The study aimed to evaluate the burden of anthropogenically emitted pollutants over an ecologically sensitive region of Munnar in Western Ghats, and quantify a baseline for aerosol measurements for comparisons with highly polluted urban clusters in India. Pre-monsoon sampling of PM₁ aerosols was carried out at the NABHA (Natural Aerosol and Bioaerosol at High Altitude) laboratory (10.09°N, 77.07°E), located ~1600 m above sea level, approximately 90 km east of the Arabian Sea. The collected PM₁ particles were analysed for metals, carbonaceous fractions, inorganic species, and polycyclic aromatic hydrocarbons (PAHs) to identify potential pollution sources and evaluate the toxicity of the sampled airmasses.

The PM₁ concentrations at this ecologically sensitive site were notably elevated, with an average of 21.7 ± 5.5 µg/m³ for the sampling duration. The physio-chemical analysis revealed the composition consisting of approximately 8% crustal dust, 7% sea salt, 20% sulphate, 7% ammonium, 42% organic mass (OM), and 4% elemental carbon (EC). Surprisingly, PM-bound nitrates were below quantifiable levels, likely due to the region's high relative humidity (>80%) and frequent precipitation, which may have scavenged nitrate salts, given their high water-solubility. However, nitrogen in the form of ammonia (1.5 ± 0.9 µg/m³) and water-soluble nitrogen (2.4 ± 0.8 µg/m³) was abundant in PM₁. The concentration of PM₁-bound USEPA priority PAHs was 98.1 ± 11.2 ng/m³. This included 2–3 ring PAHs at 41.5 ± 7.5 ng/m³ and 4–6 ring PAHs at 56.7 ± 7.2 ng/m³.

Both the PM₁ mass concentration and chemical characterization showed significant contribution of anthropogenically derived aerosol mass burden. The elevated OC/EC ratio (~6.6), coupled with a high water-soluble organic carbon (WSOC) fraction (~0.8), suggests a significant contribution from biomass burning emissions and active combustion sources in the region during sampling duration. Emissions from tea processing factories, coupled with the unchecked growth of tourist vehicles, are significant contributors to the regional high levels of sulphate, EC, Zn, Mn, Cu, and heavy metals in the ambient air. The influx of marine aerosols from the Arabian Sea further amplifies the regional pollutant load, particularly sulphate concentrations, formed through the atmospheric oxidation of dimethyl sulphide released by oceanic phytoplankton. These marine air masses additionally carry ship emissions, as evidenced by the significant presence of Ni and V in the aerosol composition.

The insights gained from this data at a strategically important geographic location are pioneering and have the potential to make a significant contribution to the development of pollution control policies in ecologically sensitive and high-altitude areas. Additionally, these findings could serve as a valuable resource for advancing climate change research.

How to cite: Gupta, A. D., Gupta, T., Gunthe, S. S., and Singh, A.: Characteristic aerosol properties from ecologically sensitive high-altitude region of Western Ghats in India, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-561, https://doi.org/10.5194/egusphere-egu25-561, 2025.

The Montreal Protocol which mandated the global phase-out of ozone-depleting substances, contributed to the gradual recovery of Antarctic stratospheric ozone. Current projections estimate that the Antarctic ozone level recovers to the 1980 values by 2066. However, anomalous behaviours of the Antarctic ozone hole such as increased ozone hole area and prolonged ozone depletion have been observed since 2020. During this period, extreme events such as the Australian bushfires in 2020 and the Hunga Tonga–Hunga Haʻapai volcanic eruption in 2022 injected a significant amount of aerosols into the lower stratosphere. These aerosols provided the surface for chlorine activation reactions, contributing to chemical ozone loss in the polar lower stratosphere. Concurrently, previous studies suggest that the observed ozone depletion is also attributed to dynamic changes in the polar vortex and the descent of mesospheric air to the lower stratosphere. However, the relative percentage contribution of chemical and dynamical loss contributing to total ozone loss in recent years remains unquantified. In this study, we decompose the total ozone loss into chemical and dynamical losses using the passive tracer method, where ozone is considered as a passive tracer and simulated in the Chemical Lagrangian Model of the Stratosphere (CLaMS) using reanalysis data. The difference between the observed and simulated ozone provides information about the chemical ozone loss. These findings will help in advancing our understanding of the factors leading to the recent enhanced ozone depletion and the potential implications on the long-term healing of the ozone layer.

How to cite: Srinivasan, P., Kudilil, S., Narayana Sarma, A., Sreedharan K., S., and Krishnaswamy K, M.: Quantification of Chemical and Dynamical loss in Recent Antarctic Ozone depletion, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-658, https://doi.org/10.5194/egusphere-egu25-658, 2025.

Entrance of metals in any form through any pathway causes significant damage to human health.  The present study quantifies probabilistic health risk for carcinogenic and non-carcinogenic metals entering through inhalation, ingestion, and dermal routes within the human body for different age groups (children and adults). Water soluble metals (major metals; Na, Ca, K, Al, Mg, and trace metals; Fe, Zn, Sr, Ni, Cu, Mn, Cr, Ba, and Cd,) present into clouds over hilltop sites of the Western Ghats (Mahabaleshwar) and Eastern Himalayas (Darjeeling) situated at the entrance and final destination of monsoonal clouds over Indian Subcontinents are measured using ICP-OES. pH of cloud water is found to be alkaline in nature over both measurement sites. Clouds contain two times higher total soluble metal concentration (TMC) over Mahabaleshwar than that of Darjeeling. Analysis of enrichment factor and PCA suggest road dust, contributes maximum to the loading of metals into the clouds while desert dust coming from Arabian deserts contribute more to the initial clouds found in Western Ghats and fossil fuel influences maximum to the Himalayan clouds. Heavy metal pollution index (HPI) is found to be 14.8 over Mahabaleshwar and 22.6 over Darjeeling indicating relatively higher polluted clouds over Darjeeling due to higher concentrations of toxic metals like Cd and Zn emitted from fossil fuel combustion and road dust. Inhalation of polluted clouds containing higher concentrations of toxic metals like Cd, Cr, Mn, and Ni are the most potential threat to non-carcinogenic diseases. Cd is most dominating metal in clouds over Darjeeling, mainly coming from fossil fuel combustion, and has two folds higher HQ values than the Mahabaleshwar. Cr emitted from industrial waste has the highest carcinogenic health risk factor for children and adults over Mahabaleshwar (3.2×10^-7, 2.3×10^-7) than that of Darjeeling (2.1×10^-7, 1.5×10^-7). The present study suggests that clouds contain major metals like Na, Ca, Al, etc., mainly coming from marine sources and desert dust over the Arabian Sea and nearby continental regions while entering to Indian Sub-continental region, and later contaminated with trace metals like Cd, Cr, Cu, Ni, etc. emitted from vehicular emissions, industrial waste, and road dust that have greater impact on human health via inhalation pathway responsible for non-carcinogenic and carcinogenic diseases.

How to cite: Mushtaque, M. A., Saikh, S. R., Biswas, A., Darbha, G. K., and Das, S. K.: An Investigation on Source-Specific Health Risks Associated with Metals Present in Clouds over Hilly Regions in Indian Subcontinent, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1053, https://doi.org/10.5194/egusphere-egu25-1053, 2025.

Understanding aerosol particles in the Arctic is crucial due to their impact on the region’s radiative balance and their role in modifying cloud properties. These interactions drive unique feedback mechanisms that enhance Arctic warming and influence global climate systems. Consequently, it is important to identify and quantify Arctic aerosol particle sources and sinks, including their vertical transport, and to characterize their optical properties and resulting effects on cloud formation. Despite the importance of aerosol particles in the Arctic, there is a lack of direct measurements of aerosol particles over the Arctic especially over the Arctic marine boundary layer. In this context, we have conducted aerosol measurements aboard the German research vessel Polarstern during the ATWAICE (Atlantic Water Pathways to the Ice in the Nansen Basin and Fram Strait) expedition from June to August 2022. This study included continuous measurements of physical and chemical aerosol parameters to investigate variations in aerosol properties. On-line measurements of black carbon (BC) and its mixing state were complemented by off-line analyses of seawater and fog water samples to identify transport pathways of BC particles. Additionally, seawater, aerosol filter samples, and fog water samples were analyzed to explore how ice nucleating particles are linked across these compartments. Vertical profiles of aerosol particles were measured above different surface conditions to examine the direction of vertical particle transport. Higher aerosol concentrations were recorded as the ship passed through the outer margin of the marginal ice zone, where marine sources dominate, supported by evidence of significant photochemical ageing processes. The highest values of refractory black carbon (rBC) and light scattering coefficients were measured during the transact from northern Europe to the Arctic circle (between 56°N to 70°N), with average rBC concentrations of approximately 40 ng m^-3 and light scattering at 525 nm averaging ~29 Mm^-1. During this period, air mass trajectories reflected a nearly equal influence from both continental and marine sources. In contrast, the lowest scattering and absorption values were observed in the central Arctic, when the ship navigated in densely packed ice regions under the influence of north-easterly air masses originating over the Arctic Ocean. A comprehensive analysis of these findings will be presented in this presentation.

How to cite: Babu Suja, A., Müller, T., Pöhlker, M., Wex, H., Held, A., van Pinxteren, M., Yang, Y., Oehlke, P., Lüchtrath, S., Siebert, H., Mathes, T., Merkel, M., and Wehner, B.: Overview of Atmospheric Aerosol Observations during the ATWAICE Expedition in the Central Arctic, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7323, https://doi.org/10.5194/egusphere-egu25-7323, 2025.

Aerosol optical depth (AOD) observations are usually focused on the visible wavelength. Recent studies highlight the potential of the infrared emission waveband in providing valuable insights for aerosol compositions (Ji et al., 2023). Expanding AOD measurements into the infrared spectrum offers an approach to enhance our understanding of aerosol properties. In this study, we use solar absorption spectra measured by Fourier Transform Infrared Spectrometer (FTIR) to obtain the infrared spectrum AOD using Langley method (Barreto et al., 2020) in several stations, including Ny-Ålesund (Arctic), Bremen (mid-latitude), and Palau (tropics). Integrating FTIR and sun-photometer observations, we obtain AOD in visible and infrared spetrum regions. This work highlights the possibility of extending traditional AOD retrieval method in visible wavelengths to a broad spectrum range.

Reference:

Ji, D., Palm, M., Ritter, C., Richter, P., Sun, X., Buschmann, M., and Notholt, J.: Ground-based remote sensing of aerosol properties using high-resolution infrared emission and lidar observations in the High Arctic, Atmos. Meas. Tech., 16, 1865–1879, https://doi.org/10.5194/amt-16-1865-2023, 2023.

Barreto, África, Omaira Elena García, Matthias Schneider, Rosa Delia García, Frank Hase, Eliezer Sepúlveda, Antonio Fernando Almansa, Emilio Cuevas, and Thomas Blumenstock. 2020. "Spectral Aerosol Optical Depth Retrievals by Ground-Based Fourier Transform Infrared Spectrometry" Remote Sensing 12, no. 19: 3148. https://doi.org/10.3390/rs12193148

How to cite: Ji, D., Palm, M., Sun, X., and Notholt, J.: Expanding the Langley Calibration Method to Infrared Wavelengths: Modeling, Validation, and Applications, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9716, https://doi.org/10.5194/egusphere-egu25-9716, 2025.

Processes occurring over the oceans, including greenhouse gas (GHG) fluxes and cloud-aerosol interactions, are a major source of uncertainty in the present climate state and hence in estimating near-term warming. To reduce this uncertainty, more comprehensive and specific observations over the oceans are needed. Due to the limited supply of dedicated research vessels, platforms of opportunity are essential to fill these observational gaps. We discuss here the Ships of Opportunity for Atmospheric Research (SOAR) program, a science infrastructure program built in collaboration with OceansX. SOAR’s purpose is to expand atmospheric observations in under-observed oceanic regions, providing new measurements to existing climate observation programs that provide open data to the global community.

We present current pilot projects under SOAR. A GHG flask sampler from NOAA Global Monitoring Lab is deployed on the Maersk Kentucky, which is taking samples as the ship transits the tropical Pacific. Sensors from NASA’s Maritime Aerosol Network (AERONET MAN), are also deployed on two other Maersk vessels and a Smyril Line vessel, where volunteer sailors are collecting aerosol optical depth measurements that are now accessible on the AERONET/MAN webpage. Finally, in collaboration with NOAA Global Monitoring Laboratory, SilverLining is developing a version of the NOAA Federated Aerosol Network (NFAN) package for deployment on ships of opportunity. This effort includes integrating instruments into a system adapted to marine environments and validating it against the NFAN technical standards. This project serves as a proof of concept for including additional higher-complexity atmospheric instrumentation packages in ships of opportunity programs

How to cite: Lamarque, J.-F., Wong, A., Kaufman, S., Bowen, D., Schubert, S., Sweeney, C., Andrews, B., and van de Kraats, B.: Ships of Opportunity for Atmospheric Research: Pilot Efforts, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11958, https://doi.org/10.5194/egusphere-egu25-11958, 2025.

Black carbon (BC) aerosols are a major concern in changing climatic scenario due to their ability to absorb solar radiation. This study investigates the temporal variation of BC and its impact on radiative forcing in the Sikkim Himalayan region. It aimed to understand the optical properties of BC and its radiative forcing at Yumthang Valley, a high-altitude (~3800 m) remote location in North Sikkim, India. In-situ measurements were undertaken to quantify BC mass concentration, using an Aethalometer, and satellite retrieval techniques were employed to assess the optical properties of BC during May 2022 to April 2024. The monthly mean BC concentration in the valley ranged from 1.03 ± 3.07 to 9.54 ± 16.44 µgm^-3, with an annual mean of 5.07 ± 16.54 µgm^-3. BC concentrations decrease during monsoon months due to limited long-range transport and effective wet scavenging. Biomass burning contributes significantly to BC levels, accounting for 88% of the total, with the highest contribution in September (55%) and the lowest in February (21%). Transport models indicate inputs from the Indo-Gangetic Plain and adjacent valleys with increased biomass burning activity. Seasonal variations reflect tourism-driven emissions and local wood burning, with the lowest levels observed in the early morning hours. BC-induced direct radiative forcing (DRF) was also calculated at the surface (SFC) and top of the atmosphere (TOA) using Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model which estimate a substantial forcing at both the surface and top of the atmosphere. The BC-induced atmospheric heating rates suggest potential regional warming, which could accelerate glacier melt in the region.

How to cite: Gupta, A., Ranjan, R. K., Panicker, A., Anand, V., and Rajak, R.: Seasonal Dynamics and Radiative Impacts of Black Carbon in the Yumthang Valley in Sikkim Himalaya, India, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12303, https://doi.org/10.5194/egusphere-egu25-12303, 2025.

Understanding the pathways through which aerosols are emitted, transformed, and removed in remote and climatically sensitive regions is essential for minimizing uncertainties in global climate modeling. This study capitalizes on the unique conditions created by the COVID-19 societal slowdown to explore anthropogenic aerosol behavior over South Asia. Observations during this period showed a marked decline in aerosol concentrations, resulting in a demasking effect comparable to nearly 75% of the radiative forcing induced by CO₂ in the region. Additionally, this reduction caused a ~7% increase in surface-reaching solar radiation and a ~0.4 K d⁻¹ decrease in atmospheric solar heating.

Black carbon (BC) aerosols were further analyzed using dual-isotope (Δ¹⁴C and δ¹³C) techniques at monitoring sites in the Maldives and Bangladesh. Findings revealed a significant decrease in fossil fuel-derived BC, dropping from 49% to 35%, while emissions from C₃ biomass burning rose from 31% to 55%. These changes reflect reduced fossil fuel usage alongside increased reliance on crop residue burning and biomass for domestic energy needs during the slowdown.

These findings highlight the complex interplay between human activities and natural processes in determining aerosol-climate interactions across South Asia. The rapid changes in emission patterns observed during societal disruptions underscore the potential for targeted policy interventions to mitigate climate impacts and reduce atmospheric pollution.

How to cite: Chandrika Rajendran Nair, H. R.: When the World Stopped: Insights into Aerosol masking effect and Black Carbon Source Shifts, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12522, https://doi.org/10.5194/egusphere-egu25-12522, 2025.

Aerosol Black Carbon (BC) can influence Earth’s radiation balance and climate in numerous ways. Atmospheric warming and the modification of the local thermodynamic structure of the atmosphere, cloud formation and precipitation are known to be influenced by BC aerosols. Many of these effects depend on the vertical distribution of BC. When the concentration of absorbing aerosols such as BC are significant, Aerosol Optical Depth (AOD) and chemical composition are not the only determinants of aerosol radiative effects. Under such circumstances, the altitude of the aerosol layers also plays a crucial role. Thus, high BC loading at elevated altitudes is of utmost importance to regional weather and climate. These elevated aerosols can further be lofted to the upper troposphere and lower stratospheric regions through strong tropical monsoonal updrafts. Despite the above significances of elevated BC layers, measurements of the vertical distribution of BC in the middle and upper tropical troposphere are extremely scarce due to the difficulties in devising suitable instrumentation. Hence, direct measurements of BC are virtually non-existent at altitudes around 10 km or above. Under this backdrop, we conducted a series of high-altitude balloon observations to improve the understanding of such elevated layers. Results of these experiments conducted during the winter and pre-monsoon summer seasons of the years 2023-2024 show several elevated layers of BC aerosol, reaching as high as three times that of the surface concentrations. In the mid/upper troposphere, aircraft engine exhaust is the main if not the only source for anthropogenic emissions, with a technology trade-off existing between the fuel performance of engines, and climate forcers. The role of aircraft emissions in the mid-tropospheric region in contributing to these layers has also been examined in the background of balloon experiments.

How to cite: Sunilkumar, K., Ajay, A., Anand, N. S., Satheesh, S. K., and Krishna Moorthy, K.: Vertical profiles of black carbon measured using high-altitude balloon experiments over an urban location in India, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14674, https://doi.org/10.5194/egusphere-egu25-14674, 2025.

Atmospheric aerosols contribute to the largest uncertainty in estimates of the Earth’s global energy balance. Their interactions with sunlight and their ability to affect cloud formation leads to both direct and indirect influence of radiative forcing. The substantial uncertainties associated with aerosol climate effects stem amongst others from the complexity of their sources, composition, and properties. Aerosols in coastal areas present a challenging mix of inorganic and organic particles from diverse sources, making measurements and characterization of their properties in these regions essential. 

This study presents measurements of the optical properties of ambient aerosols on Askö, Sweden, from October 2024 to January 2025. Askö, an island and nature reserve located approximately 80 km south of Stockholm, experiences low levels of local pollution, making it an ideal location for studying marine aerosols. Its location in the Trosa Archipelago, facing the Baltic Sea, also makes it well-suited for investigating the impact of long-range transport from Central and Eastern Europe.

Instruments were placed in a container situated on top of a floating platform near the island. Scattering coefficients, measured with a nephelometer, and absorption coefficients, measured with an aethalometer, were used to calculate Scattering and Absorption Ångström Exponents. The Ångström matrix was used to characterize aerosol types found in the area at different times. The optical data set is further complemented by local meteorological data, particle size distributions, and back trajectory analysis. This combination of data will give valuable insights into aerosol sources at this remote location, the degree of aerosol ageing, and the identification of prevailing emissions sources such as local emissions versus long-range transport of air masses.   

How to cite: Tygesen Skønager, J., Salter, M., Bilde, M., and Rosati, B.: Relating aerosol optical properties to different emission sources at a coastal site in Sweden, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17907, https://doi.org/10.5194/egusphere-egu25-17907, 2025.