ASSESSMENT OF WATER QUALITY CHANGES OF ZAGOZDZONKA RIVER IN TERMS OF SELECTED PHYSICOCHEMICAL INDICATORS

The results of analysis for two measurement profiles monitored in terms of the concentration of phosphate, total phosphorus and nitrate during years 1991-2010 shows changes in the concentrations. Analyses were performed in three periods for the Czarna profile in years 1991-1995, 1999-2000 and 2008-2010, and two periods for the Plachty Stare profile in 1991-1995 and 2008-2010 at lowland Zagozdzonka river (central Poland). Based on water quality classification percentage, of samples fulfilled certain limits, has been compared between investigation periods. The dissolved phosphorus concentration shows improvement during last period what has been seen in percentage of samples which do not fulfilled requirements for II class water quality. For Czarna profile, the percentage of those samples has been reduced from 69% to 28% and for Plachty Stare profile from 64% to 24%. In the case of total phosphorus concentrations, the percentage of sample meeting requirements for water quality class I raised form 1% d o16% at Czarna profile and from 5% to 84% for Plachty Stare profile. In the case of nitrate concentration, deterioration of water quality has been noticed. During the first measurement period the 87% (Czarna profile) and 91% (Plachty Stare profile) met the requirements for first class water quality, but during the last measurement period this percentage drops till 57% for Czarna profile and 58% of for Plachty Stare profile. There has been a big improvement in the water quality in terms of phosphates determined by comparing of the mean percentage of samples which do not meet the limit values for water quality class II (unclassified) over the periods in which the studies were conducted.