Xl. Otero et al., Bioaccumulation of heavy metals in thionic fluvisols by a marine polychaete: The role of metal sulfides, J ENVIR Q, 29(4), 2000, pp. 1133-1141
Bioavailable heavy metals have been widely studied in recent years because
of their toxicity to natural ecosystems. Despite the number of studies tarr
ied out, relatively little is known about the metal fraction that is biolog
ically available. In this study, we analyzed seasonal concentrations of aci
d-volatile sulfide (AVS) as well as heavy metals associated with the reacti
ve (soluble in 1 M HCI) and pyrite (soluble in HNO3) fractions of the soils
of three salt marshes in the ria of Ortigueira (NW Iberian Peninsula). Hea
vy metal concentrations in polychaete worms (Nereis diversicolor) collected
from each salt marsh were also determined and compared with metal contents
in the different fractions of the soil. We did not find a relationship bet
ween the concentration of total metal or metal incorporated into the reacti
ve fraction in the soil and the tissue-metal concentration in N. diversicol
or. The results appear to indicate that this species preferentially accumul
ates metals associated with reduced forms of sulfur (pyrite and presumably
AVS). Oxidation of these metal sulfides would lead to release of Cu and Ni
into interstitial water and they would then be readily available to be take
n up by these organisms, either by absorption through the body surface or a
cross the digestive tract.