A first inventory of plastic litter and some associated total metal contents at the coastline of the Bay of Asunción (Paraguay)

Abstract

Global plastic production increased remarkably through the last decades. A drawback of this fact is that many tons of new and used plastics end up in waterways worldwide, where they can adsorb other pollutants, as heavy metals. This study is one of the very first dealing with both topics (plastic inventory and major associated metals) in South America. Its aim was twofold: to perform a first inventory of plastic litter at the Bay of Asunción (Paraguay), and to evaluate the quantity of specific metals in selected plastic items. Four sampling areas were established in a period when a serious drought was occurring, and litter was sorted as plastics, metals, rubber, ceramics/glass, natural materials, and miscellaneous. Further, plastic litter was classified by size, original use, type of polymer, and characterized by infrared spectrometry. Microwave-assisted digestion with HNO3 and flame atomic absorption spectrometry was applied to quantify Cd, Cu, Fe, Mn, and Zn. Highest percentages of litter (60 – 82%) corresponded to plastics at all points and their abundances were: PP, 42% > PE, 31% > PET, 12% > PS, 10% > PVC, 3% > PMMA, 2%. The highest total metal concentrations were for Fe (3526 μg g−1) and Mn (1163 μg g−1), followed by Zn (330.2 μg g−1), Cu (94.90 μg g−1), and Cd (18.70 μg g−1). Multivariate studies revealed that Fe and Mn became associated to PS whereas Cd was more related to PP.