Combined Effects Of Nitrogen Application And Pahs Pollution On Microbial Community And Function In Farmland Soil

Polycyclic aromatic hydrocarbons(PAHs)is a kind of global environmental pollutants with carcinogenicity,teratogenicity,and mutagenicity,which can exist in the soil for a long time and enter the human body through the food chain,they are mainly produced by incomplete combustion of organic substances such as petroleum and coal Nitrogen fertilizer is the most important guarantee for agricultural production.In the farmland soil of our country,both of them are often exist and have an effect on soil microorganism commonly.In addition,with the further study of PAHs,other heterocyclic heterocyclic aromatic hydrocarbons in the contaminated area are becoming more and more important.Among them,oxygen polycyclic aromatic hydrocarbons(quinones)are a kind of PAHs derivatives that may cause damage to cells and have cytotoxicity,immuno toxicity and carcinogenic effects.Adverse effects of quinones are often enriched in contaminated areas and their toxicity to eukaryotes has been confirmed.In this paper,benz[a]anthracene and urea were chosen as the representative of PAHs and nitrogen fertilizer.We set up soil microcosm experiments with combined treatments of urea and benz[a]anthracene.All the results of nitrate accumulation,soil pH and pollutant mineralization were perfomed,in addition,quantitative PCR and high-throughput sequencing methods were also applied to study bacterial community in all treatments;Benz[a]anthracene and Benz[a]anthracene-7,12-dione were chosen as the representative of PAHs and OPAHs.The ecotoxicity of benz[a]anthracene and Benz[a]anthracene-7,12-dione to nitrifying microorganism and the effect of soil bacterial community were compared under the soil microcosm experiments and the pure culture experiment of ammonia-oxidizing archaea.The main conclusions are as follows:(1)Nitrogen fertilizer can significantly stimulate nitrification activity in soil and reduce the pH value of soil,thus changing the main microbial composition in the soil,making the soil bacterial community change.In addition,nitrogen fertilizer will stimulate the growth of main ammnonia oxidizing microorganisms in sois with different pH values.(2)Comparing to pH value,benz[a]anthracene has little effect on microbial community structure.However,under the condition of long-term pollution,in neutral and acid soils,benz[a]anthracene both has the potential to inhibit soil nitrification,change soil microbial composition and structure,and this trend is more significant in acid soil.After short-term pollution,a considerable portion of benz[a]anthracene in the soil could be converted into Benz[a]anthracene-7,12-dione.Although ben2[a]anthracene and Benz[a]anthracene-7,12-dione failed to significantly change the soil bacterial community,the total number of bacteria in the soil had been significantly inhibited by both of themBenz[a]anthracene and Ben2[a]anthracene-7,12-dione have a significant inhibitory effect on some of 1.1b groips ammonia-oxidizing archaea,and the inhibition effect of Ben2(a]anthracene-7,12-dione is stronger than that of benz[a]anthracene.(3)In neutral soil,urea did not affect the mineralization of benz[a]anthracene,but benz[a]anthracene inhibited the growth of soil ammoxidation of Archaea and decreased the nitrification activity of soil.In acid soil,urea significantly stimulated the mineralization of benz[a]antbracene,meanwhile benz[a]anthracene dose not have significant inhibition of nitrifying microorganisms in soilThese results will help to elucidate the compound ecological effects of ammonium nitrogen and polycyclic aromatic hydrocarbons in farmland soil,and provide scientific basis for revealing the interaction between organic pollutants and nitrogen transformation,they also contribute to comprehensive treatment of soil polycyclic aromatic hydrocarbons.