"Evaluating the Ecotoxicological Impacts of Heavy Metals in Freshwater Ecosystems: A Comparative Study of Sediment Quality Guidelines."

This research investigates the evolution of sediment quality guidelines (SQGs) since the 1980s, highlighting a shift from basic comparisons of contaminant concentrations to more sophisticated assessments that account for ecological impacts. Historically, the reliance on background or reference values for sediment contamination assessments neglected the biological diversity and potential adverse effects on aquatic organisms. In response, various national and regional agencies have developed comprehensive SQGs aimed at safeguarding sediment-dwelling organisms within freshwater ecosystems. These guidelines are categorized into threshold effect concentrations (TECs) and probable effect concentrations (PECs). Utilizing statistical analyses performed with Statgraphics 19 and Microsoft Excel 2019, this study reveals notable variability in PECs, ranked as follows: chromium (Cr) at 11.00%, Nickel (Ni) at 30.04%, zinc (Zn) at 32.84%, copper (Cu) at 33.11%, lead (Pb) at 40.44%, cadmium (Cd) at 43.47%, arsenic (As) at 48.48%, and mercury (Hg) at 52%. These results indicate that chromium is the least variable contaminant, while mercury exhibits the highest variability. Additionally, the toxicity levels of various metals (loids) were investigated using box-and-whisker plots, revealing that mercury was the most toxic, whereas zinc was found to be the least toxic. For TECs, the ranking is lead (11.43%), mercury (16.67%), zinc (18.70%), nickel (20.00%), arsenic (25.79%), cadmium (29.58%), chromium (30.29%), and copper (37.14%), indicating lead as the least variable and copper as the most among the examined guidelines.