Simulating diluted bitumen spills in boreal lake limnocorrals - part 2: Factors affecting the physical characteristics and submergence of diluted bitumen.

We examined the fate and behaviour of diluted bitumen (dilbit) as it weathered for 70 days in freshwater limnocorrals (10 m diameter × 1.5 m depth) installed in a boreal lake to simulate dilbit spills in a natural aquatic environment. We added seven different dilbit spill volumes, ranging from 1.5 to 180 L, resulting in oil-to-water ratios between 1:71,000 (v/v, %) and 1:500 (v/v, %). Volatile hydrocarbons in the dilbit slick decreased rapidly after the dilbit was spilled on the water's surface, and dilbit density and viscosity significantly increased (>1 g mL-1 and >5,000,000 mPa s, respectively). Dilbit sank to the bottom sediments in all treatments, and the time to sinking was positively correlated with spill volume. The lowest dilbit treatment began to sink on day 12, whereas the highest dilbit treatment sank on day 31. Dilbit submerged when its density surpassed the density of freshwater (>0.999 g mL-1), with wind, rain, and other factors contributing to dilbit sinking by promoting the break-up of the surface slick. This experiment improves our ability to predict dilbit's aquatic fate and behaviour, and its tendency to sink in a boreal lake. Our findings should be considered in future pipeline risk assessments to ensure the protection of these important aquatic systems.

Sub-second adsorption for the pico-molar monitoring of diltiazem in pharmaceutical preparations by fast Fourier transformation with the use of continuous cyclic voltammetry at an Au microelectrode in a flowing system.

Diltiazem was determined at the sub-nanomolar level for the first time by a new technique, involving fast Fourier continuous cyclic voltammetry in a flow-injection system. The best performance was achieved with the basic parameters being set at pH value of 2.0, scan rate value of 35 V/s, accumulation potential of 300 mV and accumulation time of 0.8 s. This paper additionally introduces a special computer based numerical method for the calculation of the analyte signal and the noise reduction. Concerning the electrode response calculations were carried out according to the partial and total charge exchanges on the electrode surface after subtraction of background current from that of noise. Furthermore, to obtain a sensitive determination, the currents integration range included all potential scan ranges, even oxidation and reduction of the Au surface electrode, during the measurements. In general, the potential waveform includes the potential steps for cleaning, accumulation and the step of the potential ramp of the analyte. This potential waveform was applied to an Au disk microelectrode in a continuous way. Finally, the method was found to be linear for the concentration range of 1-41450 pg/ml (r = 0.9986), while showing a limit of detection and quantitation of 0.29 and 1 pg/ml, respectively.