Quantifying Bioavailability of Pyrene Associated with Dissolved Organic Matter of Various Molecular Weights to Daphnia magna

Abstract

Dissolved organic matter (DOM) is a key environmental factor for the bioavailability of hydrophobic organic compounds (HOCs) in natural waters. However, the bioavailability of DOM-associated HOCs is not clear. In this research, pyrene was selected as a model HOC, and its freely dissolved concentration (C) was maintained by passive dosing systems. The immobilization and pyrene content in the tissues excluding gut of Daphnia magna were examined to quantify the bioavailability of DOM-associated pyrene. The results indicated that DOM promoted the bioavailability of pyrene when the C of pyrene was kept constant, and the bioavailability of pyrene associated with DOM of various molecular weights was ordered as middle molecular weight (5 000-10 000 Da) DOM > lower molecular weight (<1 000, 1 000-3 000, and 3 000-5 000 Da) DOM > higher molecular weight (>10 000 Da) DOM. The influencing mechanisms of DOM molecular weight were related with the partition of pyrene between DOM and water, the uptake routes of DOM by D. magna, and the desorption or release of pyrene from DOM in the gut of D. magna. The findings obtained in this research suggest that the bioavailability of DOM-associated HOCs should be taken into account for the eco-environmental risk assessment of HOCs in water systems.

Levels of Polycyclic Aromatic Hydrocarbons in the Water and Sediment of Buffalo River Estuary, South Africa and Their Health Risk Assessment

“…Their hydrophobicity has generated a lot of concerns amongst the general public because of the accompanying risks to humans, environment, and aquatic organisms. They associate freely with dissolved organic matter in the natural water through several means of binding and adsorption, especially those with high molecular weights (Akkanen et al 2005 ; Zheng et al 2007 ; Smith et al 2011 ; Yu et al 2011 ; Lin et al 2018 ) and are subsequently deposited in the sediment, thus accumulating to a higher level of toxicity in the aquatic environment (Prabhukumar and Pagilla 2010 ; Brazkova and Krastanov 2013 ; Olatunji et al 2014 ). The bioavailability of PAHs to the aquatic animals and also their penetration of dietary sources has thus become unavoidable (Sakuma et al 2011 ; Adeniji et al 2018b ).…”

Investigation of Daphnia magna Sub-Lethal Exposure to Organophosphate Esters in the Presence of Dissolved Organic Matter Using 1H NMR-Based Metabolomics

“…Therefore, it should also be considered that DOM may have reduced the freely dissolved concentration of TPhP to an extent where a different metabolic response was seen with TPhP and DOM exposure compared to TPhP only exposure [ 8 ]. DOM may have enhanced the bioavailability of TPhP to D. magna [ 11 ]. A previous study conducted over 48 h with pyrene (60 µg/L) in the presence of 30 mg DOC/L found that the bioaccumulation of pyrene in D. magna increased by 42–92% compared to controls without DOM [ 11 ].…”

“…DOM may have enhanced the bioavailability of TPhP to D. magna [ 11 ]. A previous study conducted over 48 h with pyrene (60 µg/L) in the presence of 30 mg DOC/L found that the bioaccumulation of pyrene in D. magna increased by 42–92% compared to controls without DOM [ 11 ]. In addition, it was reported that DOM can enhance the water solubility of some hydrophobic organic contaminants likely due to a partitioning interaction with DOM, which may contribute to the increased uptake of organic contaminants in aquatic organisms [ 11 , 39 ].…”

“…A previous study conducted over 48 h with pyrene (60 µg/L) in the presence of 30 mg DOC/L found that the bioaccumulation of pyrene in D. magna increased by 42–92% compared to controls without DOM [ 11 ]. In addition, it was reported that DOM can enhance the water solubility of some hydrophobic organic contaminants likely due to a partitioning interaction with DOM, which may contribute to the increased uptake of organic contaminants in aquatic organisms [ 11 , 39 ]. Therefore, the freely dissolved concentration of TPhP may not be the only bioavailable form and DOM may have enhanced the bioavailability of TPhP to D. magna which contributed to the unique metabolic response observed.…”

“…For instance, the bioaccumulation of benzo[k]fluoranthene and the activity of the biomarker for chemical exposure 7-ethoxysorufin-o-deethylase (EROD) in medaka decreased with an increase in DOM concentration [ 6 ]. In contrast, DOM was found to increase the bioavailability of organic contaminants such as pyrene and perfluoroalkyl substances to freshwater crustaceans [ 11 , 12 ]. Therefore, DOM may not always reduce the toxicity of organic contaminants and molecular-level mechanisms should be investigated to obtain a better understanding of how DOM may alter the toxicity of organic contaminants.…”