| Pb and Cd were the worst or most popular pollutants in soil, respectively. They could transfer in environment through dissolution, sedimentation and so on, due to food chain and biomagnifications, Pb and Cd could harm animals and human beings health. Currently, physical, chemical and ecological remediation procedures were three main methods of restoration and management of Pb and Cd polluted soils. Phytoremediation was used to remove heavy metals from the contaminated soils as an ecological technique, and the mechanism of phytoremediation was to use hyperaccumulators or tolerant plants to absorb, accumulate and translate heavy metals from the contaminated soils, achieving the purpose of alleviating the pollution of heavy metals. The phytoremediation technique had some advantages in comparison with the traditional remediation technologies, such as economical, non-pollution and high efficiency. Calendula officinalis L could tolerate low temperature to -9?, and it was not strict with illumination, water, fertilizer and grew quickly. The tolerance to heavy metals was the important characteristic. Because of these, it came to become topics in the study on soil respiration at home and aboard.The removal efficiency of Pb and Cd was not satisfactory through traditional phytoremediation technology, in order to improve the removal efficiency, this study used EDTA and tartaric acid to strengthen the Calendula officinalis L to restore combined pollution soil through pot experiment. The effect of different concentrations of heavy metals and soil moisture on the heavy metal accumulation, and the effect of EDTA and tartaric acid on heavy metal form, as well as the effect of single and combined use of chelants on enrichment characteristics, and to provide scientific basis for the chelants enhanced remediation of Pb/Cd combined pollution siol, as well as the feasibility of combined use of chelants. The main results are as follows:(1) Using (1+5) HClO4+HNO3 system digest the plants samples, under the optimum conditions, detection limits of Cd, Pb were 0.007,0.104 mg/L respectively, RSD was less than 4.75%, the rate of recovery was 94.33%?110.78% by AAS, this method had advantages of low detection limit, good accuracy and high precision, AAS could determine the content of heavy metal accurately and quickly.(2) The biomass of different parts of the plant decreased under Pb/Cd combined stress, but did not appear fatal toxic effects. As to Calendula officinalis L, the absorption of heavy metal increased with the concentration of heavy metals in soil, and always showed the heavy metal content underground part was larger than that of the ground part, and the coexisting elements in soil promoted the uptake of heavy metals. Therefore, Calendula officinalis L had strong resistance on Pb/Cd combined pollution, and had a certain potential for repair of combined contaminated soil.(3) Pb/Cd combined stress, the ground and underground parts dry biomass of Calendula officinalis L and soil water holding capacity presented inverted V curve, the emergence rate of all seedlings exceed 45%, the presence of Pb/Cd in soil could promote the growth of underground part of seedlings, and seedlings could improve pH, bulk density, organic matter, CEC and conductivity of the pollution Loess Under Pb/Cd single and combined pollution conditions (soil water holding capacity was water holding capacity from 65% to 70%(W2)). Too high or low soil water holding capacity were not conducive to the absorption and accumulation of heavy metals,65%?70%(W2) of water holding capacity was suitable for growth of Calendula officinalis L, and heavy metals accumulation of plants were the most. Under different soil water holding capacity, soil pH was significantly greater than that of foundation soil, soil pH and exchange and carbonate heavy metal had no significant correlation, the effect of soil water holding capacity on exchange and carbonate heavy metals concentration was not significant.(4)Pb and Cd contents of the ground and underground part were increased as the sampling time increased, EDTA, EDTA and tartaric acid combination increased the heavy metal of the ground and underground part significantly, the BCF (Pb/Cd) in different parts of Calendula officinalis L increased significantly. TF of Pb was greater than 1, but TF of Cd was less than 1 through adding EDTA. EDTA and tartaric acid combination could significantly improve the heavy metal accumulation of different parts in Calendula officinalis L, and the enhancement effect was the best when EDTA, tartaric acid concentration were 1.5mmol/kg,0.5mmol/kg respectively. Under combination treatment, the exchange and carbonate combination-Pb/Cd content was significantly increased in soil, the contents of heavy metals in Calendula officinalis Land exchange and carbonate combination-Pb/Cd had good correlation. XPS analysis found that C and O were two main elements of the ground and underground parts in plants, but O content of ground parts decreased after application of chelants, and its activity decreased, which was not conducive to the growth of ground parts. |
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