Figure 2: Acid volatile sulfide (AVS) levels (top panel) and excess simultaneously extracted metal (SEMX) levels (bottom panel) in sediments for white sturgeon sediment toxicity tests, calculated to characterize the potential toxicity of sediments contaminated with metals as part of the equilibrium sediment partitioning benchmark approach [32]. Based on these estimates of bioavailable metal, benthic organisms should be adequately protected in sediments if SEM does not exceed AVS (SEMX ≤ 0) when AVS ≥ 0.1 µmol/g (denoted by a horizontal solid line in top panel). On the basis of SEMX, it has been shown that sediments with SEMX < 1.7 µmol/g (denoted by a horizontal dashed line in bottom panel) pose low risk of adverse biological effects, whereas sediments with SEMX > 120 µmol/g (denoted by a horizontal solid line in bottom panel) might be expected to cause adverse biological effects [32]. For SEMX between 1.7 and 120 µmol/g, the potential for toxicity is uncertain. Treatments included artificial sediment (CTRL), reference sediments from Lower Arrow Lake (LALL) and Genelle (GE), and site sediments from Deadman’s Eddy (DE), Northport (NP), Little Dallas (LD), Upper Marcus Flats (UMF) and Lower Marcus Flats (LMF).