| 三峡小江回水区氮素赋存形态与季节变化特点 |
| 摘要点击 2564 全文点击 2146 投稿时间：2008-07-20 修订日期：2008-11-28 |
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| 中文关键词 三峡水库 小江回水区 氮素赋存形态 季节变化 循环特点 |
| 英文关键词 Three Gorges Reservoir Xiaojiang backwater area forms of nitrogen seasonal variation characteristic of cycling |
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| 中文摘要 |
| 氮素是浮游植物生长的关键生源要素之一，本研究对2007年3月～2008年3月三峡小江回水区水中氮素的跟踪观测结果进行总结，分析不同形态氮素季节变化过程与相对组成特点.研究期间，回水区TN的平均浓度为(1?553±43) μg·L-1，季节差异显著但总体呈上升趋势.DIN平均浓度为(1?031±32) μg·L-1，占TN平均浓度的66.38%，是该水域氮素的主要赋存形态，其中NO-3-N含量较高说明小江回水区总体上处于较强氧化环境且自净能力较强.DON、PON平均浓度分别为(273±23) μg·L-1、(249±23) μg·L-1，占TN的26.48%和24.15%；DON/PON比值为3.63±0.93，说明该水域氮素代谢强度与周转速率较高.小江回水区DIN在TN中所占比重从2007年3月约占TN的80%逐渐下降到2008年春季约占TN的60%，而TON在TN中的比重则相应上升，说明氮素赋存形态向有机态转变的趋势明显；而对DIN-TN和TON-TN的log-log线性模型斜率比较发现TON对TN的贡献将随TN浓度的升高而增大，表明该水域营养水平有升高的趋势.NH+4-N/NO-3-N同TON/TN存在显著正相关关系，说明TON相对丰度的增加有可能使水体向还原性环境转变.同时NH+4-N相对丰度的变化同水中DON含量及其在TN中所占比重关系密切，但该水域DON氨化降解成NH+4-N并再次被利用的内循环过程是否存在或会否成为调控氮素循环的关键过程有待更深入的研究. |
| 英文摘要 |
| Nitrogen is one of the key nutrients for phytoplankton. Seasonal variation of different forms of nitrogen in Xiaojiang backwater area (XBA) in Three Gorges Reservoir from Mar. 2007 to Mar. 2008 was reported. It was found that average concentration of total nitrogen (TN) during the research period was (1553±43) μg·L-1. Although remarkable seasonal variability of TN, it showed a general trend of increase of TN during the research period. Dissolved inorganic nitrogen (DIN) was the major form of nitrogen with an average concentration of (1031±32) μg·L-1, amounted up to 66.38% in TN. The relatively high level of nitrate in DIN indicated that XBA remained a strong oxidation environment with a good self-purification generally. Mean value of the concentration of dissolved organic nitrogen (DON) and particulate organic nitrogen (PON) were (273±23) μg·L-1 and (249±23) μg·L-1, taking up to 26.48% and 24.15% in TN separately. However, the DON/PON ratio was only 3.63±0.93, which represented the intensive nitrogen cycling and high turnover rates. The amount of DIN in TN decreased from 80% in Mar. 2007 to 60% in Mar. 2008, which showed a trend that forms of nitrogen had been transferring from inorganic forms to organic forms. Compared to the lower slope of DIN-TN log-log linear model, the relatively high slope of TON-TN log-log linear model indicated the contribution of total organic nitrogen (TON) to TN would become significant with the increase of TN. Meanwhile, the positive correlation between NH+4-N/NO-3-N and TON/TN indicated the increase of TON in TN might contribute to a reductive environment in XBA. Nevertheless, it also showed a close relationship between ammonia and DON, but whether the ammonification of DON existed or might become the controlling process of nitrogen cycling in XBA still needs further study. |
