无锡市农村黑臭河流沉积物营养盐垂向分布与污染特征分析

Vertical distribution and pollution characteristics of nutrient in sediment of rural malodorous black river in Wuxi City,China

为揭示太湖流域农村黑臭河流沉积物中碳、氮、磷营养盐的垂向分布与污染特征,以无锡市周铁镇掌下浜(北段)为例,沿河流上游至下游共采集13个沉积物柱状样,分析总氮(TN)、总磷(TP)、氨氮(NH_4^+-N)、硝氮(NO_3^--N)、有机氮(Org-N)、有机碳(TOC)的垂向分布特征,并对沉积物中碳(C)、氮(N)、磷(P)的组分分布进行相关性分析。结果表明:TN、TP、Org-N含量在各点位间变化幅度不同,但均表现出随深度增加减小的趋势,即出现明显的"表层富集"现象,TN、TP、OrgN含量在沉积物中的最大降幅分别为55.82%、69.59%和68.12%;相反,沉积物中NH_4^+-N含量在垂直距离上呈现随深度加大升高的趋势,上升幅度在25.39%~72.77%;在垂直方向上,NO_3^--N含量在1号、4号~8号采样点处含量随深度加大而升高,增幅最大为107.51%,在2号、3号和9号~13号采样点处含量随深度增加降低,降幅最大为65.17%;TOC含量呈现随深度增加递减的趋势,含量在13.12~37.52 g·kg^(-1)变化;沉积物中C/N在8.31~19.90之间,均值为13.21,有机物以外源有机质为主;C/P比在12.24~51.84之间,均值为26.71;N/P在1.04~2.86之间,均值为2.02;沉积物中TOC、TN、TP含量两两具有极显著正相关关系(p<0.01,n=13),表明C、N和P具有同源性。

To reveal the vertical distribution and pollution characteristics of carbon,nitrogen and phosphorus in the sediment of malodorous black river along countrysideof Lake Taihu,this study took the northern section of Zhangxia River,in Zhoutie town of Wuxi City as the research target. Thirteen sediment cores were collected from the Zhangxia River,of which the concentration and vertical distribution of total nitrogen（ TN）,total phosphorus（ TP）,ammonia nitrogen（ NH_4＋-N）,nitrate nitrogen（ NO_3-N）,organic nitrogen（ Org-N） and total organic carbon（ TOC） were analyzed. In addition,the pairwise concentration correlations between carbon（ C）,nitrogen（ N）,and phosphorus（ P） in the sediments were analyzed. The results showed that TN,TP,Org-N showed a decreasing trend with depth,namely surfacial enrichment,yet NH_4＋-N showed a trend of increase with the depthin the sediments. Vertically,NO_3--N increased with the depth at No. 1,No. 4 to 8 sampling sites,while it decreased with the depth at No. 2,No. 3 and No. 9 to 13 sampling sites. The concentrations of TOC showed a decrease trend. The ratio of C / N in sediments varied from 8. 31 to 19. 90 with a mean of 13. 21,andexogenous organic matter was the predominant form of organic matters; the ratio of C / P varied from 12. 24 to 51.84 with a mean of 26. 71; the ratio of N / P varied from 1. 04 to 2. 86 with a mean of 2. 02. A significant positive pairwise correlation existedbetween TOC,TN and TP concentrations in the sediments（ p〈0. 01,n = 13）,suggestingthat C,N and P could be homologousthe northern section of Zhangxia River,a typical rural malodorous black river in Wuxi City.