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Geosciences 2018, 8(5), 159; https://doi.org/10.3390/geosciences8050159

Estimation of Nitrate Trends in the Groundwater of the Zagreb Aquifer

1
Faculty of Mining, Geology and Petroleum Engineering, University of Zagreb, 10000 Zagreb, Croatia
2
Intellomics Ltd., 10000 Zagreb, Croatia
Deceased in February 2018.
*
Author to whom correspondence should be addressed.
Received: 27 March 2018 / Revised: 27 April 2018 / Accepted: 28 April 2018 / Published: 2 May 2018
(This article belongs to the Special Issue Groundwater Pollution)
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Abstract

Nitrates present one of the main groundwater contaminants in the world and in the Zagreb aquifer. The Zagreb aquifer presents the main source of potable water for the inhabitants of the City of Zagreb and it is protected by the Republic of Croatia. The determination of contaminants trends presents one of the main tools in groundwater body status and risk assessment. In this paper, the use of regression analysis on the aggregated data, together with confidence and prediction intervals, at different observation scales has been evaluated. Nitrate concentrations are generally decreasing in almost all areas, observed at different observation scales. It has been shown that linear regression can be efficiently used in the estimation of nitrates trends. Results showed that the calculation of confidence and prediction intervals can provide more useful conclusions than the calculation of the trend’s statistical significance. Also, the results suggest that confidence and prediction intervals can be used in groundwater body chemical status and risk assessment, respectively. Data smoothing and data aggregation are generally desirable, but have certain limitations. If too much data is aggregated, trend estimation by regression analysis can point to false conclusions. Evaluation of trends at different observational scales can provide more realistic trend estimation, as well as more precise identification of areas where groundwater protection measures should be implemented. View Full-Text
Keywords: linear regression; LOESS non-parametric regression; confidence and prediction intervals; data aggregation; nitrate contamination; Zagreb aquifer; trend’s evaluation at different scales linear regression; LOESS non-parametric regression; confidence and prediction intervals; data aggregation; nitrate contamination; Zagreb aquifer; trend’s evaluation at different scales
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Kovač, Z.; Nakić, Z.; Špoljarić, D.; Stanek, D.; Bačani, A. Estimation of Nitrate Trends in the Groundwater of the Zagreb Aquifer. Geosciences 2018, 8, 159.

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