82
L.D. Lacerda and W. Salomons
Table 3. Comparison between root and shoot mercury concentrations (fIg g~ ') in aquatic
macrophytes from gold mine tailings
Species
Shoot
Root
Root:shoot
Reference
Equisetum fluviatile,
0.45
0.47
1.04
Lane et al. (1988)
Nova Scotia, Canada
Juncus articulatus,
0.55
2.69
4.89
Lane et al. (1988)
Nova Scotia, Canada
Juncus pelocarpus,
0.54
6.11
11.13
Lane et al. (1988)
Nova Scotia, Canada
Dulichium arundinaceum,
0.19
0.67
3.53
Lane et al. (1988)
Nova Scotia, Canada
Leerzia oryzoides,
0.18
1.56
8.67
Lane et al. (1988)
Nova Scotia, Canada
Eichornia azurea,
0.06
0.37
6.17
CETEM (1992)
Teles Pires mines, South Amazon
Potenderia Lanceolata,
0.14
Lacerda et al. (1991 a)
central Brazil
macrophyte Eichornia crassipes from gold mining sites in South Amazon
(CETEM 1992).
The higher content of Hg in roots relative to shoots in freshwater macrophytes
is a well-known phenomenon, and also occurs for other trace metals and
terrestrial plants. (Kelly 1988). Roots act as an efficient barrier to Hg uptake.
Mercury can complex to sulfydril groups at the root surface (Siegel 1973) and
adsorb to deposited iron and manganese plates (Kozlowski 1984; Crowder and
StCyr 1991; Gambrell 1994). Also, release of Hgo vapor from shoots has been
reported for many plant species (Siegel et al. 1974; 1985; 1987) and results in less
Hg in the leaves (Table 3).
The understanding of the role played by vegetation of gold mine tailings is
hampered by lack of information on almost all significant mining sites. Since
most of these operations are taking place in the tropics, and tailings are left
frequently still surrounded by pristine ecosystems, it is of extreme urgency to
gather more information on the role played by vegetation on the migration of
mercury contamination from gold and silver mine tailings.
5.3
Animals
Some few animal species other than fish have been analyzed in Hg-contaminated
sites from gold mining areas, in order to find biological monitors of Hg
contamination. Among them, freshwater snails have been studied more
intensively, since these organisms proved to be very good monitors in many
trace metal contamination situations.
Freshwater snails are omnivorous animals, feeding on bottom sediments and
plant surfaces. Therefore Hg concentrations are generally higher in the guts of
these animals than in muscle tissues. Figure 2 shows the distribution of Hg in the
L.D. Lacerda and W. Salomons
Table 3. Comparison between root and shoot mercury concentrations (fIg g~ ') in aquatic
macrophytes from gold mine tailings
Species
Shoot
Root
Root:shoot
Reference
Equisetum fluviatile,
0.45
0.47
1.04
Lane et al. (1988)
Nova Scotia, Canada
Juncus articulatus,
0.55
2.69
4.89
Lane et al. (1988)
Nova Scotia, Canada
Juncus pelocarpus,
0.54
6.11
11.13
Lane et al. (1988)
Nova Scotia, Canada
Dulichium arundinaceum,
0.19
0.67
3.53
Lane et al. (1988)
Nova Scotia, Canada
Leerzia oryzoides,
0.18
1.56
8.67
Lane et al. (1988)
Nova Scotia, Canada
Eichornia azurea,
0.06
0.37
6.17
CETEM (1992)
Teles Pires mines, South Amazon
Potenderia Lanceolata,
0.14
Lacerda et al. (1991 a)
central Brazil
macrophyte Eichornia crassipes from gold mining sites in South Amazon
(CETEM 1992).
The higher content of Hg in roots relative to shoots in freshwater macrophytes
is a well-known phenomenon, and also occurs for other trace metals and
terrestrial plants. (Kelly 1988). Roots act as an efficient barrier to Hg uptake.
Mercury can complex to sulfydril groups at the root surface (Siegel 1973) and
adsorb to deposited iron and manganese plates (Kozlowski 1984; Crowder and
StCyr 1991; Gambrell 1994). Also, release of Hgo vapor from shoots has been
reported for many plant species (Siegel et al. 1974; 1985; 1987) and results in less
Hg in the leaves (Table 3).
The understanding of the role played by vegetation of gold mine tailings is
hampered by lack of information on almost all significant mining sites. Since
most of these operations are taking place in the tropics, and tailings are left
frequently still surrounded by pristine ecosystems, it is of extreme urgency to
gather more information on the role played by vegetation on the migration of
mercury contamination from gold and silver mine tailings.
5.3
Animals
Some few animal species other than fish have been analyzed in Hg-contaminated
sites from gold mining areas, in order to find biological monitors of Hg
contamination. Among them, freshwater snails have been studied more
intensively, since these organisms proved to be very good monitors in many
trace metal contamination situations.
Freshwater snails are omnivorous animals, feeding on bottom sediments and
plant surfaces. Therefore Hg concentrations are generally higher in the guts of
these animals than in muscle tissues. Figure 2 shows the distribution of Hg in the