Dry-season sources of riverine sediment from the tropical mixed urban-agricultural watershed of the Mun River Basin in northeastern Thailand |
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Institution: | 1. Environmental Engineering and Disaster Management Program, School of Interdisciplinary Studies, Mahidol University Kanchanaburi Campus, Kanchanaburi 71150, Thailand;2. Earth Science Research Center, Mahidol University Kanchanaburi Campus, Kanchanaburi 71150, Thailand;3. Faculty of Environment and Resource Studies, Mahasarakham University, Mahasarakham 44150, Thailand;4. State Key Laboratory of Resources and Environmental Information System, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China |
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Abstract: | Northeastern (NE) Thailand is well recognized as the land for rice cropping and consequently, it is potentially contaminated with chemicals from soil fertilization, pest/weed control, and urban discharges. The Mun River basin in NE Thailand principally is comprised of rice paddies and sedimentation in the river has been pronounced, but the studies on sediment source identification are limited. The current study aims to identify sediment sources in the Mun River basin and discuss possible impacts on ecosystems attributed to exposure to polluted sediment. The assessment relies upon physicochemical properties and heavy metal contents (iron (Fe), manganese (Mn), copper (Cu), chromium (Cr), nickel (Ni), and Zinc (Zn)) in the fine-grained sediment (<63 μm) taken from the Mun River basin and the Chi River in the dry season of 2020–2021. The findings revealed that the heavy metals in the sediment had not accumulated to levels of concern. Most sediment was from natural sources, including Fe- and Mn-rich sediment, Cr-dominant sediment, and Ni- and Cu-rich sediment. Fe- and Zn-rich sediment was, however, found in the urban watershed of Lam Ta Klong, and it could originate from mixed urban sources. Fe-rich sediment was predominant in the Mun River basin, which and could be a significant sink and source of toxic elements from agricultural and urban discharges. It is suggested that the toxic compounds in the sediment should be consistently monitored, whereas ecological and health risk assessment should be focused on the mobile forms. |
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Keywords: | Sediment Heavy metals Mun River Lower Mekong River Agriculture |
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