Volatile organic compound fluxes and source apportionment factor fluxes measured by Proton-Transfer-Reaction Time-of-Flight Mass Spectrometer (PTR-TOF-MS), Delhi, India, November 2018
https://doi.org/10.5285/9fdea71b-7719-4c2f-8ddf-7311ecdb4418
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This dataset contains high‑frequency measurements of volatile organic compounds (VOCs) and their surface-atmosphere fluxes collected at an urban site in Old Delhi, India. The measurements capture both VOC concentrations and bidirectional fluxes, allowing users to investigate emission and deposition processes within a densely populated megacity. Data were collected between 9 October and 23 November 2018 at a 25‑metre tower located at the Indira Gandhi Delhi Technical University for Women (IGDTUW), within an urban footprint influenced by traffic, domestic combustion, industrial activity, evaporative sources and occasional pyrotechnic events.
The dataset includes 5 Hz VOC concentration time series from a Proton‑Transfer‑Reaction Time‑of‑Flight Mass Spectrometer (PTR‑QiTOF‑MS), co‑located high‑frequency wind measurements from a sonic anemometer, Virtual Eddy Accumulation (VEA) updraft and downdraft concentration data, and fluxes derived using both standard eddy‑covariance and numerical VEA methods. It also provides Positive Matrix Factorisation (PMF) outputs, including source‑resolved VOC factors and their associated fluxes. Relevant meteorological variables and supporting chemical indicators are included to aid interpretation.
These data allow users to assess local emission sources, bidirectional VOC exchange, diurnal patterns, and chemical drivers relevant to ozone formation and atmospheric reactivity. The dataset is suitable for researchers studying urban air pollution, VOC source apportionment, atmospheric chemistry and model development.
The work was supported by the Natural Environment Research Council (NE/P016502/1, NE/P016472/1, NE/L002558/1 and NE/R000131/1) and the Earth System Science Organization, Ministry of Earth Sciences (Government of India, MoES/16/19/2017-APHH)
The dataset includes 5 Hz VOC concentration time series from a Proton‑Transfer‑Reaction Time‑of‑Flight Mass Spectrometer (PTR‑QiTOF‑MS), co‑located high‑frequency wind measurements from a sonic anemometer, Virtual Eddy Accumulation (VEA) updraft and downdraft concentration data, and fluxes derived using both standard eddy‑covariance and numerical VEA methods. It also provides Positive Matrix Factorisation (PMF) outputs, including source‑resolved VOC factors and their associated fluxes. Relevant meteorological variables and supporting chemical indicators are included to aid interpretation.
These data allow users to assess local emission sources, bidirectional VOC exchange, diurnal patterns, and chemical drivers relevant to ozone formation and atmospheric reactivity. The dataset is suitable for researchers studying urban air pollution, VOC source apportionment, atmospheric chemistry and model development.
The work was supported by the Natural Environment Research Council (NE/P016502/1, NE/P016472/1, NE/L002558/1 and NE/R000131/1) and the Earth System Science Organization, Ministry of Earth Sciences (Government of India, MoES/16/19/2017-APHH)
Publication date: 2026-03-20
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Format
Comma-separated values (CSV)
Spatial information
Study area
Spatial representation type
Tabular (text)
Spatial reference system
WGS 84
Spatial resolution
25 metres
Temporal information
Temporal extent
2018-10-09 to 2018-11-23
Provenance & quality
The dataset was generated using high‑frequency VOC measurements collected with a PTR‑QiTOF‑MS mounted on a 25‑metre tower, with air sampled through a high‑flow PFA inlet. The instrument recorded VOC mass spectra at 5 Hz. Simultaneous three‑dimensional wind measurements were obtained from a co‑located sonic anemometer to enable eddy‑covariance flux calculations. Raw VOC data were first corrected for detector dark counts, mass‑calibration drift, inlet‑flow variations and humidity‑related sensitivity changes. High‑frequency VOC and wind data were time‑aligned and screened for instrument malfunction, anomalous periods and low‑turbulence conditions.
Fluxes were calculated using standard eddy‑covariance methods, including coordinate rotation, detrending, and the application of frequency‑response corrections. Numerical Virtual Eddy Accumulation (VEA) was then applied to generate updraft and downdraft VOC concentrations weighted by vertical‑wind fluctuations. Positive Matrix Factorisation (PMF) was performed on these VEA‑derived concentration datasets to identify VOC source factors. Factor‑specific fluxes were calculated from the resolved VEA concentration differences combined with measured wind statistics.
Quality‑assurance steps included comparison of VEA‑derived fluxes with conventional eddy‑covariance fluxes for individual ions, with results agreeing within expected uncertainty. Instrument zero checks, calibration procedures and filter changes were conducted routinely. Flux periods that did not meet standard eddy‑covariance QA criteria (such as non‑stationarity or insufficient turbulence) were removed. All processing steps were documented, and intermediate outputs were reviewed to ensure that mass closure was maintained and that PMF residuals were within acceptable limits.
Fluxes were calculated using standard eddy‑covariance methods, including coordinate rotation, detrending, and the application of frequency‑response corrections. Numerical Virtual Eddy Accumulation (VEA) was then applied to generate updraft and downdraft VOC concentrations weighted by vertical‑wind fluctuations. Positive Matrix Factorisation (PMF) was performed on these VEA‑derived concentration datasets to identify VOC source factors. Factor‑specific fluxes were calculated from the resolved VEA concentration differences combined with measured wind statistics.
Quality‑assurance steps included comparison of VEA‑derived fluxes with conventional eddy‑covariance fluxes for individual ions, with results agreeing within expected uncertainty. Instrument zero checks, calibration procedures and filter changes were conducted routinely. Flux periods that did not meet standard eddy‑covariance QA criteria (such as non‑stationarity or insufficient turbulence) were removed. All processing steps were documented, and intermediate outputs were reviewed to ensure that mass closure was maintained and that PMF residuals were within acceptable limits.
Licensing and constraints
This dataset is available under the terms of the Open Government Licence 
Cite this dataset as:
Cash, J.M.; Nemitz, E.; Acton, W.J.; Di Marco, C.F.; Mullinger, N.J.; Langford, B. (2026). Volatile organic compound fluxes and source apportionment factor fluxes measured by Proton-Transfer-Reaction Time-of-Flight Mass Spectrometer (PTR-TOF-MS), Delhi, India, November 2018. NERC EDS Environmental Information Data Centre. https://doi.org/10.5285/9fdea71b-7719-4c2f-8ddf-7311ecdb4418
Correspondence/contact details
Authors
https://orcid.org/0000-0002-8567-1377 Other contacts
Publisher
NERC EDS Environmental Information Data Centre
info@eidc.ac.uk
Rights holder
UK Centre for Ecology & Hydrology
Additional metadata
Keywords
Funding
Natural Environment Research Council Award: NE/P016502/1
Natural Environment Research Council Award: NE/P016472/1
Natural Environment Research Council Award: NE/L002558/1
Natural Environment Research Council Award: NE/R000131/1
Earth System Science Organization, Ministry of Earth Sciences (Government of India) Award: MoES/16/19/2017‑APHH
Natural Environment Research Council Award: NE/P016472/1
Natural Environment Research Council Award: NE/L002558/1
Natural Environment Research Council Award: NE/R000131/1
Earth System Science Organization, Ministry of Earth Sciences (Government of India) Award: MoES/16/19/2017‑APHH