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The Jiaozhou Bay is characterized by heavy eutrophication that is associated with intensive anthropogenic activities. Four core sediments from the Jiaozhou Bay are analyzed using bulk technologies, including sedimentary total organic carbon(TOC), total nitrogen(TN), the stable carbon(δ~(13)C) and nitrogen(δ~(15) N) isotopic composition to obtain the comprehensive understanding of the source and composition of sedimentary organic matter and further shed light on the environmental changes of the Jiaozhou Bay on a centennial time scale.Results suggest that the TOC and TN concentrations increase in the upper core, having indicated a probable eutrophication process since the 1920 s in the inner bay and the 2000 s in the bay mouth. The TOC and TN concentrations outside the bay have also changed since 1916 owing to the variation of terrigenous input.Considering TOC/TN ratio, δ~(13) C and δ~(15) N, it can be concluded there is a mixture of terrigenous and marine organic matter sources in the study area. A simple two end-member(terrigenous and marine) mixing model usingδ~(13) C indicats that 45%–79% of TOC in the Jiaozhou Bay is from the marine source. The environmental changes of the Jiaozhou Bay are recorded by geochemical proxies, which are influenced by the intensive anthropogenic activities(e.g., extensive use of fertilizers, and discharge of sewage) and climate changes(e.g., rainfall).
The Jiaozhou Bay is characterized by heavy eutrophication that the associated with intensive anthropogenic activities. Four core sediments from the Jiaozhou Bay are analyzed using bulk technologies, including sedimentary total organic carbon (TOC), total nitrogen (TN), the stable carbon (13) C) and nitrogen (δ ~ (15) N) isotopic composition to obtain the comprehensive understanding of the source and composition of sedimentary organic matter and further shed light on the environmental changes of the Jiaozhou Bay on a centennial time scale. Results suggest that the TOC and TN concentrations increase in the upper core, having having a probable eutrophication process since the 1920 s in the inner bay and the 2000 s in the bay mouth. The TOC and TN concentrations outside the bay have also changed since 1916 owing to the variation of terrigenous input.Considering TOC / TN ratio, δ ~ (13) C and δ ~ (15) N, it can be concluded there is a mixture of terrigenous and marine organic matter sources in t A simple two end-member (terrigenous and marine) mixing model using δ ~ (13) C indicats that 45% -79% of TOC in the Jiaozhou Bay is from the marine source. The environmental changes of the Jiaozhou Bay are recorded by geochemical proxies, which are influenced by the intensive anthropogenic activities (eg, extensive use of fertilizers, and discharge of sewage) and climate changes (eg, rainfall).