• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Freshwater science >Patterns of diel variation in nitrate concentrations in the Potomac River
【24h】

Patterns of diel variation in nitrate concentrations in the Potomac River

机译：波托马克河硝酸盐浓度的二极管变化模式

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

The Potomac River is a large source of N to Chesapeake Bay, where reducing nutrient loads is a focus of efforts to improve trophic status. Better understanding of NO3- loss, reflected in part by diel variation in NO3- concentrations, may refine model predictions of N loads to the Bay. We analyzed 2 y of high-frequency NO3- sensor data in the Potomac to quantify seasonal variation in the magnitude and timing of diel NO3- loss. Diel patterns were evident, especially during low flow, despite broad seasonal and flow-driven variation in NO3- concentrations. Diel variation was similar to 0.01 mg N/L in winter and 0.02 to 0.03 mg N/L in summer with intermediate values in spring and autumn, equivalent to <1% of the daily mean NO3- concentration in winter and similar to 2 to 4% in summer. Maximum diel NO3- values generally occurred in mid- to late morning, with more repeatable patterns in summer and wider variation in autumn and winter. Diel NO3- loss reduced loads by 0.7% in winter and 3% in summer. These losses were less than estimates of total in-stream NO3- load loss across the basin that averaged 33% of the annual groundwater contribution to the river. Water temperature and discharge had stronger relationships to the daily magnitude of diel NO3- variation than did photosynthetically active radiation. Estimated diel areal NO3- loss rates were generally >1000 mg N m(-2) d(-1), greater than most published values because measurements in this large river integrate over a greater depth/unit stream bottom area than do those from smaller rivers. These diel NO3- patterns are consistent with the influence of photoautotrophic uptake and related denitrification, but we cannot attribute these patterns to assimilation alone because the magnitude and timing of diel dynamics were affected to an unknown extent by processes, such as evapotranspiration, transient storage, and hydrodynamic dispersion. Improvements to diel loss estimates will require additional high-frequency measures, such as dissolved O-2, dissolved organic N, and NH4+, and deployment of 2 measurement stations.
机译：None

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号