The effects of exploratory petroleum drilling in the northwest Gulf of Mexico on trace metal concentrations in near rig sediments and organisms
- Texas A and M Univ., College Station (United States)
For a typical offshore petroleum well, 500-1000 t (dry weight excluding cuttings) of drilling fluid solids are discharged into the sea. In this study, concentrations of selected trace elements present in drilling fluids (Ba, Cd, Cr, Cu, Fe, Pb, Ni, V), were determined in surface sediments and macroepifauna around a Gulf of Mexico exploratory drilling site before, during, and after drilling operations. Observed significant increases in the levels of Fe in organisms and Ba and Cr in sediments were attributable to drilling discharges. Shrimp, which constitute the largest commercial fishery in the region, were intensively studied. Shrimp collected during the last few days of drilling had abdominal muscle Fe concentrations more than twice those in shrimp sampled before or after drilling. Enhanced Fe solubility (bioavailability) in sea-water, caused by soluble organic chelating agents in the drilling fluids, is the most likely explanation for the observed increases. Significant increases in sediment Ba were observed at all sampling radii but large increases (up to 7.5 fold) were only observed within a few hundred meters of the drilling site. An accurate mass balance of total discharged (excess) Ba present in sediments within 1000 m of the drilling site was determined. Only 9.3% of the total Ba used, and presumably other similar drilling mud components traced by Ba, was present within 1000 m at the conclusion of drilling. After 2.6 mo. only 6.6% was present. Significant sediment resuspension and transport occurring in the high current nearshore study site (24 m water depth) was responsible for the low retention and rapid loss of discharged Ba in the sediment. The largest mean increase in sediment Cr (26%) occurred at the 1,000 m sampling radii.
- OSTI ID:
- 5920518
- Journal Information:
- Environmental Geology and Water Sciences; (United States), Vol. 9:3; ISSN 0177-5146
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
54 ENVIRONMENTAL SCIENCES
58 GEOSCIENCES
BARIUM
BIOLOGICAL ACCUMULATION
ECOLOGICAL CONCENTRATION
DRILLING FLUIDS
MARINE DISPOSAL
IRON
OFFSHORE DRILLING
ENVIRONMENTAL EFFECTS
CADMIUM
CHROMIUM
COPPER
GEOCHEMISTRY
LEAD
NICKEL
OFFSHORE PLATFORMS
OFFSHORE SITES
OIL WELLS
SEDIMENT-WATER INTERFACES
SEDIMENTS
SHRIMP
VANADIUM
ALKALINE EARTH METALS
ANIMALS
AQUATIC ORGANISMS
ARTHROPODS
CHEMISTRY
CRUSTACEANS
DECAPODS
DRILLING
ELEMENTS
FLUIDS
INTERFACES
INVERTEBRATES
MANAGEMENT
METALS
TRANSITION ELEMENTS
WASTE DISPOSAL
WASTE MANAGEMENT
WELLS
020900* - Petroleum- Environmental Aspects
540320 - Environment
Aquatic- Chemicals Monitoring & Transport- (1990-)
580000 - Geosciences