Environmental Engineering Reference
In-Depth Information
10.3 Reviewed studies
Following a gold mine disaster in Romania, heavy metal content (Pb, Cd, Cr, Ni, Hg, As)
was determined in silver carp, crawfish, sediment, and water (Francuski et al, 2000).
Samples were collected from the Tisa River on February 28, 2000, upstream from the dam
near Novi Becej in Rumania. Results showed heavy metals in all samples were significantly
increased especially the Cd concentration in crawfish, which was three times higher than the
maximal allowed concentration.
A study was performed to investigate direct and direct plus trophic contamination routes of
crawfish (Astacus astacus) by inorganic Hg(II) or methylmercury (MeHg) (Simon and
Boudou, 2001). Direct exposure was based on low contamination conditions, 300 and 30
ng/L in the dissolved phase, respectively, during 30 days at 208C. Trophic exposure was
based on daily consumption of the Asiatic clam (Corbicula fluminea), previously
contaminated during 40 days with similar exposure conditions. The Hg concentrations in
the bivalves were very similar: 1,451+287 ng/g for Hg(II) and 1,346+143 ng/g for MeHg. In
the crustaceans, Hg bioaccumulation was determined at the whole-organism level and in
eight organs (gills, stomach, intestine, hepatopancreas, tail muscle, green gland, carapace,
and hemolymph), after 15 and 30 days of exposure. Analysis of the results showed marked
differences between Hg(II) and MeHg accumulation in favor of MeHg: for the direct route,
the ratio between metal concentrations was close to 8; for the trophic route, no significant
increase in Hg accumulation
was observed for Hg(II) even when the ratio between Hg concentration in the direct plus
trophic contamination route and Hg concentration in the direct contamination route was 1.6
for MeHg, with an estimated trophic transfer rate close to 20%. Mercury organotropism was
also specifically connected to the exposure conditions, especially at the biological barrier
level according to the route of exposure: gills and carapace for the direct route and digestive
tract including hepatopancreas for the trophic route.
Another study evaluated potential human and ecological risks associated with metals in fish
and crawfish from mining in the Tri-States Mining District (TSMD) in northeast Oklahoma
(Schmitt et al, 2006). Crawfish (Orconectes spp.) and fish of six frequently consumed species
(common carp (Cyprinus carpio) ; channel catfish (Ictalurus punctatus) ; flathead catfish
(Pylodictis olivaris) ; largemouth bass (Micropterus salmoides); spotted bass (M. punctulatus) ;
and white crappie (Pomoxis annularis) were collected in 2001-2002 from the Oklahoma
waters of the Spring River (SR) and Neosho River (NR), which drain the TSMD. Samples
from a mining-contaminated site in eastern Missouri and from reference sites were also
analyzed. Individual fish were prepared for human consumption in the manner used locally
by Native Americans (headed, eviscerated, and scaled) and analyzed for Pb, Cd, and Zn.
Whole crawfish were analyzed as composite samples. Metals concentrations were typically
higher in samples from sites most heavily affected by mining and lowest in reference
samples. Within the TSMD, most metal concentrations were higher at sites on the SR than
on the NR and were typically highest in common carp and crawfish. Higher concentrations
and greater risk were associated with fish and crawfish from heavily contaminated SR
tributaries than the SR or NR mainstreams. Based on the results of this and previous studies,
the human consumption of carp and crawfish could be restricted based on current criteria
for Pb, Cd, and Zn. Overall, the wildlife assessment is consistent with previously reported
biological effects attributed to metals from the TSMD. The results demonstrated the
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