Variations, health risks, pollution status and possible sources of dissolved toxic metal(loid)s in stagnant water bodies located in an intensive agricultural region of Turkey

There are many reservoirs, ponds and lakes in the Meric-Ergene River Basin (Turkey), which is an intensive agricultural region. Since agrochemicals are extensively applied to the agricultural soils in the basin, these water bodies may be contaminated with toxic metal (loid)s (TMs). However, no study has been conducted to determine TM levels in the water bodies. In this study, levels of seven TMs (Cr, As, Cu, N, Zn, Cd and Pb) in surface water samples taken from 25 different stagnant water bodies (11 reservoirs, 12 ponds and 2 lakes) in the dry and wet seasons were measured and compared with water quality guidelines. In addition, spatial and seasonal variations, health risks, pollution status and possible sources of TMs were assessed. The mean As concentration of the lakes was significantly higher due to drainage water from paddy fields. The ponds had higher total mean TM concentration likely due to their low water volume. Surface runoff from rainfall caused the Cr, Zn, Cd, Pb and Cu concentrations to increase in the wet season. Only the mean As concentration of the lakes in the dry season was above the drinking water standards. Metal pollution indices showed low contamination of the water bodies in both seasons. Health risk indices indicated that As in the lakes in the dry season via ingestion exposure pathway may pose both non-carcinogenic and carcinogenic health risks to the residents. The results of factor and correlation analyses showed that among the studied TMs, only As originated from anthropogenic sources. The findings of this study revealed that agricultural activities caused As pollution in the lakes, while the reservoirs and ponds were not significantly affected by agricultural activities. We suggest that the levels of TMs in all water bodies should be measured at regular intervals to check the quality of surface water.

Automated summary

The Meric-Ergene River Basin in Turkey, an intensive agricultural region, has various water bodies contaminated with toxic metals. The levels of seven TMs in surface water samples taken from 25 different stagnant water bodies were measured and compared with water quality guidelines, showing that As concentration in lakes was significantly higher. Factors such as seasonal variations and health risks were assessed, indicating that only the lakes in the dry season had As concentrations above drinking water standards, posing potential health risks to residents. The study highlighted the need for regular monitoring of TM levels in all water bodies to ensure surface water quality.