The application of a simplified method to map the aerobic acetate mineralization rates at the groundwater table of the Netherlands Patrick Van Beelen ⁎, Marja J. Wouterse, Niels J. Masselink, Job Spijker, Miranda Mesman Laboratory for Ecological Risk Assessment, RIVM, National Institute for Public Health and the Environment, P.O. Box 1, 3720 BA Bilthoven, The Netherlands article info abstract Article history: Received 7 May 2010 Received in revised form 8 October 2010 Accepted 21 November 2010 Available online 28 November 2010 A simplified method is used to assess the microbial activity of subsoils and soils across a broad geographic scale. Acetate was selected because it is a major intermediate in catabolic biochemical pathways. In order to get minimal disturbance, only a small amount of tritium labelled acetate and water is added to the subsoil material. After an incubation time, the subsoil material is separated from the water by centrifugation and the formed tritium labelled water is separated from the remaining acetate by evaporation. The data of 128 locations in the Netherlands were plotted in a soil map and were also compared with the depth, dry weight, electric conductivity, pH and nitrate concentration. The peat areas consisted of limed meadows with a high groundwater level whereas the sand areas often showed deeper groundwater levels and a lower pH. The subsoils at the groundwater table of the peat areas, which are in contact with soil air, showed a higher mineralization rate compared with the surface soils in our study. In contrast, the mineralization rate of the subsoil at the groundwater table of sandy soils showed on average a factor 30 lower rate. Nevertheless, the self purification capacity of the subsoil can be vital under weather conditions where the surface soil becomes less active. © 2010 Elsevier B.V. All rights reserved. Keywords: Biodegradation Groundwater Acetate Map Ecosystem Services 1. Introduction The European water framework directive (EC, 2000) and the groundwater directive (EC, 2006) state that the European Member States must take measures to limit or prevent the input of pollutants in groundwater. The European guidance number 17 (EC, 2007) describes points of compliance where it must be checked whether the groundwater meets quality criteria. The first point of compliance lies directly under the pollution source in the subsoil at the groundwater table. We will use the word subsoil for the solid materials at the groundwater table together with the groundwater. For dangerous substances the environmental quality standard has to be met at this point of compliance (EC, 2007). For non- dangerous substances the quality standard does not need to be met at this point but must be met down streams of the groundwater. 1.1. The self purification capacity is a vital ecosystem service Natural attenuation processes like biodegradation and sorption play a role in groundwater together with dissipation processes like volatilization and dilution (Christensen et al., 2001). Biodegradation is not only dependent on the properties of the substance but also on the properties of the environment, like pH (Kjeldsen et al., 2002), redox potential (Meckenstock et al., 2004) and the presence of toxic concentrations of substances which can be present in contaminant plumes (Prommer et al., 2009). The redox potential is governed by the presence of oxidizing substances like oxygen, ferric iron, sulfate or even carbon dioxide (Christensen et al., 2001). An active microbial community can have the capacity to biodegrade organic compounds which is an economically valuable ecosystem service (Costanza et al., 1997). This self purification capacity of the subsoil at the groundwater table Journal of Contaminant Hydrology 122 (2011) 86–95 ⁎ Corresponding author. RIVM, National Institute for Public Health and the Environment, Antonie van Leeuwenhoeklaan 9, 3721 BA Bilthoven, The Netherlands. Tel.: + 31 302743133; fax: + 31 302744413. E-mail address: Patrick.van.Beelen@rivm.nl (P. Van Beelen). 0169-7722/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.jconhyd.2010.11.006 Contents lists available at ScienceDirect Journal of Contaminant Hydrology journal homepage: www.elsevier.com/locate/jconhyd