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The appearance of COVID disease and the introduction of subsequent measures and specific medical treatments throughout the world in 2020 could have been expected to cause the drug content changes in the surface waters. We have studied the lower course of the Croatian Mrežnica River at three areas (rural, small town, and large town domains) in three periods (May 2020, April and September 2021). The applied method was liquid chromatography with tandem mass spectrometry, which enabled the screening of 256 compounds with 7-9% (19-24 drugs) being detected, depending on the sampling period. In the beginning of the pandemic, total quantity of drugs was much lower in the rural and small town domain (142-187 ng L- 1) compared to the large town (954 ng L-1), whereas by the autumn 2021 marked increase of drug levels in rural and small town areas was observed (443- 481 ng L-1). Increase was especially notable for analgesics: non-opioid (aminophenazon, acetaminophen, ibuprofen) and opioid (tramadol, oxycodone). In spring of 2020, nonopioids were detectable only in large town domain (94.3 ng L- 1), and their concentrations steadily increased throughout the pandemic (up to 172 ng L-1). In the vicinity of small town, sharp increase of nonopioids occurred already in spring 2021 (235 ng L-1) and in rural area in autumn 2021 (125 ng L- 1). The opioids appeared in the river water at all studied sites in the last sampling period (46-90 ng L-1). Contrary to analgesics, decrease in quantity was recorded for the stimmulants, i.e. coffeine and cotinine (nicotine metabolite), indicating less active socializing due to the COVID epidemiological measures.

Wastewater treatment plants are considered one of the main sources of organic micropollutants. Micropollutant continuous and unregulated release into the environment constitutes a threat to the water environment and human health. In this context, upgrading wastewater treatment seems a suitable option. In this paper, we study how to increase the removal efficiencies for 20 micropollutants by the addition of powdered activated carbon (PAC) to a full-scale membrane bioreactor mainly treating hospital wastewater. In addition, we study if PAC addition improves the overall quality of the final effluent and sludge flocs properties. A special focus is done on the influence of dissolved organic matter in the adsorption of the selected micropollutants on PAC.

The lower course of the Mrežnica River has long been exposed to different types of industrial loads. In Duga Resa, the cotton industry was active for more than a century, and a few kilometres downstream, industrial wastewaters of Karlovac entered the river until approximately a decade ago. Our aim was to determine the main inorganic and organic contaminants of river-water and sediments at two differently polluted sites compared to upstream reference site. Turbidity, chemical oxygen demand, and total nitrogen were somewhat increased in Karlovac, whereas total phosphorus was increased at the reference site. Although dissolved metal concentrations in the water were rather low, indicating a pristine river, an increasing trend towards Karlovac existed for several elements (e.g., Fe, Mn), where the highest metal concentrations in finer sediment fraction (

Quantitative chemical analyses of 428 organic contaminants (OCs) indicated the presence of 313 OCs in the sediment extracts from Sava River, Croatia. Pharmaceuticals were present in higher concentrations than pesticides thus confirming their increasing threat to freshwater ecosystems. Toxicity evaluation of the sediment extracts from four locations (Jesenice, Rugvica, Galdovo and Lukavec) using zebrafish embryotoxicity test (ZET) accompanied with semi-quantitative histopathological analyses exhibited correlation with cumulative number and concentrations of OCs at the investigated sites (10.05, 15.22, 1.25, and 9.13 μg/g respectively). Toxicity of sediment extracts and sediment was predicted using toxic unit (TU) approach and persistence, bioaccumulation and toxicity (PBT) ranking. Additionally, influential OCs and genes were identified by graph mining of the prior knowledge informed, site-specific chemical-gene interaction models. Predicted toxicity of sediment extracts (TUext) was similar to the results obtained by ZET and associated histopathology with Rugvica sediment being the most toxic, followed by Jesenice, Lukavec and Galdovo. Sediment TU (TUsed) favoured OCs with low octanolwater partition coefficients like herbicide glyphosate and antibiotics ciprofloxacin and sulfamethazine thus indicating locations containing higher concentrations of these OCs (Galdovo and Rugvica) as the most toxic. Results suggest that comprehensive in silico sediment toxicity predictions advocate providing equal attention to organic contaminants with either very low or very high log Kow.

Toxic unit(TU)approach is currently currently prevailing in risk assessment of freshwater pollution (Ginebreda et al., 2014 ).It is defined as the the ratio between measured concentration of organic contaminants contaminants (OCs) in the water wand toxicological endpoints endpoints for aquatic organisms gathered from databases or by in - silico tools tools. To accentuate the importance of assessing both uptake paths in process of pollutant prioritization present in the the aquatic environment we propose an extension of the TU approach, by adding a factor containing the octanol-water partition coefficient as an estimator for lipid-water partitioning, sediment concentration and toxicity. It results in an estimative prioritization index, combined toxic unit (CTU). More effort must be invested in understanding diverse uptake paths of OCs into aquatic organisms. The CTU is an estimative index emphasizing both highly hydrophilic and lipophilic OCs no matter the uptake path.

Intensive agriculture is putting great pressure on the environment and therefore it is vital to rationalize its inputs, and to control and monitor the impact agricultural activities have on soil, water, and air, in order to achieve sustainability. For better understanding of the impact that conventional agricultural practices have not only on soil, but on water resources as well, two main objectives were established. The first one is to measure concentrations of nitrate (NO3-) and sulfate (SO42-) in lysimeter and drainpipe waters related to different nitrogen fertilization levels. The second one is to identify organic pollutants that potentially originate from used agrochemicals. The results of two-year investigating period (2014-2015) are presented in this study. The experimental field was established in Potok near Popovača on distric Stagnosols. The research contained ten treatments with four replications where different nitrogen fertilizer levels were applied: 1. Control (no fertilization), 2. N0 + P + K, 3. N100 + P + K, 4. N150 + P + K, 5. N200 + P + K, 6. N250 + P + K, 7. N250 + P + K + phosphogypsum, 8. N250 + P + K + zeolitic tuff + CaCO3, 9. N300 + P + K, and 10. Black fallow – tillage only. Phosphorous (P) and potassium (K) levels were constant, 120 and 180 kg/ha respectively. Each treatment area included two drainpipes (placed at the depth of 120 cm) and one lysimeter (at the depth of 80 cm) from which water samples were taken when discharge appeared. During the investigated period, 24 water samples for inorganic (13 from lysimeters and 11 from drainpipes) and 16 for organic substances analysis (six in 2014 and two in 2015 from lysimeters ; five in 2014 and three in 2015 from drainpipes) were taken. The concentrations of NO3- and SO42- were determined by suppressed ion chromatography (Dionex ICS-1000 system) using IonPac AS17-C separation column fitted with IonPac AG17 guard column. The gradient flow analysis was conducted using KOH as an eluent solution (10-30-10 mmol). Ultra-high performance liquid chromatography (UHPLC) coupled to time-of-flight mass spectrometry (Q- TOF/MS) was used for non-target screening and quantification of organic substances. This allowed the search of the entire spectrum of various organic compounds and their quantification at high resolution (> 10000 FWHM, full width half maximal), with accurate mass accuracy (< 1 ppm) and satisfactory sensitivity in fullacquisition mode. Research results indicated that NO3- content in both lysimeters and drainpipes increased with rising doses of N fertilizer. In the investigated period the daily concentration varied from 0.52–265 mg/L in both lysimeters and drainpipes, depending on the treatment, precipitation and agrotechnical measures. Higher average concentrations for each treatment were observed in water samples from drainpipes (up to 126 mg/L), which are placed deeper in the soil (120 cm) confirming that nitrates do not bond with soil particles and are leached into groundwater. Daily SO4 2- concentrations varied from 1-302 mg/L. As expected, the maximum average concentrations were recorded in treatment 7 with added phosphogypsum (184 mg/L in lysimeters and 105 mg/L in drainpipes), while the average concentrations on all other treatments were low (< 20 mg/L). Non-target screening revealed more than 400 different organic substances (agrochemicals, hormones, opioids, antibiotics and various other drugs) in water samples. The correlation with applied plant protection products was not observed. The focus of this study was three herbicides: atrazine, simazine, and isoproturon. Atrazine and simazine have been banned in Croatia since 2004, while isoproturon is still used. The average annual concentrations of atrazine, simazine and isoproturon in water from lysimeters in 2014 were 1.40, 0.20 and 0.21 μg/L, respectively. In drainpipes the concentrations were 0.44, 0.20 and 0.04 μg/L, respectively. The average annual concentration of atrazine, simazine and isoproturon in lysimeters in 2015 was 4.69, 8.70 and 0.78 μg/L, respectively. In drainpipes the concentrations were 0.82, 3.82 and 1.66 μg/L, respectively. Due to the fact that atrazine and simazine have not been used in Croatia since 2004 and there have been no records of isoproturon use in the investigated area since 1997, it can be assumed that these compounds persist in the environment for a considerable length of time.

Acinetobacter baumannii is an emerging hospital pathogen causing outbreaks in Croatia since 2002 and is still present in Croatian hospitals. Clinical isolates of A. baumannii in Croatian hospitals are usually multi-drug resistant(MDR), with resistance to carbapenems dramatically increasing from 10% in 2008 to 82% in 2014. Although A. baumannii has been isolated from patients and hospital environment during outbreaks, crucial questions regarding its epidemiology remains incompletely understood. The aim of this study was to screen the hospital and municipal wastewater of the City of Zagreb for the presence of viable A. baumannii and carbapenems. Sampling of hospital wastewater was performed on 2 occasions in 2015 at the central manhole of one Zagreb’s hospital from which the clinical isolates of A. baumannii were recovered. Sampling of municipal wastewater was performed on 6 occasions in 2014/15 at the influent and effluent of the central Zagreb’s wastewater treatment plant. Concentration of carbapenems in wastewater was measured by UHPLC Q-TOF MS. The isolation of A. baumannii from wastewater was performed at 42C/48h on CHROMagar Acinetobacter without or with the addition of commercial supplement CR102 which allows the growth of carbapenem- resistant isolates. Presumptive A. baumannii colonies were characterized phenotypically, by using Vitek2 system, and MALDI-TOF MS. Antibiotic resistance profiles were determined by Vitek2 system and interpreted according to EUCAST criteria. Hospital and municipal wastewaters contained high concentrations of imipenem and meropenem which averaged: 894 and 129ng/L in hospital wastewater, 3060 and 380ng/L in raw and 497 and 311ng/L in treated municipal wastewater, respectively. From hospital wastewater, raw and treated municipal wastewater 8, 30 and 7 isolates of A. baumannii were recovered, respectively. All isolates from hospital wastewater and majority (33/37) of isolates from municipal wastewater were resistant to carbapenems and majority of tested antibiotics except colistin. The 7 MDR clinical isolates recovered in the same period showed comparable levels of antibiotic resistance to MDR isolates from hospital and municipal wastewater. These suggest that A. baumannii is able to survive in environment outside hospitals. However, 4 isolates from raw municipal wastewater were susceptible to carbapenems and other antibiotics. This finding opens the possibility that A. baumannii could have natural habitat in sewage system.

Pharmaceuticals are complex molecules with different physicochemical and biological properties and functionalities. Although they are present in the aquatic environment in low (ng/L) concentrations, they are continually being released into the environment what can lead to unwanted effects on the living organisms. Many studies showed that the main points of collection and subsequent release of pharmaceuticals into the environment are wastewater treatment plants, suggesting that their upgrade and implementation of advanced treatment technologies are required. One of the possible solutions for degradation and/or removal of pharmaceuticals from the wastewaters is the use of advanced oxidation processes (AOP) as an additional treatment step. In this study the degradation of albendazole (ALB) was investigated using three UV based processes (with 185/254 and 365 nm radiation sources): (i) UV photolysis, (ii) UV photocatalysis (UV light + TiO2 nano film) and (iii) UV+O3 process. Screening of albendazole and related degradates was performed using liquid chromatography tandem mass spectrometry (HPLC- MS/MS) and ultra high performance liquid chromatography quadrupole time-of-flight mass spectrometry (UHPLC-QTOF-MS) with direct injection. The fastest degradation of ALB, for both UV-C and UV-A radiation, was obtained by UV+O3 process with removal efficiency higher than 90%, achieved in 10 minutes. Although the slowest degradation of ALB was obtained using UV-A processes, they have a potential for practical use since they could use natural solar radiation as a source of UV-A radiation and therewith significantly reduce the price of the treatment step.