Summary Report of the Meeting to Peer Review MPCA’s Draft Analysis of the Wild Rice Sulfate Standard Study Saint Paul, MN August 13-14, 2014 Submitted to: Minnesota Pollution Control Agency (MPCA) Submitted by: Eastern Research Group, Inc. 110 Hartwell Avenue Lexington, MA 02421 Final Report: September 25, 2014 wq-s6-43i Notice This report was prepared by Eastern Research Group, Inc. (ERG), a contractor to the Minnesota Pollution Control Agency (MPCA), as a general record of discussion during the Peer Review Meeting on MPCA’s Draft Analysis of the Wild Rice Sulfate Standard Study, held August 13 and 14, 2014, in St. Paul, Minnesota. This report captures the main points and highlights of the meeting. It is not a complete record of all details discussed, nor does it embellish, interpret, or enlarge upon matters that were incomplete or unclear. Statements represent the individual views of meeting participants. Contents 1. INTRODUCTION .................................................................................................................... 1 2. REVIEWER CONCLUSIONS AND RECOMMENDATIONS.......................................................... 4 3. SUMMARY OF REVIEWER DISCUSSIONS ............................................................................. 10 3.1 LABORATORY HYDROPONIC EXPERIMENTS .................................................................. 10 Charge Question 1: Discuss the appropriateness of the sulfide seedling hydroponic test method and performance in evaluating the hypothesis that elevated sulfide in the sediment porewater can be toxic to wild rice.................................................................................................. 10 Charge Question 2: Is it reasonable to use the initial exposure concentrations as the operative exposure concentration for the test? Why or why not? If not, which approach do you suggest? ................................................................................................................................... 12 Charge Question 3: Is regression analysis to derive EC20 and EC50 values an appropriate way to analyze the sulfide seedling hydroponic data to identify effect levels? Why or why not? Is there an alternative approach to evaluate the data for effect levels that you would suggest the MPCA pursue? .............................................................................................................. 13 3.2 UTILITY OF THE FIELD SURVEY DATA ............................................................................. 15 Charge Question 4: Discuss whether the Analysis demonstrates that the lake and stream field survey data and results are sufficiently representative of Minnesota lakes and streams with wild rice to 1) examine the chemical relationships between sulfate in surface water and acid-extractable iron, acid-volatile sulfide, and porewater concentrations of sulfide and iron, and 2) inform protection of wild rice from elevated sulfate. Please note any specific questions or concerns. .................................................................................................................... 15 3.3 MESOCOSM EXPERIMENT ............................................................................................. 18 Charge Question 5: Does the MPCA Analysis make appropriate use of the mesocosm experiment data? Please describe any suggestions you have about how the data could be further analyzed, or any cautions about the existing or potential use of these data. ........................ 18 3.4 WILD RICE IN RELATION TO SULFATE, SULFIDE, AND IRON ........................................... 23 Charge Question 6: Do you agree or disagree with MPCA’s assertion that the field survey and mesocosm experiment data further support the hypothesis that elevated sulfide in the sediment porewater above 300 µg/L can be toxic to wild rice? Why or why not? ............................ 23 3.5 CONTROL OF POREWATER SULFIDE BY THE AVAILABILITY OF SULFATE AND IRON ...... 25 Charge Question 7: Is the use of multiple quantile regression an appropriate tool for predicting porewater sulfide concentrations? Why or why not? If not, what other options for predicting porewater sulfide would be suitable? ............................................................................. 25 Charge Question 8: In the multiple quantile regression, MPCA relied on the acid-extractable iron rather than the porewater iron to predict porewater sulfide concentrations based on i surface water sulfate concentrations. Do you agree or disagree with this approach? Why or why not? ......................................................................................................................................... 27 3.6 SYNTHESIS: HOW SULFATE, SULFIDE, AND IRON INTERACT TO AFFECT WILD RICE ...... 29 Charge Question 9: The MPCA Analysis focuses on sulfide in the porewater as the sulfur parameter impacting wild rice, and the role of sulfate and iron as key variables controlling sulfide concentrations in porewater. Was this focus appropriate to inform understanding of the effects of sulfate on wild rice? Why or why not? If not, what other variables do you suggest the MPCA explore? ............................................................................................................. 29 Charge Question 10: Please identify any concerns you have about the Synthesis, particularly any key omissions or assumptions in the logic that should be further evaluated. ............................ 31 3.7 GENERAL QUESTIONS ................................................................................................... 34 Charge Question 11: Please state your overall assessment of the five Study components. Did MPCA choose appropriate Study components to meet Study objectives and to support the Analysis? Why or why not?.............................................................................................................. 34 Charge Question 12: Please provide any other comments you may have on the Study data collection and interpretation, or on the Analysis. ............................................................................ 35 Charge Question 13: Please identify any other issues or critical data gaps for further research that should be considered when evaluating the relationship between wild rice and sulfate. ............................................................................................................................................ 37 Appendix A: Charge to Reviewers ......................................................................................... A-1 Appendix B: Peer Reviewers .................................................................................................. B-1 Appendix C: Meeting Agenda ................................................................................................ C-1 Appendix D: Meeting Observers ............................................................................................ D-1 Appendix E: Observer Oral Comments ................................................................................... E-1 Appendix F: Reviewer Post-Meeting Comments .................................................................... F-1 Appendix G: Slides Provided by Dr. Pollman ......................................................................... G-1 Appendix H: Figures Referenced or Provided by MPCA ......................................................... H-1 Appendix I: Figure Provided by Dr. Arts .................................................................................. I-1 ii Acronyms and Abbreviations ACPR augmented component plus residual plots ANOVA analysis of variance AVS acid-volatile sulfide CFD cumulative frequency distribution DOC dissolved organic carbon EC effect concentration ERG Eastern Research Group, Inc. IAP ion activity products Ksp solubility product constant LC lethal concentration MN DNR Minnesota Department of Natural Resources mg/L milligrams per liter MPCA Minnesota Pollution Control Agency µg/L micrograms per liter NOEC no observed effect concentration ppb parts per billion ppm parts per million QA/QC quality assurance/quality control SEM structural equation modeling TOC total organic carbon TWA time-weighted average U.S. EPA U.S. Environmental Protection Agency iii 1. Introduction Background To enhance scientific understanding of the effects of sulfate on wild rice, the Minnesota Pollution Control Agency (MPCA) contracted with Eastern Research Group, Inc. (ERG) in 2014 to organize an independent scientific peer review of the Agency’s Analysis of the Wild Rice Sulfate Standard Study: Draft for Scientific Peer Review (Analysis). The Analysis integrates the results of a five-component study (Study) funded by MPCA to gather information about the effects of sulfate and other substances on wild rice growth. Conducted by scientists at the University of Minnesota Duluth and Twin Cities during 2012 and 2013, this research was intended to inform the Agency’s evaluation of the state’s sulfate water quality standard, adopted in 1973, of 10 mg/L applicable to water used for production of wild rice. The Study’s main hypothesis was that wild rice is impacted by sulfate via the conversion of sulfate to sulfide dissolved in the water in the sediment, known as the sediment porewater (see Appendix A for a detailed overview of the Study). During the first half of 2014, MPCA staff integrated the Study results, analyzed the data as a whole, received input from the Agency’s Wild Rice Standards