Supplementary information files for article: 'Regional variability in the atmospheric nitrogen deposition signal and its transfer to the sediment record in Greenland lakes'

Supplementary information files for article: 'Regional variability in the atmospheric nitrogen deposition signal and its transfer to the sediment record in Greenland lakes'.<br>Abstract: 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‐NO3 and water chemistry were coupled with bulk sediment δ15N. Study sites cover a gradient of snowpack δ15N (ice sheet: −6‰; coast urn:x-wiley:00243590:media:lno10936:lno10936-math-000110‰), atmospheric N deposition (ice sheet margin: ∼ 0.2 kg ha−1 yr−1; coast: 0.4 kg ha−1 yr−1) and limnology. Three 210Pb‐dated sediment cores from coastal lakes showed a decline in δ15N of ca. urn:x-wiley:00243590:media:lno10936:lno10936-math-00021‰ from ∼ 1860, reflecting the strongly depleted δ15N of snowpack N, lower in‐lake total N (TN) concentration (∼ 300 μg 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.

论文《格陵兰湖泊大气氮沉降信号的区域差异及其向沉积物记录的传递》补充信息文件。摘要：氮循环紊乱是全球环境变化的核心组成部分。湖泊沉积物中的δ¹⁵N正日益被用作活性氮输入的衡量指标，但存在关键局限：并非所有研究点位均能记录到特征性的贫化δ¹⁵N信号。本研究沿格陵兰西南部的降水与氮沉降梯度，采用区域重复采样策略，以解析调控湖泊沉积物岩芯中δ¹⁵N信号强度的关键因素。本研究将积雪氮、δ¹⁵N-NO₃（硝酸盐氮同位素比值）与水化学分析结果，同全沉积物δ¹⁵N测定相结合。研究站点覆盖了积雪δ¹⁵N梯度（冰盖：−6‰；海岸：urn:x-wiley:00243590:media:lno10936:lno10936-math-000110‰）、大气氮沉降梯度（冰盖边缘：~0.2 kg ha⁻¹ yr⁻¹；海岸：0.4 kg ha⁻¹ yr⁻¹）以及湖沼学特征梯度。对3根来自沿海湖泊、经²¹⁰Pb定年的沉积物岩芯分析显示，自约1860年起，δ¹⁵N值下降了约urn:x-wiley:00243590:media:lno10936:lno10936-math-00021‰，这一现象反映了积雪氮极强的贫化δ¹⁵N特征、湖泊内较低的总氮（Total Nitrogen, TN）浓度（~300 μg N L⁻¹）以及更高的总氮负荷。沿海湖泊的积雪硝酸盐输入量是内陆点位的3.7~7.1倍，而就总沉降而言，沿海湖泊及整个集水区的沉降量则是内陆的1.7~3.6倍。在冰盖边缘附近的内陆点位与湖泊中，较低的大气氮沉降速率与更大的湖泊内总氮库，使得生态系统更依赖固氮作用与氮循环再利用（多数内陆湖泊的沉积物δ¹⁵N均值为0.5~2.5‰；样本量n=6）。大气δ¹⁵N沉降信号向湖泊沉积物传递的主要调控因子，是外源氮输入量相对于湖泊内氮库的规模。