Nitrate-nitrogen concentrations in ground water from three selected areas in Kansas /

Mode of access: Internet.

Identifying sources of subsurface nitrate pollution with stable nitrogen isotopes /

"Contract no. 68-03-2450."

National performance audit program : 1980 proficiency surveys for sulfur dioxide, nitrogen dioxide, carbon monoxide, sulfate, nitrate, lead and high volume flow /

Mode of access: Internet.

Fertilizer application rates and nitrate concentrations in Illinois surface waters : a report to the Illinois Institute for Environmental Quality /

Includes bibliographical references.