Descrição
The upper limit concentrations of metals
established by international legislations for dredged sediment
disposal and soil quality do not take into consideration
the properties of tropical soils (generally submitted
to more intense weathering processes) on metal
availability and ecotoxicity. Aiming to perform an evaluation
on the suitability of these threshold values in
tropical regions, the ecotoxicity of metal-contaminated
dredged sediment from the Guanabara Bay (Rio de
Janeiro, Brazil) was investigated. Acute and avoidance
tests with Eisenia andrei were performed with mixtures
of dredged sediment with a ferralsol (0.00, 6.66, 13.12,
19.98, and 33.30 %) and a chernosol (0.00, 6.58, 13.16,
19.74, and 32.90 %). Mercury, lead, nickel, chromium,
copper, and zinc concentrations were measured in test
mixtures and in tissues of surviving earthworms from
the acute tests. While ferralsol test mixtures provoked
significant earthworm avoidance response at concentrations
≥13.31 %, the chernosol mixtures showed significant
avoidance behavior only at the 19.74 % concentration.
The acute tests showed higher toxicity in
ferralsol mixtures (LC50=9.9 %) compared to
chernosol mixtures (LC50=16.5 %), and biomass increased
at the lowest sediment doses in treatments of
both test soils. Most probably, the expansive clay minerals
present in chernosol contributed to reduce metal
availability in chernosol mixtures, and consequently, the
ecotoxicity of these treatments. The bioconcentration
factors (BCF) for zinc and copper were lower with
increasing concentrations of the dredged sediment, indicating
the existence of internal regulating processes.
Although the BCF for mercury also decreased with the
increasing test concentrations, the known no biological
function of this metal in the earthworms metabolism
lead to suppose that Hg measured was not present in
bioaccumulable forms. BCFs estimated for the other
metals were generally higher in the highest dredged
sediment doses. Ricardo Cesar and Juan Colonese were
supported by grants from the National Brazilian Council for
Scientific and Technological Development (CNPq) and CAPES
(Coordination for the Improvement of Higher Level -or
Education- Personnel—Sandwich Doctorate).
; Natal-da-Luz, Tiago 
