EFFECTS OF MULTIPLE SOURCE POLLUTION ON A SMALL MEDITERRANEAN RIVER

The small Mediterranean riverine system of the Litheos river, which fl ows through the city of Trikala, and its drainage area are subjected t o pollution from point and non point sources, which results in poor qu ality of surface waters. The pollution sources include urban activitie s, agriculture, industrial activities, handicrafts and traffic. The co ncentration levels and the geochemical behaviour of nutrients, trace m etals and organic pollutants were studied during the period 1991-1992, in a project supported by the Municipality of Trikala. The simultaneo us existence of several polluting sources leads to significant variati ons in the concentrations and distributions of main pollutants, which are elevated in the neighbourhood of polluting activities in various p arts of the river (NO3- above the city, NH3, NO2- and detergents near central rainwater collector, into the city, PO4 below the city, near t he waste water treatment plant, PAHs and metals in another river branc h in the 'industrial' zone of the city). The appearance of concentrati on maxima of various pollutants in various parts of the river indicate s environmental problems in the whole length of the river. The water q uality is significantly influenced and in most cases is unsuitable for human consumption. The mean values of the main pollutants in Litheos (NO3- 4.0 mg N/l, NH3 0.23 mg N/l, NO2- 0.10 mg N/l, P 0.37 mg P/l, Cu 7.1 mu g/l, Pb 4.8 mu g/l, Zn 3.9 mu g/l, Ni 12.8 mu g/l, Cr 3.5 mu g /l) characterize Litheos as a moderately polluted river, but the obser vation of eutrophication phenomena and the appearance of some high con centrations of heavy metals and/or organic pollutants in certain parts of the river reveal that a serious effort must be made in order to av oid further deterioration of Litheos water quality. (C) 1998 Elsevier Science Ltd. All rights reserved.