Comparison of the bioavailability of Cr and Fe bound with natural colloids of different origins and sizes to two marine bivalves |
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Authors: | J -F Pan W -X Wang |
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Institution: | (1) Department of Biology, The Hong Kong University of Science and Technology (HK UST), Clear Water Bay, Kowloon, Hong Kong, China |
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Abstract: | Recent studies have demonstrated the significant role of colloidal microparticles or macromolecules in the biogeochemical
cycling of trace metals in aquatic environments. In this study, the influences of different colloidal organic carbon (COC)
concentrations, colloidal sizes and colloidal origins (estuarine vs coastal) on the bioavailability of two trace metals (Cr
and Fe) to the green mussel Perna viridis and the clam Ruditapes philippinarum were examined under laboratory conditions. Natural colloids were isolated by cross-flow ultrafiltration and were radiclabeled
with 59Fe and 51Cr before being exposed to the mussels and clams. The uptake of colloid-bound Cr and Fe was compared with the uptake of low
molecular weight complexed metals (<1 kDa). Both natural colloid-bound Cr and Fe were bioavailable to the green mussels and
clams. The uptake of both colloidal Cr and Fe by the two bivalves was much higher than that of their counterparts in a low
molecular weight fraction, implying that colloidal binding enhanced considerably the bioavailability of Cr and Fe to the bivalves.
The magnitude to which Cr uptake was enhanced, due to its binding with colloids, was much greater than that of Fe. There was
no significant difference in the measured dry weight concentration factor of the metals between the two COC concentrations.
Similarly, the COC concentration did not influence metal uptake when all the experiments were considered together. There was
generally no major difference in the metal bioavailability between the two different sizes of colloids isolated from the coastal
waters (1–10 kDa and 10 kDa-0.2 μm), whereas metals bound with the larger size colloids isolated from the estuarine waters
were more bioavailable than metals bound with the smaller size colloids. The bioavailability of Cr and Fe bound with the colloids
from estuarine waters was generally lower than those bound with colloids from the coastal waters. This study demonstrated
that the geochemical properties of colloids (origin) and the chemical properties of metals are critical in affecting the bioavailability
of colloid-bound metals to marine bivalves.
Published online: 21 June 2002 |
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