[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.

[Effect of submerging and wetting-redrying on Cd speciation and uptake by Sorghum hybrid Sudangrass in two paddy soils under spiked Cd].

Effect of continuous submerging and wetting-redrying on cadmium speciation and uptake by Sorghum hybrid Sudangrass in a Ferric-accumulic Stagnic Anthrosol and a Tipical Hapludult collected from the Taihu Lake region and the rolling downs of Yingtan, Jiangxi, China respectively, was studied by pot experiment with Cd spike in 2003. Compared to that under wetting-redrying treatment, the MgCl2-extracted pool of Cd in Huangnitu with spiked Cd of 5mg x kg(-1) and 10mg x kg(-1) was decreased from 21.8% and 28.5% to 8.0% and 16.9% while NH2OH x HCl-extracted pool increased from 17.7% and 17.3% to28.1% and 37.5% under continuous submerging. However, in the Typical Halpudult, NaAC-extracted pool of Cd decreased from 20.8% and 29.6% to 11.6% and 12.6%. Cd uptake by Sorghum hybrid Sudangrass was found in negative correlation with the MgCl2 extracted pool of Cd. Total Cd uptake was significantly reduced by the pretreatment of continuously submerging in Huangnitu.