Terrestrial Nitrogen Inputs Affect the Export of Unprocessed Atmospheric Nitrate to Surface Waters: Insights from Triple Oxygen Isotopes of Nitrate
Terrestrial Nitrogen Inputs Affect the Export of Unprocessed Atmospheric Nitrate to Surface Waters: Insights from Triple Oxygen Isotopes of Nitrate
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DOI：
10.1007/s10021-021-00722-9
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发表时间：
2021-11-16
期刊：
影响因子：
3.7
通讯作者：
Eshleman, Keith N.
中科院分区：
文献类型：
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作者：
Bostic, Joel T.;Nelson, David M.;Eshleman, Keith N.
在过去大约150年的时间里，大气硝酸盐（NO3 Atm-）沉积急剧增加，导致生态系统富营养化。NO3 Atm-沉积是普遍的，但不同的景观在调节流域规模的加工和出口的NO3 Atm-的作用仍然不清楚。我们测量了三重氧同位素（示踪剂NO3 Atm-）的NO3-为832流样品收集在基流和暴雨流从14个流域的不同土地利用在整个两年的切萨皮克湾流域，我们用这些数据来评估土地利用对NO3 Atm-的影响。动力学流域农业（> 35%）和发达（> 70%）的土地输出更多的NO3 Atm-比主要森林（> 75%）流域。农业用地可能会促进更大的NO3 Atm-出口，因为陆地氮添加率相对于NO3-消费率的升高。相比之下，发达国家的土地可能有有限的生物处理NO3 Atm-因为更大的水文连接的陆上流动通道的渠道。我们的研究结果，沿着从以前的研究数据，可以解释通过扩展的概念模型的动力学氮饱和度NO3 Atm-跨不同的土地利用流域的流水出口。在这个框架内，陆地氮输入率升高压倒NO3-汇，允许按比例更多的NO3 Atm-从流域泄漏。流域尺度的N输入的变化，增加流NO3-浓度加性影响NO3 Atm-，与农业流域，及其相关的大型陆地N输入，增加NO3 Atm-出口。
Atmospheric nitrate (NO3Atm-) deposition has increased dramatically during the past similar to 150 years and contributes to ecosystem eutrophication. NO3Atm- deposition is widespread, but the role of different landscapes in modulating watershed-scale processing and export of NO3Atm- remains unclear. We measured triple oxygen isotopes (a tracer of NO3Atm-) of NO3- for 832 stream samples collected during baseflow and stormflow from 14 watersheds of varied land use throughout two years in the Chesapeake Bay watershed, and we used these data to assess the influence of land use on NO3Atm-. dynamics. Watersheds with more agricultural (> 35%) and developed (> 70%) land exported more NO3Atm- than predominantly forested (> 75% ) watersheds. Agricultural lands likely facilitate greater NO3Atm- export because of elevated rates of terrestrial N addition relative to rates of NO3- consumption. In contrast, developed lands likely have limited biotic processing of NO3Atm- because of greater hydrologic connectivity of overland flow pathways to channels. Our results, along with data from prior studies, can be interpreted by extending the conceptual model of kinetic N saturation to NO3Atm- streamwater export across varied land use watersheds. In this framework, elevated rates of terrestrial N inputs overwhelm NO3- sinks, allowing proportionally more NO3Atm- to leak from watersheds. Changes in watershed-scale N inputs that increase stream NO3- concentrations additively affect NO3Atm-, with agricultural watersheds, and their associated large terrestrial N inputs, increasing NO3Atm- export.