This study evaluated the surface water quality of selected Danube River sectors (km 549-990) in the RO13 Cazane–Călărași area using direct field measurements. The research was conducted within the framework of the national project “Optimizing the sustainable management of natural resources, enhancing water security, and increasing the resilience of ecosystems in the Lower Danube Basin, impacted by climate change and anthropogenic interventions” (PN 23 30 03 03).
A multiparameter EXO 2 probe (YSI, USA) was used to analyze key physico-chemical parameters, while hydrocarbon concentrations (Oil in Water and HC micro-g/L) were assessed using PAH probes. Results indicate that most water quality parameters remain within environmental standards, classifying the waters as either "Very Good" or "Good." Temperature (15.03–24.40°C) and pH (7.92–8.36) remained stable, while dissolved oxygen levels (7.01–9.43 mg/L) and chlorophyll concentrations (0.27–1.49 RFU) suggested low risk of eutrophication. Conductivity (262.53–411.56 µS/cm), TDS (207.56–280.80 mg/L), and salinity (0.15–0.21 psu) confirmed freshwater conditions. Turbidity values (2.44–28.75 FNU) and oxidation-reduction potential (-26.59 to 238.79 mV) indicated relatively stable conditions. Hydrocarbon levels (0.03–1.46 mg/L) were within acceptable environmental limits, though localized variations suggested potential pollution sources. These findings emphasize the need for long-term monitoring and transboundary collaboration to address localized pollution concerns and ensure sustainable water management in the Danube Basin