Analysis of aerosol liquid water content and its role in visibility reduction in Delhi

Ali, Umer; Faisal, Mohd. Nishat; Ganguly, Dilip; Kumar, Mayank; Singh, Vikram

doi:10.1016/j.scitotenv.2023.161484

Cited by 14 publications

(4 citation statements)

References 73 publications

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“…It is very clear that the visibility degraded rapidly with the increase in PM 2.5 levels and the exponential coefficients also increased with the PM 2.5 levels, indicating the same amount of ALWC can lower the visibility even more significantly when the PM 2.5 pollution is greater. As the ALWC increases, the aerosol size increases due to the uptake of water and can lead to a large increase in the aerosol extinction coefficient [ 61 , 62 ], which has been observed in various sites including Guangzhou, China and Delhi, India [ 63 , 64 ]. Overall, when the PM 2.5 concentration was higher than 30 μg m −3 , in most cases, the association with a very small amount of ALWC could lower the visibility to less than 10 km, i.e., hazy conditions; when the PM 2.5 mass loading was between 20 and 30 μg m −3 , the ALWC increased to ~15 μg m −3 and the visibility decreased to near 10 km, approaching hazy conditions.…”

Section: Resultsmentioning

confidence: 99%

Direct Measurement of Aerosol Liquid Water Content: A Case Study in Summer in Nanjing, China

Li,

Cui,

et al. 2024

Toxics

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Aerosol liquid water content (ALWC) affects the mass loading, optical properties, and toxicity of aerosols. However, the measurement of ALWC is very rare due to its requirement of sophisticated instruments and its high operational costs. In this work, we improved on our previous simple, low-cost method by using a combination of one real-time fine particulate matter (PM2.5) monitor and two turbidimeters and successfully applied these for the direct measurement of ALWC in PM2.5 in Nanjing during the summer of 2023. The average ALWC during this measurement period occupied ~1/6 of the total PM2.5 mass, and this contribution was even greater with the elevation in the PM2.5 concentration. The ALWC was, as anticipated, closely related to the relative humidity (RH) and PM2.5 concentrations, but it did not always increase with the air quality index (AQI) due to the fact that polluted periods in summer were often governed by high O3 levels, not PM2.5 levels. The ALWC also had a great impact on visibility; it could decrease the visibility rapidly to hazy conditions when the dry PM2.5 was not high (~30 μg m−3) or the AQI was “good” (75~100), indicating that the air quality classified as “good” using the dry PM2.5 concentration might actually be “lightly polluted” if the ALWC is included. We also found that the air mass originating from Northeast China had the lowest PM2.5 mass concentration yet the highest ALWC values due to its high RH. Moreover, the quantification of ALWC levels can help us understand the solubility/bioavailability and thus the toxic effects of some specific components (for example, heavy metals or organics). Moreover, the influence of ALWC on air quality classifications should also be considered in the assessment of the health effects of air pollution and in public health early warning and protection.

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Section: Resultsmentioning

confidence: 99%

Direct Measurement of Aerosol Liquid Water Content: A Case Study in Summer in Nanjing, China

Li,

Cui,

et al. 2024

Toxics

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“…The average ε(NH 4 + ) for PM 1 and PM 2.5 was 0.42 ± 0.17 and 0.55 ± 0.15 respectively, attributed to the substantial excess ammonia left in the gas-phase. Due to this, several studies have highlighted that pollution control strategies in India should be directed at reducing high NH 3 concentrations 25 , 35 . Here, in this study, we did not investigate the effect of pH and ALWC on the phase partitioning of sulfate ε(SO 4 2− ).…”

Section: Resultsmentioning

confidence: 99%

Thermodynamical framework for effective mitigation of high aerosol loading in the Indo-Gangetic Plain during winter

Acharja,

Ghude,

Sinha

et al. 2023

Sci Rep

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The Indo-Gangetic Plain (IGP) experiences severe air pollution every winter, with ammonium chloride and ammonium nitrate as the major inorganic fractions of fine aerosols. Many past attempts to tackle air pollution in the IGP were inadequate, as they targeted a subset of the primary pollutants in an environment where the majority of the particulate matter burden is secondary in nature. Here, we provide new mechanistic insight into aerosol mitigation by integrating the ISORROPIA-II thermodynamical model with high-resolution simultaneous measurements of precursor gases and aerosols. A mathematical framework is explored to investigate the complex interaction between hydrochloric acid (HCl), nitrogen oxides (NOx), ammonia (NH3), and aerosol liquid water content (ALWC). Aerosol acidity (pH) and ALWC emerge as governing factors that modulate the gas-to-particle phase partitioning and mass loading of fine aerosols. Six "sensitivity regimes" were defined, where PM1 and PM2.5 fall in the "HCl and HNO3 sensitive regime", emphasizing that HCl and HNO3 reductions would be the most effective pathway for aerosol mitigation in the IGP, which is ammonia-rich during winter. This study provides evidence that precursor abatement for aerosol mitigation should not be based on their descending mass concentrations but instead on their sensitivity to high aerosol loading.

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“…4,5 The hygroscopic nature of inorganic substances typically results in an increased aerosol liquid water content (ALWC) under typical ambient relative humidity (RH) conditions. 6,7 Field measurements have indicated that an elevated inorganic fraction in PM 2.5 was often associated with the formation of haze, which exacerbates PM 2.5 pollution across the Northeast Asian cities. 8,9 The physical properties of aerosols, including the PM 2.5 phase states (often reported using viscosity values), significantly impact the atmospheric chemistry and air quality.…”

Section: Introductionmentioning

confidence: 99%

“…In recent decades, rapid industrial development in Northeast Asia has resulted in significantly elevated fine particulate matter (PM 2.5 ) levels. , PM 2.5 can substantially affect both air quality and human health depending on its physical and chemical properties . Field studies have shown that PM 2.5 is a complex mixture comprising organic aerosol (OA) (i.e., primary organic aerosols (POAs) and secondary organic aerosols (SOAs)) and inorganic substances (e.g., ammonium nitrate (AN) and ammonium sulfate (AS)). , The hygroscopic nature of inorganic substances typically results in an increased aerosol liquid water content (ALWC) under typical ambient relative humidity (RH) conditions. , Field measurements have indicated that an elevated inorganic fraction in PM 2.5 was often associated with the formation of haze, which exacerbates PM 2.5 pollution across the Northeast Asian cities. , …”

Section: Introductionmentioning

confidence: 99%

Influence of Relative Humidity and Composition on PM_2.5 Phases in Northeast Asia

Seong,

Kim,

Jeong

et al. 2024

ACS Earth Space Chem.

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In Northeast Asia, the elevated levels of fine particulate matter (PM 2.5 ) are an environmental concern, yet their physicochemical properties have been poorly characterized. Herein, we determined the phase states of PM 2.5 in 92 filter samples collected from four different cities� Beijing, Seoul, Seosan, and Ulaanbaatar�during 2020−2022, within a temperature range of ∼290−293 K. We noted a distinct trend in the boundary relative humidity (RH) of liquid and semisolid phases within these PM 2.5 samples. As the inorganic fraction increased, the RH of the liquid phase decreased, whereas that of the semisolid phase increased. This behavior was strongly influenced by the chemical composition of PM 2.5 . By incorporating ambient RH data from each city, we estimated the prevalent PM 2.5 phase states within the planetary boundary layer of Northeast Asia. Our findings revealed that the dominant phase states of PM 2.5 in these urban areas were liquid and semisolid. Additionally, we showed a critical threshold based on the aerosol liquid water content (ALWC) in PM 2.5 : a primarily liquid phase for ALWC/PM 2.5 ratios of ≥∼0.5 and a predominantly semisolid phase for ALWC/PM 2.5 ratios of <∼0.5. These insights could contribute to a better understanding of the mechanisms underlying aerosol pollution in Northeast Asia.

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Analysis of aerosol liquid water content and its role in visibility reduction in Delhi

Cited by 14 publications

References 73 publications

Direct Measurement of Aerosol Liquid Water Content: A Case Study in Summer in Nanjing, China

Direct Measurement of Aerosol Liquid Water Content: A Case Study in Summer in Nanjing, China

Thermodynamical framework for effective mitigation of high aerosol loading in the Indo-Gangetic Plain during winter

Influence of Relative Humidity and Composition on PM_2.5 Phases in Northeast Asia

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Analysis of aerosol liquid water content and its role in visibility reduction in Delhi

Cited by 14 publications

References 73 publications

Direct Measurement of Aerosol Liquid Water Content: A Case Study in Summer in Nanjing, China

Direct Measurement of Aerosol Liquid Water Content: A Case Study in Summer in Nanjing, China

Thermodynamical framework for effective mitigation of high aerosol loading in the Indo-Gangetic Plain during winter

Influence of Relative Humidity and Composition on PM2.5 Phases in Northeast Asia

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Influence of Relative Humidity and Composition on PM_2.5 Phases in Northeast Asia