A comprehensive ecological risk assessment of an accidental spill of palm stearin on the subtropical marine environment

Abstract

On 3 August 2017, two container vessels collided in the Pearl River Estuary leading to release over 1,000 tonnes of palm stearin into adjacent waters. This study aimed to assess its ecological risk to marine ecosystems in subtropical Hong Kong. Samples of surface seawater, sediment and three intertidal gastropods in six locations were collected seven days and four months after the incident, subject to GC-MS analysis. Standard toxicity tests were conducted with five marine species. The results showed that seawater and sediment samples were heavily contaminated by the palm stearin after one week of the incident, and their levels significantly decreased after four months. However, levels of fatty acids in the animals generally increased over the same period. Although the palm stearin had relatively little effects on marine animals, it was toxic to microalgae species as reflected by growth inhibition. An interim criterion maximum concentration (CMC) for the palm stearin was determined as 0.389 mg/L. Overall, the palm stearin only posed a short-term risk.