Short-term Response Of Polycyclic Aromatic Hydrocarbons To Rhizosphere Degradation Of Artemisia Boratalensis

Plant rhizosphere degradate soil contaminants are a very important part of phytoremediation and one of the important research journals in soil science,botany,toxic ecology and environmental science.Especially in the increasing nitrogen deposition environment,a small amount of nitrogen deposition in the short term to improve ecosystem productivity,the accumulation of more biomass,and excessive nitrogen deposition will lead to plant nutrient excess,soil acidification,affecting ecosystem stability and so on.So,in the arid zone,whether the increase in nitrogen deposition will affect the degradation of polycyclic aromatic hydrocarbons（PAHs）in the pastures of the petrochemical plant,and if there is degradation,then what is the degradation mechanism and what changes have occurred with the increase of nitrogen deposition? Are still should to be studied.This has some reference value for soil pollution remediation and ecological environment management and construction.The experiment was carried out by simulating the experiment of nitrogen deposition around the petrochemical plant in Dushanzi district,Xinjiang.According to the results showed that the soil environment,enzyme activity and microbial functional diversity of rhizosphere soil were screened by three kinds of herbaceous plants,such as Artemisia boratalensis,Eremopyrum triticeum and Tetracme quadricornis,then select the Artemisia boratalensis as the main object of study.N0（0 kg N/hm²·a）,N1（10 kg N/hm²·a）,N2（30 kg N/hm²·a）,N3（90 kg N/hm²·a）and CK（without any treatment）were treated in a total of five treatments.Nitrogen was added every other month.From May 25 th,2016 to August 19 th,2016,soil samples before and after nitrogen application to analyze and compare.Get the following results:（1）The microbial metabolic activity（AWCD）of rhizosphere soil was different from that of non-rhizosphere soils in different plant rhizosphere soils.The soil microbial AWCD,Simpson,Shannon and Mc Intosh were all higher than those of non-rhizosphere soils.Rhizosphere soil microbes were sensitive to sugars,lipids,acids and amines,and non-rhizosphere soil microbes were sensitive to acids,amino acids and carbohydrate carbon source material,rhizosphere soil microbial carbon source utilization width is greater.The results showed that the presence of vegetation could promote soil enzyme activity,improve soil microbial metabolic activity and functional diversity,and the better soil condition,the more favorable to adapt to environmental changes.The activities of dehydrogenase,catalase and urease in the rhizosphere and non-rhizosphere soils of the three plants were the highest in the rhizosphere and non-rhizosphere soil of Artemisia boratalensis,and the three rhizosphere soil enzyme activity was higher than that of non-rhizosphere soil.The results showed that the main factors affecting soil microbial functional diversity were pH,soil organic matter（SOM）,available phosphorus（AP）and nitrate nitrogen（NO₃^--N）.PAHs had positive effects on soil electrical conductance（EC）,soil moisture and pH in rhizosphere soils.In the soil,the increase of ammonium nitrogen（NH₄⁺-N）and AP can enhance the removal effect of PAHs.（2）Increased nitrogen deposition in the short term（3 months）enhanced the activity of dehydrogenase,catalase and urease in rhizosphere soil of Artemisia boratalensis,and improved AWCD,Shannon and Mc Intosh in rhizosphere soil,while avoiding（Naphthalene）and 4 ring（flexion）polycyclic aromatic hydrocarbons in the soil can be reduced,and there is a positive effect in the removal effect of total polycyclic aromatic hydrocarbons.The addition of 30 kg N/hm²·a in the short-term and different nitrogen treatments had a good effect on the enzyme activity and microbial functional diversity in rhizosphere soil of Artemisia boratalensis,especially in the removal of PAHs,The contents of PAHs were significantly decreased（P <0.05）.The total contents of PAHs were significantly decreased（P <0.05）.The soil microbes of rhizosphere soil of Artemisia boratalensis were the maximum strength of the use in the nitrogen addition of 30 kg N/hm²·a for the six carbon source materials.CK,N1,N2 and N3 treatment of the main use of carbon source material for the lipid,the use of acid substances to minimize the intensity.The ability of the rhizosphere soil microbes in the nitrogen-free and non-water-treated groups to use the carbon source was weak,the results showed that the increase of nitrogen deposition could significantly change the soil microbial functional diversity.Based on the principal component analysis,the acids,sugars,amino acidsacidity and lipids are the main sensitive carbon sources in the rhizosphere soil microbial community in different environment of nitrogen deposition.（3）The correlation analysis between soil environmental factors with enzymes,microbes and PAHs in the rhizosphere and non-rhizosphere soils of Artemisia boratalensis was studied.The results showed that soil moisture,SOM,AP,pH,NH₄⁺-N and NO₃^--N had a significant effect on the content of PAHs in the soil.Compared with the pre-nitrogen application,the addition of nutrient substances could promote the degradation of PAHs in the rhizosphere.The contents of AP,NH₄⁺-N and NO₃^--N have some help to the removal of PAHs.The addition of NO₃^--N can also promote the removal of PAHs compared with that before nitrogen treatment.In general,the deposition of NH₄⁺-N and NO₃^--N in the atmosphere can effectively promote the removal of PAHs in rhizosphere and non-rhizosphere soil in the short term.