Studies Of Contents, Composition And Seasonal Variation Of Nitrogen, Amino Acid And Carbohydrate In Nature Colloids

The concentrations, distribution and seasonal variations of nitrogen, amino acids and carbohydrates in nature colloids were examined in surface waters of southeast Xiamen Bay, Jiulongjiang River estuary and Jiulongjiang River of China. Water samples were collected during August 2005 and May 2006 and fractionated into total dissolved (<0.2μm), colloidal (10kDa ~0.2μm) and absolutely dissolved (<10kDa) molecular weight phases with the Cross-flow ultrafiltration system. The sources and transfer of nitrogen, amino acids and carbohydrates in waters were also discussed. Results were as following:1. The decreasing concentrations of nitrogen, amino acids and carbohydrates from river water to sea water showed that terrestrial inputs were important source of nitrogen, amino acids and carbohydrate in estuary and river water.2. The average contribution of ON in truly dissolved to its TN was 22.1% and that in colloidal phase was 57.8% implying that organic nitrogen was the dominant nitrogen species in colloidal phase. The average contribution of nitrate nitrogen to TIN was 89.2% indicating the dominant status of nitrate nitrogen in TIN. There was no significant seasonal variation difference of nitrogen between truly dissolved and colloidal phases in sea and river waters while in estuary seasonal variation of colloidal nitrogen differed from truly dissolved nitrogen suggesting the specialty of colloidal nitrogen.3. The average concentration of THAA in colloidal phase of estuary and river waters were 1.2 and 2 times of that in truly dissolved phase while in sea water THAA in truly dissolved phase was 7.3 times of that in colloidal phase. This indicated that estuary and river colloids were rich in high molecule weight materials such as amino acids. The dominant amino acids were Gly+Thr, Asp and Glu followed by Ala+Tyr, Ser and Phe in truly dissolved phase while in colloidal phase Cys, His and Met were also abundant. It was showed he seasonal variations of THAA in three phases of three waters was similar, however, the change of individual amino acid with seasons was different with...