Environmental assessment of ester-based lubricants after application

Area of Science:

• Environmental Science
• Ecotoxicology
• Tribology

Background:

• Renewable-resource-based lubricants offer environmental benefits over petrochemicals.
• Additives are typically required to enhance lubricant performance, but research aims to eliminate them.
• Understanding the environmental fate of lubricants, including metal uptake during application, is crucial for ecological assessment.

Purpose of the Study:

• To determine the extractability and bioavailability of metals accumulated in lubricants during use.
• To assess the contribution of these metals to the overall ecotoxicity of lubricant eluates.
• To investigate metal interactions and their combined toxic effects using established models.

Main Methods:

• Simulated lubricant application on a tribological test bench.
• Preparation of water-soluble fractions (WSF) and serial dilutions.
• Chemical analysis for metal content and total organic carbon (TOC).
• Bioassays (algal growth inhibition, luminescence inhibition, daphnid immobilization).
• Calculation of toxic units (TU) and mixture toxicity (concentration addition, independent action).

Main Results:

• Metals, particularly copper, zinc, nickel, and chromium, were found to be extractable from used lubricants.
• The extractable fraction of metals increased with lubricant usage time.
• Bioassays confirmed metal bioavailability and indicated varying degrees of toxicity, with copper showing significant effects.
• Luminescence inhibition assays proved most sensitive; mixture toxicity calculations showed good correlation with observed effects.

Conclusions:

• Metals accumulated during lubricant application are bioavailable in aqueous environments, influencing ecotoxicity.
• The bioavailability and toxic impact vary among different metals and test organisms.
• While metals contribute to toxicity, the organic oil matrix may also play a role, necessitating further investigation.