| Samples of suspended particulate organic matter(SPOM) and surface sediment organic matter were collected in the Poyang Lake area during the dry season and the wet period, respectively,analyzed for stable carbon and nitrogen isotope compositions with using of stable carbon isotope and nitrogen isotope techniques. The origin of suspended particulate matter and surface sediment organic matter were identified, based on values of stable carbon and nitrogen isotope, as well as the correlations between them. The main conclusions are as follows:1、The values of carbon isotope of SPOM were-24.91‰～25.79%o in dry season and-25.88%o--26.91%o in wet season, varied little in the main channel area of Poyang Lake, and prejudiced during dry season than those during wet season.. The r values of nitrogen isotope were6.35%o-10.55%o in dry season and4.20%o-19.69%o in wet season,varied obviously and higher during wet season.and the spatial distribution was similar between the two period.C/N ratios were8.62-9.67in wet season and8.1～10.54in dry season.higher in wet period generally, and varied more significantly among samples during the wet season.2、The values of carbon and nitrogen isotope of surface sediment organic were-12.56‰～-25.66%o and3.51%o-6.26%o in the main channel area of Poyang Lake respectively with similar Distribution trend.The range of C/N ratios were8.97～24.01, larger in the upstream and downstream than those in the middle channel.3、The values of carbon isotope of SPOM were-25.22‰～-27.79%o in wet season26.02%o-28.07%oin dry season, varied little among samples in the five rivers’mouth area; The values of nitrogen isotope were2.87‰～17.49‰in wet season and2.12%o-8.75‰in dry season, varied greatly among samples during wet season than those in dry season while C/N ratios varied little among the samples, as well as variety between the two period. The values of carbon and nitrogen isotope of surface sediment organic were-19.55‰～-24.79%o.2.85%o-4.64%o, respectively, and the range of C/N ratios were8.97～24.01, which showed litter spatial distribution.4、Carbon isotope of SPOM were from C3plants while nitrogen source were from aquatic plants and soil organic matter in the main channel area.the source of organic matter were mainly from soil in the upstream while algae were the origin of the organic matter in the downstream.5、Carbon isotope and nitrogen isotope of SPOM were mainly from the mixture of soil organic matter and aquatic plants in GanJiang south branch estuary while those were from aquatic plants in Ganjiang north branch estuary in wet season,as well as dry season; Organic nitrogen tends to be from terrestrial input and organic carbon were from the mixture of soil organic matter and aquatic plants in both mouth of Fuhe river and Xinjiang river; the Suspended particulate organic matter may be related with fish farming, while the aquatic algae contribute a lot to the organic matter in Xiushui river mouth. The carbon isotope and nitrogen isotope of the organic matter at the surface sediments in the mouth of five rivers were mainly from terrestrial organic matter.6、There were no significant correlations on the value between carbon isotope and chlorophyll a, suspended matter concentration, while the values indicated a significant positive correlation between nitrogen isotope and nitrate, nitrite in the main channel area. The values were from the result of the integrated effects of factors and little correlations with single factor in the mouth of five rivers. Both carbon isotope and nitrogen isotope showed no significant correlation between SPOM and surface sediment organic matter in the main channel area, while nitrogen isotope of suspended organic matter were correlated significantly with values of carbon isotope,C/N ratios of surface sediment organic matter which indicated the similar source in five rivers. |
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