[Effect of Drought and Subsequent Re-wetting Cycles on Transferable Nitrogen and Its Form Distribution in the Sediment of Water Level Fluctuating Zone in the Tributary of Three Gorge Reservoir Areas].
Nitrogen is the most comment source of eutrophication in freshwater systems. In current study, we investigated the various forms of transferable nitrogen in sediments, which potentially contributed to the nitrogen output into waters. Sediments samples were collected in the water level fluctuating zone of Pengxi River crossing three hydrological sections, e. g. upstream, midstream and downstream and two water level altitudes, 160 m and 170 m, with multiple depths for each site, 0-20, 20-40, 40-60, 60-80, 80-100 cm. To characterize the response of transformation of nitrogen in sediment of the water level fluctuating zone towards cycles of drought and re-wetting processes, we analyzed the content and distribution of transferable nitrogen (TF-N) and its forms. The result showed that the changing of the amount of total nitrogen followed the pattern of upstream > midstream > downstream, the mean value was in the range of 313.02-3 255.53 mg. kg-1, while the content of total transferable nitrogen was on an average of 639.40 mg . kg-1 and coincided with the pattern of total nitrogen. In addition, TF-N followed the pattern of OSF-N > IMOF-N > OSF-N > IEF-N. It indicated that both OSF-N and IMOF-N dominated the form of TF-N in sediments by proportions of 50. 9% and 33. 3%, respectively. Since the transformation rate of OSF-N into dissolved phase was relatively slow, its contribution as a source of nitrogen to eutrophication was limited. We, thus, concluded that IMOF-N was the most important fraction which could be potentially affected by water fluctuation and contributed as dissolved nitrogen into water phase. This study indicated that the manner of manipulating water resource in the Three Gorges Reservoir area has raised the potential risk of transforming IMOF-N from sediment into water phase.
Jun-jie
JJ
Lin
Shuai
S
Zhang
Zhen-yu
ZY
Yang
Li-ping
LP
He
Nong
N
Zhou
Qian-ru
QR
Zhang
D002681:China; D055864:Droughts; D005068:Eutrophication; D019015:Geologic Sediments / Q000737:chemistry*; D009584:Nitrogen / Q000032:analysis*; D045483:Rivers / Q000737:chemistry*; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000032:analysis*
D014874:Water Pollutants, Chemical; D009584:Nitrogen