A study of surface water quality in Macedonia, Greece: Speciation of nitrogen and phosphorus

A 2-yr (1997-1998) survey aiming at the establishment of national data bases concerning the quality of surface waters has been conducted in the major river systems of Macedonia, N. Greece. This paper presents the physicochemical parameters (pH, conductivity, total suspended solids, temperature and DO), the organic pollution parameters (BOD5, COD) and the major N and P species (NO3-, NO2-, NH4+, organic N, orthophosphates and total P) determined at 25 sampling sites located on main rivers, tributaries, streams and ditches that drain the major rural, agricultural, urban and industrial areas of N. Greece. Use of multivariate statistics is also made to identify the principal factors which influence the chemistry of the water in individual river systems. The eutrophication status of the examined systems was evaluated by means of N/P ratios. Mean N/P ratios showed large variations among sampling sites ranging from potential N- to P-limitation conditions. N/P ratios at particular sampling sites showed also great temporal variability thus suggesting temporary states of N- or P- limitation. Most frequently, highest ratio values were observed during winter and early spring. Comparisons are made between data from this study region and literature on rivers elsewhere.