 0.02 mg/L. As content in water spinach exceeded 0.25 mg/kg FW and 0.5 mg/kg FW when treatment concentration of extraneous As in irrigation application was over 10 mg/L and 20 mg/L respectively. As content in water spinach exceeded 0.25 mg/kg FW and 0.5 mg/kg FW when treatment concentration of extraneous As in folia spraying application was over 0.8 mg/L and 1.6 mg/L respectively. (6) Concentration thresholds of extraneous As under different treatments. Hg concentration threshold in hydroponics nutrient solution should be set at 0.025 mg/L in order to insure Hg content in radish within 0.01 mg/kg. As concentration threshold in hydroponics nutrient solution should be set at 0.094 mg/L and 0.255 mg/L in order to insure As content in water spinach within 0.2 mg/kg FW and 0.5 mg/kg FW respectively. As concentration threshold in irrigation treatment should be set at 16.071 mg/L in order to insure As content in water spinach within 0.5 mg/kg FW. As concentration threshold in folia spraying application should be set at 0.652 mg/L and 1.788 mg/L in order to insure As content in water spinach within 0.2 mg/kg FW and 0.5 mg/kg FW respectively.