[Nitrogen and organic matter vertical distribution characteristics and evaluation in ancient canal sediments of Zhenjiang old town].

In order to reveal vertical distribution characteristics of nitrogen and organic matter in the ancient canal sediments of Zhenjiang old town, the columnar sediment samples in Dianli road bridge (D) and Nanshui bridge (B) were collected, contents of total nitrogen (TN), organic nitrogen (Org-N), ammonia nitrogen (NH4(+)-N), nitrate nitrogen (NO3(-)-N) and organic matter (O. M) were determined, and C/N, nutrient concentration coefficient and the correlation of nitrogen, O. M and environmental factors had been analyzed, and organic nitrogen and organic index had also been evaluated. The results showed that (1) The average contents of TN, Org-N, NH4(+) -N, NO3(-) -N and O. M were 366.33 mg x kg(-1), 348.02 mg x kg(-), 89.47 mg x kg(-1), 13.51 mg x kg(-1), 0.43%, respectively, in Dianli road bridge (D). And the average contents of TN, Org-N, NH4(+) -N, NO3(-) -N and O. M were 940.23 mg x kg(-1), 893.22 mg x kg(-1), 169.48 mg x kg(-1), 15.19 mg x kg(-1), 0.76%, respectively, in Nanshui bridge (B). The ranked order of average N and O. M was D < B, which indicated that nitrogen and organic matter pollution in Nanshui bridge (B) was more serious than that in Dianli road bridge (D). (2) The results of C/N indicated that the O. M source of sediment was zooplankton and phytoplankton in ancient canal. (3) There was no significant difference (P > 0.05) of nutrient concentration coefficient between D and B sampling points, which indicated that the concentration process of nitrogen and organic matter was similar in D and B sampling points. (4) TN and O. M were not significantly correlated, which indicated that TN might come from exogenous pollution. (5) The organic index evaluation results showed that ancient canal sediments of Zhenjiang old town were in a cleaning situation, and organic nitrogen still belonged to fairly cleaning and slight cleaning categories.