Distribution Of Glomalin-related Protein In Soils And Its Combination With Polycyclic Aromatic Hydrocarbons

Soil pollution is of wide concerns in china.Polycyclic aromatic hydrocarbons(PAHs)are a group of persistent organic pollutants with high toxicity in soils.PAHs in soils can enter into the food chain through soil-plant system,posing serious threats to human health and ecological safety.How to remediate the PAH-contaminated soils and reduce the PAH-risk of contaminated plants has become a worldwide environmental issue.It has been documented that inoculation of arbuscular mycorrhizal fungi(AMF)can reduce the PAH concentrations in plant shoots,and improve the rhizo-remediation efficiency of PAH-polluted soils.However,the involved mechanisms are still under elucidation.Glomalin-related soil protein(GRSP)is a class of glycoproteins produced by the AMF hyphae and then accumulated in soils.It has been reported that GRSP can improve soilpermeability and aggregate stability and promote plant growth.But the distribution of GRSP in soils and their interactions with PAHs are still unclear.To this end,understanding this issue will be of importance for revealing the influence of AMF on PAH-uptake by plant and PAH-degradation in soils.This work aimed to investigate the distribution of GRSP in soils;Clarify the influences of AMF-inoculated on plant growth and GRSP concentrations in PAH-contaminated soils,and reveal the combination of GRSP and phenanthrene as a representative PAH in aqueous solution.The main results are as follows:(1)The content and distribution of GRSP in soils under different land use types were investigated.Taking Nanjing yellow brown soil as example,It collected 5 species of land use(forest land,grassland,paddy soil,vegetable soil and tea soil)soil samples.It was found that the T-GRSP contents of all soil samples were ranged from 1.96 to 3.12 mg-g"1,accounting for 12.5%-29.0%of the SOC contents.The percentages of T-GRSP to SOC were decreased with the increase of SOC content.Compared to less anthropogenic disturbance of forest and grassland,three kinds of farming soils have low T-GRSP EE-GRSP content.The contents of T-GRSP decreased with increasing the soil depth,EE-GRSP did not show significant vertical distribution.The contents of T-GRSP were positively and significantly correlated with the SOC contents,while negatively with soil pH values.The contents of EE-GRSP were negatively and significantly correlated with the SOC contents.(2)The effect of AMF on plant growth and GRSP content in PAHs contaminated soil was studied.The AMF is Acaulospora scrobculata(A.s)?Glomus mosseae(Gm)?Glomus intraradices(G.i)?Glomus etunicatum(G.e)?Glomus constrictum(Gc),the test plant is Medicagosativa L.Inoculation of AMF promoted shoot and root growth of plant,but the biomass increasing degree by five AMF on plant is different.G.i treament have the best effect,A.s treament is the worst.With the prolongation of culture time,the content of EE-GRSP and T-GRSP in control and Gi treament increased with time.In G.i treatment,EE-GRSP and T-GRSP content is 4.13 and 2.13 mg·g-1,which were 3.93 and 4.65 times respectively in 30 d.After 90 d inoculated,the content of EE-GRSP and T-GRSP have the same trend showed G.i>Ge>Gm>Gc>A.s>Ck,EE-GRSP content of Gi treament is 1.33 mg·g-1,which was 1.7 times of the content of control group(0.79 mg·g-1),EE-GRSP content of A.s treament was the lowest(0.87 mg·g-1),T-GRSP content of Gi,Ge,G.m,Gc and A.s treament were 4.61,4.07,3.27,3.46 and 2.90 mg·g-1,the content of control treament was 2.30mg·g-1,T-GRSP content of Gi treament was 2 times of the control treament,the A.s treament were slightly higher than control treament.AMF-inoculated plant could increase the accumulation amount of phenanthrene,the accumulation amount of Gi treatment is higher than the other four treatments.AMF-inoculation reinforced the removal efficiency of PAHs in soils,the phenanthrene degradation rate of Gi and G.c treatment were more than 97%,A.s treatment has the lowest degradation rate.The content of T-GRSP?phenanthrene in plant and colonization rate were significant negative correlated with the residual phenanthrene content in soil.The contents of T-GRSP were positively correlated with the colonization rate,positively and significantly correlated with with soil pH values.(3)The combination reaction of GRSP and phenanthrene were primary evaluated.Combination isothermal curve of GRSP combining phenanthrene could be well described by Langmuir equation,the combination observed single molecule layer combination mode.The combining quantity increased with time,the combination of phenanthrene reached equilibrium basically in 24 h,the combining process conformed to the pseudo-second-order kinetics model.Equilibrium combining quantity is 44.26 ?g·mg-1.Solution pH has great influence on the effect of GRSP combined with the phenanthrene.At pH=4,combining quantity is the minimum;with decreasing of acidity,the combining quantity of phenanthrene were gradually increased,at pH=6,the combining quantity of phenanthrene reach to the maximum amount of 54.19 ?g·mg-1,when pH is more than 7,the combining quantity decreased gradually with alkaline enhancement.The higher the cation concentration,the greater impact to phenanthrene combining quantity.