dr. john martin is a colleague of professor graham's at the unirsy of florida water institute. his team studies the healthof the suwannee ver basin, sampling and testing its water for signs of pollution. because of sandy soils and the soluble limestone-bedrock geology in this part of florida, rivers here run above ground d then flow underground through sinkholes. above ground water can be sampled directly. but underground, the water fills and moves through the porous rock aquifer. this water can be accessed through a series of wells. the aquifer water here the water that's contained in the rocks in the very small, microscopic, pore spaces within the rock, is what's utilized for drinking water and, actually, all water so agriculture-irrigation water, bottling water any kind of water usage is almost all from ground water. narrator: by carefully measuring the depth of ground water, main's team can calculate how much is being used. 17.29. they also record the water's chemical composition to determine nutrient levels that could adversely affect the health of the water. okay, we're r

dr. john martin is a colleague of professor graham's at the unirsy of florida water institute. his team studies the healthof, sampling and testing its water for signs of pollution. because of sandy soils and the soluble limestone-bedrock geology in this part of florida, rivers here run above ground and then flow underground through sinkholes. above ground, water can be sampled directly. but underground, the water fills and moves through the porous rock aquifer. this water can be accessed through a series of wells. the aquifer water here, the water that's contained in the rocks in the very small, microscopic, pore spaces within the rock, is what's utilized for drinking water and, actually, allater, so agriculture-irrigation water, bottling water, any kind of water usage is almost all from ground water. narrator: by carefully measuring the depth of ground water, main's team can calculate how much is being used. 17.29. they also record the water's chemical composition to determine nutrient levels that could adversely affect the health of the water. okay, we're ready to sample. nar

dr. martin luther king junior's sister christine, arm in arm with congressman john lewis, leading the way large "get out the vote" drive called "souls to the polls." but it's not a presidential election year and the first african american president, barack obama, is not on the ballot. except in tv spots being aired by most republican senate candidates this year, including david perdue here in georgia. >> job losses come from bad policies in washington. the policies of president obama and michelle nunn. the president himself said, "make no mistake, these policies are on the ballot." >> woodruff: perdue, a 64-year- old former corporate executive and first time candidate, is trying to take advantage of president obama's unpopularity with most georgia voters, by saying his democratic opponent, michelle nunn, would be a rubber stamp for obama policies. it's an argument that perdue supporters, like 31-year-old massage therapist and mother of three, erin krenz, who regularly volunteers to make calls and knock on doors for him, enthusiastically embraces: >> because there are so many bad policies