Assessing the Acute and Chronic Effects of Palladium on Daphnia magna and the Influence of Natural Organic Matter.

In recent decades, rising industrial demand for palladium (Pd), driven by its unique properties and affordability compared to other noble metals, has increased its environmental release into aquatic systems. This highlights the need to assess its effects on organisms, given the lack of standardized toxicity studies and regulations for this element. This study examines the acute and chronic impacts of Pd exposure on D. magna. Acute lethality was assessed over 48 h at measured Pd concentrations ranging from 2 to 110 μg/L, yielding an LC of 52 ± 2 μg/L and an LC of 33 ± 3 μg/L. The impact of natural organic matter from the Suwannee River on Pd lethality and bioaccumulation was also examined. No mortality occurred at DOC concentrations of 1, 2, 5, and 8 mg C/L, in contrast with the results obtained at 0.8 mg C/L, which resulted in an LC of 74 ± 1 μg/L. Pd bioaccumulation decreased significantly with increasing DOC concentrations compared to controls. After 15 days of chronic exposure, offspring viability significantly declined, with an EC of 1 ± 0.1 μg/L, alongside reductions in total broods per D. magna (EC: 7 ± 2 μg/L). Parental dry weight also decreased significantly, though the timing of the first brood and weight-normalized oxygen consumption rates remained unaffected across treatments. Parental survival was notably affected, with an LC value of 14 ± 2 μg/L. These results emphasize Pd's potential for both lethal and sublethal effects, highlighting the need for environmental standards to protect aquatic life.