Evaluating crude oil distribution tendencies in a multi-phase aquatic system: Effects of oil type, water chemistry, and mineral sediment.

Planning for effective response to crude oil spills into water depends on evidence of oil behavior, including its tendency to become distributed throughout an aquatic system. An improved laboratory method is employed to quantitatively assess crude oil distribution among different layers that form after mixing within a multi-phase system of water and sediment. Mixtures of conventional crude oil or diluted bitumen with different water types in the presence or absence of mineral sediment are first mixed by a standard end-over-end rotary agitation protocol. After a settling period, each mixture's visibly distinct floating, surface oil (e.g., slick or emulsion), subsurface bulk water, and bottom layers are then separated. Finally, the masses of oil, water, and sediment constituting each layer are isolated, quantified, and compared. The novel results reveal how component properties affect oil distribution among layers to inform spill behavior models, risk assessments, and response plans, including applications of spill-treating agents.

Aqueous naphthenic acids and polycyclic aromatic hydrocarbons in a meso-scale spill tank affected by diluted bitumen analyzed directly by membrane introduction mass spectrometry.

With the increasing use of unconventional, heavy crude oils there is growing interest in potential impacts of a diluted bitumen (DB) spill in marine and freshwater environments. DB has the potential to release several toxic, trace organic contaminants to the water column. Here, the aqueous concentrations and compositions of two classes of organic contaminants, naphthenic acids (NAs) and polycyclic aromatic hydrocarbons (PAHs), are followed over 8 weeks after a simulated spill of DB (10 L) into a freshwater mesocosm (1200 L) with river sediment (2.4 kg). These complex samples contain biogenic dissolved organic matter, inorganic ions, petroleum contaminants, suspended sediments, and oil droplets. We report the first use of condensed phase membrane introduction mass spectrometry (CP-MIMS) as a direct sampling platform in a complex multi-phase mesocosm spill tank study to measure trace aqueous phase contaminants with little to no sample preparation (dilution and/or pH adjustment). CP-MIMS provides complementary strengths to conventional analytical approaches (e.g., gas- or liquid chromatography mass spectrometry) by allowing the entire sample series to be screened quickly. Trace NAs are measured as carboxylates ([M-H]-) using electrospray ionization and PAHs are detected as radical cations (M+•) using liquid electron ionization coupled to a triple quadrupole mass spectrometer. The DB-affected mesocosm exhibits NA concentrations from 0.3 to 1.2 mg/L, which rise quickly over the first 2 - 5 days , then decrease slowly over the remainder of the study period. The NA profile (measured as the full scan in negative-electrospray ionization at nominal mass resolution) shifts to lower m/z with weathering, a process followed by principal component analysis of the normalized mass spectra. We couple CP-MIMS with high-resolution mass spectrometry to follow changes in molecular speciation over time, which reveals a concomitant shift from classical 'O2' naphthenic acids to more oxidized analogues. Concentrations of PAHs and alkylated analogues (C1 - C4) in the DB-affected water range from 0 to 5 µg/L. Changes in PAH concentrations depend on ring number and degree of alkylation, with small and/or lightly alkylated (C0 - C2) PAH concentrations rising to a maximum in the first 4 - 8 days (100 - 200 h) before slowly decaying over the remainder of the study period. Larger and heavily alkylated (C3 - C4) PAH concentrations generally rise slower, with some species remaining below the detection limit throughout the study period (e.g., C20H12 class including benzo[a]pyrene). In contrast, a control mesocosm (without oil) exhibited NA concentrations below 0.05 mg/L and PAHs were below detection limit. Capitalizing on the rapid analytical workflow of CP-MIMS, we also investigate the impacts of sample filtration at the time of sampling (on NA and PAH data) and sample storage time (on NA data only).

Distributions of diluted bitumen and conventional crude oil in a range of water types.

Concern about the impacts that accidental discharge of under-investigated, heavy petroleum products may have on aquatic environments has prompted a comparative examination of the behaviours of diluted bitumen (DB) and light conventional crude (CC) oil in different water types. Distributions of oil among the water column and floating water-in-oil (w/o) emulsion are evaluated by a novel, reproducible procedure involving mixing oil with water, then separating, extracting, and quantifying the total absolute oil content of the water column via gravimetric and gas-chromatographic (high-temperature simulated distillation) analyses. The CC contents of water columns tend to be significantly greater than those of DB under comparable conditions, while the fraction of oil remaining afloat at the water's surface is greater for DB than for CC. The elucidated phase distribution patterns have important implications pertaining to the recoverability of these oils in the event of their release into aquatic environments, which serves to inform best practices for oil spill response. For both DB and CC, oil contents within water columns are the highest in waters of low salinity and high pH. Water contents of buoyant w/DB emulsions are significantly greater than those of w/CC emulsions after 60 min at rest, and are the highest in waters of low salinity and low pH. The effect of crude oil on the pH of water is also studied, and DB is found to have a greater effect than CC on water samples of varying initial pH.

The Lewis acidity of fluorophosphonium salts: access to mixed valent phosphorus(III)/(V) species.

Oxidative fluorination of the electron-deficient phosphine Ph(2)P(C(6)F(5)) using XeF(2), followed by fluoride ion abstraction from the resulting difluorophosphorane Ph(2)P(F)(2)(C(6)F(5)), produces electrophilic fluorophosphonium salts [Ph(2)P(F)(C(6)F(5))][X] (X = FB(C(6)F(5))(3) or O(3)SCF(3)). Variable temperature NMR spectroscopic analysis of [Ph(2)P(F)(C(6)F(5))][FB(C(6)F(5))(3)] demonstrates a fluxional process attributed to fluoride ion exchange between B(C(6)F(5))(3) and [Ph(2)P(F)(C(6)F(5))](+), suggesting that these species have comparable Lewis acidities. This exchange can also be illustrated by adding phosphine Ph(3)P to [Ph(2)P(F)(C(6)F(5))][FB(C(6)F(5))(3)] at ambient temperature to produce Ph(2)P(F)(2)(C(6)F(5)) and Ph(3)P-B(C(6)F(5))(3), while heating this mixture results in thermally induced para-substitution of Ph(3)P at the C(6)F(5) group of the phosphonium ion to generate [Ph(3)P(C(6)F(4))P(F)(2)Ph(2)][FB(C(6)F(5))(3)]. Such frustrated Lewis pair reactivity also can be exploited by reacting [Ph(2)P(F)(C(6)F(5))][O(3)SCF(3)] with silylphosphine Ph(2)PSiMe(3) to afford the unique mixed-valent salt [Ph(2)P(C(6)F(4))P(F)Ph(2)][O(3)SCF(3)], which upon the addition of fluoride is converted to Ph(2)P(C(6)F(4))P(F)(2)Ph(2). XeF(2) reacts with [Ph(2)P(C(6)F(4))P(F)Ph(2)][O(3)SCF(3)] at ambient temperature, producing equal proportions of the dicationic salt [Ph(2)P(F)(C(6)F(4))P(F)Ph(2)][O(3)SCF(3)](2) and the bis(difluorophosphorane) Ph(2)P(F)(2)(C(6)F(4))P(F)(2)Ph(2), the latter of which can then be quantitatively converted to the former by adding one equiv of Me(3)SiO(3)SCF(3).