Nitrate concentrations in the groundwater in southern Runnels County, Texas, ranged from less than 0.5 mg/l to 3,580 mg/l. Only ten percent of the water samples analyzed contained less than the U. S. Public Health Service ...

Nitrogen isotope ratios of ammonium and nitrate ions from soil and water samples can be analyzed reproducibly with an experimental error of approximately ±1⁰/₀₀. Two isotopic ranges of soil nitrate are found in the soils ...