δ15N values in Lake Erie sediments as indicators of nitrogen biogeochemical dynamics during cultural eutrophication
δ15N values in Lake Erie sediments as indicators of nitrogen biogeochemical dynamics during cultural eutrophication
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DOI：
10.1016/j.chemgeo.2010.02.002
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发表时间：
2010-04
期刊：
影响因子：
3.9
通讯作者：
YueHan Lu;P. Meyers;T. Johengen;B. Eadie;J. Robbins;Haejin Han
中科院分区：
文献类型：
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作者：
YueHan Lu;P. Meyers;T. Johengen;B. Eadie;J. Robbins;Haejin Han
我们测量了伊利湖东部盆地两个相隔15年（1988年和2003年）采样的沉积物柱样的稳定氮同位素值（δ 15 N），并将其与2003年柱样的总磷（TP）和生物硅（BSi）浓度进行了比较。TP，BSi和总氮（TN）的积累在2003年核心的变化对应于三个阶段的营养历史，包括发病（1910年至1950年），高峰（1950年至1970年），和改善（1970年至2003年）的富营养化由于加速营养负荷。从1910年到1970年，BSi：TP原子比（BSi：TPat）逐渐下降，表明在湖泊进行性富营养化过程中，硅逐渐下降，导致硅限制和硅藻沉降速率降低。δ 15 N值在1950年至1970年期间表现出明显的变化，这与湖泊流域径流中N的快速增加相对应。1910 ~ 1970年间δ 15 N值呈逐渐增大的趋势，这可能是湖心盆地缺氧底沃茨发育引起的反硝化作用的结果。这项研究说明了从沉积物中δ 15 N值提取环境信息的复杂性，并确认需要进一步研究湖泊δ 15 N记录的多个过程及其相互作用。
We have measured the stable nitrogen isotope values (δ15N) in two sediment cores sampled 15years apart (1988 and 2003) from the Eastern Basin of Lake Erie and compared them to the total phosphorus (TP) and biogenic silica (BSi) concentrations in the 2003 core. Changes in the TP, BSi and total nitrogen (TN) accumulations in the 2003 core correspond to three stages in the trophic history of the lake that include the onset (∼1910 to ∼1950), peak (∼1950 to ∼1970), and amelioration (∼1970 to 2003) of eutrophication owing to accelerated nutrient loading. Decreasing BSi:TP atomic ratios (BSi:TPat) from ∼1910 to ∼1970 suggest a gradual Si drawdown in the lake during its progressive eutrophication, which led to Si limitation and reduced diatom settling rates. δ15N values show pronounced variability in ∼1950 to ∼1970, which corresponds with rapid increases in N from runoffs from the lake catchment. A trend of gradually increasing δ15N values from ∼1910 to ∼1970 is likely the result of denitrification associated with the development of anoxic bottom waters in the Central Basin of the lake. This study illustrates the complexity of extracting environmental information from δ15N values in sediments and confirms the need for further studies of the multiple processes and their interactions that contribute to lacustrine δ15N records.