Petroleum products are introduced into the environment through a variety of mechanisms. One example is motor oil contamination which can come from a variety of sources including cars and recreational water craft such as jet skis and boats. Motor oils both synthetic and non-synthetic can produce potentially toxic components through natural weathering processes. To help assess overall ecosystem impact, a key consideration in understanding the mechanism of toxicity is examination of components produced through photochemical processes. Water accommodated fractions (WAFs) are samples of water mixed with oil and are commonly used to mimic environmental conditions when an oil spill occurs. Over time, water soluble species and partition into the water phase of the WAF. This study examined photochemical degradation and subsequent toxicity of various motor oils (synthetic, non-synthetic and detergent). Acidic and basic species formed in WAFs incubated under various light conditions were isolated using liquid/liquid extraction and the resulting toxicity of these fractions determined as a measure of bacterial growth response. For a selected detergent motor oil, sample treatments included: 1) full sun, 2) dark, 3) colored filters in the visible region (red, yellow, orange, green and blue), 4) photosynthetically active radiation (PAR). In a second study, three motor oils were exposed to full sun and PAR and the acid and base fraction toxicity measured. Overall, the motor oils tested showed decreased toxicity after light exposure which is the opposite trend compared to similar, previous studies using crude oil.

Photochemical degradation and relative toxicity of various motor oils

2019 Spring National Meeting

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