Although natural atmospheric nanomaterials are ubiquitous and highly influential in environmental systems, they have only recently begun to be studied. We analyzed sub-micron and nano-scale mineral ...dust aerosols (MDAs) in wet deposition (snowfall) from two storms in Colorado, USA using single particle inductively coupled plasma mass spectrometry (spICP-MS). We found high particle number concentrations (PNCs) of MDAs (up to 10
8
particles per mL) and observed an order of magnitude difference in number concentrations related consistent with storm strength and meteorological conditions. We applied novel data processing to particle size distributions (PSDs) obtained with spICP-MS and determined that all PSDs followed the Pareto distribution despite differences in number concentration. We characterized multi-element MDA particle types with single particle ICP-time-of-flight MS (spICP-TOFMS) using particle type-specific detection limits based on crustal abundance ratios, and supplemented this approach with an unsupervised hierarchical clustering algorithm. Both methods confirmed that the median MDA composition largely followed elemental crustal abundance ratios, with a minor class of titanium-rich particles identified. We conclude that the particle size and composition of MDAs can be effectively analyzed in wet deposition by spICP-MS, but quantifying the particle number has greater uncertainty. Characterization of nano-scale MDAs can be used to better understand particle dynamics in the atmosphere, which can affect climate. Analysis of natural particle composition informs studies related to nanogeochemical cycling and can provide background particle data to further advance methods of detecting engineered nanomaterials in the environment.
Mineral dust aerosols in snow were analyzed by single particle ICP-MS with machine learning to classify particle groups.
This study analyzed long-term air concentrations and annual wet deposition of inorganic ions and aerosol and precipitation acidity at 31 Canadian sites from 1983 to 2011. Scavenging ratios of ...inorganic ions and relative contributions of particulate- and gas-phase species to NH4+, NO3−, and SO42− wet deposition were determined. Geographical patterns of atmospheric Ca2+, Na+, Cl−, NH4+, NO3−, and SO42− were similar to wet deposition and attributed to anthropogenic sources, sea-salt emissions, and agricultural emissions. Decreasing trends in atmospheric NH4+ (1994–2010) and SO42− (1983–2010) were prevalent. Atmospheric NO3− increased prior to 2001 and then declined afterwards. These results are consistent with SO2, NOx and NH3 emission trends in Canada and the USA. Widespread declines in annual NO3− and SO42− wet deposition ranged from 0.07 to 1.0 kg ha−1 a−1 (1984–2011). Acidic aerosols and precipitation impacted southern and eastern Canada more than western Canada; however, both trends have been decreasing since 1994. Scavenging ratios of particulate NH4+, SO42− and NO3− differed from literature values by 22 %, 44 %, and a factor of 6, respectively, because of the exclusion of gas scavenging in previous studies. Average gas and particle scavenging contributions to total wet deposition were estimated to be 72 % for HNO3 and 28 % for particulate NO3−, 37 % for SO2 and 63 % for particulate SO42−, and 30 % for NH3 and 70 % for particulate NH4+.
Mercury (Hg) is a global pollutant whose atmospheric deposition is a major input to the terrestrial and oceanic ecosystems. Gas‐particle partitioning (GPP) of gaseous oxidized mercury (GOM) ...redistributes speciated Hg between gas and particulate phase and can subsequently alter Hg deposition flux. Most 3‐dimensional chemical transport models either neglected the Hg GPP process or parameterized it with measurement data limited in time and space. In this study, CMAQ‐newHg‐Br (Ye et al., 2018, https://doi.org/10.1002/2017ms001161) was updated to CMAQ‐newHg‐Br v2 by implementing a new GPP scheme and the most up‐to‐date Hg redox chemistry and was run for the northeastern United States over January‐November 2010. CMAQ‐newHg‐Br v2 reproduced the measured spatiotemporal distributions of gaseous elemental mercury (GEM) and particulate bound mercury (PBM) concentrations and Hg wet deposition flux within reasonable ranges and simulated dry deposition flux in agreement with previous studies. The GPP scheme improved the simulation of PBM via increasing winter‐, spring‐ and fall‐time PBM concentrations by threefold. It also improved simulated Hg wet deposition flux with an increase of 2.1 ± 0.7 μgm2 in the 11‐month accumulated amount, offsetting half of the decreasing effect of the updated chemistry (−4.2 ± 1.8 μgm2). Further, the GPP scheme captured the observed Kp‐T relationship as reported in previous studies without using measurement data and showed advantages at night and in rural/remote areas where existing empirical parameterizations failed. Our study demonstrated CMAQ‐newHg‐Br v2 a promising assessment tool to quantify impacts of climate change and emission reduction policy on Hg cycling.
Plain Language Summary
Mercury is a toxic global pollutant and can enter the food chain through atmospheric deposition to ecosystems. Atmospheric mercury was defined operationally in the forms of gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM) and particulate bound mercury (PBM). GEM is relatively inert, but GOM and PBM are highly soluble and readily removed from the air via deposition. GEM gets oxidized to GOM and GOM can be transformed to PBM through gas particle partitioning (GPP). CMAQ‐newHg‐Br v2 was updated from its predecessor via implementing the most up‐to‐date Hg redox chemistry and a new GPP scheme. The model improved the simulation of GEM, PBM, and Hg wet deposition. Most notably the model reproduced the observed partitioning coefficient and temperature relationship (Kp‐T) and improved nighttime and less polluted PBM simulations. CMAQ‐newHg‐Br v2 can be used to assess how climate change and emission reduction policy impact environmental Hg cycling.
Key Points
CMAQ‐newHg‐Br was updated to version 2 with a new gas‐particle partitioning (GPP) scheme and the most up‐to‐date Hg redox chemistry
CMAQ‐newHg‐Br v2 better simulated gaseous elemental mercury (GEM), particulate bound mercury (PBM) and Hg wet deposition
The new GPP scheme captured the observed Kp‐T relation not using measurement data and improved nighttime and less polluted simulations
Arctic haze has a distinct seasonal cycle with peak concentrations inwinter but pristine conditions in summer. It is demonstrated that the Geophysical Fluid Dynamics Laboratory (GFDL) atmospheric ...general circulation model (AM3) can reproduce the observed seasonality of Arctic black carbon (BC), an important component of Arctic haze. The model is used to study how large-scale circulation and removal drive the seasonal cycle of Arctic BC. It is found that despite large seasonal shifts in the general circulation pattern, the transport of BC into the Arctic varies little throughout the year. The seasonal cycle of Arctic BC is attributed mostly to variations in the controlling factors of wet removal, namely the hydrophilic fraction of BC and wet deposition efficiency of hydrophilic BC. Specifically, a confluence of low hydrophilic fraction and weak wet deposition, owing to slower aging process and less efficient mixed-phase cloud scavenging, respectively, is responsible for the wintertime peak of BC. The transition to low BC in summer is the consequence of a gradual increase in the wet deposition efficiency, whereas the increase of BC in late fall can be explained by a sharp decrease in the hydrophilic fraction. The results presented here suggest that future changes in the aging and wet deposition processes can potentially alter the concentrations of Arctic aerosols and their climate effects.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The effects of unified aerosol sources on global aerosol fields simulated by different models are examined in this paper. We compare results from two AeroCom experiments, one with different (ExpA) ...and one with unified emissions, injection heights, and particle sizes at the source (ExpB). Surprisingly, harmonization of aerosol sources has only a small impact on the simulated inter-model diversity of the global aerosol burden, and consequently global optical properties, as the results are largely controlled by model-specific transport, removal, chemistry (leading to the formation of secondary aerosols) and parameterizations of aerosol microphysics (e.g., the split between deposition pathways) and to a lesser extent by the spatial and temporal distributions of the (precursor) emissions. The burdens of black carbon and especially sea salt become more coherent in ExpB only, because the large ExpA diversities for these two species were caused by a few outliers. The experiment also showed that despite prescribing emission fluxes and size distributions, ambiguities in the implementation in individual models can lead to substantial differences. These results indicate the need for a better understanding of aerosol life cycles at process level (including spatial dispersal and interaction with meteorological parameters) in order to obtain more reliable results from global aerosol simulations. This is particularly important as such model results are used to assess the consequences of specific air pollution abatement strategies.
Abstract
Long-lived basaltic volcanic eruptions are a globally important source of environmentally reactive, volatile metal pollutant elements such as selenium, cadmium and lead. The 2018 eruption of ...Kīlauea, Hawai’i produced exceptionally high discharge of metal pollutants, and was an unprecedented opportunity to track them from vent to deposition. Here we show, through geochemical sampling of the plume that volatile metal pollutants were depleted in the plume up to 100 times faster than refractory species, such as magnesium and iron. We propose that this rapid wet deposition of complexes containing reactive and potentially toxic volatile metal pollutants may disproportionately impact localised areas close to the vent. We infer that the relationship between volatility and solubility is an important control on the atmospheric behaviour of elements. We suggest that assessment of hazards from volcanic emissions should account for heterogeneous plume depletion of metal pollutants.
A detailed study on potential sources, variation, and environmental effects of the rainwater ions was carried out at Lothian Island, Sundarban mangrove forest, India, during the southwest monsoon ...(June–September) in 2019. On an event basis, the maximum rainwater precipitation was observed 17.65 mm Day
−1
and a minimum of 1.02 mm Day
−1
. The maximum amount of total precipitation was recorded in the month of July (237 mm). The volume weighted mean (VWM) concentration shows that the total ionic composition was 93.7 μeq L
−1
, whereas the percentage contribution of the total ionic concentration is found to be 45.97% to anions and 54.02% to the cations. Temporal variation was observed between early (June- July) and late monsoon (August—September), which shows a high concentration of major ions in early monsoon and low concentration in late monsoon due to the washout of atmospheric particles with the frequent and increasing precipitation. The pH values of the 78% samples show neutral pH and neutralization factors (NF) followed a sequence of NF
Ca
˃NF
Mg
˃ NF
NH4
with factors of 0.77, 0.34, and 0.14 indicating Ca
2+
was the most potential species to balance the acidic ions (NO
3
−
, SO
4
2−
) over the study area. Source apportionment study indicates the significant influence of marine actions (long-range transport by monsoonal wind from marine origin, Sea spray, salty soil profile of mangrove) as the major source of ions over Sundarban. The rate of nutrient wet deposition in the form of rainwater was estimated and average monsoonal nitrogen flux was observed 0.87 kg ha
−1
where NO
3
contributes the most (0.60 kg ha
−1
). N and P deposition flux also showed a simultaneous pattern with the seasonal nutrient concentration of surrounding river water, which may be an indication of a possible contribution of atmospheric wet deposition in the spike of monsoonal nutrient concentration in river water.
The scenarios of deposition on the sea surface around the Korean Peninsula following hypothetical release at Kori NPP were studied by application of the atmospheric transport model FLEXPART. The ...series of 1460 dispersion scenarios was calculated, covering the time period of 1 year. The total depositions on the surfaces of the East/Japan Sea (EJS), Yellow Sea (YS), East China Sea (ECS), and near-coast zone of 200-km vicinity around the Korean Peninsula, normalized on the total emission inventory were analyzed. The normalized deposition on the total area of 3 seas varied by more than 2 orders of magnitude from 0.003 to 0.59. The fraction of wet deposition in total deposition varied from 0 to 0.99. The selected most heavy deposition scenarios were divided into those dominated by dry deposition and wet deposition. The most conservative release scenarios (7 August 2020 and 2 September 2020) were dominated by wet deposition and were caused by the monsoon rainband and passage of the typhoon. In the scenario of 7 August 2020, 96% of deposition appeared in the near-coast zone. Cluster analysis of dispersion scenarios confirmed strong seasonal dependence of deposition patterns. For EJS and YS, the maximum average deposition was reached in the ‘Summer’ cluster. For ECS the maximum average normalized deposition was reached in the ‘Spring + Fall’ cluster (
D
r
=
0.055
). Minimum average deposition on all seas was obtained for the ‘Winter’ cluster.
To assess phytoplankton nutritional status in seasonally oligotrophic waters of the southern Mid‐Atlantic Bight, and the potential for rain to stimulate primary production in this region during ...summer, shipboard bioassay experiments were performed using natural seawater and phytoplankton collected north and south of the Gulf Stream. Bioassay treatments comprised iron, nitrate, iron + nitrate, iron + nitrate + phosphate, and rainwater. Phytoplankton growth was inferred from changes in chlorophyll a, inorganic nitrogen, and carbon‐13 uptake, relative to unamended control treatments. Results indicated the greatest growth stimulation by iron + nitrate + phosphate, intermediate growth stimulation by rainwater, modest growth stimulation by nitrate and iron + nitrate, and no growth stimulation by iron. Based on these data and analysis of seawater and atmospheric samples, nitrogen was the proximate limiting nutrient, with a secondary limitation imposed by phosphorus. Our results imply that summer rain events increase new production in these waters by contributing nitrogen and phosphorus, with the availability of the latter setting the upper limit on rain‐stimulated new production.
Plain Language Summary
Human activities have substantially increased the atmospheric loading and deposition of biologically available nitrogen, an essential nutrient, to the surface ocean. Such atmospheric inputs to the ocean will likely impact on oceanic primary production by phytoplankton, and thus the marine ecosystem and ocean carbon cycling, although the scale and spatial distribution of such impacts are not well known. In this study, we used shipboard experiments, observations, and laboratory measurements to assess the potential impacts of atmospheric nitrogen deposition in rainfall on oceanic waters of the Mid‐Atlantic Bight, off the U.S. eastern seaboard, during the summer. We find that the growth of phytoplankton in these waters is limited by the availability of nitrogen during summer, such that nitrogen added to the ocean by summer rain events can considerably stimulate phytoplankton primary production. However, the biological impact of these rainwater nitrogen inputs appears to be limited by the availability of another essential nutrient, phosphorus, which is present at relatively low concentrations in rainwater. This is the first study to directly examine the nutritional status of phytoplankton in relation to the impacts of rainwater nitrogen addition on primary production in oceanic waters off the U.S. East Coast.
Key Points
Nitrogen is the proximate limiting nutrient for phytoplankton growth in seasonally oligotrophic waters of the southern Mid‐Atlantic Bight during summer
Phosphorus availability exerts a secondary limitation on phytoplankton growth during summer, which may limit the impact of wet deposition on primary production
Contrary to previous findings, our results provide no evidence that availability of dissolved iron limits phytoplankton growth in this ocean region during summer
Atmospheric N deposition patterns play an important role in the nitrogen cycles of arid ecosystems. This study observed a significant spatiotemporal variation in inorganic N concentrations in ...precipitation from 2013 to 2016 at eight sampling sites in the Hexi Corridor, northwestern China. Mean mNO3–/Cl− and mNH4+/NO3− values were 1.62 and 0.98 from late autumn to early spring, respectively, indicating that inorganic N in precipitation is most likely principally controlled by NO3− in response to coal-fired heating and low wind speeds. However, mean mNO3–/Cl− and mNH4+/NO3− were 0.91 and 2.69 from late spring to early autumn, respectively, suggesting that the primary contributor is NH3 from agricultural soils and fertilizers. Mean annual mNH4+/NO3− values in the eastern sectors of the Hexi Corridor ranged from 0.57 to 1.55, but those in the central and western sectors ranged from 1.53 to 3.59. The ratios of NH4+-N deposition flux to total wet deposition of inorganic N flux were >50% in the Corridor's central and western sectors, but <36% in its eastern sectors. These results reflect the differences in wet N deposition patterns between the western and eastern sectors of the Hexi Corridor. The spatiotemporal variations in NO2 concentrations appear consistent with those of NO3− in precipitation, indicating that atmospheric NO2 is a main driver of the spatiotemporal changes in the NH4+-N and NO3−-N components found in precipitation. This study summarized previously published data to describe a spatial distribution pattern of inorganic N in precipitation in the Hexi Corridor. It provides data support for the formulation of environmental policies and agricultural N management in arid regions.
•NH4+-N and NO3−-N were the major components of wet inorganic N deposition in the western and eastern of the Hexi Corridor.•The seasonal transition was obvious in inorganic N source in precipitation.•Spatial pattern of inorganic nitrogen in precipitation in Hexi Corridor was described.
PDF
