Alireza Namayandeh
Postdoctoral Scholar, Earth System Science
Bio
Alireza Namayandeh is an NSF Earth Science Postdoctoral Fellow at the Doerr School of Sustainability at Stanford University. He is interested in understanding the formation, transformation, and environmental impacts of metal-bearing nanoparticles in soil, water, and air, particularly their role in transporting toxic metals and influencing human and ecosystem health. His current research focuses on how biomass burning during wildfires generates toxic metal nanoparticles and affects their chemical and physical properties in soil and air.
Prior to joining Stanford, he conducted research in geochemistry, mineralogy, and nanoscience at Virginia Tech, where he earned his Ph.D. in Environmental Geochemistry. His doctoral work examined the formation and transformation of iron oxy-hydroxide nanoparticles and their interactions with environmental contaminants such as arsenic, phosphate, and nitrate. A key focus of his research was the identification and characterization of ultrasmall (~1 nm) precursor clusters that serve as building blocks for metal nanoparticles like ferrihydrite. His work provided the first direct structural evidence for the formation of these clusters, revealing their role in contaminant transport and metal mobility in natural environments. By integrating synchrotron X-ray techniques, electron microscopy, and in situ laboratory experiments, he demonstrated how these clusters remain suspended in water and air, enhancing the long-range dispersion of toxic metals.
More recently, his research has expanded to investigate the role of wildfires in mobilizing toxic metal nanoparticles, particularly through airborne particulate matter. His studies have shown that wildfire smoke contains a significant fraction of ultrafine metal-bearing nanoparticles that can be transported over long distances and pose severe health risks. By analyzing wildfire smoke samples from major fires across the Western U.S. and conducting controlled burning experiments, he is working to quantify the mechanisms by which toxic metal nanoparticles are generated, transported, and deposited into ecosystems. As part of this work, he is leading efforts to assess toxic metal nanoparticles in smoke, ash, and debris from the Eaton and Palisade wildfires in Los Angeles, studying their potential for airborne transport and human exposure. His goal is to apply these findings to inform wildfire mitigation strategies and public health policies, addressing the increasing risks posed by climate-driven wildfires in the US.
Honors & Awards
-
NSF Earth Science Postdoctoral Fellow, National Science Foundation (NSF) (2024-2026)
-
PRISM Baker Fellowship, Stanford University (2022-2023)
-
Interdisciplinary Graduate Education Fellowship, Virginia Tech (2021-2022)
-
Interdisciplinary Graduate Education Fellowship, Virginia Tech (2018-2019)
Current Research and Scholarly Interests
Alireza Namayandeh’s research focuses on the formation, transformation, and environmental impacts of metal-bearing nanoparticles in soil, water, and air, with a particular emphasis on their role in wildfire-generated pollution. His work investigates how wildfires contribute to the release and transport of toxic metal nanoparticles, assessing their chemical and physical properties and their implications for human health and ecosystem contamination.
His current research, supported by the NSF Earth Science Postdoctoral Fellowship, explores the mechanisms by which biomass burning generates toxic airborne nanoparticles and how soil mineralogy influences their formation. By combining laboratory experiments, synchrotron-based spectroscopy, electron microscopy, and field studies, he aims to better understand the pathways of metal mobilization during wildfires. He is also leading efforts to analyze ash and soil samples from recent wildfires in California, including the Eaton and Palisade fires in Los Angeles, to assess the risks associated with airborne metal nanoparticles.
Beyond wildfire-driven pollution, he is interested in the fundamental geochemistry of nanoparticle formation and transport. His previous work on precursor clusters of iron oxy-hydroxides provided new insights into the formation of metal-bearing nanoparticles and their role in controlling contaminant mobility in the environment. He continues to explore how ultrafine particles interact with toxic metals, organic matter, and microbial communities in both terrestrial and atmospheric systems.
His broader scholarly interests include wildfire geochemistry, atmospheric particulate matter, environmental mineralogy, and the intersection of environmental geochemistry and public health. His goal is to develop a deeper understanding of how natural and anthropogenic processes influence the formation and dispersion of hazardous nanoparticles, ultimately contributing to improved air quality standards, risk assessment models, and environmental policies in wildfire-prone regions.
All Publications
-
Goethite and Hematite Nucleation and Growth from Ferrihydrite: Effects of Oxyanion Surface Complexes.
Environmental science & technology
2024
Abstract
The presence of oxyanions, such as nitrate (NO3-) and phosphate (PO43-), regulates the nucleation and growth of goethite (Gt) and hematite (Hm) during the transformation of ferrihydrite (Fh). Our previous studies showed that oxyanion surface complexes control the rate and pathway of Fh transformation to Gt and Hm. However, how oxyanion surface complexes control the mechanism of Gt and Hm nucleation and growth during the Fh transformation is still unclear. We used synchrotron scattering methods and cryogenic transmission electron microscopy to investigate the effects of NO3- outer-sphere complexes and PO43- inner-sphere complexes on the mechanism of Gt and Hm formation from Fh. Our TEM results indicated that Gt particles form through a two-step model in which Fh particles first transform to Gt nanoparticles and then crystallographically align and grow to larger particles by oriented attachment (OA). In contrast, for the formation of Hm, imaging shows that Fh particles first aggregate and then transform to Hm through interface nucleation. This is consistent with our X-ray scattering results, which demonstrate that NO3- outer-sphere and PO43- inner-sphere complexes promote the formation of Gt and Hm, respectively. These results have implications for understanding the coupled interactions of oxyanions and iron oxy-hydroxides in Earth-surface environments.
View details for DOI 10.1021/acs.est.3c09955
View details for PubMedID 38506754
-
Effects of Oxyanion Surface Loading on the Rate and Pathway of Ferrihydrite Transformation
ACS EARTH AND SPACE CHEMISTRY
2023
View details for DOI 10.1021/acsearthspacechem.3c00232
View details for Web of Science ID 001072584400001
-
Oxyanion Surface Complexes Control the Kinetics and Pathway of Ferrihydrite Transformation to Goethite and Hematite.
Environmental science & technology
2022
Abstract
The rate and pathway of ferrihydrite (Fh) transformation at oxic conditions to more stable products is controlled largely by temperature, pH, and the presence of other ions in the system such as nitrate (NO3-), sulfate (SO42-), and arsenate (AsO43-). Although the mechanism of Fh transformation and oxyanion complexation have been separately studied, the effect of surface complex type and strength on the rate and pathway remains only partly understood. We have developed a kinetic model that describes the effects of surface complex type and strength on Fh transformation to goethite (Gt) and hematite (Hm). Two sets of oxyanion-adsorbed Fh samples were prepared, nonbuffered and buffered, aged at 70 ± 1.5 °C, and then characterized using synchrotron X-ray scattering methods and wet chemical analysis. Kinetic modeling showed a significant decrease in the rate of Fh transformation for oxyanion surface complexes dominated by strong inner-sphere (SO42- and AsO43-) versus weak outer-sphere (NO3-) bonding and the control. The results also showed that the Fh transformation pathway is influenced by the type of surface complex such that with increasing strength of bonding, a smaller fraction of Gt forms compared with Hm. These findings are important for understanding and predicting the role of Fh in controlling the transport and fate of metal and metalloid oxyanions in natural and applied systems.
View details for DOI 10.1021/acs.est.2c04971
View details for PubMedID 36219790
-
TRACE AND RARE EARTH ELEMENT DISTRIBUTION AND MOBILITY DURING DIAGENETIC ALTERATION OF VOLCANIC ASH TO BENTONITE IN EASTERN IRANIAN BENTONITE DEPOSITS
CLAYS AND CLAY MINERALS
2020; 68 (1): 50-66
View details for DOI 10.1007/s42860-019-00054-9
View details for Web of Science ID 000531150400005
-
Calorimetric study of the influence of aluminum substitution in ferrihydrite on sulfate adsorption and reversibility
JOURNAL OF COLLOID AND INTERFACE SCIENCE
2019; 540: 20-29
Abstract
Ferrihydrite (Fh) is a nanocrystalline iron (hydr)oxide pervasive in various surface environments. It has high specific surface areas and high density of reactive surface-sites, both of which properties impart a consequential role in determining the fate and transport of environmental nutrients and contaminants. In natural environments, Fh readily reacts with impurities, such as aluminum (Al) and has variable substituted chemical compositions and surface properties. This work examines the effect of aluminum (Al) incorporation (0%, 12% and 24 mol% Al) on the interaction energy of chloride (Cl-) and nitrate (NO3-), and adsorption/desorption of sulfate (SO42-) onto Fh. Microcalorimetry experiments were conducted at pHs 3.0 and 5.6, along with a detailed characterization of all samples. Results showed a significant increase in the energetics of the exothermic peak of NO3- and the endothermic peak of Cl- with increasing Al concentration and decreasing pH values. Furthermore, the exothermic heat of exchange, adsorption, irreversibility and fraction of inner-sphere complexes for sulfate interaction with Fh increased with more Al concentration and acidic pH.
View details for DOI 10.1016/j.jcis.2019.01.001
View details for Web of Science ID 000460710800003
View details for PubMedID 30622055
-
Genesis of the Eastern Iranian bentonite deposits
APPLIED CLAY SCIENCE
2019; 168: 56-67
View details for DOI 10.1016/j.clay.2018.10.011
View details for Web of Science ID 000455692700008
-
Characterization of Iranian bentonites to be used as pharmaceutical materials
APPLIED CLAY SCIENCE
2015; 116: 193-201
View details for DOI 10.1016/j.clay.2015.03.013
View details for Web of Science ID 000361864300023