Effect of Dissolved Organic Matter on the Uptake of Trace Metals by American Oysters
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- 作者：Laodong Guo ; Becky J. Hunt ; Peter H. Santschi ; and Sammy M. Ray
- 刊名：Environmental Science & Technology
- 出版年：2001
- 出版时间：March 1, 2001
- 年：2001
- 卷：35
- 期：5
- 页码：885 - 893
- 全文大小：241K
- 年卷期：v.35,no.5(March 1, 2001)
- ISSN：1520-5851
文摘
To examine the effects of dissolved organic matter onmetal bioavailability, uptake of trace metals (Cd, Co, Hg,Cr, Ag, Zn) by American oysters (Crassostrea virginica) wascompared between treatments with different dissolvedorganic carbon (DOC) concentrations and contrasting lowmolecular weight (LMW, 1 kDa) and high molecularweight (HMW, 1 kDa-0.2 
m) DOC fractions, using radiotracertechniques and short-term exposure experiments. Uptakerate constants (mL g-1 h-1) of metals, in general,increased with increasing DOC concentrations, with aninitial decrease at lower DOC concentrations. Oyster dryweight concentration factors (DCF, mL g-1), determined atthe end of exposure experiments (8 h), also increasedfor Cd, Co, Cr, Ag, and Zn, but decreased for Hg, withincreasing DOC concentrations. Changes of metal uptakerate constants and DCF values with DOC concentrationsuggest that metal uptake pathways by American oystersvary from predominantly uptake (by diffusion of neutral)of free ionic, inorganically complexed, and LMW organicligand complexed metals at very low DOC concentration todirect ingestion and digestion of HMW or colloidallycomplexed metals at higher DOC concentrations. Measuredpartition coefficients (Kc) between dissolved and colloidalphases were comparable between metals, ranging from105.12 to 105.75 mL g-1. However, DCF values and uptake rateconstants differed considerably between metals, withthe highest DCF values and uptake rate constants foundfor B-type metals, e.g., Ag, Hg, Zn, and Cd, and the lowestones for several intermediate-type metals (e.g., Co, Cr).Metal types and thus the interaction of metals with organicligands, such as strong complexation of B-type metalswith S-containing organic ligands, may play an importantrole in the bioavailability and toxicity of metals to aquaticorganisms. Differences in metal uptake in contrastingLMW and HMW DOC treatments suggest a generallydepressed bioavailability of colloidally complexed metalsat low DOC concentration (0.5 ppm) but a generally enhanceduptake at higher DOC concentrations.
m) DOC fractions, using radiotracertechniques and short-term exposure experiments. Uptakerate constants (mL g-1 h-1) of metals, in general,increased with increasing DOC concentrations, with aninitial decrease at lower DOC concentrations. Oyster dryweight concentration factors (DCF, mL g-1), determined atthe end of exposure experiments (8 h), also increasedfor Cd, Co, Cr, Ag, and Zn, but decreased for Hg, withincreasing DOC concentrations. Changes of metal uptakerate constants and DCF values with DOC concentrationsuggest that metal uptake pathways by American oystersvary from predominantly uptake (by diffusion of neutral)of free ionic, inorganically complexed, and LMW organicligand complexed metals at very low DOC concentration todirect ingestion and digestion of HMW or colloidallycomplexed metals at higher DOC concentrations. Measuredpartition coefficients (Kc) between dissolved and colloidalphases were comparable between metals, ranging from105.12 to 105.75 mL g-1. However, DCF values and uptake rateconstants differed considerably between metals, withthe highest DCF values and uptake rate constants foundfor B-type metals, e.g., Ag, Hg, Zn, and Cd, and the lowestones for several intermediate-type metals (e.g., Co, Cr).Metal types and thus the interaction of metals with organicligands, such as strong complexation of B-type metalswith S-containing organic ligands, may play an importantrole in the bioavailability and toxicity of metals to aquaticorganisms. Differences in metal uptake in contrastingLMW and HMW DOC treatments suggest a generallydepressed bioavailability of colloidally complexed metalsat low DOC concentration (0.5 ppm) but a generally enhanceduptake at higher DOC concentrations.