Ratchanee Puttapreecha’s research while affiliated with Phuket Marine Biological Center and other places

In February and March 2022, a large amount of pumice stone appeared along the shoreline of Thailand. Pumice is a type of extrusive volcanic rock, and since there are no volcanoes in the Gulf of Thailand, an interesting question was where the pumice stones originated from. Another question was whether the pumice could be a vehicle for microplastics (MPs) which could then journey across the ocean until reaching the coast of Thailand. A preliminary study was begun, which randomly collected samples from seven beaches in five provinces along the coast of Thailand. Grayish-green pumice stones are tiny, porous, and lightweight, ranging from 0.3 to 5.0 cm in size. The examination found 5.7–12.6 MP items per pumice stone. Most of the MP particles observed were less than 1 mm in length. From Fourier transform infrared spectroscopy (FTIR) analysis, the MPs were characterized as polystyrene, polypropylene, poly (ethylene terephthalate) (PET), rayon, and nylon. The MP could have entered the holes in pumice stones while floating on the water surface over long periods. From the seasonal flow patterns, it was revealed that pumice from the South China Sea was more likely to have floated with surface currents into the Gulf of Thailand

The 2021 eruption of Fukutoku-Oka-no-Ba (FOB) in the northwest Pacific on 13 August 2021 produced a large volume of pumice that drifted westward for ~1300 km to the Nansei Islands, Japan, and some extent. In February 2022, pumice with similar characteristics to the FOB pumice was deposited along the Gulf of Thailand. The pumice clasts deposited in Songkhla Province, Thailand, were fine-grained with <4 cm in size and rounded. Most of the clasts consisted of clinopyroxene, plagioclase (andesine), and olivine phenocrysts in a vesiculated grey groundmass, with black-coloured spots exhibiting signatures of a basaltic magma. The whole-rock compositions of the pumice are trachytic, with 61 mass% SiO2 and 9 mass% total alkali (Na2O + K2O). The overall characteristics in the pumice from Thailand are similar to those in FOB pumice. These pumice in Thailand were from the 2021 FOB eruption, and drifted >2800 km south-westward across the South China Sea.

The 2021 eruption of Fukutoku-Oka-no-Ba (FOB) in the northwest Pacific on 13 August 2021 produced a large volume of pumice that drifted westward for ~1300 km to the Nansei Islands, Japan. Some pumice clasts were transported farther southwest to Taiwan and the Philippines or northeast to the Kanto district of Japan by the Kuroshio current. In February 2022, pumice with similar characteristics to the FOB pumice was deposited along the east coast of the Malay Peninsula, along the Gulf of Thailand. The pumice clasts deposited in Songkhla Province, Thailand, were <4 cm in length and more rounded than to those collected in the Nansei Islands. Most of the clasts consisted of clinopyroxene, plagioclase (andesine) and olivine phenocrysts in a vesiculated grey groundmass, with black-coloured spots, some of which exhibited signatures of a basaltic magma, including anorthite-rich plagioclase with basaltic melt inclusions. The whole-rock compositions of the pumice are trachytic, with SiO2 contents of 61 mass% and total alkali contents (Na2O + K2O) of 9 mass%, similar to those collected in Japan. The minerals in the pumice from Thailand have similar compositions to those in FOB pumice. These pumice in Thailand were from the 2021 FOB eruption, and drifted >2800 km south-westward across the South China Sea, partly affected by the monsoon and corresponding seasonal ocean circulation. Pumice from large oceanic eruptions can spread across borders; therefore, an international pumice monitoring network might be required for future eruptions.