Initial assessment of the presence of plastic waste in some coastal mangrove forests in Vietnam

Abstract

Plastic, valued for its low cost and durability, is widely used in various aspects of daily life. However, accumulative plastic waste (PW) has emerged as an increasing environmental concern that causes a negative impact on both public well-being and marine biodiversity. Studies on marine PW have focused primarily on the number of PW items collected without considering its accumulation in coastal areas. Hence, this study aims to address this gap by meticulously examining the mass and constitution of macro PW in the summertime mangrove ecosystems of Hau Loc, Cat Ba, and Nha Trang. This study revealed that the average densities of PW collected in Hau Loc, Cat Ba, and Nha Trang mangrove forests were 0.93, 0.23, and 0.18 items·m-2 in the morning collection, whereas the afternoon collection showed slightly lower densities of 0.31, 0.12, and 0.14 items·m-2 for the same locations. Although all PWs in the standard plots were collected in the morning, PWs were present in the afternoon after the rising tide. This initially proves that tide is one of the reasons for increasing the presence of PW in mangroves. The most common types of PWs collected included water bottles, plastic bags, ropes, freight lines, fishing nets, and sponge floats. When assessing the PW composition based on mass, low-density polyethylene was the dominant PW category in Hau Loc with 5.97 g·m-2. In Cat Ba, polypropylene was the highest with 11.87 g·m-2, while polyethylene terephthalate was the highest with 0.9 g·m-2 in Nha Trang during the morning sampling. The "Others"type of PW was not present in any of the three locations. This study provides useful information that can be a foundation for future studies to analyze the relationship between socio-economic activities and the presence of PW in mangroves. Additionally, they hold the potential to guide the formulation of targeted strategies aimed at curbing plastic pollution within Vietnam's coastal regions.