滇池沉水植物生长过程对间隙水氮、磷时空变化的影响

2015年6-10月通过原位采集滇池沉水植物分布区和无植物对照区柱状沉积物间隙水,分析其溶解性总氮(DTN)和溶解性总磷(DTP)、溶解性无机氮(DIN)和溶解性无机磷(DIP)及溶解性有机氮(DON)和溶解性有机磷(DOP)浓度的时空变化,探讨沉水植物分布对间隙水氮、磷浓度、形态贡献及氮磷比的影响.结果表明:滇池沉水植物生长过程显著影响间隙水氮、磷浓度.与无植物对照区相比,沉水植物生长过程对间隙水氮浓度的削减主要发生在6、8月,而对间隙水磷浓度的削减主要发生在7月,反映了沉水植物对氮、磷两种元素的生物地球化学循环作用机制不同;间隙水氮形态贡献受季节性影响较大,6-7月以DON贡献为主,沉水植物分布区和无植物对照区分别达到61%和84%;而8-10月以DIN贡献为主,沉水植物分布区和无植物对照区分别为76%和75%;沉水植物分布区磷形态贡献随季节波动变化,沉水植物分布区以DOP贡献为主(63%),无植物对照区以DIP贡献为主(62%);沉水植物生长对沉积物间隙水各形态氮磷比影响显著.沉水植物生长显著增加间隙水DTN/DTP比,尤其是DIN/DIP比,相反降低DON/DOP比.沉水植物对间隙水氮、磷吸收及转化过程改变了沉积物氮、磷释放机制,从而影响上覆水氮、磷组成及氮磷比,很可能会影响到浮游植物生长及藻类水华过程,这对于湖泊水质管理具有重要意义.

Spatial-temporal variations of nitrogen and phosphorus forms in sediment porewater as affected by submerged plant in Lake Dianchi

From June to October in 2015, the sediment interstitial water in columnar sediment samples was collected from the areas with/without submerged plants in Lake Dianchi. The concentration of the dissolved nitrogen and phosphorus fraction was analyzed as the changes of space and time, including dissolved total nitrogen(DTN), dissolved inorganic (DIN)and organic nitrogen (DON), dissolved total phosphorus(DTP), and dissolved inorganic (DIP) and organic phosphorus (DOP). The effect of submerged plant distribution on the N, P concentration and N/P ratio were also discussed in this study. The results showed that:(1)The growth process of submerged plants significantly has affected on the concentration of N and P in sediment interstitial water. Compared with the area without plants, the N removal by plants appeared in June and August, while the P removal by plants mostly was in July. The results reflected the biogeochemical effect of the submerged plant on the N, P concentration was obviously different. (2) DON was the main fraction of TN in June and July, accounting for 61% and 84% in the areas with and without submerged plants, respectively. DIN was the main fraction of TN from August to October, accounting for 76% and 75% in the areas with and without submerged plants, respectively. In contrast, DOP always was the primary fraction of TP with the seasons change, but respectively accounted for 63% and 62% in the areas with and without submerged plants. (3) Submerged plants can significantly enhance the ratio of DTN/DTP, especially for the DIN/DIP ratio, but on the contrary for the ratio of DON/DOP. In conclusion, submerged plants can change the N, P release mechanism of sediment through the absorption and transformation process of submerged plant for N and P in sediment interstitial water, and further affected on the N fraction, P fraction and N/P. That may affected the process of phytoplankton growth and algae blooms, which is of great significance to the management of water quality in lakes.