Box coring artifacts in sediments affected by a waste water outfall

Variations in porosity of surface sediments are often the major cause of se diment loss during gravity and box coring, Sediments with a high content of organic matter usually have higher porosity, and thus, lower resistance (s train) towards mechanical disturbance. Were, we demonstrate that box coring artifacts (i.e. sediment loss and core shortening) can be produced in sedi ments from the Pales Verdes (PV) shelf, which in the past had received rela tively high loads of organic carbon (OC) enriched particulate matter origin ating from the Whites Point outfall that had created a high porosity layer at depth. This has been overlooked as a possibility for obtaining low estim ates of sediment and pollutant accumulation rates. Since any such sediment loss during coring can lead to serious underestimates of sedimentation rate s, our results here may have important implications for any attempts at rec onstructing pollutant fluxes and histories in these coastal marine sediment s. (C) 2001 Elsevier Science Ltd. All rights reserved.