Interaction of mercury with beached plastics with special attention to zonation, degradation status and polymer type

Abstract

To study the interaction of mercury (Hg) with plastics in coastal marine environments, a total of 353 plastic items were collected from 4 beaches located on the Spanish Mediterranean coast, with different characteristics. Concentrations ranged from 5 to 8216 nmol kg⁻¹ and were greater on beaches more influenced by the mining activity. A preference of Hg for polymers such as polyurethane (PUR) and poly(vinyl chloride) (PVC), and for certain colours such as black, red and brown was observed. The state of degradation proved crucial, as Hg levels increased with the aging of the plastic. Although new commercial plastic items already contain Hg associated with their manufacturing process, they are able to adsorb even more once in the marine environment, by being in contact with larger quantities of this element in the ocean microlayer and acting as vectors of this element to the beaches. Once there, plastics are transported by winds and tides to the middle and high part of the beach, where the sunlight results in the volatilization of Hg to the atmosphere, decreasing the levels of this element in plastics.