Effect of Mineral Dusts on the Growth of Silicate Bacteria S35

In order to compare the chemical compositions and physical properities of dusts on silicate bacteria S35, the chemical compositions of six kinds of mineral dusts have been analyzed and the changes of pH value, glucose （GLU）, electrolyte and Mn, Si, Fe before and after the dusts reacted with silicate bacteria S35 have been measured. The SEM analysis has been used to study the bacterial form and interface action status in the course of reaction between dusts and bacteria. The results show that these mineral dusts have different effects on experiment bacteria. Therefore, it is concluded that the effect of mineral dusts on silicate bacteria has correlation with the chemical compositions and physical properities of dusts.

A Study on Cellular Reactions and Fibrogenic Effectsof Mineral Dusts

In vivo cytotoxicity including cellular metabolic activity, lysozyme content and total protein content in rat bronchoalveolar lavage, capacity of interleukin-1 released from rat pulmonary cells and fibrogenic effects evaluated from rat lung dry weight, collagen content of the whole lung and pathological grading induced by mineral dust were assayed. The results showed that: (1) The relationship among in vivo cytotoxicity, interleukin-1 release,fibrogenic effects on the lung induced by mineral dusts correlated well with the free SiO2content in mineral dusts in most (but not all) cases; (2) The biological harmful effects of mixed dusts were not simply the additive effect of single dust. In the group of WO3-SiO2mixture, the fibrogenicity was mainly due to SiO2, tungsten trioxide (WO3) showed neither fibrogenic effect, nor significant potentiality to enhance SiO2 fibrogenicity, while in the group of SnO2-SiO2, SnO2 was suppressive to the effect of SiO2, although the contents of SiO2 in the two mixed dusts were similar

FURTHER STUDIES ON THE MALIGNANT TRANSFORMATION OF SYRIAN GOLDEN HAMSTER EMBRYO CELLS IN VITR0 BY THORIUM DIOXIDE AND RARE EARTH IRON MINERAL DUSTS

Malignant transformation of hamsterembryo cells was induced in vitro by rareearth iron mineral dusts(MP),naturalthorium(Th02) and MP plus Th02.Dusts of MP,MP plus Th02 or Th02 were added into themedium with the final concentration of 17.0,

Mechanism for the promotional formation of NH_(4)^(+) by SO_(2) on different mineral dust surfaces

Ammonium is an important atmospheric particulate component that dictates many environmental processes.The promotion of the heterogeneous conversion of NH_(3) to NH_(4)^(+) by SO_(2) on different mineral dust surfaces displays remarkable discrepancies,especially on MgO and α-Fe2O3 surfaces,however,the underlying mechanisms are not well known.Here,using periodic density functional theory(DFT)calculation and Born-Oppenheimer molecular dynamics(BOMD)simulation,we explored the hetero-geneous adsorption of NH_(3) on MgO(110)and α--Fe2O3(001)surfaces in the presence and absence of SO_(2).The results show that on MgO(110)surface,hydrogen-bonding interactions of NH_(3) on both adsorbed hydroxyl or bisulfite/bisulfate sites are observed no matter whether SO_(2) is present or not.While,on theα-Fe2O3(001)surface,significant conversion of NH_(3) to NH_(4)^(+)occurs with the coexistence of SO_(2),which is due to the hydrogen transfer reaction from surface HSO4 to N in NH_(3).The fundamental reason may be that the stronger electron affinity of Fe3+than Mg2+results in adsorbed bisulfate and/or bisulfite with greater acidity on α-Fe2O3 surface than MgO surface.Our results give a molecular-level explanation for the heterogeneous conversion of NH_(3) to NH_(4)^(+)on different mineral dust surfaces under complex air pollution conditions.Considering the fact that ammonium is abundant in secondary particulates,this work would help in understanding the rapid conversion of ammonia to ammonium and in developing classification governance policies for the key precursor pollutants in China.

An Overview of the Studies on Black Carbon and Mineral Dust Deposition in Snow and Ice Cores in East Asia

Black carbon （BC） is the most eff ective insoluble light-absorbing particulate （ILAP）, which can strongly absorb solar radiation at visible wavelengths. Once BC is deposited in snow via dry or wet process, even a small amount of BC could signifi cantly decrease snow albedo, enhance absorption of solar radiation, accelerate snow melting, and cause climate feedback. BC is considered the second most important component next to CO2 in terms of global warming. Similarly, mineral dust （MD） is another type of ILAP. So far, little attention has been paid to quantitative measurements of BC and MD deposition on snow surface in the midlatitudes of East Asia, especially over northern China. In this paper, we focus on reviewing several experiments performed for collecting and measuring scavenging BC and MD in the high Asian glaciers over the mountain range （such as the Himalayas） and in seasonal snow over northern China. Results from the surveyed literature indicate that the absorption of ILAP in seasonal snow is dominated by MD in the Qilian Mountains and by local soil dust in the Inner Mongolian region close to dust sources. The detection of BC in snow and ice cores using modern techniques has a large bias and uncertainty when the snow sample is mixed with MD. Evidence also indicates that the reduction of snow albedo by BC and MD perturbations can signifi cantly increase the net surface solar radiation, cause surface air temperature to rise, reduce snow accumulation, and accelerate snow melting.

Heterogeneous uptake of nitrogen dioxide on Chinese mineral dust

Mineral dust is one of the major aerosols in the atmosphere.To assess its impact on trace atmospheric gases,in this work we present a laboratory study of the effect of temperature on the heterogeneous reaction of NO2 on the surface of ambient Chinese dust over the temperature range from 258 to 313 K.The results suggest that nitrogen dioxide could mainly be adsorbed on these types of Chinese mineral dust reversibly with little temperature dependence.Similar to a previous study on NO2 uptake on mineral aerosols,the uptake coefficients are mainly on the order of 10^（-6） for the Chinese dust,when BET areas are taken into account.HONO was observed as a product,and its formation and decomposition on Chinese mineral dust during the uptake processes were also studied.The complete dataset from this study was compiled with previous literature determinations.Atmospheric implications of the heterogeneous reaction between NO2 and mineral dust are also discussed,in an effort to understand this important heterogeneous process.

Knudsen cell and smog chamber study of the heterogeneous uptake of sulfur dioxide on Chinese mineral dust

The heterogeneous uptake processes of sulfur dioxide on two types of Chinese mineral dust（Inner Mongolia desert dust and Xinjiang sierozem） were investigated using both Knudsen cell and smog chamber system. The temperature dependence of the uptake coefficients was studied over a range from 253 to 313 K using the Knudsen cell reactor, the initial uptake coefficients decreased with the increasing of temperature for these two mineral dust samples, whereas the steady state uptake coefficients of the Xinjiang sierozem increased with the temperature increasing, and these temperature dependence functions were obtained for the first time. In the smog chamber experiments at room temperature, the steady state uptake coefficients of SO2 decreased evidently with the increasing of sulfur dioxide initial concentration from 1.72 × 1012 to 6.15 × 1012mol/cm3. Humid air had effect on the steady state uptake coefficients of SO2 onto Inner Mongolia desert dust.Consequences about the understanding of the uptake processes onto mineral dust samples and the environmental implication were also discussed.

COMPARISON OF SIMULATING MINERAL DUST AEROSOLS IN EAST ASIA BY TWO EMISSION SCHEMES

Two common surface-dust emission schemes using critical wind speed and friction velocity were compared with the regional climate model RegCM3 in East Asia. In the comparison, transport of mineral dust and its distribution were simulated from March to April, 2001. Simulation results were also compared with TOMS aerosol index, showing that obvious differences exist in dust emission quantity and its column burden simulated by the dust emission schemes of friction velocity and wind speed criteria. The results obtained by the wind speed criterion are higher than that by friction velocity, bringing forth the problem whether or not the dust emission scheme matches the model. The obvious difference in the two schemes also explains the uncertainty of simulating mineral dust aerosol by modeling.

A Comparison of the Physical and Optical Properties of Anthropogenic Air Pollutants and Mineral Dust over Northwest China

Emissions of mineral dust and its mixing with anthropogenic air pollutants affect both regional and global climates. Our fieldwork in late spring 2007（April 25-June 15） measured the physical and optical properties of dust storms mixed with local air pollutants at a rural site about 48 km southeast of central Lanzhou. Levels of air pollutants and aerosol optical properties were observed during the experiment, with concentrations of NOx（6.8 ± 3.3 ppb, average ± standard deviation）, CO（694 ± 486 ppb）, SO2（6.2 ±10 ppb）, O3（50.7 ± 13.1 ppb）, and PM10（172 ± 180 μg m-3）, and aerosol scattering coefficient（164 ±89 Mm-1; 1 Mm = 106m） and absorption coefficient（11.7 ± 6.6 Mm-1）, all much lower than the values observed during air pollution episodes in urban areas. During a major dust storm, the mass concentration of PM10 reached 4072 μg m-3, approximately 21-fold higher than in non-dust storm periods. The mixing ratios of trace gases declined noticeably after a cold front passed through. The observed CO/SO2 and CO/NOx ratios during air pollution episodes were 4.2-18.3 and 13.7-80.5, respectively, compared with the corresponding ratios of 38.1-255.7 and 18.0-245.9 during non-pollution periods. Our investigations suggest that dust storms have a significant influence on air quality in areas far from their source, and this large-scale transport of dust and air pollutants produces major uncertainties in the quantification of the global effects of emissions over Northwest China.

A method for estimating the fraction of mineral dust in particulate matter using PM2.5-to-PM10 ratios

A simple method for estimating the contributions of mineral dust to PM2.5, PM10, or TSP is presented. The method is based on the assumption of external mixing of two types of particles with different PM2.5/PM10 ratios, The method was applied to local and transported dust events observed in Tsukuba, Japan, and was compared with collocated polarization lidar measurements. The method was then applied to three dust events that occurred in Oki, Rishiri, and Ochiishi,Japan, in 2012. The results showed that the method was useful for detecting mineral dust and for qualitatively describing the mixing of dust with anthropogenic aerosols.

Lidar Methods for Observing Mineral Dust

Lidar methods for observing mineral dust aerosols are reviewed.These methods include Mie scattering lidars,polarization lidars,Raman scattering lidars,high-spectral-resolution lidars,and fluorescence lidars.Some of the lidar systems developed by the authors and the results of the observations and applications are introduced.The largest advantage of the lidar methods is that they can observe vertical distribution of aerosols continuously with high temporal and spatial resolutions.Networks of ground-based lidars provide useful data for understanding the distribution and movement of mineral dust and other aerosols.The lidar network data are actually used for validation and assimilation of dust transport models,which can evaluate emission,transport,and deposition of mineral dust.The lidar methods are also useful for measuring the optical characteristics of aerosols that are essential to assess the radiative effects of aerosols.Evolution of the lidar data analysis methods for aerosol characterization is also reviewed.Observations from space and ground-based networks are two important approaches with the lidar methods in the studies of the effects of mineral dust and other aerosols on climate and the environment.Directions of the researches with lidar methods in the near future are discussed.

Mineral dust resuspension under vibration: Onset conditions and the role of humidity

The vibration of dusty surfaces inevitably causes re-entrainment of particles into the atmosphere.Given that movement of mineral dust particles deposited on a surface begins at a critical frequency (fc) and amplitude,an experimental laboratory study was conducted to determine the onset conditions for resuspension of a vibrated granular soil.We determined the resuspension state diagram as a function of frequency and amplitude of a sinusoidal vibration,the granulometry of the dust and the thickness of the soil bed.The mitigation effect of humidity was also evaluated.Critical frequencies ranged between 2.5 and 23 Hz when amplitudes were less than 12 rmm.These results were independent of bed thickness and perturbation type.For all particle sizes observed,fc decreased monotonically with A,contrasting with behavior observed for individual particles.In dry samples,fe for large size classes was markedly less when A was greater than 6 mm;while thefc for fine fractions only decreased once amplitudes reached 10 mm.Experiments with wet granular soils demonstrated that wetting above an optimum humidity did not necessarily impede movement and caused agglomeration.This study provides guidelines for managing resuspension of granular soils subjected to vibrations.

Heterogeneous uptake of gaseous hydrogen peroxide on mineral dust

The heterogeneous uptake processes of hydrogen peroxide on Arizona test dust and two types of authentic Chinese mineral dusts, i.e., Inner Mongolia desert dust and Xinjiang calciferous dust, were investigated using a Knudsen cell reactor coupled with a quadrupole mass spectrometer. The uptake coefficients were measured as a function of the initial concentration of H_2O_2 from 2.6 × 10^（11） to 1.2 × 10^（12）molecules/cm^3, and the temperature dependence of the uptake coefficients was investigated over a range from 253 to 313 K. The concentration of H_2O_2 showed little effect on the uptake coefficients of these heterogeneous processes. As a function of temperature, the initial uptake coefficients decrease with increasing temperature, whereas the steady state uptake coefficients of Arizona test dust and Inner Mongolia desert dust increase with increasing temperature. Implications for the understanding of the uptake processes onto mineral dust samples were also discussed.

Mineralization and Cementation of Fugitive Dust based on the Utilization of Carbon Dioxide and Its Characterization

Fugitive dust was cemented, forming larger particles bond in the calcite-consolidation-layer by microbial method. The particular composition, the morphology, and thermal decomposition properties of the samples were characterized by X-ray diffraction（XRD）, scanning electron microscopy（SEM）, Fourier transform infrared（FTIR） spectroscopy, and differential scanning calorimetry-thermogravimetry（DSC-TG）. The characterization data obtained showed that loose fugitive dust particles could be bonded and formed the consolidation-layer under the effect of calcite obtained by microbial method successfully. Meanwhile, the sample obtained by microbial method had superior wind-erosion resistance.

Heterogeneous reaction of NO_(2) with feldspar, three clay minerals and Arizona Test Dust

Heterogeneous reaction of NO_(2) with mineral dust aerosol may play important roles in troposphere chemistry,and has been investigated by a number of laboratory studies.However,the influence of mineralogy on this reaction has not been well understood,and its impact on aerosol hygroscopicity is not yet clear.This work investigated heterogeneous reactions of NO_(2)(∼10 ppmv)with K-feldspar,illite,kaolinite,montmorillonite and Arizona Test Dust(ATD)at room temperature as a function of relative humidity(<1%to 80%)and reaction time(up to 24 hr).Heterogeneous reactivity towards NO_(2) was low for illite,kaolinite,montmorillonite and ATD,and uptake coefficients of NO_(2),γ(NO_(2)),were determined to be around or smaller than 1×10^(−8);K-feldspar exhibited higher reactivity towards NO_(2),and CaCO_(3) is most reactive among the nine mineral dust samples considered in this and previous work.After heterogeneous reaction with NO_(2) for 24 hr,increase in hygroscopicity was nearly insignificant for illite,kaolinite and montmorillonite,and small but significant for K-feldspar;in addition,large increase in hygroscopicity was observed for ATD,although the increase in hygroscopicity was still smaller than CaCO_(3).

Enhanced secondary organic aerosol formation during dust episodes by photochemical reactions in the winter in Wuhan

To investigate the effect of frequently occurring mineral dust on the formation of secondary organic aerosol(SOA),106 volatile organic compounds(VOCs),trace gas pollutants and chemical components of PM_(2.5) were measured continuously in January 2021 in Wuhan,Central China.The observation period was divided into two stages that included a haze period and a following dust period,based on the ratio of PM_(2.5) and PM_(10) concentrations.The average ratio of secondary organic carbon(SOC)to elemental carbon(EC)was 1.98 during the dust period,which was higher than that during the haze period(0.69).The contribution of SOA to PM_(2.5) also increased from 2.75% to 8.64%.The analysis of the relationships between the SOA and relative humidity(RH)and the odd oxygen(e.g.,O_(X)=O_(3)+NO_(2))levels suggested that photochemical reactions played a more important role in the enhancement of SOA production during the dust period than the aqueous-phase reactions.The heterogeneous photochemical production of OH radicals in the presence of metal oxides during the dust period was believed to be enhanced.Meanwhile,the ratios of trans-2-butene to cis-2-butene and m-/p-xylene to ethylbenzene(X/E)dropped significantly,confirming that stronger photochemical reactions occurred and SOA precursors formed efficiently.These results verified the laboratory findings that metal oxides in mineral dust could catalyse the oxidation of VOCs and induce higher SOA production.

Effects of heterogeneous reaction with NO_(2) on ice nucleation activities of feldspar and Arizona Test Dust

Mineral dust is an important type of ice nucleating particles in the troposphere;however,the effects of heterogeneous reactions on ice nucleation(IN)activities of mineral dust remain to be elucidated.A droplet-freezing apparatus(Guangzhou Institute of Geochemistry Ice Nucleation Apparatus,GIGINA)was developed in thiswork to measure IN activities of atmospheric particles in the immersion freezingmode,and its performancewas validated by a series of experimental characterizations.This apparatus was then employed to measure IN activities of feldspar and Arizona Test Dust(ATD)particles before and after heterogeneous reaction with NO_(2)(10±0.5 ppmv)at 40%relative humidity.The surface coverage of nitrate,θ(NO_(3)^(−)),increased to 3.1±0.2 for feldspar after reaction with NO_(2) for 6 hr,and meanwhile the active site density per unit surface area(ns)at-20℃ was reduced from 92±5 to<1.0 cm^(−2) by about two orders of magnitude;however,no changes in nitrate content or IN activities were observed for further increase in reaction time(up to 24 hr).Both nitrate content and IN activities changed continuously with reaction time(up to 24 hr)for ATD particles;after reaction with NO_(2) for 24 hr,θ(NO_(3)^(−))increased to 1.4±0.1 and ns at-20℃ was reduced from 20±4 to 9.7±1.9 cm^(−2) by a factor of∼2.Our work suggests that heterogeneous reaction with NO_(2),an abundant reactive nitrogen species in the troposphere,may significantly reduce IN activities of mineral dust in the immersion freezing mode.

A case study of Asian dust storm particles:Chemical composition,reactivity to SO_2 and hygroscopic properties

Mineral dust comprises a great fraction of the global aerosol loading,but remains the largest uncertainty in predictions of the future climate due to its complexity in composition and physico-chemical properties.In this work,a case study characterizing Asian dust storm particles was conducted by multiple analysis methods,including SEM-EDS,XPS,FT-IR,BET,TPD/mass and Knudsen cell/mass.The morphology,elemental fraction,source distribution,true uptake coefficient for SO 2,and hygroscopic behavior were studied.The major components of Asian dust storm particles are aluminosilicate,SiO 2 and CaCO 3,with organic compounds and inorganic nitrate coated on the surface.It has a low reactivity towards SO 2 with a true uptake coefficient,5.767×10-6,which limits the conversion of SO 2 to sulfate during dust storm periods.The low reactivity also means that the heterogeneous reactions of SO 2 in both dry and humid air conditions have little effect on the hygroscopic behavior of the dust particles.

Microscopic Analyses of Insoluble Particles in an Ice Core of ürümqi Glacier No. 1: Quantification of Mineral and Organic Particles

Insoluble particle concentration in ice cores is commonly analyzed as a proxy for varia- tions in atmospheric mineral dust （aerosol concentration）. However, recent studies have revealed that the mineral dust is not only a constituent of the particles but that biogenic organic particles are also contained. We microscopically analyzed insoluble particles in a shallow ice core drilled on a mountain glacier, the Urumqi Glacier No. 1, in eastern Tienshan, China. We distinguished different morphological particles in the ice core and quantified them separately. Results showed that the insoluble particles in this ice core consisted mainly of mineral particles, amorphous organic particles, pollen, and micro- organisms. Mineral particles were the most dominant, accounting for approximately 67% of total par- ticles, and amorphous organic particles were the second most dominant, accounting for approximately 33% of the total. The annual variation in the particles for the last 11 years differed between mineral and amorphous organic particles. The results suggest that the total insoluble particle concentration in the ice core reflects not only the atmospheric mineral dust but also the organic particles blown from ground soil or produced by microbes on the glacial surface.

Impact of greenhouse gas CO_(2) on the heterogeneous reaction of SO_(2) on alpha-Al_(2)O_(3)

The heterogeneous reaction of SO_(2) on mineral dust surfaces is generally considered as an important chemical pathway for secondary sulfate formation in the troposphere.To this day,there are no reported studies that assess the impact of atmospheric CO_(2) in sulfate production on mineral dust surfaces.In this work,we investigate the impact of CO_(2) on SO_(2) uptake on dust proxy aluminum oxide particles using a diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS).CO_(2) is demonstrated to suppress the heterogeneous oxidation of SO_(2) on alpha-Al2 O_(3).Compared to that measured in the CO_(2)-free case,the uptake coefficient is decreased by nearly 57%when Al_(2)O_(3) particles are exposed to the gas flow with atmospheric CO_(2) at a relative humidity(RH)of 25%.It is also found that there is a balance between the yield of active moiety-OH provided by AI(OH)3(CO)(OH)2 clusters and the loss of basic hydroxyl group on aluminum oxide surfaces blocked by CO_(2)-derived(bi)carbonate species.This work,for the first time,reveals a negative effect of atmospheric CO_(2) on the sulfate formation,which potentially decreases solarradiation scattering and further exacerbates global warming.