Kansas Case Study Applications of Nitrogen-15 Natural Abundance Method for Identification of Nitrate Sources

Townsend, Margaret; Young, D. P.; Macko, Stephen A.

doi:10.4148/1090-7025.1029

Cited by 7 publications

(4 citation statements)

References 18 publications

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“…Natural abundance stable isotopes are effective tools for elucidating biogeochemical processes in microbial ecology (Högberg, 1997;Robinson, 2001;Boschker & Middelburg, 2002;Staddon, 2004). Exploiting differences in isotope signatures between nutrient source and sink has made it possible to link microbial activity to ecosystem processes (Miyazaki et al, 1980;Orphan et al, 2001;Townsend et al, 2003). Ecosystem ecologists are increasingly interested in measuring the natural abundance isotopic composition of the microbial biomass or DNA extracted from the environment in order to interpret dominant microbial processes (Dijkstra et al, 2006a, b;Schwartz et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Nitrogen source influences natural abundance 15N of Escherichia coli

Collins

Dijkstra

Hart

et al. 2008

FEMS Microbiology Letters

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Escherichia coli cells were forced to mineralize or assimilate nitrogen in vitro by manipulating substrate carbon and nitrogen availability. When grown on an organic nitrogen source, E. coli cells released NH(4)(+) and were enriched in (15)N relative to the nitrogen source (1.6-3.1 per thousand). However, when cells were grown on an inorganic nitrogen source, the biomass was depleted (6.1-9.1 per thousand) relative to the source. By measuring (15)N enrichment of microorganisms relative to nitrogen pools, ecosystem ecologists may be able to determine if microorganisms are assimilating or mineralizing nitrogen.

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Section: Introductionmentioning

confidence: 99%

Nitrogen source influences natural abundance 15N of Escherichia coli

Collins

Dijkstra

Hart

et al. 2008

FEMS Microbiology Letters

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“…In a study conducted in Runnels County in Texas, Kreitler and Jones (1975) concluded that about 66% of the NO 3 in groundwater had natural sources. In general, the δ 15 N values of N from commercial fertilizers, soil, precipitation, and animal wastes range from −7 to +8‰, +5 to +7‰, 12 to +3‰, and greater than +10‰, respectively (Kellman and Hillaire‐Marcel, 2003; Townsend et al, 2003). However, considerable overlap in δ 15 N between N sources makes their accurate identification difficult using N isotopes.…”

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confidence: 99%

Spatio-temporal Variability of Groundwater Nitrate Concentration in Texas: 1960 to 2010

et al. 2012

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Nitrate (NO) is a major contaminant and threat to groundwater quality in Texas. High-NO groundwater used for irrigation and domestic purposes has serious environmental and health implications. The objective of this study was to evaluate spatio-temporal trends in groundwater NO concentrations in Texas on a county basis from 1960 to 2010 with special emphasis on the Texas Rolling Plains (TRP) using the Texas Water Development Board's groundwater quality database. Results indicated that groundwater NO concentrations have significantly increased in several counties since the 1960s. In 25 counties, >30% of the observations exceeded the maximum contamination level (MCL) for NO (44 mg L NO) in the 2000s as compared with eight counties in the 1960s. In Haskell and Knox Counties of the TRP, all observations exceeded the NO MCL in the 2000s. A distinct spatial clustering of high-NO counties has become increasingly apparent with time in the TRP, as indicated by different spatial indices. County median NO concentrations in the TRP region were positively correlated with county-based area estimates of crop lands, fertilized croplands, and irrigated croplands, suggesting a negative impact of agricultural practices on groundwater NO concentrations. The highly transmissive geologic and soil media in the TRP have likely facilitated NO movement and groundwater contamination in this region. A major hindrance in evaluating groundwater NO concentrations was the lack of adequate recent observations. Overall, the results indicated a substantial deterioration of groundwater quality by NO across the state due to agricultural activities, emphasizing the need for a more frequent and spatially intensive groundwater sampling.

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“…Animal waste has a high ammonia component and because of the preferential release of 14 N by the volatilization of ammonia (Kreitler, 1975), the remaining nitrogen becomes enriched in δ 15 N to a value of +10‰ or more. Generally in Kansas, with animal-waste sources, nitrate-N values are commonly more than 10 mg/L and δ 15 N values are above +10‰ (Townsend et al, 2003).…”

Section: Nitrogen-15 Natural Abundance Isotope Methodsmentioning

confidence: 99%

Preliminary Identification of Ground-Water Nitrate Sources Using Nitrogen and Carbon Stable Isotopes, Kansas

Townsend

Macko

2007

CRES

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Increasing nitrate-N in ground water is a problem in many areas with limited ground-water supplies, such as west-central Kansas. However, potential sources of nitrate-N are not known. Nitrate-N concentrations in ground water in the Hays study area in Ellis County, west-central Kansas, range from 0.9 to 26 mg/L. The δ15N signatures of the ground waters are more enriched (+16.8 to +28.7‰) than those of the soils (+8.4 to +13.7‰), strongly suggesting that nitrogen sources are not from mineralized and labile nitrogen present in the unsaturated zone. In this study, nitrate-N values greater than the U.S. EPA drinking water limit of 10 mg/L occur with δ15N values of greater than +10‰. This relationship between high nitrate-N concentrations and enriched δ15N values (greater than +10‰) in ground water has been observed in other studies in Kansas and is usually related to a human- and/or animal-waste source. Soil cores collected near municipal wells had mean total nitrogen values of 1.2-15 mg/kg. Increased δ15N with depth in several of the cores suggests that microbial mineralization, denitrification, or volatilization processes caused the enriched δ15N signatures. Decreasing total nitrogen and nitrate-N values with depth also help support the idea of microbial processes. Stable carbon isotopes provide supporting evidence that soils are not a major contributor to the observed nitrate-N concentration in the ground water. δ13C values of the dissolved organic carbon (DOC) in soils generally were more enriched (-11.6 to -18.8‰) while corresponding ground-water δ13C values were more depleted (-19.9 to -22.2‰), suggesting that the source of the DOC in ground water is not from the soils.

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Kansas Case Study Applications of Nitrogen-15 Natural Abundance Method for Identification of Nitrate Sources

Cited by 7 publications

References 18 publications

Nitrogen source influences natural abundance 15N of Escherichia coli

Nitrogen source influences natural abundance 15N of Escherichia coli

Spatio-temporal Variability of Groundwater Nitrate Concentration in Texas: 1960 to 2010

Preliminary Identification of Ground-Water Nitrate Sources Using Nitrogen and Carbon Stable Isotopes, Kansas

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