De potentiële toepasbaarheid van zeoliet voor verschillende bodemtypes

Jelmer van Doorn, Esther Lucassen, Mats Douma, Michael van Roosmalen, Jan Roelofs & Fons Smolders

ammonium, ionenuitwisseling, mineralen, mitigatie, natuurbodems

De kwaliteit van ecosystemen op de Nederlandse zandgronden staat onder druk door de nog steeds te hoge atmosferische stikstofdepositie. Huidige herstelmaatregelen lijken niet altijd voldoende om hiervoor te compenseren. Een nieuwe, mogelijke effectieve maatregel is het aan de bodem toedienen van zeolietmineralen die zowel stikstof kunnen binden als belangrijke elementen kunnen naleveren. Hoe werken verschillende typen zeolieten en hoe effectief zijn deze om de beschikbaarheid van stikstof in de bodem te verlagen?

Mitigating nitrogen deposition with zeolite. Potential applicability for different soil types.

Ammonium, ion exchange, minerals, mitigation, nature soils

Zeolite minerals are able to bind ammonium ions (NH4+) and simultaneously release cations due to their ion-exchange properties, making them promising to mitigate for the increased atmospheric nitrogen deposition. In pilot experiments, the ammonium removal of different zeolites was tested (vulkamin, actionine, optizec) when applied to an ammonium nitrate solution (based on mean annual nitrogen deposition in the Netherlands and to different non-calcareous nature soils. Highest ammonium removal was found two weeks after actionine and optizec application to the ammonium nitrate solution (> 80%) and the slightly buffered g rassland and softwater lake soil solutions (> 50%). In addition, calcium, potassium and sodium cations were released, indicating ion exchange with ammonium. Reductions in ammonium were lower in the acidic (oak forest) and over-limed (heathland) soil solutions, due to higher cation concentrations (H+; Ca2+) which compete with ammonium ions for absorption by zeolites. Vulkamin was less effective in ammonium removal and led to raised pH of the soil solutions, which in turn stimulated organic matter mineralization or nitrification, depending on initial soil conditions. More refined research about longterm effects and field experiments are needed to evaluate whether zeolites can be used in practice as mitigation tool for the raised nitrogen deposition.