College of Environment and Safety Engineering, Shenyang University of Chemical Technology, Shenyang, 110142, Liaoning, China.
Research Institute No. 240, China National Nuclear Corporation, Shenyang, 110135, Liaoning, China.
Environ Monit Assess. 2023 Dec 19;196(1):63. doi: 10.1007/s10661-023-12098-5.
Nitrogen dioxide (NO) is a ubiquitous atmospheric pollutant, and fossil fuel combustion is generally considered its predominant source in and around urban areas. As the total nitrogen deposition is high over here, soil NO emissions from urban green space might also be an important local source of ground-level NO. In this study, Willems badge samplers were employed to monitor the spatial and seasonal variations of 2-week mean atmospheric NO concentrations at a height of 1.7 m on an urban campus in Northeast China from November 2020 to December 2021. We found considerable small-scale spatial variations of ground-level NO concentrations on the campus during the growing season, with local soil NO emissions as the main driver. According to its linear correlation with green space coverage, the increment in ground-level NO concentration was partitioned into two components, with one ascribed to the local soil source (referred to as NO-I) and the other the local vehicle source (NO-I). NO-I generally reached a maximum (as high as 25.6 μg/m) during early spring, while its ratio to the background value generally reached a maximum (could be >1) during late spring and could reach 0.52 to 0.92 during summer. Therefore, soil NO emissions were an important source of ground-level NO on the campus, with the contribution even higher than those of other anthropogenic sources during late spring. Even with light traffic on the campus, NO-I could reach 0.48 times the background value at a site with high frequencies of warm starts.
二氧化氮（NO）是一种普遍存在的大气污染物，化石燃料燃烧通常被认为是城市及其周边地区 NO 的主要来源。由于这里的总氮沉积量很高，城市绿地的土壤 NO 排放也可能是近地面 NO 的一个重要本地来源。本研究采用 Willems 徽章采样器，于 2020 年 11 月至 2021 年 12 月，在位于中国东北地区的一个城市校园内 1.7 米高处，监测了 2 周平均大气 NO 浓度的空间和季节性变化。我们发现，在生长季节，校园内近地面 NO 浓度存在可观的小规模空间变化，主要驱动因素为局部土壤 NO 排放。根据其与绿地覆盖率的线性相关性，将地面 NO 浓度的增量分为两部分，一部分归因于局部土壤源（称为 NO-I），另一部分归因于局部车辆源（NO-I）。NO-I 通常在早春达到最大值（高达 25.6 μg/m），而其与背景值的比值通常在春末达到最大值（可大于 1），在夏季可达 0.52 至 0.92。因此，土壤 NO 排放是校园近地面 NO 的一个重要来源，其贡献甚至高于春末其他人为源的贡献。即使校园内交通流量较轻，在频繁暖启动的站点，NO-I 也可能达到背景值的 0.48 倍。
