Study On Strengthening Technology-assisted Phytoremediation Of As-contaminated Soils

Arsenic is a kind of metal which is widely distributed in nature and high toxic. Soil arsenic contamination not only affects on crop, but also serious threat human health and ecological safety.At present, the situation of soil arsenic contamination is more and more serious due to the excessive exploiting, producing and use of arsenical compround. As a result, arsenic pollution has become the focus of environmental science. However, traditional remediations of contaminated soil are difficult and costly due to the characters of arsenic contamination of soil was huge in quantity and wide in spread, In recent years, phytoremediation of heavy metal contaminated soil, has become a hot spot of arsenic contaminated soil remediation. An experiment was conducted to investigate the cultivation techniques of Pteris vittata L. and affect to remediation of the low arsenic contaminated soils. Study to strengthen measures on the general plant at the same time, corn is a good candidate for phytoremediation of arsenic-contaminated soils. The main results are as follows:Through pot experiment in greenhouse, we have studied the impacts on Pteris vittata L spores reproduction speed by different treatments. The results show that the chemical treatment can accelerated germination speed, reduced germination time. The growth of Pteris vittata L prothallus stage is accelerated after spraying improved Hogland nutrient solution, which speed up the prothallus of Pteris vittata L on the growth.The research on the effects of inoculation of arbuscular mycorrhizal fungus (AM) and fertilizztion on the growth and the capability of As enrichment of Pteris vittata L is carried out at the same time. The results showed that the need of fertilizer is low during prophase of Pteris vittata L and Pteris vittata L inoculation with AM has significantly higher biomass than control, and the promoting effect on Pteris vittata L by arbuscular mycorrhizal fungus (AM) could be seen after 120 days.The experiment data showed that inoculation with AM can significantly enhance the biomass of Pteris vittata L and adding proper content of N,P,K,Ca fertilizer can also promote the growth of Pteris vittata L seedling. It was also found that compared with other treatments, inoculation with AM and adding Ca and organic could significantly enhance the content of As in Pteris vittata L. We can conciude that inoculation with AM and adding Ca and organic can promote the enrichment of As in Pteris vittata L.The treatments of inoculation of AM, inoculation of AM and adding organic, inoculation of AM and adding Ca can all increase pH of soil significantly while the pH of soil adding NPK fertilizers were lower than the control significantly. In addition, mycorrhizal infection rate of treatments which adding NPK fertilizers also were lower than other treatments significantly,we can conclude that fertilization has strong impact on AM infection rate. The treatments of inoculation of AM, inoculation of AM and adding organic, inoculation of AM and adding Ca have higher soil dehydrogenase activity than other treatments remarkably, which may be related to the decreasing pH by fertilizer.After planting Pteris vittata L for 60 days, the treatments of inoculation of AM has higher soil phosphatase activity than other treatments remarkably. The treatments of inoculation of AM and adding organic has obviously higher soil phosphatase activity than inoculation of AM and adding NPK fertilizer which has antagonistic effect in soil phosphatase activity.Overall, soil phosphatase activity has been improved after planting for 180 days.In spring, when the seedlings of Pteris vittata L grow about 10 cm, we transplant them in the field. According to the growth characteristics of Pteris vittata L, shading net should be used in hot summer. Pteris vittata L has strict requirement of soil and atmosphere humidity and more watering and spraying is necessary during summer.While in autumn it would be better have less watering to keep soil wetness. Pteris vittata L is sensitive to the low temperature, so it should be coverd with thin film in field for heat preservation take the cold winter of Jiangsu province into consideration. Cutting out withered and aged leaves before tender leaves come out in spring would promote the budding of Pteris vittata L.Through above management measures, the Pteris vittata L grow flourish. The per shoot dry weight is 32.33 gram. The per weight of root is 56.79 gram, and total dry weight is 89.12 gram, the yield of a unit area is 6 ton/hm~2. The management measures, according to the preference of Pteris vittata L, made Pteris vittata L grow well, which offer technical reserves for the remediation of As-contaminated soil by Pteris vittata L in Jiangsu Province.In addition, a field experiment was conducted to investigate the effects of inoculation of arbuscular mycorrhizal fungus (AM) or/and earthworms on phytoremediation efficiency of the low-arsenic contaminated soil by maize. The results showed that inoculation with AM or earthworms alone could significantly increase mycorrhizal infection of maize roots. And inoculation of AM and earthworms in combination showed the mycorrhizal infection was much higher than inoculation of AM or earthworms alone; While inoculating earthworms alone or combination with AM fungi, they could increase biomass of maize shoot and root,and also could significantly enhance the content of As involved in well-crystallized orhydrous oxides of ferrum and aluminum. It was also found that compared with the control treatment, the phosphatase activity in soils of AM fungi in combination with earthworms were significantly increased.Inoculation with AM fungi or earthworms alone could greatly enhance the phytoremediation efficiency of As-contaminated soil, but inoculation of earthworms and AM fungi in combination showed the highest remediation efficiency. After 3 years, the content of soil arsenic decrease to 19.70 mg/kg in the control, which is significantly lower than pre-implantation,the efficiency of arsenic is 36.9%. The content of soil arsenic inoculation with AM or earthworms alone could significantly lower than the control, the efficiency is 50.0% and 55.4% respectively. The content of soil arsenic, which inoculation of earthworms and AM fungi in combination is the lowest, is significantly lower than inoculation with AM or earthworms alone. The efficiency is 67.6%by inoculation of earthworms and AM fungi in combination, increase about 30.8% compared with the control. Inoculation of AM and earthworms could promote the phytoremediation efficiency of As-contaminated soil when maize was planted.