Operation Sources in Belgium: preliminary statistical analyses of the results and validation of the "nitrates" map

The Operation Sources of the WWF (Worldwide Fund for Wildlife) in Belgium i s an environmental educational campaign focused on the groundwater quality. It involves pupils in the fifth and sixth grades of primary school in Belg ium. Since 1994, several hundred analyses of nitrate have been carried out using colorimetric test strips at numerous springs and wells throughout Bel gium. At the end of each campaign, the point sources of water surveyed were recorded on a map of Belgium, using different colours to indicate their ra nge of nitrate concentration. The educational objective having been fulfill ed, in order to validate these maps it was necessary to verify for each vis ited point source the relationship between its actual nitrate concentration (mg l(-1)) and its colour on the map. To this end, verification was carrie d out on 308 point sources chosen at random from those tested. The statisti cal analysis shows that the relationship between the results of the colorim etric in situ tests and corresponding laboratory control checks is highly s ignificant. This result warrants further investigations, notably the use of regional information to qualify a poorly surveyed source point and also to check the temporal changes of the maps.