Interpreting the Sediment Triad: Harmonizing Instead of Weighting the Evidence

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Hollie Ashlie Miller
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1 Interpreting the Sediment Triad: Harmonizing Instead of Weighting the Evidence Daniel W. Smith, Ph.D., Inc

2 Weight of Evidence Analyses State of the Art for Sediments Multiple lines of Evidence, none alone considered definitive Weight results objectively Makes use of available information Minimizes arbitrariness, increases consensus WOE

3 Weighted Evidence Analyses Current State of Practice for Sediments? Lines of evidence weighted subjectively Ostensibly for technical reasons Really, just policies/preferences Wastes available information Increases arbitrariness, decreases consensus WOEisme

4 Real World Example Small (ca. 4 acres) isolated tidal mudflat Legacy contamination High [Hg], [PCB], [PAHs], [CBs] But also very high Organic Carbon, AVS Eco risks to other guilds dismissed Focus on direct toxicity to benthos

5 Best-Science Chemical Screening ESB non-polar narcotics (PAHs, CBs. PCBs) 9 of 10 sites with ESB < 1.5 For Hg ++, used AVS/SEM method for Me ++ Ample AVS alone wout carbon to bind Hg ++ Prediction No toxicity in 9 of 10 sites Moderate to no toxicity at one location

6 % of Ref Mean Results of Biological Survey 700% 600% 500% 400% 300% 200% 100% 0% Ref 133-Ref 134-Ref Total number Taxa 1/Dominant Diversity Evenness

7 % of Mean Ref Bioassay Results 120% 100% 80% 60% 40% 20% 0% Ref 133-Ref 134-Ref Survival Repro Growth

8 Known Bioassay Biases Disruption of sediment microstructure Minimal dilution ½ dilution 3X/week Less than optimal? food or no food Toxicity less when fed algae Potentially limited genetic potential

9 Leptocheirus plumulosus Common to East Coast US Lives in U-shaped mucus-lined burrow Found at the top of the sediments Measured irrigation rates several times/hr Probably filter-feeder and deposit feeder Pulse species rapid population increases co-incident with phyto blooms Broods young in pouch, young probably dispersal stage In terms of exposure to chemicals, may be more like zooplankton than infaunal benth Among more sensitive species to narcotics

13 Harmonized Lines of Evidence Sediment Chemistry No effects predicted at 90% of areas Null to moderate effects predicted at 10% of area Therefore no effect on community Sediment Bioassays With biases and most sensitive species No tox. at 50%, low tox at 30%, mod tox at rest Estimated bias 3 to 10 or more Wout bias, no effects likely at 9 or 10 of 10 sites No effects on community Biological Survey No effects on community

14 Common Sense Ending Get it in writing Know your ecosystem Be willing to manipulate methods

15 SQB, mg/kg 1000 LT-SQG for Metals vs. Median Urban Conc. In Sediments from US ERL TEL TEC MOE LEL Median Background, mg/kg 20

16 ER-L,Log10 ug/kg ER-M, Log10 ug/kg 8 7 ER-L and ER-M Values for PAH, metals, PCB vs. Ambient Conc R 2 = R 2 = Log10 Ambient Conc,ug/kg ERL vs 34%ile ERM vs. 68%ile 1 21

17 Random (Analytical) SELs and LELs vs. MOE Values for Metals (mg/kg) Hg Cd Ar R2 = 0.99 Pb NiCu Cr Mn Zn Fe R2 = E+06 SEL LEL 22

18 Random ug/kg OC vs. MOE Values for PAH, PCB, Pesticides R 2 = R 2 = 0.97 LEL SEL MOE ug/kg OC 23

19 Random ug/kg OC Random (by iteration) SELs and LELs vs. MOE Values for PAH, PCB, Pesticides R2 = R2 = SEL LEL MOE ug/kg OC 24

20 Conclusions of Analysis Values statistically similar to LELs and SELs can be generated with constrained random sampling of the chem. conc. This sampling does not include effects at all Magnitude of SEL and LEL function of 1. Bias (choice of chemical to estimate SEL/LEL) 2. Randomness (constrained random sampling) 3. Distribution of chemicals in the database Therefore, critical assumption that SELs and LELs are effects-based, toxicological values is mirage, delusion, fantasy, myth, blather, poppycock, drivel, nonsense, hoax, balderdash, BS, inanity,.. 25

Assessing and Predicting Effects of Sediment Contamination

Assessing and Predicting Effects of Sediment Contamination David R. Mount U.S. Environmental Protection Agency Office of Research and Development Mid-Continent Ecology Division, Duluth, MN Why Study Sediments?