Exploring the State of Heavy Metal Pollution the sediment, flora and fauna of Hong Kong's mangroves

Abstract

The mangroves of Hong Kong cover ~350 hectares and are exposed to multiple and intense anthropogenic stressors related to urban development. One of the major threats faced by Hong Kong mangroves is heavy metal pollution introduced via industrial activities. Mangroves are particularly vulnerable to heavy metal pollution as their fine-grained sediments and levels of organic matter result in a high binding affinity for contaminants. The extent and concentration of heavy metals in marine sediments are known to vary across the Hong Kong coastline thanks to the monitoring of marine sediment quality by the Environmental Protection Department (EPD). However, there is limited knowledge concerning the concentration of metals in Hong Kong mangroves specifically and current literature fails to consider the accumulation of metals in mangrove fauna including crabs, which are vital to the health and resilience of mangroves by performing key ecological roles (e.g. soil aeration through burrowing and feeding behaviour). To understand the extent of heavy metal pollution in Hong Kong mangroves and gain insight to their bioavailability, we assessed the concentration of Al, As, Cd, Cr, Cu, Fe, Mg, Mn, Ni, Pn and Zn in sediment, plant and crab species in four Hong Kong mangroves using Induction Coupled Plasma Mass Spectrometry (ICP-MS) for the first time in Hong Kong.