Distribution and sources of nitrate-nitrogen in Kansas groundwater.

Margaret A Townsend,Stephen A Macko,David P Young

doi:10.1100/tsw.2001.331

Margaret A Townsend, Stephen A Macko + Show 1 more

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https://doi.org/10.1100/tsw.2001.331

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Abstract

Kansas is primarily an agricultural state. Irrigation water and fertilizer use data show long- term increasing trends. Similarly, nitrate-N concentrations in groundwater show long-term increases and exceed the drinking-water standard of 10 mg/l in many areas. A statistical analysis of nitrate-N data collected for local and regional studies in Kansas from 1990 to 1998 (747 samples) found significant relationships between nitrate-N concentration with depth, age, and geographic location of wells. Sources of nitrate-N have been identified for 297 water samples by using nitrogen stable isotopes. Of these samples, 48% showed fertilizer sources (+2 to +8) and 34% showed either animal waste sources (+10 to +15 with nitrate-N greater than 10 mg/l) or indication that enrichment processes had occurred (+10 or above with variable nitrate-N) or both. Ultimate sources for nitrate include nonpoint sources associated with past farming and fertilization practices, and point sources such as animal feed lots, septic systems, and commercial fertilizer storage units. Detection of nitrate from various sources in aquifers of different depths in geographically varied areas of the state indicates that nonpoint and point sources currently impact and will continue to impact groundwater under current land uses.

Highlights

Groundwater is the major source of drinking water for 50% of the residents in Kansas[1]
The primary sources of data consist of studies done by the Kansas Geological Survey (KGS) and by other agencies for which the KGS performed groundwater chemistry analyses
The δ15N was determined on a Micromass Optima isotope ratio mass spectrometer (IRMS) coupled with an elemental analyzer (EA), with an overall precision better than 0.5

Summary

Introduction

Groundwater is the major source of drinking water for 50% of the residents in Kansas[1]. In the western twothirds of Kansas, has increased since the 1940s, as illustrated by the cumulative irrigation water rights and the volume of nitrogen fertilizer sold statewide[9] (Fig. 1). Animal waste (including human waste) is another potential point source of nitrate (feedlots, septic systems, and sewage wastetreatment systems) and nonpoint source (use of manure as fertilizer). The potential contribution of animal-waste nitrogen loading to the hydrologic system in Kansas is approximately 180,000 metric tons/year[9,10] if the waste is not properly utilized. The total amount of organic nitrogen from animal and human sources is less than 20% of the amount of nitrogen applied in the form of commercial fertilizers (900,000 metric tons, Fig. 1) in the year 2000

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