Identification of river basin specific pollutants and derivation of environmental quality standards: A case study in the Slovak Republic

Following the requirements of the European Water Framework Directive (WFD), a process of selecting relevant dangerous substances and developing related Pollution Reduction Programme (PRP) has started in the Slovak Republic in 2001. Based on the results of a three years investigative screening campaign, 59 chemical substances were identified as relevant dangerous substances in 2004 and included in the national PRP. This study describes two independent prioritization approaches that have been applied to revise the list of relevant dangerous substances in 2010. The first approach was using a classification system based on the occurrence monitoring data of these substances combined with self-monitoring data by industries on their emissions into wastewaters and data on production/usage of chemicals and agricultural pesticides. As an outcome, 41 of the 59 relevant substances were proposed to be retained in the updated PRP. The second approach was based on the evaluation of the Frequency of exceedance and the Extent of exceedance of environmental thresholds, referred to as predicted no effect concentrations (PNEC), for all organic compounds monitored in the river systems of the Slovak Republic from 2001 to 2010, with exclusion of WFD priority substances (PS). The results showed that 18 of 87 monitored compounds deserve closer attention in future revisions of the list, out of which 11 pollutants were new candidates to expand the list of relevant substances. The two approaches were found complementary. The methodology included a safety net to capture new pollutants not previously listed among the above target substances. A novel approach of prioritizing gas chromatography - mass spectrometry (GC-MS) non-target screening data, based on the assessment of (i) derived provisional PNEC (P-PNEC) values and (ii) estimated concentrations of tentatively identified substances, has been applied for the first time. P-PNEC values were derived for 242 substances and the prioritization effort resulted in a list of 60 new substances that might be potential candidates for inclusion into investigative monitoring schemes and, if their relevance confirmed, into the updated PRP. (C) 2012 Elsevier Ltd. All rights reserved.