The Effects Of Plants, Carbon Sources And Bacteria On The Remedation Of PAHs Contaminated Soils And Water

Polycyclic aromatic hydrocarbons (PAHs) are widespread hydrophobic and persistent organic pollutants in environment, which can be detrimental to human beings through biomagnification. The aim of this study was to evaluate the role of plants, additional nutrients and bacterial agents on PAHs polluted media including soils and water. Based on the role of phytoremediation in degrading PAHs in long-term PAHs-aged soils and newly polluted soils, the interaction with the PAHs and carbon sources was studied by using FTIR technology. Furthermore, in the present study we tried to identify some highly efficient PAHs degrading bacteria in order to restore the PAHs polluted soils in the field.1. Four plants (Tall Fescue,Lucerne. Ryegrass,White Clover) were growed for 120 days to remedy the newly and aged PAHs polluted soils. Results showed that in PAHs-aged soils, plants increased the availibility of bound PAHs with the order of Tall Fescue> Ryegrass> Lucerne> White Clover. However, all plants facilitated PAHs dissipation for newly polluted soils with the order of Tall Fescue> Lucerne> Ryegrass> White Clover. It was also found that both newly and aged soils without plants have the capacity to dissipate PAHs to some extend.Further investigations were conducted to identify the soil microbial community changes by using phospholipid fatty acids technique (PLFAs). The soil microbes were shifted from gram-negative bacteria towards fungi, gram-positive bacteria and actinomycetes.2. Two types of carbon sources (Rhizosphere Dissolved Organic Matter, RDOM; artificial root exudates, AREs) were used to stimulate the microbes to utilize PAHs. Results demonstarted that addition of both carbon sources at the levels ranging from 20 to 50mg C L-1 promoted the biodegrdation of PAHs in soils. Further study showed that both above and below 1000Da fractions of AREs brought a rapid change in the PAHs degradation period as compared to the whole AREs, but no obvious degradation differences were found between the above and below 1000Da fractions of AREs. FTIR results indicated that RDOM and its composition with different molecular weight were mainly composed of carbohydrates, aliphatic compounds, hydroxyl compounds and aromatic compounds. While RDOM composition with different polarity were different from that with different molecular weight. Based on the FTIR figures of RDOM with and without addition of PAHs, we found that different functional groups in RDOM fractions took different effects in the combination with PAHs, which would certainly cause different behavior of PAHs in soils.3. The single and double carrier of PAHs degradation bacteria were developed by using black carbon and humic acid as carriers. Results showed that both types of bacteria carrier largely promoted the degradation of PAHs with a dissipation rate of 98% during 6-day period.