研究生知识库

富营养化是当前全球关注的水环境问题。中国西南地区深水水库正面临着富营养化问题的挑战，沉积物内源磷的输入被认为是造成这一现状的重要原因。目前针对这些深水水库沉积物-水界面磷的时空变化特征和释放机理的原位、高分辨率研究很少。本研究以贵州省典型深水水库红枫湖和阿哈水库为研究对象，运用薄膜扩散梯度技术（DGT）和高分辨率透析技术（HR-peeper），开展了为期一年的沉积物-水界面磷（P）、铁（Fe）、硫（S）时空分布特征的原位、高分辨率月度监测研究，取得了以下主要认识：（1） 红枫湖、阿哈水库沉积物-水界面理化性质均存在显著的季节变化特征。水温、溶解氧分别呈现“夏高冬低”和“夏低冬高”变化规律，库区水质总磷含量夏季（>0.03 mg/L）高于冬季（<0.02 mg/L），表明夏季缺氧期沉积物内源磷释放对上覆水体磷贡献较大，冬季好氧期较小。（2） 原位、高分辨率研究结果表明，红枫湖沉积物-水界面活性P、Fe浓度垂向变化规律一致，皮尔森相关性分析显示沉积物活性P、Fe浓度呈现极显著正相关性（r2> 0.70, p < 0.001），表明红枫湖沉积物内源磷释放主要受控于铁结合态磷还原溶解。（3） 阿哈水库沉积物-水界面活性P、Fe浓度无明显相关性。与红枫湖相比，阿哈水库沉积物具有明显高的锰（Mn）、S含量。在夏季缺氧期，阿哈水库沉积物-水界面活性S浓度处于很高水平（平均浓度超过130 μg/L）。阿哈水库沉积物活性S、Mn可能对Fe、P耦合地球化学循环产生重要影响。 （4） 红枫湖、阿哈水库沉积物中总磷平均含量分别为1820 mg/kg和1415 mg/kg，约为中国典型富营养化湖泊太湖、洞庭湖等沉积物TP含量的2~3倍。红枫湖、阿哈水库沉积物内源磷释放速率较高，平均表观扩散速率分别高达0.220 mg/m2?d和0.372 mg/m2?d。因此，沉积物内源磷是红枫湖、阿哈水库水体P的重要来源。中国西南深水水库沉积物磷污染严重、内源磷释放速率较高，在水环境保护治理中应引起重视。

Eutrophication has become a global environmental problem. Reservoirs in southwestern China are encountering the challenge of eutrophication, in which internal phosphorus (P) release from sediments plays an important role. Studies on the high-resolution profile variations and release mechanisms of P at the sediment-water interface (SWI) are rare in these reservoirs until now. In this study, monthly monitoring using the diffusive gradient in thin films (DGT) technique and high resolution dialysis technology (HR-peeper) were taken to determine the temporal and vertical profile variations of the DGT-labile P, iron (Fe) and sulfur (S) at the SWI in Aha Reservoir and Hongfeng Lake. The main conclusions were summarized as follows:(1) Seasonal variations of physical and chemical properties in water were investigated in Hongfeng Lake and Aha Reservoir. Water temperature and dissolved oxygen showed the characteristics of "high in summer and low in winter" and "low in summer and high in winter". The total P concentration in summer (>0.03 mg/L) was higher than that in winter (<0.02 mg/L). The results showed that the contribution of sediment P release to P in overlying water was greater in summer anoxic period, but smaller in winter aerobic period.(2) In-situ, high resolution studies showed that coincident concentration variations of the active P and -Fe in the vertical profiles were observed in Hongfeng Lake. Pearson correlation analysis showed that there was a significant positive correlation between the concentration of active P and Fe in sediments (r2> 0.70, p < 0.001), suggesting that the P release from sediments is mainly controlled by the reductive dissolution of Fe-bounded P in Hongfeng Lake.(3) There was no significant correlation between active P and Fe concentrations at the SWI in Aha Reservoir. The sediment of Aha Reservoir has higher Mn and S contents compared with that of Hongfeng Lake. During the summer hypoxia period, the concentration of active S at the SWI of Aha Reservoir was at a very high level (the average concentration exceeded 130 ug/L). Active S and Mn in sediments of Aha Reservoir seem to have an important influence on the coupling geochemical cycle of Fe and P. (4) The average total TP content in the sediments of Hongfeng Lake and Aha Reservoir was 1820 mg/kg and 1415 mg/kg, respectively, which was about 2-3 times of that in typical eutrophic lakes such as Taihu Lake and Dongting Lake. The internal P diffusion flux at the SWI was remarkably high in Hongfeng Lake and Aha Reservoir, with a mean apparent diffusion flux value of 0.220 mg/m2?d, 0.372 mg/m2?d, respectively. Therefore, the internal P is an important source of overlyingwater P in Hongfeng Lake and Aha Reservoir. Deep-water reservoirs in southwest China have serious phosphorus pollution in sediments and high release rate of internal phosphorus, which should be paid attention to in water environmental protection.