A year-long study from May 2018 to April 2019 investigated the spatio-temporal changes in water quality of seven major rivers in the Giresun Province in northeastern Turkey. The results of the analysis were classified according to WHO limit values for drinking water and water quality classes were determined with respect to the Turkish Surface Water Quality Regulation (TSWQR). In addition, sodium percentage (% Na), sodium absorption ratio (SAR), magnesium hazard (MH), and residual sodium carbonate (RSC) values were calculated to evaluate the eligibility of the streams for irrigation purposes. Multivariate statistical analysis methods such as one-way ANOVA, Pearson correlation index (PCI), cluster analysis (CA), principal components analysis/factor analysis (PCA/FA) were used to determine the differences and similarities of streams, pollution sources and relations between parameters. As a result of the PCA, four factors accounted for 71.52% of all factors. These factors show that the major changes in water quality parameters were associated with point-based pollution such as wastewater from household and industrial resources, non-point sources such as agricultural activities and natural phenomena such as flooding, rock and soil erosion. The pH values in the range of 7.77 to 9.8 were slightly alkaline compared to the TSWQR range of pH 6–9. In certain months, the average NO₂-N values (> 0.06 mg/L) in Batlama Stream, Aksu Stream, Yağlıdere Stream and Gelevera Stream was class III (medium) water quality and mean fluoride values in streams (1 and 1.19 mg/L) were class II water quality according to TSWQR. The levels of anionic surfactants in all streams were class III (polluted) water quality, except for Pazarsuyu Stream with class II (less polluted) water quality. The annual mean water quality index (WQI) values of the streams ranged from 25.69 (excellent) to 32.39 (good). When the water quality was evaluated for irrigation, the SAR, Na%, RSC and MH did not exceed the limit values. Based on these indices it was assessed that settlements and related anthropogenic activities along the riverbanks did not affect the water quality currently. This does not mean that it may not have an effect in the near future.

Water scarcity is a growing concern due to rapid urbanization and population growth. This study assesses spring water quality at 20 stations in Giresun province, Türkiye, focusing on potentially toxic elements and physicochemical parameters. The Water Quality Index rated most samples as "excellent" during the rainy season and "good" during the dry season, except at stations 4 (40° 35′ 12″ North/38° 26′ 34″ East) and 19 (40° 44′ 28″ North/38° 06′ 53″ West), indicating "poor" quality. Mean macro-element concentrations (mg/L) were: Ca (34.27), Na (10.36), Mg (8.26), and K (1.48). Mean trace element values (μg/L) were: Al (1093), Zn (110.54), Fe (67.45), Mn (23.03), Cu (9.79), As (3.75), Ni (3.00), Cr (2.84), Pb (2.70), Co (1.93), and Cd (0.76). Health risk assessments showed minimal non-carcinogenic risks, while carcinogenic risk from arsenic slightly exceeded safe limits (CR = 1.75E−04). Higher arsenic concentrations during the rainy season were due to increased recharge, arsenic-laden surface runoff, and human activities. Statistical analyses (PCA, PCC, HCA) suggested that metals and physico-chemical parameters originated from lithogenic, anthropogenic, or mixed sources. Regular monitoring of spring water is recommended to mitigate potential public health risks from waterborne contaminants.

Heavy metal pollution in the sediments of Çalışlar and Akçaova Streams may expose hazardous risk to environment and public health through food chain in Ordu province of southeastern Black Sea region of Turkey. The enrichment and distributions of the heavy metals in the sediments of these two streams demonstrated a decreasing trend in the mean heavy metal toxic levels in mg kg⁻¹ as follows Fe (8135.27) > Mn (272.56) > Zn (25.68) > Cu (13.03) > Co (5.13) > Pb (3.74) > Ni (3.62) > Cr (3.52) > Cd (0.005) in Çalışlar Stream and Fe (9939.12) > Mn (286.97) > Zn (24.24) > Cu (19.31) > Ni (10.95) > Co (6.2) > Cr (4.90) > Pb (3.97) > Cd (0.09) > Ag (0.07) in Akçaova Stream, respectively. The sum of the toxic units of Fe, Mn, Zn, and Cu in both streams were significantly higher. The assessment of sediment pollution was carried out using multivariate statistical approaches and indices such as enrichment factor (EF), contamination factor (CF), geoaccumulation index (I_geo), and potential ecological risk factor (E_rⁱ). The results of the cluster analysis in both streams showed that Co, Pb, and Cr were mainly associated with natural sources. EF values indicated that the average concentration of all metals from both streams were lower than potential effect levels with the exception of Cu, and Ag in Akçaova Stream. Relatively low levels of pollution indicators in Çalışlar Stream pointed out no environmental contamination and suggested that metal contamination sourced most likely from the naturally present minerals in the area. Akçaova Stream sediments were moderately contaminated with Cu (EF > 2), and significantly contaminated with Ag (EF = 5 − 20) according to the average EF values attributable to anthropogenic activities.