O3 Series Research Articles

Screening Ba0.9A0.1MnO3 and Ba0.9A0.1Mn0.7Cu0.3O3 (A = Mg, Ca, Sr, Ce, La) Sol-Gel Synthesised Perovskites as GPF Catalysts.

Ba0.9A0.1MnO3 (BM-A) and Ba0.9A0.1Mn0.7Cu0.3O3 (BMC-A) (A = Mg, Ca, Sr, Ce, La) perovskite-type mixed oxides were synthesised, characterised, and used for soot oxidation in simulated Gasoline Direct Injection (GDI) engine exhaust conditions. The samples have been obtained by the sol-gel method in an aqueous medium and deeply characterised. The characterization results indicate that the partial substitution of Ba by A metal in BaMnO3 (BM) and BaMn0.7Cu0.3O3 (BMC) perovskites: (i) favours the hexagonal structure of perovskite; (ii) improves the reducibility and the oxygen desorption during Temperature-Programmed Desorption (O2-TPD) tests and, consequently, the oxygen mobility; (iii) mantains the amount of oxygen vacancies and of Mn(IV) and Mn(III) oxidation states, being Mn(IV) the main one; and (iv) for Ba0.9A0.1Mn0.7Cu0.3O3 (BMC-A) series, copper is partially incorporated into the structure. The soot conversion data reveal that Ba0.9La0.1Mn0.7Cu0.3O3 (BMC-La) is the most active catalyst in an inert (100% He) reaction atmosphere, as it presents the highest amount of copper on the surface, and that Ba0.9Ce0.1MnO3 (BM-Ce) is the best one if a low amount of O2 (1% O2 in He) is present, as it combines the highest emission of oxygen with the good redox properties of Ce(IV)/Ce(III) and Mn(IV)/Mn(III) pairs.

Identifying nonlinear interactions between PM2.5 and O3 on small time scales with visibility graph approaches

Identifying nonlinear interactions between PM2.5 and O3 is crucial for fully understanding atmospheric pollution. These interactions between PM2.5 and O3 involve complex chemical processes and boundary layer dynamics under different meteorological drivers. Due to the deficiency of traditional linear statistical methods (e.g. Pearson correlation or Pearson partial correlation analysis), they fail in quantifying nonlinear interactions between PM2.5 and O3 on small time scales and nonlinear features in PM2.5 and O3 series. We adopt two statistical indicators based on visibility graph (VG) algorithm to analyze the PM2.5 and O3 time series: average edge overlap (AEO) as measure for nonlinear interactions and Knp as measure for cross-scale interaction by frequency modulation (FM). Detail studies show that AEO is insensitive to large-scale nonstationary variations but indeed sensitive to nonlinear coupling variations in the tailored models with known prescribed coupling. The AEO can successfully identify true both linear and nonlinear interactions in these tailored models, while Pearson correlation analysis fails. Then AEO is applied to reanalysis data of PM2.5 and O3 to identify events with specific nonlinear interactions between PM2.5 and O3 with significant cross-scale interactions quantified by calculated Knp, which exist in both within and between these pollutant time series. Further analysis shows that the possible mechanisms underlying these nonlinear interactions may be mainly local mixing (or emission) and chemical processes related to meteorological drivers such as surface air temperature, surface solar radiation and surface relative humidity.

Impacts of Synoptic Patterns and Meteorological Factors on Distribution Trends of Ozone in Southeast China During 2015–2020

AbstractSurface ozone (O3) pollution under global climate change has become one of the top environmental issues. In this study, we focused on the coastal region in Southeast China with relatively low O3 precursor's emissions and complicated synoptic conditions, where the O3 trends and meteorological contributions remain unclear. An increasing trend of O3 concentrations in the cities (0.3–4.6 μg m−3 yr−1) from 2015 to 2020 was observed. Twenty‐three synoptic patterns were clustered based on weather typing method, in which cyclone‐related types and southwesterly type were generally associated with low O3 concentrations, and high O3 levels occurred with anticyclone‐related types. Considering both frequency and intensity of synoptic patterns, reconstructed O3 series captured 46.0%–58.3% of the observed variability. Using Kolmogorov‐Zurbenko filter, an increasing trend of long‐term O3 was found. By implementing the multiple linear regression model between O3 concentrations and meteorological factors, the meteorological contributions to O3 variabilities (44.7%–66.1%) were quantified. The results indicated the meteorological conditions were particularly important in O3 pollution with the reductions of O3 precursor's emissions, among which relative humidity, boundary layer height, solar radiation along with low cloud cover were proved to play important roles. The weakening southwest winds along with more anti‐cyclone systems under climate change could increase surface O3. This study elucidated the crucial meteorological drivers on the O3 variability in relatively clean areas and implied the challenges for local governments to mitigate O3 pollution under global climate change.

Research on Improving Energy Storage Density and Efficiency of Dielectric Ceramic Ferroelectric Materials Based on BaTiO3 Doping with Multiple Elements

In order to promote the research of green energy in the situation of increasingly serious environmental pollution, dielectric ceramic energy storage materials, which have the advantages of an extremely fast charge and discharge cycle, high durability, and have a broad use in new energy vehicles and pulse power, are being studied. However, the energy storage density of ordinary dielectric ceramic ferroelectric materials is low, so, in this paper, we have divided eight components based on BaTiO3 (BT). Through the traditional solid phase sintering method, AB positions were replaced with various elements of different proportions to improve their energy storage density and the energy storage efficiency of BT-based ferroelectric materials. In this paper, we studied the results of XRD, Raman, ferroelectric, dielectric, and impedance tests of doped samples, and the best components were determined. The (1−x)BT−xBi(Mg1/3Zn1/3Ta1/6Nb1/6)O3 series of ceramics are made by the incorporation of five elements, Bi3+, Mg2+, Zn2+, Ta5+, and Nb5+. With the rising electric hysteresis loop of the doping amount x thin, the saturation polarization strength and residual polarization strength decrease, and the energy storage density rises first and then decreases. The dielectric characteristic after x = 0.08 showed a flat dielectric peak, indicating that the ferroelectric relaxation had been formed. The energy storage density and efficiency of the best component x = 0.12 reached 1.75 J/cm3 and 75%, respectively, and the Curie temperature was about −20 °C, so it has the potential to be used at room temperature.

Composition-, temperature- and pressure-induced transitions between high-pressure stabilized perovskite phases of the (1-x)BiFe0.5Sc0.5O3 - xLaFe0.5Sc0.5O3 series

Crystal structures of the high-pressure synthesized perovskite phases of the (1-x)BiFe0.5Sc0.5O3-xLaFe0.5Sc0.5O3 (0 ​= ​x ​≤ ​1) system and their temperature and pressure behaviours were studied using laboratory and synchrotron X-ray diffractions as well as neutron diffraction. At room temperature, the as-prepared phases with x ​≤ ​0.05 have an antipolar structure with the Pnma symmetry and with the √2ap ​× ​4ap ​× ​2√2ap superstructure (where ap is the pseudocubic perovskite unit-cell parameter). An incommensurately modulated phase with the Imma(00γ)s00 superspace group is observed for 0.10 ​= ​x ​≤ ​0.33, while a non-polar Pnma phase (√2ap ​× ​2ap ​× ​√2ap) is stable when x ​≥ ​0.34. The antipolar Pnma phase in the as-prepared samples with composition corresponding to x ​= ​0 transforms into the polar Ima2 one via irreversible annealing-caused transformation accompanied by a formation of a high-temperature intermediate polar R3c polymorph, while the antipolar Pnma phase in samples with x ​= ​0.05 is stable until the decomposition temperature. In the solid solutions with 0.10 ​= ​x ​≤ ​0.33, increasing temperature was found to result in a reversible transformation of the Imma(00γ)s00 phase into a non-polar Pnma one. The transition temperature decreases with increasing x. A hydrostatic pressure of few GPa was also shown to induce a reversible Imma(00γ)s00 → Pnma transformation.

High-Pressure Synthesized Perovskite CdMnO3 with C-Type Antiferromagnetic Spin Configuration

CdMnO3 had not been previously reported and was a missing piece in the A2+Mn4+O3 series. We succeeded in synthesizing this compound by a high-pressure method and confirmed that it is crystallized in a distorted perovskite structure with a Cd2+Mn4+O3 charge configuration. The obtained insulating CdMnO3 exhibits an antiferromagnetic transition at about 86 K. First-principles calculations revealed that the Mn4+ (t2g3) spins form a C-type antiferromagnetic structure, which is in sharp contrast to the G-type antiferromagnetism in the isostructural and isoelectronic CaMnO3. Significant overlap of the Mn-3d and O(2)-2p orbitals produces distorted octahedra with a large Mn-O(1)-Mn tilt and induces antiferromagnetic couplings in the ac plane and the ferromagnetic couplings along the b axis.

The Dynamic Impacts of COVID-19 Pandemic Lockdown on the Multifractal Cross-Correlations between PM2.5 and O3 Concentrations in and around Shanghai, China

Although the outbreak of the COVID-19 pandemic caused serious restrictions on human activities in and around Shanghai, China, the period can be viewed as a helpful experiment to investigate the correlation between PM2.5 and O3 concentrations. In this study, the hourly PM2.5 and O3 series in four cities (i.e., Shanghai, Jiaxing, Nantong and Suzhou) from 27 November 2019 to 23 March 2020 are used. The “seesaw effect” is observed in the study data. The dynamic impacts of the COVID-19 pandemic on the multifractal cross-correlations and the coordinated control degree of PM2.5-O3 are examined in these cities. First of all, the multifractal cross-correlations, multifractality components and dynamic influences of the COVID-19 pandemic on cross-correlations between PM2.5 and O3 in four cities are illustrated. Furthermore, a new quantification index, ζ, evaluating the coordinated control degree of PM2.5-O3 is developed, validated and compared. The multifractal cross-correlation analysis results reveal that the cross-correlations between PM2.5 and O3 in and around Shanghai both before and during the COVID-19 partial lockdown have multifractal characteristics. Moreover, there are weaker multifractal cross-correlation degrees of PM2.5-O3 in four cities during the COVID-19 partial lockdown. The multifractal cause analysis based on stochastic simulation illustrates that the impacts of multifractality due to the nonlinear correlation part are greater than the linear correlation part and the fat-tailed probability distribution part in and around Shanghai. The intrinsic multifractal cross-correlations decreased in all cities during the COVID-19 lockdown. However, the effects of the COVID-19 lockdown on the multifractal cross-correlations are limited from the perspective of intrinsic multifractality. The mean values of ζ in and around Shanghai all increase during the COVID-19 partial lockdown, which indicates that the PM2.5-O3 coordinated control degrees in all four cities become weaker.

Magnetic Behaviour of Perovskite Compositions Derived from BiFeO3

The phase content and sequence, the crystal structure, and the magnetic properties of perovskite solid solutions of the (1−y)BiFeO3–yBiZn0.5Ti0.5O3 series (0.05 ≤ y ≤ 0.90) synthesized under high pressure have been studied. Two perovskite phases, namely the rhombohedral R3c and the tetragonal P4mm, which correspond to the structural types of the end members, BiFeO3 and BiZn0.5Ti0.5O3, respectively, were revealed in the as-synthesized samples. The rhombohedral and the tetragonal phases were found to coexist in the compositional range of 0.30 ≤ y ≤ 0.90. Magnetic properties of the BiFe1−y[Zn0.5Ti0.5]yO3 ceramics with y < 0.30 were measured as a function of temperature. The obtained compositional variations of the normalized unit-cell volume and the Néel temperature of the BiFe1−y[Zn0.5Ti0.5]yO3 perovskites in the range of their rhombohedral phase were compared with the respective dependences for the BiFe1−yB3+yO3 perovskites (where B3+ = Ga, Co, Mn, Cr, and Sc). The role of the high-pressure synthesis in the formation of the antiferromagnetic states different from the modulated cycloidal one characteristic of the parent BiFeO3 is discussed.

RbMT3 (BO3 )2 O3 (M=Ba, Sr; T=Al, Ga): New Double-Layered Oxyborates Constructed from [BO3 ] Triangles and [TO4 ] Tetrahedra.

Four new alumino-/galloborates RbMT3 (BO3 )2 O3 (M=Ba, Sr; T=Al, Ga) have been synthesized for the first time by using a high-temperature solution method. All the title compounds have Sr2 Be2 B2 O7 -like structures, in which the [BO3 ] triangles and [TO4 ] tetrahedra form the final double-layered configurations with the M- and Rb-site atoms located between and in the double layer, respectively. The structure evolution from Sr2 Be2 B2 O7 to RbMT3 (BO3 )2 O3 series is discussed. The broader energy bandgaps in Al-based borates when compared with Ga-based ones can be entirely attributed to the location of Al/Ga s orbitals near the Fermi surface. Both experimental and computational approaches were used to study their structure-property relationships.

A new lithium‐rich layer‐structured cathode material with improved electrochemical performance and voltage maintenance

Lithium-rich layered oxides (LRLOs) are highly attractive cathode materials for next-generation lithium-ion batteries because of their high reversible capacity, but poor cycle performance and voltage decay are two main problems that strongly limit their practical applications. These challenges also apply to the Ru-based LRLOs of Li2RuO3. The Li2RuO3 cathode material is highly attractive because of their high conductivity and favourable electrochemical reaction kinetics. To overcome the problems associated with Li2RuO3, in contrast to normal single atom doping, here, we propose a Na, Cr co-doping strategy with the design of Li2−xNaxRu0.95Cr0.05O3 (x = 0, 0.02, 0.06, and 0.1) series materials. Cr doping increases capacity, and Na doping suppresses voltage decay. As a result, the discharge capacity of the optimal Li1.98Na0.02Ru0.95Cr0.05O3 sample over 240 mAh/g after 50 charge-discharge cycles at 0.2 C is maintained, and the capacity retention reaches a value of 80.5% compared with 69.1% for the undoped Li2RuO3. The value of the voltage decay in the Li1.98Na0.02Ru0.95Cr0.05O3 sample is 125 mV after 100 cycles at a rate of 1 C, and the voltage decay is 188.4 mV for the undoped Li2RuO3. This finding will expand the scope for designing novel layered electrodes with excellent performance.

Metamagnetic transition in the system Eu1-xSrxMn0.5Co0.5O3 (0 ≤ x ≤ 0.75)

Magnetic properties of orthorhombic (space group Pnma) perovskite EuMn0.54+Co0.52+O3 synthesized at various temperatures are studied up to 140 kOe. The sample obtained at 1500 °C shows a metamagnetic behavior irreversible below 40 K, whereas the sample obtained at 1200 °C exhibits purely ferromagnetic behavior. Both samples are ordered at Curie temperature TC = 123 K and reach equal magnetizations at high magnetic fields. The substitution of Eu3+ by Sr2+ within Eu1-xSrxMn0.5Co0.5O3 series of compounds leads to the increase in TC, but the magnetization of these compositions strongly decreases and the metamagnetic transition disappears at x > 0.3. The composition with x = 0.75 is a cubic (Pm3¯m) antiferromagnet with Neel temperature TN ≈ 210 K. It is assumed that the metamagnetic transition is associated with a transition from a noncollinear into a collinear ferromagnetic phase. A noncollinear phase is formed due to the competition between positive Co2+ – Mn4+ and negative Mn4+ – Mn4+ and Co2+ – Co2+ superexchange interactions in the presence of large magnetic anisotropy. It is suggested that Sr2+ doping leads to formation of mixed high/low spin state of Co3+ ions and enforces antiferromagnetic component.

Concentration- and Temperature-Induced Phase Transitions in PrAlO3-SrTiO3 System.

Single-phase mixed aluminates-titanates Pr1−xSrxAl1−xTixO3 (x = 0.1, 0.2, 0.3, 0.5, 0.7) with rhombohedral perovskite structure were prepared by solid-state reaction technique at 1823–1873 K. Morphotropic rhombohedral-to-cubic phase transition in Pr1−xSrxAl1−xTixO3 series is predicted to occur at x = 0.88. The temperature-induced structural phase transition R overline{3} с − Pm overline{3} m in Pr0.5Sr0.5Al0.5Ti0.5O3, detected at 930 K by in situ high-temperature X-ray synchrotron powder diffraction, occurs at considerably lower temperature as the corresponding transformation in the parent compound PrAlO3 (1770 K). Such remarkable drop of the transition temperature is explained by gradual decrease of the perovskite structure deformation in the Pr1−xSrxAl1−xTixO3 series with increasing Sr and Ti contents as a consequence of the increasing Goldschmidt tolerance factor. For Pr0.3Sr0.7Al0.3Ti0.7O3 phase, a sequence of the low-temperature phase transformation R overline{3} с − Immb(C2/m) − I4/mcm was detected.

Microwave dielectric properties of Ga3+ and Ta5+ co-doped CaTiO3

Compositions in the (1 − x)CaTiO3–xCa(Ta1/2Ga1/2)O3 (x = 0.4, 0.45, 0.50, 0.55) series were processed through a solid-state mixed-oxide route. X-ray diffraction (XRD) of x = 0.5 and 0.55 compositions revealed the formation of single-phase ceramics with orthorhombic (Pbnm) symmetry. At x ≤ 0.45, a couple of low intensity XRD peaks matching PDF# 04-002-5066 for Ca3TiTaGa3O12 were also observed which indicated second-phase formation. The microstructure of the sintered pellets for x = 0.5 and 0.55 compositions comprised densely packed irregular-shaped large grains with uniform contrast. The unit cell volume increased with increasing Ta5+ and Ga3+ contents at the B-site, which caused a decrease in both the relative permittivity (er) and temperature coefficient of resonance frequency (τf) but an increase in quality factor (Q × fo). The optimum microwave dielectric properties (i.e., er ~ 47, Q × fo ~ 26,630 GHz and τf ~ −2.64 ppm/ °C) were achieved for the x = 0.5 composition (i.e., CaTi0.5Ta0.25Ga0.25O3) which can be a potential candidate material for microwave dielectric applications. Thus, the substitution of Ta and Ga at the B-site of CaTiO3 was useful in tuning the larger positive τf through zero and increasing Q × fo without too much compromise on er.

Quest for lead free relaxors in YIn(1-x)Fe(x)O₃ (0.0 ≤ x ≤ 1.0) system: role of synthesis and structure.

The B-site tailored YIn(1-x)Fe(x)O3 (0.0≤ x≤ 1.0) series was synthesized by glycine-aided gel-combustion technique and subjected to extensive structural and electrical investigations. The temperature had tremendous bearing on the phase evolution exhibited by the system. The entire system crystallized as C-type metastable polymorph in the as-synthesized form. Hexagonal polymorphs of Fe(3+)-rich compositions could be isolated by controlled heat treatment at 750 °C. Raman spectroscopic investigations showed that, while there is a general shrinkage of the lattice due to substitution of a smaller ion at In(3+)-site, there is an apparent dilation of the Y-O bond, and this anomaly reflects in the electrical behavior exhibited by the system. The single-phasic hexagonal nominal compositions, YIn(1-x)Fe(x)O3 (0.0 ≤ x ≤ 0.3), were also studied by impedance spectroscopy. The dielectric constant was found to drastically increase from 10 for YInO3 to 1000 for YIn(0.7)Fe(0.3)O3 at room temperature stressing the role of B-site tailoring on electrical behavior. More interestingly, careful substitution of Fe into YInO3 could tune the electrical behavior from a dielectric to relaxor ferroelectric in the temperature range studied. The nominal composition YIn(0.7)Fe(0.3)O3 showed a classical relaxor ferroelectric like behavior which is an important observation in context of the search for new lead free relaxor materials.

Dielectric Properties and Conductivity of Ferroelectric LixNa1-xTa 0.1Nb0.9O3 Solid Solutions

Results of a study of dielectric properties and conductivity of ferroelectric perovskite solid solutions of the LixNa1-xTa0.1Nb0.9O3 (х = 0.03–0.135) series with the 290–700 K thermal range and frequencies from 25 to 106 Hz are reported. The charge in this kind of materials is shown to be transferred by Li+ ions the contribution from bulk transport of ions dominating. A first order phase transition close to the second order transitions proceeds in LixNa1-xTa0.1Nb0.9O3 solid solutions within the thermal range examined. The increase of Li concentration enhances the features of the second order transition.

Evolution from Ferroelectric to Relaxor Behavior in the (1 − x)BaTiO3 − xLa(Mg1/2Ti1/2)O3 System

Ceramics of (1 − x)BaTiO3−xLa(Mg1/2Ti1/2)O3 series (x = 0, 0.025, 0.05, 0.075 and 0.1) were dielectrically investigated. Based on the dielectric and X-ray diffraction data, phase diagram of the system for the studied composition range has been determined. Apparent relaxor behavior was revealed to set in when the BaTiO3-type sequence of three phase transitions is reduced to only diffuse transition. No clear boundary was found between ferroelectric and relaxor compositions of the system. It was observed the continuous crossover from ferroelectric to relaxor behavior.

Preparation of Perovskite Pb(B0.5Nb0.5)O3 (B = Rare-Earth Elements)

Pb(B0.5Nb0.5)O3 (B = Sc, Y, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) powders were prepared from mixed nitrate solutions by a chemical coprecipitation method. This method produced very small particles (∼30 nm) with good compositional homogeneity. These powders were highly reactive upon calcination. The powders of the systems (B = Sc, Tm, Yb and Lu) yielded ∼100% perovskite phase after calcination between 800∘C and 1000∘C for 1 h. For the system with B = Er, 93% perovskite phase was formed at 900∘C for 1 h. For the other systems of the elements (B = Y, Nd, Sm, Eu, Gd, Tb, Dy and Ho) with a larger ionic size, perovskite compounds were not formed up to 1100∘C. The stability and the possible formation of the compounds with a perovskite structure for the Pb(B0.5Nb0.5)O3 series were discussed.

Effects of Niobium Addition on the Relaxor Ferroelectric Properties and Ordering Structures of Lead Iron Tantalates

Pyrochlore-free Pb(Fe1/2Ta1/2)O3, Pb(Fe1/2Nb1/2)O3, and complete series of solid solutions between them were fabricated and their ordering structures as well as their dielectric properties were investigated. The dielectric properties of Pb(Fe1/2Ta1/2)O3 were those of typical relaxor ferroelectrics showing evident dielectric relaxation and diffusive phase transition, but the degrees of diffusive phase transition and dielectric relaxation decreased as Ta5+ was replaced by Nb5+. Also, the Fe3+ and Ta5+ ions of Pb(Fe1/2Ta1/2)O3 were ordered within the nanoscale region, but the degree of ordering decreased as Ta5+ was replaced by Nb5+. The loss of relaxor ferroelectric characteristics in Pb(Fe1/2Ta1/2)O3 with the replacement of Ta5+ by Nb5+ was correlated with the weakening of the ordering.

Magnetic interaction in Mg, Ti, Nb doped manganites

An effect of Mn substitution with Me=Mg2+, Ti4+, Nb5+ in manganites has been investigated by preparing La0.7Sr0.3(Mn1-xMex)O3 and La1-xSrx(Mn1 - x/2Nbx/2)O3 series. It was established that substitution of manganese with magnesium up to x = 0.16 leads to a collapse of a long-range ferromagnetic order whereas La0.7Sr0.3(Mn 3 +0.85Nb 5 +0.15)O3 is ferromagnet with TC = 123 K and exhibits a large magnetoresistance below Curie point despite an absence of four-valent manganese. Hypothetical magnetic phase diagrams are constructed for La0.7Sr0.3(Mn1-xMex)O3 and La1-xSrx(Mn1 - x/2Nbx/2)O3. Our results show that Mn3+-O-Mn3+ exchange interaction is ferromagnetic in the orbitally disordered manganites as well as an increase of Mn4+ content above 50% from a total amount of manganese ions leads to formation of a spin glass state due to a competition between antiferromagnetic Mn4+-O-Mn4+ and ferromagnetic Mn3+-O-Mn4+(Mn3+) superexchange interactions.

Defining the Photochemical Contribution to Particulate Matter in Urban Areas Using Time-Series Analysis

The objective of this project is to demonstrate how the ambient air measurement record can be used to define the relationship between O3 (as a surrogate for photochemistry) and secondary particulate matter (PM) in urban air. The approach used is to develop a time-series transfer-function model describing the daily PM10 (PM with less than 10 μm aerodynamic diameter) concentration as a function of lagged PM and current and lagged O3, NO or NO2, CO, and SO2. Approximately 3 years of daily average PM10, daily maximum 8-hr average O3 and CO, daily 24-hr average SO2 and NO2, and daily 6:00 a.m.-9:00 a.m. average NO from the Aerometric Information Retrieval System (AIRS) air quality subsystem are used for this analysis. Urban areas modeled are Chicago, IL; Los Angeles, CA; Phoenix, AZ; Philadelphia, PA; Sacramento, CA; and Detroit, MI. Time-series analysis identified significant autocorrelation in the O3, PM10, NO, NO2,CO, and SO2 series. Cross correlations between PM10 (dependent variable) and gaseous pollutants (independent variables) show that all of the gases are significantly correlated with PM10 and that O3 is also significantly correlated lagged up to two previous days. Once a transfer-function model of current PM10 is defined for an urban location, the effect of an O3-control strategy on PM concentrations is estimated by calculating daily PM10 concentrations with reduced O3 concentrations. Forecasted summertime PM10 reductions resulting from a 5 percent decrease in ambient O3 range from 1.2 μg/m3 (3.03%) in Chicago to 3.9 μg/m3 (7.65%) in Phoenix.