Fluoranthene In Shallow Groundwater System:Transport And Its Bioenhanced Remediation

Anthropic environmental pollution has become a global problem that comes into notice of people worldwide.Shallow groundwater system as a critical part of the earth environment has been contaminated at different level as well.Unlike surface water,pollution of the shallow groundwater system was hidden underground and much more difficult to be removed.Polycyclic aromatic hydrocarbons(PAHs)are ubiquitous and persistent in the environment with mutagenicity and carcinogenicity.The research about its fate/transport and remediation is meaningful for the environment protection.The sources,state,fate/transport and remediation methods for PAHs pollution have been summarized in this article.PAHs have been detected in 9.0-3344.7 ng/L levels and fluoranthene in ND-384.3 ng/L level in groundwater,northern Shenyang,because due to the agricultural activity and traffic.Based on the column simulation experiment,fluoranthene(20 ?g/g)in the polluted topsoil of the vadose zone will leach and transport downward with the infiltration water.Fluoranthene in this infiltration water can be constant in the concentration of 2.0 ?g/L.Medium in the vadose zone can absorb 60%-89% of fluoranthene from the infiltration water but 0.6 ?g/L fluoranthene remained still.In saturated condition,fluoranthene in the simulated groundwater at a concentration of 200 ?g/L reduced to 1.1 ?g/L after passing through the column.The calculated maximum concentration of fluoranthene in the soil of the study area may be 3.8 ?g/g based on the experiment.Fluoranthene in the soil can be decomposed via natural attenuation with the help of indigenous microorganisms in the soil.The remove rate was 97.7% for 200 ?g/g initial concentration after 64 days,about 2.2 ?g/(g·d).the composition and abundance of indigenous microorganisms were changed with the presence of fluoranthene,especially Gammaproteobacteria and Alphaproteobacteria.After cultivation in proper condition with the presence of fluoranthene,some bacteria can rebound,and the degradation of fluoranthene was accelerated slightly.In order to stimulate the decompose of fluoranthene in soil,a bacteria strain which has been identified as Brevundimonas with fluoranthene degradation capacity was isolated from the polluted soil.Its degradation rate for fluoranthene(500 ?g/L,1000 ?g/L,2000 ?g/L)can reach the level of 44%-56%,and the co-existent of cadmium(Cd)pose no significant influence.This bacteria strain can accelerate the degradation of fluoranthene when used as bio-enhancement in the contaminated soil and the reduction rate was 86.4% after 33 d.The addition of this bacteria strain was a benefit to the restoration of microbial diversity,inhibit the growth of unidentified_Bacteria as well.