ABSTRACT
The long-term effects of discharged oily drill cuttings on native fish populations are of major concern. This study investigates the uptake of oil and synthetic liquid by the mud minnow, Fundulus grandis. when exposed to three different concentrations of low-aromatic mineral oil-wet and synthetic liquid-wet cuttings in flow-through bioassay chambers.
Fish were introduced into the flow-through bioassay system and cultured for 30 days. Water, cuttings, and fish were sampled routinely for analysis. Fish samples were dissected; gut and tissue samples were analyzed separately.
Flow-through water was analyzed by extracting the water sampling tube absorbent. The cutting samples were analyzed by Soxhlet extraction. Fish tissue and gut samples were digested in sodium hydroxide and extracted with ether. The extracted organics in all the samples were analyzed by gas chromatograph!mass spectrometry.
Gas chromatograph!mass spectrometry identified uptake of the mineral oil in fish tissue and gut samples for all cuttings treated with mineral oil-based mud (MOBM). No uptake was measured in any of the tissue samples for all cuttings treated with synthetic liquid-based mud (SBM). An accumulation of synthetic liquid was only detected in one sample of fish gut from the lowest concentration of SBM. The contrast in uptake between the mineral oil and the synthetic liquid is perhaps due to the greater molecular size of the synthetic liquid over that of the mineral oil. It is hypothesized that the greater molecular size of the synthetic liquid restricts uptake by gill and digestive structures.
During the study, there was little migration of either base fluid from the cuttings. Hydrocarbon amounts in the water samples generally decreased during the 30-day test period. All collected organics were liberated as negligibly soluble microdroplets. Tests indicated no selective solubility of released microdroplets and little if any biodegradation for both SBM and MOBM.
