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SYNTHETIC-BASED DRILLING FLUIDS: AN ASSESSMENT OF THE SPATIAL DISTRIBUTION OF TOXICANTS IN SEDIMENTS FROM GULF OF MEXICO DRILLING PLATFORMS
Citation:
Daniels, C B. SYNTHETIC-BASED DRILLING FLUIDS: AN ASSESSMENT OF THE SPATIAL DISTRIBUTION OF TOXICANTS IN SEDIMENTS FROM GULF OF MEXICO DRILLING PLATFORMS. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-98/104, 1998.
Impact/Purpose:
This study was designed to provide a qualitative assessment of a series of field sites in the Gulf of Mexico for the Office of Water, with an indication of the potential hazards associated with the field application/use of synthetic-based drilling fluids (SBF).
Description:
Use of the amphipods, Leptocheirus plumulosus and Ampelisca abdita, in these bioassays presented no major difficulties in the execution of these test protocols. Sensitivity to the toxicants was exhibited by L. plumulosus and survival of control animals was good suggesting the suitability of this organism for use. Continued application of these species to evaluations of field-collected sediments contaminated with Synthetic-based drilling fluids (SBF) is encouraged and should enhance our understanding of the toxicity of these products. Data from this initial screening with Leptocheirus plumulosus indicate sensitivity of these species to sediments collected within a 150 meter radius of platform 1 (GI95) and demonstrate the spatial distribution of contaminants along a gradient. Sediments within the vicinity of the other two platforms, (platform 2, SMI57C and platform 3, ST148) proved to be less toxic than those from platform 1 but serve to illustrate the sensitivity of the organism, L. plumulosus to a range of SBF. Data from tests with Ampelisca abdita indicated a lower sensitivity to the field-collected samples than was observed with L. plumulosus. Survival values in the range of the control suggested an apparent lack of toxicity from any of the sites to this organism above those of background. Procedural delays were throught to have reduced the overall responsiveness of Ampelisca abdita in these tests. Measures of sample variability indicated variability between replicate samples from the same grab and between sequential grabs. Variability denoted in composite samples suggests additional research should be conducted to improve the protocol to achieve sample homogenization. Coarse-sieving of field-collected sediments should also be explored to ascertain if such procedural modifications might also reduce sample variability.