Publications de Kalliopi Violaki

Atmospheric reactive nitrogen and its dry deposition regimes under anthropogenic influence: Insights from intensive and long-term monitoring in Switzerland

Athanasios Nenes, Kalliopi Violaki, Ghislain Gilles Jean-Michel Motos, Andrea Baccarini

Excessive nitrogen deposition from anthropogenic activities poses significant challenges to ecosystems and air quality.1 The atmospheric deposition of ammonium and nitrate plays a critical role in regulating ecosystem productivity and driving particulate m ...

2025

Comparative characterization of bronchial and nasal mucus reveals key determinants of influenza A virus inhibition

Tamar Kohn, Céline Terrettaz, Aline Laetitia Schaub, Athanasios Nenes, Kalliopi Violaki, Ghislain Gilles Jean-Michel Motos, Walter Hugentobler

Differentiated primary human respiratory epithelial cells grown at air-liquid interface have become a widely used cell culture model of the human conducting airways. These cultures contain secretory cells such as goblet and club cells, which produce and se ...

American Society for Microbiology2025

Solid-state 31P NMR reveals the biological organophosphorus compounds as the dominant phosphorus species in Saharan dust aerosols

Pierre Rossi, Claudia Esther Avalos, Athanasios Nenes, Kalliopi Violaki, Christos Panagiotopoulos

Phosphorus is a critical nutrient affecting primary productivity across all ecosystems. Many regions worldwide are limited or co-limited by phosphorus availability, which can be alleviated through atmospheric deposition. Dust is known to be a key external ...

2025

Phosphorus speciation in environmental organic matter using 31P-NMR. Recent advances in the characterization of atmospheric organic matter

Athanasios Nenes, Kalliopi Violaki, Christos Panagiotopoulos

Phosphorus (P) is a vital element for all living organisms and is one of the most essential nutrients in both aquatic and terrestrial ecosystems. As a fundamental component of DNA and RNA, it plays a structural role in cell membranes (e.g., as part of phos ...

2025

Stability of influenza A virus in droplets and aerosols is heightened by the presence of commensal respiratory bacteria

Tamar Kohn, Htet Kyi Wynn, Céline Terrettaz, Aline Laetitia Schaub, Athanasios Nenes, Kalliopi Violaki, Marta Augugliaro, Shannon Christa David, Ghislain Gilles Jean-Michel Motos, Walter Hugentobler, Laura José Costa Henriques, Daniel Scott Nolan

Aerosol transmission remains a major challenge for control of respiratory viruses, particularly those causing recurrent epidemics, like influenza A virus (IAV). These viruses are rarely expelled alone, but instead are embedded in a consortium of microorgan ...

American Society for Microbiology2024

Dependence of aerosol-borne influenza A virus infectivity on relative humidity and aerosol composition

Tamar Kohn, Céline Terrettaz, Aline Laetitia Schaub, Athanasios Nenes, Kalliopi Violaki, Shannon Christa David, Ghislain Gilles Jean-Michel Motos, Walter Hugentobler, Laura José Costa Henriques

We describe a novel biosafety aerosol chamber equipped with state-of-theart instrumentation for bubble-bursting aerosol generation, size distribution measurement, and condensation-growth collection to minimize sampling artifacts when measuring virus infect ...

Frontiers Media SA2024

Salt Supersaturation as an Accelerator of Influenza A Virus Inactivation in 1 μL Droplets

Tamar Kohn, Céline Terrettaz, Athanasios Nenes, Kalliopi Violaki, Ghislain Gilles Jean-Michel Motos, Walter Hugentobler, Laura José Costa Henriques

Influenza A virus (IAV) spreads through exhaled aerosol particles and larger droplets. Estimating the stability of IAV is challenging and depends on factors such as the respiratory matrix and drying kinetics. Here, we combine kinetic experiments on millime ...

2024

Drivers of droplet formation in east Mediterranean orographic clouds

Kalliopi Violaki, Ghislain Gilles Jean-Michel Motos, Kunfeng Gao

The purpose of this study is to understand the drivers of cloud droplet formation in orographic clouds. We used a combination of modeling, in situ, and remote sensing measurements at the high-Altitude Helmos Hellenic Atmospheric Aerosol and Climate Change ...

Copernicus Publications2024

Impact of organic compounds on the stability of influenza A virus in deposited 1-μL droplets

Tamar Kohn, Céline Terrettaz, Aline Laetitia Schaub, Athanasios Nenes, Kalliopi Violaki, Shannon Christa David, Ghislain Gilles Jean-Michel Motos, Walter Hugentobler

The composition of respiratory fluids influences the stability of viruses in exhaled aerosol particles and droplets, though the role of respiratory organics in modulating virus stability remains poorly understood. This study investigates the effect of orga ...

2024

Inactivation mechanisms of influenza A virus under pH conditions encountered in aerosol particles as revealed by whole-virus HDX-MS

Tamar Kohn, Jonathan Paz Montoya, Aline Laetitia Schaub, Athanasios Nenes, Giovanni D'Angelo, Kalliopi Violaki, Shannon Christa David, Ghislain Gilles Jean-Michel Motos, Walter Hugentobler

Multiple respiratory viruses, including influenza A virus (IAV), can be transmitted via expiratory aerosol particles, and aerosol pH was recently identified as a major factor influencing airborne virus infectivity. Indoors, small exhaled aerosols undergo r ...

2023

Expiratory Aerosol pH: The Overlooked Driver of Airborne Virus Inactivation

Tamar Kohn, Aline Laetitia Schaub, Athanasios Nenes, Kalliopi Violaki, Shannon Christa David, Ghislain Gilles Jean-Michel Motos, Walter Hugentobler

Respiratory viruses, including influenza virus and SARS-CoV-2, are transmitted by the airborne route. Air filtration and ventilation mechanically reduce the concentration of airborne viruses and are necessary tools for disease mitigation. However, they ign ...

2023

Expiratory aerosol pH is determined by indoor room trace gases and particle size

Tamar Kohn, Aline Laetitia Schaub, Athanasios Nenes, Kalliopi Violaki, Shannon Christa David, Ghislain Gilles Jean-Michel Motos, Walter Hugentobler

2022

Water soluble reactive phosphate (SRP) in atmospheric particles over East Mediterranean: The importance of dust and biomass burning events

Athanasios Nenes, Kalliopi Violaki, Christos Panagiotopoulos

The importance of dust and biomass burning episodes on the atmospheric concentration of water-soluble reactive phosphate (SRP) was determined in the eastern Mediterranean. SRP was measured with a new rapid real-time automated analytical system with a time ...

ELSEVIER2022

Bioaerosols and dust are the dominant sources of organic P in atmospheric particles

Athanasios Nenes, Kalliopi Violaki

Several studies assessed the impact of inorganic P in fertilizing oligotrophic areas, however, the importance of organic P in such fertilization processes received far less attention. In this study, the amount and origin of organic P delivered to the easte ...

NATURE PORTFOLIO2021

Source apportionment of atmospheric P using the Positive Matrix Factorization (PMF) model

Athanasios Nenes, Kalliopi Violaki, Christos Panagiotopoulos

The PMF receptor model was applied to a combined dataset using specific markers such as phospholipids and sugars together with other metals (e.g. Al, Pb, V) and ions (e.g. K+, Ca2+, SO42-, NO3-) as tracers of main aerosol sources in order to characterize t ...

2020

The role of Organophosphate Esters Flame Retardants and plasticizers (OPEs) in Phosphorus Cycle in the atmosphere of the Mediterranean Sea

Athanasios Nenes, Kalliopi Violaki, Christos Panagiotopoulos

The atmosphere is considered as an important external nutrient source for the marine environment, especially in remote ocean waters or the oligotrophic Mediterranean Sea. Phosphorus (P) is a critical nutrient affecting primary productivity in large areas o ...

2020

Effects of Atmospheric Processing on the Oxidative Potential of Biomass Burning Organic Aerosols

Athanasios Nenes, Kalliopi Violaki

Oxidative potential (OP), which is the ability of certain components in atmospheric particles to generate reactive oxidative species (ROS) and deplete antioxidants in vivo, is a prevailing toxicological mechanism underlying the adverse health effects assoc ...

AMER CHEMICAL SOC2019

Atmospheric evolution of molecular-weight-separated brown carbon from biomass burning

Athanasios Nenes, Kalliopi Violaki

Biomass burning is a major source of atmospheric brown carbon (BrC), and through its absorption of UV/VIS radiation, it can play an important role in the planetary radiative balance and atmospheric photochemistry. The considerable uncertainty of BrC impact ...

Copernicus GmbH2019

Enhanced Iron Solubility at Low pH in Global Aerosols

Yan Feng, Athanasios Nenes, Kalliopi Violaki

The composition and oxidation state of aerosol iron were examined using synchrotron-based iron near-edge X-ray absorption spectroscopy. By combining synchrotron-based techniques with water leachate analysis, impacts of oxidation state and mineralogy on aer ...

2018