(267) Using the TRIAD approach in sediment quality monitoring near a wastewater outfall.
Armstrong, J1, Sakamoto, K1, Thomas, C1, McCarthy, M1, Ralph, Y1, 1 Orange County Sanitation District, Fountain Valley, CA, USA
ABSTRACT- The sediment quality triad (TRIAD) approach was used to assess sediment quality near the Orange County Sanitation District wastewater outfall in southern California. Samples were collected quarterly from October 1999 through July 2001 at 10 sites for sediment geochemistry, infaunal community, and sediment toxicity analysis. Whole sediment toxicity was tested with the 10-day amphipod (Eohaustorius estuarius) test and porewater toxicity was tested using Microtox. Sediment toxicity changed over time both spatially and in magnitude. Whole sediment test results correlate to the overall good health of the infaunal populations in the monitoring area, while Microtox results suggest that porewater toxicity is increasing both spatially and temporally in the monitoring area. ERM-quotients ranged from 0.06-0.13 with a relationship to the outfall suggested. No ERM values were exceeded at any station for metal or organic compounds. ERL exceedances for tDDT, tPAH, and tPCB were generally localized near the outfall. Community analysis indicates overall enhancement of the infauna near the outfall, with a gradient of decreasing diversity moving away from the outfall. Seventy-six percent of the individual station analyses conclude that low levels of toxicants are present in the sediments, but that toxicity is a laboratory artifact and a normal infaunal community is present. Seventeen percent showed chemicals in the sediment were not bioavailable and there was no evidence of environmental degradation. Four percent indicated that unmeasured chemicals or conditions exist with the potential to cause degradation. Strong evidence for no pollution-induced degradation occurred in only one station analysis. Similarly, strong evidence for pollution-induced degradation occurred in only one analysis.
Key words: triad, sediment toxicity, wastewater, monitoring