About

Donald R. Blake is a Distinguished Professor at the University of California, Irvine, within the Department of Chemistry. His research interests focus on analytical atmospheric and environmental chemistry. He is associated with the UC Irvine School of Physical Sciences and is involved in advancing understanding in these scientific areas through his academic and research activities.

Research topics

• Environmental science
• Meteorology
• Atmospheric sciences
• Chemistry
• Geology
• Geography
• Environmental chemistry
• Climatology
• Organic chemistry
• Oceanography
• Chromatography
• Physics
• Computer Science
• Telecommunications
• Ecology
• Photochemistry

Selected publications

• Diurnal Trends Differentiate Anthropogenic and Biogenic Terpenes in the Los Angeles Basin

  2025-05-15 · 1 citations

  preprintOpen access

  Terpenoids play a significant role in the formation of tropospheric ozone (O3) and secondary organic aerosol (SOA). While terpenoids are largely attributed to biogenic sources, they are also widely used in consumer products that end up in the atmosphere. Terpenoid mixing ratios are reported here from samples collected during the Los Angeles Air Quality Campaign (LAAQC) in 2022 and were compared with data from three other campaigns in the LA Basin conducted between 2010 and 2021. Across all campaigns, differences in diurnal mixing ratios and composition suggest anthropogenic sources are predominant contributors to terpenoid mixing ratios in the evening to early morning (22:00 – 6:00 PDT), shifting to predominately biogenic sources in the afternoon (10:00 – 18:00 PDT). This manuscript presents the first evidence for a significant presence of anthropogenic terpenoids in the LA Basin and highlights the need for systematically studying anthropogenic and biogenic terpenoid emissions in urban areas.

  PublisherOA PDFDOI

• Characteristics of atmospheric CH4, CO2 and CO at a suburban coastal site in Hong Kong

  Atmospheric Environment · 2025-10-22

  articleSenior author
  PublisherDOI

• Spatial and temporal variation in coal fire emissions: Examples from two eastern Kentucky coal fires

  International Journal of Coal Geology · 2025-02-17

  article1st author
  PublisherDOI

• Investigating fire-induced ozone production from local to global scales

  Atmospheric chemistry and physics · 2025-11-28 · 2 citations

  articleOpen accessCorresponding

  Abstract. Tropospheric ozone (O3) production from wildfires is highly uncertain; previous studies have identified both production and loss of O3 in fire-influenced air masses. To capture the total ozone production attributable to a smoke plume, we bridge the gap between near-field fire plume chemistry and aged smoke in the remote troposphere. Using airborne measurements from several major campaigns, we find that fire-ozone production increases with age, with a regime transition from NOx-saturated to NOx-limited conditions, showing that O3 production in well-aged plumes is largely controlled by nitrogen oxides (NOx). Observations in fresh smoke demonstrate that suppressed photochemistry reduces O3 production by ∼ 70 % in units of ppb Ox (O3 + NO2) per ppm CO in the near-field (age < 20 h). We demonstrate that anthropogenic NOx injection into VOC-rich fire plumes drives additional O3 production, sometimes exceeding 50 ppb above background. Using a box model, we explore the evolving sensitivity of O3 production to fire emissions and chemical parameters. We demonstrate the importance of aerosol-induced photochemical suppression over heterogeneous HO2 uptake, validate HONO's importance as an oxidant precursor, and confirm evolving NOx sensitivity. We evaluate GEOS-Chem's performance against these observations, finding the model captures fire-induced O3 enhancements at older ages but overestimates near-field enhancements, fails to capture the magnitude and variability of fire emissions, and does not capture the chemical regime transition. These discrepancies drive biases in normalized ozone production (ΔO3/ΔCO) across plume lifetime, though the model generally captures observed absolute O3 enhancements in fire plumes. GEOS-Chem attributes 2.4 % of the global tropospheric ozone burden and 3.1 % of surface ozone concentrations to fire emissions in 2020, with stronger impacts in regions of frequent burning.

  PublisherOA PDFDOI

• The Mental Health of Farmers and Farmworkers Impacted by Flooding and Drought in England

  European Journal of Public Health · 2025-10-01

  articleOpen access1st authorCorresponding

  Abstract Background Farmers and farmworkers are particularly vulnerable to the mental health impacts of environmental stressors such as flooding and drought. While studies from countries like Australia have explored this, there is a critical gap in understanding these effects in farming communities elsewhere, including England-especially as such events increase with climate change. This study investigates how flooding and drought affect the mental health and wellbeing of farmers and farmworkers in England, examining impacts on livelihoods and exploring both risk and protective factors. Methods A mixed-methods approach was used, beginning with a national online survey distributed through agricultural organisations in early 2025. Mental wellbeing was assessed using the Warwick-Edinburgh Mental Wellbeing Scale (WEMWBS). Thematic analysis was applied to survey responses to identify key patterns in mental health challenges, coping strategies, and resilience. A subset of respondents will be invited for follow-up semi-structured interviews to gather deeper qualitative insights. Results The survey received 94 complete responses, representing every region of England and a variety of farm types. Results reveal a high prevalence of mental health issues among respondents, with limited professional help-seeking. Support from family and friends emerged as central to coping, alongside specific personal strategies. The national government was often cited as having a role in supporting mental health in relation to climate-related impacts. Conclusions This study underscores the importance of considering local and national contexts when addressing the mental health impacts of flooding and drought on farming communities. Findings will inform targeted health protection interventions and contribute to international research on the mental health effects of climate change.

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• Trends in CH ₄ Emission Sources in the Los Angeles Basin from 2010 to 2023 Using Airborne Measurements

  Environmental Science & Technology · 2025-11-29 · 1 citations

  article

  emission reduction goals.

  PublisherDOI

• Global methane budget 2000--2020

  ENLIGHTEN (Jurnal Bimbingan dan Konseling Islam) · 2025-05-09 · 218 citations

  articleOpen access

  Understanding and quantifying the global methane (CH4) budget is important for assessing realistic pathways to mitigate climate change. CH4 is the second most important human-influenced greenhouse gas in terms of climate forcing after carbon dioxide (CO2), and both emissions and atmospheric concentrations of CH4 have continued to increase since 2007 after a temporary pause. The relative importance of CH4 emissions compared to those of CO2 for temperature change is related to its shorter atmospheric lifetime, stronger radiative effect, and acceleration in atmospheric growth rate over the past decade, the causes of which are still debated. Two major challenges in quantifying the factors responsible for the observed atmospheric growth rate arise from diverse, geographically overlapping CH4 sources and from the uncertain magnitude and temporal change in the destruction of CH4 by short-lived and highly variable hydroxyl radicals (OH). To address these challenges, we have established a consortium of multidisciplinary scientists under the umbrella of the Global Carbon Project to improve, synthesise, and update the global CH4 budget regularly and to stimulate new research on the methane cycle. Following Saunois et al. (2016, 2020), we present here the third version of the living review paper dedicated to the decadal CH4 budget, integrating results of top-down CH4 emission estimates (based on in situ and Greenhouse Gases Observing SATellite (GOSAT) atmospheric observations and an ensemble of atmospheric inverse-model results) and bottom-up estimates (based on process-based models for estimating land surface emissions and atmospheric chemistry, inventories of anthropogenic emissions, and data-driven extrapolations). We present a budget for the most recent 2010–2019 calendar decade (the latest period for which full data sets are available), for the previous decade of 2000–2009 and for the year 2020. The revision of the bottom-up budget in this 2025 edition benefits from important progress in estimating inland freshwater emissions, with better counting of emissions from lakes and ponds, reservoirs, and streams and rivers. This budget also reduces double counting across freshwater and wetland emissions and, for the first time, includes an estimate of the potential double counting that may exist (average of 23 Tg CH4 yr−1). Bottom-up approaches show that the combined wetland and inland freshwater emissions average 248 [159–369] Tg CH4 yr−1 for the 2010–2019 decade. Natural fluxes are perturbed by human activities through climate, eutrophication, and land use. In this budget, we also estimate, for the first time, this anthropogenic component contributing to wetland and inland freshwater emissions. Newly available gridded products also allowed us to derive an almost complete latitudinal and regional budget based on bottom-up approaches. For the 2010–2019 decade, global CH4 emissions are estimated by atmospheric inversions (top-down) to be 575 Tg CH4 yr−1 (range 553–586, corresponding to the minimum and maximum estimates of the model ensemble). Of this amount, 369 Tg CH4 yr−1 or ∼ 65 % is attributed to direct anthropogenic sources in the fossil, agriculture, and waste and anthropogenic biomass burning (range 350–391 Tg CH4 yr−1 or 63 %–68 %). For the 2000–2009 period, the atmospheric inversions give a slightly lower total emission than for 2010–2019, by 32 Tg CH4 yr−1 (range 9–40). The 2020 emission rate is the highest of the period and reaches 608 Tg CH4 yr−1 (range 581–627), which is 12 % higher than the average emissions in the 2000s. Since 2012, global direct anthropogenic CH4 emission trends have been tracking scenarios that assume no or minimal climate mitigation policies proposed by the Intergovernmental Panel on Climate Change (shared socio-economic pathways SSP5 and SSP3). Bottom-up methods suggest 16 % (94 Tg CH4 yr−1) larger global emissions (669 Tg CH4 yr−1, range 512–849) than top-down inversion methods for the 2010–2019 period. The discrepancy between the bottom-up and the top-down budgets has been greatly reduced compared to the previous differences (167 and 156 Tg CH4 yr−1 in Saunois et al. (2016, 2020) respectively), and for the first time uncertainties in bottom-up and top-down budgets overlap. Although differences have been reduced between inversions and bottom-up, the most important source of uncertainty in the global CH4 budget is still attributable to natural emissions, especially those from wetlands and inland freshwaters. The tropospheric loss of methane, as the main contributor to methane lifetime, has been estimated at 563 [510–663] Tg CH4 yr−1 based on chemistry–climate models. These values are slightly larger than for 2000–2009 due to the impact of the rise in atmospheric methane and remaining large uncertainty (∼ 25 %). The total sink of CH4 is estimated at 633 [507–796] Tg CH4 yr−1 by the bottom-up approaches and at 554 [550–567] Tg CH4 yr−1 by top-down approaches. However, most of the top-down models use the same OH distribution, which introduces less uncertainty to the global budget than is likely justified. For 2010–2019, agriculture and waste contributed an estimated 228 [213–242] Tg CH4 yr−1 in the top-down budget and 211 [195–231] Tg CH4 yr−1 in the bottom-up budget. Fossil fuel emissions contributed 115 [100–124] Tg CH4 yr−1 in the top-down budget and 120 [117–125] Tg CH4 yr−1 in the bottom-up budget. Biomass and biofuel burning contributed 27 [26–27] Tg CH4 yr−1 in the top-down budget and 28 [21–39] Tg CH4 yr−1 in the bottom-up budget. We identify five major priorities for improving the CH4 budget: (i) producing a global, high-resolution map of water-saturated soils and inundated areas emitting CH4 based on a robust classification of different types of emitting ecosystems; (ii) further development of process-based models for inland-water emissions; (iii) intensification of CH4 observations at local (e.g. FLUXNET-CH4 measurements, urban-scale monitoring, satellite imagery with pointing capabilities) to regional scales (surface networks and global remote sensing measurements from satellites) to constrain both bottom-up models and atmospheric inversions; (iv) improvements of transport models and the representation of photochemical sinks in top-down inversions; and (v) integration of 3D variational inversion systems using isotopic and/or co-emitted species such as ethane as well as information in the bottom-up inventories on anthropogenic super-emitters detected by remote sensing (mainly oil and gas sector but also coal, agriculture, and landfills) to improve source partitioning.

  PublisherDOI

• Investigating fire-induced ozone production from local to global scales

  2025-05-13

  preprintOpen access

  Abstract. Tropospheric ozone (O3) production from wildfires is highly uncertain; previous studies have identified both production and loss of O3 in fire-influenced air masses. To capture the total ozone production attributable to a smoke plume, we bridge the gap between near-field fire chemistry and aged smoke in the remote troposphere. Using airborne measurements from several campaigns, we find that fire-ozone production increases with age, with a regime transition from NOx-saturated to NOx-limited conditions, showing that O3 production in aged plumes is controlled by nitrogen oxides (NOx). Observations in fresh smoke show that suppressed photochemistry reduces O3 production by ~70% in units of ppb Ox per ppm CO. Anthropogenic NOx injection into VOC-rich fire plumes drives additional O3 production, exceeding 50 ppb above background in extreme cases. Using a box model, we explore the sensitivity of O3 production to fire emissions and chemical parameters, demonstrating the importance of aerosol-induced photochemical suppression over heterogeneous HO₂ uptake, validating HONO's role as an oxidant precursor, and confirming evolving NOx sensitivity. We evaluate GEOS-Chem's performance against these observations, finding that the model captures fire-induced O3 enhancements at older ages but overestimates near-field enhancements, fails to capture fire emission magnitude and variability, and misses the chemical regime transition. These discrepancies bias normalized ozone production (∆O3/∆CO) across plume lifetime. GEOS-Chem attributes 2.4% of the global tropospheric ozone burden and 3.1% of surface ozone concentrations to fire emissions in 2020, with stronger impacts in regions of frequent burning.

  PublisherOA PDFDOI

• Supplementary material to "Investigating fire-induced ozone production from local to global scales"

  2025-05-13

  preprintOpen access
  PublisherDOI

• Widespread trace bromine and iodine in remote tropospheric non-sea-salt aerosols

  Atmospheric chemistry and physics · 2025-01-06 · 6 citations

  articleOpen access

  Abstract. Reactive halogens catalytically destroy O3 and therefore affect (1) stratospheric O3 depletion and (2) the oxidative capacity of the troposphere. Reactive halogens also partition into the aerosol phase, but what governs halogen-aerosol partitioning is poorly constrained in models. In this work, we present global-scale measurements of non-sea-salt aerosol (nSSA) bromine and iodine taken during the NASA Atmospheric Tomography Mission (ATom). Using the Particle Analysis by Laser Mass Spectrometry instrument, we found that bromine and iodine are present in 8 %–26 % (interquartile range, IQR) and 12 %–44 % (IQR) of accumulation-mode nSSA, respectively. Despite being commonly found in nSSA, the concentrations of bromine and iodine in nSSA were low but potentially important, at 0.11–0.57 pmol mol−1 (IQR) and 0.04–0.24 pmol mol−1 (IQR), respectively. In the troposphere, we find two distinct sources of bromine and iodine for nSSA: (1) a primary source from biomass burning and (2) a pervasive secondary source. In the stratosphere, nSSA bromine and iodine concentrations increased with increasing O3 concentrations; however, higher concentrations of stratospheric nSSA bromine and iodine were found in organic-rich particles that originated in the troposphere. Finally, we compared our ATom nSSA iodine measurements to the global chemical transport model GEOS-Chem (Goddard Earth Observing System); nSSA bromine concentrations could not be compared because they were not tracked in the model. We found that the model compared well to our ATom nSSA iodine measurements in the background atmosphere but not in the marine boundary layer, biomass burning plumes, or stratosphere.

  PublisherDOI

Recent grants

• RAPID: Examining the relation between trace gas emissions and seismic activity of the 2019 Searles Valley Earthquake

  NSF · $200k · 2019–2023

• Collaborative Research: Organic Trace Gas Studies from Whole-Air Sampling of the Impact of Megacities and Intercontinental Transport on Regional and Global Environments

  NSF · $676k · 2005–2008

• RAPID: Chemical Analysis of Atmosphere Associated with Gulf Oil Spill

  NSF · $93k · 2010–2011

Frequent coauthors

• G. W. Sachse

  Langley Research Center

  591 shared

• H. B. Singh

  National Institute of Technology Delhi

  567 shared

• R. W. Talbot

  University of Colorado Denver

  487 shared

• Brian G. Heikes

  University of Rhode Island

  486 shared

• J. D. Bradshaw

  Wake Forest University

  477 shared

• S. T. Sandholm

  University of North Dakota

  452 shared

• G. L. Gregory

  377 shared

• N. J. Blake

  University of California, Irvine

  371 shared

Education

• Professor, Chemistry

  University of California Irvine