DOI: 10.5061/dryad.c866t1gmf
title: Chloramine chemistry as a missing link in atmospheric chlorine cycling

description: Chlorine radicals (Cl·) profoundly impact atmospheric oxidation capacity.
 Chloramines, especially trichloramine (NCl3), are emerging precursors of
 Cl·. However, their sources and roles in the atmosphere remain elusive.
 This study presents field evidence of primary emissions and explicit
 secondary production pathways of atmospheric NCl3 in Beijing, supplemented
 by observations from New Delhi and reanalysis of measurements in Toronto.
 We demonstrate that the sequential chlorination reactions initiated by
 molecular chlorine (Cl2) and ammonia (NH3) in atmospheric aerosols are a
 major source of NCl3. The NCl3 produced in aerosols is a source of gaseous
 NCl3 and serves as an intermediate during the conversion from Cl2 to Cl·,
 while direct NCl3 emissions constitute a previously overlooked source of
 Cl·. Overall, chloramine chemistry alters the Cl· production mechanism and
 represents a crucial missing pathway to Cl· worldwide.
description: # Chloramine chemistry as a missing link in atmospheric chlorine cycling
 Dryad DOI: 10.5061/dryad.c866t1gmf All field observation data used and
 codes developed for this manuscript and Table S15. ## Description of the
 data and file structure Beijing_obs_data.csv Hourly averaged data, forward
 averaging is applied, e.g., the timestamp for the average of measurements
 from 2022/1/22 00:00 to 2022/1/22 01:00 is 2022/1/22 00:00. Time indicates
 local Beijing time 1. Time series of reactive chlorines mixing ratios, in
 units of part per trillion (ppt) 2. Time series of trace gases and
 volatile organic compounds mixing ratios, in units of part per billion
 (ppb) 3. Meteorological parameters: Temp refers to temperature in units of
 degrees Celsius RH refers to relative humidity in units of % WD refers to
 wind direction in units of degrees WS refers to wind speed in units of
 meters per second Precipitation in units of millimeters 4. Aerosol
 composition data (chloride, nitrate, sulfate, and ammonium) in units of
 μg/m^3^ 5. Gas-phase data (NH~3~, HCl and HNO~3~) in unit of μg/m^3^ n/a
 indicates not available due to the lack of measurements or instrument
 malfunction Delhi_obs_data.csv Hourly averaged data, forward averaging is
 applied, e.g., the timestamp for the average of measurements from
 2023/2/23 18:00 to 2023/2/23 19:00 is 2023/2/23 18:00. Time indicates
 local Delhi time 1. Time series of reactive chlorines mixing ratios, in
 units of part per trillion (ppt) 2. Time series of PM2.5 mass
 concentration in units of μg/m^3^ and solar radiation in units of W/m^2^
 n/a indicates not available due to the lack of measurements or instrument
 malfunction Table_S15.xlsx Table S15 in the supplementary material ##
 Sharing/Access information Links to other publicly accessible locations of
 the data: *
 [https://doi.org/10.6084/m9.figshare.30305371](https://doi.org/10.6084/m9.figshare.30305371) ## Code/Software Code_BoxModel.zip: MATLAB version R2024b, please find the detailed readme file in the corresponding .zip file MATLAB packages: Statistics Toolbox, Curve Fitting Toolbox, and Optimization Toolbox Code_ML.zip: Codes for Machine Learning Environment: OS: Windows 11 Professional CPU: 11th Gen Intel(R) Core(TM) i7-1165G7 @ 2.80GHz IDE: Visual Studio Code 1.78.0 Python: 3.8.8 Python packages used in this paper are shown in requirements.txt Launch: 1\. install vscode # [https://code.visualstudio.com/docs/supporting/faq#_previous-release-versions](https://code.visualstudio.com/docs/supporting/faq#_previous-release-versions) 2\. install Python3.8.8 # [https://mirrors.huaweicloud.com/python/3.8.8/](https://mirrors.huaweicloud.com/python/3.8.8/) 3\. Install Python package in terminal: pip install -r requirements.txt 4\. install jupyter and select python3.8.8 as interpreter # following hint of vscode 5\. running main.ipynb step by step Please find the detailed readme file in the corresponding .zip file