The contributions to aerosols and major chemical compositions (e.g. water-soluble ions-WSIs) from residential coal combustion (RCC) are still now existing large uncertainty in air quality modeling. ...The lake of reliable emission inventories for primary WSIs from RCC in China with measured emission factors (EFs) adopted is a major obstacle. With simulating burning test and dilution sampling method, this study detected the emission factors of nine size-segregated aerosols (0.43–10 μm) and associated WSIs emission factors from residential honeycomb briquettes and chunk coal burning, considering smoldering and flaming combustion status. Then a 1 km × 1 km grid cell-based emission inventory of RCC, including size-segregated particles and associated WSIs in China was established. The contributions of RCC to ambient fine particles were estimated by GEOS-Chem model. Results indicated that compared with anthracite coal combustion emission, bituminous coal burning emission can reduce the EFs of particles, while may increase the EFs of WSIs. The averaged EF of WSIs from honeycomb coal combustion was found 1.15 times higher than those for chunk coal burning. The total emission amounts of NH4+, Na+, K+, Mg2+, Ca2+, Cl−, NO3− and SO42− in PM2.1 from residential coal combustion in 2015 were 1915.3, 101.8, 1180.8, 50.1, 96.8, 4956.1, 552.4 and 7430.3 t, respectively, totally accounting for 2.03% of PM2.1. SO42− was the most important WSIs in fine particles released from RCC, occupied by 45.6% of the total WSIs. GEOS-Chem simulation indicated that RCC emission in China averagely accounted for 25.7% of ambient PM2.5 and 7.1% for sulfate. Our results show that RCC emission is an important source for primary PM2.5 and sulfate, suggesting the primary emission of WSI should be included in air quality modeling. More EFs monitoring of RCC of different types and regions in China should be conducted, for updating emission inventory and optimizing modeling results.
Display omitted
•Emission factors of water-soluble ions from domestic coal burning were obtained.•Honeycomb coal flaming and smoldering burning condition were considered.•Emission inventory for ions in PM1.1 and PM2.1 from domestic coal burning were established.•Contributions of PM2.5 and ions from domestic coal burning were simulated by GEOS-Chem model.
Vertical distribution of black carbon (BC) determines the layer where its heating impacts exert. This study presents continuous and simultaneous measurements at surface and on a mountain site above ...the wintertime planetary boundary layer influenced by uplifted surface anthropogenic emissions. BC was observed efficiently transported upwards by daytime convective mixing. However, this vertical transport was less for other particulate masses. An about twofold higher BC mass fraction was thus present at mountain than surface, hereby a lowered single‐scattering albedo (SSA) by 0.06. This may be caused by the evaporative loss of condensed semivolatile materials, prevailing the secondary particulate formation, in a cleaner environment containing less precursors. The elevated BC mass corresponded with the most intensive solar radiation at midday, wielding more heating impacts over the planetary boundary layer (PBL). This phenomenon may apply to other remote regions where a reduced SSA will introduce more positive radiative effects.
Plain Language Summary
Black carbon is strongly light absorbing, and its heating impacts in disturbing the stability of atmosphere depend on its location in the atmospheric column; thus, to understand its vertical distribution and transport mechanism is important. This study conducted simultaneous measurements at both sites on the surface and an elevated mountain site influenced by surface sources. We found that BC can be efficiently and vertically transported to the mountain site but not for the other more volatile substances. This is because a less secondary formation (due to lack of gas precursor) and some repartition process on the particle (back to the gas phase) may have led to a higher BC mass fraction in cleaner environment. This means in some remote places with less gas precursor present, BC may still reach and result in a high mass fraction, leading to more positive radiative effect.
Key Points
Simultaneous measurements at both surface and top of boundary layer were performed for 1 month
BC was transported efficiently to the top of PBL however not for other more volatile aerosols
Higher BC mass fraction was observed over the top of boundary layer with lowered single‐scattering albedo by 0.06
Aerosol particles are of importance in the Earth's radiation budget since
they scatter and absorb sunlight. While extensive studies of aerosol optical
properties have been conducted at ground sites, ...vertical measurements and
characterization are very limited in megacities. In this work, we present
simultaneous real-time online measurements of aerosol optical properties at
ground level and at 260 m on a meteorological tower from 16 November to
13 December in 2016 in Beijing along with measurements of continuous vertical
profiles during two haze episodes. The average (±1σ) scattering
and absorption coefficients (bsca and babs; λ=630 nm) were 337.6 (±356.0) and 36.6 (±33.9) Mm−1 at
260 m, which were 26.5 % and 22.5 % lower than those at ground
level. Single scattering albedo (SSA), however, was comparable between the
two heights, with slightly higher values at ground level (0.89±0.04).
Although bsca and babs showed overall similar
temporal variations between ground level and 260 m, the ratios of 260 m to ground
varied substantially from less than 0.4 during the clean stages of haze
episodes to > 0.8 in the late afternoon. A more detailed
analysis indicates that vertical profiles of bsca,
babs, and SSA in the low atmosphere were closely related to the
changes in meteorological conditions and mixing layer height. The mass
absorption cross section (MAC) of equivalent black carbon (eBC, λ=630 nm) varied substantially from 9.5 to 13.2 m2 g−1
in winter in Beijing, and it was strongly associated with the mass ratio of
coating materials on refractory BC (rBC) to rBC (MR), and also the
oxidation degree of organics in rBC-containing particles. Our results show
that the increases in MAC of eBC in winter were mainly caused by
photochemically produced secondary materials. Light absorption of organic
carbon (brown carbon, BrC) was also important in winter, which on average
accounted for 46 (±8.5) % and 48 (±9.3) % of the total
absorption at 370 nm at ground level and 260 m, respectively. A linear
regression model combined with positive matrix factorization analysis was
used to show that coal combustion was the dominant source contribution of BrC
(48 %–55 %) followed by biomass burning (17 %) and
photochemically processed secondary organic aerosol (∼20 %) in
winter in Beijing.
Commercial shipping is considered as an important source of air pollution and cloud condensation nuclei (CCN). To assess the climatic and environmental impacts of shipping, detailed characterization ...of ship plumes near the point of emission and understanding of ship plume evolution further downwind are essential. This airborne measurement study presents the online characterization of particulate phase ship emissions in the region of Western Europe in 2019 prior to new international sulfur emission controls becoming enacted. More than 30 ships from both the sulfur emission control area (SECA) in the English Channel and the open sea (OS) are measured and compared. Ships within the SECA emitted much less sulfate (SO4) compared with those at OS. When shifted to a lower apparent fuel sulfur content (FSC) at similar engine loads, the peak of the fresh ship emitting the particle number size distribution shifted from around 60–80 nm in diameter to below 40 nm in diameter. The emission factors (EFs) of sulfate are predicted to decrease by around 94% after the 2020 regulation on ship sulfur emission in the open ocean. The EFs of refractory black carbon (rBC) and organic compounds (Org) do not appear to be directly affected by the lower sulfur contents. The total number concentration for condensation nuclei (CN) >2.5 nm and >0.1 μm are predicated to be reduced by 69 and 56%, respectively. Measured plume evolution results indicate that the S(IV) to S(VI) conversion rate was around 23.4% per hour at the beginning of plume evolution, and the CCN and CN >2.5 nm ratio increased with plume age primarily due to condensation and coagulation. We estimate that the new sulfur emission regulation will lead to a reduction of more than 80% in CCN from fresh ship emissions. The ship-emitted EFs results presented here will also inform emission inventories, policymaking, climate, and human health studies.
The role of organic aerosols (OA) as ice nucleating particles (INPs) deserves attention because of their high atmospheric abundance. The low concentration of INPs poses challenges in identifying the ...ice nucleation (IN) of OA among a mix of aerosol types in ambient environment. This study coupled a catalytic stripper system (350°C heating) with a continuous flow diffusion chamber to online investigate the immersion INPs of ambient particles at −30°C at a suburban site. Significant reduction (71 ± 25%) of INP concentrations after evaporation suggested that INPs can be significantly contributed by volatile OA. In addition, nonvolatile OA were more efficient INPs than black carbon. Oxygenated OA by photooxidation and lower ambient promoted the IN activity at noon, when the OA may be more viscous. These results hereby present the first field evidence that OA in anthropogenically influenced regions can be efficient INPs well above the homogeneous IN temperature.
Plain Language Summary
Ice nucleating particles have an important impact on weather and climate by modulating cloud microphysics. Globally, measurements have demonstrated the ubiquitous presence of ice nucleating particles (INPs); however, the contribution of abundant organic aerosols (OA) to INPs remains uncertain owing to their complex compositions and varying phase states. In this study, using concurrent measurements between ambient and heated INPs, we prove the important contribution of volatile OA at 350°C to immersion freezing INPs at −30°C, especially at noon, when OA are more solid‐like because of their oxygenation by photooxidation and lower ambient relative humidity. In addition, nonvolatile OA were found to be a more efficient INPs than black carbon. Therefore, our results provide field evidence that OA in anthropogenically influenced regions could serve as an important atmospheric INPs at 8°C above the homogeneous freezing temperature.
Key Points
Field measurements prove contribution of organic aerosols (OA) in anthropogenically influence region to immersion mode ice nucleation (IN)
OA oxygenated by photooxidation and lower relative humidity showed a correlation with increased at noon
Nonvolatile OA at 350°C heating have a higher IN efficiency than that of black carbon
We propose an opportunistic user association for multi-service HetNets aiming to guarantee quality of service (QoS) of human-to-human (H2H) traffic while providing fair resource allocation for ...machine-to-machine (M2M) traffic. We classify H2H traffic as primary service and M2M traffic as secondary service. The opportunistic user association is formulated as an optimization problem, which can be resolved by Nash Bargaining Solution (NBS). Simulation results show that the proposed algorithm can enable network operators to support fair resource allocation for M2M traffic without jeopardizing QoS of H2H traffic.
Cyperus esculentus is unique in that it can accumulate significant amounts of oil, starch and sugar as major storage reserves in tubers with high tuber yield and therefore considered as a novel model ...to study carbon allocation into different storage reserves in underground sink tissues such as tubers and roots. Sucrose (Suc) plays a central role in control of carbon flux toward biosynthesis of different storage reserves; however, it remains unclear for the molecular mechanism underlying Suc metabolism in underground oil-rich storage tissues. In the present study, a comprehensive transcriptome analysis of C. esculentus oil tuber compared to other plant oil- or carbohydrate-rich storage tissues was made for the expression patterns of genes related to the Suc metabolism.
The results revealed some species-specific features of gene transcripts in oil tuber of C. esculentus, indicating that: (i) the expressions of genes responsible for Suc metabolism are developmentally regulated and displayed a pattern dissimilar to other plant storage tissues; (ii) both of Suc breakdown and biosynthesis processes might be the major pathways associated with Suc metabolism; (iii) it was probably that Suc degradation could be primarily through the action of Suc synthase (SUS) other than invertase (INV) during tuber development. The orthologs of SUS1, SUS3 and SUS4 are the main SUS isoforms catalyzing Suc breakdown while the vacuolar INV (VIN) is the leading determinant controlling sugar composition; (iv) cytosolic hexose phosphorylation possibly relies more on fructose as substrate and uridine diphosphate glucose pyrophosphorylase (UGP) plays an important role in this pathway; (v) it is Suc-phosphate synthase (SPS) B- and C-family members rather than SPS A that are the principal contributors to SPS enzymes and play crucial roles in Suc biosynthesis pathway.
We have successfully identified the Suc metabolic pathways in C. esculentus tubers, highlighting several conserved and distinct expressions that might contribute to sugar accumulation in this unique underground storage tissue. The specific and differential expression genes revealed in this study might indicate the special molecular mechanism and transcriptional regulation of Suc metabolism occurred in oil tubers of C. esculentus.
Mineral dust is an important component of the climate system, affecting the
radiation balance, cloud properties, biogeochemical cycles, regional
circulation and precipitation, as well as having ...negative effects on
aviation, solar energy generation and human health. Dust size and composition
has an impact on all these processes. However, changes in dust size
distribution and composition during transport, particularly for coarse
particles, are poorly understood and poorly represented in climate models.
Here we present new in situ airborne observations of dust in the Saharan Air
Layer (SAL) and the marine boundary layer (MBL) at the beginning of its
transatlantic transport pathway, from the AERosol
Properties – Dust (AER-D) fieldwork in August 2015,
within the peak season of North African dust export. This study focuses on
coarse-mode dust properties, including size distribution, mass loading,
shape, composition, refractive indices and optical properties. Size
distributions from 0.1 to 100 µm diameter (d) are presented, fully
incorporating the coarse and giant modes of dust. Within the MBL, mean
effective diameter (deff) and volume median diameter (VMD) were 4.6 and 6.0 µm respectively, giant particles with a mode at
20–30 µm were observed, and composition was dominated by quartz and
alumino-silicates at d > 1 µm. Within the SAL, particles
larger than 20 µm diameter were always present up to 5 km altitude, in
concentrations over 10−5 cm−3, constituting up to 40 % of
total dust mass. Mean deff and VMD were 4.0 and 5.5 µm
respectively. Larger particles were detected in the SAL than can be explained
by sedimentation theory alone. Coarse-mode composition was dominated by
quartz and alumino-silicates; the accumulation mode showed a strong
contribution from sulfate-rich and sea salt particles. In the SAL, measured
single scattering albedos (SSAs) at 550 nm representing d < 2.5 µm were
0.93 to 0.98 (mean 0.97). Optical properties calculated for the full
size distribution (0.1 < d < 100 µm) resulted in lower
SSAs of 0.91–0.98 (mean 0.95) and mass extinction coefficients of 0.27–0.35 m2 g−1 (mean 0.32 m2 g−1). Variability in SSA was mainly
controlled by variability in dust composition (principally iron) rather than
by variations in the size distribution, in contrast with previous observations
over the Sahara where size is the dominant influence. It is important that
models are able to capture the variability and evolution of both dust
composition and size distribution with transport in order to accurately
represent the impacts of dust on climate. These results provide a new SAL
dust dataset, fully representing coarse and giant particles, to aid model
validation and development.
The transport processes and fate of 137Cs in eastern Chinese seas (ECSs) that consists of the Bohai, Yellow, and East China Seas, have not been well established. In this study, we measured the ...concentrations of 137Cs in the ECSs water and surface sediments during 2013–2014. Combined with a number of published 137Cs inventory data from drainage basins and sediment accumulation rates in the ECSs, the distribution, sources and budgets of 137Cs in the ECSs were investigated. The 137Cs activity in the water column and surface sediments ranged from 0.03 to 1.92 Bq/m3 and from 0.30 to 5.22 Bq/kg, respectively. No 134Cs signal was observed, suggesting that the Fukushima accident had limited impact on the ECSs during the investigation period. Mass balance of 137Cs suggests that at least 7.4 × 1012 Bq/y of 137Cs imported into the ECSs from the Northwestern Pacific that accounts for 0.7% of the 137Cs transported by the Kuroshio Current, and this value is 5.2 times higher than the sum of atmospheric fallout and total riverine input. The apparent half-lives of 137Cs are estimated to be 15.1 y for the ECS and 7.7 y for the YS. The vertical profiles in the continental shelf edge and the Yangtze River Estuary reveal that the upwelling of the Kuroshio Subsurface Water is the main mechanism of 137Cs import into the ECSs. The high level of 137Cs in oceanic water masses and the low level of 137Cs in riverine and coastal waters make 137Cs a good indicator for tracing water mass movement and interaction. In addition, good correlation between 137Cs activity and mean grain size (φ) indicates that 137Cs can serve as an effective tracer to track dispersal pathways of fine sediments in river-dominated marginal seas.
Display omitted
•The spatial distribution of 137Cs in surface sediments and seawater was investigated.•Oceanic inputs dominate the source of 137Cs in eastern Chinese seas.•The apparent half-lives of 137Cs are 7.7–15.1 y in eastern Chinese seas.•137Cs is useful to track fine sediment transport in river-dominated marginal seas.•137Cs is useful to trace water mass movement and exchange in marginal seas.
Abstract
The less improvement of ambient visibility suspects the government’s efforts on alleviating PM
2.5
pollution. The COVID-19 lockdown reduced PM
2.5
and increased visibility in Wuhan. Compared ...to pre-lockdown period, the PM
2.5
concentration decreased by 39.0 μg m
−3
, dominated by NH
4
NO
3
mass reduction (24.8 μg m
−3
) during lockdown period. The PM
2.5
threshold corresponding to visibility of 10 km (PTV
10
) varied in 54–175 μg m
−3
and an hourly PM
2.5
of 54 μg m
−3
was recommended to prevent haze occurrence. The lockdown measures elevated PTV
10
by 9–58 μg m
−3
as the decreases in PM
2.5
mass scattering efficiency and optical hygroscopicity. The visibility increased by 107%, resulted from NH
4
NO
3
extinction reduction. The NH
4
NO
3
mass reduction weakened its mutual promotion with aerosol water and increased PM
2.5
deliquescence humidity. Controlling TNO
3
(HNO
3
+ NO
3
−
) was more effective to reduce PM
2.5
and improve visibility than NH
x
(NH
3
+ NH
4
+
) unless the NH
x
reduction exceeded 11.7–17.5 μg m
−3
.
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