engleski

Assessment of Water Quality and Metal Exposure in the Krka River Watercourse (Croatia) Influenced by the Wastewater Outlets

Due to its travertine waterfalls, many cascades and lakes, very rich and diverse flora and fauna, the Krka River represents exceptional natural value in the Republic of Croatia and worldwide. In accordance, middle and lower course of the river were proclaimed Krka National Park (KNP). Only 2 km upstream of the park border municipal and industrial wastewaters, which are released without proper purification, may threaten living world and tufa barriers of this karst phenomenon [1]. The aim of the present study was to evaluate water quality and metal exposure by means of physico- chemical water parameters (turbidity, conductivity, total dissolved salts, chemical oxygen demand, ammonia, nitrates, nitrites, total nitrogen and total phosphorus) and dissolved metal levels (Al, As, Cd, Co, Fe, Hg, Li, Mn, Mo, Ni and Zn). Sampling was performed at eight locations: Krka River source (KRS) as reference site ; tributary Krčić (TKR) ; industrial wastewater (IWW) ; municipal sewage of the Town of Knin (KRK) ; tributary Orašnica (TOR), impacted by industrial wastewater ; tributary Kosovčica (TKO), nearby Knauf factory ; tributary Butišnica (TBU), influenced by agricultural runoff and Brljan Lake (KBL), located in the KNP. Sampling campaigns were conducted in April and July 2021, as two seasons of higher and lower water level, respectively. Physico-chemical parameters were measured in situ and by Standard Methods for the Examination of Water & Wastewater, while metals were measured by high resolution inductively coupled plasma-mass spectrometry (HR ICP-MS). Water quality was estimated following the Directive on water quality status [2]. Chemical water status was the lowest in industrial effluents (IWW) in both sampling campaigns, which were therefore confirmed as a serious threat to the river water. Physico- chemical water parameters (especially chemical oxygen demand, ammonia, total nitrogen and phosphorus) also pointed to deteriorated water quality at anthropogenically impacted locations (TKO, KRK, TOR, TBU) but also at KBL, which is situated within KNP. Dissolved metal levels, especially of Mn, Fe, Co and Ni, showed the highest increase at IWW, TOR, KRK and TKO compared to KRS in both seasons. Those metals are known by their use in industry and confirmed potential impact of IWW to the Krka River and its tributaries. Only Hg levels were low at all sites, even below limit of detection. Concentrations of most metals were higher in July than April at all sampling sites, probably due to lower water level in the summer period. Presented results indicated the influence of direct pollution sources and emphasized its potential threat to the preservation of the natural beauties of the Krka River. Therefore, proper purification of the wastewaters and implementation of water quality monitoring strategies of the Krka River are required. Acknowledgements The financial support of the Croatian Science Foundation for the project: “Integrated evaluation of aquatic organism responses to metal exposure: gene expression, bioavailability, toxicity and biomarker responses (BIOTOXMET)” (IP-2020-02-8502) is highly acknowledged.

national park ; karst river ; anthropogenic impact ; trace elements ; nutrients ; water ecological status

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