Question

What evidence indicates that mercury is still leaching into the Wabigoon River upstream of the community of Grassy Narrows, long after the initial dumping of the original 9+ tonnes of mercury by the chlor-alkali plant (part of the pulp and paper mill) between 1962 and 1970? There are still high concentrations of mercury in recently laid down surface sediments collected at and immediately downstream of the former mill site. Ongoing symptoms of mercury toxicity have been experienced by both young and old people within the community of Grassy Narrows, which have been documented over the decades by researchers from Japan. Mercury concentrations in fish went down after the old mill stopped dumping mercury directly into the system, but leveled off at a much higher concentration than normal (background) levels.

Answer 1

Answer:
Option - Mercury concentrations in fish went down after the old mill stopped dumping mercury directly into the system, but leveled off at much higher concentration than normal (background) levels.

Since the 1970s, the mercury levels in the fish have declined in the Wabigoon river but current mercury levels in these fish are still high as compared to normal. Due to this, consumption advisories have been put in place all along the course of the river.