Distribution and temporal variation of cadmium in the St. Lawrence river basin |
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Authors: | Bernadette Quémerais Ken R Lum |
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Institution: | (1) St. Lawrence Centre, Contamination of the Aquatic Environment, Environment Canada, 105 McGill, 7th floor, H2Y 2E7 Montréal, Québec;(2) World Conservation Union, 380 St. Antoine Street West, Suite 3200, H2Y 3X7 Montréal, Québec |
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Abstract: | Samples of raw water were collected at regular intevals at two transects in the St. Lawremce River and four of its tributaries
from March to November 1991 and from April to June 1992. Water samples were analyzed for both the dissolved and the particulate
phase for cadmium (Cd), organic carbon, iron and manganese. Mean dissolved Cd concentration was 10±5 ng/L and no spatial variability
was observed. Higher concentrations were found during high flow periods, suggesting an uptake of cadmium by phytoplankton
during summer. In addition, dissolved cadmium did not appear to be associated with either DOC, dissolved Fe or dissolved Mn.
The mean particulate Cd concentration was 1.3±1.1 μg/g, with almost all stations presenting the same concentration except
the Yamaska River, which had a concentration of 0.5±0.2 μg/g. Particulate Cd showed a negative correlation with suspended
particulate matter and a positive correlation with particulate organic carbon and particulare manganese. Fifty-nine percent
of the cadmium was found to be in the particulate phase. Partition coefficients for cadmium (Kd), organic carbon (Kc), iron
(KdFe) and manganese (KdMn) were calculated for each sample. Log Kd varied from 3.9 to 5.9, with an average of 5.0±0.4. Log
Kd decreased with increasing particulate, matter as did Log Kc and Log KdMn. No significant correlation was found between
Log Kd and Log Kc, suggesting that the distribution of cadmium between the dissolved and the particulate phase is not influenced
by the distribution of organic carbon. In contrast, positive correlations were observed between Log Kd, Log KdFe and Log KdMn.
Cadmium distribution appears to be influenced by Fe and Mn distribution. |
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Keywords: | Cadmium seasonal variation particles Fe Mu organic carbon |
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