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This study aims to investigate the seasonal variation and source identification of fluorescent aerosol particles at the monitoring site of the University of Salento in Lecce, southeastern Italy. Utilizing a wideband integrated bioaerosol sensor (WIBS), this research work analyzes data from two specific monitoring days: one in winter (10 January 2024), marked by significant transport of anthropogenic particles from Eastern Europe, and another in early spring (6 March 2024), characterized by marine aerosol sources and occasional desert dust. This study focuses on the seven WIBS particle categories (A, B, C, AB, AC, BC, ABC), which exhibited distinct characteristics between the two days, indicating different aerosol compositions. Winter measurements revealed a predominance of fine-mode particles, particularly soot and bacteria. In contrast, spring measurements showed larger particles, including fungal spores, pollen fragments, and mineral dust. Fluorescence intensity data further emphasized an increase in biological and organic airborne material in early spring. These results highlight the dynamic nature of fluorescent aerosol sources in the Mediterranean region and the necessity of continuous monitoring for air quality assessments. By integrating WIBS measurements with air mass back-trajectories, this study effectively identifies fluorescent aerosol sources and their seasonal impacts, offering valuable insights into the environmental and health implications of aerosol variability in the investigated Mediterranean area. [ABSTRACT FROM AUTHOR]

Marine carbonaceous aerosols, originating from marine and continental sources, are significant global aerosol components. The understanding of marine carbonaceous aerosols is currently limited, especially in the Southern Hemisphere. Furthermore, there is an ongoing debate regarding the contributions of marine fresh and ancient carbon to marine aerosols. To address these gaps, we conducted an extensive investigation utilizing a long‐term data set of aerosol samples collected during six Antarctic cruises (28°N–78°S) from 2013 to 2020. Our analysis revealed an average organic carbon (OC) concentration of 1.29 ± 1.15 μg/m3 and an element carbon (EC) concentration of 0.13 ± 0.18 μg/m3 in the samples. These concentrations varied within a range spanning from background marine samples to those impacted by substantial continental transport. Fossil fuel combustion remained the primary source of continental influence in the marine environment, as evidenced by the OC/EC ratio. The δ13CTC value for all samples range from −22.3‰ to −28.4‰, with a mean value of −26.3 ‰. Using a three‐endmember isotopic source model, we find that continental carbonaceous aerosols make substantial contributions in the Eastern Indian Ocean (81 ± 4%), while their prevalence is lower in the Southern Ocean (SO) (44 ± 20%). In contrast to mid‐latitudes, primary marine aerosol of the SO exhibits a significantly higher contribution from the fresh carbon pool (52 ± 19%). Furthermore, our study suggests that SO sea ice may play a potential role in driving emissions from the fresh carbon pool. These findings contribute to a comprehensive understanding of the effects of carbonaceous aerosols on climate change and the ocean‐atmosphere carbon cycle. Plain Language Summary: In this study, we investigated marine carbonaceous aerosols, which are important components of global aerosols. We analyzed a long‐term data set of aerosol samples collected during Antarctic cruises from 2013 to 2020. Our analysis showed that the concentration of organic carbon (OC) averaged 1.29 ± 1.15 μg/m3, and the concentration of element carbon (EC) averaged 0.13 ± 0.18 μg/m3 in the samples. The concentrations varied, ranging from background marine levels to those influenced by continental transport. The highest OC concentration was observed over the Eastern Indian Ocean, attributed to emissions from power plants and refineries. Fossil fuel combustion remained the primary source of continental influence. Isotopic analysis revealed that continental carbonaceous aerosols contributed significantly in the EIO (81 ± 4%), while their prevalence was lower in the SO (44 ± 20%). In the SO, primary marine aerosols had a higher contribution from fresh carbon pool (52 ± 19%), which is closely linked to the marine phytoplankton ecosystem. We also found that sea ice in the SO may play a potential role in driving emissions from the fresh carbon pool and influencing carbonaceous aerosol concentrations. These findings enhance our understanding of the impacts of carbonaceous aerosols on climate change and the ocean‐atmosphere carbon cycle. Key Points: Fossil fuel combustion is the primary source of continental influence in the marine environmentCarbonaceous aerosol of the Southern Ocean (SO) exhibits a significant contribution from the fresh carbon pool (52 ± 19%)SO sea ice play a potential role in driving emissions from the fresh carbon pool [ABSTRACT FROM AUTHOR]

Aeolian transport of mineral dust is an important carrier of nutrients and trace metals to the surface ocean and, hence, affects the biogeochemical cycles of C and N therein. Studies focusing on the provenances of dust across the latitudinal gradients over the open ocean waters are essential for better constraining the biogeochemical effects of dust deposition. Here, we analyzed the radiogenic isotope composition of Sr (87Sr/86Sr) and Nd (ε Nd (0)) in the silicate fraction of mineral aerosols collected over the pelagic northern and southern Indian ocean waters during the GEOTRACES-India research expeditions (GI-01: March-April 2014 and GI-02: April-May 2014). Both tracers, 87Sr/86Sr and ε Nd (0), exhibited marked spatial variability for dust deposition to different basins, including the Bay of Bengal (BoB), Arabian Sea (AS), equatorial Indian Ocean (EIO), and the southern sector of the Indian Ocean (SIO). The dust deposited in the AS showed a narrow spread in both 87Sr/86Sr (0.71520–0.71642) and ε Nd (0) (−10.9 to −10.1), along with the air mass back trajectories, indicating transport from the Arabian Peninsula. Likewise, the dust collected over the BoB was mainly sourced from the Thar Desert (87Sr/86Sr > 0.72, −16 < ε Nd (0) 〈 −1 3), whereas the EIO received mineral dust from the Thar Desert and sand dunes in northern Australia (87Sr/86Sr: 0.72, ε Nd (0): −11) and Indonesian Archipelago. In contrast, the SIO appeared to receive dust deposition from three different source regions, including dust from Antarctica, western Australia (87Sr/86Sr: 0.712, −20 < ε Nd (0) <−16, and South Africa/South America (87Sr/86Sr: 0.708–0.710; −24.5 < ε Nd (0) >−8.4). These results have important implications for modelling the dust transport to pelagic Indian and southern Indian Ocean waters. [ABSTRACT FROM AUTHOR]

Our understanding of ocean-cloud interactions and their effect on climate lacks insight into a key pathway: do biogenic marine emissions form new particles in the open ocean atmosphere? Using measurements collected in ship-borne air-sea interface tanks deployed in the Southwestern Pacific Ocean, we identified new particle formation (NPF) during nighttime that was related to plankton community composition. We show that nitrate ions are the only species for which abundance could support NPF rates in our semicontrolled experiments. Nitrate ions also prevailed in the natural pristine marine atmosphere and were elevated under higher sub-10 nm particle concentrations. We hypothesize that these nucleation events were fueled by complex, short-term biogeochemical cycling involving the microbial loop. These findings suggest a new perspective with a previously unidentified role of nitrate of marine biogeochemical origin in aerosol nucleation. [ABSTRACT FROM AUTHOR]

Atmospheric particles from different sources can impact cloud formation and play a critical role in regulating cloud properties. However, particle characteristics at single particle level and their abilities to serve as ice nucleating particles (INPs) over different marine atmosphere are poorly understood. Here, we present characterizations and ice nucleation properties of particles collected during a northern and southern hemisphere cruise from South Korea to Antarctica. Micro-spectroscopic analysis was used to obtain composition of individual particles and mixing state of particle populations. Major particle classes were identified and have different contributions over the Western Pacific and the Southern Ocean, including fresh and aged sea salt, sea salt mixed with sulfate, carbonaceous, sulfur-containing, and dust particles. Increasing contribution of fresh sea salt particles, the dominate particle class in the samples, tended toward an increasing mixing state index indicating the population becoming more internally mixed. Aging processes and new particle sources introduce particles with new compositions resulting in external mixtures. We found that the investigated particles demonstrated a variety of ice nucleation abilities at cirrus conditions. The identified INPs are all major particle classes present in the population, and the sea salt mixed sulfate particle is enriched in INPs. Aging processes affected both particle mixing state and their ice nucleation abilities. We tested different ice nucleation parameterizations of marine atmospheric particles for their applicability. Finally, we discuss how the mixing state of particle populations impacts ice nucleation in the atmosphere. [ABSTRACT FROM AUTHOR]

Marine aerosol particles can act as cloud condensation nuclei and influence the atmospheric boundary layer by scattering solar radiation. The interaction of ocean waves and coral reefs may affect the distribution and size of marine aerosol particles. Measuring this effect has proven challenging. Here, we tested the hypothesis that the distribution and size of marine aerosol particles would vary over three distinct zones (i.e., coral lagoon, surf break, and open water) near One Tree Island in the Great Barrier Reef, which is approximately 85 km off the east coast of Australia. We used a modified DJI Agras T30 drone fitted with a miniaturised scanning electrical mobility sizer and advanced mixing condensation particle counter to collect data on aerosol size distribution between 30 and 300 nm at 20 m above the water surface. We conducted 30 flights over ten days during the Austral summer/autumn of 2023. The fitted bimodal lognormal curves indicate that the number concentrations for aerosols below 85 nm diameter are more than 16% higher over the lagoon than over open water. The average mean mode diameters remained constant across the different zones, indicating no significant influence of breaking waves on the detected aerosol size modes. The most influential explanatory variable for aerosol size distribution was the difference between air temperature and the underlying sea surface, explaining around 40% of the variability. Salinity also exhibited a significant influence, explaining around 12% of the measured variability in the number concentration of aerosols throughout the campaign. A calculated wind stress magnitude did not reveal significant variation in the measured marine aerosol concentrations. Overall, our drone-based aerosol measurements near the water surface effectively characterise the dynamics of background marine aerosols around One Tree Island Reef, illustrating the value of drone-based systems for providing size-dependent aerosol information in difficult-to-access and environmentally sensitive areas.

Context. In total, 43 shallow waterbodies were sampled in 1983 in the vicinity of Casey Station and nearby islands in Antarctica. The following physico-chemical parameters were obtained: water and air temperature, pH, conductivity, dissolved oxygen, plus major and minor elements. Aims. To identify the physico-chemical characteristics of these waters and determine their origin, and calculate theirmineral saturation indices. Methods. Waterswere analysed using standardmethods, including for some elements, flame-atomic absorption spectrometry, spectrophotometry, ion chromatography and gravimetric determination. Mineral saturation indices were calculated using the PHREEQ program. Key results. Water salinities were generally low and in the range of 120-1200mg L-1 (total dissolved solids, TDS), except for one site connected to the sea, and four slightly saline sites. The Na/Cl, Cl/Br and Ca/SO4 ratios of several waters were in the vicinity of seawater ratios, implying a contribution of marine aerosols. However, the Mg/Ca ratio of most waters departed from the seawater ratio, plus there was concordance between the molar ratios of (Na + K)/(Ca + Mg) of many of the waters sampled and those calculated from rock geochemical analyses from diverse lithologies. Such chemical 'provincialism' appears to be dictated by rock composition. Nitrate and phosphate concentrations were high in the vicinity of penguin rookeries. Conclusions. Two sources of ions are identified, one as marine aerosols as shown by three sets of ratios (Na/Cl, Cl/Br and Ca/SO4) with known marine values, and the other from the weathering of local rocks as shown by (Na + K)/(Ca + Mg) of the lake waters compared to the same ratios for the surrounding rocks. Only a few waterbodies have saturation levels for several carbonate minerals (calcite, aragonite, dolomite and rhodochrosite). Implications. Future work is recommended for monitoring the waterbodies surrounding Casey Station as a result of the increased atmospheric CO2 concentration that has occurred over the past 40 years, and likely also with the cessation of building activities around Casey Station. [ABSTRACT FROM AUTHOR]

Dimethyl sulfide (DMS), emitted from the oceans, is the most abundant biological source of sulfur to the marine atmosphere. Atmospheric DMS is oxidized to condensable products that form secondary aerosols that affect Earth's radiative balance by scattering solar radiation and serving as cloud condensation nuclei. We report the atmospheric discovery of a previously unquantified DMS oxidation product, hydroperoxymethyl thioformate (HPMTF, HOOCH2SCHO), identified through global-scale airborne observations that demonstrate it to be a major reservoir of marine sulfur. Observationally constrained model results show that more than 30% of oceanic DMS emitted to the atmosphere forms HPMTF. Coincident particle measurements suggest a strong link between HPMTF concentration and new particle formation and growth. Analyses of these observations show that HPMTF chemistry must be included in atmospheric models to improve representation of key linkages between the biogeochemistry of the ocean, marine aerosol formation and growth, and their combined effects on climate.

This work addresses the chemical characterization of atmospheric aerosols and precipitation in the period from May to November 2019 at Monte Fenton (53.16° S, 71.05° W, 612 m.a.s.l.), 9 km west of Punta Arenas, to study the contribution and distribution of emission sources and chemical enrichment. The main ions (Ca2+, Cl−, K+, Mg2+, Na+, NH4+, NO3− and SO42−) were studied using ion chromatography, and trace elements (Al, Br, Ca, Cl, Cr, Fe, K, Mg, Mn, Na, Ni, P, Pb, S, Se, Si, Ti, V and Zn) using energy dispersive X-ray fluorescence. Ions concentration ranged from 5.0 × 10−1 to 2.9 × 104 mg/m3 for Ca2+ and Cl−, respectively; whilst the concentration of elements varied between 8.8 × 10−11 and 2.1 × 10−2 mg/m3, for crZn (crustal Zn) and Fe, respectively. The electrical conductivity (EC, mean = 32.5 µS/cm) and the pH (mean = 6.8), showed the atmosphere of the study site was relatively neutral compared to the standard pH for rain (or snow) without contamination (pH = 5.6), and presented relatively low levels of conductivity compared to the EC standards for distilled water (0.5 to 3 µS/cm) and seawater (30,000 to 60,000 µS/cm). The main contribution to aerosols in the atmosphere of Monte Fenton came from marine and lithospheric sources, followed by local anthropogenic sources such as burning firewood and/or urban waste for heating production, etc., that led to the enrichment of aerosols with high Fe, K, Mn and V content. The results of this study contribute to filling a gap in knowledge of the chemistry of atmospheric aerosols in Southern Patagonia. [ABSTRACT FROM AUTHOR]

The source of marine carbonaceous aerosols is crucial to determine as it provides information about the ocean‐cloud‐climate relationship and the carbon cycle. However, contribution of different marine organic pools to marine primary organic aerosols remains controversial and this will lead to uncertainties in climate models. Here, we report the stable carbon isotopes and carbonaceous fraction of marine aerosols, measured during three summer Arctic cruises (33°N–85°N, July‐September, 2014–2018). By comparing the stable carbon isotopic signatures of seawater and aerosols in the Arctic Ocean, we found that the marine fresh carbon pool had a depleted isotopic signature, contributing 80 ± 12% of the carbonaceous fraction. Both in 2016 and 2018, the aerosol carbon isotopes in the Arctic Ocean were significantly higher than those in 2014. Increased productivity in the Arctic Ocean may dominate the increase of stable carbon isotope in the marine fresh carbon pool on an annual scale. Our research highlights the important contribution of fresh marine carbon pool to marine carbonaceous aerosols in response to marine ecosystem change under Arctic warming. Plain Language Summary: The source of marine carbonaceous aerosols is crucial to determine as it provides information about climate change. The Arctic has received widespread attention due to the rapid warming of recent years. Here, we report the stable carbon isotopes and carbonaceous fraction of marine aerosols, measured during three summer Arctic cruises. Stable carbon isotopes can be effective in probing the origin of marine aerosols. By comparing the stable carbon isotopic signatures of seawater and aerosols in the Arctic Ocean, we found the same isotopic signature between aerosols and sea surface particulate organic carbon. This means that the fresh marine carbon pool represented by marine particulate organic carbon may be an important and neglected pool of carbon and dominates the Arctic Ocean carbonaceous aerosol. On multi‐year scales, increased productivity due to Arctic warming may be reflected in changes in aerosol carbon isotopes. This research highlights the important contribution of fresh marine carbon pool to marine carbonaceous aerosols in response to marine ecosystem change under Arctic warming. Key Points: Stable carbon isotope of aerosol during three Arctic cruises are reportedFresh carbon pool contributing 80 ± 12% of Arctic Ocean carbonaceous aerosolArctic warming leads to higher carbon isotope in summer Arctic Ocean aerosols [ABSTRACT FROM AUTHOR]

To explore the latitudinal distributions, sources and formation mechanisms of total carbon (TC), nitrogen (TN), sulfur (TS) and water‐soluble major ions (Na+, Cl−, SO42−, K+, nss‐SO42−, NH4+, NO3−, and MSA−), marine aerosol samples were collected over the Western Pacific (WP) and Southern Ocean (SO) from November 1994 to February 1995. Concentrations of TC ranged 30–390 ng m−3 (av. 190 ng m−3) over the SO, which are six times lower than those (1,200 ng m−3) over the WP, whereas concentrations of TN (av. 83 ng m−3) in the SO are three times lower than those (av. 232 ng m−3) over the WP. The highest concentrations of TC and TN were observed near New Zealand (7,000 and 720 ng m−3, respectively), suggesting a continental influence over the marine atmosphere. NO3−, tracer of anthropogenic sources, showed higher concentrations over the WP, whereas NH4+ concentrations over the SO are higher than the WP. The latter may be associated with penguin‐derived guano droppings from Antarctica. The concentration trends and statistical analysis demonstrate that the formation mechanisms of MSA− over the SO and WP is different. We found a strong correlation between MSA− and liquid water content (LWC) over the WP, suggesting the heterogenous aqueous phase production of MSA−, whereas aqueous phase reaction is less important over the SO. The strong correlation (R2 = 0.97) between nss‐Ca2+ and ss‐Ca2+ together with their similar relative abundances demonstrates an influence of CaCO3 eroded from coral reefs and shells and subsequent emission to the atmosphere by bubble bursting process. Plain Language Summary: Major ions in the marine aerosols are important constituents with various sources. The ionic composition and sources are studied via the oceanic cruise over the Western Pacific (WP) and Southern Ocean (SO). Total carbon (TC), total nitrogen (TN) and total sulfur (TS) are disclosed for the first time over the SO. Marine aerosols collected over the WP is influenced by the anthropogenic sources in the Asian continent. There are several penguin colonies in Antarctica, which may be the source for the abundant presence of NH4+ over the SO emitted from the penguin‐derived guano. Coral reefs eroded from the ocean may have an influence on the marine atmosphere. Biomass burning tracers also affect the pristine marine atmosphere in the SO. The formation of methanesulfonic acid (MSA) from dimethylsulfide (DMS) over the WP and SO is different. Solid, liquid and gas‐phase reactions contribute to the formation of the MSA in the WP, whereas different kind of mechanisms such as free radical mechanism may be involved over the SO. Long term study is needed to reveal the exact formation mechanism of MSA from DMS over the SO. Key Points: Total carbon, Total nitrogen and total sulfur over the Western Pacific and Southern Oceanwater‐soluble major ions (Na+, Cl−, SO42−, K+, nss‐SO42−, NH4+, NO3−, and MSA−) in the marine atmosphereErosion of coral reefs and shells and subsequent emission to the atmosphere by bubble bursting process [ABSTRACT FROM AUTHOR]

Ice wedges are a characteristic ground ice feature in permafrost regions that form primarily from the meltwater of the seasonal snowpack. Ice‐wedge oxygen and hydrogen stable isotopes have been used in winter paleotemperature reconstructions; however, until recently, the ion geochemistry of ice wedges has rarely been analyzed as a potential paleoclimate proxy. This potential is greatest for ice wedges located in coastal regions, where marine aerosols are the dominant contributor to snowpack impurities. Here, we evaluate the source and integrity of ionic concentrations of a coastal ice wedge in the northwestern Canadian Arctic (Beaufort Sea coast) to evaluate the use of ice wedges as a marine aerosol archive. Comparison to a regionally comparable snowpack reveals remarkably similar ionic concentrations for Cl−, Na+, Br−, SO42−, Ca2+, and Mg2+, with a Cl−/Na+ ratio similar to bulk seawater (1.80 vs. 1.79 in seawater), suggesting that marine aerosols, probably from sea salt aerosol production during blowing snow events over sea ice as indicated by depleted SO42− values relative to Na+, are probably the dominant contributor to ion concentrations. A previously established linear age model for the ice wedge is used to develop a continuous ion record spanning ~4,600 to ~700 yr b2k. Cl− and Na+ concentrations reveal a strong and continuous increase in concentrations over the late Holocene, thought to be driven by reduced distance‐to‐coast of up to 1 km as a result of coastal erosion. This study presents a novel interpretation of ice‐wedge geochemical data and represents the first Holocene ice‐wedge ion record. [ABSTRACT FROM AUTHOR]

Marine aerosol, containing an enormous source of chloride, coupled with severe environmental conditions (e.g., high temperature, high relative humidity), poses a threat to the durability of concrete exposed to the marine atmospheric zone. The distribution of marine aerosol is spatial and temporal dependent, and thus, the deposition rate of airborne chlorides Ddep can vary a lot with geological and environmental factors. Chloride profile in concrete exposed to marine aerosol is a two-zone profile due to the wetting/drying action. The peak chloride concentration Cmax and depth of the convection zone Δx are largely affected by time, materials, environmental conditions which usually is less than 10 mm. Many models based on Fick’s law are developed to predict chloride transport in unsaturated concrete under wetting–drying cycles. However, the prediction of marine aerosol penetration into concrete is far from satisfactory, due to lack of enough experimental and theoretical researches. [ABSTRACT FROM AUTHOR]

The North Atlantic Aerosols and Marine Ecosystems Study (NAAMES) is an interdisciplinary investigation to improve understanding of Earth's ocean ecosystem-aerosol-cloud system. Specific overarching science objectives for NAAMES are to (1) characterize plankton ecosystem properties during primary phases of the annual cycle and their dependence on environmental forcings, (2) determine how these phases interact to recreate each year the conditions for an annual plankton bloom, and (3) resolve how remote marine aerosols and boundary layer clouds are influenced by plankton ecosystems. Four NAAMES field campaigns were conducted in the western subarctic Atlantic between November 2015 and April 2018, with each campaign targeting specific seasonal events in the annual plankton cycle. A broad diversity of measurements were collected during each campaign, including ship, aircraft, autonomous float and drifter, and satellite observations. Here, we present an overview of NAAMES science motives, experimental design, and measurements. We then briefly describe conditions and accomplishments during each of the four field campaigns and provide information on how to access NAAMES data. The intent of this manuscript is to familiarize the broad scientific community with NAAMES and to provide a common reference overview of the project for upcoming publications.

In order to determine the nature of the high salinisation rate of the waters of Lake Sidi Boughaba, which has been listed in the Ramsar list since 1980, 23 samples that were taken during four sampling operations were subjected to physicochemical analyses. The obtained results were processed using a combination of bi-varied methods (correlation tests) and multivariate statistical methods (principal component analysis - PCA). The physicochemical analyses reveal that they are alkaline waters with a pH ranging between 8.38 and 9.03, an electrical conductivity (EC) of the order of 12.4 to 17.4 mS⋅cm-1, and high levels of Na+ and Cl-, up to 3700 and 6630 mg⋅dm-3 respectively, indicating a marine origin of these waters. In addition, the statistical treatment revealed that the mineralisation of the waters of this ecosystem is controlled by four main mechanisms of the salinisation; the main mechanism underlying this strong mineralisation is due to the impact of the marine spray. The second-order processes are about the phenomenon of the ion exchange, the dissolution/precipitation of evaporitic and carbonate formations, the oxidation-reduction processes, notably the reduction of sulphates as well as biochemical phenomena due to the selective absorption of certain ions by fauna and flora. [ABSTRACT FROM AUTHOR]

Aerosols play an important role in the Earth–atmosphere system. Their impacts on the weather and climate are highly dependent on spatiotemporal distributions as well as physical-optical properties. Physical-optical properties of the aerosols over the Asian continent have been widely investigated, but there are relatively few observations in maritime locations, especially the South China Sea (SCS). Here, with the combination of in situ ship-based observations from June and July 2019 as well as long-term MERRA-2 reanalysis datasets from January 2012 to December 2021, the physical and optical properties of marine aerosols in the SCS are explored. The impacts of meteorological factors, particularly frontal systems, on the aerosol properties are further analyzed based on detailed observations. The observed results show that aerosols are vertically concentrated below 3 km and the extinction coefficient reaches the maximum value of 0.055 km−1 near 480 m. Moreover, the particles are composed of an accumulation and a coarse particle mode, and they conform to the lognormal distribution. The synoptic-scale case study demonstrates that both the cold front and stationary front lead to an increase in aerosol optical thickness (AOD), which is due to the enhanced wind speed and the hygroscopic growth of fine particles, respectively. The long-term analysis indicates that AOD decreases from northwest to southeast with the increasing distance away from the continent, and it reflects higher values in spring and winter than in summer and autumn. Sulfate and sea salt dominate AOD in this region when compared with other components. The overall AOD shows a significant negative trend of −0.0027 year−1. This work will help us further understand the physical and optical properties of marine aerosols over the SCS and then contribute to quantifying the aerosol radiative forcing in the future. [ABSTRACT FROM AUTHOR]

Ice nucleating particles (INPs) are vital for ice initiation in, and precipitation from, mixed-phase clouds. A source of INPs from oceans within sea spray aerosol (SSA) emissions has been suggested in previous studies but remained unconfirmed. Here, we show that INPs are emitted using real wave breaking in a laboratory flume to produce SSA. The number concentrations of INPs from laboratory-generated SSA, when normalized to typical total aerosol number concentrations in the marine boundary layer, agree well with measurements from diverse regions over the oceans. Data in the present study are also in accord with previously published INP measurements made over remote ocean regions. INP number concentrations active within liquid water droplets increase exponentially in number with a decrease in temperature below 0 °C, averaging an order of magnitude increase per 5 °C interval. The plausibility of a strong increase in SSA INP emissions in association with phytoplankton blooms is also shown in laboratory simulations. Nevertheless, INP number concentrations, or active site densities approximated using "dry" geometric SSA surface areas, are a few orders of magnitude lower than corresponding concentrations or site densities in the surface boundary layer over continental regions. These findings have important implications for cloud radiative forcing and precipitation within low-level and midlevel marine clouds unaffected by continental INP sources, such as may occur over the Southern Ocean.

Marine aerosols play an important role in the Earth's climate, but their effects remain highly uncertain due to a poor understanding of their sources, properties, and atmospheric processing, partly due to limited measurements. The Coastal Fog study investigated the processes controlling the formation and properties of fog in the North Atlantic Ocean. As part of this study, aerosol-particle-size distributions and chemical composition were measured off the shore of the north-eastern United States and Atlantic Canada, and used to investigate the sources and processes affecting the observed aerosols. Processed marine air during the study was characterized by single and bimodal aerosol size distributions. Aerosols in the port city of St. John's, Newfoundland likely reflected local emissions built up due to poor ventilation, whereas aerosols observed in Halifax, Nova Scotia were likely affected by transport, cloud processing and precipitation. Finally, two particle-growth events were observed. The first event captured the appearance of 10-nm particles that grew to 30 nm over 4 h. These aerosols appeared to be newly formed in the upper portion of the boundary layer with influence from the free troposphere before subsiding to the surface. In the second event, 45-nm particles grew to 70 nm over 8 h. Our observations provide important insight into the processes affecting marine aerosols and highlight the crucial role of boundary-layer meteorology. [ABSTRACT FROM AUTHOR]

To understand the sources and transport pathways of organic compounds associated with soil microbes and higher plant waxes in the East Asian outflow, we assessed source‐specific tracers such as α‐, β‐ and ω‐hydroxy fatty acids (FAs) in remote marine aerosols collected at Chichijima Island in the western North Pacific (WNP) during 2001–2003. Molecular distributions of hydroxy FAs are characterized by strong even‐carbon numbered predominance, indicating biogenic sources. Hydroxy FAs showed a strong seasonality with higher loadings during winter/spring than summer/autumn. Cluster analysis of backward air mass trajectories, satellite‐based fire counts and dust extinction data reveal an impact of the East Asian outflow over the WNP in winter/spring. In the spring, there are larger relative abundances of short‐chain β‐hydroxy C10‐C18 FAs (a proxy for soil microbes), consistent with the higher loadings of non‐sea‐salt Ca2+ (dust tracer). The molecular distributions of β‐hydroxy FAs in spring are in agreement with those of the reference materials of Chinese loess (CJ‐1) and simulated Asian mineral dust (CJ‐2), suggesting their probable sources in East Asia. A comparison of relative abundances of short‐chain β‐hydroxy C10‐C18 FAs and long‐chain ω‐hydroxy C20‐C32 FAs (a proxy for higher plant metabolites) in Chichijima aerosols between this (2001–2003) and previous (1990–1993) studies have unveiled an increment of 20% and 30%, respectively. Such an increase was likely caused by the changes in source strength on a decadal‐scale and warrants further investigation. Furthermore, cluster analysis of trajectories and the overall distributions of hydroxy FAs between both datasets have shown their similar provenance in winter/spring. Plain Language Summary: Atmospheric transport is a major source of land‐derived lipid compounds in the deep‐sea sediments. Here, we assessed the source‐specific tracers (α‐, β‐ and ω‐hydroxy fatty acids [FAs]) of soil microbes and higher plant waxes in remote marine aerosols collected at Chichijima Island in the western North Pacific during 2001–2003 to understand their sources and transport patterns from East Asia. Molecular distributions of hydroxy FAs revealed characteristic even‐C number predominance, suggesting their origin from plant waxes/soil microbes. Besides, hydroxy FAs showed higher concentrations in winter/spring compared to summer/autumn. High concentrations of short‐chain β‐(C10‐C18) hydroxy FAs (tracers of soil‐microbes) coincide with the non‐sea‐salt Ca2+ loadings (dust tracer) in spring. Similar molecular distributions of β‐hydroxy FAs in the Chichijima aerosols and the reference materials of Chinese loess (CJ‐1) and simulated Asian mineral dust (CJ‐2), suggesting their probable sources in East Asia. A comparison of relative abundances of β‐(C10‐C18) and long‐chain ω‐(C20‐C32) hydroxy FAs (tracer of plant lipids) in Chichijima aerosols collected between 2001–2003 and 1990–1993 have unveiled an increment of ∼20% and 30%, respectively. Despite having similar sources in winter/spring between both these datasets, such an increase could only be explained by changes in source strength on decadal‐scale. Key Points: High concentrations of β/ω‐hydroxy fatty acids (FA) in winter/spring suggest the impact of plant/microbial lipids in the East Asian outflowDistributions of β/ω‐hydroxy FAs between 1990–93 and 2001‐03 clearly indicate their similar sources in East AsiaSignificant increases in β‐ (20%) and ω‐hydroxy FAs (30%) from 1990–93 to 2001–2003 suggest changes in source‐strength of the Asian outflow [ABSTRACT FROM AUTHOR]

Iodine affects the radiative budget and the oxidative capacity of the atmosphere and is consequently involved in important climate feedbacks. A fraction of the iodine emitted by oceans ends up in aerosols, where complex halogen chemistry regulates the recycling of iodine to the gas-phase where it effectively destroys ozone. The iodine speciation and major ion composition of aerosol samples collected during four cruises in the East and West Pacific and Indian Oceans was studied to understand the influences on iodine’s gas-aerosol phase recycling. A significant inverse relationship exists between iodide (I–) and iodate (IO3–) proportions in both fine and coarse mode aerosols, with a relatively constant soluble organic iodine (SOI) fraction of 19.8% (median) for fine and coarse mode samples of all cruises combined. Consistent with previous work on the Atlantic Ocean, this work further provides observational support that IO3– reduction is attributed to aerosol acidity, which is associated to smaller aerosol particles and air masses that have been influenced by anthropogenic emissions. Significant correlations are found between SOI and I–, which supports hypotheses that SOI may be a source for I–. This data contributes to a growing observational dataset on aerosol iodine speciation and provides evidence for relatively constant proportions of iodine species in unpolluted marine aerosols. Future development in our understanding of iodine speciation depends on aerosol pH measurements and unravelling the complex composition of SOI in aerosols.

Study region: Ireland Study focus: Multiple studies have established that catchment geology and weathering regime strongly influence surface water chemistry, and that geochemical cycling can vary due to seasonal climatic conditions. However, fewer studies have focused on the influence these controls in a holistic manner. We relate the water chemistry of a country-wide Irish river survey to atmospheric input, underlying geology, and the influence of bogs. Climatic conditions were defined by an atypically wet winter and an unusually dry summer, providing the opportunity to investigate river chemistry variation across hydrologic conditions. Sampling included 21 of Ireland’s 22 largest rivers ranked by discharge, first-order and second-order streams draining bog lands, a second-order stream draining a limestone catchment, and downstream transects along the River Shannon. All samples were analyzed for major elements, selected trace elements, and nutrients, and a subset was analyzed for δ34SSO4. New hydrological insights: Most catchments were dominated by carbonate weathering with little contribution from the weathering of aluminosilicates. River water composition also varied geographically along the prevailing wind direction due to inputs from marine aerosols, with additional weathering components important in some systems. Seasonal influences could be seen in the chemistry of the headwaters of the River Shannon, while the lower reaches of the river exhibited less variable behavior throughout seasonal changes, likely due to the influence of lakes in the River Shannon system.

Dissolved black carbon (DBC) is an important recalcitrant fraction of marine dissolved organic matter. Riverine discharge is the largest known source of oceanic DBC; however, the significance of atmospheric deposition as a source of oceanic DBC remains poorly understood. In this study, year‐round aerosol sampling was carried out at a rural coastal site in Southeast Asia for DBC analysis using the benzene polycarboxylic acid (BPCA) method. The results revealed the uncertainty of an earlier estimate of the atmospheric deposition flux of DBC to the global ocean (FDBC), which assumed a linear correlation between DBC and water‐soluble organic carbon (WSOC). The correlation between DBC and WSOC depended on the sources of carbonaceous aerosols. The DBC/WSOC ratios were higher for the biomass burning aerosols. DBC was linearly correlated with black carbon (BC) for biomass or fossil fuel combustion aerosols. However, the DBC/BC ratios were higher for biomass burning aerosols (0.41 ± 0.22), whereas lower for fossil fuel combustion aerosols (0.04 ± 0.03). FDBC was revisited based on the relationship between DBC and BC. FDBC is primarily contributed by biomass burning aerosols and maybe previously underestimated. In this study, the DBC in aerosols had less condensed aromatic structures than the DBC present in the major rivers of the world, as shown by the BPCA compositions. This indicated that oceanic DBC sourced from atmospheric deposition was less likely to be removed by photodegradation and sedimentation, as compared to the DBC sourced from riverine discharge. Plain Language Summary: Understanding the sources and environmental processes of dissolved black carbon (DBC) in the ocean is crucial because it helps determine the quantity of DBC in the ocean that will finally transform into CO2, thereby affecting the atmospheric CO2 stock and climate. The annual amount of DBC entering the ocean through atmospheric deposition (FDBC) was previously estimated based on a linear correlation between DBC and water‐soluble organic carbon (WSOC) in aerosols. In the present study, the correlation between DBC and WSOC was observed to be different for aerosols from various sources, such as biomass and fossil fuel combustion. The DBC/WSOC ratios were higher for biomass‐burning aerosols. DBC/black carbon (BC) ratios were also higher for biomass burning aerosols, whereas lower for fossil fuel combustion aerosols. A new estimate of FDBC was proposed, based on the relationship between DBC and BC, where FDBC was primarily contributed by biomass‐burning aerosols. DBC entering the ocean through atmospheric deposition had less condensed aromatic structures, as compared to DBC entering the ocean via rivers. This suggested that the former were less likely to be removed by photodegradation and sedimentation. Key Points: Correlation coefficient and the ratio of dissolved black carbon to water‐soluble organic carbon are relatively high for biomass burning aerosolsAtmospheric deposition flux of dissolved black carbon to the ocean is mainly contributed by biomass burning aerosolsThe dissolved black carbon in aerosols has less condensed aromatic structures than the major rivers of the world [ABSTRACT FROM AUTHOR]

Sea ice plays a critical role in the Earth's climate system, including influencing ocean heat uptake, reflecting solar radiation, and contributing to dense water formation. Instrumental records of polar sea ice extent are only available since 1979, however. The short length of such records also limits our knowledge of polynya variability, which can reflect large‐scale atmospheric and climate changes. Ice core proxy records can extend these observations, but require further development and regional validation. We compare chloride and methanesulfonic acid concentrations from two new firn cores from the Canadian Arctic with satellite‐derived observations of regional sea‐ice concentration and polynya variability from 2002 to 2014. The sub‐annual resolution of these cores allows for detailed investigation of how regional sea‐ice concentration is recorded in the ice at Prince of Wales Icefield (POW), Ellesmere Island and Devon Ice Cap (DIC), Devon Island, Nunavut. Over the period 2002–2014 we find that the primary sources of marine aerosols to POW are polynyas within Arctic Canada and the Canada basin of the Arctic Ocean, whereas the primary sources of marine aerosols to DIC are a broader region of the Queen Elizabeth Islands, Baffin Bay, and the Arctic Ocean. Marine aerosol sources to the two core sites are distinct, reflecting different moisture source regions and, likely, differing transport pathways. Air mass back trajectory results support the satellite‐derived results. Glaciochemical records from this dynamic, warming region may provide a proxy for reconstructing North Water polynya and other regional polynya and shore‐lead variability prior to the satellite era. Plain Language Summary: Sea ice plays a critical role in the Earth's climate system, yet instrumental records of polar sea ice extent are only available since 1979. The chemistry of ice cores can extend these observations farther back in time, but need to be validated over the satellite era first. In this study, we compare marine aerosol records from two new cores from the Canadian high Arctic with satellite‐derived observations of regional sea‐ice concentration from 2002 to 2014. Ice cores from this vital region are sparse, and recent surface warming across the Queen Elizabeth Islands heightens the urgency to develop histories of regional sea‐ice and environmental variability. We find that ice core records from this dynamic and warming region may provide a proxy for reconstructing sea‐ice variability prior to the satellite era in certain key regions of the Canadian Arctic Archipelago. Key Points: Marine aerosols to Prince of Wales, 2002–2014, are derived from Canadian Arctic polynyas and the Canada basin of the Arctic OceanMarine aerosols to Devon Ice Cap are derived from broader regions of the Queen Elizabeth Islands, Baffin Bay, and the Arctic OceanMarine aerosol sources to the two core sites are largely distinct, reflecting different moisture source regions and transport pathways [ABSTRACT FROM AUTHOR]

In this study, we investigate the occurrence of primary biological aerosol particles (PBAP) over all sectors of the Southern Ocean (SO) based on a 90‐day data set collected during the Antarctic Circumnavigation Expedition (ACE) in austral summer 2016–2017. Super‐micrometer PBAP (1–16 µm diameter) were measured by a wide band integrated bioaerosol sensor (WIBS‐4). Low (3σ) and high (9σ) fluorescence thresholds are used to obtain statistics on fluorescent and hyper‐fluorescent PBAP, respectively. Our focus is on data obtained over the pristine ocean, that is, more than 200 km away from land. The results indicate that (hyper‐)fluorescent PBAP are correlated to atmospheric variables associated with sea spray aerosol (SSA) particles (wind speed, total super‐micrometer aerosol number concentration, chloride and sodium concentrations). This suggests that a main source of PBAP over the SO is SSA. The median percentage contribution of fluorescent and hyper‐fluorescent PBAP to super‐micrometer SSA was 1.6% and 0.13%, respectively. We demonstrate that the fraction of (hyper‐)fluorescent PBAP to total super‐micrometer particles positively correlates with concentrations of bacteria and several taxa of pythoplankton measured in seawater, indicating that marine biota concentrations modulate the PBAP source flux. We investigate the fluorescent properties of (hyper‐)fluorescent PBAP for several events that occurred near land masses. We find that the fluorescence signal characteristics of particles near land is much more variable than over the pristine ocean. We conclude that the source and concentration of fluorescent PBAP over the open ocean is similar across all sampled sectors of the SO. Key Points: Fluorescent primary bioaerosol particles (PBAP) were measured over all sectors of the Southern OceanModerate to good correlations were observed between PBAP and sea spray aerosol (SSA) proxiesPBAP fractions in SSA were positively correlated to concentrations of certain marine biota [ABSTRACT FROM AUTHOR]

Natural aerosols in pristine regions form the baseline used to evaluate the impact of anthropogenic aerosols on climate. Sea spray aerosol (SSA) is a major component of natural aerosols. Despite its importance, the abundance of SSA is poorly constrained. It is generally accepted that wind-driven wave breaking is the principle governing SSA production. This mechanism alone, however, is insufficient to explain the variability of SSA concentration at given wind speed. The role of other parameters, such as sea surface temperature (SST), remains controversial. Here, we show that higher SST promotes SSA mass generation at a wide range of wind speed levels over the remote Pacific and Atlantic Oceans, in addition to demonstrating the wind-driven SSA production mechanism. The results are from a global scale dataset of airborne SSA measurements at 150 to 200 m above the ocean surface during the NASA Atmospheric Tomography Mission. Statistical analysis suggests that accounting for SST greatly enhances the predictability of the observed SSA concentration compared to using wind speed alone. Our results support implementing SST into SSA source functions in global models to better understand the atmospheric burdens of SSA. [ABSTRACT FROM AUTHOR]

Variability in atmospheric dimethylsulfide (DMSa) and the potential influence on atmospheric aerosols was investigated at Heron Island in the southern Great Barrier Reef (GBR), Australia. This work compiles previously published DMSa data (reported in Swan, Jones, Deschaseaux, & Eyre, 2017, https://doi.org/10.1007/s00216‐017‐0385‐8), with additional surveys of DMSa, atmospheric particle number concentration, and other oceanic and atmospheric data sets. DMSa was higher in summer (mean 3.2 nmol m−3/78 ppt) than winter (mean 1.3 nmol m−3/32 ppt), reflective of seasonal shifts in phytoplankton biomass and emissions from corals in the southern GBR. Seasonally extreme spikes in DMSa were detected during low tide and low wind speed, supporting findings that the coral reef can be an important source of DMSa above background oceanic emissions. A significant link was present between DMSa and aerosol concentration (ranging from 0.5 to 2.5 μm) during calm, daylight hours, when conditions were optimal for the local oxidation of DMSa to sulfate aerosol precursors. This link may reflect condensational growth of existing fine particles (< 0.5 μm), which is the dominant pathway by which biogenic trace gases influence aerosols in the marine boundary layer. Aerosol concentration significantly correlated with reduced surface solar irradiance and sea surface temperature, which is potential evidence of a local negative feedback mitigating coral physiological stress. These findings provide a step toward a better understanding of the processes influencing DMSa and aerosol concentrations and of the consequences for the local radiative balance over coral reefs; an increasingly important topic with ongoing ocean warming and coral bleaching. Key Points: Coral reefs are an important source of atmospheric dimethylsulfideA significant link exists between atmospheric dimethylsulfide and marine aerosols in the southern Great Barrier ReefMarine aerosols reduced surface solar irradiance and sea surface temperature, potentially mitigating coral physiological stress [ABSTRACT FROM AUTHOR]

Dimethyl sulfide (DMS), emitted from the oceans, is the most abundant biological source of sulfur to the marine atmosphere. Atmospheric DMS is oxidized to condensable products that form secondary aerosols that affect Earth's radiative balance by scattering solar radiation and serving as cloud condensation nuclei. We report the atmospheric discovery of a previously unquantified DMS oxidation product, hydroperoxymethyl thioformate (HPMTF, HOOCH2SCHO), identified through global-scale airborne observations that demonstrate it to be a major reservoir of marine sulfur. Observationally constrained model results show that more than 30% of oceanic DMS emitted to the atmosphere forms HPMTF. Coincident particle measurements suggest a strong link between HPMTF concentration and new particle formation and growth. Analyses of these observations show that HPMTF chemistry must be included in atmospheric models to improve representation of key linkages between the biogeochemistry of the ocean, marine aerosol formation and growth, and their combined effects on climate. [ABSTRACT FROM AUTHOR]

We report the first simultaneous eddy covariance flux measurements of CO2 and dimethylsulfide (DMS) over the open ocean for two North Atlantic cruises. After normalization for Schmidt number, the two gases give essentially identical gas transfer coefficients and wind speed dependences for the wind speed range 2–10 ms−1. The data indicate a linear relationship between the gas transfer coefficient and mean wind speed, with measured gas transfer coefficients slightly above the Wanninkhof (1992) parameterization, particularly at low wind speeds.

This study examines atmospheric reactive chlorine chemistry at the Cape Verde Atmospheric Observatory in the eastern tropical Atlantic. During May–June, 2007, Cl2 levels ranged from below detection (∼2 ppt) to 30 ppt. Elevated Cl2 was associated with high HNO3 (40 to 120 ppt) in polluted continental outflow transported in the marine boundary layer (MBL) to the site. Lower Cl2 was observed in recently subsided air masses with multiday free tropospheric oceanic trajectories and in air containing Saharan dust. Model simulations show that the observations of elevated Cl2 in polluted marine air are consistent with initiation of Cl chemistry by OH + HCl and subsequent heterogeneous, autocatalytic Cl cycling involving marine aerosols. Model estimates suggest that Cl atom reactions significantly impact the fates of methane and dimethylsulfide at Cape Verde and are moderately important for ozone cycling.

A flame emission aerosol sodium detector (ASD) has been developed to study the distribution of seasalt in individual marine aerosol droplets. The instrument detects sodium via D-line emission in a fuel-rich, laminar, hydrogen/oxygen/nitrogen flame. Laboratory studies with synthetic monodisperse aerosols were carried out in order to characterize the sensitivity, precision, and linearity of the technique. Experiments were also carried out with aerosols generated from mixed salt solutions and seawater in order to determine whether ionic or other matrix effects lead to interference. The ASD has a linear response function for NaCl aerosol particles from 100 nm to 2.0μm in diameter. The precision of sodium mass measurements is on the order of ±3% standard error on replicate measurements, with a quantitative response to the sodium content of a single aerosol particle that is independent of the chemical composition of the particle, i.e. anions, cations, seawater. No interferences were found with major ions in seawater and common atmospheric aerosols. These experiments demonstrate a detection limit equivalent to a 100 nm diameter dry 100% NaCl aerosol. Copyright © 2001 Elsevier Science Ltd.

The North Atlantic Aerosols and Marine Ecosystems Study (NAAMES) is an interdisciplinary investigation to improve understanding of Earth's ocean ecosystem-aerosol-cloud system. Specific overarching science objectives for NAAMES are to (1) characterize plankton ecosystem properties during primary phases of the annual cycle and their dependence on environmental forcings, (2) determine how these phases interact to recreate each year the conditions for an annual plankton bloom, and (3) resolve how remote marine aerosols and boundary layer clouds are influenced by plankton ecosystems. Four NAAMES field campaigns were conducted in the western subarctic Atlantic between November 2015 and April 2018, with each campaign targeting specific seasonal events in the annual plankton cycle. A broad diversity of measurements were collected during each campaign, including ship, aircraft, autonomous float and drifter, and satellite observations. Here, we present an overview of NAAMES science motives, experimental design, and measurements. We then briefly describe conditions and accomplishments during each of the four field campaigns and provide information on how to access NAAMES data. The intent of this manuscript is to familiarize the broad scientific community with NAAMES and to provide a common reference overview of the project for upcoming publications.

A study of temporal variations of particulate matter in different size fractions (TSP, PM10, PM2.5) was undertaken in the city of San Francisco de Campeche (SFC), in southeast Mexico, in the years 2014 and 2015 in order to assess the contribution of the chemical components. The samples were analyzed using X-ray fluorescence (XRF) and ion exchange chromatography (IC) for PM10. XRF identified the presence of Al, Si, P, S, K, Ca, Ti, Cr, Mn, Fe, Cu, and Zn. The results of a cluster analysis (CA) indicates a strong correlation of S and P in the three fractions due to agricultural land use and this may be related to the burning of biomass during the dry season. Also the CA also suggests that the elements Al, Si, K, Ca, Ti, Mn, and Fe can be associated with a geological origin. The results of the IC analysis show high levels of Na+, Cl−, and SO4−2 and the latter must be related to anthropogenic sources. The application of principal components analysis (PCA) suggests that Na+, Cl− and Mg+2 are associated with marine aerosols; NO3− and SO4−2 are from emissions related to fuel combustion due to increase in the number of motor vehicles in the city. [ABSTRACT FROM AUTHOR]

Methods for determining aerosol types in cases where chemical composition measurements are not available are useful for improved aerosol radiative forcing estimates. In this study, two aerosol characterization methods by Cazorla et al. (2013, https://doi.org/10.5194/acp-13-9337-2013; CA13) and Costabile et al. (2013, https://doi.org/10.5194/acp-13-2455-2013; CO13) using wavelength‐dependent particle absorption and scattering are used, to assess their applicability and examine their limitations. Long‐term ambient particle optical property and chemical composition (major inorganic ions and bulk carbon) measurements from the Maldives Climate Observatory Hanimaadhoo as well as concurrent air mass trajectories are utilized to test the classifications based on the determined absorption Ångström exponent, scattering Ångström exponent, and single scattering albedo. The resulting aerosol types from the CA13 method show a good qualitative agreement with the particle chemical composition and air mass origin. In general, the size differentiation using the scattering Ångström exponent works very well for both methods, while the composition identification depending mainly on the absorption Ångström exponent can result in aerosol misclassifications at Maldives Climate Observatory Hanimaadhoo. To broaden the applicability of the CA13 method, we suggest to include an underlying marine aerosol group in the classification scheme. The classification of the CO13 method is less clear, and its applicability is limited when it is extended to aerosols in this environment at ambient humidity. Key Points: Optical aerosol classifications conform reasonable well with chemical measurements and air mass origin analysisThe extension of optical characterization methods to a remote marine site is limited due to strong aerosol mixing and humidificationAn underlying sea spray category should be considered for optical aerosol characterization at sites with marine influence [ABSTRACT FROM AUTHOR]

A scientific campaign was undertaken along the Western sector of the Mediterranean Sea in the summer 2015 (26th Jun to 13th Jul), with the goal of gathering information about organic contaminants affecting marine aerosol over the Italian seas and with a special focus on changes in composition due to sources. 24 PM 10 atmospheric samples in total were chemically characterized, including polycyclic aromatic hydrocarbons (PAHs), aliphatic hydrocarbons (n -alkanes) and phthalate esters. Contemporarily, regulated gaseous toxicants (i.e. ozone, nitrogen oxides and sulfur dioxide) and meteorological parameters were recorded. Samplings were carried out inshore in front of harbors (N = 7) and along the cruise, both during the vessel shipping (N = 11, transects) and at its stops offshore (N = 6). Total PAH concentrations ranged from 0.03 to 1.94 ng/m3 and raised close to harbors and coastal sites, confirming that continental sources were responsible for the strong increase of pollution levels there compared to offshore. The percent composition and diagnostic ratio rates of PAHs were different for harbors, while transects were in agreement with offshore stops, possibly due to the different impact of pollution sources. n -Alkanes (C 21 C 38) and the corresponding carbon preference index rates (CPI) were assessed; their values ranged 8.7–90 ng/m3 and 1.1–2.9 respectively, which suggested that fossil fuel combustion was the dominant source, though biogenic emission could contribute. Alkyl phthalates revealed wide variability in concentrations among aerosol samples. Moreover, long-range atmospheric transport and particle ageing effect induced by photo-oxidants were important factors controlling the composition of organic aerosols in the Mediterranean Sea air. Image 1 • PAHs, n -alkanes and gaseous contaminants were valued in the air over Mediterranean Sea. • Relevant differences were observed in the marine air among the three site types. • Vehicles exhausts seemed to be one of the principal PAH sources near harbors. • This study underlined the role of both anthropogenic and biogenic sources. • The impact of natural events like volcanic ashes was detected in the Aeolian Islands area. The patterns of PAH s, n -alkanes and phthalate esters of atmospheric samples along Western sector of Mediterranean Sea were investigated in the frame of an oceanographic campaign. [ABSTRACT FROM AUTHOR]

Abstract Awareness of the importance of marine atmosphere for accurately estimating global aerosol budget and climate impacts has arisen recently. However, studies are limited due to the difficulty and inconvenience in sampling as well as the diversity of sources. In this study, the Community Multiscale Air Quality (CMAQ) model was applied to investigate the fine particulate matter (PM 2.5) and its chemical components over the East China Sea (ECS) and offshore regions. In spite of slight under-predictions, model predictions agree well with observations over the ECS and along the coast. PM 2.5 and its major components in the mainland are higher than in marine area, suggesting Asian continent is a major emitter of marine aerosols. PM 2.5 and its components in marine regions show higher abundance during daytime than nighttime, while it is opposite in continental regions. Aerosol phase SO 4 2− is the most abundant component of PM 2.5 over the ECS with an average concentration of 5.12 μg m−3, followed by NH 4 + (1.02 μg m−3) and primary organic aerosol (POA) (0.92 μg m−3). Industry and ship emissions are the top two contributors to primary (PPM) and total PM 2.5 over the ECS, while industry and agriculture sectors are major sources for secondary inorganic aerosols (SIA), followed by ship emissions. For terrestrial regions, industry and agriculture are predominant sources of PM 2.5 and SIA, while industry and residential activities are the top two contributors to PPM. This study improves the understanding of transport and accumulation of air pollutants over the ECS and adjacent regions, and provides useful information for designing efficient control strategies. Graphical abstract Unlabelled Image Highlights • PM 2.5 and components over the East China Sea and offshore regions were investigated. • Model predictions agree well with observations over the ECS and along the coast. • Emissions from China have significant effects on marine aerosols over the ECS. • SO 4 2− is the most abundant PM 2.5 component over the ECS, followed by NH 4 + and POA. • Industry and ship emissions are the top two contributors to total PM 2.5. [ABSTRACT FROM AUTHOR]

To understand the influences of continental emissions on marine aerosols from East Asia, the total suspended particle (TSP) samples were collected from the Yellow Sea (YS) and Bohai Sea (BS) of China through a cruise campaign during the spring of 2018. >100 individual organic compounds were identified and determined in the samples, and they were classified into 6 major groups according to the functionality and sources. The mass concentrations of total quantified organic compounds in BS (307.6 ± 268.3 ng m−3) was approximately 3 times those of YS (111.0 ± 97.3 ng m−3). Organic compounds from biomass burning (23.2 ± 34.2 ng m−3), marine/microbial source (23.1 ± 6.2 ng m−3) and fossil fuel combustion (21.4 ± 11.3 ng m−3) were the most abundant in the YS samples, whereas primary biological origins (90.0 ± 107.1 ng m−3), biomass burning (52.1 ± 39.1 ng m−3) and fossil fuel combustion (41.9 ± 20.1 ng m−3) were the most important organic species in BS marine aerosols. The concentrations of total biogenic secondary organic aerosol (BSOA) tracers including six isoprene SOA (SOA I), three monoterpene SOA (SOA M), and one β -caryophyllene SOA (SOA C) were 2.4 ± 1.5 ng m−3 and 7.3 ± 4.4 ng m−3 in the YS and BS samples, respectively. A strong correlation between BSOA tracers and levoglucosan was shown in the marine aerosol samples, indicating that biomass burning emissions could also promote BSOA formations. The spatial distribution of chemical and source characteristics suggests a relatively large impacts of continental emissions to the BS aerosols. Based on the tracer-based method, the biomass burning (YS: 4.9 ± 6.8%; BS: 8.8 ± 8.0%) was the largest contributor to OC, followed by primary biogenic OC (YS: 0.59 ± 0.44%; BS: 2.9 ± 3.0%) and biogenic secondary OC (YS: 0.45 ± 0.23%; BS: 1.0 ± 0.59%). This study suggests important contributions of biomass burning emissions to organic aerosols in the YS and BS marine atmosphere, although marine source, fossil fuel combustion and secondary formation was also substantial. [Display omitted] • Chemical and source characteristics of marine organic aerosols over the Bohai Sea and Yellow Sea were studied. • Biomass burning is a major contributor of marine organic aerosols over the Bohai Sea and Yellow Sea. • Biogenic primary emission contribution to organic carbon is higher than biogenic-derived secondary formation. • The Bohai Sea is more receptive to the input of continental emissions than the Yellow Sea. [ABSTRACT FROM AUTHOR]

In this study, the concentrations of marine aerosols estimated with the model CALPUFF (a multi-layer, multispecies, non-steady-state puff dispersion) were compared with the concentrations of PM10 monitored near the coast with minimum volume gravimetric equipment. It was found that the contribution of marine aerosols to the mass of PM10 can be significant, reaching between 20% and 27%. Concentrations between 5 and 15 μg/m3 were estimated on streets that are less than 100 meters from the beach. The maximum concentrations were found at the sampling point located offshore. The correlation was strong and positive at this same point (r2 = 0.65). In the dispersion analysis, the impact of marine aerosols was observed more than 20 km from the beach in the direction of the wind, with levels between 1.65 μg/m3 y 15.02 μg/m3. In the monitoring with the gravimetric equipment, a maximum concentration of PM10 of 77.98 μg/m3 and a minimum concentration of 2.82 μg/m3 was obtained. The results show that CALPUFF provides reasonable predictions of long-term marine pollutant deposition patterns. [ABSTRACT FROM AUTHOR]

Abstract The atmospheric deposition of water-soluble organic carbon (WSOC) contributes to the open ocean dissolved organic carbon (DOC) reservoir similarly to riverine discharge. However, information on the sources and composition of water-soluble organic matter (WSOM) in marine aerosols remains scarce, particularly at the molecular level. By using ultra-high resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS), we identified approximately ten thousand molecular formulas in marine aerosols collected over the China coastal seas and the northwestern Pacific Ocean (NWPO). Even though their molecular compositions were highly variable (Bray-Curtis distance: 0.12–0.74), four distinctive origins, namely, marine biogenic sources, secondary organic aerosols (including CHO, CHON formulas derived from biogenic volatile organic compounds (VOCs) and organosulfate derived from both biogenic and anthropogenic VOCs), soil-derived organic matter (OM) and biomass and fossil fuel burning-derived polycyclic aromatics (including highly condensed organosulfur compounds) and unsaturated compounds, were discovered. Moreover, the different types of aerosols, including aerosols from the NWPO (marine-influenced), NWPO (dust) and China coastal seas, contained various proportions of organics from different sources. The NWPO (marine-influenced) aerosols were enriched with sea spray-derived OM, which was widely distributed and was likely related to marine biological activity. The NWPO (dust) aerosols exhibited a higher fraction of soil-derived OM, while the China coastal sea aerosols exhibited a much higher fraction of organosulfate than the other aerosols. Our investigation provided detailed molecular compositional and source information for marine aerosols over the northwestern Pacific Ocean, which can be utilized to understand the composition of WSOM deposited on the sea surface. Highlights • Approximately ten thousand of molecular formulas were identified in marine aerosols. • Anthropogenic organic matter can be transported to the open ocean. • Sea spray compounds were widely observed but were enriched in the open ocean aerosols. • China coastal seas aerosols contained higher fraction of organosulfate compounds. • Dust aerosols exhibited a higher fraction of soil-derived organic matter. [ABSTRACT FROM AUTHOR]

Abstract: Marine aerosols consist of a variety of compounds and play an important role in many atmospheric processes. In the present study, sodium iodide clusters with their simple isotope pattern serve as model systems for laboratory studies to investigate the role of iodide in the photochemical processing of sea‐salt aerosols. Salt clusters doped with camphor, formate and pyruvate are studied in a Fourier transform ion cyclotron resonance mass spectrometer (FT‐ICR MS) coupled to a tunable laser system in both UV and IR range. The analysis is supported by ab initio calculations of absorption spectra and energetics of dissociative channels. We provide quantitative analysis of IRMPD measurements by reconstructing one‐photon spectra and comparing them with the calculated ones. While neutral camphor is adsorbed on the cluster surface, the formate and pyruvate ions replace an iodide ion. The photodissociation spectra revealed several wavelength‐specific fragmentation pathways, including the carbon dioxide radical anion formed by photolysis of pyruvate. Camphor and pyruvate doped clusters absorb in the spectral region above 290 nm, which is relevant for tropospheric photochemistry, leading to internal conversion followed by intramolecular vibrational redistribution, which leads to decomposition of the cluster. Potential photodissociation products of pyruvate in the actinic region may be formed with a cross section of <2×10−20 cm2, determined by the experimental noise level. [ABSTRACT FROM AUTHOR]

Investigating the nature of PM 10 is crucial to differentiate sources and their relative contributions. In this study we compared the levels, and the chemical and mineralogical properties of PM 10 particles sampled in different seasons at monitoring stations representative of urban background, urban traffic and suburban traffic areas of Naples city. The aims were to relate the PM 10 load and characteristics to the location of the monitoring stations, to investigate the different sources contributing to PM 10 and to highlight PM 10 seasonal variability. Bulk analyses of chemical species in the PM 10 fraction included total carbon and nitrogen, δ 13 C and other 20 elements. Both natural and anthropogenic sources were found to contribute to the exceedances of the EU PM 10 limit values. The natural contribution was mainly related to marine aerosols and soil dust, as highlighted by X-ray diffractometry and SEM-EDS microscopy. The percentage of total carbon suggested a higher contribution of biogenic components to PM 10 in spring. However, this result was not supported by the δ 13 C values which were seasonally homogeneous and not sufficient to extract single emission sources. No significant differences, in terms of PM 10 load and chemistry, were observed between monitoring stations with different locations, suggesting a homogeneous distribution of PM 10 on the studied area in all seasons. The anthropogenic contribution to PM 10 seemed to dominate in all sites and seasons with vehicular traffic acting as a main source mostly by generation of non-exhaust emissions Our findings reinforce the need to focus more on the analysis of PM 10 in terms of quality than of load, to reconsider the criteria for the classification and the spatial distribution of the monitoring stations within urban and suburban areas, with a special attention to the background location, and to emphasize all the policies promoting sustainable mobility and reduction of both exhaust and not-exhaust traffic-related emissions. [ABSTRACT FROM AUTHOR]

Fine particles (PM 2.5 ) samples, collected at Weizhou Island over the Gulf of Tonkin on a daytime and nighttime basis in the spring of 2015, were analyzed for primary and secondary organic tracers, together with organic carbon (OC), elemental carbon (EC), and stable carbon isotopic composition (δ 13 C) of total carbon (TC). Five organic compound classes, including saccharides, lignin/resin products, fatty acids, biogenic SOA tracers and phthalic acids, were quantified by gas chromatography/mass spectrometry (GC/MS). Levoglucosan was the most abundant organic species, indicating that the sampling site was under strong influence of biomass burning. Based on the tracer-based methods, the biomass-burning-derived fraction was estimated to be the dominant contributor to aerosol OC, accounting for 15.7% ± 11.1% and 22.2% ± 17.4% of OC in daytime and nighttime samples, respectively. In two episodes E1 and E2, organic aerosols characterized by elevated concentrations of levoglucosan as well as its isomers, sugar compounds, lignin products, high molecular weight (HMW) fatty acids and β -caryophyllinic acid, were attributed to the influence of intensive biomass burning in the northern Southeast Asia (SEA). However, the discrepancies in the ratios of levoglucosan to mannosan (L/M) and OC (L/OC) as well as the δ 13 C values suggest the type of biomass burning and the sources of organic aerosols in E1 and E2 were different. Hardwood and/or C 4 plants were the major burning materials in E1, while burning of softwood and/or C 3 plants played important role in E2. Furthermore, more complex sources and enhanced secondary contribution were found to play a part in organic aerosols in E2. This study highlights the significant influence of springtime biomass burning in the northern SEA to the organic molecular compositions of marine aerosols over the Gulf of Tonkin. [ABSTRACT FROM AUTHOR]

Marine sulfate aerosols in the Southern Ocean are critical to the global radiation balance, yet the sources of sulfate and their seasonal variations are unclear. We separately sampled marine and ambient aerosols at Baring Head, New Zealand for 1 year using two collectors and evaluated the sources of sulfate in coarse (1–10 μm) and fine (0.05–1 μm) aerosols using sulfur isotopes (δ34S). In both collectors, sea‐salt sulfate (SO42−SS) mainly existed in coarse aerosols and nonsea‐salt sulfate (SO42−NSS) dominated the sulfate in fine aerosols, although some summer SO42−NSS appeared in coarse particles due to aerosol coagulation. SO42−NSS in the marine aerosols was mainly (88–100%) from marine biogenic dimethylsulfide (DMS) emission, while the SO42−NSS in the ambient aerosols was a combination of DMS (73–79%) and SO2 emissions from shipping activities (~21–27%). The seasonal variations of SO42−NSS concentrations inferred from the δ34S values in both collectors were mainly controlled by the DMS flux. [ABSTRACT FROM AUTHOR]

The traditional voltammetric method at the mercury electrode, and an acidification step developed for the determination of reduced sulfur species (RSS) in natural waters, was for the first time used for the quantification of RSS in the water-soluble fraction of fine marine aerosols collected at the Middle Adriatic location (Rogoznica Lake). The evidence of two types of non-volatile RSS that have different interaction with the Hg electrode was confirmed: mercapto-type which complexes Hg as RS−Hg and sulfide/S0-like compounds which deposits HgS. The analytical protocol that was used for RSS determination in aerosol samples is based on separate voltammetric studies of a methyl 3-mercaptopropionate (3-MPA) as a representative of mercapto-type compounds and sulfide as a representative of inorganic RSS. Our preliminary study indicates the presence of mainly RS−Hg compounds in spring samples, ranging from 2.60−15.40 ng m−3, while both, the mercapto-type (0.48−2.23 ng m−3) and sulfide and/or S0-like compounds (0.02−0.26 ng m−3) were detected in early autumn samples. More expressed and defined RS−Hg peaks recorded in the spring potentially indicate their association with biological activity in the area. Those samples were also characterized by a higher water-soluble organic carbon content and a more abundant surface-active fraction, pointing to enhanced solubility and stabilization of RSS in the aqueous atmospheric phase.

Total suspended particle (TSP) samples were collected during a marine cruise in the East China Sea from May 18 to June 12, 2014. They were analyzed for solvent extractable organic compounds (lipid compounds, PAHs and phthalates) using gas chromatography/mass spectrometry (GC/MS) to better understand the sources and source apportionment of aerosol pollution in the western North Pacific. Higher concentrations were observed in the terrestrially influenced aerosol samples on the basis of five-day backward air mass trajectories, especially for aerosols collected near coastal areas. Phthalates were found to be the dominant species among these measured compound classes (707 ± 401 ng m − 3 for daytime and 313 ± 155 ng m − 3 for nighttime), followed by fatty acids, fatty alcohols, n -alkanes and PAHs. In general, the daytime abundances for these compounds are higher than nighttime, possibly attributable to more intensive anthropogenic activities during the daytime. The factor analysis indicates that biomass burning, fungal activities and fossil fuel combustion maybe the main emission sources for organic aerosols over the East China Sea. This study demonstrates that the East Asian continent can be a natural emitter of biogenic and anthropogenic organics to the marine atmosphere through long-range transport, which controls the chemical composition and concentration of organic aerosols over the East China Sea. [ABSTRACT FROM AUTHOR]