| The eruption of Mount St. Helens in southwestern Washington had a pronounced effect on the chemistry of water in rivers draining these areas affected by the debris deposits, pyroclastic flows, mudflows, and airborne ash. Comparison of pre-eruption and post-eruption data show that there were marked increases in selected rivers of the levels of sulfate, chloride, turbidity, total nitrogen, total organic nitrogen, and total iron, manganese, and aluminum. In streams affected solely by ash, the changes were shortlived and the intensity of change decreased with distance downwind from Mount St. Helens. Streams in the blast and mudflow-affected areas showed more persistent effects. -- Klein 1984 |
