Impact of an accidental explosion in Tianjin Port on enhanced atmospheric nitrogen deposition over the Bohai Sea inferred from aerosol nitrate dual isotopes

Abstract

In recent years, emergent pollutant's accidents have occurred frequently in China, causing serious harm to the ecological environment. In this study, the impact of an accidental fire and explosion at Tianjin Port in 2015 on the atmosphere over the Bohai Sea was explored. Results showed sharp increases in the concentrations of several important components of fine particulate matter (e.g. NO 3 − , SO 4 2− , NH 4 + , organic carbon, elemental carbon) over Beihuangcheng Island after the explosion. Among them, NO 3 − was most affected (about 10 days), with a maximum concentration of 16.45 μg m −3. The δ 15 N-NO 3 − ranged from −1.58‰ to +8.74‰, with an average of +2.79‰ ± 3.32‰. Influenced by the explosion, δ 15 N-NO 3 − decreased significantly, which was in accordance with the industrial processes of explosives. The δ 18 O-NO 3 − varied between +49.40‰ and +69.52‰, and showed a marked increase (+66.62‰ ± 3.92‰) in the explosion-affected period. Using Monte Carlo simulation, the •OH pathway for NO 3 − formation was 51.79% ± 10.94% at that timemuch lower than in the regular period. The elevated dry deposition of NO 3 − caused by the explosion was 266.08 μmol N m −2 d −1 over the Bohai Seaagain, much higher than in the regular period. With the dry nitrogen deposition of NH 4 + (42.41 μmol N m −2 d −1), the total nitrogen deposition increased by 308.49 μmol N m −2 d −1 , leading to severe ecological risk. Through the inverse computation of the dry deposition flux of NO 3 − , the affected area over the Bohai Sea was less than 1.42 × 10 4 km 2 , which is about 20% of the total area. 利用气溶胶硝酸盐双同位素评估天津港爆炸事故对渤海地区大气氮沉降的影响 摘要 近年来，我国突发性污染事故频繁发生，对生态环境造成了严重危害。本研究基于气溶胶硝酸 盐的氮氧同位素确认并评估了2015年天津港火灾爆炸事故对渤海地区大气氮沉降的影响研究 结果表明δ 15 N-NO 3 − 与δ 18 O-NO 3 − 范围分别为−1.58‰至+8.74‰与+49.40‰ 至+69.52‰ 受到火 灾爆炸影响，δ 15 N-NO 3 − 显著下降，而δ 18 O-NO 3 − 明显上升。火灾爆炸导致渤海地区大气氮沉降 量增加308.49 μmol N m −2 d −1 ，其中硝态氮为266.08 μmol N m −2 d −1 ，总影响区域约为渤海面积 的1/5。本研究显示同位素技术是污染事故研究中重要的示踪手段。 ARTICLE HISTORY

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

“…Of the aerosol constitutes, nitrate was most affected. Its concentrations peaked at 16.5 μg m −3 one week after the explosion, as observed at an island 300 km downwind of Tianjin (Zong et al 2020). After the explosion, the stable nitrogen isotope of aerosol nitrate decreased significantly from +7.33‰ to −1.58‰.…”