Cultivating Of Pioneer Plant Peganum Harmala L.on Calcareous Soil And Its Remediation Mechanism For Heavy Metals

Peganum harmala L.is the pioneer plant on calcareous soil in the arid area of Northwest China,which not only has the biological characteristics of drought tolerance,cold tolerance and saine-alkali tolerance,but also has strong tolerance to heavy metals and high value in environmental ecology.This article was carried out based on the current situation of artificial breeding of the pioneer plant Peganum harmala L.and part of the farmland soil was seriously contaminated by heavy metals and it is difficult to continue to grow crops in the arid area of Northwest China.Taking heavy metals（Cd,Cu,Pb and Zn）and the pioneer plant Peganum harmala L.growing on the contaminated soil as the research focus,the artificial cultivation of Peganum harmala L.and its remediation mechanism on heavy metal contaminated soil were carry out that using a combination of pot experiment and field experiment.Meanwhile,the enrichment mechanism of Peganum harmala L.under different heavy metal contaminated levels was studied,to provide theoretical support for the remediation of heavy metal contaminated calcareous soil in the arid area of Northwest China.The main conclusions are as follows:（1）Seed soaking agents KMnO₄ can significantly enhance the germination and growth of Peganum harmala L.（P<0.05）,which was the most ideal seed soaking agent for growth and development of Peganum harmala L.selected in this experiment,and 5%KMnO₄ solution soaking seeds for 10 minutes was the best treatment effect.Single seed dressing agent New American Star,Gaoqiao,Diweidan,Lvheng No.1 and compound seed dressing agent calcium phosphate+fludioxonil,calcium phosphate+New American star can also significantly improve the germination of Peganum harmala L.seeds and the growth of seedlings（P<0.05）,and solved the problem of the root rot of Peganum harmala L.especially Peganum harmala L.seeds showed high germination rate and growth rate with New American Star treatment.In summary,KMnO₄ was the best seed soaking agent,and New American Star was the best seed dressing agent for growth and development of Peganum harmala L.（2）The pioneer plant Peganum harmala L.had high tolerance to heavy metals,which promoted the growth and development of Peganum harmala L.at low concentration,inhibited the growth and development of Peganum harmala L.at high concentration,and even caused death,especially Cd was the most important factor affecting growth and development of Peganum harmala L.Moreover,compared with the pot experiment,Peganum harmala L.grown under field conditions had higher tolerance to heavy metals.（3）The enrichment and absorption of heavy metals by Peganum harmala L.were different according to the heavy metal types,in which the ability of enrichment and migration of Cd was much higher than that of Cu,Pb and Zn,and the ability of absorption and enrichment of heavy metals by seedlings of Peganum harmala L.was stronger than that of mature plants.In the pot experiment,heavy metals were mainly concentrated in the roots of Peganum harmala L.The maximum enrichment of Cd,Cu,Pb and Zn reached 79.86,201.54,55.64 and 453.41 mg/kg,but the（Bioconcentration coefficient）BCF value of Cd was greater than 1,the mobility coefficient（TF）is less than 1,and the TF and BCF of Cu,Pb and Zn are all less than 1.However,in the field experiment,there was no significant difference in the enrichment capacity of heavy metals in the organs of Peganum harmala L.The maximum enrichment of Cd,Cu,Pb and Zn reached 34.96,36.47,33.66 and 84.77mg/kg,and the BCF and TF of Cd were basically greater than or close to 1,while the BCF and TF of Cu,Pb and Zn were basically less than or close to 1,indicating that Peganum harmala L.had a weak ability to migrate upwards of Cu,Pb and Zn,but Cd was a potential ecological safety element in contaminated area area.However,under pot experiment conditions and field conditions,there are obvious differences in the accumulation of four heavy metals in Peganum harmala,and the comprehensive analysis of the tolerance characteristics,enrichment and migration coefficients of Peganum harmala L.showed that it is not hyperaccumulator,but it had the potential for phytostabilization of heavy metals and can be used to remediate Cd,Cu,Pb and Zn contaminated soil,but due to its high accumulation and migration ability of Cd,measures such as regulating soil characteristics should be considered to prevent the huge risk caused by the activation of heavy metals in the future research.（4）Peganum harmala L.will change the soil physical and chemical properties during the growth process,thereby regulating the bioavailability of heavy metals in the soil,causing differences in the occurrence of heavy metals and the activation of Cd.Therefore,when using Peganum harmala L.to remediate heavy metal contaminated soil,the risk of heavy metal leaching should also be considered,and attention should be paid to the collection of seeds and fallen leaves of mature Peganum harmala L.to avoid secondary pollution.In summary,the seed dressing agent and the seed soaking agent had a positive effect on the artificial cultivation of Peganum harmala L.which can effectively improve the germination and growth of Peganum harmala L.and solve the problem of root rot,so that Peganum harmala L.can be planted in a large area.At the same time,Peganum harmala L.as a pioneer plant in the arid area of the Northwest China,had strong tolerance to heavy metals,and can be used as a potential plant for phytostabilization on calcareous soil in the arid area of the northwest,to remediate Cd,Cu,Pb and Zn contaminated soil.However,due to the high enrichment of Cd,future research should take into account the risk of Cd activation and achieve the triple benefits of ecological environment,society and economy by regulating the soil.