| In order to choose the plants that were hypertolerant to heavy metals and for the case of phytoremediation of soils that were polluted by heavy metals, the research was carried out by the methods of soil-planting and sand-planting in green-house. The study includes selecting the hypertolerant plants from 36 dominant species found in the vicinity of a Pb/Zn mine tailings pond , observing the ecophysiological response of the hyperaccumulators, improving-impact of hyperaccumulators on biosolds and examining the effect of nutrient elements(N P K) on the Lead uptake. The major results are as follows:1. Selecting the hypertolerant plants. The concentration of Lead treatment was 400mg.L"', and the screened standards are SPAD of plant leaves, the plant length and the content of Lead in plants. There are six plant varieties, which are Vetiveria zizanioides, Schizonepeta feniiifolio, Amaranthus tricolor, Xanthium sibiricum , Sophorajaponica, Bidens maximowiciziana. meet jointly to the criteria of SPAD/CK>0.9, plant length/CK > 1.00 and Lead content> 500mg/kg, and they are claimed hyperaccumulators.2. Ecophysiological response of the hyperaccumulators. The seven Lead levels were 0. 100. 200, 400, 800, 1000, 1500 mg.L"1, and remarked 0. 1, 2. 3, 4, 5, 6 respectively. With the increase of Lead level, the changing trend of SPAD and soluble sugar content and the activity of nitric acid reverting enzyme(NR) had appeared the same direction, which ascended first and then fell. On one hand, the growth of SPAD and the activity of NR had no significant difference at 5% level . The maximum of soluble sugar content of Amaranthus tricolor and Bidens maximowiciziana showed significant difference compared with the contrcHed samples. On the other, the decrease of SPAD and the soluble sugar content and the activity of NR of the hyperaccumulators appeared significant difference. Additionally, the ABA content of hyperaccumulators had risen dramatically with the growth of Lead concentration, and the increase of ABA content was sig The results showed that the Lead contamination had negative effect even on the hyperaccumulators.3. Lead uptake "'nd tolerance of hyperaccumulators. The sequence of Lead content in each hyperaccumulator was Bidens maximowiciziana>Amaranthus tricolor>Sophora japonica>Xanthium sibiricum>Schizonepeta fenuifolio> Vetiveria zizanioides in this study. On one hand, Bidens maximowiciziana and Amaranthus tricolor could transport the iiiost of the Lead from roots to the above-ground parts, and the total heavy metaltranslocated (TMT) of Bidens maximowiciziana and Amaranthus tricolor rose to the 11.29mg and 9.17mg in 100 plants. On the other, the root of Bidens maximowiciziana was not sensitive to high Lead level, and the maximum of root tolerance index (RTI) was 1.66. Additionally, the six plant varieties critical contents, which are both low limit and high limit, were drafted in this study.4. Response of hyperaccumulators on biosolids. Biosolids can stimulate the growth of hyperaccumulators, and increase the plant biomass. Especially, the biomass of Thlaspi goesingense and Bidens maximowiciziana cultivated in biosolids had risen significantly compared with the CK. Thlaspi goesingense can accumulate Cu, Zn, and Pb, and Bidens maximowiciziana uptook Pb and Cd significantly. The root of each hyperaccumulators had activated compact on heavy metals. Particularly, the activated ratios ( 1) of Cu and Zn in Thlaspi goesingense were the highest, which were 2.74% and 3.56%, the activated ratios ( n) of Cd in Amaranthus tricolor was the highest, which is 2.17%, but the heavy metals activated ratios of other plants were around 1.1%.5. Effect of nutrient elements on Lead uptake of hyperaccumulators. A little amount Nitrogen and Potassium can accelerate the growth of SPAD and plant dry weights, advance the Lead uptake of hyperaccumulators. But with the increasing of Nitrogon and Potassium concentration, the Lead uptake of plants droped, and SPAD and dry weights rose constantl...
|
PDF Full Text Request