Long-term changes in watershed retention of nitrogen
Long-term changes in watershed retention of nitrogen
复制标题
流域氮滞留的长期变化
DOI：
10.1021/ba-1994-0237.ch008
复制
发表时间：
1994
期刊：
影响因子：
4
通讯作者：
J. Stoddard
中科院分区：
文献类型：
--
作者：
J. Stoddard
当大气中含氮化合物的供应超过流域植物和土壤微生物对这些化合物的需求时，就会发生氮饱和。有几个因素使森林流域氮饱和，包括长期高速率的氮沉积，先进的林分年龄，和大池的土壤氮。在美国东部的许多流域表现出氮饱和的症状。一系列可识别的阶段产生特征的长期和季节性模式的湖水和河水NO3-浓度，反映了这些流域的变化率和相对重要性的N转换成为更多的N充足。氮饱和的早期阶段的特点是增加的严重程度和频率的NO3-事件。后期阶段的氮饱和度的显着升高基流浓度的NO3-从地下水。氮饱和最严重的症状通常发生在氮沉降速率最高的地区。地表水NO3-的长期增加对地表水酸化有重要影响，但可能不会导致淡水富营养化。
Nitrogen saturation occurs when the supply of nitrogenous compounds from the atmosphere exceeds the demand for these compounds on the part of watershed plants and soil microbes. Several factors predispose forested watersheds to N saturation, including chronically high rates of N deposition, advanced stand age, and large pools of soil N. Many watersheds in the eastern United States exhibit symptoms of N saturation. A sequence of recognizable stages produces characteristic long-term and seasonal patterns of lake-water and stream-water NO3-concentrations that reflect the changes in rates and relative importance of N transformations as these watersheds become more N sufficient. The early stages of N saturation are marked by increases in the severity and frequency of NO3-episodes. The later stages of N saturation are marked by elevated baseflow concentrations of NO3-from groundwater. The most advanced symptoms of N saturation usually occur in regions with the most elevated rates of N deposition. Long-term increases in surface-water NO3-have important implications for surface-water acidification, but probably will not lead to freshwater eutrophication.