The Content and Distribution of Nitrogen in Nature Colloids from Jiulongjiang River

The content, distribution and seasonal variations of nitrogen in nature colloids were examined in surface waters of south Xiamen Bay Jiulongjiang River estuary and Jiulongjiang River of China. Water samples were fractionated into total dissolved (< 0.2 mu m) colloidal (10 kDa-0.2 mu m) and truly dissolved (< 10 kDa) phases with the cross-flow ultrafiltration system. Results showed that average concentrations of different nitrogen species in truly dissolved phase were evidently higher than those in colloidal phase and concentrations of NO2- NO3- NH4+ TN TIN and ON were 52 238 18 9 39 and 3 times higher respectively. In addition NO3- was the most abundant inorganic species and was 11-28 times as high as NH4+ and NO2- in truly dissolved phase but 2-15 times as high as NH4+ and NO2- in colloidal phase. NO2- NO3- NH4+ TN and TIN in truly dissolved phase make up 77.2%-100.0% of that in total dissolver phase while those of colloidal phase make up only 0-19.0%; ON contents in truly dissolved phase made up 42.2%-69.3% of that in total dissolved phase while those of the colloidal phase made up 30.7%-57.9% of them. This indicated that IN species were distributed mainly in truly dissolved phase (< 10 kDa) in natural aquatic environments and ON was distributed mainly in colloidal phase (10 kDa-0.22 mu m). It was also found that the seasonal variations of all N species in truly dissolved phase was similar to that of total dissolved phase in all waters from different sources. There was slight variation of NO2- and NH4+ with season. The NO3- was highest in April and March and lowest in August and November. The seasonal variation of ON was related to the water sources. The contents of all N species in both dissolved phase and truly dissolved phase decreased from river to sea.