Environment 360: Mercury levels in the Pacific Ocean have risen by 30 percent in the past 20 years and are expected to increase by 50 percent in the next few decades as emissions from power plants and other industrial sources rise, according to a new study. Scientists from Harvard University and the U.S. Geological Survey discovered the increases after sampling mercury levels at 16 locations in the Pacific Ocean and comparing them with historical data, according to the study, published in the journal Global …