Research On The Purification Mechanism Of Coix Lacryma-jobi L. From Constructed Wetlands Acts On The Chromium-containing Domestic Sewage

Research on the purification mechanism of Coix Lacryma-jobi L. from constructed wetlands acts on the chromium-containing domestic sewage.In this study, the constructed wetlands system mode was simulated and the Coix Lacryma-jobi L. was set as the research object. The1/2Hoagland s nutrient solution and the domestic sewage were employed to culture the plant, with the chromium concentration of0,20,40mg/L respectively. The impact on the growth parameters of Coix Lacryma-jobi L. was studied by the determination of total chromium in different organs of Coix Lacryma-jobi L., even of the subcellular level, as well as the determination of different chemical forms of chromium content. The distribution features of different organs of the chromium in plant body, the subcellular level, as well as the different binding forms were analyzed. The effect of chromium on the ultra structure of Coix Lacryma-jobi L. root and root cross-section spectrum analysis were accomplished by transmission electron microscopy and scanning electron microscopy. The study can explore the purification and absorption mechanism of the Coix Lacryma-jobi L. acts on the Cr (VI) in constructed wetlands and provide a theoretical basis for the treatment of domestic sewage with constructed wetlands. The main results are as follows:(1)In this study, three chrome concentration of0,20,40mg/L were set, Growth parameters containing the root morphology index of Coix Lacryma-jobi L., the plant height, the stem diameter and the leaf area were negatively correlated with the increase of chromium concentration.(2)Effect on the Coix Lacryma-jobi L. ultra structure of Chromium:With the treatment of20mg/L Cr(VI), the double nuclear membrane of nucleus was mildly damaged, the chromatin was reduced and the mitochondrial double membrane structure was not obvious. As with the40mg/L treatment, the nuclear membrane was seriously damaged, the nucleolus became looser, the chromatin was condensated, the mitochondrial was swelling and the number of the crest was reduced.(3)The migration law of chromium in Coix Lacryma-jobi L. in vivo:The energy spectrum analysis showed that the chromium mainly accumulated in the epidermis, the outer cortex and the inner cortex in the roots, while hits the lowest content in central column. For different organ level, it was root> leaf> stem; for subcellular level, it was F1 (cell wall photo)> F3(soluble portion)> F2(control cells), indicating that the chromium ion binding in the cell wall would obviously reduce the poison of chromium on intracellular carried life activities of each cell, while it will protect cells by isolating the chromium ion entering into the intracellular in the vacuole.(4)Different chemical forms of chromium tests showed that the chromium of Coix Lacryma-jobi L. roots and the stem body was mainly in residual fraction, followed by deionized water extractable form, indicating that the existence of chromium forms of low bioavailability led to the detoxification mechanisms of the Coix Lacryma-jobi L. roots and stems. In Coix Lacryma-jobi L.’s leaves, the deionized water extractable chromium was with the largest proportion.