Regional variability in the atmospheric nitrogen deposition signal and its transfer to the sediment record in Greenland lakes

Regional variability in the atmospheric nitrogen deposition signal and its transfer to the sediment record in Greenland lakes
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大气氮沉降信号的区域变化及其向格陵兰湖泊沉积物记录的转移

DOI:
10.1002/lno.10936
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发表时间:
2018
影响因子:
4.5
通讯作者:
Anderson N
Anderson N
中科院分区:
地球科学1区
文献类型:
--
作者:
Anderson N

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氮循环的破坏是全球环境变化的主要组成部分。湖泊沉积物中的δ 15 N越来越多地被用作活性氮输入的量度,但问题是,并非所有站点都记录到特征性的δ 15 N亏损信号。我们采用区域重复采样策略,沿着格陵兰岛西南部的降水和N沉积梯度,以评估湖泊沉积物岩心中δ 15 N信号强度的决定因素。积雪N和δ 15 N-NO3和水化学的分析与散装沉积物δ 15 N相结合。研究地点包括积雪δ 15 N梯度(冰盖:-6 ‰;海岸10‰)、大气氮沉降(冰盖边缘:0.2 kg ha− 1 yr −1;海岸:0.4 kg ha− 1 yr −1)和湖沼学。三个来自沿海湖泊的210 Pb定年沉积物岩心显示,约1000年的δ 15 N下降。 1‰,反映了积雪N的δ 15 N强烈亏损,湖泊总N(TN)浓度较低(约300μg N L−1)和较高的TN负荷。沿海湖泊有3.7-7.1倍的积雪输入的硝酸盐比内陆网站,而总沉积的值是1.7-3.6倍,为湖泊和整个集水区沉积。在内陆站点和靠近冰盖边缘的湖泊,较低的大气氮沉积速率和较大的湖泊总氮库导致对氮固定和再循环的依赖程度更大(大多数内陆湖泊的平均沉积物δ 15 N为0.5-2.5‰;n= 6)。大气δ 15 N沉积信号向湖泊沉积物转移的主要控制因素是外部N输入相对于湖内N库的大小。
Disruption of the nitrogen cycle is a major component of global environmental change. δ15N in lake sediments is increasingly used as a measure of reactive nitrogen input but problematically, the characteristic depleted δ15N signal is not recorded at all sites. We used a regionally replicated sampling strategy along a precipitation and N‐deposition gradient in SW Greenland to assess the factors determining the strength of δ15N signal in lake sediment cores. Analyses of snowpack N and δ15N‐NO3and water chemistry were coupled with bulk sediment δ15N. Study sites cover a gradient of snowpack δ15N (ice sheet: −6‰; coast 10‰), atmospheric N deposition (ice sheet margin: ∼ 0.2 kg ha−1yr−1; coast: 0.4 kg ha−1yr−1) and limnology. Three210Pb‐dated sediment cores from coastal lakes showed a decline in δ15N of ca. 1‰ from ∼ 1860, reflecting the strongly depleted δ15N of snowpack N, lower in‐lake total N (TN) concentration (∼ 300μg N L−1) and a higher TN‐load. Coastal lakes have 3.7–7.1× more snowpack input of nitrate than inland sites, while for total deposition the values are 1.7–3.6× greater for lake and whole catchment deposition. At inland sites and lakes close to the ice‐sheet margin, a lower atmospheric N deposition rate and larger in‐lake TN pool resulted in greater reliance on N‐fixation and recycling (mean sediment δ15N is 0.5–2.5‰ in most inland lakes;n= 6). The primary control of the transfer of the atmospheric δ15N deposition signal to lake sediments is the magnitude of external N inputs relative to the in‐lake N‐pool.
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