Long-term changes in sediment barium inventories associated with drilling-related discharges in the Santa Maria Basin, California, USA

Abstract

From the Abstract: “Nine-year (1986–1995) records of barium (Ba) concentrations in surficial, subsurface, and suspended sediments near offshore oil and gas platforms in the Santa Maria Basin, California, USA, were analyzed to evaluate temporal trends related to drilling activities. These trends provide important information on the long-term effects of drilling discharges on geochemical conditions. Drilling during the 1986 through 1989 (phase II) monitoring period resulted in significant changes in Ba concentrations in suspended particles and surficial sediments, whereas the relatively shorter 1993 through 1994 (phase III) drilling operations resulted in only minor increases in Ba concentrations in suspended sediments. Residual excess Ba was present in some sediments within 500 m of the platforms at concentrations up to an order of magnitude above background. These elevated levels probably were associated with cuttings particles deposited near the base of the platforms. Calculated excess Ba in sediments within 500 m of the platforms represented 6 to 11% of the total Ba discharged during the two drilling periods.”