Dissolution Rate of BTEX Contaminants In Water

Marine Environmental Research, 1995

The present report describes a reliable method for the preparation of a solution of Kuwaiti crude oil in seawater, and for determining the concentrations of its components. The dissolution rate was monitored by two complementary methods: total dissolved oil was measured by a photochemical dissolved organic carbon (DOC) technique, whilst fluorescent aromatic hydrocarbons, the dominant soluble constituents, were determined by ultraviolet fluorescence (UVF) spectrophotometry. Maximum dissolution was observed after five days stirring of oil on water when concentrations were, respectively, 3.2-3.6 pg C ml' seawater (DOC) and 2.4 pg diesel equivalents mt' seawater (UVF). However, whilst DOC and UVF measurements are suitable for monitoring dissolution, neither provides an accurate estimate of true oil concentrations. The DOC method underestimates volatile constituents (which dominate the water soluble fraction) and UVF detects only fluorescent components and is dependent on a proper match of calibrant and analyte compositions. A more accurate measurement of the concentrations of dissolved hydrocarbons in the seawater was made for samples taken from the dissolution apparatus after jive days stirring, by addition of deuterated internal standards, extraction with n-pentane, controlled evaporation (micro-Kuderna-Danish concentrator) and gas chromatography-mass spectrometry (GC-MS). In a series of related experiments, the recovery of the deuterated internal standards through the isolation steps was found to range from 2I-32% for deuterated benzene, to 51-102% for deuterated phenanthrene.

Geology, 1994

Aqueous solubilities of liquid nonane (C 9 H 20 [liq]) with activities ranging from 1.0 in pure nonane to 0.1 and 0.01 in crude oil have been calculated at-120 °C and 400 bar as a function of oxygen fugacity if 0 Jg), where g stands for gas) in a generic oilfield water containing representative concentrations of NaCl, CaCl 2 , MgCl 2 , and FeCl 2 in equilibrium with minerals in the system Ca0-Mg0-Fe0-C0 2-0 2-H 2 0. The calculations indicate that in the presence of calcite, the oxidative solubilities resulting from the formation of aqueous C0 2 , n-carboxylic acids, and other oxidized organic aqueous species from n-alkanes in crude oil are several orders of magnitude greater than their stoichiometric counterparts. For example, the oxidative solubility in the aqueous phase of nonane with an activity of 0.1 in crude oil coexisting with calcite at the oil-water interface increases dramatically with increasing Iog/ Oj (g) at-120 °C and 400 bar from a stoichiometric solubility of-0.26 ppm to an oxidative solubility of-320 ppm at log f 0l (g) =-56, which is typical of the fugacity of oxygen in hydrocarbon reservoirs at-120 °C and 400 bar. Because oilfield waters are generally acidic, production of carbonic acid by the oxidative dissolution of crude oil in hydrocarbon reservoirs favors generation of secondary porosity at the oil-water interface, which may be mediated by hyperthermobarophilic microbes.

Journal of contaminant hydrology, 2017

Understanding dissolution dynamics of hazardous compounds from complex gasoline mixtures is a key to long-term predictions of groundwater risks. The aim of this study was to investigate if the local equilibrium assumption for BTEX and TMBs (trimethylbenzenes) dissolution was valid under variable saturation in two dimensional flow conditions and evaluate the impact of local heterogeneities when equilibrium is verified at the scale of investigation. An initial residual gasoline saturation was established over the upper two-thirds of a water saturated sand pack. A constant horizontal pore velocity was maintained and water samples were recovered across 38 sampling ports over 141days. Inside the residual NAPL zone, BTEX and TMBs dissolution curves were in agreement with the TMVOC model based on the local equilibrium assumption. Results compared to previous numerical studies suggest the presence of small scale dissolution fingering created perpendicular to the horizontal dissolution front...

2003

To better understand the environmental behaviour of fuel oil used in the power industry ( Fuel oil no.6), in case of accidental spilling in groundwater, a two-step experimental study with laboratory batch equilibrations and with a twodimensional physical model of aquifer was carried-out. Preliminary characterisation of the the oil mixture included determination of boiling points distribution of homologue class of hidrocarbons, followed by determination of mass transfer coefficients at the water-oil iterface of relevant BTX, PAH and TPH substrates. Effective solubilities of SWSCs (Slightly water soluble compounds) were obtained and an empirical equation for evaluating partition coefficients of SWSCs compounds of environmental concern in the commercial Fuel oil no.6 samples was set-up and validated. In the second part of the investigation a physical model of an homogeneous sand aquifer was set up and, by following transport phenomena from oil pools (0.5-1 m long), laying on the water table of the saturated porous media, the influence of mass transfer and dissolution rates of specific compounds (benzene, toluene, naphtalene) were evaluated by continuous sampling of groundwater from the model at fixed contact times (7 and 28 days). Experimental data were correlated by assuming an analytical model for contaminants dissolution in the oil-water system and mass transfer rates for different contaminants were evaluated and compared with the experimental figures obtained after determination of the effluent concentration from the model. A practical relationship between dissolution time of contaminants and filtration velocity of groundwater, as a function of the extension of the pool and water-oil partition coefficient, was also obtained.

1994

To further a quantitative understanding of the effects of weathering on oil spilled at sea, a series of laboratory experiments were conducted to investigate the dissolution and photodegradation kinetics of Kuwait crude oil in seawater. A simple and practical method was developed for the preparation of stable homogeneous samples of sea water-soluble oil (SWSF) at 25 "C. The dissolution was monitored by two independent but complementary methods; total dissolved oil was measured by a photochemical dissolved organic carbon (DOC) technique whilst the dominant soluble constituents, aromatic hydrocarbons, were measured by ultraviolet-fluorescence (UVF) spectrophotometry. Maximum dissolution was observed after slowly stirring oil on seawater for 5 days when concentrations were, respectively, 3.2-3.6 fig C mL * seawater (DOC) and 2.4 /xg diesel equivalents mL ' seawater (UVF). C^ntification of the photodegradation of individual SWSF constituents required development and optimisation of a more specific analytical method. The final method involved addition of deuterated internal standards, extraction with n-pentane, controlled evaporation (micro Kudema-Danish concentration) and gas chromatography-mass spectrometry (GC-MS). Particular care was taken to eliminate sample contamination and storage conditions were also optimised. The recovery of deuterated internal standards through the isolation steps ranged from 30% for benzene-d^ to 100% for phenanihrene-diQ. The method allowed more than fifty compounds, mainly low molecular weight aromatic hydrocarbons, to be identified and quantified in the SWSF. Alkylated benzenes (Q^ were the most abundant (98% of the dissolved oil) followed by alkylated naphthalenes (C0.3) (= 2%). The oil to seawater partition coefficient of individual hydrocarbons (K^^) showed that hydrocarbons of high aqueous solubility (e.g C0.2 alkylbenzenes) also possessed the lowest partition values, whereas compounds with high partition coefficients (e.g. alkylnaphthalenes) remained mainly in the oil phase. A reproducible method of simulating solar irradiation was established under controlled environmental conditions using a calibrated 1.8 kW xenon lamp. The photodegradation of a model SWSF compound (phenanthrene) followed first-order kinetics (kp= 0.317+0.029) with a half life (tj^J of 2.2 hr at 25 "^C when irradiated at 194 Wm'-. The extrapolation of to latitude 30 *' N (Florida summer sunlight) showed that phenantiirene would degrade in = 9 hr. Some photoproducts including fluorene, fluorenone, 2,2'-diformylbiphenyl, 2,3:4,5-dibenzoxepin, 3,4-benzocoumarin, and 9,10phenanthrenequinone were identified by GC-MS, although these accounted for only 11% of the initial mass of phenanthrene. UVF and GC-MS methods for examining the photodegradation of phenanthrene were compared. The photochemical fate of the characterised SWSF was investigated using the optimised irradiation system. Benzene and C^s alkylated benzenes showed no evidence of photodegradation after periods of up to 48 hour under the lamp, however, some C4 alkylbenzenes (jec-butylbenzene, 1,2dimethylbenzene, 1,2,4,5-+ 1,2,3,4-tetramethylbenzene and 1,2,3,4-tetrametiiylbenzene) appeared to follow first-order kinetics with respect to irradiation time. The photodegradation rate constants (kp) of the alkylated benzene and alkylated naphthalene isomers were statistically different demonstrating that certain isomers will phoiodegrade faster tiian others under the same conditions. Half lives ranged from 11.8 to 33.6 hr at 25 ''C. The majority of naphthalene (i.e. C^^^) identified in the SWSF of Kuwait crude oil exhibited first-order photodegradation kinetics with differing rate constants. Half lives were: naphtiialene. 15.7 hr; 1-methyl and 2-methyl naphthalene, 14.9 and 12 hr, respectively; l-l-2-ethylnaphthalene, 15.9; 1,6-dimethylnaphthalene, 10.4hr; 1,3,7-and 1,2,4-trimethylnaphthalene, 11.95 and 12 hr, respectively. The low initial concentration of other naphthalene isomers did not allow for accurate photodegradation kinetics to be determined. Extrapolating the data to latitude 30 "N showed that die photodegradation ti;^ expected for tiie determined SWSF compounds were between 4.2 to 7 days. This would make photodegradation an effective weathering process for the removal of spilled oil, particularly in high solar radiation environments.

Journal of Environmental Monitoring, 2012

Relative toxicity of water-soluble fraction of Kuwait crude oil and different petroleum products in seawater was determined and compared. The toxicity was determined by Microtox. The results indicated that WSFs of crude oil and kerosenes were moderately toxic. WSFs of gasolines were relatively highly toxic. Heavy petroleum products produced WSFs that were relatively less toxic. Relative toxicity of WSFs of these products generally reflected the total concentration of benzenoids in the WSF.

Environmental Science & Technology, 2011

Oil & Gas Science and Technology, 1998

acerca de las mezclas. La utilización de una relación simplificada conduce a subestimar la solubilidad real. En este artículo se presentan algunos nuevos datos de solubilidades de mezclas hidrocarbonadas simples. Un análisis termodinámico riguroso permite describir la solubilidad observada, tanto de las mezclas modelo como de los querosenos. Los modelos de coeficiente de actividad utilizados con este objeto son NRTL, UNIQUAC y UNIFAC. Habida cuenta de la reducida concentración de ciertos componentes en el petróleo, su coeficiente de actividad puede llegar a ser importante. Esto permite explicar un aumento de la solubilidad con respecto a aquella propuesta por el modelo simple de un factor superior a dos. * No data have been found.

Fluid Phase Equilibria, 2013

A simple model is proposed for the calculation of oil and water mutual solubilities as a function of temperature using the hydrocarbon specific gravity and Watson-K factor as correlating parameters. The model parameters were determined using a single consistent set of high quality solubility data collected at the water or hydrocarbon saturation pressures at temperatures from 273 K and 573 K but primarily from 298 K to 398 K. The hydrocarbon in water solubilities ranged over 11 orders of magnitude while the water in hydrocarbons solubilities ranged over 4 orders of magnitude. Hydrocarbon types ranged from low molecular weight paraffins such as n-pentane to heavy aromatics such as anthracene. The average absolute error in the estimated solubilities of water in hydrocarbons over 621 data points was 34% and approached the suggested underlying uncertainty in the reference data (30%). The average absolute error in the estimated solubilities of hydrocarbons in water over 964 data points was 88% and exceeded the suggested underlying uncertainty in the reference data (30%).