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Origin, fate and TRAnsport modelling of NItrate in the Varaždin ALluvial aquifer



Project title: Origin, fate and TRAnsport modelling of NItrate in the Varaždin ALluvial aquifer
Principal Investigator: Tamara Marković
Duration of the project: 4 years
Begining of the project: 01/03/2017
Granting agency: Croatian Science Foundation (HRZZ)
Project web page: http://projects.hgi-cgs.hr/tranital//




Nitrate is a compound of nitrogen that occurs naturally in moderate concentrations in many aquatic environments. Higher concentrations of nitrate in groundwater are typically caused by anthropogenic activities including nitrogen compounds from synthetic fertilizers and manure used in agriculture, septic systems and other waste waters. All over the world, high concentrations of nitrate are observed and can cause deterioration of groundwater and surface freshwater quality and that poses a serious problem for drinking water supplies and contributes to the process of eutrophication. Since problems relating to high nitrate concentrations occurred in the world, intensive investigation of source, distribution and fate of nitrate and nitrogen related species have been conducted. An interdisciplinary approach was developed to study the spatio-temporal dynamics, fate and sources of nitrate in the aquifer systems at the catchment scale. In response to high nitrate concentration problems, environmental policies have been implemented in the European Union legislation including the Nitrates Directive 91/676/EEC and the Groundwater Directive 2006/118/EC which prohibits that nitrate concentrations in aquifers exceed the mandatory limit of 50 mg/L and requires the actions to be taken in order to reverse or prevent any infringement. The same legislation is valid also in the Croatia. In some parts of Croatia, uncontrolled and extensive production is causing the pollution of groundwater with nitrate. An example of area with high nitrogen content in groundwater is the surrounding area of the town of Varaždin. This area is densely populated with industrial and extensive agricultural production. Farmers are producing high amounts of agricultural products such as corn, cabbage, potatoes etc. Poultry farming is extensive, especially fattening of chickens, quails and pheasants, also breeding of hens. Demands for drinking and industrial water rise because of growing production. High concentrations of nitrate caused the shutting down of the pumping site ‘’Varaždin’’. The research area comprises the catchment area of the pumping sites ‘’Varaždin’’ and ‘’Vinokoščak’’. The aquifer of the research area is composed of gravel and sand with variable portions of silt and it is formed during Pleistocene and Holocene as the result of accumulation processes of the Drava River. A semipermeable layer, mainly composed of silt and clay, splits the aquifer into two layers – upper and lower aquifer. The recharge of the upper aquifer occurs by means of precipitation infiltration and percolation of surface water. The general groundwater flow direction is NW-SE and is parallel to the Drava River. The covering layer of the aquifer is not continuously developed. In the research area, it rarely exceeds two meters, while often it completely disappears. Such conditions are favourable if they are considered from the aspect of aquifer recharge, but at the same time tiny covering layer composed of clay, silt and sand particles mixed with various content of organic matter, make the aquifer quite vulnerable. The previous research that has been conducted in the proposed study area dealing with nitrates was from hydrogeological or agricultural points of view. The proposed systematic interdisciplinary research on fate and distribution of nitrate in the aquifer has never conducted before. The research will include researchers from different fields using different approaches of studying denitrification and nitrification processes in the systems such as an alluvial aquifer:

  1. To develop multi-parametric approach to characterize alluvial aquifer hydraulic properties and chemical, isotopic and microbiological properties of groundwater.
  2. To define the role of surface waters on aquifer recharge and nitrogen cycle.
  3. To define the soil’s mineral, chemical and microbiological properties and its role in nitrogen cycle.
  4. To identify the sources of nitrate that causes the groundwater quality deterioration and the processes that may assist in groundwater natural purification
  5. To establish numerical model of groundwater flow and transport of nitrate in the alluvial aquifer
  6. Transfer of knowledge about nitrate origin, fate and transport in the alluvial aquifer.

The main goal of the TRANITAL project is to provide scientifically justified approach and transfer of knowledge between scientists of different disciplines who will study aquifers with high nitrate concentrations which deteriorate groundwater quality and to transfer the knowledge to decision makers and local water-use groups to ensure environmentally sustainable management of water resources and agricultural production.