红枫水库和普定水库碳、磷、硅生源要素时空分布特征

Temporal and Spatial Distribution Characteristics of Carbon, Phosphorus and Silicon in the Water Column of Hongfeng Reservoir and Puding Reservoir

选取了营养盐浓度和水体滞留时间存在明显差异的普定水库和红枫水库作为研究对象,通过对两个水库碳、磷、硅生源要素时空变化的分析,揭示了河流筑坝水库营养盐时空分布的主要影响因素。分析结果显示:普定水库表层水体溶解性无机碳(DIC)、总磷(TP)、溶解性总磷(DTP)和溶解性硅(DSi)大体上均表现出冬季较高、夏季较低的变化趋势;而在垂向分布上,除冬季外,其他三个季节均表现出表层水体较低、底层水体较高的趋势。红枫水库DIC变化趋势与普定水库类似。而红枫水库TP和DTP大致表现为冬夏季偏低、春秋季偏高;由于浓度较低,各个季节垂向变化趋势均不明显。夏季红枫水库底部水体DSi显著高于表层水体,而其他三个季节DSi在垂向剖面上波动较小。两水库表层水体DIC与叶绿素a(Chla)呈负相关,且夏季普定水库和红枫水库表层水体DIC稳定碳同位素(δ^(13)C_(DIC))显著高于底层,而DIC则表层水体显著低于底层水体。综合分析结果表明,浮游植物光合作用是影响普定水库和红枫水库碳、磷、硅生源要素时空分布的最主要因素。营养盐水平较高、水体滞留时间较短的普定水库,其Chla低于营养盐水平较低、水体滞留时间较长的红枫水库。这反映出对于河流筑坝水库而言,水体滞留时间(水动力条件)比营养盐对浮游植物生物量的影响更显著。因此,在制定水库污染防治措施时,需结合水体滞留时间,差异化、经济合理地制定水质控制/修复目标。

Puding Reservoir and Hongfeng Reservoir, which are significantly different in nutrient concentration and hydraulic retention time, were investigated for the temporal and spatial variations of the biogeneic elements of carbon, phosphorus, and silicon in the water volume, and the main factors affecting the temporal and spatial distribution of nutrients in the river-dammed reservoirs were revealed. The results showed that dissolved inorganic carbon(DIC), total phosphorus(TP), dissolved total phosphorus(DTP) and dissolved silicone(DSi) concentrations of the surface water of Puding Reservoir generally were higher in winter and lower in summer. In the vertical distribution, all of them were lower in the surface water than in the bottom water, except in winter. The DIC variation trend of Hongfeng Reservoir was similar to that of Puding Reservoir. The TP and DTP concentrations of Hongfeng Reservoir were generally lower in winter and summer, and higher in spring and autumn. As TP and DTP concentrations were very low, the vertical variation in each season was not obvious. The DSi concentration of Hongfeng Reservoir was significantly higher in the bottom water than in the surface water in summer, while it fluctuated slightly in the vertical profile in the other three seasons. The DIC concentration in the surface water of the two reservoirs was negatively correlated with Chla. The stable carbon isotope of DIC(δ^(13)C_(DIC)) value was significantly higher in the surface water than in the bottom water, while the DIC concentration was significantly lower in the surface water than in the bottom water in both reservoirs in summer. These results showed that phytoplankton photosynthesis was the most important factor affecting the temporal and spatial distribution of carbon, phosphorus and silicon in Puding Reservoir and Hongfeng Reservoir. The Chla concentration in Puding Reservoir, with a relatively higher nutrient level and shorter hydraulic retention time, was significantly lower than that in Hongfeng Reservoir, which has a relatively lower nutrient level and longer hydraulic retention time. This reflected that hydraulic retention time(hydrodynamic conditions) played a more significant role on phytoplankton biomass than nutrients for river-dammed reservoirs. Therefore, when formulating reservoir pollution prevention and control measures, it is necessary to establish water quality control/remediation goals in a differentiated, economical and reasonable way in accordance with the hydraulic retention time.