Quality assessment of river waters using risk indexes for substances and sites, based on the COMMPS procedure.

The well established risk assessment COMMPS methodology (Fraunhofer Institut, Schmallenberg, Germany) developed at a European basin scale to identify priority pollutants based on their exposure and effects, has been applied at a local scale along a double step process: (a) first, the corresponding adapted list of priority pollutants has been obtained from monitoring data at a regional scale; (b) second, a new site pollution risk index has been developed for the relative comparison of the chemical pollution status of the investigated geographical region. As a case study, representative of the Mediterranean area, the process has been applied to 17 Catalan rivers (NE Spain), using the monitoring data collected between 1997 and 2006 in 207 different sampling sites. After an appropriate selection procedure, 52 parameters were finally used for the calculation of the local priority substance and site risk indexes. From the exposure point of view the most relevant substances at the Catalan scale were volatile organohalogen compounds (VOX) and volatile aromatic hydrocarbons (toluene and xylene), whereas the priority substance risk index points to dibromomethane (volatile organohalogen compound) and benzo-a-anthracene (PAH) as the most concerning compounds. The local and European priority substance indexes have been compared, showing minor differences. Finally, site risk indexes have been calculated and utilized for comparison of the chemical status of different sites. They can be conveniently displayed in quality geographical maps and are considered a valuable tool for the environmental management and risk assessment of the region under study.