Aug. 3—A mysterious purple plume that rose above the Portland skyline Thursday morning was most likely caused by a larger-than-normal amount of iodine in the waste stream at ecomaine's waste to energy plant, company officials said. The purple plume, tinged with pink, began rising from a stack at the plant on Blueberry Road in Portland around 9:20 a.m. and could be seen as far away as the Maine ...