Laboratory and field studies on the use of artificial mussels as a monitoring tool of platinum exposure in the freshwater environment

Abstract

Abstract Background The artificial mussel (AM) is a passive sampling device that was originally developed for monitoring metal concentrations in the marine environment, but is also increasingly used in freshwater environments. The AM consists of a non-permeable Perspex tube, which is closed on both sides with a semi-permeable membrane. The space in between contains Chelex-100 beads, which bind metals. The AM allows the determination of the dissolved, bioaccessible metal fraction in water bodies without killing organisms, as well as environments with unfavorable conditions for living bioindicators. In the present study, the use of the AM was adapted for the monitoring of platinum (Pt) in a freshwater ecosystem. Results The elution of Pt from the Chelex-100 beads was optimized. Two modifications to the original method for the use of AMs are recommended, i.e., washing and separation of the beads through centrifugation and elution with a mixture of 4.5 mL HNO3 and 0.5 mL HCl for approximately 2–3 h to ensure the release of all Pt bound to the beads. Additionally, the uptake kinetics of the AM were determined under laboratory conditions over a wide exposure concentration range (0.1–1000 µg/L) showing highly correlated Pt accumulation in the AMs with the aqueous exposure concentration. For the tested Pt exposure concentrations of 0.1, 1, 10, and 100 µg/L, the Pt concentrations in the AMs increased during the exposure period of 6 weeks. At the highest exposure concentration of 1000 µg/L, the increase stagnated after 3 weeks. To validate the AM in the field, the Pt accumulation of the AM was assessed together with that of freshwater clams (Corbicula fluminalis africana), muscle and liver tissue of the three fish species sharptooth catfish (Clarias gariepinus), common carp (Cyprinus carpio) and Mozambique tilapia (Oreochromis mossambicus), as well as water hyacinths (Eichhornia crassipes) at two sampling sites in the Pt mining area of South Africa. Conclusion Results from the present study showed that the AM is a promising tool to monitor Pt concentrations in the freshwater environment at contaminated sites.