Iodine speciation and size distribution in ambient aerosols at a coastal new particle formation hotspot in China

Abstract

Abstract. Intense new particle formation (NPF) events were observed in the coastal atmosphere during algae growth and farming season at Xiangshan gulf of the east China coast. High nucleation-mode iodine concentrations measured by ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC/Q-TOF-MS) confirmed that the NPF events were induced by iodine species. Our study provides important information on iodine speciation, size distributions, and its role in NPF in the context of heavy air pollution in China's coastal areas. For the first time, we identified 5 inorganic iodine species, 45 organic iodine compounds (35 molecular formulas), and a group of iodide–organic adducts in aerosols. The concentrations and size distributions of iodine species down to 10 nm were measured during the iodine-induced NPF, continental NPF, and non-NPF days at the coastal site and compared to those at an inland site. The iodine in the above four aerosol sample types were characterized by iodate, aromatic iodine compounds, iodoacetic acid or iodopropenoic acid, and iodide–organic adducts, respectively. Iodide and organic iodine compounds were found in the nucleation-mode particles; however, it is still not clear whether they contributed to nucleation or just new particle growth. Wild algae, as well as farmed algae, could be an important NPF source in China's coastal areas.

Role of Gas-Phase Halogen Bonding in Ambient Chemical Ionization Mass Spectrometry Utilizing Iodine

“…However, halogen bonding may play a more important role in the condensed phase found in particles. Yu et al 146 reported the presence of a number of organic iodine compounds in particles in China under conditions where new particle formation was occurring. They proposed formation via electrophilic substitutions involving I + formed from HOI or I 2 .…”

Probing key organic substances driving new particle growth initiated by iodine nucleation in coastal atmosphere

“…Iodine-induced NPF (I-NPF) events were mostly reported in European coastlines (Yoon et al, 2006;Mahajan et al, 2010) and polar regions (Allan et al, 2015;Roscoe et al, 2015;DallÓsto et al, 2018). In 2019 we provided evidences of I-NPF in the southeast coastline of China, based on particle number size distribution and iodine measurements (Yu et al, 2019). The focus of that paper (Yu et al, 2019) is, however, the speciation of organic iodine compounds in size-segregated aerosol samples.…”

“…Three additional sets of blank samples were collected by placing a high efficiency particulate air (HEPA) filter at the gas inlet of nano-MOUDI. Detailed information on aerosol sample collection could be found in Yu et al (2019).…”

“…After being centrifuged for 30 min at 12,000 rpm, the supernatant was collected for total iodine (I) analysis by Agilent 7500a ICP-MS (Agilent Technologies, Santa Clara, CA, USA) and HSO4analysis by UPLC-ESI-Q-TOF-MS. The measurements of HSO4and total I were elaborated in our previous article Yu et al 2019. Another half of each filter was extracted in the same way but used for TOC analysis by a TOC analyzer (Model TOC-5000A, Shimadzu, Japan) and https://doi.org/10.5194/acp-2020-345 Preprint.…”

“…In 2019 we provided evidences of I-NPF in the southeast coastline of China, based on particle number size distribution and iodine measurements (Yu et al, 2019). The focus of that paper (Yu et al, 2019) is, however, the speciation of organic iodine compounds in size-segregated aerosol samples. Moreover, the use of relatively low resolution Time-of-Flight (TOF) mass analyzer and in vitro signal amplification approach in that paper did not allow the detection of the majority of non-https://doi.org/10.5194/acp-2020-345 Preprint.…”