How to Implement User-Friendly BLMs in the Absence of DOC Monitoring Data: A Case Study on Bulgarian Surface Waters

The metal bioavailability concept is implemented in the Water Framework Directive (WFD) compliance assessment. assessment usually performed by application of user-friendly Biotic Ligand Models (BLMs), which require dissolved concentrations to be used with “matching” data supporting physicochemical parameters organic carbon (DOC), pH and Cadissolved. Many national surface water monitoring networks do not have sufficient matching records, especially for DOC. In this study, different approaches dealing missing DOC are presented: substitution using historical data; appropriate percentile concentrations; combinations two. applicability three following proposed verified comparison available data: (i) calculations from TOC (ii) 25th joint Bulgarian network (measured calculated TOC); (iii) investigated body (SWB). BLMs (BIO-MET, M-BAT PNEC Pro) 13 bodies (3 reservoirs 10 rivers) waters outlines that suitability decreases order: > use respective SWB data. Additionally, BIO-MET most tool Cu, Zn Pb bodies.