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PROCEEDINGS

1995

CANADIAN MERCURY NETWORK WORKSHOP

heron

Report of a Workshop
held on September 29-30, 1995
at York University, Toronto, Ontario, Canada

Program Coordinators:
Thomas Brydges,Alicia Prez-Fuentetaja and Donald J. McQueen

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TABLE OF CONTENTS

T. BRYDGES. Summary (English).

T. BRYDGES. Summary (French).

TOPIC 1
GROUPS AT RISK

     The management question is to establish whether or not particular
     target groups are affected (either directly or indirectily) by
     mercury toxicity. Both humans and biota may be at risk. Fish
     consumption is the primary human mode of mercury bioaccumulation,
     and aboriginal people are most at risk. The assessment of potential
     risks will be necessary component of future policy development.
    
     A.M. SCHEUHAMMER. Methylmercury Exposure and Effects in Piscivorous
     Birds. D. EVANS. Mercury Levels in Otters. R. WAGEMANN. Mercury
     Levels and Their Spatial and Temporal Trends in
     Arctic Marine Mammals. C. DUMONT. Mercury and Health. The James Bay
     Cree Experience.

TOPIC II
ANTHROPOGENIC VS. NATURAL MERCURY SOURCES

     Management interest in this subject resulted from ongoing
     discussions in Ottawa and at international policy meetings where it
     was suggested that geological sources might be far more important
     than the current literature would lead us to believe. The issue,
     therefore, is to define the relative contributions to the mercury
     pool (on a mean annual basis) of anthropogenic vs natural sources.
    
     The three critical areas that might be expected to contribute
     answers to this question are:
    
     (i) Mass-balance analyses, include: (a) quantification of the size
     of total atmospheric mercury pool, (b) quantification of the rates
     of total mercury dry and wet depostition, (c) quantification of the
     rates of volatilization from water and soil with special reference
     to unique geological features, (d) quantification of natural
     emmissions and natural inventory.
    
     D.B. PORCELLA. The Atmospheric Mercury Pool. W.H. SCHROEDER.
     Environmental Measurments and Results of Mercury
     Volatilization Rates ("Fluxes") from Soil and Lake Surfaces. M.
     AMYOT, D. R. S. LEAN,
     G. MIERLE & D. J. MCQUEEN. Volatilization of Hg from Lakes Mediated
     by Solar Radiation. S. E. LINDBERG. Air / Surface Exchange of
     Mercury Vapor in Forests:
     The Importance of Dry Deposition and Re-Emission
     in the Overall Biogeochemical Cycle of Mercury S. SANG & B. LOURIE.
     Mercury in Ontario: An Inventory of Sources, Uses, and Releases.

     (ii) Mercury dynamics in air and surficial media includes
     information about mercury chemistry and residence time in the
     atmoshpere and surficial media. Specifically, this information can
     be used to cross-check rates of imput to the atmosphere or rates of
     loss from the atmosphere.
    
     P. E. RASMUSSEN. Natural Sources of Mercury: Field Methods for
     Characterizing
     Monitoring Sites. =C5. IVERFELDT. Mercury Chemistry in Air and its
     Atmospheric residence time.

     (iii) Sediment record analyses could possible be used to investigate
     rates of mercury burial. This, in turn, could be used to make
     inferences about the relatively short-term (i.e., 200 yrs.)
     contributions of anthropogenic sources vs. the long-term (i.e.,
     geological time) contributions of natural sources.
    
     W. L. LOCKHART,
     P. WILKINSON,
     R. HUNT &
     R. WAGEMANN. Mercury in Lake and Marine Sediments from Northern
     Canada. D. EVANS. Utility of Sediment Core Profiles to Distinguish
     between
     Anthropogenic and Natural Inputs of Hg. M. LUCOTTE,
     A. MUCCI,
     C. HILLAIRE-MARCEL,
     P. PICKET &
     A. GRONDIN. Anthropogenic Mercury Enrichment in Remote Lakes of
     Northern Qubec (Canada). W. B. COKER. Processes Effecting Mercury
     and Associated Metals in Lake
     Sediment Columns.

TOPIC III
REGIONAL EFFECTS AND CRITICAL LOADS

     The management issue is to investigate the possibility of
     establishing "critical anthropogenic atmospheric loads" on a
     regional basis. This will require information about regional
     atmospheric and natural loading rates and regional features which
     may independently modify the availability of methyl mercury to
     biota.
    
     (i) Mercury regional loading rates
    
     R. BLOXAM. Modelling Mercury Atmospheric Transport, Chemistry and
     Deposition. S. VERMETTE. Mercury Deposition Network. G. F.
     BONHAM-CARTER. Mass Balance Model for Mercury Applied to Huntsville
     Lakes:
     a GIS study.
    
     (ii) Regional features
    
     J. W. M. RUDD. Mercury Cycling in the Boreal Forest at the
     Experimental
     Lakes Area (ELA), Northwestern Ontario. G. MIERLE. Sources of
     mercury to Lakes on the Precambrian Shield
     of Ontario R. G. GARRET. Regional and Large Scale Patterns of
     Mercury Distribution:
     Influential Factors.

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