About

Pierre Herckes is a professor in the School of Molecular Sciences at Arizona State University. His research interests focus on Atmospheric Chemistry, particularly aerosols and clouds, aerosol-cloud interactions, and their effects on air quality and climate. A significant portion of his work involves applied projects aimed at addressing real-world air pollution challenges. Additionally, he specializes in analytical chemistry, developing methods to investigate the sources, occurrence, and fate of environmental pollutants. His recent research has concentrated on detecting emerging contaminants such as nitrosamines and nanomaterials in environmental and biological samples, with a strong emphasis on applied projects related to water quality and human exposure. Dr. Herckes holds a degree in Chemical Engineering from EHICS Strasbourg and earned his MS and PhD degrees in Environmental Physical Chemistry from Strasbourg University in France. Prior to joining ASU, he was a postdoctoral researcher and research scientist in the Atmospheric Science Department at Colorado State University.

Research topics

• Materials science
• Nanotechnology
• Computer Science
• Optoelectronics
• Metallurgy
• Chemistry
• Engineering
• Process engineering
• Soil science
• Geology
• Composite material
• Environmental chemistry
• Medicine
• Chemical engineering
• Mineralogy
• Environmental science
• Waste management

Selected publications

• Characteristics of common ozone exceedance days across the U.S. Intermountain West

  Atmospheric Environment · 2026-03-30

  article
  PublisherDOI

• Temporal surveillance of Coccidioides in soils and aerosols at a single location in Arizona

  2026-03-13

  articleOpen access

  Valley fever is a lung infection caused by the inhalation of infectious spores from the fungi Coccidioides spp., a genus of soil dwelling fungal pathogen endemic to the arid regions of the southwestern United States, Mexico, Central and South America. Valley fever can exclusively be acquired through environmental reservoirs and is non-communicable from host to host. Very few Valley fever studies have focused on detecting Coccidioides spores in airborne respirable particles, which is the vector to infection. This study looks at the presence of Coccidioides in the air, soil, and burrow systems at a highly positive site in Mesa, Arizona. Monthly soil samples were taken from 14 animal burrows and 2 – 40 meter transects. Aerosol samples were collected for 24 hours every 6 days, following the Environmental Protection Agency sampling schedule. Two types of filter media were used for aerosol sampling: quartz fiber filters were used to determine gravimetric PM10, key ions, and organic and elemental carbon, and cellulose filters were used to analyze key elements. Meteorological data, including relative humidity, wind speeds, wind direction, and temperature were collected from a nearby weather station. Temporal soil sampling showed that C. posadasii stayed present at the site during the entire duration of the study however, temporal fluctuations of fungal burden occurred with decreases in detection occurring in the early spring and mid-summer months. Spatial variation was also detected, with certain burrow systems maintaining a high fungal burden throughout the year while others transiently housing the pathogen. We also showed that the pathogen was detected in rodent burrows significantly more frequency than in our surface soil transects. The temporal patterns of positivity for all the burrows were consistent over three years of sampling. Coccidioides were detected in ~68% of aerosol samples. Bulk PM10 did not have a statistically significant relationship with presence of Coccidioides, however, there was a statistically significant relationship between the amount of crustal material in the aerosols and presence of Coccidioides. Crustal material was reconstructed using the primary elements that make up earth’s crust (Al, Si, Fe, Ca, and Ti). Previous studies often link the presence of Coccidioides in the air with bulk PM10 concentrations; however, we found that looking at bulk PM10 concentrations gives an incomplete story. Additionally, there were statistically significant relationships with presence of Coccidioides and meteorological parameters, such as relative humidity and wind speed. This study emphasizes the importance of dust entrainment in the aerosolization and transport of Coccidioides.

  PublisherDOI

• Size-dependent carbon isotope signatures in urban aerosol: the influence of carbonate-rich dust in an arid city Phoenix (Arizona)

  Atmospheric Environment · 2026-05-01

  articleSenior author
  PublisherDOI

• Polycyclic aromatic hydrocarbons in PM2.5 and PM10 in Lagos, Nigeria: Sources, characteristics, and health risks

  Environmental Research · 2026-01-10 · 1 citations

  article
  PublisherDOI

• Growth and formaldehyde degradation of photoheterotrophic <i>Methylobacterium</i> within radiation fogs

  mBio · 2026-05-11

  articleOpen access

  ABSTRACT The atmosphere contains thousands to millions of bacterial cells per cubic meter. However, it remains unclear if microbes are at all active or growing in situ or whether they are merely being transported in an inactive state. Based on the analyses of 32 overland radiation fog events over a 2-year period, we show that fog waters, with bacterial concentrations similar to those in continental or marine bodies of water, contain microbiomes well differentiated in composition from those in the dry aerosol microbiomes that occur locally before, during, or after fog events. They are consistently and strongly enriched in photoheterotrophic Methylobacterium species, suggesting that fog populations may be metabolizing volatile C1 compounds in situ , although phototrophy seems much less important. Indeed, metabolically active bacteria in the fog, and representative isolates of the main field populations, can degrade formaldehyde at unprecedently high rates; most of this activity seems to play a detoxification role. The increase in bacterial aerobiome counts upon intervening fog events, the dependence of microbial concentration on ambient temperature, the increases in cell size and frequency of dividing cells in fog water with respect to cells in interstitial aerosols of fogs, in addition to their metabolic capacity, all suggest that the fog water microbiome is actually growing. Consequently, droplets of atmospheric water should be considered a potential aquatic microhabitat. Our results highlight the fog microbiome’s role in atmospheric chemistry and have implications for fog harvesting as a source of fresh water for human use. IMPORTANCE While bacteria are common in the atmosphere, their activity in situ has remained unclear. Using stagnant radiation fogs as new study systems where sampling is optimal, the dynamics, composition, cellular characteristics, and metabolic rates of fog water microbiomes, dominated by Methylobacterium sp., show that they are a hub of active detoxification of atmospheric formaldehyde and likely growing in situ on the basis of heterotrophic or photoheterotrophic metabolism of volatile C1 compounds, with implications for atmospheric chemistry and fog harvesting as sources of freshwater.

  PublisherDOI

• Abstract DP222: Microplastic Exposure Exacerbates Post-Stroke Depression and Memory Impairment

  Stroke · 2026-01-29

  article

  Introduction: Global plastic production and use continue to rise, with significant human health concerns. Once released into the natural environment, plastics degrade into microplastics, which can enter the human body primarily via ingestion. A recent clinical study reported that over 50% of patients undergoing carotid endarterectomy had detectable microplastics in their specimens, and their presence was associated with worse cardiovascular and cerebrovascular outcomes. However, causal links remain unclear. We compared long-term functional outcomes after acute ischemic stroke in mice with and without chronic exposure to microplastics using the middle cerebral artery occlusion model. Methods: 12-week-old male C57BL/6J mice (N = 48) were exposed to polyethylene (150 mg/kg/day), the most common polymer found in the environment and human tissues, or to vehicle for 5 weeks before stroke. Overall neurological deficit was assessed on day 28 post-stroke using the Garcia score. Cognitive and affective behaviors were evaluated with the nestlet test, elevated plus maze, open field test, and Morris water maze. To explore mechanisms, RNA sequencing of the ipsilateral hemisphere was performed on day 3 post-stroke. Results: Mice exposed to microplastics showed significantly worse Garcia score than vehicle controls ( P &lt; 0.001; Fig. A ). Mice exposed to microplastics also had lower nestlet test scores, indicating reduced general behavior and well-being, presumably due to aggravated post-stroke depression ( P &lt; 0.01; Fig. B ). In the elevated plus maze, mice exposed to microplastics spent less time in open arms and more time in closed arms, suggesting higher post-stroke depression ( P &lt; 0.05, respectively; Figs. C–D ). Open field testing showed fewer entries into the center zone in mice exposed to microplastics, again indicating greater post-stroke depression ( P &lt; 0.05; Fig. E ). In the Morris water maze, mice exposed to microplastics exhibited longer time and distance to reach the hidden platform, indicating greater post-stroke memory impairment ( P &lt; 0.01, respectively; Figs. F–I ); the probe trial corroborated these deficits ( P &lt; 0.05; Fig. J ). RNA sequencing revealed upregulation of pro-inflammatory genes and downregulation of genes related to neurotransmission and synaptic function in mice exposed to microplastics. Conclusions: Chronic exposure to microplastics worsens long-term neurological outcomes after stroke, exacerbating post-stroke depression and memory impairment.

  PublisherDOI

• Supplementary material to "Contrasting solubility and speciation of metal ions in total suspended particulate matter and fog from the coast of Namibia"

  2025-01-23

  preprintOpen access
  PublisherDOI

• Elemental and morphological diversity of individual magnetic particles from urban surfaces: implications for adverse health outcomes

  Environmental Science Nano · 2025-01-01 · 1 citations

  article

  Integrating spICP-TOFMS and STEM-EDX enables comprehensive single-particle analysis of urban magnetic dust particles, revealing their heterogeneous composition, trace metal co-occurrence, and potential health implications.

  PublisherDOI

• Temporal surveillance of <i>Coccidioides</i> in Aerosols in Mesa, Arizona

  Environmental Science & Technology Letters · 2025-10-20 · 1 citations

  article

  Valley fever is a lung infection caused by the inhalation of infectious spores from the fungus Coccidioides spp. Coccidioides is a genus of soil dwelling fungi endemic to the arid regions of the southwestern United States, Mexico, and Central and South America. Few Valley fever studies have focused on detecting Coccidioides spores in airborne respirable particles, which is the primary infection vector. This study looks at the presence of Coccidioides in air at a highly soil positive site in Mesa, Arizona. Aerosol samples were collected for 24 h every 6 days, following the Environmental Protection Agency sampling schedule. Meteorological data were collected from a nearby weather station. Coccidioides were detected in ∼68% of the aerosol samples. Bulk PM10 did not have a statistically significant relationship with presence of Coccidioides; however, there was a significant relationship between the amount of crustal material in the aerosols and presence of Coccidioides. Previous studies link the presence of Coccidioides in air with bulk PM10 concentrations; however, we found that bulk PM10 concentrations give an incomplete story. Additionally, there were statistically significant relationships with the presence of Coccidioides and meteorological parameters, including relative humidity, temperature, and wind speed. This study emphasizes the importance of dust entrainment in the transmission of Coccidioides.

  PublisherDOI

• Contrasting solubility and speciation of metal ions in total suspended particulate matter and fog from the coast of Namibia – Part 1

  Atmospheric chemistry and physics · 2025-11-19 · 1 citations

  articleOpen accessCorresponding

  Abstract. The western coast of southern Africa is a region of particular climate interest and crossroads for aerosols of different origins as well as fog occurrences. In this study, we present a comparison between the concentration of dissolved trace metals in pairs of total suspended particulate (TSP) and fog water samples collected in Henties Bay, Namibia, during the AErosols, Radiation and CLOuds in southern Africa (AEROCLO-sA) field campaign in September 2017. From inductively coupled plasma mass spectrometry measurements, we found that the concentration of dissolved Al, Fe, Ni, Cu, and Cr is enhanced in fog samples compared to the TSP samples. We found that thermodynamic modelling predicts the formation of soluble complexes with inorganic and organic ligands in fog for Cu, Cr, and Ni, but it would predict Al and Fe to precipitate as hydroxides given the neutral pH of fog. In contrast, X-ray absorption near edge structure measurements showed the presence of oxalate of Fe complexes that could explain its enhanced dissolved concentration in fog samples, despite a neutral pH. In addition, transmission electron microscopy and dynamic light scattering measurements revealed the presence of nano-sized colloidal particles containing Fe and Al in filtered fog samples that may appear soluble in inductively coupled plasma mass spectrometer (ICP-MS) measurements. We hypothesise that these complexes are formed in the early stages of particle activation into droplets when water content and, therefore, pH are expected to be lower and then remain in fog in a kinetically stable form or lead to the formation of colloidal nanoparticles.

  PublisherOA PDFDOI

Recent grants

• CAREER: Cloud and Fog Processing of Organic Matter

  NSF · $569k · 2009–2014

• Collaborative Research: Atmospheric Processing of Iron--Does Particle Size Influence Iron Solubility?

  NSF · $220k · 2010–2014

Frequent coauthors

• Paul Westerhoff

  Arizona State University

  86 shared

• Jeffrey L. Collett

  42 shared

• Barbara Ervens

  Centre National de la Recherche Scientifique

  30 shared

• Matthew P. Fraser

  Arizona State University

  29 shared

• J. W. Hutchings

  26 shared

• D. Straub

  Susquehanna University

  21 shared

• David Hanigan

  University of Nevada, Reno

  17 shared

• Nabin Upadhyay

  Arizona State University

  14 shared

Education

• Ph.D., Environmental Physical Chemistry

  Louis Pasteur University

  1999

• M.S., Environmental Physical Chemistry

  Strasbourg University

• B.S., Chemical Engineering

  EHICS Strasbourg