环胶州湾污水处理厂排放口溶解有机氮生物可利用潜力研究

Potential Bioavailability of Dissolved Organic Nitrogen in the Discharge Outlets of Sewage Treatment Plants Around the Jiaozhou Bay

溶解有机氮(DON)是陆源输入近海总溶解氮(TDN)的重要组成部分,其生物可利用性对探讨近海氮污染和富营养化形成机制具有重要意义.本研究根据2012年7月、2012年11月、2013年3月和2013年5月在胶州湾海域4个污水处理厂进行的4次调查,分析了直排胶州湾污水处理厂水体中总溶解氮(TDN)及其中总溶解氨基酸(TDAA)的含量和季节分布特征,并以溶解有机碳n(DOC)/溶解有机氮n(DON)和氨基酸的构成和丰度为指标,评价了直排胶州湾各污水处理厂排放口DON的生物可利用性.结果表明,TDN的变化范围为413.10~3 580.65μmol·L^(-1),并基本呈现3月和11月高,5月和7月低的变化趋势,其中,DON在TDN中所占摩尔分数变化范围为2.14%~88.75%.各污水处理厂排放口不同季节DOC/DON值较低,介于0.2~26.2 mol·mol^(-1)之间,平均值为(5.05±6.39)mol·mol^(-1),而TDAA中所含碳在DOC中的摩尔分数即TDAA/DOC值较高,分布在0.33%~3.02%之间,平均值为1.54%±0.78%,基于TDAA/DOC估算排入胶州湾各污水处理厂排放口污水中具有生物可利用溶解有机质所占摩尔分数为0.44%~46.97%.上述结果表明,直排胶州湾污水处理厂排放口DON具有较高的生物可利用性,对该海域富营养化贡献不容忽视.

Dissolved organic nitrogen（ DON） is an important portion of total dissolved nitrogen（ TDN） transported to the coastal from land-based sources and its bioavailable moieties of DON are regarded as potentially important nitrogen sources for eutrophication in coastal environments. Based on the four field observations conducted in July,November 2012 and in March,May 2013 at the four sewage treatment plants（ STPs） around the Jiaozhou Bay（ JZB）,the concentrations and compositions of total dissolved nitrogen（ TDN） as well as total dissolved amino acids（ TDAA） were analyzed,and the ratio of dissolved organic carbon（ DOC） to DON and the composition and abundance of amino acids were regarded as indexes to evaluate the bioavailability of DON in STPs around JZB. The concentrations of TDN ranged from 413. 10 μmol·L^（-1）to 3 580. 65 μmol·L^（-1）and showed a seasonal variation tendency,which were higher in March and November and lower in May and July,and the percentages of DON to TDN varied from 2. 14% to 88. 75%. In the discharge outlets of STPs around JZB,the values of DOC/DON were low and ranged from 0. 2 mol·mol^（-1）to 26. 2 mol·mol^（-1）with an average of（ 5. 05 ± 6. 39） mol·mol^（-1）,while the values of TDAA/DOC were high and ranged from 0. 33% to 3. 02% with an average of 1. 54% ± 0. 78%. Based on TDAA/DOC,the bioavailable proportion of the dissolved organic matter was estimated,which accounted for 0. 44% to 46. 97%. In conclusion,DON in the discharge outlets of STPs around JZB possessed high bioavailability and might contribute to the eutrophication of coastal water in JZB.