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Plant-microbial Remediation for Crude Oil Contaminated Soil under Different Salt Content

Author: MaChuanZuo
Tutor: WangZhiRong
School: Tianjin University of Technology
Course: Environmental Science
Keywords: Plant-microbial remediation exogenous flora DHA PCR-DGGE
CLC: X172
Type: Master's thesis
Year: 2011
Downloads: 266
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Abstract

With increased yield and consumption of crude oil, it is inevitable to enter soil environment and to contaminate the soil. Once crude oil mixing with soil, the physical and chemical characters of soil will be changed and permeability of the soil voids will be blocked. Meanwhile, as a complex compound, aromatic compounds in the crude oil take a large proportion, especially for PAHs, which can cause carcinogenic, teratogenic and mutagenic, all of these will run a high risk to animals, plants and microbes in the soil.Plant-microbial remediation as a fast, efficient and non-secondary pollution treatment has been applied remediation of crude oil contaminated soil commonly. Based on the salinity character of soil in Tianjin, crude oil contaminated soil remediation under high salt concentration by using plant-microbial method can provide theories for restoring in-suit soil directly. In this test, three salt contents, including 2493mg/kg, 3690mg/kg and 4666.67mg/kg, three crude oil contents, including 5000 mg/kg, 10000 mg/kg and 15000mg/kg are designed to study crude oil degradation rate in the pot experiments by applying plant-microbial combined method, the main conclusions are listed:Through comparison of non-root group, plant group and plant-microbe group, it shows that the degradation rate under 5000mg/kg crude oil is plant group<non-root group<plant-microbe group; the degradation rate under 10000mg/kg and 15000mg/kg crude oil is plant group≈non-root group<plant-microbe group.When considering the effect of plant in the whole process of remediation, the time of reaching peak point of the total microbial amount in the soil is delayed comparing with non-root group. Meanwhile, total microbial amount in the soil is higher than that of non-root group. Also, under high salt condition, microbial amount is inhibited, the same results can be found when measuring DHA in the different salt and oil contents.Ten sorts of bacteria in the pot experiment are identified through morphological structure of microbe, including Bacillus(12.8%), Sporolactobacillus(38.5%), Staphylococcus(10.3%), Aerococcus(5.1%), Arthrobacter (12.8%), Halobacillus-spring(5.1%), Lactabacillus(2.6%), Clostridium(2.6%), Strptococcus(2.6%) and Micrococcus(5.1%).Physiological indicators of plant describe that germination rate, height, biomass and root length of plant are inhibited under the condition of 4666.67mg/kg salt content. Meanwhile, comparing with root activity of plant group, the root activity under the effect of exogenous microbial flora is much higher than plant group.The main conclusions in the crude oil degradation under high salt concentration (7000mg/L) by bacteria flora and fungus flora are:The similar discipline of degradation rate of crude oil can be found in both bacteria flora and fungus flora: 30000mg/L>10000mg/L>50000mg/L. However, the final degradation rate of crude oil in the fungus flora is lower than that of in the bacteria flora. The same conclusions of DHA and total microbial amount in the flask are resulted.It is worth to point out that pH in both bacteria flora and fungus flora has changed greatly from neutral/acidic to alkaline. However, an exact explanation to this phenomenon cannot be concluded now.Through PCR-DGGE analysis, the main strain is increased as crude oil content increasement and the strength of these main strains is increased as well. Meanwhile, the structure and complex of bacteria and fungus flora become more and more diverse as crude oil increasement by observing other stains in each flask system.

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