The occurrence and distribution of persistent and emerging organic pollutants in Maltese coastal areas

Abstract

The presence of organic contaminants in the marine environment has been a focal point of interest to researchers as they pose a threat to aquatic organisms and human health. In the past, research has often focused on persistent organic pollutants (POPs). This includes legacy contaminants such as several organochlorine pesticides. These are known to be highly resistant to biodegradation and they tend to bio-accumulate in aquatic organisms. However, nowadays research has shifted to include the evaluation of emerging pollutants. This includes chemicals which are not being regulated, and although they may not be persistent by nature, they are constantly being released into the environment. It can be noted that data available on these types of pollutants in the Maltese islands is very limited. Hence, the aim of this study is to investigate the presence of POPs and emerging pollutants in Maltese coastal areas. During this study samples were collected from marine surface waters, during the months of June to August 2021, across the islands of Malta and Gozo. The contaminants present were then extracted using the solid phase extraction technique. A preliminary study, consisting of 10 sampling sites, was first carried out in order to identify the different types of organic pollutants present. This was performed using gas chromatography-mass spectrometry. From this investigation, different types of pollutants were identified including fuel derivatives, personal care products, pharmaceuticals, pesticides, plastic additives and flame retardants. Most of the contaminants were identified as being emerging pollutants rather than legacy contaminants, showing the relevance of these pollutants. For the latter part of this study, a group of emerging pollutants known as phthalate acid esters were investigated across 28 sampling sites. These were quantified using ultraperformance liquid chromatography mass spectrometry. Dibutyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP) were investigated as these are some of the most common plasticisers used in various plastic products. In fact, both of these contaminants were found in 96% of the locations sampled with concentrations ranging from <LOD -122.85 ngL-1 (LOD = 5.60 ngL-1) for DBP and <LOD - 98.99 ngL-1 (LOD = 5.42 ngL-1) for DEHP. Differences between Malta and Gozo, and location types, such as beaches and harbours were also investigated, however statistical analysis showed no significant difference for concentrations of DBP and DEHP. Still, this study helped to bridge the gap in determining the distribution and contaminant levels of phthalates in Malta. Such studies are essential in order to understand the fate of pollutants in our environment.