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Occurrence of microplastics in Russell’s snapper (Lutjanus russellii) and associated prey species in the Central Gulf of Thailand
(2025-02-01)
Klangnurak, Wanlada
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Prachumwong, Siriluk
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Alfonso, María Belén
;
Nakano, Haruka
;
Chavanich, Suchana
Microplastic (MP) contamination in fish may occur via their feeding behavior and ingestion of contaminated prey. This study investigated the presence of MPs in the predator Lutjanus russellii (Russell’s snapper) and its prey along the Chumphon coast of the Central Gulf of Thailand. Stomach contents of L. russellii were analyzed to identify its prey species. Prey species were then sampled from the same geographical area as the predator specimens for subsequent MP analysis. The dietary habits of L. russellii classify it as a generalist carnivore, consuming a diverse range of food items, including zooplankton, crustaceans, and small fish. No significant correlation was observed between MP abundance and the weight or length of the predator fish (general linear model, p > 0.05). Black and red fibers were the predominant MP types in both predator and prey, though MP sizes varied among the sampled species. In predator stomachs, the most common polymers were acrylonitrile butadiene styrene (ABS; 26.32%), polyethylene terephthalate (PET; 21.05%), and polyester (PES; 10.53%). Conversely, prey samples were dominated by PES (17.58%), PET (15.38%), and ABS (13.19%). Notably, similarities in MP characteristics (shape, color, average size, and certain polymer types) were observed between L. russellii and Portunus sp. The detection of smaller PET fibers in L. russellii compared to Portunus sp. (Mann–Whitney U-test, p ≤ 0.05) suggests the transfer of MPs to L. russellii through the ingestion of hard-shelled crustacean prey. This study underscores the importance of examining predator–prey interactions to better understand MP contamination pathways in marine ecosystems, particularly in regions like the Gulf of Thailand, where plastic pollution is prevalent. Further research is required to assess the long-term ecological implications of MP transfer within marine food chains.
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Organochlorine pesticide residues persist throughout the sugar production process
(2024-01-01)
Janjamroon, Wilailak
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Sriprom, Pongsert
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Kaewlaoyoong, Acharee
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Cheruiyot, Nicholas Kiprotich
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Permana, Lasuardi
Thailand, one of the world's largest sugarcane producers, has historically used organochlorine pesticides (OCPs) extensively in its plantations. Therefore, OCP residues are anticipated in plantation soil. However, the persistence of these compounds during sugar production is ambiguous. Thus, this study investigated the OCP residues in sugarcane at the different processing stages. Five product samples, i.e., sugarcane juice, bagasse, raw sugar, granulated white sugar, and molasses were obtained from different regions in Thailand. High concentrations of p,p′-dichlorodiphenyltrichloroethane (p,p′-DDT), γ-hexachlorocyclohexane (γ-HCH or lindane), and cyclodiene derivatives such as aldrin, dieldrin, heptachlor and its epoxide were found in the samples. This is surprising because the OCP use in sugarcane plantations has been long banned in Thailand. Bagasse and raw sugar had the highest total OCP concentrations of 1.0393 ± 0.7555 mg/kg and 0.9658 ± 0.8209 mg/kg, followed by white sugar (0.1616 ± 0.1311 mg/kg), molasses (0.0813 ± 0.1195 mg/kg), and sugarcane juice (0.0173 ± 0.0112 mg/kg). This study offers comprehensive information on the fate of OCPs during the entire sugarcane processing stage, from the cane to the final granulated sugar. The findings also suggest persistent OCP presence in plantation soil, possibly due to illegal use.
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A two-dimensional mathematical model for long-term contaminated groundwater pollution measurement around a land fill
(2020-01-01)
Limthanakul, Jirapud
;
Pochai, Nopparat
A source of contaminated groundwater is governed by the disposal of waste material on a land fill. There are many people in rural areas where the primary source of drinking water is well water. This well water may be contaminated with groundwater from landfills. In this research, a two-dimensional mathematical model for long-term contaminated groundwater pollution measurement around a land fill is proposed. The model is governed by a combination of two models. The first model is a transient two-dimensional groundwater flow model that provides the hydraulic head of the groundwater. The second model is a transient two-dimensional advection-diffusion equation that provides the groundwater pollutant concentration. The proposed explicit finite difference techniques are used to approximate the hydraulic head and the groundwater pollutant concentration. The simulations can be used to indicate when each simulated zone becomes a hazardous zone or a protection zone.
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Degradation of polyethylene terephthalate bottles after long sunlight exposure
(2019-01-01)
Chaisupakitsin, Malinee
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Chairat-Utai, Pitsamai
;
Jarusiripot, Chutima
Effects of sunlight on PET bottles degradation and liquid filled inside the bottles were studied. Three types of soft drinks filled in Polyethylene terephthalate (PET) bottles; drinking water in clear bottle, carbonated water in green, and pink bottles was left on the rooftop of building for 8 months. After long exposure to sunlight, the bottles’ shapes were not changed, but the tensile strength of plastics decreased. Moreover, the enthalpy of fusion which corresponds to molecular rearrangement of plastics increased. The results from FTIR showed slightly increased of peak hydroxyl group at 3,400 cm<sup>-1</sup> on outer surface of PET bottle. Sunlight slowly degraded the chemical structure on outer surface of PET bottle by photo-hydrolysis reaction. The pH of water for all samples changed from acid to base. By using Tollen’s reagent, aldehyde was found clearly in drinking water after sunlight exposure, but was not observed in green and pink water.
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Simulation of airflow in a cleanroom to solve contamination problem in an HDD production line
(2018-01-01)
Naosungnoen, Jiranan
;
Thongsri, Jatuporn
Contamination that exceeds the specification is one of many causes that contributed to a poor quality product in HDD cleanroom manufacturing process. The purpose of this research was to utilize CFD simulation to study the airflow in a clean room to find out the cause(s) of high contamination and to propose a remedy. The results of the simulation show that some areas in the production line had vortex flow and collected a large number of particles which were similar to the results of actual measurement in that clean room. A particular area, which was a long rectangular area near the middle of the clean room, stretching from one side of the room to the other, showed high particle concentration compared to other areas. To solve this problem, we closed one of the ULPA filters which was an inlet of that area. Subsequent simulation showed that there was less vortex flow and a significant reduction of particle concentration. Our method proved to be able to improve contamination control in a manufacturing clean room.
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A CFD investigation of airflow in a hard disk drive production line to detect the cause(s) of contamination and its mitigation
(2017-07-02)
Khaokom, Adisorn
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Thongsri, Jatuporn
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Kaewkhaw, Polsate
Contamination exceeds the standards in certain areas within the production line of hard disk drive (HDD) manufacturing, such as in the clean room of a factory. In order to find the cause(s) and solve the problem, we decided to use the computational fluid dynamics (CFD) to simulate the airflow within the production line. The results show the cause of contamination, which is from the exhaust fan installed in the electrical testing machine in the production line of HDD manufacturing, which releases large amounts of particles. To resolve this problem, the CFD results were analyzed to design and create a new cover for the exhaust fan. Once this invention is installed to the electrical testing machine, it can control the airflow to float into other areas that do not affect nor contaminate the product. The factory utilized this research. Other than solving contamination problems that exceed standards, it also saves production costs from purchasing new machines as well.

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