Mindaugas Gudas's research while affiliated with Lithuanian University of Agriculture and other places

The reference thresholds of common water quality elements in Lithuanian rivers were established using three different methods: (1) analysis of the data from all sites of the Lithuanian state river monitoring, selecting the 25-th percentile of concentration dispersion for the description of reference thresholds (Buck et al. 2000), (2) linear regression analysis method proposed by Wasson (2006) (relationship between the Lithuanian fish index and water quality indices), and (3) analysis of the dispersion of water quality indices in the rivers of high status according to the Lithuanian fish, selecting the 25% concentration dispersion threshold for the description of reference conditions. A comparison of reference thresholds established by different methods showed that the highest (least stringent) reference concentrations of common elements were obtained when applying Wasson's (2006) method. The reference thresholds obtained using two other methods were lower and rather identical, which implies that they can potentially correspond to real reference thresholds. The reference thresholds of common elements in Lithuanian rivers obtained by different methods were compared with those calculated using different methods and proposed during the European Union intercalibration-harmonization process. Lithuanian reference thresholds were more stringent in nearly all cases, in particular as regards N-NO3, N-NH4, and P-PO4.