Is the Iron Gate I reservoir on the Danube River a sink for dissolved silica?
Is the Iron Gate I reservoir on the Danube River a sink for dissolved silica?
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DOI：
10.1023/b:biog.0000025738.67183.c0
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发表时间：
2004-03
期刊：
影响因子：
4
通讯作者：
G. Friedl;Christian Teodoru;Bernhard Wehrli
中科院分区：
文献类型：
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作者：
G. Friedl;Christian Teodoru;Bernhard Wehrli
拦河筑坝以许多直接和间接的方式改变了大坝下游的沉积物和养分循环。位于罗马尼亚边境的铁门I水库是多瑙河上最大的蓄水池，蓄水量为32亿立方米。在以前使用间接方法的研究中，假定硅以硅藻硅藻壳的形式保留在储层中高达600 kt年-1。这些溶解的硅酸盐没有被输送到黑海沿岸，可能导致那里的浮游植物群落发生变化，随后渔业急剧下降。我们直接量化了连续11个月进入和离开水库的溶解硅酸盐（DSi）的量。基于这些数据的预算揭示了两个重要事实：（1）只有约4%的DSi进入水库;（2）与区域和全球平均水平相比，水库上游河流中的DSi浓度相对较低。因此，在铁门处修建多瑙河大坝不可能导致蓄水下游记录的DSi浓度下降。相反，DSi的这种变化一定发生在多瑙河的源头。潜在的原因包括在铁门上游建造了许多水坝，水文变化导致地下水位降低，以及河床堵塞限制了地下水与河流的交换。
Damming rivers changes sediment and nutrient cycles downstream of a dam in many direct and indirect ways. The Iron Gates I reservoir on the Yugoslavian-Romanian border is the largest impoundment by volume on the Danube River holding 3.2 billion m3of water. Silica retention within the reservoir in the form of diatom frustules was postulated to be as high as 600 kt year−1in previous studies using indirect methods. This amount of dissolved silicate was not delivered to the coastal Black Sea, and presumably caused a shift in the phytoplankton community there, and subsequent drastic decline in fishery. We directly quantified the amount of dissolved silicate (DSi) entering and leaving the reservoir for 11 continuous months. The budget based on these data reveals two important facts: (1) only about 4% of incoming DSi was retained in the reservoir; (2) the DSi concentrations were relatively low in the rivers upstream of the reservoir compared to regional and global averages. Thus damming the Danube at the Iron Gates could not have caused the decline in DSi concentrations documented downstream of the impoundment. Rather, this change in DSi must have occurred in the headwaters of the Danube River. Potential reasons include the construction of many dams upstream of the Iron Gates, hydrologic changes resulting in lower groundwater levels, and clogging of the riverbed limiting groundwater–river exchange.