Surface Water Contaminants (Metals, Nutrients, Pharmaceutics, Endocrine Disruptors, Bacteria) in the Danube River and Black Sea Basins, SE Romania

The assessment of surface water quality of the Danube River and Black Sea was performed taking into account the amounts determined for heavy metals (As, Cd, Cr, Cu, Hg, Mn, Ni, Pb, Zn), nutrients (compounds of N and P, chlorophyll a), emerging contaminants (CECs) (pharmaceutics and endocrine disruptors—19 quantified compounds, out of 30 targeted chemicals), heterotrophic bacteria and total coliforms, in thirty-two locations from the lower Danube sector (starting with km 375 up to the river mouths), the Danube Delta Biosphere Reserve (three Danube branches—Chilia, Sulina, and Sf. Gheorghe) and the Romanian coastal area of the Black Sea. The heavy metals levels were found in the following ranges: 3.0–6.5 μg/L As; 0.51–1.32 μg/L Cd; 21.6–61.2 μg/L Cr; 10.2–28.6 μg/L Cu; 196–351 μg/L Mn; 12.3–47.67 μg/L Ni; 5.2–15.5 μg/L Pb; 44–74 μg/L Zn; 0.01–0.08 μg/L Hg. The nutrient concentrations vary in the intervals: 0.04–0.45 mg/L N-NH4; 0.01–0.06 mg/L N-NO2; 0.07–1.9 mg/L N-NO3; 1.0–3.2 mg/L N total; 0.01–0.05 mg/L P-PO4; 0.02–0.27 mg/L P total, and 0.8–17.3 μg/L chlorophyll a. The concentrations of CECs from various classes (sulfamethoxazole, trimethoprim, ciprofloxacin, flumequine, amoxicillin, cefuroxime, dicloxacillin, carbamazepine, pravastatin, erythromycin, piroxicam, ketoprofen, diclofenac, naproxen, enilconazole (imazalil), clotrimazole, drospirenone, 17α-ethinylestradiol, and bisphenol A) were compared with values reported for European rivers and the Danube River water in various river sectors. The highest detection frequencies were registered for bisphenol A (100%), sulfamethoxazole (96%), carbamazepine and diclofenac (87%), trimethoprim (78%), pravastatin (46%), and imazalil (34%). Bisphenol A exhibited the largest concentrations (342 ng/L), followed by diclofenac (132 ng/L), carbamazepine (38 ng/L), and sulfamethoxazole (36 ng/L). For most of the contaminants, Black Sea coastal water showed lower concentrations than the Danube water and good ecological status for surface water. Correlations between CECs and total coliforms suggest insufficient treated wastewater effluents as a common contamination source and possible use of CECs as indirect fecal pollution indicator in aquatic systems. This is the first study carried out in the connected system Danube River–Danube Delta–Black Sea for a large palette of toxicants classes and microbial pollutants, which will serve as a baseline for future monitoring of water quality in the region.