dr. shine: this is groundwater bubbling up from underground. what hapns is the iron when it's rground and there's no oxygen, it can stay dissolved. but once it comes up itxidizes, and essentiay what you're looking at is rust. you can see the mixing. here comes the acid mine water. you can see the line where it goes from orange to clear. and the question is, what's the amount of toxic heavy metals that are coming along with that rust? narrator: to gain a clearer understanding of where the metals are coming from, dr. shine and his team take samples of water at different points along tar creek. dr. shine: we will process these, take them back to the lab, and analyze them for heavy-metal content. narrator: back at the lab in boston, laurel schaider is evaluating the samples taken from tar creek using a mass spectrometer. woman: so we run the sample through and it separates the metals based on their atomic mass. and then we're able to quantify the concentration of the metals in the samples. and so t