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Chemical and isotopic results

Overview

The pilot site is located in the Alsace region (France), it is part of the Upper Rhine basin. This site was selected because of the strong anthropogenic (agriculture, urbanisation, industries...) impact on the groundwater body (one of the most important drinking water reservoirs in Europe).

The ISONITRATE project is a demonstration project, we need to prove that isotope can clearly discriminate the different types of pollution sources (unlike classical chemical analysis). Thus the selected sites have been minimized to only a few sites with specific problems that have been previously studied. Four sampling sites have been chosen on the basis of the review data in order to cover different cases of nitrate concentrations and nitrate sources that will represent a pool of demonstrative samples:

  1. Non-polluted end-member. This sampling site corresponds to the natural nitrification of the soil and will represent the reference end-member. Samples with NO3 concentration levels higher than this end-member will be considered as polluted.
  2. Simple nitrate source. This sampling site is supposed to involve only one type of pollution source.
  3. Multiple nitrate sources. This sampling site corresponds to a more complex site where nitrates correspond to a mixing of different pollution sources.
  4. Natural denitrification zone. This sampling site is of crucial importance for the demonstration feature of the project. A transect along the flow direction will be studied, from the more contaminated sample (without denitrification process) to very low NO3 concentrations (down to 2-5 mg/l through denitrification) and via partially denitrified samples.

The sampling strategy

For the 4 studied cases both surface water and groundwater are collected.

In the 4 studied cases, a total of 16 sampling points were selected, about 2/3 of which are for groundwater sampling from piezometers and about 1/3 for surface water from rivers. Sampling are planned 12 times over a period of 18 months:

2007 2008
January 4  Done
February 5  Done
March 6  Done
April 7  Done
May
June 8  Done
July
August 9  Done
September
October 1  Done 10  Done
November 2  Done 11  Done
December 3  Done 12  Done
Done Done
P Planned

The anthropogenic inputs for the pilot site under investigation, potentially contributing to surface and groundwater pollution, are characterized on the basis of a pool of 40 samples including:

  • various chemical fertilisers,
  • various organic fertilisers (manure),
  • sewage affluents.

The local potential sources of anthropogenic nitrate were sampled from farms, agricultural marketing cooperative and sewage stations (liquid effluent and dried mud) in the different studied sites.

Source samples

Analysis and results

Samples were dispacthed in the labs of the partners (VITO and BRGM) and analyses are in progress.

The field data measured on site during each sampling campaigns : Temperature (T, °C), pH, Redox potential (Eh, mV), Electric Conductivity (EC, µS/cm et 25°C), Dissolved Oxygen (O2, %), Water level of groundwater (m).

Data can be downloaded (pdf) from the table:

ISONITRATE Sampling Campaign Field data
1 October 2007 PDF
2 November 2007 PDF
3 December 2007 PDF
4 January 2008 PDF
5 February 2008 PDF
6 March 2008 PDF
7 April 2008 PDF
8 June 2008 PDF
9 August 2008 PDF
10 October 2008 PDF
11 November 2008 PDF
12 December PDF

The sample locations are presented on the following maps.

Maps
General map of the studied sites Map
Natural Case Map
Simple Case Map
Complex Case Map
Denitrification Case Map

The first results of the ISONITRATE Project can be downloaded here (in French). These results were presented to the local authorities In Strasbourg (8 dec. 2008). Foreword: the results presented here are preliminary results based on the first interpretation of an incomplete data set. Results presented here can't be considered as the final understanding of the different studied cases.

Last results