Atmospheric nitrogen deposition in Yangtze River Delta: insights gained from the nitrogen content and isotopic composition of the moss Haplocladium microphyllum

Abstract

Simple and inexpensive estimation of the rates and sources of atmospheric nitrogen (N) deposition is critical for its effective mitigation in a region with different land-use types. In this study, the N content and N isotopic composition (δ 15 N) of moss (Haplocladium microphyllum) tissues and precipitation at six sites with three land-use types (urban, suburban, and rural) were measured in the Yangtze River Delta. A significant linear relationship between moss N content and wet N deposition, and a consistent decrease trend for moss N content and wet N deposition from urban to suburban to rural areas were observed. More negative δ 15 N of suburban and rural mosses indicated N mainly released from agriculture and effluent, while the less negative δ 15 N of urban mosses were mainly influenced by fossil fuel combustion and traffic emissions. Although the negative moss δ 15 N indicates that reduced N dominates wet N deposition, there was no significant correlation between moss δ 15 N and the ratio of ammonium to nitrate (NH 4 + /NO 3 −). These results reveal that the moss N content and δ 15 N can be used as a complementary tool for estimating the rates and sources of wet N deposition in a region with different land-use types. 石生苔藓能指示长三角大气氮湿沉降量及其来源吗？ 摘要 简单有效地估算大气氮沉降量及其来源至关重要。本研究同时收集长三角市区, 郊区, 农村的 雨水和附近的石生细叶小羽藓，分析苔藓氮含量与氮湿沉降量以及苔藓和雨水的氮同位素 (δ 15 N)。结果显示：苔藓氮含量与氮湿沉降量显著相关，均呈市区>郊区>农村趋势。苔藓 δ 15 N表明郊区和农村大气氮湿沉降主要来自农业和人畜废水释放，而市区还受煤炭燃烧和机 动车排放影响。该研究表明石生苔藓氮含量和δ 15 N能用来指示长三角大气氮湿沉降量及其来 源，以弥补传统氮沉降监测数据的缺乏和费时费力的缺点。 ARTICLE HISTORY

Toward a better understanding of cascading consequences of atmospheric reactive nitrogen along its transport pathway

“…Compared with site-based precipitation collection, moss nitrogen was suggested to be a simple technique in estimation of wet nitrogen deposition A significant linear relationship between moss nitrogen content and wet deposition was found by Chen et al (2020). They also determined the nitrogen isotopic composition of moss (Haplocladium microphyllum) tissues and found a more negative value at suburban and rural sites than that at urban sites, due to major contributions from agricultural and nonagricultural sources, respectively.…”