Relationship between catchment characteristics and nitrogen forms in Cao-ERiver Basin, Eastern China
JIN Shuquan , LU Jun , CHEN Dingjiang , SHEN Yena , SHI Yiming
DOI:
Received May 14, 2008,Revised July 28, 2008, Accepted , Available online
Volume 21,2009,Pages 429-433
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The distribution of di erent nitrogen forms and their spatial and temporal variations in di erent pollution types of tributaries or
reaches were investigated. Based on the catchments characteristics the tributaries or reaches can be classified into 4 types, including
headwater in mountainous areas (type I), agricultural non-point source (NPS) pollution in rural areas (type II), municipal and industrial
pollution in urban areas (type III), and combined pollution in main stream (type IV). Water samples were collected monthly from July
2003 to June 2006 in the Cao-E River Basin in Zhejiang, eastern China. The concentrations of NO3??-N, NH4
+-N, and total nitrogen
(TN) were measured. The mean concentrations of NO3??-N were decreased in the sequence type IV > type II> type III > type I,
whereas, NH4
+-N, total organic nitrogen (TON), and TN were in the sequence: type III > type IV > type II> type I. In headwater and
rural reaches, CNO??3 ??N was much higher than CNH+4 ??N. In urban reaches, TON and NH4
+-N were the main forms, accounting for 54.7%
and 32.1% of TN, respectively. In the whole river system, CNH+4 ??N decreased with increasing distance from cities, and CNO??3 ??N increased
with the increasing area of farmland in the catchments. With increased river flow, CNO??3 ??N increased and CNH+4 ??N decreased in all types
of reaches, while the variations of CTON and CTN were di erent. For TN, the concentration may be decreased with the increase of river
flow, but the export load always increased.
