胶州湾沉积物氮的环境生物地球化学意义

利用氮的分级浸取技术,研究了胶州湾不同粒级沉积物中氮的赋存形态.研究表明,胶州湾沉积物中可转化态氮可分为离子交换态、弱酸浸取态、强碱浸取态和强氧化剂浸取态.不同粒级沉积物中各形态氮占可转化态氮的比例各不相同.在细、中和粗粒级沉积物中,强氧化剂浸取态氮是可交换态氮的优势形态,分别占可转化氮的35.38%、44.38%和58.69%.在中、粗粒级沉积物中,强碱浸取态氮是无机氮的主要赋存形态,分别占可转化态氮的26.31%和25.85%.在细粒级沉积物中,离子交换态氮是优势态的无机氮,占可转化态氮的27.67%.相关分析表明,对于胶州湾来说,沉积物的粒度越细,氮的含量就越高,各形态氮大致与细、中粒级沉积物含量呈正相关,而与粗粒级沉积物含量呈负相关.研究还表明,不同粒级沉积物中氮与浮游植物数量、叶绿素a以及上覆水体中硝酸盐的含量大致都在一定程度上呈正相关,这一方面说明了沉积物对上覆水体元素的含量有着不可忽视的影响,另一方面也说明了沉积物中的氮对海水的富营养化水平有着较好的指示和十分重要的环境意义.

Environmental Biogeochemical Significance of Nitrogen in Jiaozhou Bay Sediments

The geochemical characteristics of nitrogen forms in different grain size sediments of Jiaozhou Bay were investigated employing the sequential extraction technique. Results showed that the transferable nitrogen in Jiaozhou Bay sediments can be divided into four forms: ion exchangeable form (IEF-N), weak acid extractable form (WAEF-N), strong alkaline extractable form (SAEF-N) and strong oxidant extractable form (SOEF-N). The percentages of nitrogen forms for transferable nitrogen in different grain size sediments were different. Generally, for all grain size sediments, the SOEF-N was the primary form accounted for 35.38%, 44.38% and 58.69% of transferable nitrogen for fine, medium and coarse sediments. And for medium and coarse grain size sediment, SAEF-N was the dominant inorganic nitrogen accounted for 26.31% and 25.85%, respectively. And for fine-grained sediments, IEF-N was the primary inorganic nitrogen accounted for 27.67% of transferable nitrogen. The correlation analysis showed that generally, nitrogen was positive correlated with fine and medium grain size but negative correlation with coarse sediments. In addition, nitrogen in different grain size sediments had also positive correlations with phytoplankton abundance, chlorophyll-a and NO3- concentrations of overlying water. The results showed that sediments have great influences on element concentrations of overlying water, and on the other side, it also illustrated that sedimentary nitrogen is an excellent indicator of hypereutrophication and has essential environmental significance.