Reuters: Oil sands operations are polluting the Athabasca River system, researchers said on Monday, contradicting the Alberta government’s assertions that toxins in the watershed are naturally occurring. In a study likely to add more fuel to the environmental battle over oil sands development, researchers said mercury, arsenic, lead and cadmium are among the toxins being released into the Athabasca, which flows north through the region’s major oil sands operations. The findings of the …