On 5 November, a dam holding approximately 50 million cubic meters of waste from iron mines burst withoutwarning near the city of Mariana in Minas Gerais state.
The disaster spawned a mud tsunami that buried villages downstream, killing at least 13 people.
Within a day, the wave reached the Doce River and traversed 600 kilometerssnuffing out aquatic life in its pathbefore spilling into the Atlantic Ocean on 21 November.
A network of scientists, backed by crowdfunding, is analyzing river samples to assess the environmental impacts independently of the government and the mining companies that managed the dam.
One controversy they hope to settle is whether the sludge was laced with two dozen heavy metals, including arsenic, copper, and mercury, and whether such toxic contamination will persist, delaying recovery.
2015 by the American Association for the Advancement of Science (AAAS)