Projecte de

Wetlands for Nitrates


Using wetlands to reduce nitrate pollution

Problem: water pollution 

Nitrates are Catalonia’s most important groundwater pollution problem. 41% of Catalan groundwaters are in a bad status (nitrate concentrations over 50 mg/L)The origin of this pollution is primarily agricultural (Agencia Catalana del Agua, 2016).


Legal framework:
Water Framework Directive 2000/60/CE
Directive 2006/118/EC, for the protection of groundwaters.

Problem: air pollution

Atmospherical ammonia can increase particulate matter concentrations, with serious health implications. Ammonia emissions are sourced by agricultural and industrial activities. 

Global hotspots of atmospherical ammonia. NATURE (2018) Industrial and agricultural ammonia point sources exposed Van Damme, M. et al.

Legal framework:
Directive 2008/50/CE, for air quality 

Objectives of this project

  • To prevent and reduce agricultural nitrate pollution in surface and subsurface waters. 
  • To restore denitrifying ecosystems: wetlands, riparian vegetation and meadows.
  • To recover landscape ecological functions for the management of pollution and public health problems. 
Denitrifying ecosystems in an agricultural watershed. ©The Wetlands Initiative

Wetlands are able to remove nitrogen effectively


  • Denitrification is an important function of wetlands and riparian woodlands.
  • Denitrification takes place by means of bacterial activity, in anoxic conditions, which are typical of wetland sediments and waterlogged soils.
  • Nitrates are transformed into gaseous nitrogen (N2), and returned to the atmosphere.


Project  strategy


To restore wetlands in key areas within an agricultural watershed, in order to intercept the highest possible proportion of nitrate. Therefore, working at the landscape scale is the optimal.

Andrena has funded an assessment for a pilot restoration project in the Vic area (Barcelona province). We are advised by scientists at the CEAB-CSICICRA and MN Consultors

Currently we are talking with landowners of fields within the study area, specifically selected due to their suitable hydrogeological characteristics.

We wish to frame this project within the Natural Climate Solutions strategy.

Restored wetlands within an agricultural region in the American Midwest. ©The Wetlands Initiative
Passeport et. al (2013) Ecological Engineering Practices for the Reduction of Excess Nitrogen in Human-Influenced Landscapes: A Guide for Watershed Managers. Environmental Management