Annual and seasonal variations of some heavy metal concentrations in the Lakes Mazais and Lielais Baltezers
Osite, A.(University of Latvia, Riga (Latvia)) | Viksna, A.(University of Latvia, Riga (Latvia)) | Pastare, S.(University of Latvia, Riga (Latvia)) | Nulle, S.(University of Latvia, Riga (Latvia)) | Balcerbule, Z.(University of Latvia, Riga (Latvia))
The obtained results of the current investigation during four years show interesting alterations of trace element concentrations in water of the Lake Lielais and Mazais Baltezers. Marked seasonal variations of manganese and zinc concentrations were observed, probably due to the eutrophication processes usually during July to September. Mean concentrations of copper during four years were rather stable and significant alterations were not observed. Mean concentrations of cadmium and lead ions changed about three times during the investigation period and the main source of these contaminants is considered to be the uncontrolled increasing domestic activities. Only in 2004 decrease of cadmium and lead concentrations was observed, but this could be explained by the long rainy period in the summer.
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