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Isotope Geochemistry of Biodegradation Processes in a Petroleum Hydrocarbon-Contaminated Aquifer

Author: LvHang
Tutor: SuXiaoSi
School: Jilin University
Course: Groundwater Science and Engineering
Keywords: Groundwater Petroleum hydrocarbons Biodegradable Stable isotope Factor Analysis
CLC: P641.3
Type: Master's thesis
Year: 2011
Downloads: 225
Quote: 1
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Abstract

An oilfield in mining plant wells rakeback accident caused pollution of shallow groundwater, groundwater drinking water safety of local residents directly affect the governance of groundwater in the region, there is an urgent need to select the appropriate repair method. In the number of repair methods for monitoring natural attenuation remediation technology because of its use of natural attenuation capacity, does not produce secondary pollutants, minimal degree of interference with the ecological environment and land use become the first choice. The technology includes advection, dispersion, volatilization, adsorption and biodegradation process, only biodegradation by destroying contaminants structure, its complete eradication. Thus biodegradation occurrence and degree of response direct impact on the natural attenuation of the effect of repair technology, the study of the process is to evaluate the natural attenuation of the technical feasibility and appropriateness of the key. In this paper, the oil-contaminated sites, for example, on the basis of full analysis of site hydrogeological conditions, groundwater petroleum hydrocarbon pollution characteristics, site groundwater and soil water chemistry and stable carbon and sulfur isotope data distribution laws, and factor analysis, cluster analysis, isotope conservation and Rayleigh fractionation model analysis means of site groundwater pollution characteristics, analysis of site monitoring indicators of pollution control mechanism of the formation of the distribution process, identify groundwater component of oil biodegradation. Specific research results are as follows: First, site groundwater pollution characteristics of the different positions of the site pollution sources and sources of pollution downstream from the surface to the upper part of the aquifer soil samples at different depths TPH concentration analysis showed that: Groundwater pollution pathway for the direct transmission of air pollution mainly oil wells back to the water accident oily wastewater directly caused by penetration into the aquifer. Groundwater TPH concentration multi-phase monitoring results of the monitoring wells groundwater have been polluted to varying degrees during the monitoring of the monitoring wells TPH concentration basically stable groundwater space, of TPH contamination dizzy from pollution sources along the flow direction downstream expansion, pollution halo axis The portion substantially in the observation hole, Z1-Z7, Z16, Z9 constitute a straight line, to the shaft on both sides of the TPH concentration gradually decreases. Groundwater petroleum hydrocarbon contaminated sites, water chemistry spatial and temporal characteristics and formation process of analysis showed that water chemistry indicators of contaminated sites Temporal and Spatial Characteristics: Key Indicators of the various monitoring wells content changed little in the three-month monitoring period, relatively stable , contaminated sites, groundwater environment has reached a state of relative balance; space along the axis of the pollution halo from pollution sources to downstream monitoring biological degradation indicators show a certain regularity: characterization of petroleum hydrocarbon biodegradation product DIC concentrations gradually reduce, the main electron acceptor from low to high, and the main physical and chemical indicators of pH value on behalf of the groundwater environment, Eh corresponding demonstration increasing trend, indicating biodegradation of petroleum hydrocarbons. Application of factor analysis method successfully extracted from a number of indicators for monitoring the impact site groundwater chemical properties of the five main factor, combined with the main factor corresponding to the variation of the composition in space to prove that the environmental impact from the control site groundwater chemistry factors for Mineral Dissolution and petroleum hydrocarbons microbial degradation reactions. On this basis, on behalf of the microbial degradation of F2 main factor score coefficient of observation points based on microbial degradation of petroleum hydrocarbons in the degree of response to the strength distribution in space, combined with the method of cluster analysis, each monitoring site revealed the water chemistry and its reaction process is divided into two categories, Category 1 distributed in the upstream of the sources of pollution and pollution halo, the main controlling factor for petroleum hydrocarbons microbial degradation; Category 2 is mainly distributed in the space downstream of the pollution halo and edge position, primarily due to the impact of the the soluble mineral dissolution process. CONCLUSION verified score coefficient obtained by the factor analysis. Third, the carbon isotope geochemistry of the biodegradation of petroleum hydrocarbons in groundwater on site hydrogeological conditions, mineralogy, soil organic carbon and water chemical indexes content analysis to determine the main source of inorganic carbon in the site groundwater uncontaminated conditions of carbonate mineral dissolution process, and then get the uncontaminated groundwater 13C values ??near -10% 0. The venue by the value of petroleum hydrocarbon contaminated groundwater δ13CDIC exhibit two different trends: from contaminated sites off Z7-oriented the pollution halo downstream petroleum hydrocarbon content decreased, DIC concentrations in groundwater is reduced accordingly, and the 13C values ??gradually increased to Z10 is not the level of pollution of groundwater; Z7 section upstream pollution sources near each groundwater observation wells 13C values ??are higher than the site groundwater background values ??range. Combined with the characteristics of site contamination, degradation products and electron acceptor content of the spatial distribution of different sources of inorganic carbon 13C range of values, the Z7 section downstream of contaminated groundwater by petroleum hydrocarbons methanogenic biodegradation of inorganic carbon supply, and the upstream groundwater inorganic carbon content mainly by methanogenic biodegradation. Site groundwater contaminated by petroleum hydrocarbons δ13CDIC conservation analysis showed that the contaminated sites Z7 section the following contaminated groundwater inorganic carbon content increases 58.9% from petroleum hydrocarbons in methanogenic microbial degradation: petroleum hydrocarbons in groundwater biodegradable sulfur isotope geochemistry pollution the venue of groundwater SO42 its varied δ34S value space law: extends along the pollution halo Z1-1 cross-section in the direction of the venue following The δ34S values ??showing a trend to decrease gradually increased with the content of SO42-, , Description of upstream biodegradable role of a more thorough, more SO42-use as an electron acceptor, while making more enriched residual SO42-34S isotope. The low δ34S value of the site near the source of pollution Z23 and E3 hole analysis of the reasons may have been influenced δ34S values ??lower oily wastewater intrusion and adsorption of aqueous medium iron hydroxides and oxides role. Contaminated sites, groundwater is a relatively closed system under the conditions of contaminated sites, the use of the Rayleigh fractionation model the SO42-34S enrichment factor ε -8.23%. The results reported in the study of degradation and other petroleum hydrocarbon contaminated groundwater dust - more consistent. SO42-biodegradation as an electron acceptor sulfur isotope geochemical environment of contaminated sites.

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