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Water quality is assessed through the biological, physical and chemical parameters. The limits of these parameters that are harmful to human health have been established at national or international level (WHO, EPA, MECC) by various laws, regulations, normative. An efficient and simplified to express the quality of water for consumption is given by the water quality index. It reflects the quality of water in a single value by comparing data obtained from the investigation of a number of physico-chemical and bacteriological parameters with existing limits. This number is placed on a relative scale to justify the quality of water in categories ranging from very poor to excellent. In this study are discussed various water quality indices used to assess the quality of drinking water (surface water). National and international agencies involved in assessing water quality and pollution control defines different quality criteria used for drinking water which is why there are many water quality specific indices for each region or area. In this context, it will present a comparative study of the most important quality indices used to assess water quality worldwide.

Environmental issues have a worldwide impact on water bodies, including the Danube Delta, the largest European wetland. The Water Framework Directive (2000/60/EC) implementation operates toward solving environmental issues from European and national level. As a consequence, the water quality and the biocenosis structure was altered, especially the composition of the macro invertebrate community which is closely related to habitat and substrate heterogeneity. This study aims to assess the ecological status of Southern Branch of the Danube Delta, Saint Gheorghe, using benthic fauna and a computational method as an alternative for monitoring the water quality in real time. The analysis of spatial and temporal variability of unicriterial and multicriterial indices were used to assess the current status of aquatic systems. In addition, chemical status was characterized. Coliform bacteria and several chemical parameters were used to feed machine-learning (ML) algorithms to simulate a real-time classification method. Overall, the assessment of the water bodies indicated a moderate ecological status based on the biological quality elements or a good ecological status based on chemical and ML algorithms criteria.

The Danube River is the major source of drinking water supply for the cities in the southern part of Romania. The study was a descriptive-analytical one and lasted for 9 month. Samples were taken monthly between March 2016 and November 2016. Six sampling sites were selected to evaluate the spatial and temporal changes of water quality along the river. The samples were analyzed based on the standard methods for the following parameters: pH, conductivity (EC), NH4+, NO3-, Cl -, suspended solids, PO43-, SO42-, metals (Fe, Cd, Cr, Pb, Ni, Hg, As, Zn, Cu, Mn). The obtained values were compared with those imposed by the Romanian environmental legislation. An efficient and simplified method to express the quality of water used for consumption is provided by the Water Quality Index (WQI). WQI reflects the quality of water in a single value by comparing data obtained from the investigation of a number of physico-chemical parameters to the existing limits. The evaluation of water quality was performed using the Water Quality Index of the Canadian Council of Ministries of the Environment (CCME WQI). Water quality indices were classified as: excellent, good, medium, bad and very bad. The results indicated the water quality classification as �good� in all six sampling selected sites.

The present study investigated the distribution and environmental fate of Bisphenol A (BPA), the 4‐hydroxyacetophenone (4‐HAP) metabolite, and 5 other bisphenol congeners in 2 municipal wastewater treatment plants (WWTPs) and their receiving rivers in Romania. Accordingly, a new, highly sensitive and accurate solid‐phase extraction–liquid chromatography–electrospray ionization–tandem mass spectrometry method was developed and validated. This technique generated low limit of quantitation values: below 2.3 ng/L for surface water and less than 2.4 and 2.7 ng/L for WWTP effluent and influent water. The sum of detected analytes in wastewater was between 1337 and 16 118 ng/L for influent samples and between 15 and 96 ng/L for effluent samples. In surface water, the total of all compounds was somewhere between 34 and 240 ng/L. The highest concentration observed was for BPA in all 3 types of analyzed water (up to 9140 ng/L for influent, as high as 75 ng/L for effluent, and a maximum of 135 ng/L in surface waters). All analyzed samples were free of bisphenols B, C, and F. For all analytes detected in surface water, the concentration values were higher than those determined in the effluent samples, which may be caused by intrinsic contamination of the 2 rivers (Danube and Jiu Rivers). Values of environmental risk coefficients, calculated for both effluents and surface waters, indicated a low ecological risk or no ecological risk for 3 types of organisms (algae, daphnia, and fish). Human risk assessment calculation suggests no risk to human health as a result of the presence of BPA in either of the 2 rivers. Environ Toxicol Chem 2021;40:435–446. © 2020 SETAC

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A simple, reliable and accurate HPLC/CAD method was developed for the determination of anionic (sodium dioctyl sulfosuccinate and sodium 1-dodecane sulfonate), amphoteric (CHAPS (3-[(3-Cholamidopropyl) dimethylammonium]-1-propanesulfonate hydrate)) and cationic (benzethonium chloride) surfactants mixture from surface water samples. The chromatographic analysis was performed on an Acclaim Surfactant Plus (150 x 3.0 mm, 3 mm d.p.) column acquired from Thermo Scientific, kept at 300C. All experiments were performed in gradient elution conditions at a flow-rate of 0.6 mL/min. Mobile phase composition was a mixture of acetonitrile (A) and 0.1 M ammonium acetate solution acidified to pH 5 with acetic acid (B). The limit of detection (LD) were 20 mg/L for anionic surfactants and 30 mg/L for cationic and amphoteric surfactants. The calibration curves were linear between 15 mg/L � 110 mg/L, with R2 values above 0.992 for all surfactants. Solid phase extraction (SPE) using polymeric (Strata X) cartridges has been applied to extract and concentrate the target analytes from the synthetic samples. Surfactants recoveries after SPE procedure were situated between 91.5�94.6%. Intra-day and inter-day precision (RSD%) were situated between 4.0 � 7.7% and 7.5 � 11.7%, respectively. Limit of quantitation (LQ) was lower than 80 mg/L for anionic surfactants and 90 mg/L for cationic and 100 mg/L for amphoteric surfactants. The new sensitive and selective HPLC/CAD developed method allows simultaneous determination of anionic, amphoteric and cationic surfactants mixture from environmental samples (surface water).

A liquid chromatography-tandem mass spectrometry (SPE-LC-MS/MS) method was developed and validated for the simultaneous determination of six organic compounds (2-hydroxy benzophenone, 4hydroxy benzophenone, 2,2',4,4'-tetrahydroxy benzophenone, 2,4-dyhydroxy benzophenone, 4,4'dyhydroxy benzophenone, 2,2'-dyhydroxy-4-methoxy-benzophenone) used as UV filters in personal care products used to protect against UV radiation. The major concern about this type of pollutants is due to their persistence and bioaccumulation potential in the environment and aquatic organisms and for their endocrine disruptor properties. Solid phase extraction was used for sample preparation, followed by liquid chromatography tandem mass spectrometry analysis. Benzophenone derivatives were analyzed on a Phenomenex Luna C18 column (150 x 2.0 mm, 3.0 µm) with the mobile phase run in gradient mode with a mixture of aqueous 0.1% formic acid and acetonitrile as the mobile phase components (at a flow rate of 0.2 mL/min). MS detector response was linear, on the tested concentration domain from 1 to 100 μg/L with correlation coefficient R 2 > 0.998. The recoveries of benzophenone derivatives after solid phase extraction procedure from surface water was found to be >81% for surface water and higher than 79% for wastewater matrix. The standard deviation values for intra-day precision were situated between 7.67% and 9.88% for lower concentration and 7.27% and 8.86% for higher concentration respectively. The limits of quantitation were calculated for both environmental water matrices (1.6-4.1 ng/L for surface water and 3.3-8.2 ng/L for wastewater). This method can be applied for benzophenone derivatives detection in real environmental samples.