Assessment of the macrophyte flora, ecological quality, heavy metal risks and phytoremediation potential of the kovada lake and kovada channel (Isparta)

This thesis study was carried out in two different periods. The first study period was conducted between July 2021-April 2022, and aimed to determine heavy metal contamination in the water, sediments and in aquatic plants Ceratophyllum demersum and Myriophyllum spicatum growing in Kovada Lake, using various indices. The second study period was carried out between June 2024-October 2024 aimed to determine the water quality of Kovada Lake and the Kovada Channel based on some physicochemical parameters and macrophyte indices. In the first study period, water, sediment, Ceratophyllum demersum and Myriophyllum spicatum were taken from 4 stations in Kovada Lake. The concentrations of some heavy metals (Cd, Cr, Cu, Fe, Mo, Mn, Ni, Pb, Se, Zn) were measured in water, sediment and plant samples collected seasonally. In the water samples, temperature (C), pH, electrical conductivity (µS/cm) and dissolved oxygen (mg/l) values were determined. Water quality classes were determined according to SWQR (Surface Water Quality Regulation) using physicochemical parameters and heavy metals measured in water and compared with standard values in TS 266, WHO, EPA and EU. The relationship between the physicochemical parameters and heavy metals determined in the water was evaluated using the Pearson correlation analysis. Heavy metal contamination in the water assessed using the water quality index (WQI), heavy metal pollution index (HPI) and heavy metal evaluation index (HEI). Heavy metal contamination in the sediment was assessed using sediment quality guidelines (SQG), contamination factor (CF), contamination degree (Cd), modified contamination degree (mCd), enrichment factor (EF), geo-accumulation index (Igeo), pollution load index (PLI), toxic risk index (TRI), modified ecological risk factor index (mER), modified potential ecological risk index (mPER), hazard quotient (HQ), hazard index (HI) and lifetime cancer risk index (LCR). To determine the potential use of the plants for phytoremediation, the bioaccumulation factor (BF) and translocation factor (TF) were calculated. When the results were evaluated generally, the metal concentrations in water increased during the summer and decreased in spring. In the sediment they increased in autumn and decreased during the summer. It was determined that the lake water was in the very poor water category in summer and in poor water category in other seasons according to WQI, and was in low level metal pollution class in all seasons according to HPI and HEI. It was determined that the lake sediment was classified as moderately polluted in summer and higly polluted in other seasons according to Cd, as moderately polluted in spring and lowly polluted in other seasons according to mCd, as polluted in spring but not in other seasons to PLI, as presenting low toxic risk in all seasons according to TRI and as posing very high ecological risk in all seasons according to mPER. No risk was indicated in terms of HI and LCR. In all seasons, in terms of EF it was determined there was extremely high enrichment for Se, moderate enrichment for Cr and Mn and significant enrichment for Cu, Ni, Pb and Zn, according to the mER there was low potential risk for Cr, Mn and Zn, moderate for Cu and high for Cd, according to Igeo there was no Cr, Cu, Fe, Mn, Mo, Ni, Pb and Zn pollution, moderate Cd contamination and moderately to heavily polluted for Se, according to SQG Cd, Cu and Ni exceeded the LEL, MET and TET values. The levels of heavy metal accumulation were observed as root>leaf>stem in M. spicatum and leaf>stem in C. demersum, and that the most accumulated metal in both plants was Fe and the least accumulated metal was Cd, these could be used for phytoremediation purposes. In the second period of the study, water and macrophyte samples were collected from two stations determined in Kovada Channel and four stations determined in Kovada Lake. Temperature (°C), pH, electrical conductivity (µS/cm), dissolved oxygen (mg/L), oxygen saturation (%), biochemical oxygen demand (BOD₅), ammonium nitrogen (NH₄-N), nitrate nitrogen (NO₃-N), nitrite nitrogen (NO₂-N), orthophosphate (PO₄-P), sulfate ion (SO₄-2), total phosphorus (P), carbonate (CO₃), bicarbonate (HCO₃⁻), chloride ion (Cl⁻), calcium (Ca), magnesium (Mg), total dissolved solids (TDS), suspended solids (SS), total water hardness (°f), and turbidity (NTU) were analyzed in water samples. While determining the water quality of the stations according to physicochemical parameters, the Surface Water Quality Regulation (SWQR) and the Water Pollution Control Regulation (WPCR) were utilized. Besides, the physicochemical parameters were compared with the drinking water standards for human consumption established by the WHO, EPA, EU, and TS 266 quality criteria and the water quality index (WQI) was determined using some physicochemical parameters. To determine water quality according to macrophyte samples, the biological macrophyte index for rivers (IBMR) and the mean trophic rank (MTR) were applied at stations 1. and 2., macrophyte index (MI) was employed at stations 3., 4., 5. and 6. Pearson correlation analysis and PCA were performed to determine the relationship between macrophyte species and physicochemical parameters. Dominance, similarity and diversity analyses were applied to the macrophyte samples. According to SWQR the water of the study area is in the I. quality class in terms of nitrate nitrogen, I. and II. in terms of electrical conductivity and biological oxygen demand, I. and III. in terms of ammonium nitrogen and total phosphorus, I., II. and III. in terms of medium phosphate and dissolved oxygen. According to the WPCR, the water was classified as class I, II, and III in terms of temperature and oxygen saturation; class I, II, and IV in terms of pH; class I and IV in terms of nitrite nitrogen; and class I in terms of sulfate, chloride, and total dissolved solids. It was determined that, at some stations, the values of pH, ammonium nitrogen, nitrite nitrogen, and turbidity exceeded the WHO, EPA, EU, and TS 266 drinking water standards. According to the WQI values, Kovada Lake was classified in the excellent water while Kovada Channel was placed in the poor water category. As a result of the study, a total of 62 macrophyte taxa belonging to 48 genera and 32 families were identified. The most dominant species was Myriophyllum spicatum, followed by Phragmites australis, Ceratophyllum demersum, Myriophyllum verticillatum, and Potamogeton panormitanus, respectively. Kovada Channel was determined in the poor quality class according to IBMR, in the 2b quality class according to the MTR, its trophic status was at the eutrophic level. Kovada lake was classified polluted water quality class according to MI. The highest similarity was revealed between stations 4 and 6 with 73%, whereas the lowest similarity between stations 1 and 4 with 49% according to Sorensen similarity analysis. In the diversity assessment, the Shannon-Wiener index was calculated between 3.30 and 3.88. Kovada Lake is currently at risk of disappearing. Necessary measures should be taken to reduce pollution pressure on the lake, maintain its sustainability, and increase its water volume.