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 水利部水质 监督检验测试中心 |
 院电力环境影响 评价与研究中心 |
《 Chinese Journal of Geochemistry 》 2006 Volume 25(Suppl.)
Early Diagenesis of Nurtrigents(C, N, P and Si) stored in sediments of two reservoirs in Southwestern China
Y. Wang 1 , J. Zhu 2 , and C.Liu 2
1. Dept. of Water Environment , China Institute of Water Resources and Hydropower Research , Beijing , 100038, People's Republic of China ;
2.State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry , Chinese Academy of Sciences, Guiyang , 55002, People's Republic of China
Abstract: Damming is a common anthropogenic intervention along the course of rivers, which is defined as “artificial-lake effect” (Humborg et al 1997), both in China and across the world. Today as many as 48,000 dams and /or reservoirs are in operation within the Changjiang River ( Yangze River ) drainage area, and more are being constructed. While damming is well known to affect riverborne nutrient loads, and thus the riverine ecosystems owing to removal of carbon fixation, and removal of particles in reservoirs sediments, there is limited information on the detailed early diagenesis of sediment in reservoirs including the regeneration processes of nutrients deposited in sediments and exchange flux across the sediment-water interface, which is important for mass balance of riverborne nutrients.
In the present study, two large-size reservoirs, Wujiangdu reservoir (WJDR) and Dongfeng reservoir (DFR), located on main steam of the Wujiang River and with uniformity hydrography and discrepancy biogeochemical activity (e. g. primary production), were selected for implementing a comparative study on the detailed processes of nutrients regeneration. Water, pore water and sediment were collected from these two reservoirs and dissolved organic carbon (DOC), NH 4 + , NO 3 - , PO 4 3- , dissolved silica (DSi) in the overlying water and pore water, and total organic matter in sediments were determined. The results of the correlation analysis suggested that in this two reservoir, processes of nutrients regeneration near the sediment-water interface were significantly different. As the result of rapid decomposition of algae-derived “labile” organic matters in upper sediments, nutrients regeneration processes and upward fluxes in WJDR are dramatically stronger than those of DFR. NH 4 + upward flux from sediment in WJDR was about 17 times higher than that in DFR. PO 4 3- flux in WJDR is about 13 times above that in DFR, DOC flux in WJDR is larger that in DFR by 5 times, and DSi by 1 time. These results implied that, retention nutrients in reservoirs might be partly compensated by nutrients regeneration near the sediment/water interface, and thus have significance for further investigation of the ‘artificial-lake effect' on riverine nutrients transportation, and on the tropic structure of aquatic ecosystems.
Key words: riverine nutrients, artificial-lake effect, nutrients regeneration, sediment-water interface, reservoir