scholarly journals Chemical composition of PM<sub>10</sub> and PM<sub>1</sub> at the high-altitude Himalayan station Nepal Climate Observatory-Pyramid (NCO-P) (5079 m a.s.l.)

2010 ◽  
Vol 10 (10) ◽  
pp. 4583-4596 ◽  
Author(s):  
S. Decesari ◽  
M. C. Facchini ◽  
C. Carbone ◽  
L. Giulianelli ◽  
M. Rinaldi ◽  
...  
Keyword(s):  
Organic Matter ◽  
Chemical Composition ◽  
High Altitude ◽  
Seasonal Cycle ◽  
Mineral Dust ◽  
Indian Subcontinent ◽  
Monsoon Season ◽  
Moist Convection ◽  
Anthropogenic Aerosols ◽  
High Himalayas

Abstract. We report chemical composition data for PM10 and PM1 from the Nepal Climate Observatory-Pyramid (NCO-P), the world's highest aerosol observatory, located at 5079 m a.s.l. at the foothills of Mt. Everest. Despite its high altitude, the average PM10 mass apportioned by the chemical analyses is of the order of 6 μg m−3 (i.e., 10 μg/scm), with almost a half of this mass accounted for by organic matter, elemental carbon (EC) and inorganic ions, the rest being mineral dust. Organic matter, in particular, accounted for by 2.0 μg m−3 (i.e., 3.6 μg/scm) on a yearly basis, and it is by far the major PM10 component beside mineral oxides. Non-negligible concentrations of EC were also observed (0.36 μg/scm), confirming that light-absorbing aerosol produced from combustion sources can be efficiently transported up the altitudes of Himalayan glaciers. The concentrations of carbonaceous and ionic aerosols follow a common time trend with a maximum in the premonsoon season, a minimum during the monsoon and a slow recovery during the postmonsoon and dry seasons, which is the same phenomenology observed for other Nepalese Himalayan sites in previous studies. Such seasonal cycle can be explained by the seasonal variations of dry and moist convection and of wet scavenging processes characterizing the climate of north Indian subcontinent. We document the effect of orographic transport of carbonaceous and sulphate particles upslope the Himalayas, showing that the valley breeze circulation, which is almost permanently active during the out-of-monsoon season, greatly impacts the chemical composition of PM10 and PM1 in the high Himalayas and provides an efficient mechanism for bringing anthropogenic aerosols into the Asian upper troposphere (>5000 m a.s.l.). The concentrations of mineral dust are impacted to a smaller extent by valley breezes and follow a unique seasonal cycle which suggest multiple source areas in central and south-west Asia. Our findings, based on two years of observations of the aerosol chemical composition, provide clear evidence that the southern side of the high Himalayas is impacted by transport of anthropogenic aerosols which constitute the Asian brown cloud.

scholarly journals Chemical composition of PM<sub>10</sub> and PM<sub>1</sub> at the high-altitude Himalayan station Nepal Climate Observatory-Pyramid (NCO-P) (5079 m a.s.l.)

2009 ◽  
Vol 9 (6) ◽  
pp. 25487-25522 ◽  
Author(s):  
S. Decesari ◽  
M. C. Facchini ◽  
C. Carbone ◽  
L. Giulianelli ◽  
M. Rinaldi ◽  
...  
Keyword(s):  
Organic Matter ◽  
Chemical Composition ◽  
High Altitude ◽  
Seasonal Cycle ◽  
Mineral Dust ◽  
Monsoon Season ◽  
Optically Active ◽  
Moist Convection ◽  
Anthropogenic Aerosols ◽  
High Himalayas

Abstract. We report chemical composition data for PM10 and PM1 from the Nepal Climate Observatory-Pyramid (NCO-P), the world's highest aerosol observatory, located at 5079 m a.s.l. at the foothills of Mt. Everest. Despite its high altitude, the average PM10 mass apportioned by the chemical analyses is of the order of 6 μg m−3 (i.e., 10 μg/scm), with almost a half of this mass accounted for by organic matter, elemental carbon (EC) and inorganic ions, the rest being mineral dust. Organic matter, in particular, accounted for by 2.0 μg m−3 (i.e., 3.6 μg/scm) on a yearly basis, and it is by far the major PM10 component beside mineral oxides. Non-negligible concentrations of EC were also observed (0.36 μg/scm), confirming that optically-active aerosol produced from combustion sources can be efficiently transported up the altitudes of Himalayan glaciers. The concentrations of carbonaceous and ionic aerosols follow a common time trend with a maximum in the premonsoon season, a minimum during the monsoon and a slow "ramp-up" period in the postmonsoon and dry seasons, which is the same phenomenology observed for other Nepalese Himalayan sites in previous studies. Such seasonal cycle can be explained by the seasonal variations of dry and moist convection and of wet scavenging processes characterizing the climate of north Indian subcontinent. We document the effect of orographic transport of carbonaceous and sulphate particles upslope the Himalayas, showing that the valley breeze circulation, which is almost permanently active during the out-of-monsoon season, greatly impacts the chemical composition of PM10 and PM1 in the high Himalayas and provides an efficient mechanism for bringing anthropogenic optically-active aerosols into the Asian upper troposphere (>5000 m a.s.l.). The concentrations of mineral dust are impacted to a smaller extent by valley breezes and follow a unique seasonal cycle which suggest multiple source areas in central and south-west Asia. Our findings, based on two years of observations of the aerosol chemical composition, provide clear evidence that the southern side of the high Himalayas are impacted by transport of anthropogenic aerosols which constitute the Asian brown cloud.

scholarly journals First insights into northern Africa high-altitude background aerosol chemical composition and source influences

2021 ◽  
Vol 21 (24) ◽  
pp. 18147-18174
Author(s):  
Nabil Deabji ◽  
Khanneh Wadinga Fomba ◽  
Souad El Hajjaji ◽  
Abdelwahid Mellouki ◽  
Laurent Poulain ◽  
...  
Keyword(s):  
Organic Matter ◽  
Chemical Composition ◽  
High Altitude ◽  
North Africa ◽  
Mineral Dust ◽  
Water Soluble ◽  
Atmospheric Composition ◽  
Chemical Compositions ◽  
Aerosol Composition ◽  
Aerosol Chemical Composition

Abstract. Field measurements were conducted to determine aerosol chemical composition at a newly established remote high-altitude site in North Africa at the Atlas Mohammed V (AMV) atmospheric observatory located in the Middle Atlas Mountains. The main objectives of the present work are to investigate the variations in the aerosol composition and better assess global and regional changes in atmospheric composition in North Africa. A total of 200 particulate matter (PM10) filter samples were collected at the site using a high-volume (HV) collector in a 12 h sampling interval from August to December 2017. The chemical composition of the samples was analyzed for trace metals, water-soluble ions, organic carbon (OC/EC), aliphatic hydrocarbons, and polycyclic aromatic hydrocarbon (PAH) contents. The results indicate that high-altitude aerosol composition is influenced by both regional and transregional transport of emissions. However, local sources play an important role, especially during low wind speed periods, as observed for November and December. During background conditions characterized by low wind speeds (avg. 3 m s-1) and mass concentrations in the range from 9.8 to 12 μg m-3, the chemical composition is found to be dominated by inorganic elements, mainly suspended dust (61 %) and ionic species (7 %), followed by organic matter (7 %), water content (12 %), and unidentified mass (11 %). Despite the proximity of the site to the Sahara, its influence on the atmospheric composition at this high-altitude site was mainly seasonal and accounted for only 22 % of the sampling duration. Biogenic organics contributed up to 7 % of the organic matter with high contributions from compounds such as heneicosane, hentriacontane, and nonacosane. The AMV site is dominated by four main air mass inflows, which often leads to different aerosol chemical compositions. Mineral dust influence was seasonal and ranged between 21 % and 74 % of the PM mass, with peaks observed during the summer, and was accompanied by high concentrations of SO42- of up to 3.0 μg m-3. During winter, PM10 concentrations are low (<30 μg m-3), the influence of the desert is weaker, and the marine air masses (64 %) are more dominant with a mixture of sea salt and polluted aerosol from the coastal regions (Rabat and Casablanca). During the daytime, mineral dust contribution to PM increased by about 42 % because of road dust resuspension. In contrast, during nighttime, an increase in the concentrations of alkanes, PAHs, alkane-2-ones, and anthropogenic metals such as Pb, Ni, and Cu was found due to variations in the boundary layer height. The results provide the first detailed seasonal and diurnal variation of the aerosol chemical composition, which is valuable for long-term assessment of climate and regional influence of air pollution in North Africa.

scholarly journals First insights into Northern Africa high-altitude background aerosol chemical composition and source influences

2021 ◽  
Author(s):  
Nabil Deabji ◽  
Khanneh Wadinga Fomba ◽  
Souad El Hajjaji ◽  
Abdelwahid Mellouki ◽  
Hartmut Herrmann
Keyword(s):  
Organic Matter ◽  
Chemical Composition ◽  
High Altitude ◽  
Field Measurements ◽  
High Volume ◽  
Ionic Species ◽  
Atmospheric Composition ◽  
Chemical Compositions ◽  
Aerosol Composition ◽  
Aerosol Chemical Composition

Abstract. Field measurements were conducted to determine aerosol chemical composition in a newly established remote high-altitude site in North Africa to investigate the variations in aerosol composition useful in assessing global and regional changes in atmospheric composition. Particulate matter (PM10) filter samples (200) were collected at the Atlas Mohammed V atmospheric observatory (AM5) located in the Middle-Atlas Mountains in Morocco using a high-volume (HV) collector in a 12 h sampling interval from August to December 2017. The chemical composition of the samples was analyzed for trace metals, ions, elemental carbon, organic carbon, aliphatic hydrocarbons, and polycyclic aromatic hydrocarbon (PAHs) content. The results indicate that high-altitudes aerosol composition is influenced by both regional as well as trans-regional transport of emissions. However, local sources play an important role, especially during low wind speed periods, as observed for November and December. Despite the proximity of the site to the Sahara Desert, its influence on the atmospheric composition at this high-altitude site was mainly seasonal and accounted for only 14 % of the sampling duration. Background conditions at this remote site are characterized by low wind speeds (Av. 2.5 m/s) and mass concentrations in the range of 9.8 and 20 µg/m3. The chemical composition is found to be dominated by inorganic elements, mainly suspended dust (47 %) and ionic species (16 %), followed by organic matter (15 %), water content (12 %), and indeterminate mass (9 %). Biogenic organics contributed up to 7 % of the organic matter with high contributions from compounds such as Nonacosane, Heptacosane, and 2-Pentadecanone. The AM5 site is dominated by four main air mass inflow, which often leads to different aerosol chemical compositions. Mineral dust influenced was seasonal and ranged between 20 and 70 % of the PM mass with peaks observed during the summer and was accompanied by high concentrations of SO42− of up to 1.3 µg/m3. During winter, PM10 concentrations are low (

Aerosol chemical composition of the middle Atlas region of North Africa

2021 ◽  
Author(s):  
Nabil Deabji ◽  
Khanneh Wadinga Fomba ◽  
Souad El Hajjaji ◽  
Abdelwahid Mellouki ◽  
Hartmut Herrmann
Keyword(s):  
Boundary Layer ◽  
Organic Matter ◽  
Chemical Composition ◽  
High Altitude ◽  
North Africa ◽  
Atmospheric Composition ◽  
North African ◽  
Air Masses ◽  
Middle Atlas ◽  
Aerosol Chemical Composition

&lt;p&gt;Mountain and high-altitude sites provide representative data for the lower free troposphere and various pathways for aerosol interactions, changing boundary layer heights useful in understanding atmospheric composition. However, few studies exist in African regions despite its diversity in both natural and anthropogenic emissions. For this reason, the ATLAS Mohamed V (AM5) observatory in the Middle Atlas region was established to provide the necessary infrastructure for detailed atmospheric studies in the North African high-altitude region. Here, results of a field study conducted to determine the aerosol chemical composition in this region, understand its variations, and importance in assessing global and regional changes in the atmospheric composition is reported. Particulate matter (PM&lt;sub&gt;10&lt;/sub&gt;) filter samples (200) were collected using a high-volume (500l/min) collector in a 12h sampling interval from August to December 2017. The chemical composition of the samples was analyzed for trace metals, ions, elemental carbon, organic carbon, aliphatic hydrocarbons, and polycyclic aromatic hydrocarbon (PAHs) content. The results show that the high-altitude aerosol composition is influenced by regional and transregional transport of different pollutants. Local sources play an important role during periods when the wind speed is low, especially during autumn. Despite the proximity of the site to the Saharan Desert, its influence on the atmospheric composition was mainly seasonal and accounted for only 14% of the sampling duration. The chemical composition was dominated by inorganic elements, mainly suspended dust (47%) and ionic species (16%), and followed by organic matter (15%), water content (12%), and indeterminate mass (9%). Biogenic organics contributed up to 7% of the organic matter with high contributions from compounds such as Nonacosane, Heptacosane, and 2-Pentadecanone. Four main air masses characterized the inflow to the site, which often leads to different aerosol chemical compositions. Mineral dust influenced was seasonal and ranged between 20 and 70% of the PM mass with peaks observed during the summer and was accompanied by high concentrations of SO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;2-&lt;/sup&gt; of up to 1.3 &amp;#181;g/m&amp;#179;. PM&lt;sub&gt;10&lt;/sub&gt; concentrations during winter were low (&lt; 30 &amp;#181;g/m&amp;#179;), with a dominance of marine air masses (53%) carrying aerosols rich in sea salt and polluted anthropogenic aerosols from the coastal regions (Rabat and Casablanca). During the day-time, mineral dust contribution to PM increased by about 42% due to road dust resuspension. In contrast, during night-time, an increase in the concentrations of PAHs, ketones, and anthropogenic metals such as Pb, Ni, and Cu was found due to variations in the boundary layer height. The results provide first insights into typical North African high-altitude background aerosol chemical composition useful for long-term assessment of climate and regional influence of air pollution in North Africa.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

Chemical composition of cover crops and soil organic matter pools in no‐tillage systems in the Cerrado

2021 ◽  
Author(s):  
Arminda Moreira de Carvalho ◽  
Luana Ramos Passos Ribeiro ◽  
Robélio Leandro Marchão ◽  
Alexsandra Duarte de Oliveira ◽  
Karina Pulrolnik ◽  
...  
Keyword(s):  
Organic Matter ◽  
Chemical Composition ◽  
Soil Organic Matter ◽  
Cover Crops ◽  
No Tillage ◽  
Tillage Systems

scholarly journals Synoptic Preconditions for Extreme Flooding during the Summer Asian Monsoon in the Mumbai Area

2014 ◽  
Vol 15 (1) ◽  
pp. 229-242 ◽  
Author(s):  
Marco Lomazzi ◽  
Dara Entekhabi ◽  
Joaquim G. Pinto ◽  
Giorgio Roth ◽  
Roberto Rudari
Keyword(s):  
Time Series ◽  
South Asian ◽  
Asian Monsoon ◽  
Indian Subcontinent ◽  
Monsoon Season ◽  
Value Added ◽  
South Asian Monsoon ◽  
Flood Events ◽  
The South ◽  
Synoptic Conditions

Abstract The summer monsoon season is an important hydrometeorological feature of the Indian subcontinent and it has significant socioeconomic impacts. This study is aimed at understanding the processes associated with the occurrence of catastrophic flood events. The study has two novel features that add to the existing body of knowledge about the South Asian monsoon: 1) it combines traditional hydrometeorological observations (rain gauge measurements) with unconventional data (media and state historical records of reported flooding) to produce value-added century-long time series of potential flood events and 2) it identifies the larger regional synoptic conditions leading to days with flood potential in the time series. The promise of mining unconventional data to extend hydrometeorological records is demonstrated in this study. The synoptic evolution of flooding events in the western-central coast of India and the densely populated Mumbai area are shown to correspond to active monsoon periods with embedded low pressure centers and have far-upstream influences from the western edge of the Indian Ocean basin. The coastal processes along the Arabian Peninsula where the currents interact with the continental shelf are found to be key features of extremes during the South Asian monsoon.

Effects of climate change on soil organic matter chemical composition and carbon content in different physical fractions

2021 ◽  
Author(s):  
Moritz Mohrlok ◽  
Victoria Martin ◽  
Alberto Canarini ◽  
Wolfgang Wanek ◽  
Michael Bahn ◽  
...  
Keyword(s):  
Climate Change ◽  
Organic Matter ◽  
Chemical Composition ◽  
Soil Organic Matter ◽  
Soil C ◽  
Size Classes ◽  
Soil Fractions ◽  
Total Soil ◽  
C And N ◽  
Amp Clay

&lt;p&gt;Soil organic matter (SOM) is composed of many pools with different properties (e.g. turnover times) which are generally used in biogeochemical models to predict carbon (C) dynamics. Physical fractionation methods are applied to isolate soil fractions that correspond to these pools. This allows the characterisation of chemical composition and C content of these fractions. There is still a lack of knowledge on how these individual fractions are affected by different climate change drivers, and therefore the fate of SOM remains elusive. We sampled soils from a multifactorial climate change experiment in a managed grassland in Austria four years after starting the experiment to investigate the response of SOM in physical soil fractions to temperature (eT: ambient and elevated by +3&amp;#176;C), atmospheric CO&lt;sub&gt;2&lt;/sub&gt;-concentration (eCO&lt;sub&gt;2&lt;/sub&gt;: ambient and elevated by +300 ppm) and to a future climate treatment (eT x eCO&lt;sub&gt;2&lt;/sub&gt;: +3&amp;#176;C and + 300 ppm). A combination of slaking and wet sieving was used to obtain three size classes: macro-aggregates (maA, &gt; 250 &amp;#181;m), micro-aggregates (miA, 63 &amp;#181;m &amp;#8211; 250 &amp;#181;m) and free silt &amp; clay (sc, &lt; 63 &amp;#181;m). In both maA and miA, four different physical OM fractions were then isolated by density fractionation (using sodium polytungstate of &amp;#961; = 1.6 g*cm&lt;sup&gt;-3&lt;/sup&gt;, ultrasonication and sieving): Free POM (fPOM), intra-aggregate POM (iPOM), silt &amp; clay associated OM (SCaOM) and sand-associated OM (SaOM). We measured C and N contents and isotopic composition by EA-IRMS in all fractions and size classes and used a Pyrolysis-GC/MS approach to assess their chemical composition. For eCO&lt;sub&gt;2&lt;/sub&gt; and eT x eCO&lt;sub&gt;2 &lt;/sub&gt;plots, an isotope mixing-model was used to calculate the proportion of recent C derived from the elevated CO&lt;sub&gt;2 &lt;/sub&gt;treatment. Total soil C and N did not significantly change with treatments.&amp;#160; eCO&lt;sub&gt;2&lt;/sub&gt; decreased the relative proportion of maA-mineral-associated C and increased C in fPOM and iPOM. About 20% of bulk soil C was represented by the recent C derived from the CO&lt;sub&gt;2&lt;/sub&gt; fumigation treatment. This significantly differed between size classes and density fractions (p &lt; 0.001), which indicates inherent differences in OM age and turnover. Warming reduced the amount of new C incorporated into size classes. We found that each size class and fraction possessed a unique chemical fingerprint, but this was not significantly changed by the treatments. Overall, our results show that while climate change effects on total soil C were not significant after 4 years, soil fractions showed specific effects. Chemical composition differed significantly between size classes and fractions but was unaffected by simulated climate change. This highlights the importance to separate SOM into differing pools, while including changes to the molecular composition might not be necessary for improving model predictions.&amp;#160;&amp;#160;&amp;#160;&amp;#160;&lt;/p&gt;

Implications of aerosol-induced snow darkening on regional hydroclimate over the Himalayas

2021 ◽  
Author(s):  
Vijayakumar Sivadasan Nair ◽  
Usha Keshav Hasyagar ◽  
Surendran Nair Suresh Babu
Keyword(s):  
South Asia ◽  
Climate Model ◽  
Hydrological Cycle ◽  
Monsoon Season ◽  
Radiation Balance ◽  
Western Himalayas ◽  
Radiative Effect ◽  
Anthropogenic Aerosols ◽  
Snow Albedo ◽  
Snow Cover Extent

&lt;p&gt;The snow-covered mountains of Himalayas are known to play a crucial role in the hydrology of South Asia and are known as the &amp;#8220;Asian water tower&amp;#8221;. Despite the high elevations, the transport of anthropogenic aerosols from south Asia and desert dust from west Asia plays a significant role in directly and indirectly perturbing the radiation balance and hydrological cycle over the region. Absorbing aerosols like black carbon (BC) and dust deposited on the snow surface reduces the albedo of the Himalayan snow significantly (snow darkening or snow albedo effect). Using a Regional Climate Model (RegCM-4.6.0) coupled with SNow, ICe and Aerosol Radiation (SNICAR) module, the implications of aerosol-induced snow darkening on the regional hydroclimate of the Himalayas are investigated in this study. The aerosols deposited on snow shows a distinct regional heterogeneity. The albedo reduction due to aerosols shows a west to east gradient during pre-monsoon season and this results in the positive radiative effect of about 29 Wm&lt;sup&gt;-2&lt;/sup&gt;, 17 Wm&lt;sup&gt;-2&lt;/sup&gt; and 5 Wm&lt;sup&gt;-2&lt;/sup&gt; over western, central and eastern Himalayas respectively. The reduction in the snow albedo also results in the sign reversal of the aerosol direct radiative effect i.e., from warming to cooling at the top of the atmosphere during pre-monsoon season. The excess solar energy trapped at the surface due to snow darkening warms the surface (0.66-1.9 K) and thus decreases the snow cover extent significantly. This results in the reduction of the number of snow-covered days by more than a month over the western Himalayas and about 10 &amp;#8211; 15 days over the central Himalayas. The early snowmelt due to aerosol-induced snow darkening results in the increase of runoff throughout the melting season. Therefore, the present study highlights the heterogeneous response of aerosol induced snow albedo feedbacks over the Himalayan region and its impact on the snowpack and hydrology, which has further implications on the freshwater availability over the region.&lt;/p&gt;

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