The Pollution Load by Nitrogen and Phosphorus in the Cetina River

摘要

The objective of the investigations of the Cetina River, located in southern Croatia, was to record specific characteristics and properties of the Cetina waters at nine stations. In addition to measurements undertaken in the Cetina River, the water quality of its most significant springs and tributaries, such as Kosinac, Silovka, Studenci and Mala Ruda, Velika Ruda and Grab, has also been measured. The water quality in the Cetina watershed has been evaluated in the following storage reservoirs: Peruca, Busko Blato and Prancevici. The nitrogen compounds and phosphorus concentrations have been estimated at all these sampling sites over a 3-year period (2005-2008). Concentration levels at the Cetina-Vinalic sampling site for total N (from August 2005 to December 2008) ranged from 0 to 1.759 mg/L, for NH_3-N from 0 to 0.374 mg/L, for NO_3-N from 0.063 to 0.916 mg/L and for PO_4-P from 0 to 0.099 mg/L. The results prove that the Cetina-Vinalic sampling site is not polluted by nitrogen and phosphorus compounds. The river section from Trilj to the Prancevici dam, where the water is used for the water supply of Omis, Makarska and Dalmatian islands, has beenrnpolluted by wastewater because the majority of agricultural area, roads, industry and settlements are located upstream of it. The highest concentration for total N of 1.128 mg/L and of 1,527 total coliforms in 100 mL, expressed as a mean value for a 3-year period of investigations, was found at the sampling site Trilj. The results of concentration changes at the Cikotina Lada and Cetina Radmanove Mlinice sampling sites show no regularities. The highest concentration for total N of 0.941 mg/L was measured at the Cetina Radmanove Mlinice during 2007. The highest concentration for NO_3-N of 0.916 mg/L was measured at the same sampling site. According to the investigations of the water quality of the Cetina springs and tributaries, the bacteriological most polluted river spring is Kosinac, and the bacteriological most polluted river tributary is Grab. With reference to the water quality in the Cetina storage reservoirs, it may be concluded that the lowest quality standard has been found within the Prancevici storage reservoir regarding nitrogen compounds and phosphorus concentration levels.