Oceanic Emissions Research Articles

Characterizing Sources and Health Risks of Airborne Carbonyl Compounds in a Subtropical Coastal Atmosphere in South China.

Carbonyl compounds are critical air pollutants with adverse impacts on regional air quality and human health. This study presents a pioneering analysis of spatiotemporal distribution, source appointment, and health risk assessments of carbonyl compounds in the coastal marine atmosphere. By combining ship-borne and ground-based sampling followed with enhanced chemical analysis, 39 carbonyls were identified and quantified in the coastal Hong Kong. Carbonyl concentrations were generally higher in late summer/autumn with lower levels in winter, correlating with their secondary formation rates from precursors. Most species exhibited higher concentrations in open waters than in the fairway and sea channels, due to prominent photochemical formation from regional outflows in the Pearl River Estuary. In contrast, α, β-unsaturated aliphatic aldehydes and acetone were elevated in harbor areas, highlighting the influence of ship emissions on these compounds. Source analysis further indicated a notable contribution from ocean emissions to long-chain aldehydes (C≥6), acetone and di-aldehydes. Health risk assessment demonstrated that carbonyl compounds pose substantial carcinogenic and non-carcinogenic risks to maritime workers and other exposed populations, even exceeding risks faced by road workers. These findings underscore the necessity of considering carbonyl compounds in occupational exposure risk assessments. Overall, this study provides a comprehensive overview of carbonyl compounds in the coastal marine atmosphere, shedding light on the interactions among ship emissions, ocean activities and coastal urban emissions on airborne carbonyls and emphasizing the associated health implications.

Particle-bound mercury in Saharan dust-loaded particulate matter in Cabo Verde.

Particle-bound mercury (PBM) concentrations in particulate matter (PM), PM10 and PM2.5, were investigated during dust and non-dust events at urban and rural sites in Cabo Verde, Africa. During dust events, PBM averaged 35.2 pg m-3 (PM10) and 16.1 pg m-3 (PM2.5) compared to 15.9 pg m-3 (PM10) and 1.21 pg m-3 (PM2.5) during non-dust events representing 2.21- and 13.3-fold increases, respectively. The PM10/PM2.5 PBM ratio was 2.19 during dust and 13.1 in non-dust events, highlighting the role of coarse particles during non-dust periods. Air mass trajectories and elemental markers associate PBM sources to mineral dust, mining, oceanic emissions, and biomass burning. Health risk assessment indicates higher inhalation risk compared to dermal or ingestion pathways. By comparing the PBM concentrations during dust and non-dust events, for PM10, dust and long-range transport contributed about 63 % to the average PBM concentration in urban and 52 % in the rural areas and enriched PBM levels in PM2.5 by about 84 % (urban) and 94 % (rural). This result indicates that fine-mode PM is significantly enriched with PBM during dust events, elevating exposure risks and associated health impacts.

Atmospheric CO2 column concentration over Iran: Emissions, GOSAT satellite observations, and WRF-GHG model simulations

Regarding global warming and climate change, carbon dioxide (CO2) is one of the most important greenhouse gases. Simulating CO2 gas at hourly/weekly time intervals and desired vertical resolution is challenging due to the coarse horizontal resolution of global models. In this study, both column-averaged CO2 mixing ratio (XCO2) and vertical cross sections of CO2 mixing ratio were simulated by the Weather Research and Forecast Green House gas (WRF-GHG) model at spatial resolutions of 30 and 10 km for the Middle East region as the first domain, and Iran as the second domain. Simulations consider the primary CO2 sources (anthropogenic, biogenic, fire, and oceanic) and the Copernicus Atmosphere Monitoring Service (CAMS) dataset. XCO2 retrieved from GOSAT satellite observations was employed to evaluate the simulation results of the column-averaged CO2 concentrations in February and August 2010. The evaluations showed that the spatiotemporal variability of meteorological variables was well simulated by WRF-GHG with correlation coefficients r of 0.86–0.92, 0.67–0.75, and 0.76–0.82 for temperature, wind, and relative humidity, respectively, during February and August 2010. The evaluations also indicated that the WRF-GHG simulations outperformed the global model TM3, with mean bias error values of − 0.79 and 0.45 PPMV for WRF-GHG in February and August, respectively. The percentage contribution of net CO2 emissions from human activities in Iran was calculated as (38.33 % and 23.70 %) of the total emissions, respectively, with values of 4.4 and 0.85 kg/km2 in each month. The net emissions contributions of biogenic, fire, and oceanic sources were evaluated in February and August, with biogenic emissions contributing (31.901 % and 27.66 %), biogenic absorption contributing (24.07 % and 46.63 %), fire emissions contributing (5.7 % and 2.064 %), and oceanic emissions contributing (3.23 × 10−6 % and 2.23 × 10−6 %). Large-scale circulations and biogenic activity are responsible for the major features of the spatial and seasonal distribution of CO2 in the area. In February, column mixing ratios are higher in more northern latitudes; in August, they are higher to the south. Furthermore, the simulated vertical cross sections show high CO2 mixing ratios in the mid-lower troposphere and northerly/northeasterly advection in February; the vertical profile is inverted in August with high concentrations in the lower stratosphere associated with southwesterly advection. However, the interaction between the synoptic and sub-synoptic features with the topography determines the precise dispersion and distribution of CO2. Despite the negligible emissions in central and eastern Iran, these factors play an important role in the observed concentrations in February and August. In August, the areas between the 120-day low-level monsoon flow of Sistan in eastern Iran, and the westerlies over western/southwestern Iran and the Zagros Mountain range, interact with the heat-low in the Iranian plains and with the Arabian subtropical high. In February, the dominant winds in western Asia were west winds, with the main source of pollution coming from the northeastern regions flowing towards central and eastern Iran. The equatorward displacement of the polar jet stream and the passage of low-pressure systems from the west in winter cause a temporary reduction in CO2 concentrations.

Source-specific health effects of internally exposed organics in urban PM2.5 based on human serum albumin adductome analysis

Once inhaled, organic compounds in ambient PM2.5 permeate the bloodstream, resulting in internal exposure. The intricate composition of these internalized organic molecules complicates the processes of source attribution and toxicity assessment. A systematic framework to assess the health impacts of water-soluble organic molecules (WSOMs) originating from diverse sources is still undeveloped. This study aims to comprehensively analyze the source-specific health effects of internalized organics in urban PM2.5 through human serum albumin (HSA) non-covalent adductomes with WSOMs. Using high-resolution mass spectrometry, surface plasmon resonance, and machine learning, we mapped HSA-WSOM interactions, uncovering WSOM's potential internal exposure through its HSA adductome. The study identified eight distinct sources of internalized WSOMs, primarily from biogenic emissions, gasoline exhaust, and biomass combustion. Notably, WSOMs from these sources exhibited a predominant interaction with HSA residues ARG257, LEU238, and TRP150, substantially altering the functional dynamics of fatty acid binding site two and the hydrophobic cavity via hydrogen bonding and hydrophobic interactions. The primary health impacts of internalized WSOMs were identified as neurotoxicity and respiratory toxicity. WSOMs originating from biogenic sources and ocean emissions were mainly responsible for neurotoxic effects, whereas those from biomass burning and gasoline exhaust predominantly caused respiratory toxicity. Using the HSA adductome framework, our study identifies source-specific profiles and health effects of internally exposed WSOMs in urban PM2.5, emphasizing the importance of targeted mitigation strategies.

A 20-year (1998–2017) global sea surface dimethyl sulfide gridded dataset with daily resolution

Abstract. The oceanic emission of dimethyl sulfide (DMS) plays a vital role in the Earth's climate system and constitutes a substantial source of uncertainty when evaluating aerosol radiative forcing. Currently, the widely used monthly climatology of sea surface DMS concentration falls short of meeting the requirement for accurately simulating DMS-derived aerosols with chemical transport models. Hence, there is an urgent need for a high-resolution, multi-year global sea surface DMS dataset. Here we develop an artificial neural network ensemble model that uses nine environmental factors as input features and captures the variability of the DMS concentration across different oceanic regions well. Subsequently, a global sea surface DMS concentration and flux dataset (1° × 1°) with daily resolution spanning from 1998 to 2017 is established. According to this dataset, the global annual average concentration was ∼ 1.71 nM, and the annual total emissions were ∼ 17.2 Tg S yr−1, with ∼ 60 % originating from the Southern Hemisphere. While overall seasonal variations are consistent with previous DMS climatologies, notable differences exist in regional-scale spatial distributions. The new dataset enables further investigations into daily and decadal variations. Throughout the period 1998–2017, the global annual average concentration exhibited a slight decrease, while total emissions showed no significant trend. The DMS flux from our dataset showed a stronger correlation with the observed atmospheric methanesulfonic acid concentration compared to those from previous monthly climatologies. Therefore, it can serve as an improved emission inventory of oceanic DMS and has the potential to enhance the simulation of DMS-derived aerosols and associated radiative effects. The new DMS gridded products are available at https://doi.org/10.5281/zenodo.11879900 (Zhou et al., 2024).

Rapid cycling and emission of volatile sulfur compounds in the eastern Indian Ocean: Impact of runoff inputs and implications for balancing atmospheric carbonyl sulfide budget

Volatile sulfur compounds, such as dimethyl sulfide (DMS), carbonyl sulfide (OCS), and carbon disulfide (CS2), significantly influence atmospheric chemistry and climate change. Despite the oceans being an important source of these sulfides, the limited understanding of their biogeochemical cycles in seawater introduces considerable uncertainties in quantifying their oceanic emissions and assessing atmospheric OCS budgets. To address this issue, we conducted a comprehensive field survey in the tropical eastern Indian Ocean (EIO) to examine the spatial distributions, source-sink dynamics, and sea-air exchange fluxes of marine DMS, OCS, and CS2. Our study indicates that nutrients, organic matter, and freshwater input from terrestrial runoff significantly affect most of the source-sink processes of these sulfides in the Bay of Bengal and even the tropical EIO. The resulting sulfide accumulation in seawater combined with high wind speeds establishes the tropical EIO as a considerable direct and indirect atmospheric OCS source. These insights underscore the potentially critical role of marine environments influenced by runoff in contributing to the atmospheric OCS budget. However, by integrating these results with previous field surveys, we believe that actual OCS emissions from tropical oceans exceed some bottom-up box-model simulations, yet fall significantly below those predicted by top-down models, still insufficient to bridge the atmospheric OCS source gap. Our detailed examination of source-sink dynamics offers deeper insights into the marine sulfur cycle and has potential implications for refining future box-models, thus mitigating uncertainties in estimating marine sulfur emissions.

Carbonyl sulfide measurements from a South Pole ice core and implications for atmospheric variability since the last glacial period

Abstract. Carbonyl sulfide (COS) is the most abundant sulfur gas in the atmosphere with links to terrestrial and oceanic productivity. We measured COS in ice core air from an intermediate-depth ice core from the South Pole using both dry and wet extraction methods, recovering a 52 500-year record. We find evidence for COS production in the firn, altering the atmospheric signal preserved in the ice core. Mean sea salt aerosol concentrations from the same depth are a good proxy for the COS production, which disproportionately impacts the measurements from glacial period ice with high sea salt aerosol concentrations. The COS measurements are corrected using sea salt sodium (ssNa) as a proxy for the excess COS resulting from the production. The ssNa-corrected COS record displays substantially less COS in the glacial period atmosphere than the Holocene and a 2 to 4-fold COS rise during the deglaciation synchronous with the associated climate signal. The deglacial COS rise was primarily source driven. Oceanic emissions in the form of COS, carbon disulfide (CS2), and dimethylsulfide (DMS) are collectively the largest natural source of atmospheric COS. A large increase in ocean COS emissions during the deglaciation suggests enhancements in emissions of ocean sulfur gases via processes that involve ocean productivity, although we cannot quantify individual contributions from each gas.

Observed APO Seasonal Cycle in the Pacific: Estimation of Autumn O2 Oceanic Emissions

AbstractIn this work, we investigated the seasonal cycle of atmospheric potential oxygen (APO), a unique tracer of air‐sea gas exchanges of molecular oxygen (O2) and carbon dioxide (CO2), expressed as APO = O2 + 1.1 × CO2. APO data were obtained from flask air samples collected since the late 1990s at three Japanese ground stations and on commercial cargo ships sailing between Japan and Australia/New Zealand, North America, and Southeast Asia. We also analyzed the APO spatial distribution and seasonal cycles with simulations from an atmospheric transport model using climatological oceanic O2 fluxes from an empirical product that relate O2 flux to ocean heat as input. Model simulations reproduced the observed APO seasonal cycles generally well, but with larger amplitudes and earlier occurrence of seasonal minima and maxima than in the observations. Moreover, the observed seasonal cycles exhibited larger APO enhancements than the simulations in autumn and early winter, especially in the North Pacific at 20°N–60°N. These enhancements remained when refining the comparison by adjusting the simulated APO peak‐to‐peak amplitudes and seasonal phases to the observations. This suggests additional O2 emissions in the North Pacific, not well expressed in the air‐sea O2 fluxes used as input for our model simulations. The average autumn enhancement at 40°N–60°N was approximately twice that measured at 20°N–40°N. Confirming previous studies, our results indicate two distinct mechanisms possibly contributing to the additional oceanic O2 emissions: outgassing from a subsurface shallow oxygen maximum at 20°N–40°N and autumn phytoplankton bloom at 40°N–60°N.

Multi-process atmospheric particle number size distribution over the Bohai Sea: Insights from cruise and onboard unmanned aerial vehicle observations

A better understanding of the particle number size distribution aids to better assess the direct and indirect effects of particles on air quality and climate. In this study, particle number concentrations (PNCs) and size distribution along with chemical components, gaseous pollutants, and meteorological parameters were measured during a cruise campaign over the Bohai Sea. Four distinct periods were identified, showing significant impacts from continental outflows and ocean emissions on the particle number size distributions. Under the strong terrestrial pollution transport period, an obvious increase of PNCs below 1 μm was observed. The significant correlation between black carbon (BC) and PNCs in the size range of 0.35–1.0 μm suggested aging of aerosols during the long-range transport. An invaded dust pollution significantly reduced PNCs below 0.5 μm, while tripled the number concentration of particles larger than 0.5 μm. The ocean moisture facilitated the mixing between dust and secondary aerosols. An intense sea fog event observed during the cruise slightly increased PNCs smaller than 1 μm while decreasing larger ones. The correlations between PNCs below 0.5 μm and BC as well as SO2 demonstrated the impact of shipping activities on the formation of fresh particles. Aerosol vertical profiles in the marine boundary layer were measured by an unmanned aerial vehicle platform. The vertical patterns of particle number size distribution were largely governed by the origins of transported air masses and profiles of wind fields. Observations showed that the particle distribution in the lower marine boundary layer was typically inhomogeneous and rapidly evolving with time, highlighting the importance of strengthening the vertical observations of atmospheric parameters over the ocean.

Natural marine bromoform emissions in the fully coupled ocean–atmosphere model NorESM2

Abstract. Oceanic bromoform (CHBr3) is an important precursor of atmospheric bromine. Although highly relevant for the future halogen burden and ozone layer in the stratosphere, global CHBr3 production in the ocean and its emissions are still poorly constrained in observations and are mostly neglected in climate models. Here, we newly implement marine CHBr3 in the second version of the state-of-the-art Norwegian Earth System Model (NorESM2) with fully coupled interactions of ocean, sea ice, and atmosphere. Our results are validated using oceanic and atmospheric observations from the HalOcAt (Halocarbons in the Ocean and Atmosphere) database. The simulated mean oceanic concentrations (6.61 ± 3.43 pmol L−1) are in good agreement with observations from open-ocean regions (5.02 ± 4.50 pmol L−1), while the mean atmospheric mixing ratios (0.76 ± 0.39 ppt) are lower than observed but within the range of uncertainty (1.45 ± 1.11 ppt). The NorESM2 ocean emissions of CHBr3 (214 Gg yr−1) are within the range of or higher than previously published estimates from bottom-up approaches but lower than estimates from top-down approaches. Annual mean fluxes are mostly positive (sea-to-air fluxes); driven by oceanic concentrations, sea surface temperature, and wind speed; and dependent on season and location. During winter, model results imply that some oceanic regions in high latitudes act as sinks of atmospheric CHBr3 due to their elevated atmospheric mixing ratios. We further demonstrate that key drivers for oceanic and atmospheric CHBr3 variability are spatially heterogeneous. In the tropical West Pacific, which is a hot spot for oceanic bromine delivery to the stratosphere, wind speed is the main driver for CHBr3 fluxes on an annual basis. In the North Atlantic, as well as in the Southern Ocean region, atmospheric and oceanic CHBr3 variabilities interact during most of the seasons except for the winter months, when sea surface temperature is the main driver. Our study provides an improved process-based understanding of the biogeochemical cycling of CHBr3 and more reliable natural emission estimates, especially on seasonal and spatial scales, compared to previously published model estimates.

Photothermal conditions and upwelling enhance very short-lived brominated halocarbons emissions in the western tropical Pacific Ocean

Sea-to-air emissions of very short-lived brominated halocarbons (VSLBrHs) are known to contribute to 30 % of stratospheric and tropospheric ozone depletion. However, empirical data on their occurrence in open ocean are scarce, which makes it difficult to estimate the significant contribution of open ocean releases to the global budget of halocarbons. This study was conducted in 2022 to explore the spatial variations of VSLBrHs and their controlling factors in the western tropical Pacific Ocean (WTPO). The findings highlighted that high biological productivity and the resulting dissolved organic matter (DOM) as well as upwelling dynamics significantly influenced the distribution and production of VSLBrHs in seawater, with atmospheric levels primarily governed by oceanic emissions. Based on the simultaneous observation of seawater and atmospheric concentrations, the mean sea-to-air fluxes of CH2Br2, CHBr3, CHBrCl2, and CHBr2Cl were estimated to be 1.01, 6.65, 9.31, and 7.25 nmol m−2 d−1, respectively. Sea-to-air fluxes of these gases in the upwelling regions were 9.0, 4.6, 2.9, and 6.8 times those in the non-upwelling regions, respectively. Additionally, in-situ incubation experiments revealed that the enzymatic mediated biosynthesis pathways of VSLBrHs were enhanced under temperature and light-induced stress and in waters rich in humus-like substances. Therefore, we tentatively concluded that abundant photothermal conditions and the existence of upwelling in the WTPO made it a potential hotspot for the emission of VSLBrHs. This study offers critical insights into the environmental dynamics of VSLBrHs emissions and underscores the importance of regional oceanic conditions in influencing atmospheric greenhouse gas compositions.

Atmospheric isoprene measurements reveal larger-than-expected Southern Ocean emissions

Isoprene is a key trace component of the atmosphere emitted by vegetation and other organisms. It is highly reactive and can impact atmospheric composition and climate by affecting the greenhouse gases ozone and methane and secondary organic aerosol formation. Marine fluxes are poorly constrained due to the paucity of long-term measurements; this in turn limits our understanding of isoprene cycling in the ocean. Here we present the analysis of isoprene concentrations in the atmosphere measured across the Southern Ocean over 4 months in the summertime. Some of the highest concentrations ( >500 ppt) originated from the marginal ice zone in the Ross and Amundsen seas, indicating the marginal ice zone is a significant source of isoprene at high latitudes. Using the United Kingdom Earth System Model we show that current estimates of sea-to-air isoprene fluxes underestimate observed isoprene by a factor >20. A daytime source of isoprene is required to reconcile models with observations. The model presented here suggests such an increase in isoprene emissions would lead to >8% decrease in the hydroxyl radical in regions of the Southern Ocean, with implications for our understanding of atmospheric oxidation and composition in remote environments, often used as proxies for the pre-industrial atmosphere.

Anthropogenic short-lived halogens increase human exposure to mercury contamination due to enhanced mercury oxidation over continents

Mercury (Hg) is a contaminant of global concern, and an accurate understanding of its atmospheric fate is needed to assess its risks to humans and ecosystem health. Atmospheric oxidation of Hg is key to the deposition of this toxic metal to the Earth's surface. Short-lived halogens (SLHs) can provide halogen radicals to directly oxidize Hg and perturb the budget of other Hg oxidants (e.g., OH and O3). In addition to known ocean emissions of halogens, recent observational evidence has revealed abundant anthropogenic emissions of SLHs over continental areas. However, the impacts of anthropogenic SLHs emissions on the atmospheric fate of Hg and human exposure to Hg contamination remain unknown. Here, we show that the inclusion of anthropogenic SLHs substantially increased local Hg oxidation and, consequently, deposition in/near Hg continental source regions by up to 20%, thereby decreasing Hg export from source regions to clean environments. Our modeling results indicated that the inclusion of anthropogenic SLHs can lead to higher Hg exposure in/near Hg source regions than estimated in previous assessments, e.g., with increases of 8.7% and 7.5% in China and India, respectively, consequently leading to higher Hg-related human health risks. These results highlight the urgent need for policymakers to reduce local Hg and SLHs emissions. We conclude that the substantial impacts of anthropogenic SLHs emissions should be included in model assessments of the Hg budget and associated health risks at local and global scales.

Sources and Distribution of Light NMHCs in the Marine Boundary Layer of the Northern Indian Ocean During Winter: Implications to Aerosol Formation

AbstractNon‐methane hydrocarbons (NMHCs) are ubiquitous trace gases and profoundly affect the Earth's atmosphere and climate change. Mixing ratios of light NMHCs were measured over the northern Indian Ocean during winter‐2018 as part of the Integrated Campaign for Aerosols, gases, and Radiation Budget (ICARB‐2018). Higher levels of NMHCs over the coastal regions were due to the efficient transport of anthropogenic and biogenic air masses and higher air‐sea exchanges due to the higher biological productivity. Although oceanic emissions dominated the open ocean, the transport of aged continental air also influenced the levels of some NMHCs. The higher and lower propane/ethane ratios of 2.41 ± 0.34 and 1.13 ± 0.78 ppbv ppbv−1 over coastal and open oceans indicated the prevalence of fresh and aged air masses, respectively. Ethene and propene show a strong correlation, but the ethene/propene ratios over open ocean (2.2 ± 0.25 ppbv ppbv−1) were slightly lower than the coastal region (2.5 ± 0.34 ppbv ppbv−1). Principal component analysis reveals the major associated sources identified in this study are from oceanic and nearby anthropogenic sources, explaining nearly 51% and 21% of variance. Light alkenes accounted for ∼70% of the total ozone and secondary organic aerosol formation potential. A higher alkene/alkane ratio, strong correlation of alkene with organic aerosol mass, and new particle formation events highlight the role of alkenes in secondary aerosol formation over the equatorial Indian Ocean. Overall, the levels of NMHCs were much higher than those measured nearly two decades ago during the Indian Ocean Experiment (INDOEX)‐1999.

Marine carbohydrates in Arctic aerosol particles and fog – diversity of oceanic sources and atmospheric transformations

Abstract. Carbohydrates, originating from marine microorganisms, enter the atmosphere as part of sea spray aerosol (SSA) and can influence fog and cloud microphysics as cloud condensation nuclei (CCN) or ice-nucleating particles (INP). Particularly in the remote Arctic region, significant knowledge gaps persist about the sources, the sea-to-air transfer mechanisms, atmospheric concentrations, and processing of this substantial organic group. In this ship-based field study conducted from May to July 2017 in the Fram Strait, Barents Sea, and central Arctic Ocean, we investigated the sea-to-air transfer of marine combined carbohydrates (CCHO) from concerted measurements of the bulk seawater, the sea surface microlayer (SML), aerosol particles and fog. Our results reveal a wide range of CCHO concentrations in seawater (22–1070 µg L−1), with notable variations among different sea-ice-related sea surface compartments. Enrichment factors in the sea surface microlayer (SML) relative to bulk water exhibited variability in both dissolved (0.4–16) and particulate (0.4–49) phases, with the highest values in the marginal ice zone (MIZ) and aged melt ponds. In the atmosphere, CCHO was detected in super- and submicron aerosol particles (CCHOaer,super: 0.07–2.1 ng m−3; CCHOaer,sub: 0.26–4.4 ng m−3) and fog water (CCHOfog,liquid: 18–22 000 µg L−1; CCHOfog,atmos: 3–4300 ng m−3). Enrichment factors for sea–air transfer varied based on assumed oceanic emission sources. Furthermore, we observed rapid atmospheric aging of CCHO, indicating both biological/enzymatic processes and abiotic degradation. This study highlights the diverse marine emission sources in the Arctic Ocean and the atmospheric processes shaping the chemical composition of aerosol particles and fog.

What factors cause ocean CO2? A panel data analysis.

Over the past three decades, industrial innovations and technological advancements have changed business dynamics, adversely devastating the overall environment. As a result, our oceans have been severely affected due to climate change and global warming. To address this issue, this study investigates the factors that cause ocean CO2 using a sample of 44 countries over 2012-2021 and explores a dynamic and causal relationship between economic growth, ocean carbon dioxide emissions, energy consumption, and control variables relating to the ocean industry. This study finds that increasing economic activity tends to increase ocean carbon emissions. The results support the evidence of the environmental Kuznets curve (EKC) hypothesis suggesting an inverted U-shaped association between ocean emissions and real income for the sample countries. Moreover, this study reports that ocean health index, maritime container transport, trade of fishery and ocean species, aquaculture production and marine species, and employment rate in the fishery processing sector are the significant factors of ocean CO2. Region-wise analyses suggest that real income positively influences ocean emissions and confirm the evidence of the EKC hypothesis in European sample countries but these relationships have an insignificant effect in Asia and the Pacific and the American regions. Furthermore, a short-run unidirectional panel causality flows from the production of aquaculture and other species to RD&D, from OHI and GDP to trade of fishery and other species, and from OHI to employment rate in the fishery sector. Likewise, bidirectional causality runs from energy consumption and maritime transport to ocean CO2 in the long term. Regarding the long-run causal association, the results determine that all of the estimated coefficients of the lagged error correction terms are statistically significant which explains that they are crucial in the adjustment process as they deviate from the long-run equilibrium.

Physiological responses and altered halocarbon production in Phaeodactylum tricornutum after exposure to polystyrene microplastics

Oceanic emissions are a major source of atmospheric, very short-lived, ozone-depleting, brominated substances. These substances can be produced by marine microalgae, estimates of their current and future emissions are imperfect, because the processes by which marine microalgae respond to environmental changes are rarely account for environmental pollutants. Here, concurrent measurements of the potential effects of polystyrene (PS) microplastics with concentrations of 25–100 mg/L on the growth of Phaeodactylum tricornutum and their volatile halocarbons (VHCs) production were made over a 20-day culture period. The maximum inhibition rates (IR) due to 0.1 µm and 0.5 µm PS microplastics on cell density were 40.11 % and 32.87 %, on Chl a content were 25.89 % and 20.73 %, and on Fv/Fm were 9.74 % and 9.00 %, respectively. All IR showed dose-dependent effects with maxima occurring in the logarithmic phase. However, in the stationary phase, P. tricornutum exposed to PS microplastics exhibited improved attributes. Enhanced biogenesis of VHCs was induced by the excess reactive oxygen species in algal cells due to microplastics exposure, and their production rates were higher in the logarithmic phase than stationary phase. This represents that oxidative stress to cells plays a dominant role in determining the release of CHBrCl2, CHBr2Cl, and CHBr3. Hence, we suggest that the widespread microplastics in the ocean may be partly responsible for the increase in the emission of VHCs by marine phytoplankton, thereby affecting the ozone layer recovery in the future.

Constraining the budget of atmospheric carbonyl sulfide using a 3-D chemical transport model

Abstract. Carbonyl sulfide (OCS) has emerged as a valuable proxy for photosynthetic uptake of carbon dioxide (CO2) and is known to be important in the formation of aerosols in the stratosphere. However, uncertainties in the global OCS budget remain large. This is mainly due to the following three flux terms: vegetation uptake, soil uptake and oceanic emissions. Bottom-up estimates do not yield a closed budget, which is thought to be due to tropical emissions of OCS that are not accounted for. Here we present a simulation of atmospheric OCS over the period 2004–2018 using the TOMCAT 3-D chemical transport model that is aimed at better constraining some terms in the OCS budget. Vegetative uptake of OCS is estimated by scaling gross primary productivity (GPP) output from the Joint UK Land Environment Simulator (JULES) using the leaf relative uptake (LRU) approach. The remaining surface budget terms are taken from available literature flux inventories and adequately scaled to bring the budget into balance. The model is compared with limb-sounding satellite observations made by the Atmospheric Chemistry Experiment – Fourier Transform Spectrometer (ACE-FTS) and surface flask measurements from 14 National Oceanic and Atmospheric Administration – Earth System Research Laboratory (NOAA-ESRL) sites worldwide. We find that calculating vegetative uptake using the LRU underestimates the surface seasonal cycle amplitude (SCA) in the Northern Hemisphere (NH) mid-latitudes and high latitudes by approximately 37 ppt (35 %). The inclusion of a large tropical source is able to balance the global budget, but further improvement to the SCA and phasing would likely require a flux inversion scheme. Compared to co-located ACE-FTS OCS profiles between 5 and 30 km, TOMCAT remains within 25 ppt (approximately 5 % of mean tropospheric concentration) of the measurements throughout the majority of this region and lies within the standard deviation of these measurements. This provides confidence in the representation of atmospheric loss and surface fluxes of OCS in the model. Atmospheric sinks account for 154 Gg S of the annual budget, which is 10 %–50 % larger than previous studies. Comparing the surface monthly anomalies from the NOAA-ESRL flask data to the model simulations shows a root-mean-square error range of 3.3–25.8 ppt. We estimate the total biosphere uptake to be 951 Gg S, which is in the range of recent inversion studies (893–1053 Gg S), but our terrestrial vegetation flux accounts for 629 Gg S of the annual budget, which is lower than other recent studies (657–756 Gg S). However, to close the budget, we compensate for this with a large annual oceanic emission term of 689 Gg S focused over the tropics, which is much larger than bottom-up estimates (285 Gg S). Hence, we agree with recent findings that missing OCS sources likely originate from the tropical region. This work shows that satellite OCS profiles offer a good constraint on atmospheric sinks of OCS through the troposphere and stratosphere and are therefore useful for helping to improve surface budget terms. This work also shows that the LRU approach is an adequate representation of the OCS vegetative uptake, but this method could be improved by various means, such as using a higher-resolution GPP product or plant-functional-type-dependent LRU. Future work will utilise TOMCAT in a formal inversion scheme to better quantify the OCS budget.

Airborne Bioaerosol Observations Imply a Strong Terrestrial Source in the Summertime Arctic

AbstractPrimary biological aerosol (PBA) is a component of coarse mode aerosol which may affect climate and health. The possible climate impacts arise from interactions between PBA and water vapor, especially since some PBA nucleate ice at warm temperatures. The health impacts span from seasonal allergies to transmission of pathogens. Despite their potential importance, the emissions, transport, and atmospheric distribution of PBA are poorly understood, especially at high latitudes where cloud effects could be pronounced. Here we report summertime measurements of fluorescent aerosol (a proxy for PBA) over the Bering and Chukchi Seas using a Wide‐Band Integrated Bioaerosol Sensor aboard a Twin Otter, alongside a lidar which detected water column productivity. Most observations occurred at 300 m over the ocean with periodic excursions to 60 and 900 m. Loadings were always low in the marine boundary layer, despite the presence of subsurface plankton layers and in contrast to other recent reports, likely indicating low oceanic emissions during our study. Large variability was observed in PBA aloft, with higher concentrations approaching those observed over the Continental US. Back trajectory analysis showed that high loadings were associated with recent transit through the continental boundary layer and we estimate PBA emissions from the Arctic tundra of up to 300 m−2 s−1 at the warmest observed temperatures. On days with strong transport from land (∼50% of our flights), PBA accounts for 12% of supermicron number and 64% of supermicron volume, indicating potentially significant effects on the albedo, glaciation and lifetime of Arctic clouds.

Seasonal and regional variations of atmospheric ammonia across the South Korean Peninsula

This study aimed to identify the factors causing NH3 emissions in the South Korean Peninsula and West Sea region. To analyze the trends of NH3 and other air pollutants, such as NOx, CO, and NR-PM1, we collected samples from six supersites across the peninsula, a roadside in Seoul, and the West Sea over different sampling periods, ranging from 1 month to 1 year. The highest NH3 concentrations were found at rural areas, ascribed to agricultural activities, particularly NH4NO3 decomposition at high summer temperatures. Areas with low population densities recorded the lowest NH3 concentrations, attributed to the lack of anthropogenic activities. A roadside field experiment confirmed the close link between ambient NH3 and vehicle emissions in urban regions by showing a strong correlation between CO and NOx concentrations and that of NH3. Moreover, we examined oceanic emissions near the eastern coast of South Korea in the West Sea. Long-range transportation studies confirmed that most of the pollutants (NH3, CO, and PM1) were transported by wind from the northeastern region of China. A maritime origin study showed that oceanic emissions and NH4NO3 decomposition in the atmosphere owing to high temperatures were the causing NH3 pollution. These findings provided valuable insights into the emission sources of NH3 in primary air pollutants in South Korea, highlighting the contributions of land-based and oceanic sources. Our study can help inform policymakers and stakeholders for developing effective regional air pollution control strategies.