Adrienne Ethier*, Joseph Atkinson, Joseph DePinto and David Lean.

Adrienne Ethier*, Joseph Atkinson, Joseph DePinto and David Lean

HERMESHERMES

Hermes (Roman: Hermes (Roman: Mercury) is the Mercury) is the Greek god of Greek god of boundaries and boundaries and travelers who cross travelers who cross them. A messenger them. A messenger with a winged hat with a winged hat and shoes. and shoes.

Similar to the symbol for Similar to the symbol for woman (woman (♀♀). Pregnant ). Pregnant women are the most at risk women are the most at risk group for Hg exposure since group for Hg exposure since Hg can cross placental Hg can cross placental membrane causing birth membrane causing birth defects and neurological defects and neurological damage in fetus.damage in fetus.

The symbol for Mercury The symbol for Mercury may represent the may represent the caduceus staff or the circle caduceus staff or the circle might be mercurymight be mercury’’s head s head and the two and the two ““hornshorns”” might might be wings on his head.be wings on his head.

Hg concentration and / or flux rates are commonly measured in the environment

*** not interconversion or reaction rates among Hg species

Attempts are often made to relate these measurements to other physical and / or chemical parameters of the watershed or lake (e.g. DOC versus Hg)

ReactionReaction Hg is conservedHg is conserved

HgHg00 : Elemental Hg: Elemental HgMain species found in atmosphereMain species found in atmosphere

MeHg MeHg : Methyl Hg: Methyl HgOrganic fraction of Hg that Organic fraction of Hg that bioaccumulates in food websbioaccumulates in food webs

Hg(II)Hg(II) : Inorganic Hg : Inorganic HgMain species found in Main species found in sediment and watersediment and water

Log10 (Suspended particulate matter (mg L-1)) = 1.56 x Log (Total phosphorus (μg L-1)) – 1.69

Log10 (Suspended particulate matter (mg L-1)) = -1.123 x (Log Secchi depth (m)) +0.993

Solid settling rate (g m-2day-1) = 1.04 - (0.07 x Mean depth (m))

Resuspension rate (% of settling) = 90 x (850 - ((Mean depth (m) - 8.5) x 70)) / 850

Vapour Pressure (Pa) = P1 x exp (- (ΔHvap / R) (1 / T2 – 1 / T1))

Water solubility (mg L-1) = 8000000 x 10 (-122.911 + (4475.3 / T2) + (40.2205 x Log (T2)))

Ln (Concentration of Hg in inflow water (ng L-1)) = 2.02 – 0.063 x Ln (Watershed area (km2) x 100)

Log10 (Sediment MeHg : THg) = -1.9025 - 0.0086 x TOC (%) + 0.0011 x Redox potential (mV)

For summer and DOC < 20 mg L-1: Water MeHg : THg = (-0.4 + 0.128 x DOC (mg L-1)) / (0.48 x DOC (mg L-

1))

Water inflow MeHg : THg = 10 ((% Wetland x 0.056)-1.12) / e (2.02 – 0.063 x Ln (Watershed area (km2) x 100))

Sediment with TOC < 20%: sediment THg (ng g-1) = 4.4215 x TOC (%) + 16.225

Water with DOC < 20 mg L-1: water THg (ng L-1) = 0.48 x DOC (mg L-1)

Model Model input input driving driving variablesvariables

Location Location or lake-or lake-specific specific variablesvariables

ESTIMATION METHODSESTIMATION METHODS

MODEL OUTPUT ‘DOUBLE-CHECK’MODEL OUTPUT ‘DOUBLE-CHECK’

MeHg : THg RATIOSMeHg : THg RATIOS

clickclick

HERMESHERMES

No rate constants usedNo rate constants used

ModelModel ComparisonComparisonLOTOX 2LOTOX 2

Table 5. Contribution to variance for the model input variables altered during application.

Contribution to variance in model output

ΣHg concentration ΣHg concentrationInput variable in water (%) in sediment (%)

Concentration of Hg in air (ng/m3) 63.93 62.98Rain rate (m/year) 17.76 17.10

Concentration of Hg in inflow water (ng/L) <0.1 <0.1

Water inflow rate (m3/h) <0.1 <0.1

Sediment deposition velocity (g/m2/day) 17.60 15.67

Suspended particulate matter (mg/L) 0.26 3.81Inflow suspended particulate matter (mg/L) <0.1 <0.1

Year-round mean temperature (oC) 0.45 0.43Total 100 100

NOTE: surface area, water volume and mean depth are fixed lake parameters and

were therefore not included in uncertainty analysis.

Sm

all

Sm

all

Lar

ge L

arge

Lake Ontario versus smaller lakesLake Ontario versus smaller lakes

Model theory and development:Model theory and development:Ethier, A.L.M., Mackay, D., Toose-Reid, L.K., O’Driscoll, N.J., Scheuhammer, A.M. The development and application of a mass balance model for mercury (total, elemental and methyl) using data from a remote lake (Big Dam West, Nova Scotia, Canada) and the multi-species multiplier method. Appl Geochem 2008; 23(3): 467-481.

Model estimation methods:Model estimation methods:Ethier, A.L.M., Lean, D.R.S., Scheuhammer, A.M., Bodek, T., Sosso-Kolle, K. Predicting mercury concentrations and fluxes in the water column and sediment of lakes with a limited dataset. Environ Toxicol & Chem in press – available online