Tall oil, sodium salt

Phototransformation in water

Description of key information

Phototransformation in water is not expected to be a significant removal process for the constituents of TOS.

Additional information

There is no information available for phototransformation in water of TOS as a whole substance. Phototransformation in water is not expected to be a significant removal process for the substance due to low light absorption and low light intensity in most natural waters.

A PhD thesis is available which investigates the novel application of tandem, or two stage, photolysis and biological degradation systems for removal of rosin acids from natural river water (McMartin, D W, 2003). This is relevant to the constituents of Block 2 (Rosin acids: Abietic acid; Palustric acid; Pimaric acid).

The river water was collected from the River Saale, Calbe, Germany, downstream of pulp and paper milling industries.

Spiked water samples were exposed to UV radiation (UV₂₅₄ and broadband) for periods of 10 - 24 hours in quartz photochemical reactors. Duplicate experiments with rosin acids at 0.1, 0.5, 2 and 4 mg/L were conducted. Experiments at UV₂₅₄ are indicative of the potential for development of effective wastewater treatment processes. Two broadband UV radiation sources were used to model environmental degradation potential: A 15W fluorescent backlight (300 – 400 nm, max at 350 nm; Philips BLB), which includes the UV wavelengths of solar radiation that reach the earth’s surface; and a Heraeus TQ 150 Z3 immersion lamp, which includes wavelengths in both the UV and visible range (200 – 700 nm), but as it emits high energy UV-C radiation it does not provide as accurate a simulation of natural solar UV radiation as does the Philips lamp.

The four rosin acids investigated (abietic acid, dehydroabietic acid, isopimaric acid and pimaric acid) were highly susceptible to UV/vis radiation. At UV₂₅₄ all four rosin acids were degraded rapidly, with half-life values between 18 and 100 minutes. With the addition of further UV and visible wavelength provided by the Heraeus broad band UV lamp, the rosin acids were most effectively removed. Experiments with the Philips lamp also resulted in rapid removal of the rosin acids, but half-life values were, in general, approximately twice as long.

Half-life values for each of the four rosin acids were independent of initial concentrations.

UV radiation is responsible for only 1% of the total solar irradiance, but is important because it is highly energetic and influences several biological, physical and chemical processes.

No experiments were conducted to determine the photochemical process responsible for rosin acid photolysis (i.e. direct vs indirect); it is likely that all four resin acids are degraded primarily via direct photolysis with indirect methods playing a minor role in overall concentration reduction.

In the natural environment, it must be anticipated that photolysis in river water has minimal effect on both concentration and toxicity of rosin acids since light penetration beyond the upper 5mm is attenuated.

Microbial degradation studies with both pre-photo-treated rosin acid solutions and untreated rosin acid solutions indicated that the pre-treated solutions were much more readily biodegraded. The rate of biodegradation was significantly less than that observed for photolysis but was significantly increased (by a factor of 2) through the use of pre-treatment photolysis.

 

Reference:

McMartin, D W (2003) Persistence and Fate of Acidic Hydrocarbons in Aquatic Environments: Naphthenic Acids and Resin Acids. A Thesis Submitted to the College of Graduate Studies and Research in Partial fulfilment of the Requirements for the Degree of Doctor of Philosophy in the Division of Environmental Engineering, University of Saskatchewan, Saskatoon. By Dena Wynnn McMartin. December 2003.