Development and Multi-laboratory Verification of US EPA Method 543 for the Analysis of Drinking Water Contaminants by Online Solid Phase Extraction-LC-MS-MS

Yesterday's contamination-A problem of today? The case study of discontinued historical contamination of the Mrežnica River (Croatia)

The remnants of historical industrial contamination can be detected in many aquatic ecosystems worldwide even at present time. Mrežnica is a river in Croatia that has been, for more than a hundred years, continually exposed to effluents of various industries, which have, in modern time, mostly ceased to operate. Our aim was to establish the level of current contamination and pollution of the Mrežnica river-water and sediments. The study of river contamination at three sites (reference site; site nearby former cotton industry facility in Duga Resa - DRF; industrial zone of Karlovac town - KIZ) in three sampling campaigns (May 2020, April and September 2021) encompassed analyses of physico-chemical water parameters, screening of 369 pesticides, measurement of metal (loid) concentrations in the sediments, and in the dissolved and particulate phases of the river-water. The sediment pollution was assessed through the analyses of total bacteria abundance (by targeting 16S rRNA genes), and their associated metal resistance genes (cnrA, pbrT and czcD) and class 1 integrons (intl1). At the DRF site, industrial organic contaminants that can be traced to textile production were detected (dye and nylon components), as well as increased levels of some metals bound to suspended particulate matter and sediments. At the most downstream KIZ site, occasional high level of industrial herbicide neburon was measured in the river-water, and metal contamination of suspended particulate matter and sediments was evident. Although, based on the comparison with legislation and literature data, the level of contamination was rather mild, the effects on microbial communities were unquestionable, confirmed by increased abundance of the czcD gene at DRF site and the intI1 gene at both industrially impacted sites. Obtained results indicated long-term sediment retention of some industrial contaminants at the places of historical freshwater contamination, and, thus, the necessity for their monitoring even after the termination of contamination sources.

COVID-19 Lockdowns-Effect on Concentration of Pharmaceuticals and Illicit Drugs in Two Major Croatian Rivers

In order to prevent the spread of COVID-19, contingency measures in the form of lockdowns were implemented all over the world, including in Croatia. The aim of this study was to detect if those severe, imposed restrictions of social interactions reflected on the water quality of rivers receiving wastewaters from urban areas. A total of 18 different pharmaceuticals (PhACs) and illicit drugs (IDrgs), as well as their metabolites, were measured for 16 months (January 2020-April 2021) in 12 different locations at in the Sava and Drava Rivers, Croatia, using UHPLC coupled to LCMS. This period encompassed two major Covid lockdowns (March-May 2020 and October 2020-March 2021). Several PhACs more than halved in river water mass flow during the lockdowns. The results of this study confirm that Covid lockdowns caused lower cumulative concentrations and mass flow of measured PhACs/IDrgs in the Sava and Drava Rivers. This was not influenced by the increased use of drugs for the treatment of the COVID-19, like antibiotics and steroidal anti-inflammatory drugs. The decreases in measured PhACs/IDrgs concentrations and mass flows were more pronounced during the first lockdown, which was stricter than the second.