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Possible impact of dam reservoirs and river diversions on material fluxes to the Gulf of Thailand 总被引：1，自引：0，他引：1
Manuwadi Hungspreugs Wilaiwan Utoomprurkporn Penjai Sompongchaiyakul Watanee Heungraksa 《Marine Chemistry》2002,79(3-4)
Thai people have always been agricultural-based, although rainwater is not enough to sustain year-round agricultural practice. The first earth-filled dam was built across a valley near Sukhothai over 700 years ago. Now, there are six major multipurposed dam reservoirs, among which the largest is the Sri Nakarind (SN) built across the Kwae Yai River, the main branch of the Mae Klong River in the western part of Thailand. The first multipurposed dam reservoir built on the Chao Phraya (largest) River System is the Bhumibhol Dam on the Ping River. In this paper, the two Mae Klong River Dam Reservoirs and their biology and chemistry are discussed. Also investigated are the historical records of material fluxes to the Gulf of Thailand in down-core sediment profiles and in 40-year bands of coral, Porites lutea, taken from the Upper Gulf of Thailand near Si Chang Island. Sediment cores studied did not show clear decreases in the biogenic silica concentration in the Upper Gulf area after the building of dams. Part of the reasons might be the higher rate of dissolution of silica in tropical waters bioturbation of surface layers or the constant disturbance of the bottom sediment by fishermen using bottom trawls. The record in the coral bands seems to be more promising in reflecting the material flux change due to dam construction. An attempt to detect changes in diatom population with time due to the expected decrease in siliceous material discharge was not possible because there was a change from the use of 70 μm mesh size to 20 μm mesh size resulting in the increase of species and biomass, although the diatom percentage remained above 80% in all estuarine samples. 相似文献
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海洋碎屑沉积物的粒度特征是海底沉积动力环境的直接体现,是用来研究海洋动力环境变化的重要手段,尤其是陆架海底表层沉积物的粒度分布,对于研究沿岸和水柱底边界层现今海洋动力环境可起到重要作用。该项研究通过调查遍布泰国湾至湄公河口海底表层沉积物陆源碎屑的粒度分布特征,以期获得影响现今特定海域沉积作用的海洋动力环境过程。粒度分析的结果显示,泰国湾表层沉积物的陆源碎屑以细砂-细粉砂为主,分选总体较差,频率分布以正偏为主。其中,细砂-极细砂组分主要分布在曼谷湾和柬埔寨沿岸。湄公河岸外沉积物为细砂,且分选比泰国湾区域的沉积物要好。这些表层沉积物的粒度特征具有良好的环境变化指示作用。湄公河岸外分选较好、近于正态分布的中砂沉积物指示了波浪作用下的沉积环境。曼谷湾和柬埔寨沿岸分选较差的中砂-细砂粗粒沉积物反映了潮汐和波浪的共同作用;泰国湾东西沿岸区域分选中等、呈正偏态的极细砂-中粉砂沉积物体现了潮汐的控制作用;而泰国湾中部分选较差的沉积物则指示了表层洋流作用。研究表明,泰国湾和湄公河岸外表层沉积物陆源碎屑的粒度分布特征可用于区分不同海洋动力因素的控制作用,揭示出泰国湾的沉积动力环境主要受潮汐、波浪和洋流的共同影响,湄公河岸外的沉积动力环境主要受波浪的影响。 相似文献
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The U-Tapao Canal is the main source of freshwater draining into the outer part of Songkhla Lake, which is the most important estuarine lagoon in Thailand. Songkhla Lake is located in southern Thailand between latitudes 7°08' and 7°50' N and longitudes 100°07' and 100°37' E. Acetic acid (HOAc)-soluble Cu, Fe, Mn, Pb, and Zn and the total concentration of these metals along with Al concentration, organic carbon, carbonate, sand, silt, and clay contents were determined in 4 sediment cores obtained at selected intervals from the mouth of the canal to 12 km upstream. Readily oxidizable organic matter in the cores varies from 1.52% to 7.30% and is generally found to decrease seaward. Total concentrations of Al (61.7–99.0 g kg−1; 2.29–3.67 mol kg−1), Cu (12.4–28.2 mg kg−1; 195–444 μmol kg−1), Fe (25.2–42.0 g kg−1; 451–752 mmol kg−1), Mn (0.22–0.49 g kg−1; 4.0–8.9 mmol kg−1), Pb (16.7–43.1 mg kg−1; 80.6–208 μmol kg−1), and Zn (48.6–122.7 mg kg−1; 0.74–1.88 mmol kg−1) vary to a certain extent vertically and seaward in the U-Tapao Canal core sediments. These concentrations are at or near natural levels and show no indication of anthropogenic contamination.Overall, the data show that total metal concentrations in the surface and near surface core sediments are enriched in varying degrees relative to Al in the order of Zn>Mn>Pb>Fe>Cu. Chemical partitioning shows that the enrichment in the surface and near surface sediments is related to the relatively high proportion of the total metal concentrations (Mn>Zn>Fe>Cu>Pb) that occur in the acetic acid-soluble (nondetrital) fraction, and they generally decrease with depth. Nondetrital Cu, Pb, and Zn likely derive from those metals held in ion exchange positions, certain carbonates, and from easily soluble amorphous compounds of Mn and perhaps those of Fe. Diagenetic processes involving Mn and to a lesser extent, Fe compounds, as well as the vertical changes in the oxidizing/reducing boundaries, appear to be the most important factors controlling the behavior of the metals in these cores. Organic matter and the aluminosilicate minerals, however, appear to be less important carriers of the metals studied. 相似文献
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