Sedimented Organic Nitrogen Isotopes in Freshwater Wetlands Record Long-Term Changes in Watershed Nitrogen Source and Land Use
详细信息 查看全文
- 作者：Emily M. Elliott and Grace S. Brush
- 刊名：Environmental Science & Technology
- 出版年：2006
- 出版时间：May 1, 2006
- 年：2006
- 卷：40
- 期：9
- 页码：2910 - 2916
- 全文大小：181K
- 年卷期：v.40,no.9(May 1, 2006)
- ISSN：1520-5851
文摘
Although historic land use is widely recognized as animportant determinant of watershed N cycling, efforts toexamine land use legacy effects are limited by incompletehistorical data. This research evaluates N isotopes ofsedimented organic matter (
15Norg), in a palynologicalcontext, as a long-term proxy of changes in N source towetland biota. N and S isotope measurements of organicsediments, fossil plant fragments, and living plants areused to explore isotope stratigraphies of wetland sedimentcores. Processes potentially contributing to isotopestratigraphies are investigated including the following: achange in N source, diagenesis, and denitrification.We document the 15Norg stratigraphy of a core from theSmithsonian Environmental Research Center, MD, U.S.A.spans approximately 350 years, during which time 15Norgincreases from +2” to +7”. Reconstructed populationdensity and wastewater inputs to the watershed suggest thatthe increase in 15N reflects changing land use fromforested conditions to increasing nutrient inputs from humanwaste. Our results illustrate the importance of hydrologicconnectivity in delivering waste-derived N in a watershedcharacterized by relatively low human population density.These results also demonstrate how this approach canexpand the temporal horizon over which we can assesshuman impacts to watershed N dynamics.
15Norg), in a palynologicalcontext, as a long-term proxy of changes in N source towetland biota. N and S isotope measurements of organicsediments, fossil plant fragments, and living plants areused to explore isotope stratigraphies of wetland sedimentcores. Processes potentially contributing to isotopestratigraphies are investigated including the following: achange in N source, diagenesis, and denitrification.We document the 15Norg stratigraphy of a core from theSmithsonian Environmental Research Center, MD, U.S.A.spans approximately 350 years, during which time 15Norgincreases from +2” to +7”. Reconstructed populationdensity and wastewater inputs to the watershed suggest thatthe increase in 15N reflects changing land use fromforested conditions to increasing nutrient inputs from humanwaste. Our results illustrate the importance of hydrologicconnectivity in delivering waste-derived N in a watershedcharacterized by relatively low human population density.These results also demonstrate how this approach canexpand the temporal horizon over which we can assesshuman impacts to watershed N dynamics.