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| Stable organic nitrogen isotope in core sediments of the Three Rivers Estuary, Poyang Lake and its environmental implications |
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Abstract Samples of core sediments from the Three Rivers Estuary of Poyang Lake (Ganjiang River south branch, Fuhe River, Xinjiang River west branch and Poyang Lake) were collected. The compositions of stable nitrogen isotope (δ15N), C/N ratio, total organic carbon (TOC) and total nitrogen (TN) in these samples were determined for investigating the origin of sedimentary organic matter and nitrogen. The results showed that δ15N ranged from 2.44‰ to 4.55‰, 4.03‰ to 5.84‰, 3.79‰ to 4.81‰ and 3.42‰ to 8.13‰ in the sediment for the Ganjiang River south branch, Fuhe River, Xinjiang River west branch and Poyang Lake, respectively. The sedimentary organic matter was mainly from the soil organic matter in Ganjiang River. The sources of sedimentary organic matter were generally autochthonous in Fuhe River. The sources were mainly from the algae and the soil organic matter below 12cm, and autochthonous up 12cm in the sedimentary organic matter of Xinjiang River. In Poyang Lake, the sedimentary organic matter was autochthonous in the surface layer; the contribution of soil organic matter was obvious from 6cm to 3cm; the algae and the soil organic matter were the main sources of the sedimentary organic matter below 7cm. Chemical fertilizer and soil erosion were the main sources of nitrogen in sediments for Ganjiang River, Xinjiang River and Poyang Lake. The sources of nitrogen in the sediment were mainly from the soil erosion for Fuhe River.
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Received: 25 May 2014
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