Diel variations in photoinduced oxidation of Hg0 in freshwater.
Experiments have been conducted to determine diel variations in photoinduced Hg0 oxidation in lake water under natural Hg0(aq) concentrations. Pseudo-first-order rates of photooxidation (k') were calculated for water freshly collected in a Canadian Shield lake, Lake Croche (45 degrees 56' N, 74 degrees 00' W), at different periods of the day and subsequently incubated in the dark. Hg0 oxidation rates ranged from 0.02 to 0.07 h(-1), increasing from sunrise to noon and then decreasing throughout the remainder of the day. These changes paralleled those in sunlight intensity integrated over 1 h preceding water collection, and suggested that the water freshly collected in daylight was rich in photochemically produced Hg0 oxidants. It was also estimated that under intense solar radiation, even if oxidation rates reached a peak, reduction of Hg(II) was the prevalent redox process. Inversely, Hg0 oxidation overcame DGM production during the night or at periods of weaker light intensity. Overall, these findings explain the decreases in the DGM pool generally observed overnight. They also support previous reports that, during summer days, volatilization of Hg0 from water represent an important step in the Hg cycle in freshwater systems.
Garcia
Edenise
E
Université de Montréal, Département des sciences biologiques, succursale Centre Ville, CP 6128, Montréal, Québec, Canada H3C 3J7.
Poulain
Alexandre J
AJ
Amyot
Marc
M
Ariya
Parisa A
PA
D005618:Fresh Water / Q000737:chemistry*; D008628:Mercury / Q000737:chemistry*; D010084:Oxidation-Reduction / Q000528:radiation effects; D044367:Phase Transition / Q000528:radiation effects; D017440:Photoperiod; D011792:Quebec; D013050:Spectrometry, Fluorescence; D013472:Sunlight; D013997:Time Factors
D008628:Mercury