巢湖溶解性有机物时空分布规律及其影响因素

Temporal and Spatial Distribution Characteristics of Dissolved Organic Matter and Influencing Factors in Lake Chaohu

为研究巢湖溶解性有机物(dissolved organic matter,DOM)的时空分布规律及其影响因素,于2013年4月至2014年4月每月在巢湖3个不同湖区17个点位采集表层水样,测定了水体溶解性有机碳(dissolved organic carbon,DOC)和溶解性有机氮(dissolved organic nitrogen,DON)浓度.结果表明,东部、中部和西部这3个湖区DON浓度具有显著差异(P<0.01,n=13),这可能与西湖区入湖河流的外源输入以及DON的可利用性有关.水华期间,水体总氮总磷比、总溶解性氮磷比以及溶解性无机氮(dissolved inorganic nitrogen,DIN)与溶解性活性磷(soluble reactive phosphorus,SRP)比值迅速降低,其中西湖区DIN/SRP在2013年8月降至5±7,表明水体出现氮限制.此外,DON浓度迅速降低,西部湖区叶绿素浓度与DON显著负相关(r=-0.265,P<0.05,n=91),表明在氮限制条件下,DON具有一定生物可利用性.DOC浓度不存在显著空间差异,水温是控制这3个湖区DOC浓度变化的重要因素.东部和中部湖区DOC浓度还受叶绿素和硝态氮浓度的影响.此外,巢湖DOC/DON变幅较大,由于含氮化合物更易降解,因此DON是影响碳氮比值的主导因子,是表征DOM可利用性的重要组分.

To study the temporal and spatial distribution of dissolved organic matter( DOM) and the related influencing factors of Lake Chaohu,surface water samples were collected at seventeen sites in three different regions of the Lake from April 2013 to April 2014.The concentration of dissolved organic carbon( DOC) and dissolved organic nitrogen( DON) were then analyzed. A significance difference in DON concentration was observed among the sampling sites( P < 0. 01,n = 13),which was caused by the terrestrial input from the western rivers and the bioavailability of DON. The ratio of total nitrogen to total phosphorus,total dissolved nitrogen to total dissolved phosphorus,and dissolved inorganic nitrogen to soluble reactive phosphorus( DIN/SRP) declined gradually during the phytoplankton bloom period,especially the ratio of DIN/SRP dropped to 5 ± 7 in August 2013,indicating the nitrogen was limited in lake water. Moreover,the concentration of DON was decreased and a significant negative correlation was observed between DON and Chl-a( r =- 0. 265,P < 0. 05,n = 91),suggesting that DON is bioavailable,and can be utilized by phytoplankton directly or indirectly during nitrogen limitation. No significant difference in DOC concentration was observed and water temperature was the major factor related to the variation of DOC. Chl-a and nitrate concentrations can also affect the dynamics of DOC. In addition,the ratio of DOC/DON was considerably varied,the concentration of DON contributed to the variation of DOC/DON,and DON was the major component contributed to the bioavailability of DOM.