## 6 General Overview  
Continuous monitoring over the last two decades, either through point surveys or complex surveillance programs covering several years, has led to changes and continuous updates of the legislation (e.g., Commission Decisions EU 2018/840 [26] and 2020/1161 [45]), to the development of large substances databases (e.g., NORMAN [60]), and to new approaches in pollutant prioritization and risk assessment methodology [33]. The literature on monitoring programs of organic and inorganic pollutants published during 2010-2021 for the Lower Danube basin and North West Black Sea region show that this research area has been extended in the last year (Figure 8 due to the higher concern of political entities and, on the other hand, the development of more sensitive analytical techniques. Some observations on the cited studies include:  
* Most of the papers focused on the active substances and only a few on the metabolites or biodegradation products [15; 26; 39; 49; 53];  
Figure 8: Frequency of reports by year (2010–2020), dealing with monitoring of the emerging contaminants, and persistent pollutants. Studies are repetitive, which is helpful in terms of pollutants dynamics but, on the other hand, not only the most frequently studied substances should be considered but also those with high risk and relevance for the environment;
* Most of the authors reported occurrence of CECs without justifying the selection of compounds. Criteria as \"substances that commonly have been detected\" or \"ubiquit presence\" were appealed. Priority substances listed by the EU regulations or NORMAN databases were mentioned in four papers [26,44,51,77];
* Insufficient attention was paid to the natural variability of the aquatic environment, leading to inadequate data collection (e.g., substances that are susceptible to degradation caused by sunlight exposer or absorption of the pollutant on suspended particulate matter were rarely discussed). One paper concerning CECs analysis in suspended particulate matter was identified [45];
* The majority of the reviewed studies concerning CECs monitoring were based on 'grab-sampling' often with no intra-day repetition. The limitations of such an approach results in snap shots data on pollutant concentration for a specific point in time. Composite sampling that considered flow fluctuations was performed in 1 of 24 studies [15]; furthermore, chemical stability of the target analytes during storage until analysis was investigated in only one study [45];
* Few antibiotics are usually monitored in the studies cited in Table 1 (pharmaceuticals) despite the risk posed to aquatic and terrestrial organisms and possible occurrence of bacteria resistance;
* The analytical approach of targeted screening with low resolution mass spectrometry (e.g., triple quadrupoles) used in the majority of reviewed studies resulted in numerous substances such as metabolites or transformation products going undetected. Among 24 studies concerning CECs monitoring, tentative identification using HRMS-MS was carried out in one publication [26]. Multiresidue methods allowing targeted (quantitative) and non-targeted (qualitative) screening should become standard procedures for CECs analysis as well as combining analytical methods with metabolomics for the identification of uncommon chemicals, metabolites, and degradation product(s);
* To determine and predict trends, multivariate statistical methods (factor analysis of principal component analysis (PCA) were applied as well as indicators of pollution status, as Hazard Quotient (HQ), Enrichment Factor (EF), Geo-accumulation index (Igeo), and Ecological risk index (RI) were determined in several papers concerning persistent pollutants as PAHs, OCPs, and metals [2,46,51,84,100,107,121,144];
* Regarding CECs, the basis for risk assessment was rarely discussed.