Environmental science: atmospheres最新文献

The influence of a prolonged Saharan Dust event across Europe and specifically in Munich (Germany) in March 2022 was detected and analyzed in detail. The event arose from a sequence of Saharan Dust incursions intertwined with a stagnation in the regional circulation leading to the persistence of a mineral dust plume for several weeks over the region. Trace element and meteorological data were collected. Enrichment factors, size distribution analyses, and multivariate techniques such as Varimax and Self-Organizing Maps (SOM) were applied to highlight the influence of Saharan Dusts and to evaluate the pollution sources in Munich municipality. The overall results revealed how the Munich airshed was clearly affected by long-distance mineral dusts from the North African desert, that increased the concentrations of natural (e.g. Al, Mg, Ca) and anthropogenic (e.g. Sb, Mo, Pb) elements based on the different paths followed by the dusts. Moreover, the chemometric analyses revealed a range of well-defined local anthropogenic emission sources including road traffic, energy production by coal combustion (S and Se), traffic (Cu, Sb), and waste incineration (Zn).

The contributions of meteorology and emissions to air pollutant trends are critical for air quality management, but they have not been fully analyzed, especially in the background area of northern China. Here, we used a machine learning technique to quantify the impacts of meteorological conditions and emissions on PM_2.5, NO₂, SO₂, O₃, and CO pollution during 2013–2021 and evaluated their contributions to Clean Air Action policies. The annual effect of the meteorology on PM_2.5, NO₂, SO₂, and CO levels was dominated by the meteorological conditions during the cold season, while that of the O₃ level largely depended on the meteorological conditions during the warm season. Meteorology-driven anomalies contributed −14.8 to 10.3%, −8.5 to 7.3%, −11 to 7.1%, −7.9 to 6.0%, and −7.4 to 7.3% to the annual mean concentrations of PM_2.5, NO₂, SO₂, O₃, and CO during the study period, respectively. The Clean Air Actions have led to a major improvement in the air quality at regional scale, with the reduction of 1.7 μg m⁻³ year⁻¹, 0.2 μg m⁻³ year⁻¹, 1.5 μg m⁻³ year⁻¹, 0.7 μg m⁻³ year⁻¹, and 0.03 mg m⁻³ year⁻¹ for PM_2.5, NO₂, SO₂, O₃, and CO at background area, respectively, after meteorological correction. Although emissions dominated the long-term variations in pollutants, the meteorological conditions obviously played a positive role during the action periods for pollutants except for O₃. Considering the notable effects of the meteorological conditions on air pollution and the interreaction between pollutants, a more comprehensive control strategy should be considered on a broader regional scale.

Microplastics (MPs) have recently become a growing environmental pollution concern. MPs are easily transferred and ubiquitously found in ambient air. MPs in the air can act as carriers for several toxic pollutants, and exposure to MPs can lead to pulmonary diseases in humans. Polyethylene terephthalate (PET) is one of the most abundant MPs used in the manufacturing of various fibres and plastics. In this study, we present a method for the determination of mass concentrations of PET MPs in the airborne inhalable fraction of fine particulate matter (PM_2.5) using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). Teflon and quartz fiber filters were tested for extraction efficiency in measuring the mass concentrations of airborne PET MPs. Teflon filters showed good recovery (80–120%) compared to quartz fiber filters. Using this method, a pilot study was carried out in Delhi, the national capital of India, and Mohali, a suburban city in the northwest Indo-Gangetic Plain (NWIGP), for the determination of mass concentrations of PET MPs present in airborne PM_2.5. The observed maximum mass concentrations of PET MPs in airborne PM_2.5 in Delhi and Mohali are 135.20 ng m⁻³ and 157.98 ng m⁻³, respectively.

Ice nucleating particles (INPs) play a crucial role in freezing water droplets by acting as heterogeneous ice nuclei, influencing cloud phase state and climate dynamics. INPs from marine aerosol particles are particularly relevant. Saturated fatty alcohols and acids have been identified in sea spray aerosols (SSA). In this study, we employ a micro-Raman spectrometer integrated with an environmental cell to control relative humidity and temperature and measure the ice nucleation activity of individual lipid particles, including fatty alcohols and fatty acids of varying chain lengths. For fatty acids, we observe little IN activity for these lipid particles as they freeze close to the temperature found for homogeneous freezing. For fatty alcohols, we demonstrate that freezing temperatures depend on the carbon chain length, with longer chains leading to warmer ice nucleating temperatures. Although this result qualitatively agrees with existing literature, we observe that the ice nucleating temperatures of these lipid particles differ from the freezing temperatures measured for fatty alcohol monolayers at the air/water interface for large water droplets. To better understand these differences, we further investigate the effects of droplet size as well as phase state by theoretically determining the wet viscosity on freezing. Our results, taken together, suggest that for fatty alcohol particles, freezing occurs at the lipid particle/water interface. Overall, our findings highlight the influence of lipid chain length, droplet size, and phase state on ice nucleation for lipid particles.

The use of low-cost sensors (LCS) for the evaluation of the ambient pollution by particulate matter (PM) has grown and become significant for the scientific community in the past few years. However promising this novel technology is, the characterization of their limitations is still not satisfactory. Reports in the scientific literature rely on calibration, which implies the physical (or geographical) co-location of the LCS with reference in situ (or remote, e.g. onboard satellite platforms) instrumentation. However, calibration is not always feasible, and even when feasible, the validity of the developed relationship, even in similar settings, is subject to large uncertainties. In the present work, the performance of a popular LCS for PM, the Plantower PMS5003, is investigated. The LCS performs particle counts, which is the physical quantity that is input to the black-box model of the manufacturer to compute the ambient PM mass, which is output to the operator. The particle counts of LCS Plantower PMS5003 units were compared to those of the co-located research-grade Grimm EDM-164 monitor. The results show that humidity possibly has a reduced influence on the performance, but the performance can better be constrained, however spanning more than one order of magnitude in terms of agreement ratio, by functions of the actual particle count itself. In view of these results, further development in the field of LCS for PM monitoring should focus on improvements of the physical design of the devices, in order to enhance the sizing of the particles. The use of the actual Plantower PMS5003 models should be limited to the monitoring of PM mass in the smaller size bins.

Ozone (O₃) pollution has been recognized as the major air pollution in the Pearl River Delta (PRD) region, South China. Understanding O₃ formation sensitive to volatile organic compound (VOC)- and nitrogen oxide (NO_X)-limited regimes is a key step for alleviating O₃ pollution. Herein, measurements of VOCs, NO_X and O₃ were simultaneously performed at multi sampling sites in an industrial park of the PRD region during June, 2020. VOCs/NO_X ratios ranged from 0.5 to 5.7, suggesting that the O₃ formation was in the VOC-limited regime in the industrial park. The estimated O₃ formation potential (OFP) of VOCs showed that alkenes and aromatic hydrocarbons from motor vehicles and industrial sources contributed to 40% and 39% of the O₃ formation, respectively, in the industrial park. However, a low O₃ level (<50 ppb) was observed in the region where high OFP values (>194 ppb) were estimated. Further analysis found that the concentration of NOx (25 ± 10 ppb) in the high O₃ region was lower than that (36 ± 6 ppb) in the low O₃ region, mostly due to the titration reaction of NO and O₃ to form NO₂, therefore leading to the consumption of O₃. This result implies that NO_X control was not conducive to the O₃ pollution in the study region. Thus, O₃ pollution control in the study region should be taken into consideration in terms of the effect of NO_X titration and control of VOC emissions.

The impact of water-soluble atmospheric iron on formation, growth and aging of secondary organic aerosol (SOA) is a controversial subject in the literature. Iron chemistry drives Fenton reactions in the aqueous phase which is dependent on pH. Flow reactor experiments in the dark and under humid conditions were conducted to investigate systematically the influence of ferrous iron in the aqueous phase on α-pinene SOA by online physical analysis and offline high-resolution mass spectrometry. During the experiments increased SOA formation under conditions favorable for dark Fenton chemistry in the aqueous phase was observed. Furthermore, samples with an acidified and iron-containing aqueous phase showed a degradation of pinyl-diaterpenyl (C₁₇H₂₆O₈) ester which ages through oxidation via OH radicals and can thus be evidence for ongoing degradation processes of high molecular weight molecules by iron chemistry. Moreover, higher abundance of dimer MW338 (C₁₉H₃₀O₅) in the acidic sample affected by Fenton's chemistry was detected which is suggested to be formed via acid catalysis indicating competing acidity-driven reactions influencing SOA formation. Therefore, this study provides insight into the impact of aqueous phase iron on SOA formation and transformation under simulated natural conditions.

Microplastics (MPs) have become a key environmental issue over the last few decades. However, while previous studies have mainly focused on aquatic MP pollution, research on atmospheric MPs remains limited. To expand our knowledge of atmospheric MPs, we collected atmospheric samples using active and dry deposition techniques during one year in an urban environment in the megacity of Hangzhou, China. MPs were identified in the samples using a range of analytical and optical techniques. The concentrations of MPs on the filters collected using active sampling ranged from 0.37–8.9 particles per m³, with an annual mean of 3.2 ± 0.5 particles per m³. The dry deposition rate of atmospheric MPs ranged from 441.18–3181.8 particles per m² per day, with an annual mean of 1387.8 ± 237.7 particles per m² per day. Fiber MPs were the most predominant type while a few film-type MPs were identified. Raman microspectrometer analysis identified that tires (27.0% of MPs) and polyethylene terephthalate (PET, 19.7% of MPs) were the dominant MP types. Finally, we estimated that the annual dry deposition rate of MPs in the Hangzhou urban area was 16.9 ± 2.9 tons. Exploring the abundance and deposition of MPs helps to evaluate their potential threat to human health or aquatic ecology, which finally contributes to development of MP control measures.

Increasing marine haze and clouds has been considered as a possible means of increasing the Earth's albedo. This would reduce solar heating and global warming, counteracting the effects of the anthropogenic increase in greenhouse gases. One proposed method of doing so would inject small droplets of seawater or condensation nuclei into the marine boundary layer, creating artificial haze and cloud. The equilibrium size of such droplets is described by the Köhler equation that includes the vapor pressure reduction attributable to the solute according to Raoult's law and the vapor pressure increase of a small droplet as a result of surface tension according to Kelvin. Here we apply this classic result to small droplets in the marine boundary layer, where the partial pressure of water vapor is less than the equilibrium vapor pressure because it is in equilibrium with the saline ocean. We calculate the equilibrium size of a droplet containing dissolved ions and find that the radius of a droplet of seawater shrinks greatly before it achieves equilibrium.