Larry E. Fink, M.S.

Waterwise Consulting, LLC

August 2, 2013

A Scientific Critique of the Proposed Federal Clean Water Act Mercury Total Maximum Daily Load for the State of

Florida

WWC

Abstract Section 303(d)(1)(C) of the U,S. Federal Clean Water Act (CWA) mandates that water

quality-impaired waters be restored to fisheries and recreational uses by calculating a Total Maximum Daily Load (TMDL) based on the capacity of the receiving water to assimilate the pollutant so as not to exceed the applicable Water Quality Standard for each impairing pollutant. The TMDL has to quantify all controllable and uncontrollable point and nonpoint sources of pollution within a mass balance framework, including natural background, and has to take into account seasonal variation in the assimilative capacity with a margin of safety sufficient to compensate for any lack of knowledge about the loading rate-concentration relationship in the receiving water under seasonally appropriate conditions. The TMDL provision of the CWA anticipates a waterbody-specific TMDL, but Florida is proposing a statewide approach, because most of the controllable mercury sources are air emissions sources that originate outside of Florida, and wet and dry atmospheric deposition of inorganic mercury from these regional, continental, and global sources is relatively uniform across the state. The proposed approach requires an 86% reduction to achieve a Water Quality Target equal to the Federal Environmental Protection Agency's Water Quality Criterion of 0.3 ppm methylmercury as total mercury in fish flesh. However, the proposed mercury TMDL for Florida omits an important background source and a substantial controllable nonpoint source. It also sacrifices the most methylmercury-susceptible waters. This paper summarizes the scientific and administrative deficiencies of Florida's statewide approach and strategy for mercury source reduction and proposes the analysis, synthesis, and integration of research, monitoring, and modeling to close the gap between Florida's proposed approach and sound science constrained by the administrative requirements of the CWA.

Introduction Most Florida (FL) inland and all coastal waters

are listed as impaired by a highly toxic form of mercury (Hg), methylmercury (MeHg).

This triggers mandatory Hg source reduction under Section 303(d)(1)(C) of the Federal Clean Water Act (CWA) based on a mass budget, a Total Maximum Daily Load (TMDL).

Mercury-impaired waters in FL and elsewhere are caused primarily by the total mercury (THg) in atmospheric deposition from air sources outside of the control of the CWA and most beyond FL’s borders and outside the United States of America (USA).

Introduction This necessitates a broader approach to

restore the water quality of mercury-impaired waters than the traditional focus on wastewater and runoff source controls.

This is the basis for a statewide approach to Hg TMDL calculation & implementation.

USEPA has already approved Minnesota’s statewide approach, so nothing new here.

FL is proposing to reduce the MeHg concs. in top-predator sport fish by 60% …

Introduction … requiring 86% reduction of controllable air

sources because of a 30% background.

This is a critique of the administrative and scientific deficiencies supporting FL’s proposed statewide Hg TMDL, not the need for mercury source control in the USA or elsewhere.

A version of this presentation with appended supporting information and analysis will be uploaded to WWC website: http://www.waterwiseconsulting.com

WWC

Proposed FL Statewide Hg TMDL Key Administrative

Deficiencies

Key Scientific Deficiencies

Scope: omits estuaries, wetlands

Approach: sacrifices 10% of most-susceptible

WQS Protects Humans & Wildlife: No & No

Consider Seasonality: No

Adequate MOS: No

Correct WLA: No

-- LA > TMDL; WLA = 0

-- no sharing for multi-jurisdiction waters

Monitoring Study: omits sed. pore water; one-time misses seasonality

WQT: derivation errors

Load-Conc. Relationship:

-- no modeling

Sources:

-- omits gw seepage, legacy soils & seds.

-- omits landfill out-gassing & biosolids runoff

Proposed FL Statewide Hg TMDL Key Administrative

Deficiencies

Key Scientific Deficiencies

Scope: omits estuaries, wetlands

Approach: sacrifices 10% of most-susceptible

WQS Protects Humans & Wildlife: No & No

Consider Seasonality: No

Adequate MOS: No

Correct WLA: No

-- LA > TMDL; WLA = 0

-- no sharing for multi-jurisdiction waters

Monitoring Study: omits sed. pore water; one-time misses seasonality

WQT: derivation errors

Load-Conc. Relationship:

-- no modeling

Sources:

-- omits gw seepage, legacy soils & seds.

-- omits landfill out-gassing & biosolids runoff

Focus of this Talk

Key Administrative Deficiencies Water Quality Target (WQT)

The WQT is based on USEPA’s human health protection Water Quality Criterion (WQC) guidance value of 0.3 ppm THg as MeHg in fish flesh published in 2001.

The WQT is not a duly promulgated, enforceable Water Quality Standard (WQS) as prescribed by the CWA …

… so any water quality discharge limits based on a TMDL based on a WQT are also unenforceable.

The WQT of 0.3 ppm THg as MeHg in fish flesh is not adequately protective of human health or all fish-eating wildlife.

Key Scientific Deficiencies Water Quality Target (WQT): Human Health

The FL median background MeHg diet exposure from salt water fish and shellfish > USEPA’s RfD,

so the freshwater fish WQT = 0, not 0.3 ppm.

Instead, FDEP assumes 60% MeHg reduction applies to both fresh and salt water species.

However, when FL background rate is reduced by 60%, WQT = 0.14 ppm THg, not 0.3 ppm THg.

The higher the WQT, the lower the background exposure must be, so if freshwater WQT is 0.3 ppm THg, background must be 0%, …

... but 30% is irreducible load, so it’s a no go!

Key Scientific Deficiencies

FDEP’s Market Basket Approach: Human Health

Probabilistic analysis of exposure via MC using:

-- probability distribution functions (pdfs) of meal composition, size, and freq. for fresh and salt water species to calc. consumption rates

-- pdf of body wt. for child-bearing-age women

-- avg. THg as MeHg concs. in flesh rather than pdfs for each fish and shellfish species.

-- combined to calc. dose rate pdf (mg/Kd-day)

-- FDEP claims median exposure achieves 0.1 ppm THg market basket goal at 99th UCL when fresh & salt water fish MeHg decrease by 60%.

Key Scientific Deficiencies FDEP’s market Basket Approach: Human Health

-- FDEP justified the use of fish THg as MeHg conc. averages rather than conc. pdfs by assuming exposures and effects of high and low fish would balance out over of a woman’s reproductive lifetime.

-- However, if a pregnant woman approaches steady state with the MeHg in her diet by the third trimester, consuming even one highly contaminated fish during her pregnancy could exceed safe levels for the developing fetus, …

… irrespective of what she eats before or after.

Key Scientific Deficiencies FDEP’s market Basket Approach: Human Health

This possibility prompted an evaluation of time-dependent exposure to MeHg from consumption of fish at the WQT for median and subsistence consumers during pregnancy

To simplify the representation:

-- assume all organs exchange rapidly with MeHg conc. in perfusing blood during uptake phase

-- the growth rate of reproduction-related biomass is constant throughout pregnancy

This allows an exact time-dependent solution to the one-compartment model of abs. MeHg dose.

Fetal Exposure Model Equation

CB(t) = [FMR*MAF*FM*AE*(FR*WQT+(FR/RR)*BR*BW)]*[1-exp(-(LN(2)/t1/2 + KG)])

Where:

CB(t) = MeHg conc. in fetal

blood at time t (ug/L)

FMR = ratio umbilical/maternal blood

MAF = MeHg in maternal blood as frac. abs. dose

FM = frac. MeHg as THg in fish flesh

AE = MeHg gut abs. eff.

Where:

FR = fish cons. rate (Kg/day)

WQT = Water Quality Target

RR = ref. fish cons. rate

BR = background rate

BW = body weight

t1/2 = mat. blood half-life

KG = pregnant woman birth wt. gain rate

Fetal Exposure Model Derivation

Model Parameters USEPA FDEP

reference woman (Kg) 70(1) 64(2)

ave. fish cons. rate (g/d) 17.5(1) 21(2)

background rate (ug/Kg-d) 2.70E-2(1) 1.32E-1(2)

half-life in blood (d) 45.5(3) 45.5(3)

blood MeHg (% of abs. dose) 5.9(3) 5.9(3)

blood mass as % BW 7 7

MeHg gut abs. eff. 0.95(3) 0.95(3)

MeHg as THg in flesh 0.95 0.95 (1) USEPA MeHg WQC Document (2001)

(2) FDEP’s Statewide Mercury TMDL Report (2012)

(3) USEPA IRIS Database

Margin of Safety in Fish Flesh MeHg Target Value: Risk from Exposure to Freshwater Fish

Average/Median Consumption Rates: Status Quo

Days of Gestation

1:1 umbilical cord/maternal

blood ratio from USEPA WQC (2001)

Mo

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1:1 umbilical cord/maternal

blood ratio from USEPA WQC (2001)

Margin of Safety in Fish Flesh MeHg Target Value: Risk from Exposure to Freshwater Fish

Average/Median Consumption Rates: Status Quo

Days of Gestation

1:1 umbilical cord/maternal

blood ratio from USEPA WQC (2001)

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1.7:1 median

umbilical cord/maternal

blood ratio (Stern and

Smith, 2003)

Margin of Safety in Fish Flesh MeHg Target Value: Risk from Exposure to Freshwater Fish

Average/Median Consumption Rates: Status Quo

Days of Gestation

1:1 umbilical cord/maternal

blood ratio from USEPA WQC (2001)

Mo

dele

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(u

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3.4:1 95th percentile UCL umbilical cord/maternal

blood ratio (Stern and

Smith, 2003)

Margin of Safety in Fish Flesh MeHg Target Value: Risk from Exposure to Freshwater Fish

Average/Median Consumption Rates: Status Quo

Days of Gestation

Third Trimester Begins: 92% of

steady state

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Margin of Safety in Fish Flesh MeHg Target Value: Risk from Exposure to Freshwater Fish

Average/Median Consumption Rates: Status Quo

Days of Gestation

Median PCB-corrected cognitive deficit for 5th percentile in 7-year old

child tested in Faroe Island epidemiological study: 48 ug/L MeHg

(USEPA IRIS Database)

Mo

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Margin of Safety in Fish Flesh MeHg Target Value: Risk from Exposure to Freshwater Fish

Average/Median Consumption Rates: Status Quo

Days of Gestation

Margin of Safety Not Adequate

for Subsistence Consumers

10-fold

Margin of Safety for Nat’l Ave.

Consumers built into

USEPA RfD =

0.1 ug/Kg-d

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Margin of Safety in Fish Flesh MeHg Target Value: Risk from Exposure to Freshwater Fish

Average/Median Consumption Rates: Status Quo

Days of Gestation

Margin of Safety Not Adequate

for Subsistence Consumers

Margin of Safety Not Adequate at 95th UCL

for FL Median

Consumers under

status quo

Mo

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(u

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Margin of Safety in Fish Flesh MeHg Target Value: Risk from Exposure to Freshwater Fish

Average/Median Consumption Rates: FL Hg TMDL

Days of Gestation

Margin of Safety Not Adequate

for Subsistence Consumers

Margin of Safety Not Adequate at 95th UCL

for FL Median

Consumers under 60% THg load reduction

Mo

dele

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(u

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Margin of Safety in Fish Flesh MeHg Target Value: Risk from Exposure to Freshwater Fish

Subsistence Consumption Rate: Status Quo

Days of Gestation

Margin of Safety Not Adequate

for Subsistence Consumers

Margin of

Safety Non-Existent at

95th UCL for Median

Consumers under

status quo

Margin of

Safety Non-Existent at

95th UCL for Median

Consumers under

status quo

Margin of

Safety Non-Existent at

95th UCL for Median

Consumers under

status quo

Margin of

Safety Non-Existent at

95th UCL for Median

Consumers under

status quo

Margin of

Safety Non-Existent at

95th UCL for Median

Consumers under

status quo

Margin of

Safety Non-Existent for

all FL SubsistenceConsumers

under status quo

Subsistence Fish Consumption Rate = 0.135 kg/day

(Holliman and Newman 2011)

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Margin of Safety in Fish Flesh MeHg Target Value: Risk from Exposure to Freshwater Fish

Subsistence Consumption Rate: FL Hg TMDL

Days of Gestation

Margin of Safety Not Adequate

for Subsistence Consumers

Margin of

Safety Non-Existent at

95th UCL for Median

Consumers under

status quo

Margin of

Safety Non-Existent at

95th UCL for Median

Consumers under

status quo

Margin of

Safety Non-Existent at

95th UCL for Median

Consumers under

status quo

Margin of

Safety Non-Existent at

95th UCL for Median

Consumers under

status quo

Margin of

Safety Non-Existent at

95th UCL for Median

Consumers under

status quo

Margin of

Safety Non-Existent for

all FL SubsistenceConsumers under 60% THg load reduction

Mo

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Key Conclusions Water Quality Target: Human Health

0.3 ppm WQT is not fully protective of median consumers under status quo or proposed FL 60% THg TMDL load reduction for target lake.

The developing fetus of subsistence consumers is at unacceptable risk of cognitive deficit under status quo and will not be adequately protected under proposed 60% FL THg TMDL load reduction.

The use of averages rather than lognormal pdfs in the probabilistic exposure analysis suppresses exposure extremes that have real consequences for fetal development

Key Recommendations Water Quality Target: Human Health Rerun market basket MC analysis using this

exposure model at steady-state with -- pdfs for fresh and salt water fish and

shellfish meal sizes and THg as MeHg concs. -- pdfs for maternal weight, maternal blood

half-life & umbilical cord/maternal blood ratio -- develop a separate conc. pdf for each

distinct freshwater fish size category and … -- evaluate the effect of high-size selection

bias in sport fish meals using size-conc. relationships for bluegill and largemouth bass from statewide study

Key Recommendations Water Quality Target: Human Health

Expand diet MeHg exposure scenario to include nursing infant with pdfs for MeHg conc. ratio of maternal blood to mother’s milk, mother’s milk production and consumption rates, and infant body wt and growth rate

Reevaluate claim that the FL median consumer will be protected at MeHg dose rate equivalent to 0.1 ppm THg as MeHg at 99th percentile UCL when fresh and salt water fish and shellfish THg as MeHg concs. are both reduced by 60% without and with nursing scenario.

Key Recommendations Water Quality Standard: Human Health

Promulgate enforceable freshwater WQS for fish flesh to protect human health for subsistence consumers

Promulgate enforceable WQS for whole fish to protect sensitive, fish-eating wildlife

Develop and implement enforceable statewide Hg TMDL based on enforceable WQS

Use enforceable TMDL as leverage to implement and enforce Minamata Convention: http://en.wikipedia.org/wiki/Minamata_Convention_on_Mercury

Policy Implications MeHg is a growing threat to the public health,

safety and welfare, esp. indigenous peoples and ethnic groups with a fish-rich diet

... but growing wealth disparity will increasingly shift the problem to the growing ranks of the disadvantaged among ethnic minorities and then majorities, as more people are forced to subsist on fish.

Net mercury methylation and bioaccumulation are likely to increase with global warming.

Expedite the Minamata Convention.

Acknowledgements Carl Miles, Ph.D. (1951-2000): He

implemented the So. FL Water Management District’s Everglades mercury monitoring & R&D programs & his well-designed equilibrium and kinetics studies of methylmercury sorption to algae species are still classics.

Tom Atkeson, Ph.D: Florida Dept. of Env. Protection Mercury Coordinator, 1991-2011, an articulate spokesman for sound science in support of sound policy-making with a budget to match the breadth and depth of his vision.

Acknowledgements Don Axelrad, Ph.D: who picked up the torch

from Dr. Atkeson and ran the last leg with brilliance and determination, before FDEP walked away from its world-class mercury monitoring, R&D and modeling program.

Aaron Higer: USGS-Retired, who said if you get mercury right, everything else must be right, then made sure the Everglades got the USGS scientists needed to get mercury right, including Dave Krabbenhoft, Cynthia Gilmour, Bill Orem, George Aiken, Judson Harvey, Ron Oremland, and Mark Marvin-DiPasquale

References Axelrad et al. 2005-13. Mercury and Sulfur Monitoring, Research and

Environmental Assessment for South Florida (Everglades). South Florida Ecosystem Report. So. Fla. Water Manage. District, West Palm Beach, FL

http://my.sfwmd.gov/portal/page/portal/xweb%20about%20us/agency%20reports

Atkeson, T.A. and D. Axelrad. 2003.The Everglades Mercury TMDL Pilot Study: Final Report to USEPA, ORD-Air, RTP, NC

http://water.epa.gov/lawsregs/lawsguidance/cwa/tmdl/everglades_fs.cfm

Evans, D.W. and P.H. Crumley. 2005. Mercury in Fish in Eastern Florida Bay …

http://aquaticcommons.org/2099/1/01-4940-Evans.pdf

Fink, Larry E. 2012. Comment Letter on FDEP’s Proposed Statewide Hg TMDL for the State of Florida

Not accessible on Florida Dept. Env. Protection Hg TMDL website

References Florida Dept. of Env. Prot. 2012. Draft Statewide Mercury TMDL

Report to USEPA Region 4

http://www.dep.state.fl.us/water/tmdl/draft_tmdl.htm#mercury

Florida Dept. of Health

http://www.doh.state.fl.us/floridafishadvice/

http://www.doh.state.fl.us/environment/community/fishconsumptionadvisories/MEFG.htm

Florida Fish & Wildlife Commission http://myfwc.com/research/saltwater/health/mercury/faq/

Houck, O.A. 2002. The Clean Water Act TMDL Program: Law, Policy and Implementation. Env. Law Institute, Washington, DC.

http://www.amazon.com/Clean-Water-TMDL-Program-Implementation/dp/1585760382

Holliman, E.L. and M.C. Newman. 2011. Expanding perceptions of subsistence fish consumption: …Sci. Tot. Environ. e-pub.

References Lange, T. 1996. FL Fish and Wildlife Conservation Commission.

Personal communication.

Lindberg SE and JL Price. 1999. Airborne emissions of mercury from municipal landfill operations: A short-term measurement study in Florida,” JAWMA, 49:520-532.

Lindberg, S.E., D. Wallschlaeger, E. Prestbo, N. Bloom, J. Price, and D. Reinhart. 2001. Methylated mercury species in municipal waste landfill gas sampled in Florida. Atm. Environ. 35:4011-4015.

Lindberg, S., G. Southworth, M. Bogle, T. Blasing, H. Zhang, T. Kuiken, D. Wallschlaeger, J. Price, D. Reinhart, H. Sfeir, J. Owens, and K. Roy. 2005. Airborne emissions of mercury from municipal solid waste-I: New measurements from six operating landfills in Florida. JAWMA. 55:859-869

Rumbold, D. 2012. Comment Letter on FDEP’s Proposed Statewide Hg TMDL for the State of Florida: Not accessible on FDEP’s Hg TMDL website

References Rumbold, D. et al. 2010: Source identification of Florida Bay’s

Mercury Problem … http://www.evergladeshub.com/lit/pdf11/Rumbold11estuarCoasts34-494-513-HgFLbayDeposition.pdf

Sacks, L.A. , A. Swankar and T.M. Lee. 1998. Estimating Ground-water Exchange with Lakes … USGS Water-Resources Investigations Report. 98-4133. http://fl.water.usgs.gov/PDF_files/wri98_4133_sacks.pdf

Southworth, G.R.; Lindberg, S.E.; Bogle, M.A; Zhang, H., Kuiken, T. Price, J.; Reinhart, D.; Sfeir H. 2005. Airborne emissions of mercury from municipal solid waste- II: potential losses of airborne mercury prior to landfill. JAWMA. 55: 870-877

Stern, A.H. and A.E. Smith. 2003. An Assessment of the Cord Blood-Maternal Blood MeHg Ratio: Implications for Risk Assessment

http://www.questia.com/library/1G1-109567746/an-assessment-of-the-cord-blood-maternal-blood-methylmercury

References USEPA. TMDL Regulations and Guidance: Mercury-Specific

http://water.epa.gov/lawsregs/lawsguidance/cwa/tmdl/mercury/upload/2008_10_01_tmdl_pdf_document_mercury_tmdl_elements.pdf

USEPA. TMDL Technical Support

http://water.epa.gov/lawsregs/lawsguidance/cwa/tmdl/techsupp.cfm

USEPA.ORD. Water Quality Models and Modeling Technical Guidance

http://water.epa.gov/scitech/datait/models/library_index.cfm

USEPA. 1995. Great Lakes Water Quality Initiative Technical Guidance for Derivation of Site-Specific Wildlife Water Quality Criteria

http://www.epa.gov/gliclear/docs/usepa_wildlife_tsd.pdf

USEPA. 1997. Mercury Study Report to Congress http://www.epa.gov/hg/report.htm

USEPA IRIS Database. http://www.epa.gov/iris/subst/0073.htm

References USEPA. TMDL Regulations and Guidance: General

http://water.epa.gov/lawsregs/lawsguidance/cwa/tmdl/guidance.cfm

USEPA. 2001. Human Health Criteria: Methylmercury in Fish Water Quality Criteria Document

http://water.epa.gov/scitech/swguidance/standards/criteria/aqlife/methylmercury/upload/2009_01_15_criteria_methylmercury_mercury-criterion.pdf

… Implementation Guidance http://water.epa.gov/scitech/swguidance/standards/criteria/aqlife/methylmercury/index.cfm

USGS General Mercury Information Page

http://www.usgs.gov/mercury/

Young, J.F., W. Wosilait and R.H. Luecke. 2001. Analysis of MeHg Disposition in Humans Using a PBPK Model and Animal Pharmacokinetic Data. J. Toxicol Env. Health. Part A. 63. 9-52

http://www.ncbi.nlm.nih.gov/pubmed/11346132

Records Requests to FDEP Please provide any formal responses to comments

received from Waterwise Consulting, LLC, during public comment period that closed 08/27/12. [None]

Please provide THg, Hg(0), and MeHg mass loads, loading rates, and/or mass fluxes measured, estimated, or modeled for any waterbody included in one-time statewide mercury monitoring study. [None, None, None]

Please provide all records of internal communications regarding WWC’s public comments on proposed administrative action [CDs received 07/19/13]

Clean Water Act TMDL Provision

“Section 303(d)(1)(C): Each State shall establish for the waters identified in paragraph (l)(A) of this subsection, and in accordance with the priority ranking, the total maximum daily load, for those pollutants which the Administrator identifies under section 304(a)(2) as suitable for such calculation. Such load shall be established at a level necessary to implement the applicable water quality standards with seasonal variations and a margin of safety which takes into account any lack of knowledge concerning the relationship between effluent limitations and water quality.”

http://water.epa.gov/lawsregs/guidance/303.cfm

Wildlife Water Quality Criteria Derivation: Trophic Level 3 and 4 Whole Fish-Equivalents

WholeT4 Fish-Equivalent Florida’s Statewide 0.3 ppm

THg as MeHg WQT in Fish Flesh to Protect Human Health: 0.21

ppm THg

TH

g a

s M

eH

g in

Wh

ole

Fis

h

(m

g/

Kg

wet

wt.

) Whole T3 Fish-

Equivalent Florida’s Statewide 0.3 ppm

THg as MeHg WQT in Fish Flesh to Protect Human Health: 0.11

ppm THg

TH

g A

tm.

Dep

. Lo

ad

Red

ucti

on

Req

uir

ed

fro

m

Co

ntr

ollab

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ir E

mis

sio

ns S

ou

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percen

t)*

90th % Largemouth Bass THg Conc. in Flesh (ppm wet wt.)

TMDL WQT vs. THg Atmospheric Deposition Load Reduction Non-Linearities: Sensitivity to Choice of WQT

96% THg Load

Reduction Required

Statewide inland water body average THg as MeHg in LMB

flesh: 0.91 ppm THg

TH

g A

tm.

Dep

. Lo

ad

Red

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on

Req

uir

ed

fro

m

Co

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ollab

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ir E

mis

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90th % Largemouth Bass THg Conc. in Flesh (ppm wet wt.)

TMDL WQT vs. THg Atmospheric Deposition Load Reduction Non-Linearities: Sensitivity to Choice of WQT

107% THg Load

Reduction Required

95th percentile UCL of lognormally

distributed THg as MeHg in LMB flesh:

1.04 ppm THg

95th percentile LCL of lognormally distributed MeHg as

THg in LMB flesh to correct for sampling error to ensure compliance with WQT:

0.26 ppm THg

Statewide inland water body average THg as MeHg in LMB

flesh: 0.91 ppm THg

Policy Issues Legal

Where in the CWA does it give USEPA:

-- the authority to regulate air emissions sources for purposes of TMDL development, implementation or enforcement, rather than including them as an uncontrollable mass loading rate in the LA?

-- the option of ignoring the contaminated sediment contribution to the LA, when there is no plan or feasibility to remove, stabilize, or offset the sediment load contribution?

Policy Issues Resource Management Time-To-Recovery Should a regulatory agency be required to impose

greater load reductions, remediations, or offsets to expedite recovery of impaired ecosystems that respond more slowly?

… thereby providing a greater MOS for water

resources that respond more rapidly?

Should the regulatory agency calculate source reductions to protect the representative most-susceptible, least-responsive water resource?

Technical Issues

Simplifying Assumptions:

All Water Resources Are At Steady State

What internal state criteria must a seasonally dynamic aquatic ecosystem with seasonally dynamic external and internal mercury species fluxes and load-conc. relationships meet to be considered to be oscillating normally around a steady-state condition?

What, where, when, how frequently, and for how long must one monitor such an aquatic ecosystem to establish that it has met those criteria?

Technical Issues Simplifying Assumptions:

All Water Resources Are At Steady State

Do large-bodied, slow-growing, top-predator fish with low MeHg depuration rates integrate and average out the intra- and inter-annual variations in MeHg concs. in water, plants, and prey or accumulate and lock-in their unique foraging histories, increasing rather than decreasing the variability of their body burdens in each size, age, and sex cohort?

Technical Issues Simplifying Assumptions:

All Water Resources Are At Steady State

What are the appropriate lag-times for pairing the MeHg concentrations in various aquatic media and various aquatic biota for purposes of regression model-building of the mercury species load-fish MeHg conc. relationship?... mechanistic model calibration and validation?