The aim of this doctoral thesis is to use laboratory experiments and computer modeling to test our hypothesis that plastic is a source of potentially hazardous chemical contaminants. Throughout this doctorial study we will characterize mixtures of organic chemicals that are released from aging plastics and assess the resulting hazards. The field work, laboratory experiments and computer modeling required to test our hypothesis will be divided into four research activities.

The first activity is to collect microplastic particles from the Baltic Sea to characterize the level and composition of plastic, and to provide material for experiments in the subsequent activities. Sampling will be conducted using a research vessel equipped with a trawling net. During our sampling we will use to trawling nets with different mesh sizes. We will take samples close to the mainland beginning from Askö as our starting point. During the ship ride we will try to collect samples that are more influenced by bigger cities. This will be conducted by driving to Södertälje. Plastic debris collected from the surface will be isolated by oxidizing marine carbon with hydrogen peroxide. After oxidation inorganic solids will be separated from the plastic by density gradient centrifugation. In order to assess the quantity of micro plastic mass in the original sample it will be weighed. If necessary the plastics will be separated by physical sorting using tweezers and a microscope. To the extent possible, the plastic debris will be identified according to polymer type using infrared spectroscopy. Later on we will age the collected plastic under laboratory con ditions mimicking many years of weathering in the environment.

Project members

Berit Gewert (PhD-student) and Matthew McLeod (supervisor), Berit.Gewert@aces.su.se