Effects Of Nitrogenous Fertilizers On Accumulation Of Lead By Houttuynia Cordata Thunb Under Lead Stress

Phytoremediation has becoming an established technology for environmental clean-up and protection. Hyperaccumulator plants are potential tools to remove excessive metals in contaminated soils by continuous phytoextraction. Fertilization is one of the main measurements to enhance their ability to extract and accumulate metals from the metal contaminated soils. Houttuynia cordata Thunb was used as tested plant in this research. As an efficient operational routine technology, phytoextraction requires a better knowledge of the behaviors,such as Pb absorption, accumulation, distribution, and biomass of Houttuynia cordata Thunb as affected by N and Pb addition. To identify the responses of growth and Pb absorption or accumulation of Houttuynia cordata Thunb to N fertilization was also investigated by using a pot experiment with polluted soil. The results obtained are summarized as follows:1. To the growth and contamination symptom of Houttuynia cordata Thunb, (NH₄⁺)-N treatment is better than (NO₃^-)-N treatment in different concentration of Pb stress. From the Houttuynia cordata Thunb biomass and the low concentration stress of Pb, the stem weight and leaf weight in (NH₄⁺)-N treatment is higher than (NO₃^-)-N treatment with same nitrogen using level, but the root weight, plant height, and root length don't have changing rules. The biomass of (NH₄⁺)-N treatment is higher than that of (NO₃^-)-N treatment in the condition of high concentration stress of Pb and it indicates that ammonic fertilizer enhance the resistence of plant in Pb stress condition .2. The pH value of soil reached the highest when using 50mg/kg nitrogen fertilizer and fell when nitrogen fertilizer dosage rising.By useing (NH₄⁺)-N fertilizer , the pH value before soil potted is higher than it was potted; the gap of two values is increased with nitrogen dosage rising, the value of pH which decreased most is 0. 86 unit, the average decreasing value is 0. 55 unit. When used (NO₃^-)-N fertilizer, the pH value before soil potted is lower than it...