Use of reflectometry for determination of nitrate‐nitrogen in well water

Abstract

Recurrent monitoring of water wells is necessary to ensure that nitrate‐nitrogen (NO3‐N) concentrations in groundwater do not exceed 10 mg/L, the maximum contaminant level set by the U.S. Environmental Protection Agency. Continuous chemical analysis is often a time consuming and expensive process. A recently developed ‘Reflectoquant Analysis System’, which employs reflectometry techniques, may offer a simple and accurate method for NO3‐N analysis. The objective of this study was to evaluate the ‘Reflectoquant Analysis System’ as an alternative method for determination of NO3‐N in well water. Water samples were collected from 42 wells in Oklahoma. The samples were analyzed using the ‘Reflectoquant Analysis System’, automated cadmium reduction (Griess‐Ilosvay), ion chromatography, and phenoldisulfonic acid procedures. The linear range of the ‘Reflectoquant Analysis System’ is 1.1 to 50.6 mg/L NO3‐N. Samples exceeding this range must be diluted before analysis is performed. Excluding two wells where NO3‐N was >50.6 mg/L, simple correlation was high (r > 0.91) among the four procedures evaluated. In addition, slopes and intercepts from linear regression of NO3‐N among procedures were not significantly different. Population means obtained using the four methods were very similar. For this sample of wells, the ‘Reflectoquant Analysis System’ was precise and provided NO3‐N analysis of water samples equivalent to standard methods. Other advantages of the ‘Reflectoquant Analysis System’ are short analytical times, reduced operator training period, and competitive costs compared to standard methods.

Notes

Contribution from the Oklahoma Agricultural Experiment Station, Stillwater, OK.

Graduate research assistant, and Assistant Professors, respectively.