scholarly journals Profiling Dust Mass Concentration in Northwest China Using a Joint Lidar and Sun-photometer Setting

2021 ◽  
Vol 13 (6) ◽  
pp. 1099
Author(s):  
Tianhe Wang ◽  
Ying Han ◽  
Wenli Hua ◽  
Jingyi Tang ◽  
Jianping Huang ◽  
...  
Keyword(s):  
Mass Concentration ◽  
Field Experiments ◽  
Negative Relationship ◽  
Northwest China ◽  
Dust Particles ◽  
Mass Loading ◽  
Average Mass ◽  
Dust Mass ◽  
Dust Loading ◽  
Sun Photometer

The satellite-based estimation of the dust mass concentration (DMC) is essential for accurately evaluating the global biogeochemical cycle of the dust aerosols. As for the uncertainties in estimating DMC caused by mixing dust and pollutants and assuming a fixed value for the mass extinction efficiency (MEE), a classic lidar-photometer method is employed to identify and separate the dust from pollutants, obtain the dust MEE, and evaluate the effect of the above uncertainties, during five dust field experiments in Northwest China. Our results show that this method is effective for continental aerosol mixtures consisting of dust and pollutants. It is also seen that the dust loading mainly occurred in the free troposphere (< 6 km), with the average mass loading of 905 ± 635 µg m−2 trapped in the planetary boundary layer. The dust MEE ranges from 0.30 to 0.60 m2 g−1 and has a significantly negative relationship with the size of dust particles. With the assumption of the dust MEE of 0.37 (0.60) m2 g−1, the DMC is shown to be overestimated (underestimated) by 20–40% (15–30%). In other words, our results suggest that the change of MEE with the size of dust particles should be considered in the estimation of DMC.

scholarly journals Measurement of scattering and absorption properties of dust aerosol in a Gobi farmland region of northwest China — a potential anthropogenic influence

2017 ◽  
Author(s):  
Jianrong Bi ◽  
Jianping Huang ◽  
Jinsen Shi ◽  
Zhiyuan Hu ◽  
Tian Zhou ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Source Region ◽  
Inversion Layer ◽  
Vertical Mixing ◽  
Northwest China ◽  
Single Scattering ◽  
Dust Aerosol ◽  
Dust Particles ◽  
Valley Wind ◽  
Average Mass

Abstract. We conducted a comprehensive field campaign on exploring the optical characteristics of mineral dust in Dunhuang farmland nearby the Gobi deserts of northwest China during spring of 2012. The day-to-day and diurnal variations of dust aerosol showed prominent features throughout the experiment, primarily attributable to frequent dust events and local anthropogenic emissions. The overall average mass concentration of the particulate matter with an aerodynamic diameter less than 10 μm (PM10), light scattering coefficient (σsp,670), absorption coefficient (σap,670), and single-scattering albedo (SSA670) were 113±169 μgm-3, 53.3 ± 74.8 Mm-1,  3.2± 2.4 Mm-1, and 0.913 ± 0.05, which were comparable to the background levels in southern United States, but smaller than that in the eastern and other northwestern China. The anthropogenic dust produced by agricultural cultivations (e.g., land planning, plowing, and disking) exerted a significant superimposed effect on high dust concentrations in Dunhuang farmland prior to the growing season (i.e., from 1 April to 10 May). Strong south valley wind and vertical mixing in daytime scavenged the pollution and weak northeast mountain wind and stable inversion layer at night favorably accumulated the air pollutants near the surface. In the afternoon (13:00–18:00 LT), mean SSA670 was 0.945 ± 0.04 that was predominant by dust particles, whereas finer particles and lower SSA670 values (~ 0.90–0.92) were measured at night, suggesting the potential influence by the mixed dust-pollutants. During a typical biomass burning event on 4 April 2012, σap,670 changed from ~ 2.0 Mm-1 to 4.75 Mm-1 and SSA670 changed from ~ 0.90 to ~ 0.83, implying remarkable modification of aerosol absorptive properties induced by human activities. The findings of this study would help to advance an in-depth understanding of the interaction among dust aerosol, atmospheric chemistry, and climate change in desert source region.

scholarly journals Measurement of scattering and absorption properties of dust aerosol in a Gobi farmland region of northwestern China – a potential anthropogenic influence

2017 ◽  
Vol 17 (12) ◽  
pp. 7775-7792 ◽  
Author(s):  
Jianrong Bi ◽  
Jianping Huang ◽  
Jinsen Shi ◽  
Zhiyuan Hu ◽  
Tian Zhou ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Source Region ◽  
Inversion Layer ◽  
Vertical Mixing ◽  
Northwest China ◽  
Dust Aerosol ◽  
Dust Particles ◽  
Gobi Desert ◽  
Valley Wind ◽  
Average Mass

Abstract. We conducted a comprehensive field campaign to explore the optical characteristics of mineral dust in Dunhuang farmland near the Gobi Desert of northwest China during spring of 2012. The day-to-day and diurnal variations of dust aerosol showed prominent features throughout the experiment, primarily attributable to frequent dust events and local anthropogenic emissions. The overall average mass concentrations of the particulate matter with an aerodynamic diameter less than 10 µm (PM10), light scattering coefficient (σsp, 670), absorption coefficient (σap, 670), and single-scattering albedo (SSA670) were 113 ± 169 µg m−3, 53.3 ± 74.8 Mm−1, 3.2 ± 2.4 Mm−1, and 0.913 ± 0.05, respectively, which were comparable to the background levels in the southern United States but smaller than those in the eastern and other northwestern Chinese cities. The anthropogenic dust produced by agricultural cultivations (e.g., land planning, plowing, and disking) exerted a significant superimposed effect on high dust concentrations in Dunhuang farmland prior to the growing season (i.e., from 1 April to 10 May). Strong south valley wind and vertical mixing in daytime scavenged the pollution, and the weak northeast mountain wind and stable inversion layer at night favorably accumulated the air pollutants near the surface. In the afternoon (13:00–18:00 LT, local time), mean SSA670 was 0.945 ± 0.04 predominantly from dust particles, whereas finer particles and lower SSA670 values ( ∼  0.90–0.92) were measured at night, suggesting the potential influence by the mixed dust pollutants. During a typical biomass burning event on 4 April 2012, σap, 670 increased from  ∼  2.0 to 4.75 Mm−1 and SSA670 changed from  ∼  0.90 to  ∼  0.83, implying remarkable modification of aerosol absorptive properties induced by human activities. The findings of this study would help to advance an in-depth understanding of the interaction among dust aerosol, atmospheric chemistry, and climate change in a desert source region.

Shock Wave Propagation Into a Dust-Gas Suspension Inside a Double-Bend Conduit

2002 ◽  
Vol 124 (2) ◽  
pp. 483-491 ◽  
Author(s):  
O. Igra ◽  
X. Wu ◽  
G. Q. Hu ◽  
J. Falcovitz
Keyword(s):  
Shock Wave ◽  
Wave Attenuation ◽  
Numerical Study ◽  
Effective Means ◽  
Solid Particles ◽  
Dust Particles ◽  
Mass Loading ◽  
Shock Attenuation ◽  
Dust Mass ◽  
Transmitted Shock Wave

Using conduits in which a transmitted shock wave experiences abrupt changes in its direction of propagation is an effective means for shock wave attenuation. An additional attenuation of the transmitted shock wave is obtained when the medium contained inside the conduit (through which the shock wave is transmitted) is a suspension rather than a pure gas. The present numerical study shows that adding small solid particles (dust) into the gaseous phase results in sharp attenuation of all shock waves passing through the conduit. It is shown that the smaller the dust particles diameter is, the higher the shock attenuation becomes. Increasing the dust mass loading in the suspension also causes a quick attenuation. By proper choice of dust mass loading in the suspension, or the particles diameter, it is possible to ensure that the emerging wave from the conduit exit channel is a (smooth) compression wave, rather than a shock wave.

scholarly journals Quantitative Detection of Dust Storms with the Millimeter Wave Radar in the Taklimakan Desert

Atmosphere ◽  
2019 ◽  
Vol 10 (9) ◽  
pp. 511 ◽  
Author(s):  
Ming ◽  
Wei ◽  
Wang
Keyword(s):  
Dust Storm ◽  
Mass Concentration ◽  
Dust Storms ◽  
Taklimakan Desert ◽  
Effective Height ◽  
Average Mass ◽  
Wave Radar ◽  
Dust Mass ◽  
Spectrum Distribution ◽  
Reflectivity Factor

In order to conduct real-time quantitative monitoring of dust storms, Ka-band millimeter wave radar (MMWR) was utilized for the consecutive detection of dust storms over the Taklimakan Desert from April to June 2018. The retrievals of the reflectivity factor, dust spectrum distribution and dust mass concentration were carried out with the power spectrum data detected by MMWR for three dust storm processes. The analysis shows that: The probability density distribution of dust conforms to the lognormal distribution. During the dust storm processes, the effective detection height of the reflectivity factor was within 2000 m and the range of the reflectivity factors was between-25 dBZ and 25 dBZ. During the floating dust period, the effective height of the dust spectrum distribution was lower than 300 m and the values of dust mass concentration were less than 31.62 μg·m-3,at a height of 200 m. Furthermore, during the blowing sand stage, the effective height of the dust spectrum distribution was normally lower than 600 m and the values of dust mass concentration were mainly less than 316.23 μg·m-3,at a height of 200 m. During the dust storm period, the effective height of the dust spectrum distributionexceeded1000 m; when the height was 100 m, the values of dust mass concentration were between 1220 μg∙m-3 and 42,146 μg∙m-3 and the average mass concentration was 9287 μg·m-3; whereas, the values of dust mass concentration were between 2 μg∙m-3 and 820 μg∙m-3 when the height was 1200m and the average mass concentration was 24 μg∙m-3. The relationship between the reflectivity factor Z and the dust mass concentration M isdefined as Z=651.6M0.796. Compared with the observational data from Grimm180 particle detector, the data of the retrieved dust mass concentration are basically accurate and this retrieved method proves to be feasible. Thus, the MMWR cans be used as a new device for quantitative monitoring of dust storms.

scholarly journals Uncertainty in modeling dust mass balance and radiative forcing from size parameterization

2013 ◽  
Vol 13 (7) ◽  
pp. 19649-19700 ◽  
Author(s):  
C. Zhao ◽  
S. Chen ◽  
L. R. Leung ◽  
Y. Qian ◽  
J. Kok ◽  
...  
Keyword(s):  
Mass Balance ◽  
Radiative Forcing ◽  
Dust Emission ◽  
Dust Particles ◽  
Mass Loading ◽  
Dust Source ◽  
Deposition Fluxes ◽  
Source Regions ◽  
Dust Mass ◽  
The Difference

Abstract. This study examines the uncertainties in simulating mass balance and radiative forcing of mineral dust due to biases in the dust size parameterization. Simulations are conducted quasi-globally (180° W–180° E and 60° S–70° N) using the WRF-Chem model with three different approaches to represent dust size distribution (8-bin, 4-bin, and 3-mode). The biases in the 3-mode or 4-bin approaches against a relatively more accurate 8-bin approach in simulating dust mass balance and radiative forcing are identified. Compared to the 8-bin approach, the 4-bin approach simulates similar but coarser size distributions of dust particles in the atmosphere, while the 3-mode approach retains more fine dust particles but fewer coarse dust particles due to its prescribed σg of each mode. Although the 3-mode approach yields up to 10 days longer dust mass lifetime over the remote oceanic regions than the 8-bin approach, the three size approaches produce similar dust mass lifetime (3.2 days to 3.5 days) on quasi-global average, reflecting that the global dust mass lifetime is mainly determined by the dust mass lifetime near the dust source regions. With the same global dust emission (∼6000 Tg yr-1), the 8-bin approach produces a dust mass loading of 39 Tg, while the 4-bin and 3-mode approaches produce 3% (40.2 Tg) and 25% (49.1 Tg) higher dust mass loading, respectively. The difference in dust mass loading between the 8-bin approach and the 4-bin or 3-mode approaches has large spatial variations, with generally smaller relative difference (<10%) near the surface over the dust source regions. The three size approaches also result in significantly different dry and wet deposition fluxes and number concentrations of dust. The difference in dust aerosol optical depth (AOD) (a factor of 3) among the three size approaches is much larger than their difference (25%) in dust mass loading. Compared to the 8-bin approach, the 4-bin approach yields stronger dust absorptivity, while the 3-mode approach yields weaker dust absorptivity. Overall, on quasi-global average, the three size parameterizations result in a significant difference of a factor of 2∼3 in dust surface cooling (-1.02∼-2.87 W m-2) and atmospheric warming (0.39∼0.96 W m-2) and in a tremendous difference of a factor of ∼10 in dust TOA cooling (-0.24∼-2.20 W m-2). An uncertainty of a factor of 2 is quantified in dust emission estimation due to the different size parameterizations. This study also highlights the uncertainties in modeling dust mass and number loading, deposition fluxes, and radiative forcing resulting from different size parameterizations, and motivates further investigation of the impact of size parameterizations on modeling dust impacts on air quality, climate, and ecosystem.

scholarly journals Uncertainty in modeling dust mass balance and radiative forcing from size parameterization

2013 ◽  
Vol 13 (21) ◽  
pp. 10733-10753 ◽  
Author(s):  
C. Zhao ◽  
S. Chen ◽  
L. R. Leung ◽  
Y. Qian ◽  
J. F. Kok ◽  
...  
Keyword(s):  
Mass Balance ◽  
Radiative Forcing ◽  
Dust Emission ◽  
Dust Particles ◽  
Mass Loading ◽  
Dust Source ◽  
Source Regions ◽  
Dust Mass ◽  
The Difference ◽  
The Impact

Abstract. This study examines the uncertainties in simulating mass balance and radiative forcing of mineral dust due to biases in the dust size parameterization. Simulations are conducted quasi-globally (180° W–180° E and 60° S–70° N) using the WRF-Chem model with three different approaches to represent dust size distribution (8-bin, 4-bin, and 3-mode). The biases in the 3-mode or 4-bin approaches against a relatively more accurate 8-bin approach in simulating dust mass balance and radiative forcing are identified. Compared to the 8-bin approach, the 4-bin approach simulates similar but coarser size distributions of dust particles in the atmosphere, while the 3-mode approach retains more fine dust particles but fewer coarse dust particles due to its prescribed σg of each mode. Although the 3-mode approach yields up to 10 days of longer dust mass lifetime over the remote oceanic regions than the 8-bin approach, the three size approaches produce a similar dust mass lifetime (3.2 days to 3.5 days) on quasi-global average, reflecting that the global dust mass lifetime is mainly determined by the dust mass lifetime near the dust source regions. With the same global dust emission (~4600 Tg yr−1), the 8-bin approach produces a dust mass loading of 39 Tg, while the 4-bin and 3-mode approaches produce 3% (40.2 Tg) and 25% (49.1 Tg) higher dust mass loading, respectively. The difference in dust mass loading between the 8-bin approach and the 4-bin or 3-mode approaches has large spatial variations, with generally smaller relative difference (<10%) near the surface over the dust source regions. The three size approaches also result in significantly different dry and wet deposition fluxes and number concentrations of dust. The difference in dust aerosol optical depth (AOD) (a factor of 3) among the three size approaches is much larger than their difference (25%) in dust mass loading. Compared to the 8-bin approach, the 4-bin approach yields stronger dust absorptivity, while the 3-mode approach yields weaker dust absorptivity. Overall, on quasi-global average, the three size parameterizations result in a significant difference of a factor of 2~3 in dust surface cooling (−1.02~−2.87 W m−2) and atmospheric warming (0.39~0.96 W m−2) and in a tremendous difference of a factor of ~10 in dust TOA (top of atmosphere) cooling (−0.24~−2.20 W m−2). The impact of different size representations on dust radiative forcing efficiency is smaller. An uncertainty of a factor of 2 is quantified in dust emission estimation due to the different size parameterizations. This study also highlights the uncertainties in modeling dust mass and number loading, deposition fluxes, and radiative forcing resulting from different size parameterizations, and motivates further investigation of the impact of size parameterizations on modeling dust impacts on air quality, climate, and ecosystems.

Factors affecting the yield of winter cereals in crop margins

2000 ◽  
Vol 135 (4) ◽  
pp. 335-346 ◽  
Author(s):  
A. WILCOX ◽  
N. H. PERRY ◽  
N. D. BOATMAN ◽  
K. CHANEY
Keyword(s):  
Soil Compaction ◽  
Dry Matter ◽  
Field Experiments ◽  
Polynomial Regression ◽  
Negative Relationship ◽  
Fertilizer Application ◽  
Winter Cereal ◽  
Edge Field ◽  
Winter Cereals ◽  
Non Linear

Yields of arable crops are commonly lower on the crop margins or headlands, but the nature of the relationship between yield and distance from the crop edge has not been clearly defined, nor have the reasons for lower marginal yields. Surveys of 40 winter wheat headlands were carried out in 2 years to determine how yield changed with distance, and what factors might influence this relationship. Two field experiments were also conducted over 3 years in winter cereal headlands, in which the effect of distance was measured under conservation headland and conventional (fully sprayed) management.Yields in the headland surveys varied from 0·8 to 10·2 t/ha. An inverse polynomial regression model was fitted to yield and weed data. Best fits were obtained by using separate parameters for each site. Adjusting yields to take account of weed dry matter improved the non-linear fit between yield and distance from crop edge. Field experiments provided similar results but the non-linear relationship was not as apparent.There was a negative relationship between soil compaction, as measured by a cone penetrometer, and yield in one field experiment, where soil density values were relatively constant. No relationship was found between pattern of nitrogen fertilizer application and yield. Conservation headland management resulted in lower yield at one experimental site, especially in the third year, but not at the other site. Where yields were affected, weed dry matter was higher in conservation headland plots than in fully sprayed plots.Although greater weed competition appears to account for at least part of the observed yield reductions on headlands, the role of other factors, particularly soil compaction, needs further study. Increased weed infestation may be an indirect result of reduced crop competition caused by other adverse conditions.

Qualitative assessment of air pollution in the working area of energy-intensive materials production by nanoscale aerosols with a solid dispersed phase

2021 ◽  
Vol 61 (12) ◽  
pp. 828-832
Author(s):  
Boris N. Filatov ◽  
Natalya I. Latyshevskaya ◽  
Natalya V. Krylova ◽  
Irina K. Gorkina ◽  
Yulya I. Velikorodnaya ◽  
...  
Keyword(s):  
Air Pollution ◽  
Mass Concentration ◽  
Solid Phase ◽  
Qualitative Assessment ◽  
Dust Particles ◽  
Dispersed Phase ◽  
Forced Circulation ◽  
Aluminum Powders ◽  
Nanoscale Particles ◽  
Wide Range

The presence of grinding, mixing, and fractionation of solid components of formulations leads to the formation of aerosols in the air of the working area with a wide range of dispersion of the solid phase - all this characterizes the organization of technological processes for the production of energy-intensive materials. The study aims to give a qualitative assessment of possible air pollution of the working area of energy-intensive materials production by nanoscale aerosols with a solid dispersed phase. The researchers carried out the sampling of the working area air and flushes from solid horizontal surfaces to produce energy-intensive materials. We carried out the sampling by forced circulation of the test air through the absorption devices of Polezhaev. Scientists used Triton TX-114 solution with a mass concentration of 2.0 mg/dm3 as an absorption medium. The researchers performed flushing from surfaces using cloth tampons moistened with Triton TX-114 solution with a mass concentration of 2.0 mg/dm3. We determined the particle sizes in the samples using NanotracULTRA (Microtrac). Scientists found aluminum and nitrocellulose particles with sizes from 36 to 102 nm in the air of the working area and flushes from horizontal surfaces. The study of the fractional composition of RDX and aluminum powders of the ASD-1 brand showed the presence of nanoscale particles in them. Nanoscale dust particles pollute the air of the working area and solid horizontal surfaces at certain stages of the production of energy-intensive materials. There are nanoscale particles in the composition of powders of some standard components of formulations. Flushes from solid horizontal surfaces are an adequate qualitative indicator of the presence of nanoaerosols in the air of the working area.

scholarly journals Coarse and giant particles are ubiquitous in Saharan dust export regions and are radiatively significant over the Sahara

2020 ◽  
Author(s):  
Claire Ryder ◽  
Eleanor Highwood ◽  
Adrian Walser ◽  
Petra Walser ◽  
Anne Philipp ◽  
...  
Keyword(s):  
Mass Concentration ◽  
Size Range ◽  
State Of The Art ◽  
Chem Phys ◽  
Saharan Dust ◽  
Dust Particles ◽  
Field Campaign ◽  
Dust Transport ◽  
Coarse Mode ◽  
Significant Underestimation

&lt;p&gt;Mineral dust is an important component of the climate system, interacting with radiation, clouds, and biogeochemical systems and impacting atmospheric circulation, air quality, aviation, and solar energy generation. These impacts are sensitive to dust particle size distribution (PSD), yet models struggle or even fail to represent coarse (diameter (&lt;span&gt;&lt;em&gt;d&lt;/em&gt;&lt;/span&gt;)&amp;#160;&lt;span&gt;&gt;2.5&lt;/span&gt;&amp;#8201;&lt;span&gt;&amp;#181;&lt;/span&gt;m) and giant (&lt;span&gt;&lt;em&gt;d&lt;/em&gt;&gt;20&lt;/span&gt;&amp;#8201;&lt;span&gt;&amp;#181;&lt;/span&gt;m) dust particles and the evolution of the PSD with transport. Here we examine three state-of-the-art airborne observational datasets, all of which measured the full size range of dust (&lt;span&gt;&lt;em&gt;d&lt;/em&gt;=0.1&lt;/span&gt;&amp;#160;to&amp;#160;&lt;span&gt;&gt;100&lt;/span&gt;&amp;#8201;&lt;span&gt;&amp;#181;&lt;/span&gt;m) at different stages during transport with consistent instrumentation. We quantify the presence and evolution of coarse and giant particles and their contribution to optical properties using airborne observations over the Sahara (from the Fennec field campaign) and in the Saharan Air Layer (SAL) over the tropical eastern Atlantic (from the AER-D field campaign).&lt;/p&gt;&lt;p&gt;Observations show significantly more abundant coarse and giant dust particles over the Sahara compared to the SAL: effective diameters of up to 20&amp;#8201;&lt;span&gt;&amp;#181;&lt;/span&gt;m were observed over the Sahara compared to 4&amp;#8201;&lt;span&gt;&amp;#181;&lt;/span&gt;m in the SAL. Excluding giant particles over the Sahara results in significant underestimation of mass concentration (40&amp;#8201;%), as well as underestimates of both shortwave and longwave extinction (18&amp;#8201;% and 26&amp;#8201;%, respectively, from scattering calculations), while the effects in the SAL are smaller but non-negligible. The larger impact on longwave extinction compared to shortwave implies a bias towards a radiative cooling effect in dust models, which typically exclude giant particles and underestimate coarse-mode concentrations.&lt;/p&gt;&lt;p&gt;A compilation of the new and published effective diameters against dust age since uplift time suggests that two regimes of dust transport exist. During the initial 1.5&amp;#8201;d, both coarse and giant particles are rapidly deposited. During the subsequent 1.5 to 10&amp;#8201;d, PSD barely changes with transport, and the coarse mode is retained to a much greater degree than expected from estimates of gravitational sedimentation alone. The reasons for this are unclear and warrant further investigation in order to improve dust transport schemes and the associated radiative effects of coarse and giant particles in models.&lt;/p&gt;&lt;p&gt;This work has been recently published in ACP (Ryder, C. L., Highwood, E. J., Walser, A., Seibert, P., Philipp, A., and Weinzierl, B.: Coarse and giant particles are ubiquitous in Saharan dust export regions and are radiatively significant over the Sahara, Atmos. Chem. Phys., 19, 15353&amp;#8211;15376, https://doi.org/10.5194/acp-19-15353-2019, 2019).&lt;/p&gt;

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