Across the country, the shale boom has given rise to fears about whether oil and gas development might be polluting the water we drink and the air we breathe. This has led some residents to try doing their own field research, in the mode of “citizen science.” But unlike the annual Christmas Bird Count or a website to help astronomers catalog billions of galaxies, their work is a tricky blend of science and advocacy.

Joanne Martin stands on the muddy bank of Brady Run, a stream in Beaver County in western Pennsylvania. To get there, she crawled down a steep gravel slope, ducking low tree branches and stepping over dead brush.