Mangroves are areas that connect the land and sea, and are important to the ecosystem. They are important places for food sources and the habitat of aquatic fauna in the tidal areas. However, the existence of plastic debris poses a risk to the aquatic environment. This study aimed to investigate the accumulation of microplastics (MPs) in sediment cores from two mangrove areas. The first mangrove area is in the outer section of the Songkhla lagoon (SK), while the second is in the coastal area of Pattani province (PN). Sediment core sampling was performed from SK = 8 stations and PN = 5 stations. Surface enrichment of MP was observed, especially in sediments of 0–4 cm. MPs were found throughout the depth in both areas, while fewer MPs were found in deeper sediment core layers (p < 0.05) at some stations inside the mangrove zone. Simple linear regression of the observed MPs and distance in the horizontal were found to be significant at SK within the mangrove zone with r2 = 0.79 (p < 0.05). MP fibers were the most commonly found MP type in both areas and were less than 1 mm. Blue and black MPs were the most abundant colors found in both areas. The six polymer types reported in this study comprised polyethylene, rayon, rubber, styrene, Poly (vinyl acetate), and paint. The findings of the present study suggest that long-term monitoring of marine debris along coastlines is necessary to help improve national policies and measures related to marine plastic debris.
The concentration and distribution of trace metals were determined in sediment cores from the Khuan Khi Sian wetland, Thailand. The sediment cores were collected from seven stations in the dry and wet seasons in 2022. The concentration of Pb, As, and Cd in the dry season were in the range 0.00–60.16, 0.00–6.68, and 0.00–0.92 mg/kg (dry weight), respectively. Meanwhile, the concentration of Pb, As, and Cd in the wet season were in the range 0.00–12.12, 0.00–3.86, and 0.00–0.92 mg/kg (dry weight), respectively. The vertical profiles of metal concentrations in core sediment show a general increase from bottom to top. Average concentrations of heavy metals in the sediments of the Khuan Khi Sian wetland are found to be lower than the sediment quality guideline. In the sediment cores, only As in the dry season exceeded the U.S. EPA standard. The calculated enrichment factor (EF) and the geoaccumulation index (Igeo) indicate that the sediments were moderately polluted with As in some locations. According to the Ri analysis, Pb was low risk but the criteria of ecological risk of As and Cd are considerable and they are considered high risk. This is potentially due to agricultural activities and land use around the wetland areas and municipalities. The concentration of As and Cd should be of concern and subject to regular monitoring.
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