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UPTAKE OF LIPOPHILIC CADMIUM COMPLEXES BY THREE GREEN ALGAE: INFLUENCE OF HUMIC ACID AND ITS pH DEPENDENCE 1
Author(s) -
Boullemant Amiel,
Le Faucheur Séverine,
Fortin Claude,
Campbell Peter G. C.
Publication year - 2011
Publication title -
journal of phycology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.85
H-Index - 127
eISSN - 1529-8817
pISSN - 0022-3646
DOI - 10.1111/j.1529-8817.2011.01013.x
Subject(s) - dissolved organic carbon , humic acid , algae , cadmium , biology , environmental chemistry , chelation , chemistry , nuclear chemistry , botany , inorganic chemistry , ecology , organic chemistry , fertilizer
Cadmium forms neutral, lipophilic CdL 2 0 complexes with diethyldithiocarbamate (L = DDC) and with ethylxanthate (L = XANT). In a synthetic solution and in the absence of natural dissolved organic matter (DOM), for a given total Cd concentration, uptake of these complexes by unicellular algae is much faster than the uptake of the free Cd 2+ cation. The objective of the present study was to determine how this enhanced uptake of the lipophilic CdL 2 0 complexes was affected by the presence of natural DOM (Suwannee River humic acid, SRHA). Experiments were performed with Cd(DDC) 2 0 and Cd(XANT) 2 0 at two pH values (7.0 and 5.5) and with the three chlorophytes [ Chlamydomonas reinhardtii P. A. Dang., Pseudokirchneriella subcapitata (Korshikov) Hindák, Chlorella fusca var. vacuolata Shihira et R. W. Krauss]. Short‐term uptake (30–40 min) of the CdL 2 0 complexes was followed in the absence and presence of SRHA (6.5 mg C · L −1 ). Acidification from pH 7.0 to 5.5 decreased CdL 2 0 uptake by the three algae, in the presence or absence of humic acid (HA). The dominant effect of the HA was to decrease Cd uptake, due to its interaction with the CdL 2 0 complexes in solution. However, if uptake of the free CdL 2 0 complexes was compared in the presence and absence of HA, in four of eight cases initial uptake rate constants ( k i ) were significantly higher ( P < 0.05) in the presence of the HA, suggesting the operation of an interfacial effect of the HA at the algal cell membrane, favoring uptake of CdL 2 0 . Overall, the experimental results suggest that neutral metal complexes will be less bioavailable in natural waters than they are in synthetic laboratory media in the absence of natural DOM.