بررسي توزيع و تنوع ميكروپلاستيك‌ها در محيط دريا و ارزيابي ريسك زيست‌محيطي (مطالعه موردي: خور موسي)

Study on the distribution an‎d diversity of microplastics in the sea an‎d assessing their environmental risk (Case study: Musa Estuary)

مهندسي عمران

Microplastics are plastic particles smaller than 5 mm that are recognized as emerging environmental pollutants. Due to their high persistence, small size, an‎d capacity to adsorb an‎d transport chemical contaminants, microplastics can exert detrimental effects on aquatic ecosystems an‎d pose environmental an‎d human health risks through their incorporation into food webs. Estuaries, as semi-enclosed coastal ecosystems, are particularly prone to the accumulation of these pollutants because of limited water exchange with the open seas an‎d their proximity to industrial an‎d urban activities. The Musa Estuary, located in the northwestern Persian Gulf, is considered one of the sensitive areas with respect to microplastic pollution due to the presence of a petrochemical special economic zone an‎d the direct discharge of industrial effluents. The present study aimed to investigate the abundance, distribution, an‎d diversity of microplastics in industrial effluents as well as in the water an‎d sediment matrices of the Musa Estuary an‎d to assess the associated environmental risk. To this end, during a single sampling campaign, a total of 36 samples were collected from water, sediment, an‎d industrial effluents. Overall, 11 water samples an‎d 10 sediment samples were collected from the Musa Estuary, along with 15 industrial effluent samples from petrochemical discharge outlets. Microplastic particles were extracted in the laboratory using physical an‎d chemical separation methods an‎d subsequently identified in terms of size, shape, an‎d polymer type. Data analysis was conducted using statistical tests, an‎d the preliminary environmental risk of microplastics was eva‎luated using the PHI index. The results indicate that the Musa Estuary is contaminated with microplastics in both water an‎d sediment matrices. The mean abundance of microplastics was 540.4 particles L⁻¹ in water, 19,720 particles kg⁻¹ dry weight in sediments, an‎d 441.8 particles L⁻¹ in industrial effluents. The highest microplastic abundance in the water column was observed at stations adjacent to industrial effluent discharge outlets, highlighting the dominant role of industrial activities in the direct input of microplastics into the Musa Estuary. In sediments, the highest values were recorded at an‎d near the outlets of the Jafari an‎d Zangi creeks an‎d in the southern areas of the estuary, whereas lower abundances were observed at the reference station an‎d at sites characterized by unstable hydrodynamic conditions. Across all three matrices, water, sediment, an‎d industrial effluents, the majority of microplastic particles were within the size range of 100–500 μm, indicating the progressive fragmentation of larger plastic debris an‎d the persistence of this size fraction during environmental transport an‎d accumulation processes. In terms of morphology, fibers an‎d fragments were identified as the dominant shapes in water an‎d effluent samples, while fragments constituted a larger proportion in sediments. The dominant identified polymers included polyethylene (PE), polypropylene (PP), an‎d polyethylene terephthalate (PET). Environmental risk assessment results revealed that the Musa Estuary falls within the high-risk category in both water an‎d sediment matrices, posing a potential threat to aquatic organisms an‎d the ecological sustainability of the region. Overall, the findings demonstrate the widespread occurrence of microplastic pollution in the Musa Estuary an‎d emphasize the necessity for continuous monitoring an‎d effective control of industrial effluents to reduce the input of these emerging pollutants into coastal environments.

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