Scholarly record
ASSESSMENT OF SURFACE WATER QUALITY ALONG THE SFANTU GHEORGHE BRANCH (DANUBE DELTA) UNDER NATURAL AND ANTHROPOGENIC INFLUENCES
Abstract
This study assesses surface water quality along the Sf. Gheorghe Branch of the Danube Delta (km 85-km 15) and adjacent control sectors, in order to assess the influence of both natural processes and anthropogenic pressures on aquatic environmental conditions. In situ measurements were performed at 97 stations during the June and September 2025 campaigns using a YSI EXO2 multiparameter probe. The monitored indicators were temperature, pH, dissolved oxygen, conductivity, total dissolved solids, salinity, turbidity, oxidation-reduction potential and chlorophyll fluorescence. The dataset shows clear seasonal and spatial variability throughout the study area. Water temperature was higher in June and lower in September, reflecting normal seasonal cooling, while pH values remained generally neutral to slightly alkaline, indicating stable buffering conditions. June values showed higher temperature and, at several confined or weakly flushed sites, markedly higher mineralization. Turbidity and ORP displayed the strongest local contrasts, reflecting sediment resuspension, channel morphology, navigation disturbance, reduced water exchange and diffuse runoff inputs. Spatial differences in turbidity and redox conditions were more pronounced and appeared to be linked to sediment resuspension, channel hydrodynamics, navigation-induced disturbance, and local runoff inputs. These patterns indicate that the water quality of the Sf. Gheorghe Branch is shaped by the interaction between natural hydrological and sedimentary processes and anthropogenic influences, including local human activity, modified flow conditions, and diffuse nutrient or sediment inputs. The investigated sector maintained good ecological status, with most observations consistent with Class I-II quality conditions under Romanian Order 161/2006 and only localized signs of pressure.
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