| Due to its highly toxic, deformed, carcinogenic and mutagenic properties to organisms, arsenic(As) has long been one of the elements of public concern. With the development of phytoremediation and the new findings of As hyperaccumulators, such as Pteris vittata, Pityrogramma calomelanos, P. cretica, P. cretica var. nervosa and so on, remediating soil and water contaminated with As using this cost-effective and environmentally sound method has become possible. Presently,p. vittata is widely used as an important material in phytoremediation research of As-contaminated soil and water.they mainly launch to repair the soil and water contaminated with As using plants taken p. vittata as experimental material both domestic and foreign.It is very nice material with different metal-accumulating characteristics in species under the same genus. However,many researchers used P. vittata as experimental material solely at present, and some use plants belonging to different families and genera. In addition, there is little information available on how the photosynthesis physiology change in different plants under As stress.In present study, firstly, a field survey were conducted to research the characters of soil-plant system at 7 sampling sites in As mine area in Nanhua county, Yunnan province. Secondly, pot and hydroponic trials were developed under laboratory conditions in which 4 species[P. vittata,P. cretica var. nervosa(As hyperaccumulators) and P. semipinnata, P. ensiformis(nonhyperaccumulators)] were cultivated for 60 days on As-amended soils with 0, 50, 100 200, 2204±169 mg As kg-1(collected in As mine area) and 25 days in As-amended aqueous with 0, 5, 25, 50 mg As L-1,respectively. Thirdly, concentrations of As and soil physico-chemical properties were determined. The chloroplasts ultrastructure were observed in different time(15d, 30d, 45d and 60d) by transmission electron microscope(TEM). At the same time, time-cause effect of Chlorophyll content were determined(pot trials:10d, 20d. 30d, 40d, 50d, 60d; hydroponic trials: 5d,10d, 15d, 20d, 25d). At last, effects of induced phytoremediation on As accumulation(appended P, CDTA and acid) before 15d of harvest were examined.The results indicated as follows:1. The As mine area were polluted by As with different degree(concentration of total As was 58-603mg kg-1 upper soil, 197-645mg kg-1 nether soil) >40 mg kg-1,Surpass the third level of GB15618-1995). The fluctuation of soil physico-chemical properties in the As mine area is obvious, such as pH(range4.85-8.59), , contents of organic matter(OM) 4.41-57.57g kg-1, total phosphorus(TP) 2.01-55.62g kg-1 and total nitrogen(TN) 0.03-0.55 g kg-1. At the As control site pH ranged from 5.35 to 5.99, contents of OM from 1.81 to 16.85, TP from 2.87 to 11.74 and TN from 0.07 to 0.63. concentration of As is the highest at S4. The translocation factor (TF) was >1(1.03-5.45), especially P. vittata(2.40-5.45), except for Ageratina adenophora(0.87).2. Among soil enzymes activities(catalase, urease, protease, phenol oxidase, amylase and invertase) of top(0-15cm) and below(15-30cm) soils at seven sites, there was no significant difference in the activities of catalase and urease (P>0.05). Protease was also like this except S2, below of S1 & S2 and top of S1 & S4, S3 & S4. Activities of phenol oxidase was insignificant at the same site. Amylase and invertase exist significant difference below sites and S1 & S6. At the same time, total As and available As(top soil)restrain soil enzymes activities, but available As(blow soil) activise soil enzymes activities. In conclusion, (1). urease and protease inexist relativity to contents of As in soil abviously. (2). OM promoted soil enzymes activities. (3). among physico-chemical properties, concents of As, OM osculates and activities soil enzymes activities. (3). OM and invertase activity represent all of transformation information at 7 sites with 12 indexes.[Note:S1,S2,S3,S4- rhizosphere soils under Quercus pannosa,P.vittata grown under Quercus pannosa, p.vittata grown under Ageratina adenophora and P.vittata, P.vittata grown on gangue, respectively]3. Under pot experiment, chlorophyll a, b and carotenoid in P. nervosa and P. ensiformis reduced under 100 mg As kg-1 treatment with control obviously. And not only different plants(P.nervosa and P. ensiformis) but also the same one with time-cause, chlorophyll a, b and Carotenoid also reduced under 25 mg As L-1 hydroponic conditions with control obviously.4. Chloroplasts ultrastructure were observed by TEM using P. nervosa and P. ensiformis under 0 and 100 mg As kg-1 treatment. The shape and the chloroplast structure were normal, their granum thylakoids arranges neatly and the chloroplast becomes the ellipse under control. But in P. nervosa, chloroplast structures were destroyed in which starches firstly increased but then reduced. Fats increase at all times, membrane system shattered, and the damage lightened under 100 mg As kg-1 treatment. In P. ensiformis, there was significant difference, chloroplast structures were destroyed heavily in which starches firstly increased and then reduced. Fats increase at all times, membrane ruptured, the contents seeps out, thylakoid piles up to be few and sparsely, and chloroplast distorted.5. Among P. vittata, P. nervosa, P. semipinnata and P. ensiformis, CDTA and P-increased the As uptake of P. vittata and P. ensiformis before 15d of harvest, respectively. |
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