Air Mass Trajectory Analysis Research Articles

Characterization and bioavailability of rainwater dissolved organic matter at the southeast coast of China using absorption spectroscopy and fluorescence EEM-PARAFAC

Rainwater brings considerable amounts of dissolved organic matter (DOM) from atmosphere to freshwater and marine environments, but little is known about the chemical composition and bioavailability of rainwater DOM. The quantity, quality, and bioavailability of DOM were investigated for 21 rain events at a coastal site in southeast China, using dissolved organic carbon (DOC) measurements, absorption spectroscopy, and fluorescence excitation-emission matrices-parallel factor analysis (EEM-PARAFAC). The DOC concentration ranged from 35 to 457 μM, which was affected by the prevailing monsoon, rainfall amount and terrestrial/anthropogenic inputs. The volume-weighted average DOC was 118 μM, corresponding to a rainwater DOC flux of 1.98 g m−2 yr−1. Four fluorescent components were identified with EEM-PARAFAC, including three humic-like components (C1-C3) and one tyrosine-like component C4. Absorption coefficient (aCDOM(300)) and fluorescence intensities of C2-C4 strongly correlated with DOC, indicating they can be used for DOC estimation. Rainwater DOM was characterized by low DOC-specific UV absorbance (SUVA254) and humification index (HIX), which indicated a low aromaticity and humification degree. Principal component analysis (PCA) based on DOM indices revealed two principal factors, which were related to the DOM concentration and humification degree respectively. PCA, together with air-mass trajectory analysis, successfully separated different rain events with variable inputs from living plants/local sources, soil organic matter/humified materials, and the marine source. Rainwater DOM generally showed a high bioavailability of 50% ± 19%, with higher degradability of non-chromophoric constituents and C1-C2 than other components. This study demonstrated the applicability of absorption and EEM-PARAFAC combined with PCA and air-mass trajectory analysis in differentiating rain events and tracking organic matter sources, and revealed different effects of microbial degradation on individual PARAFAC components in rainwater.

Burning-derived vanillic acid in an Arctic ice core from Tunu, northeastern Greenland

Abstract. In this study, vanillic acid was measured in the Tunu ice core from northeastern Greenland in samples covering the past 1700 years. Vanillic acid is an aerosol-borne aromatic methoxy acid, produced by the combustion of lignin during biomass burning. Air mass trajectory analysis indicates that North American boreal forests are likely the major source region for biomass burning aerosols deposited to the ice core site. Vanillic acid levels in the Tunu ice core range from < 0.005 to 0.08 ppb. Tunu vanillic acid exhibits centennial-scale variability in pre-industrial ice, with elevated levels during the warm climates of the Roman Warm Period and Medieval Climate Anomaly, and lower levels during the cooler climates of the Late Antique Little Ice Age and the Little Ice Age. Analysis using a peak detection method revealed a positive correlation between vanillic acid in the Tunu ice core and both ammonium and black carbon in the North Greenland Eemian Ice Drilling (NEEM) project ice core from 600 to 1200 CE. The data provide multiproxy evidence of centennial-scale variability in North American high-latitude fire during this time period.

Unexpected Contributions of Sea Spray and Lake Spray Aerosol to Inland Particulate Matter

Sea spray aerosol (SSA) and lake spray aerosol (LSA) from wave breaking contribute to particulate matter (PM) in coastal regions near oceans and freshwater lakes, respectively. However, SSA and LSA contributions to atmospheric aerosol populations in inland regions are poorly understood because of difficulties differentiating them from other inland sources when using bulk particle measurements. Herein, we show that SSA and LSA episodically contribute to atmospheric aerosol populations at a rural site in northern Michigan >700 and >25 km from the nearest seawater and Great Lakes sources, respectively. During July 2014, individual SSA and LSA particles were identified by single-particle mass spectrometry and electron microscopy and then combined with air mass trajectory analysis for source apportionment. SSA comprised up to 33 and 20% of PM mass (0.5–2.0 μm) during two multiday transport events from Hudson Bay and a 3% average background outside these periods. LSA transported from Lake Michigan reached a max...

Tropospheric ozone enhancement during post-harvest crop-residue fires at two downwind sites of the Indo-Gangetic Plain.

In the present study, surface ozone (O3), nitrogen oxides (NOx), and carbon monoxide (CO) levels were measured at two sites downwind of fire active region in the Indo-Gangetic Plain (IGP): Agra (27.16° N, 78.08° E) and Delhi (28.37° N, 77.12° E) to study the impact of post-harvest crop-residue fires. The study period was classified into two groups: Pre-harvest period and Post-harvest period. During the post-harvest period, an enhancement of 17.3 and 31.7ppb in hourly averaged O3 mixing ratios was observed at Agra and Delhi, respectively, under similar meteorological conditions. The rate of change of O3 was also higher in the post-harvest period by 56.2% in Agra and 39.5% in Delhi. Relatively higher O3 episodic days were observed in the post-harvest period. Fire hotspots detected by Moderate Resolution Imaging Spectroradiometer (MODIS) along with backward air-mass trajectory analysis suggested that the enhanced O3 and CO levels at the study sites during the post-harvest period could be attributed to crop-residue burning over the North-West IGP (NW-IGP). Satellite observations of surface CO mixing ratios and tropospheric formaldehyde (HCHO) column also showed higher levels during the post-harvest period. Graphical abstract.

Regions of open water and melting sea ice drive new particle formation in North East Greenland

Atmospheric new particle formation (NPF) and growth significantly influences the indirect aerosol-cloud effect within the polar climate system. In this work, the aerosol population is categorised via cluster analysis of aerosol number size distributions (9–915 nm, 65 bins) taken at Villum Research Station, Station Nord (VRS) in North Greenland during a 7 year record (2010–2016). Data are clustered at daily averaged resolution; in total, we classified six categories, five of which clearly describe the ultrafine aerosol population, one of which is linked to nucleation events (up to 39% during summer). Air mass trajectory analyses tie these frequent nucleation events to biogenic precursors released by open water and melting sea ice regions. NPF events in the studied regions seem not to be related to bird colonies from coastal zones. Our results show a negative correlation (r = −0.89) between NPF events and sea ice extent, suggesting the impact of ultrafine Arctic aerosols is likely to increase in the future, given the likely increased sea ice melting. Understanding the composition and the sources of Arctic aerosols requires further integrated studies with joint multi-component ocean-atmosphere observation and modelling.

Seasonal variation and chemical characterization of PM<sub>2.5</sub> in northwestern Philippines

Abstract. The seasonal and chemical characteristics of fine particulate matter (PM2.5) were investigated in Burgos, Ilocos Norte, located at the northwestern edge of the Philippines. Each 24 h sample of fine aerosol was collected for four seasons. Fine particulate in the region shows strong seasonal variation in both concentration and composition. Highest mass concentration was seen during the boreal spring season with a mean mass concentration of 21.6 ± 6.6 µg m−3, and lowest was in fall with a mean concentration of 8.4 ± 2.3 µg m−3. Three-day wind back trajectory analysis of air mass reveals the influence of the northwestern Pacific monsoon regimes on PM2.5 concentration. During southwest monsoon, sea salt was the dominant component of fine aerosols carried by moist air from the South China Sea. During northeast monsoon, on the other hand, both wind and receptor model analysis showed that higher particulate concentration was due to the long-range transport (LRT) of anthropogenic emissions from northern East Asia. Overall, sea salt and soil comprise 33 % of total PM2.5 concentration, while local biomass burning makes up 33 %. LRT of industrial emission, solid waste burning and secondary sulfate from East Asia have a mean contribution of 34 % to the total fine particulate for the whole sampling period.

Analysis of air mass trajectories to explain observed variability of tritium in precipitation at the Southern Sierra Critical Zone Observatory, California, USA

Understanding the behavior of tritium, a radioactive isotope of hydrogen, in the environment is important to evaluate the exposure risk of anthropogenic releases, and for its application as a tracer in hydrology and oceanography. To understand and predict the variability of tritium in precipitation, HYSPLIT air mass trajectories were analyzed for 16 aggregate precipitation samples collected over a 2 year period at irregular intervals at a research site located at 2000 m elevation in the southern Sierra Nevada (California, USA). Attributing the variation in tritium to specific source areas confirms the hypothesis that higher latitude or inland sources bring higher tritium levels in precipitation than precipitation originating in the lower latitude Pacific Ocean. In this case, the source of precipitation accounts for 79% of the variation observed in tritium concentrations. Air mass trajectory analysis is a promising tool to improve the predictions of tritium in precipitation at unmonitored locations and thoroughly understand the processes controlling transport of tritium in the environment.

Early-Holocene greening of the Afro-Asian dust belt changed sources of mineral dust in West Asia

Production, transport and deposition of mineral dust have significant impacts on different components of the Earth systems through time and space. In modern times, dust plumes are associated with their source region(s) using satellite and land-based measurements and trajectory analysis of air masses through time. Reconstruction of past changes in the sources of mineral dust as related to changes in climate, however, must rely on the knowledge of the geochemical and mineralogical composition of modern and paleo-dust, and that of their potential source origins. In this contribution, we present a 13,000-yr record of variations in radiogenic Sr–Nd–Hf isotopes and Rare Earth Element (REE) anomalies as well as dust grain size from an ombrotrophic (rain fed) peat core in NW Iran as proxies of past changes in the sources of dust over the interior of West Asia. Our data shows that although the grain size of dust varies in a narrow range through the entire record, the geochemical fingerprint of dust particles deposited during the low-flux, early Holocene period (11,700–6,000 yr BP) is distinctly different from aerosols deposited during high dust flux periods of the Younger Dryas and the mid-late Holocene (6,000–present). Our findings indicate that the composition of mineral dust deposited at the study site changed as a function of prevailing atmospheric circulation regimes and land exposure throughout the last deglacial period and the Holocene. Simulations of atmospheric circulation over the region show the Northern Hemisphere Summer Westerly Jet was displaced poleward across the study area during the early Holocene when Northern Hemisphere insolation was higher due to the Earth's orbital configuration. This shift, coupled with lower dust emissions simulated based on greening of the Afro-Asian Dust Belt during the early Holocene likely led to potential sources in Central Asia dominating dust export to West Asia during this period. In contrast, the dominant western and southwest Asian and Eastern African sources have prevailed during the mid-Holocene to modern times.

Spatial variation of Aerosol Optical Depth and Solar Irradiance over Delhi -NCR during Summer season

Present study shows the spatial variation of Aerosol Optical Depth (AOD), solar irradiance and their association at the urban and rural sites in Delhi and National Capital Region (NCR) during the summer season of the year 2015. Summer-time AOD data from the NASA’s Terra satellite MODIS sensor has been used to study the spatial distribution of aerosols over Delhi and its surrounding rural area. The ground data for the direct and global solar irradiances was collected over this region at urban and rural locations in Delhi and NCR using a Fieldspec Spectro-radiometer. HYSPLIT model has been used for the air mass trajectory analysis. The AOD values were observed to be higher over Delhi compared to the relatively lower AOD in rural area of NCR. The NCR site observed higher average solar irradiances than Delhi during the summer season. This may be because of the higher aerosol concentration in Delhi as compared to its outskirts. Also, this region is affected by the severe dust storm events during the summer season which further increases the aerosol load in the atmosphere. HYSPLIT results show the influence of western Thar Desert air masses on the Delhi-NCR. Windblown as well anthropogenic aerosols play a major role in scattering and absorption of the incoming solar radiation and hence, in governing the micro-climatology of the region.

Arctic sea ice melt leads to atmospheric new particle formation

Atmospheric new particle formation (NPF) and growth significantly influences climate by supplying new seeds for cloud condensation and brightness. Currently, there is a lack of understanding of whether and how marine biota emissions affect aerosol-cloud-climate interactions in the Arctic. Here, the aerosol population was categorised via cluster analysis of aerosol size distributions taken at Mt Zeppelin (Svalbard) during a 11 year record. The daily temporal occurrence of NPF events likely caused by nucleation in the polar marine boundary layer was quantified annually as 18%, with a peak of 51% during summer months. Air mass trajectory analysis and atmospheric nitrogen and sulphur tracers link these frequent nucleation events to biogenic precursors released by open water and melting sea ice regions. The occurrence of such events across a full decade was anti-correlated with sea ice extent. New particles originating from open water and open pack ice increased the cloud condensation nuclei concentration background by at least ca. 20%, supporting a marine biosphere-climate link through sea ice melt and low altitude clouds that may have contributed to accelerate Arctic warming. Our results prompt a better representation of biogenic aerosol sources in Arctic climate models.

Dew water chemical composition and source characterization in the IGP outflow location (coastal Bhola, Bangladesh)

Dew water samples were collected during the winter season (December, 2014 to January, 2015) at an outflow location from the Indo-Gangetic Plain (IGP) to the Bay of Bengal (Coastal Bhola, Bangladesh). Physical properties of the dew water, including pH and electrical conductivity (EC), were measured. The concentrations of water soluble ions (Cl−, SO4 2−, NO3 −, HCO3 −, Na+, K+, Ca2+, and Mg2+) and trace metals (Zn, Fe, Mn, Cu, Cr, Pd, and Ni) were also measured. Source characterization of the chemical species was done by correlation analysis, enrichment factor analysis, percent source contribution calculation, and air mass trajectory analysis. The average pH and EC of the collected dew water were 6.81 and 154.80 μS cm−1, respectively. The average concentration of SO4 2− and NO3 − was 264.10 and 222.20 μeq L−1, respectively. The concentrations of water soluble ions followed the sequence: Ca2+ > Cl−> SO4 2 > Na+ > NO3 −> Mg2+ > K+ > HCO3 −. The concentrations of trace metals ranged in order with Zn > Fe > Mn > Cu, while the concentrations of Cr, Pb, and Ni were below detection limit in dew water. Regression analysis showed significant correlations among sea, soil, and anthropogenic species. High enrichment factors of SO4 2−, NO3 −, Zn, Mn, and Cu indicates anthropogenic sources. Percent source contribution of different species showed significant anthropogenic contribution for Cl−(1.80%), SO4 2−(83.5%), and NO3 −(99.3%). Air mass trajectory analysis supported that the regional urban pollutions have significant influence on the dew water chemistry at the coastal Bhola, Bangladesh.

Chemical characteristics and source apportionment of PM2.5 using PCA/APCS, UNMIX, and PMF at an urban site of Delhi, India.

The present study investigated the comprehensive chemical composition [organic carbon (OC), elemental carbon (EC), water-soluble inorganic ionic components (WSICs), and major & trace elements] of particulate matter (PM2.5) and scrutinized their emission sources for urban region of Delhi. The 135 PM2.5 samples were collected from January 2013 to December 2014 and analyzed for chemical constituents for source apportionment study. The average concentration of PM2.5 was recorded as 121.9±93.2μgm-3 (range 25.1-429.8μgm-3), whereas the total concentration of trace elements (Na, Ca, Mg, Al, S, Cl, K, Cr, Si, Ti, As, Br, Pb, Fe, Zn, and Mn) was accounted for ∼17% of PM2.5. Strong seasonal variation was observed in PM2.5 mass concentration and its chemical composition with maxima during winter and minima during monsoon seasons. The chemical composition of the PM2.5 was reconstructed using IMPROVE equation, which was observed to be in good agreement with the gravimetric mass. Source apportionment of PM2.5 was carried out using the following three different receptor models: principal component analysis with absolute principal component scores (PCA/APCS), which identified five major sources; UNMIX which identified four major sources; and positive matrix factorization (PMF), which explored seven major sources. The applied models were able to identify the major sources contributing to the PM2.5 and re-confirmed that secondary aerosols (SAs), soil/road dust (SD), vehicular emissions (VEs), biomass burning (BB), fossil fuel combustion (FFC), and industrial emission (IE) were dominant contributors to PM2.5 in Delhi. The influences of local and regional sources were also explored using 5-day backward air mass trajectory analysis, cluster analysis, and potential source contribution function (PSCF). Cluster and PSCF results indicated that local as well as long-transported PM2.5 from the north-west India and Pakistan were mostly pertinent.

Estimates of land and sea moisture contributions to the monsoonal rain over Kolkata, deduced based on isotopic analysis of rainwater

Abstract. Moisture sources responsible for rains over Kolkata during the summer monsoon can be traced using backward air-mass trajectory analysis. A summary of such trajectories between June and September suggest that these moisture parcels originate from the Arabian Sea and travel over the dry continental region and over the Bay of Bengal (BoB) prior to their arrival at Kolkata. We use monthly satellite and ground-based observations of the hydrometeorological variables together with isotopic data of rainwater from Bangalore and Kakinada to quantify the contributions of advected continental and oceanic water vapour in the Kolkata rains. The vapour mass is modified during its transit from its original isotopic value due to addition of evaporated moisture from the BoB, and further modification occurs due to the process of rainout during transport. The evaporated component is estimated using the Craig–Gordon equation. The rainout process is simulated using a Rayleigh fractionation model. In this simulation we assume that the initial isotopic composition of vapour originating from the continent is similar to the rainwater composition measured at Bangalore. In order to explain the monthly isotopic composition in southwest monsoon rainwater at Kolkata, we invoke 65–75 % moisture contribution from the BoB; the remaining moisture is from the continental land mass.

Isotopic ratios of nitrate in aerosol samples from Mt. Lulin, a high-altitude station in Central Taiwan

The importance of Asian countries towards increase of atmospheric pollutants is being examined critically in recent times. In this context, we carried out analysis of nitrates separated from aerosol samples collected during 2010 from Mt. Lulin (NOAA code: LLN), Taiwan, located at an altitude of 2 862 m above sea level. Large temporal variations are seen in δ15N, δ18O and Δ17O values of the nitrate, with day-to-day variations comparable to the seasonal amplitude. The δ15N values of nitrate are found to be higher in spring months (March–April; −1±3‰) and lower in summer (June–September; −5±3‰). Similarly, the δ18O (69 ± 15‰ versus 32 ± 13‰) and Δ17O (23 ± 5‰ versus 12 ± 4‰) values are higher in spring and lower in summer. The lowest δ18O value observed was 10.8‰. The higher values of δ15N in spring could be attributed to enhanced contribution from fossil fuel combustions, especially burning of coal in nearby Asian countries like China, with the resultant pollutants being brought to the Lulin station by long-range transport. An alternative explanation is the isotopic exchange reaction between N2O5 and HNO3 that elevates the δ15N value in nitrate. The oxygen isotope variability is explained by changes in contribution from two major pathways of nitrate formation from its precursor NOx molecules. During spring time, nitrate formation via the N2O5 pathway is dominant, resulting in higher values of both δ18O and Δ17O. In contrast, during summer, formation involving HO2/RO2 radicals becomes important, producing lower values of δ18O and Δ17O. A chemistry box model was used to study the nitrate formation pathways through oxidation of NO and NO2 via formation of NO2 and NO3−/HNO3. Both the model results and observations suggest that for the formation of NO2 from NO, the pathway via O3 is more active in spring, whereas in summer the pathway via HO2/RO2 radicals predominates. For the subsequent formation of NO3− and HNO3, the OH pathway is more active in summer than in spring. These suggestions are supported by a wind rose diagram and back trajectory analysis of air masses bringing the precursor NOx to the sampling site.

Influence of Cloud/Fog on Atmospheric VOCs in the Free Troposphere: A Case Study at Mount Tai in Eastern China

ABSTRACTField measurements of volatile organic compounds (VOCs) were conducted in July of 2015 at Mount Tai, where 63 species of VOCs were measured using GC-MS. In this study, air samples were collected in two different weather conditions: cloud/fog and non-cloud/fog respectively and influences of the cloud/fog on VOCs species were analyzed. The sources of air masses were calculated by back trajectories with HYSPLIT model. Five main kinds of VOCs were analyzed and oxy-VOCs (OVOCs) had the largest contribution (67% on the cloudy/foggy days and 72% on the non-cloudy/foggy days) to total measured VOCs among all of the samples collected at Mount Tai. Acetone was the most abundant compound (18 ppb on the cloudy/foggy days and 15 ppb on the non-cloudy/foggy days) among the VOCs. The concentrations of VOCs collected in cloudy/foggy days were higher than those measured in non-cloudy/foggy days and indicated that cloudy/foggy days favoured the accumulation of atmospheric VOCs. However, the concentrations of most OVOCs in non-cloud/fog conditions were higher than those in cloud/fog conditions. Atmospheric photochemical reactions may partly account for this result. Air mass trajectory analysis shows that most air masses from heavily polluted areas results in the increase of atmospheric VOCs. OVOCs and aromatics provided the main contribution to ozone formation potential. Besides cloud and fog, VOC concentration is concerned with integrated factors including temperature, relative humidity, wind speed and direction.

Effect of Prudhoe Bay emissions on atmospheric aerosol growth events observed in Utqiaġvik (Barrow), Alaska

The Arctic is a rapidly changing ecosystem, with complex aerosol-cloud-climate feedbacks contributing to more rapid warming of the region as compared to the mid-latitudes. Understanding changes to particle number concentration and size distributions is important to constraining estimates of the effect of anthropogenic activity on the region. During six years of semi-continuous measurements of particle number size distributions conducted near Utqiaġvik (Barrow), Alaska, 37 particle-growth events were observed. The majority of events occurred during spring and summer with a monthly maximum in June, similar to other Arctic sites. Based on backward air mass trajectory analysis, similar numbers of particle-growth events were influenced by marine (46%) and Prudhoe Bay air masses (33%), despite air primarily coming from the Arctic Ocean (75 ± 2% of days) compared to Prudhoe Bay (8 ± 2% of days). The corresponding normalized particle-growth event frequency suggests that emissions from Prudhoe Bay could induce an average of 92 particle-growth events, more than all other air mass sources combined, at Barrow annually. Prudhoe Bay is currently the third largest oil and gas field in the United States, and development in the Arctic region is expected to expand throughout the 21st century as the extent of summertime sea ice decreases. Elevated particle number concentrations due to human activity are likely to have profound impacts on climate change in the Arctic through direct, indirect, and surface albedo feedbacks, particularly through the addition of cloud condensation nuclei.

Colorado air quality impacted by long-range-transported aerosol: a set of case studies during the 2015 Pacific Northwest fires

Abstract. Biomass burning plumes containing aerosols from forest fires can be transported long distances, which can ultimately impact climate and air quality in regions far from the source. Interestingly, these fires can inject aerosols other than smoke into the atmosphere, which very few studies have evidenced. Here, we demonstrate a set of case studies of long-range transport of mineral dust aerosols in addition to smoke from numerous fires (including predominantly forest fires and a few grass/shrub fires) in the Pacific Northwest to Colorado, US. These aerosols were detected in Boulder, Colorado, along the Front Range using beta-ray attenuation and energy-dispersive X-ray fluorescence spectroscopy, and corroborated with satellite-borne lidar observations of smoke and dust. Further, we examined the transport pathways of these aerosols using air mass trajectory analysis and regional- and synoptic-scale meteorological dynamics. Three separate events with poor air quality and increased mass concentrations of metals from biomass burning (S and K) and minerals (Al, Si, Ca, Fe, and Ti) occurred due to the introduction of smoke and dust from regional- and synoptic-scale winds. Cleaner time periods with good air quality and lesser concentrations of biomass burning and mineral metals between the haze events were due to the advection of smoke and dust away from the region. Dust and smoke present in biomass burning haze can have diverse impacts on visibility, health, cloud formation, and surface radiation. Thus, it is important to understand how aerosol populations can be influenced by long-range-transported aerosols, particularly those emitted from large source contributors such as wildfires.

Trans-boundary aerosol transport during a winter haze episode in China revealed by ground-based Lidar and CALIPSO satellite

By employing PM2.5 observation data, ground-based lidar measurements, MODIS and CALIPSO satellite images, meteorological data, and back trajectories analysis, we investigate a trans-boundary transport of aerosols during a large-area haze episode in China during 3–5 January 2015. The ground-based lidar observations indicated similar episodes of external aerosols passing through and mixing into three East China cities. A considerable amount of total AOD below 3 km (46% in average) was contributed by the external aerosol layers during passing over and importing. CALIPSO satellite observations of central and eastern China revealed a high altitude pollutant belt on January 3. Although the severest ground pollution was found in central and south-eastern Hebei, the high altitude pollution transport was greater in south-western Shandong, north-western Jiangsu, and north-western Anhui. These observations along with the analysis of air mass trajectories and wind fields indicates pollutants moving from Hebei, Henan and Hubei probably contributed to the haze pollution in Shandong and Jiangsu. This study reveals haze transports from North China Plain to East China could be a common phenomenon influenced by the winter monsoon in northern China. Hence, effective control of air pollution requires collaboration among different cities and provinces throughout China. The long-term measurements of aerosol vertical properties by ground-based lidar and CALIPSO are extremely valuable in quantifying the contributions of external factors and will be helpful in validating and improving various air quality models.

Dimethyl sulfide in the summertime Arctic atmosphere: measurements and source sensitivity simulations

Abstract. Dimethyl sulfide (DMS) plays a major role in the global sulfur cycle. In addition, its atmospheric oxidation products contribute to the formation and growth of atmospheric aerosol particles, thereby influencing cloud condensation nuclei (CCN) populations and thus cloud formation. The pristine summertime Arctic atmosphere is strongly influenced by DMS. However, atmospheric DMS mixing ratios have only rarely been measured in the summertime Arctic. During July–August, 2014, we conducted the first high time resolution (10 Hz) DMS mixing ratio measurements for the eastern Canadian Archipelago and Baffin Bay as one component of the Network on Climate and Aerosols: Addressing Key Uncertainties in Remote Canadian Environments (NETCARE). DMS mixing ratios ranged from below the detection limit of 4 to 1155 pptv (median 186 pptv) during the 21-day shipboard campaign. A transfer velocity parameterization from the literature coupled with coincident atmospheric and seawater DMS measurements yielded air–sea DMS flux estimates ranging from 0.02 to 12 µmol m−2 d−1. Air-mass trajectory analysis using FLEXPART-WRF and sensitivity simulations with the GEOS-Chem chemical transport model indicated that local sources (Lancaster Sound and Baffin Bay) were the dominant contributors to the DMS measured along the 21-day ship track, with episodic transport from the Hudson Bay System. After adjusting GEOS-Chem oceanic DMS values in the region to match measurements, GEOS-Chem reproduced the major features of the measured time series but was biased low overall (2–1006 pptv, median 72 pptv), although within the range of uncertainty of the seawater DMS source. However, during some 1–2 day periods the model underpredicted the measurements by more than an order of magnitude. Sensitivity tests indicated that non-marine sources (lakes, biomass burning, melt ponds, and coastal tundra) could make additional episodic contributions to atmospheric DMS in the study region, although local marine sources of DMS dominated. Our results highlight the need for both atmospheric and seawater DMS data sets with greater spatial and temporal resolution, combined with further investigation of non-marine DMS sources for the Arctic.

Characterization of PM2.5 generated from opencast coal mining operations: A case study of Sonepur Bazari Opencast Project of India

Abstract Opencast coal mines, a major source of airborne particulate matter (PM), is widespread in India. The health impacts are primarily associated with the concentration and composition of the PM inhaled. A study aimed at characterization of the airborne PM 2.5 at a coal mine was carried out during 01–07 October 2014 in the Sonepur Bazari Opencast Project in India. Samples were collected at three different locations at the mine using PM 2.5 samplers. Collected PM 2.5 samples were characterized in terms of surface elemental composition using Energy Dispersive X-ray (EDX) spectroscopy. The PM 2.5 levels were 2–3 times of the permissible Indian limits. Surface elemental composition analysis indicates that Fe (∼45–70%) and C (∼30–50%) as the dominant elements amongst all elements present in PM 2.5 . An average organic carbon (OC) to elemental carbon (EC) ratio of 3.5 indicated diesel vehicle and coal smoke from stockyard as the sources, which is typical to opencast coal mining activities. Forward air mass trajectory analysis using HYSPLIT4 model showed that in addition to the locations nearby the mine getting affected by the PM 2.5 emitted from the mine, places as far as 200 km from the mine can also receive the traces of PM 2.5 . More studies on elemental species characterization of PM 2.5 in different coal mining areas will provide better understanding of occupational health hazards to which mine workers exposed due to inhalation of airborne PM.