Deposition Monitoring Networks: What Monitoring Site Density Is Required to Give Reasonable Estimates of Ammonia/ammonium?

Deposition is one of the main loss terms for ammonia and ammonium from the atmosphere. It is also the input for ecosystems that can lead to drastic changes and effects. Deposition networks are needed to evaluate the need and the effect of policies to reduce emissions, but also for studying deposition parameters and develop deposition models. As with the ambient concentration of ammonia, deposition, especially dry deposition, varies strongly in space and in time. Furthermore, the bi-directional surface – atmosphere exchange of ammonia makes the combination of ambient concentration measurements with inferential models inadequate. Developing deposition monitoring networks with reasonable accuracy and representativity is therefore not straightforward. In Europe several projects have addressed deposition monitoring. From these results it is concluded that a monitoring strategy should consist of a network with a limited amount of super sites combined with a larger number of sites where cheap methods are applied, together with models for generalization.

⁽¹⁾ Energy Research Centre of the Netherlands, P.O.Box 1, 1755 ZG Petten, The Netherlands
⁽²⁾ CEH, Edinburgh, UK 3RIVM, Bilthoven, NL
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