Microbiological diversity and functionality of a chronically hydrocarbon contaminated soil post chemistry oxidation

MEDINA R; PEDRO DAVID GARA; ROSSO J. A.; VIERA M.; DEL PANNO M.T.

Cordoba

Congreso; XI Congreso Argentino de Microbiología General. SAMIGE; 2015

In situ chemical oxidation (ISCO) is increasingly usedfor the remediation of soil containing organic contaminants such as polycyclicaromatic hydrocarbons (PAH). However, the impact on the soil microbialcommunity has not beenthoroughly elucidated. The aim of thestudy was to analyze the effect of the ammonium persulfate application followedby a bioremediation process on the matrix, microbialcommunity and the PAH removal of the soil. Chronically contaminated soil (S) was collected from a petrochemical area (214 ppm PAH). Ammonium persulfate (PS) wassprayed as aqueous solution on contaminated soil by three additions (1% wt/wt)every two days and incubated at 30°C(SOx).S and SOx were further incubated at 25°C, 25% moisture content, mixedand monitored for 28 days. These microcosms were named SB and SOxBrespectively. The PAH concentrations weredetermined by GC-FID. NoPAH elimination was detected in SB. A significant elimination (35%) wasobserved in SOx while no additional decrease was detected SOxB.Alkaline extraction was performed to obtain anaqueous solution of natural organic matter of the soil. The Total OrganicCarbon contents (TOC, TOC-5000 Shimadzu) and the Fluorescence ExcitationEmission Matrixes (FEEM, Perkin-Elmer LS-50B) were determined for Sand SOx.FEEM of S presents two zones of emission. The zone on lexc ~ 320 nm and lem ~ 440 nm could be assigned to thepresence of PAH. These emissions were absent in SOx in line with the PAHelimination, and a significant increment on TOCvalues was also detected. A significant decrease in the microbial counts wasobserved in SOx. The subsequent bioremediation only increased theheterotrophic bacterial population which suggested that the available organiccarbon allowed the growth of this population. To evaluate the microbialactivity, four enzymes lipase, aril sulphatase, urease and protease wereanalyzed. All of them were slightly expressed in S microcosms and onlylipase activity was significantly increased in SOx. Seed germinationtest using Lactuca Sativa on water extracts was performed to evaluatethe soil toxicity. The toxicity detected in S was exacerbated in SOx and it was notreversed in SOxB. The dynamics of the bacterial communitystructure, analyzed by 16S rRNA PCR DGGE, evidenced a great change due to theoxidation. Theclustering among the S and SOxB profile bandssuggested the tendency of SOxB to recover the originalstructure. The pyrosequence analysis showedthat members of actinobacteria, bacilli and acidimicrobiia classes were thepredominant populations in SOx. Members of the actinobacteriabecame the dominant population in SOxB. This group was considered ask-strategist microorganisms and a major component in the later stages ofsuccessions in bioremediated soils. The initial PAH elimination provoked by PSwas not followed by an additional elimination under bioremediation condition.However, a microbial succession of generalist populations was observed.