Study On The Key Parameters Of Fusarium Sp.ZH-H2 To Degrade The HMW-PAHs Contaminated Soil

In the 2014 national soil pollution survey bulletin revealed that the point exceeding rate of polycyclic aromatic hydrocarbons(PAHs)had reached 1.4%,indicating that soil pollution was serious.High Molecular Weight PAHs(HMW-PAHs)with 4 or more rings have become a key restoration object of PAHs because they are more biotoxic.Microbioremediation is the main repair method of PAHs in the environment,but there are still some difficulties.At present,the removal rate of most strains in aged contaminated soil is only about 20%,which has become a technical difficulty for soil restoration.Our previous study had found a strain of high efficiency degradation of HMW-PAHs,named Fusarium sp.ZH-H2,which the monomers removal rate was 91.48% in an inorganic salt solution with a single carbon source of 5-6 ring HMW-PAHs.However,the degradation efficiency in aging contaminated soil is not high.Based on this,using the aged PAHs contaminated soil in typical coal mine area as the restoration object,the environmental conditions,nutrition condition and the number and time of the bacteria for the degradation of HMW-PAHs in the aging soil by Fusarium sp.ZH-H2 were optimized to determine the key technical parameters for the efficient degradation of HMW-PAHs in the aging soil.The main results were shown as follows:(1)The environmental factors such as temperature and humidity of HMW-PAHs degraded by Fusarium sp.ZH-H2 were optimized by orthogonal test of three factors and four levels.The results showed that suitable for ZH-H2 to degradate HMW-PAHs in soil environmental parameters as follows: temperature was 30~40 ?,humidity was 5~15%and the inoculation quantity was 1.0~2.0 g/kg,10 kinds of HMW-PAHs total removal rate was 22.89% ~ 25.44%.(2)Carbon source screening experiments were conducted to identify the types and doses of carbon sources that enhance the HMW-PAHs degradation by Fusarium sp.ZH-H2.Compared with ZH-H2,the two-factor treatment of exogenous carbon-ZH-H2 significantly promoted the total removal rate of HMW-PAHs in soil,especially the 2.5 g/kg dry soil humic acid-ZH-H2 treatment was the most significant,with an increase of 70.05%.The removal rate of single HMW-PAHs was also the highest in H+F3 treatment,which was29.58%~48.92%,with the best performance of the DbA.(3)Through the test of the nutrition parameters of carbon,nitrogen and phosphorus,proved the C-N-P optimization ratio of HMW-PAHs in the degradation of aging contaminated soil by Fusarium sp.ZH-H2,and the nutritional adjustment agent was formed.Different C-N-P treatments all promoted the total removal rate of HMW-PAHs by Fusarium sp.ZH-H2 in the soil,especially in the nutritive adjuvant Z of 50:1:0.5 treatment had the most significant effect,up to 37.15%.The removal rate of individual monomers also reached the highest value,between 30.39% and 54.63%,among which BaP showed the best performance.(4)Through multiple tests of bacteria at different times,the time and frequency of the inoculation of HMW-PAHs in the aging soil were defined.The results showed that the total removal rate of HMW-PAHs and monomer HMW-PAHs was the highest in H4 treatment,the total removal rate was 49.64%,the range of monomer removal rate was45.24%~59.73%,and BaP was the best.After the H4 treatment was completed,the total amount of soil PAHs and the environmental equivalence of benzo(a)pyrene satisfied with the local standard for ecological restoration of soil environment.(5)The dynamic characteristics of HMW-PAHs degradation by ZH-H2 were analyzed through degradation kinetics.For the same treatment,both single HMW-PAHs and the total amount of HMW-PAHs were the fastest degradation rate in 0~4 d.After that,the degradation rate gradually decreased and the reaction was slow.The degradation rate in the same time period was the fastest with 2.5 g/kg humic acid-ZH-H2 treatment.The self-degradation cycle of HMW-PAHs was greatly shortened,resulting in a total half-life of55.5 d,and the half-life of monomer was 49.2~69.3 d.(6)Through the degradation mechanism of lignin peroxidase,the mechanism of lignin peroxidase in high efficiency degradation of HMW-PAHs was clarified.The results showed that lignin peroxidase was a key enzyme in the process of degrading HMW-PAHs.To sum up,this study put forward the key parameters for the repair of the aging soil of HMW-PAHs by Fusarium sp.ZH-H2,which provide a technical reference for the modification of the contaminated soil.Parameters were recommended for: environmental conditions,temperature 30~40?,humidity of soil moisture content 5~15%.Carbon source and carbon nitrogen and phosphorus nutrition conditions,the carbon source was 2.5 g/kg humic acid,C:N:P was 50:1:0.5 nutritional adjustment agent Z.The dose and frequency of inoculation were 1g hyphae quantity of Fusarium sp.ZH-H2 for each kg of dry soil,each 7d was inoculated 1 times,4 times of inoculation,1 month of repair time,and the total amount of HMW-PAHs can be decreased by about 50%.The suitability of the study needed to be adjusted according to different soil pollution conditions,at the same time it needed to be further studied.