Full-text search functions in environmental portals make a large amount of environmental data accessible. Many data sources, however, are not suited for indexing by search machines or the data themselves are not suited for access by full-text search. A possibility to make such data of the “dark web” accessible consists in addressing the data sources in the environmental portal directly. The procedure presented here starts with a formal description of data sources (e.g. from the point of view of the portal, these are the target systems). Based on this description, a special component of full-text search, the so-called search broker, can extend and detail a search query, such that all necessary parameters (if possible) are compiled to address these systems and to guide the user directly to the data desired. The presentation component of the environmental portal is responsible for the adequate compilation and display of these data, the so-called result mash-up.