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Article

Hot Spots and Persistence of Nitrate in Aquifers Across Scales

1
Earth Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
2
Biological and Agricultural Engineering Department, Texas A&M University, College Station, TX 77843, USA
*
Author to whom correspondence should be addressed.
Academic Editor: Kevin H. Knuth
Entropy 2016, 18(1), 25; https://doi.org/10.3390/e18010025
Received: 29 May 2015 / Revised: 3 December 2015 / Accepted: 5 January 2016 / Published: 13 January 2016
(This article belongs to the Special Issue Applications of Information Theory in the Geosciences)
Nitrate-N (NO3 -- N) is one of the most pervasive contaminants in groundwater. Nitrate in groundwater exhibits long-term behavior due to complex interactions at multiple scales among various geophysical factors, such as sources of nitrate-N, characteristics of the vadose zone and aquifer attributes. To minimize contamination of nitrate-N in groundwater, it is important to estimate hot spots (>10 mg/L of NO3 -- N), trends and persistence of nitrate-N in groundwater. To analyze the trends and persistence of nitrate-N in groundwater at multiple spatio-temporal scales, we developed and used an entropy-based method along with the Hurst exponent in two different hydrogeologic settings: the Trinity and Ogallala Aquifers in Texas at fine (2 km × 2 km), intermediate (10 km × 10 km) and coarse (100 km × 100 km) scales. Results show that nitrate-N exhibits long-term persistence at the intermediate and coarse scales. In the Trinity Aquifer, overall mean nitrate-N has declined with a slight increase in normalized marginal entropy (NME) over each decade from 1940 to 2008; however, the number of hot spots has increased over time. In the Ogallala Aquifer, overall mean nitrate-N has increased with slight moderation in NME since 1940; however, the number of hot spots has significantly decreased for the same period at all scales. View Full-Text
Keywords: entropy analysis; nitrate-N in groundwater; temporal variability; spatial variability; multi-scale analysis; Hurst exponent entropy analysis; nitrate-N in groundwater; temporal variability; spatial variability; multi-scale analysis; Hurst exponent
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MDPI and ACS Style

Dwivedi, D.; Mohanty, B.P. Hot Spots and Persistence of Nitrate in Aquifers Across Scales. Entropy 2016, 18, 25. https://doi.org/10.3390/e18010025

AMA Style

Dwivedi D, Mohanty BP. Hot Spots and Persistence of Nitrate in Aquifers Across Scales. Entropy. 2016; 18(1):25. https://doi.org/10.3390/e18010025

Chicago/Turabian Style

Dwivedi, Dipankar, and Binayak P. Mohanty 2016. "Hot Spots and Persistence of Nitrate in Aquifers Across Scales" Entropy 18, no. 1: 25. https://doi.org/10.3390/e18010025

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