Figure 4: Geometric mean toxic units (TUs) for dissolved copper as a function of treatment and sample type. If ≥ 80% of measure concentrations were qualified (i.e., censored) maximum likelihood estimate procedures [25] were used to derive geometric mean TUs. These calculations are identified with a less than symbol (“<”) positioned above respective columns. Sample types (e.g., porewater) are identified in the top left-hand corner of each plot, with replicate exposure chambers illustrated with colored bars. The dashed line represents a TU of 1. Treatments included negative controls with water only (H2O) and 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).