Influence of technological and municipal wastewaters on vulnerable karst riverine system, Krka River in Croatia

Abstract

Exceptional natural value of karst rivers, as well as their potential as a source of drinking water supply, contributes to the importance of developing strict environmental protection. Although most of its watercourse is proclaimed national park, Krka River is impacted by technological and municipal wastewaters, which are released without proper purification only 2 km upstream of the park border. In order to assess water ecological status of the Krka River, vulnerability of karst ecosystem and potential threat to the Krka National Park, spatial and temporal variability of physico-chemical and microbiological water parameters, as well as concentrations of 25 total dissolved metals/metalloids were evaluated. All parameters indicated deteriorated water quality near the wastewater influences, which was for certain metals and bacterial counts even comparable to other world rivers of technological/rural catchment. Downstream location pointed to purification processes in karst river, although nutrients and conductivity were still in a range below good water quality and Al, Co, Fe, Li, Mn, Ni, Sr, Ti, and Zn levels remained comparable to their levels in the pollution impacted area, especially in autumn, indicating season-dependent processes. Presented data provided background status and identified pollution influences in the karst riverine system which indicated potential risk for protected area and a need for comprehensive water quality assessment.

Total and cytosolic concentrations of twenty metals/metalloids in the liver of brown trout Salmo trutta (Linnaeus, 1758) from the karstic Croatian river Krka

“…Nichols and Playle (2004) reported the positive influence of increased ambient temperature on Ag accumulation in the liver of O. mykiss, probably due to increased fish metabolic rates at higher water temperatures, whereas the same effect was not observed on Ag elimination; therefore, they found higher Ag concentrations in the liver of O. mykiss kept at higher compared to lower water temperatures. Although water temperatures in autumn and spring samplings are usually comparable (Filipović Marijić et al, 2017), higher hepatic Ag levels in S. trutta in the autumn compared to spring in our study could be explained by the fact that autumn sampling occurred after long period of high summer temperatures.…”

“…The association of Co with S. trutta length was negative and rather strong, meaning that higher concentrations were found in smaller specimens. However, this correlation was determined in both sampling campaigns only at the contaminated site, downstream of Knin town (r = -0.659 and -0.720; p<0.01), where Co accumulation in S. trutta liver was significantly higher compared to the reference site (Table 3), same as Co exposure level in the river water (Table 1; Filipović Marijić et al, 2017;Sertić Perić et al, 2017). Therefore, it can be presumed that in the conditions of increased exposure to Co, smaller S. trutta specimens accumulate higher amounts of this metal than the bigger ones.…”

Comparison of electrochemically determined metallothionein concentrations in wild freshwater salmon fish and gammarids and their relation to total and cytosolic metal levels

“…Based on the previously published data on the physico-chemical water parameters and total dissolved metal levels in the river water (Cukrov et al, 2008;Filipović Marijić et al, 2018), river source was chosen as the reference site, whereas a location downstream of the town of Knin, located 2 km upstream of the northern border of the Krka National Park, was selected as the contaminated site. Krka River is threatened by two known sources of contamination: technological wastewaters of the screw factory and municipal wastewaters of the town of Knin.…”

“…The wastewaters are released without a proper treatment into the river watercourse just 2 km upstream of the border of the Krka National Park. Krka River water analyses conducted upstream and downstream of the wastewater discharge have shown that metal/metalloid concentrations were increased at the affected site Filipović Marijić et al, 2018;Sertić Perić et al, 2018). Dissolved metals in water with the highest concentrations at the anthropogenically impacted site were Fe, Li, Mn, Mo, Sr, Rb and Ca and among them Fe and Mn are metals specific for technological wastewaters and often used in the manufacture of iron and steel alloys, and manganese products Filipović Marijić et al, 2018;Sertić Perić et al, 2018).…”

“…Krka River water analyses conducted upstream and downstream of the wastewater discharge have shown that metal/metalloid concentrations were increased at the affected site Filipović Marijić et al, 2018;Sertić Perić et al, 2018). Dissolved metals in water with the highest concentrations at the anthropogenically impacted site were Fe, Li, Mn, Mo, Sr, Rb and Ca and among them Fe and Mn are metals specific for technological wastewaters and often used in the manufacture of iron and steel alloys, and manganese products Filipović Marijić et al, 2018;Sertić Perić et al, 2018). All measured physico-chemical water parameters indicated slightly deteriorated environmental conditions at the site downstream of wastewater discharge, of which temperature, conductivity, total dissolved solids and total water hardness showed significant between-site differences (Sertić Perić et al, 2018).…”