scholarly journals Effects of continental emissions on Cloud Condensation Nuclei (CCN) activity in northern South China Sea during summertime 2018

2020 ◽  
Author(s):  
Mingfu Cai ◽  
Baoling Liang ◽  
Qibin Sun ◽  
Shengzhen Zhou ◽  
Bin Yuan ◽  
...  
Keyword(s):  
Long Range ◽  
Particle Number ◽  
Cloud Condensation Nuclei ◽  
Northern South China Sea ◽  
Long Range Transport ◽  
Marine Atmosphere ◽  
Condensation Nuclei ◽  
Air Masses ◽  
Range Transport ◽  
Local Emissions

Abstract. Aerosol particles in marine atmosphere have been shown to significantly affect cloud formation, atmospheric optical properties, and climate change. However, high temporal and spatial resolved atmospheric measurements over sea are currently sparse, limiting our understanding of aerosol properties in marine atmosphere. In this study, a ship-based cruise campaign was conducted over northern South China Sea (SCS) region (19°37′ N to 22°43′ N, 113°44′ E to 118°12′ E) during summertime 2018. Chemical compositions of the non-refractory PM1 (NR-PM1), particle number size distribution (PNSD) and size-resolved cloud condensation nuclei (CCN) activity (at supersaturation ss = 0.18 %, 0.34 %, and 0.59 %) were measured by a time-of-flight aerosol chemical speciation monitor (ToF-ACSM), and the combination of a cloud condensation nuclei counter (CCNc) and a scanning mobility particle sizer (SMPS), respectively. Overall, aerosol particles exhibited a unimodal distribution (centering at 60∼80 nm) and dominated by sulfate (~46 %) in the NR-PM1, similar to the characteristic of previously-reported background marine aerosols. Two polluted episodes were respectively observed at the beginning (P1, 6th–8th August) and at the end (P2, 25th–26th August) of the campaign and both were characterized by high particle number concentrations (NCN) which were shown to originate from local emissions or pollutants from long range transport. Two relatively clean periods (C1, 9th–10th and C2, 19th–21st August) prior to and after tropical storm Bebinca (11th–15th August) were also classified due to substantial removal of pollutants by strong winds and rainfalls accompanying with the storm. A value of about 0.4 for aerosol hygroscopicity parameter κ measured in this study falls in a range of values (i.e., 0.2–1.0) reported previously for urban atmosphere and for remote marine atmosphere. The concentrations of trace gases (i.e., O3, CO, NOX) and particles (NCN and NCCN at ss = 0.34 %) were elevated at the end of the campaign and decreased with the offshore distance, suggesting important impacts of anthropogenic emissions from the inland Pearl River Delta (PRD) region on the northern SCS. A good correlation between NOX concentration and NCN implies similar sources (e.g., heavy ship, traffic, and biomass burning) for NOx and particles. The results showed that the NCCN/NCN,tot and the κ values obtained from the CCNc measurement (ss = 0.34 %) had no clear correlation either with the offshore distance or with the concentrations of the particles. Back trajectory analysis showed that the air pollutants originated from local emissions and from inland China continent via long range transport during P1 and P2, respectively. In addition, the air was affected by air masses from southwest and from Indo-China Peninsula during the clean C1 and C2 periods respectively. Chemical composition measurements showed an increase of organic mass fraction and no obviously different κ values were obtained from CCN measurements during C2 and P2, implying that the air masses carried pollutants from local sources during long range transport from Indo-China Peninsula and from the inland China continent respectively during the above two periods. Our study highlights dynamical variations of particle properties and the impact of long range transport from the China continent and Indo-China Peninsula on the northern SCS region during summertime.

scholarly journals Effects of continental emissions on cloud condensation nuclei (CCN) activity in the northern South China Sea during summertime 2018

2020 ◽  
Vol 20 (15) ◽  
pp. 9153-9167 ◽  
Author(s):  
Mingfu Cai ◽  
Baoling Liang ◽  
Qibin Sun ◽  
Shengzhen Zhou ◽  
Xiaoyang Chen ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Long Range ◽  
Particle Number ◽  
Cloud Condensation Nuclei ◽  
Northern South China Sea ◽  
Long Range Transport ◽  
Marine Atmosphere ◽  
Condensation Nuclei ◽  
Air Masses ◽  
Range Transport

Abstract. Aerosol particles in marine atmosphere have been shown to significantly affect cloud formation, atmospheric optical properties, and climate change. However, high temporally and spatially resolved atmospheric measurements over the sea are currently sparse, limiting our understanding of aerosol properties in marine atmosphere. In this study, a ship-based cruise campaign was conducted over the northern South China Sea (SCS) region during summertime 2018. The chemical composition of non-refractory PM1 (NR-PM1), the particle number size distribution (PNSD), and size-resolved cloud condensation nuclei (CCN) activity were measured by a time-of-flight aerosol chemical speciation monitor (ToF-ACSM) and the combination of a cloud condensation nuclei counter (CCNc) and a scanning mobility particle sizer (SMPS). Overall, aerosol particles exhibited a unimodal distribution centering at 60–80 nm and the chemical composition of the NR-PM1 was dominated by sulfate (∼ 46 %), which likely originated from anthropogenic emissions rather than dimethyl sulfide (DMS) oxidation. Two polluted episodes (P1 and P2) were observed, and both were characterized by high particle number concentrations (NCN) which originated from local emissions and from emissions in inland China via long-range transport. The concentrations of trace gases (i.e., O3, CO, NOx) and particles (NCN and NCCN at ss = 0.34 %) were elevated during P2 at the end of the campaign and decreased with offshore distance, further suggesting important impacts of anthropogenic emissions from the inland Pearl River Delta (PRD) region. Two relatively clean periods (C1 and C2) prior to and after tropical storm Bebinca were classified and the air was affected by air masses from the southwest and from the Indo-Chinese Peninsula, respectively. Chemical composition measurements showed an increase in organic mass fraction during P2 compared to C2; however, no obviously different κ values were obtained from the CCNc measurements, implying that the air masses carried pollutants from local sources during long-range transport. We report an average value of about 0.4 for the aerosol hygroscopicity parameter κ, which falls within the literature values (i.e., 0.2–1.0) for urban and remote marine atmosphere. In addition, our results showed that the CCN fraction (NCCN∕NCN, tot) and the κ values had no clear correlation either with the offshore distance or with concentrations of the particles. Our study highlights dynamical variations in particle properties and the impact of long-range transport from continental China and the Indo-Chinese Peninsula on the northern SCS region during summertime.

scholarly journals New particle formation in marine atmosphere during seven cruise campaigns

2018 ◽  
Author(s):  
Yujiao Zhu ◽  
Kai Li ◽  
Yanjie Shen ◽  
Yang Gao ◽  
Xiaohuan Liu ◽  
...  
Keyword(s):  
Long Range ◽  
Particle Number ◽  
Particle Formation ◽  
Long Range Transport ◽  
Northwest Pacific ◽  
Marine Atmosphere ◽  
New Particle Formation ◽  
Marginal Seas ◽  
Range Transport ◽  
New Particles

Abstract. To study the particle number concentration, size distribution and new particle formation (NPF) events in marine atmosphere, we made measurements during six cruise campaigns over the marginal seas of China in 2011–2016 and one campaign from the marginal seas to the Northwest Pacific Ocean (NWPO) in 2014. We observed relatively frequent NPF events in the atmosphere over the marginal seas of China, i.e., 23 out of 126 observational days with the highest occurrence frequency in fall, followed by spring and summer. 22 out of 23 NPF events were analyzed to be associated with the long-range transport of continental pollutants based on 24-hr air mass back trajectories and the preexisting particle number concentrations largely exceeding the clean marine background, leaving one much weaker NPF event to be likely induced by oceanic precursors alone and supported by multiple independent evidences. Although the long-range transport signal of continental pollutants can be clearly observed in the remote marine atmosphere over the NWPO, NPF events were observed only in 2 days out of 36 days. The nucleation mode particles ( 8 cm−3 s−1. The possible mechanisms were argued in terms of roles of different vapor precursors. We also found a ceiling existing for the growth of new particles from 10 nm to larger size in most of NPF events. We thereby introduce a term, i.e., the maximum geometric median diameter of new particles (Dpgmax) and correlate it with the growth rate of new particles (GR). A moderately good linear correlation was also obtained between Dpgmax and GR, and only GR larger than 7.9 nm h−1 can lead to new particles growing with Dpgmax beyond 50 nm. Combining simultaneous measurements of the particle number size distributions and cloud condensation nuclei (CCN) at different super saturations (SS), we indeed observed a clear increase in CCN when the Dpg of new particles exceeded 50 nm at SS = 0.4 %. However, it was not the case for SS = 0.2 %. Consistent with previous studies in continental atmosphere, our results implied that 50 nm can be used as the threshold for new particles to be activated as CCN in the marine atmosphere. Moreover, the κ decreased from 0.4 to 0.1 during the growth period of new particles, implying that organics likely overwhelmed the growth of new particle to CCN size. The chemical analysis of nano-MOUDI samples revealed TMA and oxalic acid may play the important role in the growth of new particles.

scholarly journals Source apportionment and impact of long-range transport on carbonaceous aerosol particles in central Germany during HCCT-2010

2021 ◽  
Vol 21 (5) ◽  
pp. 3667-3684
Author(s):  
Laurent Poulain ◽  
Benjamin Fahlbusch ◽  
Gerald Spindler ◽  
Konrad Müller ◽  
Dominik van Pinxteren ◽  
...  
Keyword(s):  
Black Carbon ◽  
Long Range ◽  
Biomass Burning ◽  
Mass Concentration ◽  
Carbonaceous Aerosol ◽  
Long Range Transport ◽  
Air Masses ◽  
Central Germany ◽  
Range Transport ◽  
Local Emissions

Abstract. The identification of different sources of the carbonaceous aerosol (organics and black carbon) was investigated at a mountain forest site located in central Germany from September to October 2010 to characterize incoming air masses during the Hill Cap Cloud Thuringia 2010 (HCCT-2010) experiment. The near-PM1 chemical composition, as measured by a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS), was dominated by organic aerosol (OA; 41 %) followed by sulfate (19 %) and nitrate (18 %). Source apportionment of the OA fraction was performed using the multilinear engine (ME-2) approach, resulting in the identification of the following five factors: hydrocarbon-like OA (HOA; 3 % of OA mass), biomass burning OA (BBOA; 13 %), semi-volatile-like OA (SV-OOA; 19 %), and two oxygenated OA (OOA) factors. The more oxidized OOA (MO-OOA, 28 %) was interpreted as being influenced by aged, polluted continental air masses, whereas the less oxidized OOA (LO-OOA, 37 %) was found to be more linked to aged biogenic sources. Equivalent black carbon (eBC), measured by a multi-angle absorption photometer (MAAP) represented 10 % of the total particulate matter (PM). The eBC was clearly associated with HOA, BBOA, and MO-OOA factors (all together R2=0.83). Therefore, eBC's contribution to each factor was achieved using a multi-linear regression model. More than half of the eBC (52 %) was associated with long-range transport (i.e., MO-OOA), whereas liquid fuel eBC (35 %) and biomass burning eBC (13 %) were associated with local emissions, leading to a complete apportionment of the carbonaceous aerosol. The separation between local and transported eBC was well supported by the mass size distribution of elemental carbon (EC) from Berner impactor samples. Air masses with the strongest marine influence, based on back trajectory analysis, corresponded with a low particle mass concentration (6.4–7.5 µg m−3) and organic fraction (≈30 %). However, they also had the largest contribution of primary OA (HOA ≈ 4 % and BBOA 15 %–20 %), which was associated with local emissions. Continental air masses had the highest mass concentration (11.4–12.6 µg m−3), and a larger fraction of oxygenated OA (≈45 %) indicated highly processed OA. The present results emphasize the key role played by long-range transport processes not only in the OA fraction but also in the eBC mass concentration and the importance of improving our knowledge on the identification of eBC sources.

scholarly journals Source apportionment and impact of long-range transport on carbonaceous aerosol particles in Central Germany during HCCT-2010

2020 ◽  
Author(s):  
Laurent Poulain ◽  
Benjamin Fahlbusch ◽  
Gerald Spindler ◽  
Konrad Müller ◽  
Dominik van Pinxteren ◽  
...  
Keyword(s):  
Black Carbon ◽  
Long Range ◽  
Biomass Burning ◽  
Mass Concentration ◽  
Carbonaceous Aerosol ◽  
Long Range Transport ◽  
Air Masses ◽  
Central Germany ◽  
Range Transport ◽  
Local Emissions

Abstract. The identification of different sources of the carbonaceous aerosol (organics and black carbon) was investigated at a mountain forest site located in central Germany from September to October 2010 to characterize incoming air masses during the Hill Cap Cloud Thuringia 2010 (HCCT-2010) experiment. The near-PM1 chemical composition, as measured by an Aerosol Mass Spectrometer (HR-ToF-AMS), was dominated by organics (OA, 41 %), followed by sulfate (19 %) and nitrate (18 %). Source apportionment of the OA fraction was performed using the Multilinear Engine approach (ME-2), resulting in the identification of five factors: Hydrocarbon-like OA (HOA, 3 % of OA mass), biomass burning OA (BBOA, 13 %), semi-volatile-like OA (SVOOA, 19 %), and two oxygenated OA (OOA) factors. The more-oxidized OOA (MO-OOA, 28 %) was interpreted as being influenced by aged polluted continental air masses, whereas the less-oxidized OOA (LO-OOA, 37 %) was found to be more linked to aged biogenic sources. Equivalent black carbon (eBC) measured by a multi-angle absorption photometer, MAAP, represented 10 % of the total PM. The eBC was clearly associated with the three factors HOA, BBOA, and MO-OOA (all together R2 = 0.83). Therefore, eBC's contribution to each factor was achieved using a multi-linear regression model. More than half of the eBC (52 %) was associated with long-range transport (i.e. MO-OOA), whereas liquid fuel eBC (35 %) and biomass burning eBC (13 %) were associated with local emissions leading to a complete apportionment of the carbonaceous aerosol. The separation between local and transported eBC was well supported by the mass size distribution of elemental carbon (EC) from Berner-impactor samples. Air masses with the strongest marine influence based on back trajectory analysis corresponded with a low particle mass concentration (6.4–7.5 µg m−3) and organic fraction (≈ 30 %). However, they also had the largest contribution of primary OA (HOA ≈ 4 % and BBOA 15–20 %), which was associated with local emissions. Continental air masses had the highest mass concentration (11.4–12.6 µg m−3) and a larger fraction of oxygenated OA (≈ 45 %) indicated highly processed OA. The present results emphasize the key role played by long-range transport processes not only on the OA fraction but also on the eBC mass concentration and the importance of improving our knowledge on the identification of eBC sources.

scholarly journals First simultaneous measurements of peroxyacetyl nitrate (PAN) and ozone at Nam Co in the central Tibetan Plateau: impacts from the PBL evolution and transport processes

2017 ◽  
Author(s):  
Xiaobin Xu ◽  
Hualong Zhang ◽  
Weili Lin ◽  
Ying Wang ◽  
Shihui Jia
Keyword(s):  
Long Range ◽  
Early Morning ◽  
Diurnal Variations ◽  
Long Range Transport ◽  
Nam Co ◽  
Monsoon Period ◽  
Air Masses ◽  
Upper Troposphere ◽  
Central Tibetan Plateau ◽  
Range Transport

Abstract. Both peroxyacetyl nitrate (PAN) and ozone (O3) are key photochemical products in the atmosphere. Most of the previous in-situ observations of both gases have been made in polluted regions and at low altitude sites. Here we present first simultaneous measurements of PAN and O3 at Nam Co (NMC, 90°57′ E, 30°46′ N, 4745 m  a.s.l.), a remote site in the central Tibetan Plateau (TP). The observations were made during summer periods in 2011 and 2012. The PAN concentrations averaged 0.36 ppb (range: 0.11–0.76 ppb) and 0.44 ppb (range: 0.21–0.99 ppb) during 16–25 August 2011 and 15 May to 13 July 2012, respectively. The O3 concentration varied from 27.9 ppb to 96.4 ppb, with an average of 60.0 ppb. Profound diurnal cycles of PAN and O3 were observed, with minimum values around 05:00 LT, steep rises in the early morning, and broader platforms of high values during 09:00–20:00 LT. We find that the evolution of planetary boundary layer (PBL) played a key role in shaping the diurnal patterns of both gases, particularly the rapid increases of PAN and O3 in the early morning. Air entrainment from the free troposphere into the PBL seemed to cause the early morning increase and be a key factor of sustaining the daytime high concentrations of both gases. The days with higher daytime PBL (about 3 km) showed stronger diurnal variations of both gases and were mainly distributed in the drier pre-monsoon period, while those with shallower daytime PBL (about 2 km) showed minor diurnal variations of both gases and were mainly distributed in the humid monsoon period. Episodes of higher PAN levels were observed occasionally at NMC. These PAN episodes were caused either by rapid downward transport of air masses from the middle/upper troposphere or by long-range transport of PAN plumes from North India. The PAN level in the downward transport cases ranged from 0.5 ppb to 0.7 ppb and may indicate the PAN abundance in the middle/upper troposphere. In the long-range transport case, the PAN level varied in the range of 0.6–1.0 ppb. This long-range transport process influenced most of the western and central TP region for about a week in early June 2012. Our results suggest that polluted air masses from South Asia can significantly enhance the PAN level over the TP. As PAN act as a reservoir of NOx, the impacts of pollution transport from South Asia on tropospheric photochemistry over the TP region deserve further studies.

Radioactivity measurements in the atmosphere and water column of Rogoznica Lake (central Adriatic)

2021 ◽  
Author(s):  
Ivana Tucaković ◽  
Sarah Mateša ◽  
Ivana Coha ◽  
Marija Marguš ◽  
Milan Čanković ◽  
...  
Keyword(s):  
Water Column ◽  
Long Range ◽  
Lake Water ◽  
Dry Deposition ◽  
Long Range Transport ◽  
Atmospheric Input ◽  
Air Masses ◽  
Activity Concentrations ◽  
Range Transport ◽  
Radionuclide Activity

<p>Croatian Science Foundation MARRES project (MARine lake (Rogoznica) as a model for EcoSystem functioning in a changing environment) aims to investigate the unique environment (slow exchange of seawater with the sea; atmospheric input is the only source of freshwater) of the marine lake which is an example of highly stratified (permanent anoxia bellow 9 m depth), and by climate changes affected marine system in the middle of the eastern Adriatic coast (43.53° N, 15.95° E). The area of the lake is characterized by the extensive tourism and mariculture, and the low impact of local industrial activities. It is also affected by the combined influence of long-range transport of air masses and local emissions (open-fire events).</p><p>An important part of the project is focused on the exchange and interaction between atmosphere, water column and sediment by measuring the atmospheric input (wet and dry deposition) of sulphur compounds, organic carbon, trace metals and radionuclides (Be-7, Pb-210).</p><p>This work for the first time will present the current state of the measurements of radioactivity in the Rogoznica lake area, including samples of aerosol particulate matter, PM2.5 < 2.5 um, rainwater and lake water column. Namely, the concentrations of Be-7 and Pb-210 in PM2.5 are measured to determine and correlate the dynamics of particle transport, meteorological information, especially origin of air masses and seasonal variation of PM2.5. While presence of Be-7 indicates the recent wet or dry deposition from the upper parts of the atmosphere, Pb-210 may be used as a tracer for continental air masses. Therefore, it can also indicate the influence of the pollution induced by human activity. Regarding that, special attention will be paid to compare results before and during the Covid-19 lockdown periods.</p><p>So far, preliminary results do not show significant difference in PM2.5 masses and measured radionuclide activity concentrations for the lockdown period. Be-7 and Pb-210 were regularly detected in aerosols collected on a glass fiber filters during a one-week sampling periods with the air flow rate of 2.3 m<sup>3</sup>/h. Their activity concentrations are determined by gamma spectrometry using High Purity Germanium detectors. The results are found to be correlated with PM2.5 masses, ranging from 2.9 to 12.2 Bq/m<sup>3</sup> for Be-7 and from 0.5 to 2.5 Bq/m<sup>3</sup> for Pb-210. First analyses show that the highest values can be related to the long-range transport of air masses and to the recorded near open-fire event. As expected, Be-7 is also detected in almost every rainwater sample (event), with the activity concentration up to 5.6 Bq/L, while low activities of Pb-210 are detected only sporadically. Related to that, Be-7 is detected in lake water column as well, but only in the surface layer and in samples collected during, or immediately after the rain events. </p><p>Dynamics and seasonal variation of radionuclide activity concentrations in here studied samples will be discussed, and the relationships with some meteorological parameters (temperature, wind speed, relative humidity, precipitation level) as well as local and long-range transport and physico-chemical conditions in the lake water column will be established.</p>

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