| 高原亚深水湖泊沉积物内源磷释放特征与控制途径研究 |
| 杨永琼
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| 导师 | 陈敬安
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| 2013
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| 学位授予单位 | 中国科学院研究生院
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| 学位授予地点 | 北京
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| 学位名称 | 博士
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| 学位专业 | 环境科学
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| 关键词 | 红枫湖
磷释放
磷钝化
天然/改性粘土
影响因素
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| 摘要 | 水体磷含量是湖泊富营养化最主要的限制因子之一。伴随着湖泊流域工农业发展，外源污染物长期的输入致使沉积物中蓄积了大量的磷及其它污染物。湖泊沉积物一方面是水体磷重要的汇，但另一方面也是水体磷重要的源。在单纯控制湖泊外源污染条件下，沉积物磷的释放仍可导致水体持续富营养化，湖泊水质得到明显改善往往需要数十年。因此，要彻底改善湖泊水质，在控制外源污染物输入的同时，还必须进行湖泊污染底泥治理。由于水体深度较大，生物修复技术和底泥环保疏浚在高原亚深水型湖泊难以实施，探索有效的原位钝化技术是控制该类型湖泊沉积物内源磷释放的关键。 本文选取贵州红枫湖这一典型高原亚深水型湖泊为研究对象，通过对大坝和后五湖区的系统采样观测、实验室模拟和野外试验示范，研究揭示高原亚深水型湖泊沉积物磷的释放特征，探索建立适合该类型湖泊的沉积物磷原位钝化技术，取得了如下主要成果和认识： (一) 温度对沉积物磷释放有重要影响，温度升高促进沉积物磷的释放。受沉积物物理化学性质及沉积物磷来源的影响，大坝湖区沉积物磷释放量较大，在不同温度下均表现为磷“源”；后五湖区沉积物磷释放量在15℃时达到最高，表现为沉积物磷“源”，在5℃和25℃时沉积物磷释放量减少，表现为磷“汇”。不同温度下，后五沉积物磷“源-汇”的转换可能受沉积物-水界面细菌种类和数量的影响。 (二) 红枫湖沉积物中易受碱性环境影响的NaOH-P含量较高，偏碱性水体(pH=9.5)可促进沉积物磷的释放，在弱酸性和中性环境下，沉积物磷释放量较小。厌氧环境或对沉积物进行灭菌，可促进沉积物磷的释放。 (三) 根据不同湖区沉积物、不同温度条件下磷释放的模拟实验结果，估算出红枫湖沉积物磷释放量为19~27 t/a，沉积物释放的磷最终仍然会沉降至沉积物或被迁移进入下游水体，因此，控制沉积物磷污染的关键是降低沉积物-水界面磷的交换通量。 (四) 天然粘土的磷吸附及沉积物磷钝化效果研究结果表明，天然粘土具有较强的阳离子交换性，但磷吸附效果较差，不能有效抑制沉积物磷的释放。天然粘土主要通过表面吸附、物理阻隔作用及离子交换作用减少和控制沉积物磷的释放。 (五) 对不同改性粘土(沸石、钠基膨润土、钙基膨润土)的沉积物磷钝化效果的对比研究结果表明：①HCl、NaCl溶液改性粘土不能抑制沉积物磷释放；②硫酸铝改性粘土具有较好的磷吸附效果，磷吸附效率与改性粘土中粘土含量呈正相关关系；③粘土经改性后可促进Ca2+释放，从而有效提高磷吸附量。磷吸附效率总体上为改性钠基膨润土>改性钙基膨润土>改性沸石；④受Al(OH)3吸附特点的影响，硫酸铝改性粘土的DRP钝化效率大于TP钝化效率；⑤增加粘土的用量或向水体添加缓冲剂，可减缓水体因铝离子水解造成的pH值下降。 (六) 对不同环境条件下(温度、pH、离子强度、DO、生物活性、磷含量)硫酸铝改性粘土的磷钝 化实验研究结果表明：①硫酸铝改性粘土能有效减少不同环境条件下沉积物磷和重金属离子的释放，对水环境基本没有负面影响；②水体pH值是影响磷钝化效果的主要因素，酸性条件下的磷钝化效率最低，碱性环境下的磷钝化效率最高；③水体温度、离子强度、DO及上覆水磷含量对改性粘土的磷钝化效果影响较小。 (七) 在红枫湖后五湖湾进行了野外钝化试验，试验采用2:1硫酸铝改性粘土为钝化剂，结果表明：①钝化剂有效减少了水体DRP含量，增加了水体透明度；②由于风浪及水域面积的影响，钝化剂对水体TP含量减少不明显；③应用硫酸铝改性粘土不会导致水体pH值明显降低，也不会导致Al3+含量超标。 本文的创新性成果体现在：通过对红枫湖沉积物磷释放特征、沉积物磷钝化机理与模拟实验的深入研究，遴选出适合于高原亚深水型湖泊的沉积物磷钝化剂，建立了有效的沉积物磷原位钝化技术，为该类型湖泊沉积物内源污染控制提供了科学指导和技术支撑。 |
| 其他摘要 | Phosphorus (P) is one of the limited factors for eutrophication. With the industrial and agricultural development, a large amount of phosphorus and other pollutants were inputted and accumulated in sediments. Sediments play an important role in overall phosphorus (P) cycling in Lake Ecosystem, which are thought to act both as a sink and a source of P due to continuous transport of P across the sediment–water interface. Phosphorus can be released from sediments into overlying water under certain environmental conditions, which may have a significant impact on water quality and delay eutrophic lake recovery. If only exogenous pollution is controlled, the lake water will be improved in at least several decades of years. To improve water quality thoroughly, it will be necessary to control the phosphorus release from sediments. In this paper, Hongfeng Lake, a typical plateau sub-deep lake in Guizhou Province, was selected as the research object. Through systematic sampling, observation, laboratory simulation and field practice for the Daba and Houwu of Hongfeng Lake, we revealed the release characteristics of sediment phosphorus in plateau sub-deep lakes, and explored the in-situ P inactive technology. The main findings and conclusions are as fellows: (1) Temperature is one of the main factors affecting the phosphorus release from sediments. Higher temperature promotes the phosphorus release from sediments. Phosphorus released from Daba sediments was significantly much more than that of Houwu sediments because of their differences in the physical and chemical properties. At Daba area, the sediments always acted as the source of phosphorus at different temperatures. At Houwu area, the sediments acted as the source of phosphorus at 15℃, when phosphorus released from sediments in the highest, while at the temperature of 5℃ and 25℃ the sediments acted as the sink of phosphorus. The shifting between source and sink of Houwu sediments at different temperature may be dominated by bacteria types and quantities. (2) There was no differences in phosphorus release from sediments when the pH of the overlying water was weakly acidic and neutral. The amount of phosphorus release from sediments increased obviously at weak alkaline environment. Anaerobic environment and sediments for sterilization, can promote phosphorus release from sediments. (3) According to the phosphorus release from different sediments at different temperatures, the overall phosphorus release of the Hongfeng Lake sediments is estimated to be 19~27 t/a.The released phosphorus will be finally deposited or migrated downstream. The key to control the sediment phosphorus pollution is to reduce the phosphorus flux at the sediment-water interface. (4) The efficiency of phosphorus adsorption and sediment phosphorus inactivation of natural clay was studied. The results showed that the natural clay has big cation exchange capacity, but phosphorus adsorption effect is too poor to inhibit the phosphorus release from sediments. Natural clay can reduce the phosphorus release from sediments mainly by surface adsorption, ion exchange, and physical barrier effect. |
| 学科领域 | 环境地球化学
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| 语种 | 中文
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| 文献类型 | 学位论文
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| 条目标识符 | http://ir.gyig.ac.cn/handle/352002/5830
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| 专题 | 研究生_研究生_学位论文
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推荐引用方式
GB/T 7714 |
杨永琼. 高原亚深水湖泊沉积物内源磷释放特征与控制途径研究[D]. 北京. 中国科学院研究生院,2013.
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