A modified QWASI model for fate and transport modeling of mercury between the water-ice-sediment in Lake Ulansuhai

- Mercury contamination in lakes a growing concern in northern China.
- Hg distribution differs between ice growth and ice free periods.
- Ice as an environmental medium was added to develop a new QWASI + ice model.
- Model results compared to experimental tests and within acceptable margin of error.
- QWASI + ice offers potential for more accurate prediction of Hg contamination in winter.

Mercury contamination from industrial and agricultural drainage into lakes and rivers is a growing concern in Northern China. Lake Ulansuhai, located in Hetao irrigation district in Inner Mongolia, is the only sink for the all industrial and agricultural drainage and sole outlet for this district to the Yellow River, which is one of the main source of drinking water for the numerous cities and towns downstream. Because Ulansuahi is ice-covered during winter, the QWASI model was modified by adding an ice equation to get a more accurate understanding of the fate and transport of mercury within the lake. Both laboratory and field tests were carried out during the ice growth period. The aquivalence and mass balance approaches were used to develop the modified QWASI + ice model. The margins of error between the modelled and the measured average concentrations of Hg in ice, water, and sediment were 30%, 26.2%, and 19.8% respectively. These results suggest that the new QWASI + ice model could be used to more accurately represent the fate and transport of mercury in the seasonally ice-covered lakes, during the ice growth period.

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