| We are facing with the great pressure of heavy metals pollutions to the soil, and food safety is a crucial problem that caused serious concern from all sections. The study through pot cultivation, choose Cd and Pb, potherb mustard was used as a test material, discussed the relationship of absorptive character and heavy metals pollution from biology and environmental toxicology. The study took some treatments in order to discuss how to restrain heavy metals transfer to the plant from soil and keep a definite store of output maintimes. This could direct the environmental quality and offer basis for food safety.The study contains four sections: (1) growth-impact and toxic-symptom of single and compound pollution of Cd and Pb in soil of potherb mustard; (2) effects of different fertilizations on biochemical and psychotic response of potherb mustard; (3) effects of different fertilizations on photosynthetic characteristics of potherb mustard ; (4) effects of different fertilizations on biological effectiveness of heavy metals in soil.Through pot cultivation of different sewage irrigation, we know that potherb mustard would be turning color in nerve and drying out and without green in Cd-contaminated soil. And in the Pb-contaminated soil, the potherb mustard would be wilt and lost greenand leaves appeared reddish-brown patchs and new leaavs curls. That low concentration of Cd and Pb promoted growth of vegetables, and the potherb mustard woule be more poisoned when the concentration of heavy metals over the critical concentrations. The simulated test of compound contamination with Cd and Pb showed that, at a certain concentration, Cd inhibited potherb mustards to absorb Pb, and Pb promoted them to absorb Cd.On Cd-contaminated soil the use of organic fertilizer could stimulate the output, the chlorophyll content and protein content of potherb mustard. The use of lemon acid could stimulate the root activity of potherb mustard significance, and the use of lemon acid and phosphate could maintain the output high and reduce heavy metals of plants. On Pb-contaminated soil, the use of organic fertilizer could stimulate the output, the chlorophyll content, the protein content and activity of enzyme of potherb mustard. The heavy metals can restrain the root activity of plants, and the effect of Pb is more than Cd. The organic fertilizer could stimulate the output of plants and the effect of organic fertilizer related of its quantity and usage mode, but the protein content related to the usage mode of organic fertilizer only. On compound contamination soil, the use of lemon acid could stimulate the protein content and root activity of potherb mustard significance. The use of phosphate could reduce Pb content of potherb mustard and the effect of compound contamination to the root activity is more than single contamination.Different fertilizations could stimulate the adaptation to light of the plant. All the fertilizations could enhance the net photosynthetic rate (P_n) , light saturation point (LSP) and apparent quantum yield (AQY) and reduce the light compensation point (LCP) of the plant. The fertilizations of organic could maintain a higher P_n, LSP and AQY, and related to the method of the usage. The F_v/F_m of all the fertilizations was higher than 0.8, and this showed that the plants were not restrained by light. On Cd-contaminated soil the use of phosphate made the P_n and LSP largest. On Pb-contaminated soil the use of phosphate made the P_n , LSP and AQY largest. And the use of organic fertilizer made the PS II largest.The results showed that the use of organic fertilizer could enhance the risk of absorption of heavymetal. The use of lemon acid could reduce the content of heavy metals in the plant, and reduce the content of bioavailable Pb, but have no effect on the content of bioavailable Cd; so we should select a right kind of heavy metal when repair the soil with lemon acid. Phosphate fertilization could decrease the bioavailability of Pb and Cd very well, it made the heavy metals turn EXC to RES. |
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