Almost 25 years of chromatographic and spectroscopic analytical method development for petroleum hydrocarbons analysis in soil and sediment: State-of-the-art, progress and trends

This review provides a critical insight into the selection of chromatographic and spectroscopic techniques for semi-quantitative and quantitative detection of petroleum hydrocarbons in soil and sediment matrices. Advantages and limitations of both field screening and laboratory-based techniques are discussed and recent advances in chemometrics to extract maximum information from a sample by using the optimal pre-processing and data mining techniques are presented. An integrated analytical framework based on spectroscopic techniques integration and data fusion for the rapid measurement and detection of on-site petroleum hydrocarbons is proposed. Furthermore, factors influencing petroleum hydrocarbons analysis in contaminated samples are discussed and recommendations on how to reduce their influence provided

Predicting polycyclic aromatic hydrocarbon concentrations in soil and water samples

Polycyclic Aromatic Hydrocarbons (PAHs) are compounds found in the environment that can be harmful to humans. They are typically formed due to incomplete combustion and as such remain after burning coal, oil, petrol, diesel, wood, household waste and so forth. Testing laboratories routinely screen soil and water samples taken from potentially contaminated sites for PAHs using Gas Chromatography Mass Spectrometry (GC-MS). A GC-MS device produces a chromatogram which is processed by an analyst to determine the concentrations of PAH compounds of interest. In this paper we investigate the application of data mining techniques to PAH chromatograms in order to provide reliable prediction of compound concentrations. A workflow engine with an easy-to-use graphical user interface is at the heart of processing the data. This engine allows a domain expert to set up workflows that can load the data, preprocess it in parallel in various ways and convert it into data suitable for data mining toolkits. The generated output can then be evaluated using different data mining techniques, to determine the impact of preprocessing steps on the performance of the generated models and for picking the best approach. Encouraging results for predicting PAH compound concentrations, in terms of correlation coefficients and root-mean-squared error are demonstrated

Implementation of spectroscopy as a rapid measurement tool (RMT) to inform risk assessment at petroleum contaminated sites in the Niger Delta, Nigeria.

The recent developments and applications of rapid measurement tools (RMT) such as visible near-infrared (vis-NR) spectroscopy can provide ‘fit for purpose’ and cost effective data for informing risk assessment and managing oil-contaminated sites. Infrared spectroscopy discriminates between chemical compounds by detecting the specific vibrational frequencies of molecular bonds, producing a unique infrared ‘spectral signal’ thereby enhancing its identification and quantification applying chemometrics. The aim of the research was therefore to assess the potential of vis-NIR and mid-infrared (MIR) diffuse reflectance spectroscopy (DRS) techniques as RMT to inform risk decision support for remediation of petroleum contaminated sites. The objectives of the study were to: critically review chromatographic and spectroscopic methods for petroleum hydrocarbon analysis in soils; evaluate vis-NIR sensitivity to detect hydrocarbon concentration differences throughout weathering; predict TPH, PAH and alkanes concentrations in contaminated soils using vis-NIR and MIR DRS coupled with regression techniques. The study further evaluated which spectroscopy technique (vis-NIR or MIR); and which modelling method (RF or PLSR) performs best. In this study, a series of 13 soil mesocosms was set up where each soil sample collected was spiked with 10 ml of Alaskan crude oil and allowed to equilibrate at room temperature for 48 h before analysis. The mesocosms were incubated for two years at roomntemperature in the dark. Soils scanning and gas chromatography coupled to mass spectrometry (GC-MS) analysis were carried out at T0, 4, 12, 16, 20 and 24 months. Prior to scanning, soil samples were air-dried at room temperature (21oC) to reduce the effect of moisture. The soil scanning was done simultaneously using an AgroSpec spectrometer with a spectral range of 305 to 2200 nm (tec5 Technology for Spectroscopy, Germany) and Analytical Spectral Devices LabSpec2500 spectrometer (ASD Inc, USA) with a spectral range of 305 to 2500 nm to assess and compare the sensitivity and response of the two instruments to weathering and hydrocarbon composition change overtime against GC-MS data. Partial least squares (PLS) and random forest (RF) regression models showed that ASD LabSpec2500 performed better than tec5 which may be attributed to the shorter wavelength spectra range of the tec5 spectrometer and therefore not detecting all significant hydrocarbon signals (e.g., 2207, 2220, 2240 and 2460 nm). The sensitivity of the two spectral devices to weathering and REWARD K. DOUGLAS Cranfield University PhD Thesis, 2018 hydrocarbon composition change was, however, comparable; and the predicted concentrations were also comparable to the hydrocarbons concentrations determined by GC-MS. The results (coefficient of determination, R²=0.9; ratio of prediction deviation, RPD=3.79 and root mean square error of prediction, RMSEP=108.56 mg/kg) demonstrate that visible-near infrared diffuse reflectance spectroscopy (vis-NIR DRS) is a proven tool for rapid site investigation and monitoring without the need of collecting soil samples and lengthy hydrocarbon extraction for further analysis..To this end, 85 soil samples collected from three crude oil spill sites in the Niger Delta, Nigeria. Prior to spectral measurement, soil physiochemical properties such as pH, total organic carbon and textural analysis were carried out. Soil samples were scanned (field-moist) and assessed using ASD LabSpec2500 (wavelength 350-2500 nm) and MIR data was acquired with Agilent 4300 handheld Fourier transform infrared (FTIR) spectrometer (Agilent Technologies, Santa Clara, CA, United States) with a spectral range of 4000- 650 cmˉ¹. Specifically, detailed analysis of the hydrocarbon content including total petroleum hydrocarbons (TPH), aliphatic and aromatic hydrocarbon fractions were determined and quantified by GC-MS, vis-NIR and MIR DRS. MIR over-performed vis-NIR with RF modelling method performing better than PLSR in predicting TPH, PAH and alkanes. However, PLSR-vis-NIR produced slightly better results than PLSR- MIR in predicting TPH and alkanes. Overall, vis-NIR (wavelength 350-2500 nm) laboratory-scale study yields better TPH prediction than the field-scale study. The minimised moisture content may have improved the results, as laboratory-scale samples were air-dried. Based on the results, MIR spectroscopy coupled with RF is recommended for the analysis of hydrocarbon contaminated soil. Finally, spectroscopy approach was proposed as RMT for contaminated soil investigation and risk prioritisation.PhD in Environment and Agrifoo

δ13C and δD measurements of volatile organic compounds in a variety of emissions by thermal desorption compound specific isotope analysis

Volatile organic compounds (VOCs) can be related to different compound classes but they all have a distinct vapour pressure allowing them to enter the atmosphere under ambient conditions. VOCs can undergo various reactions in the atmosphere and are emitted by various processes (anthropogenic and natural). Compound specific isotope analysis (CSIA) has been used in many other research studies to track the fate and source of compounds in the environment and the geological record. The majority of CSIA has been applied to extracts from soil, sediment or crude oils requiring entirely different sampling techniques compared to atmospheric samples. Applying CSIA to atmospheric compounds is a growing research field but has mainly being restricted to stable isotopes of carbon.This PhD thesis presents a novel application for adsorptive sampling on TenaxTA to analyse compound specific δ13C and δD of a range of atmospheric VOCs (C6 - C10). For the first time a 2-stage thermal desorption (TD) unit was linked to gas chromatography isotope ratio mass spectrometry (GC-irMS) and instrumental conditions were thoroughly investigated and optimised. Results obtained by using a standard mix of eleven VOCs confirmed reliability of TD-GCirMS analyses with standard deviations (SD) below instrument precision. δ values showed negligible isotopic fractionation compared to results obtained from traditional GC-irMS analysis (without TD unit) demonstrating the suitability of TD for CSIA.The technique was applied to analyse VOCs from various emission sources, e.g. car exhaust, biomass combustion and an industry stack. The results obtained have provided some insight into the formation processes of the VOCs investigated. δ13C values from an alumina refinery emission support a natural origin for the VOCs (organic material in bauxite ore). The δD values (21 to - 137 ‰) of the industry emission were consistently more enriched in D compared to δD values of VOCs previously reported making the δ values of VOCs in the industrial stack unique. Car exhaust emission from a petrol engine showed significant differences in δ values for VOCs up to 2 ‰ and 25 ‰ (δ13C and δD, respectively) at different tank fuel levels when using the same fuel batch. Car exhaust emission samples from a diesel engine showed a high content of highly complex mixture of unresolved compounds thus chromatographic baseline separation of VOCs was not achieved for stable hydrogen isotope analysis and led to unreliable δ values. The results from different biomass combustion emissions (including 5 species of C3 plants and 3 species of C4 plants) confirmed significant differences in δ13C of VOCs between C3 and C4 plants due to their specific metabolic pathways for carbon fixation in photosynthesis. The δD of VOCs derived from dicotyledons were less depleted in D compared to δD of VOCs derived from grasses (differences >27 ‰) indicating that the VOCs are derived mainly from lignin/cellulose rather than from lipids since dicotyledons contain higher amounts of lignin/cellulose.Due to the unique isotopic signatures of the VOCs from the different emission sources it was possible to distinguish their origins. Furthermore, TD-GC-irMS shows great potential to establish other emission sources in the environment and may help to gain some insight into their modes of formation

DEGRADATION AND MOBILITY OF PETROLEUM HYDROCARBONS IN OILSANDS WASTE AT THE AURORA FORT HILLS DISPOSAL AREA

Surface mining in the Athabasca oil sands region of Northern Alberta, Canada, results in the disturbance of significant areas of boreal forest landscape. The Aurora Soil Capping Study is a reclamation research project that aims to find the optimal soil capping (cover) material and thickness to re-establish a boreal forest ecosystem above a lean oil sands (LOS) disposal area at Syncrude's Aurora North mine. The objectives of this laboratory and field-based study are to (1) characterize the in-situ hydrocarbon composition of the LOS material, (2) determine the effect of temperature on rates of gas flux and the biodegradation potential of petroleum hydrocarbons (PHC) as a result of microbial activity and (3) determine the potential for PHC to leach into the groundwater system. The results of the laboratory-study show that temperature has a significant effect on the rate of PHC degradation as indicated by the linear relationship observed between temperature and CO2 gas flux rates. The respiratory results from the laboratory-based study were consistent and relatively comparable with data from the field study, which indicates that the column study could be useful in estimating in situ PHC degradation

Baseline study on chemical composition of Brunei Darussalam rivers

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University, 16/6/2005.The research provides data of pH and conductivity, some anions (e. g. fluoride, chloride, bromide, nitrate, phosphate and sulphate), monovalent cations (e. g sodium, ammonium and potassium), divalent cations (e. g calcium and magnesium) heavy metals (e. g. iron, copper, zinc, nickel, cobalt, cadmium and manganese) and organic compounds – from water samples of rivers of Brunei Darussalam, namely, Brunei River, Belait River, Tutong River and Temburong River. The higher values of certain parameters with respect to the acceptable standard limits for river water indicate the pollution in river water samples of the study area, make the waters unsuitable for various applications and do pose a human health hazard. The pH levels in Brunei Darussalam is quite reassuring and mostly safe. Although there are some stretches of rivers that show slightly lower levels of pH, there is no cause for any alarm as these waterways are not sources of drinking water. As for anions and cations, the only anion of significant levels detected in Brunei Rivers is chloride whereas only monovalent cation detected in significant levels, is sodium. The concentrations of chloride and sodium ions are below the standard concentrations. Brunei Rivers are still free from chloride and sodium pollution. For heavy metals, only iron is detected in Brunei Rivers. Brunei being a oil based country experiments were done to identify levels of a numbers of significant toxic organic compounds, including, toluene and benzene which have been detected in the waters of the oil mining district of Belait District but are within normal limits. The use of a photolytic cell system to achieve the photodegradation of benzene, toluene, ethylenediaminetetra-acetic acid (EDTA) and the surfactant – hexadecyltrimethyl-ammonium bromide (C19H42NBr) is reported. The system has been optimised by investigating the effects of the addition of hydrogen peroxide (H202) as an oxidant and the addition of titanium dioxide (TiO2) as a catalyst. The results show that the photolytic system can be used to achieve >99% degradation of organic contaminants. The research also includes a final chapter on management system which covers water protection, pollution control and solid waste management in Brunei. In addition to investigating various factors of the solid waste management in Brunei, the researcher has also exposed some of the weaknesses that need immediate addressing. Various measures have been suggested to make Brunei's water more efficient. Moreover, ways of preserving the high quality of Brunei's water figures in this chapter

Application of subcritical and supercritical fluids in coal extraction and analysis

Coal is used to generate electricity and produce high-value chemicals through coal gasification, liquefaction, and coke. During combustion sulfur is released, which leads to acid rain formation. Mineral matter present in coal is undesirable because it causes technological problems such as corrosion of equipment and reduction of overall rate of combustion of coal. Also, after combustion, the mineral matter which has been transformed to solid waste (ash) is disposed of in landfills. The reported pre-combustion extraction methods for desulfurization and demineralization are time consuming, require the use of large volumes of environmentally toxic reagents at high temperature and they are not selective.The main aim of this thesis was to systematically develop desulfurization and demineralization methods based on non- toxic solvents using pressurized liquid extraction (PLE) and supercritical fluid extraction (SFE). The main emphasis was placed on achieving high selectivity for total sulfur and mineral matter during solvent extraction. Therefore, optimization of extraction methods in terms of solvent composition, extraction temperature and extraction time using Box Benhken design was carried out. The aim was to maximize solubility of target analytes, to improve mass transfer properties of the extraction solvent as well as reducing extraction temperature and time.Water with ethanol as a co-solvent was used during PLE method development. The results showed that increasing ethanol content resulted in higher extracted amount of total sulfur at mild temperature in a short time, corresponding to decrease in viscosity which resulted in fast diffusion of solvent and fast mass transfer. At optimum conditions, total sulfur extraction efficiency of 79 wt.% from the raw coal was achieved. SFE utilized supercritical carbon dioxide (scCO2) with ethyl lactate (EL) as a co-solvent. Higher temperature and lower ethyl lactate content significantly increased extraction of total sulfur even though increasing temperature reduces the density of scCO2. Higher solubility of sulfur compounds may be due to their increased vapour pressure in addition to the more polar solvent. At optimum conditions, total sulfur extraction efficiency of 93 wt.% from the raw coal was achieved. Neither of the methods were efficient in extracting mineral matter from the raw coal in comparison to extraction with acids/bases such as nitric acid and sodium hydroxide.Overall, the two methods have similar effects on the raw coal. Additionally, the properties of the raw coal were slightly improved. In addition to the reduction of the sulfur content, the thermal decomposition and burnout temperatures were decreased to a more considerable extent compared to the combustion temperature and the temperature at which maximum conversion of coal occurs. The calorific value, fixed carbon and volatile content have also increased and these parameters are all important in the combustion efficiency of coal.The research presented here serves as a base for the scaling up of extraction methods that utilizes green and environmentally sustainable solvents for reduction of pollution from coal combustion