Factors Influencing the Molecular Compositions and Distributions of Atmospheric Nitrogen‐Containing Compounds

Abstract

NOCs deposition from atmospheric particles considerably affects the global nitrogen cycle and can have substantial effects on aquatic and terrestrial ecosystems (Altieri Abstract Atmospheric nitrogen-containing organic compounds (NOCs) are critical components of global nitrogen deposition and light-absorption species. The sources and compositions of NOCs are complex and remain largely unknown. Here, NOCs in 55 ambient aerosol samples collected in Guangzhou, South China, were analyzed via ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry in negative-ion and positive-ion electrospray ionization (ESI) modes. The molecular compositions of NOCs measured via ESI-and ESI+ exhibited considerable differences. NOCs detected in the negative mode were mainly composed of highly oxygenated organic nitrates (O/N = 6), whereas NOCs detected in the positive mode were mainly composed of reduced nitrogen-containing compounds (e.g., amides and amino acids). CHN compounds potentially corresponding to amines and alkaloids showed low abundance in the detection modes. Non-metric multidimensional scaling and individual compound correlation analyses showed that the molecular compositions of NOCs were mainly affected by anthropogenic activities and meteorological parameters. For example, anthropogenic activities such as biomass burning and secondary nitrogen-chemistry processes led to the accumulation of aromatic and highly oxygenated NOCs during winter. During summer, higher OH radical concentrations and temperatures will result in more prevalent or persistent reduced aliphatic NOCs, particularly lipid-like amines. Some variables (e.g., relative humidity) have distinct effects on the variation of different types of NOCs. More research is needed to reveal the influencing mechanisms. This study clarifies the molecular compositions of NOCs and the mechanisms by which various factors influence the molecular variations. The findings can guide the assessment of NOCs evolution and deposition.Plain Language Summary Negative and positive electrospray ionization coupled with Fourier transform ion cyclotron resonance mass spectrometry (ESI-FT-ICR-MS) was used to characterize the molecular composition of nitrogen-containing organic compounds (NOCs) from aerosol samples in Guangzhou. It was determined that a large amount of various NOCs are present in the samples, with NOCs in highly oxidative and reduced states can be roughly identified by distinct ionization modes. By combining the ESI-FT-ICR-MS results and statistical analysis, the factors that associated with the distribution of NOCs and how these factors worked were identified. Anthropogenic activities and meteorological parameters (e.g., temperature and oxidation levels) are the two important drivers that led to the variations of NOCs, resulting to inverse molecular patterns with different response to aromatic/highly unsaturated and saturated structures, respectively. This study provides a useful clue for studying NOCs in complex system, bridges the links between t...

Molecular Signatures and Sources of Fluorescent Components in Atmospheric Organic Matter in South China

“…However, the abundant saturated and reduced N-containing formulas detected by ESI+ FT-ICR-MS were assigned to C4, with 3% of them sharing the same formulas with the ESI− formulas (potential amino acids). 23 This probably indicated that other than CHO compounds lowoxidized/reduced N-containing compounds were also potential fluorophores of C4, but microbial amino acids may have minor influences.…”

“…A puzzling phenomenon in previous studies was that the assigned protein-like FCs in both AOM and aquatic DOM showed insignificant correlations with N-containing species and covaried mainly with CHO formulas, , which was consistent with the results obtained for the ESI– analysis. However, the abundant saturated and reduced N-containing formulas detected by ESI+ FT-ICR-MS were assigned to C4, with 3% of them sharing the same formulas with the ESI– formulas (potential amino acids) . This probably indicated that other than CHO compounds low-oxidized/reduced N-containing compounds were also potential fluorophores of C4, but microbial amino acids may have minor influences.…”

“…Similar carbon concentrations of methanol extracts were directly infused and analyzed using the Bruker 9.4 T solariX XR FT-ICR-MS both in the ESI+ and ESI– modes. The details of the instrumental setting and operational conditions are described elsewhere , and in Text S3. The elemental ratios, modified aromatic index, carbon oxidation state, and double bond equivalent (DBE) were calculated for the chemical formula C c H h O o N n S s (Text S3).…”

“…Year-long 24-h PM 2.5 samples were collected on the roof of the Biaoben Building of the Guangzhou Institute of Geochemistry (Guangzhou, 23.15° N, 113.35° E) from July 2017 to June 2018 (once a week), and a representative subset of 53 PM 2.5 samples was selected for EEM spectra measurement and ESI-FT-ICR-MS analysis (Text S1 and Table S1). , …”

“…Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) is an effective method to obtain the molecular information on AOM. − The joint analysis of two complementary data sets obtained by EEM and FT-ICR-MS analysis in negative electrospray ionization (ESI) mode can effectively establish the relationship between the molecular composition and FCs for soil and hydrological DOM. ,− However, studies have revealed that PRLIS in aquatic DOM are associated mainly with non-N-containing molecules from the ESI– FT-ICR-MS analysis, which was not confirmed to the assigned name. Given that reduced N-containing species (e.g., amino acids) are preferentially detected in ESI+ FT-ICR-MS analysis, , the combined use of ESI+ and ESI– FT-ICR-MS analyses can provide more molecular information for FCs.…”