2026-10-11T00:23:11Z https://api.figshare.com/v2/oai

oai:figshare.com:article/34031524 2026-09-30T11:06:55Z category_7 category_14 category_272 category_873 category_106 category_45 category_734 category_61 category_64 category_133 portal_63 item_type_6 month_year_09_2026

Trace Methylamine Drives Efficient Photochemical HONO Formation on Aged Urban Grime Bowen He (5434409) Bai Li (72384) Zhu Ran (22452765) Yan Ren (149348) Qingxin Deng (20107586) Jiangping Liu (1885537) Manolis Romanias (22468413) Adrien Gandolfo (5760059) Xinming Wang (510004) Lei Li (29537) Sasho Gligorovski (5760071) Medicine Molecular Biology Environmental Sciences not elsewhere classified Chemical Sciences not elsewhere classified Science Policy Sociology Biological Sciences not elsewhere classified Developmental Biology Cancer Plant Biology regenerating photoactive pyrene oh radical budgets 5 × 10 different experimental conditions 97 ev without aging process reduces 25 ± 2 10 </ sup aged urban grime 2 </ sub urban grime laboratory conditions 17 ev 01 ev values reported urban hono trace methylamine relative humidity quantitatively assess promoted pathway photochemical reactivity nitrous acid molecules cm like sites hydrogen carrier 50 ppb 40 ppb 35 )% The aging process reduces the photochemical reactivity of urban grime. Here, we show that two-month accumulated urban grime from Guangzhou sustains highly efficient photochemical conversion of NO₂ to nitrous acid (HONO) in the presence of trace methylamine (MA). Under UV-A irradiation and 80% relative humidity, MA addition increased HONO yields up to (91.25 ± 2.35)% at 40 ppb MA, while 50 ppb MA generated a maximum measured surface flux of 2.5 × 10¹⁰ molecules cm^–2 s^–1, of the same order of magnitude as values reported for NH₃-promoted urban grime under different experimental conditions. Using density functional theory, we reveal that MA acts as a hydrogen carrier, lowering the activation barrier for HONO formation from 1.12 to 1.01 eV under photoexcitation and, critically, reduces the barrier for regenerating photoactive pyrene-like sites from 2.97 eV without MA to only 0.17 eV in the presence of MA. While MA substantially promotes HONO formation under laboratory conditions, its specific ambient contribution remains unquantified. Aged urban grime stays photochemically active with MA, marking it a persistent daytime HONO source. This MA-promoted pathway should be included in urban air quality models to quantitatively assess its contributions to urban HONO and OH radical budgets. 2026-09-30T00:00:00Z Text Journal contribution 10.1021/acs.estlett.6c00821.s001 https://figshare.com/articles/journal_contribution/Trace_Methylamine_Drives_Efficient_Photochemical_HONO_Formation_on_Aged_Urban_Grime/34031524 CC BY-NC 4.0