Quantifying the bioavailability of pyrene sorbed on suspended sediments of various compositions and grain sizes to Daphnia magna

Suspended sediment (SPS) composition and grain size will affect the bioavailability of hydrophobic organic compounds (HOCs) associated with SPS in aquatic environments. However, no research has been carried out to quantify the... [ view full abstract ]

Suspended sediment (SPS) composition and grain size will affect the bioavailability of hydrophobic organic compounds (HOCs) associated with SPS in aquatic environments. However, no research has been carried out to quantify the bioavailable fraction of HOCs sorbed on SPS with different compositions and grain sizes. In this work, the passive dosing devices were made to control the freely dissolved concentration of pyrene, a typical HOC, in the exposure systems. The effect of pyrene associated with amorphous organic carbon (AOC), black carbon (BC), and minerals of SPS with grain sizes of 0-50 m and 50-100 m on the immobilization and enzymatic activities of D. magna was investigated to quantify the bioavailability of pyrene sorbed on SPS with different grain sizes and compositions. The results showed that the contribution of AOC-, BC-, and mineral-associated pyrene to the total bioavailability of SPS-associated pyrene was approximately 50%-60%, 10%-29%, and 20%-30%, respectively. The bioavailable fraction of pyrene sorbed on the three components of SPS was ordered as AOC (22.4%-67.3%) > minerals (20.1%-46.0%) > BC (9.11%-16.8%), and the bioavailable fraction sorbed on SPS of 50-100 m grain size was higher than those of 0-50 m grain size. This is because the SPS grain size will affect the ingestion of SPS and the SPS composition will affect the desorption of SPS-associated pyrene in D. magna. Based on this, a model has been developed to calculate the bioavailability of HOCs to aquatic organisms in natural waters considering both SPS grain size and composition.