Assessment of elemental chemistry, spatial distribution, and potential risks of road-deposited dusts in Sharjah, United Arab Emirates.

Road dust is a major source of pollution in the environment, carrying different pollutants, including heavy metals and metalloids, from one location to another. This study assesses the concentrations of eight heavy metals and one metalloid (Zn, Pb, Mn, Fe, Cr, Cu, Cd, Ni, and As) in dust samples collected from sixty-eight streets of Sharjah, United Arab Emirates using ICP-OES, as well as investigates their effects on both the environment and humans. Mean concentrations of the elements in µg/g across the sites were 392 ± 46 (Zn), 68.28 ± 11.3 (Pb), 1437 ± 67 (Mn), 39,481 ± 4611 (Fe), 460 ± 31 (Cr), 150 ± 44 (Cu), 1.25 ± 0.65 (Cd), 856 ± 72 (Ni), and 0.97 ± 0.28 (As). The Cdeg and ERI calculated from the study were 54.79 and 573, respectively, suggesting varying pollution levels. The highest contributions were from Ni, Cd, Zn, Cu, Cr, and Pb, especially in areas with heavy traffic. The non-carcinogenic risk assessments were generally low for the three routes of exposure, except HQoral that was slightly higher for children. Similarly, none of the elements exhibited any carcinogenic risk except chromium. Overall, the cancer risk is considered low. In view of the limited studies from UAE in relation to the metal content of road-deposited dusts, the current study serves as novel knowledge, especially in the context of geographical areas with a higher occurrence of sandstorms and the presence of particulate matter. The study also adds to the global understanding of the contribution of street dust to environmental pollution and its implications for human health.

Utilizing sludge-based activated carbon for targeted leachate mitigation in wastewater treatment.

Activated carbon (AC) based adsorbents derived from waste sludge were utilized to remediate mixed contaminants in wastewater as an integrated waste-to-resource approach promoting a paradigm shift in management of refuse sludge and wastewater. This review specifically focuses on the remediation of constituents of landfill leachate by sludge-based activated carbon (SBAC). The adsorption effectiveness of SBAC for the exclusion of leachate characters including heavy metals, phenols, dyes, phosphates, and phosphorus were explored with regard to modifiers such as pH, temperature, properties of the adsorbent including functional groups, initial doses of absorbent and adsorbate, and duration of exposure to note the impact of each parameter on the efficiency of adsorption of the sludge adsorbent. Through the works of various researchers, it was noted that the properties of the adsorbent, pH and temperature impact the working of SBACs. The pH of the adsorbent by influencing the functional groups. Temperature was expected to have a paramount effect on the adsorption efficiency of the SBACs. The importance of the regeneration and recycling of the adsorbents as well as their leachability is highlighted. Sludge based activated carbon is recommended as a timely, resource-efficient, and sustainable approach for the remediation of wastewater.

Adsorption of Eosin B from Wastewater onto the Prepared Porous Anion Exchange Membrane.

This research describes the fabrication of the porous trimethylamine (TMA)-grafted anion exchange membrane (AEM) over a phase inversion process. The synthesis of the generated AEM was verified using Fourier transform infrared (FTIR) spectroscopy. The fabricated porous AEM showed 240% water uptake (WR), 1.45 mg/g ion exchange capacity (IEC), and a 9.0% linear expansion ratio (LER) at 25 °C. It exhibited a porous structure and higher thermal stability. It was utilized to remove eosin B (EB) from wastewater via the process of adsorption. The adsorption capacity of EB increased with time and the starting concentration of EB while decreasing with temperature and the AEM dosage. Adsorption isotherm investigation results showed that EB adsorption onto the porous AEM followed the Langmuir isotherm because the value of correlation coefficient (R2 = 0.992) was close to unity. Because the correlation coefficient was close to one, it was determined through adsorption kinetic experiments that the adsorption of EB on the produced porous AEM was suitable for a pseudo-second-order model. Thermodynamic study about process of EB adsorption on the porous AEM revealed that there was an exothermic (ΔH° = -16.60 kJ/mol) and spontaneous process.

Isotherms, kinetics and thermodynamic mechanism of methylene blue dye adsorption on synthesized activated carbon.

The treatment of methylene blue (MB) dye wastewater through the adsorption process has been a subject of extensive research. However, a comprehensive understanding of the thermodynamic aspects of dye solution adsorption is lacking. Previous studies have primarily focused on enhancing the adsorption capacity of methylene blue dye. This study aimed to develop an environmentally friendly and cost-effective method for treating methylene blue dye wastewater and to gain insights into the thermodynamics and kinetics of the adsorption process for optimization. An adsorbent with selective methylene blue dye adsorption capabilities was synthesized using rice straw as the precursor. Experimental studies were conducted to investigate the adsorption isotherms and models under various process conditions, aiming to bridge gaps in previous research and enhance the understanding of adsorption mechanisms. Several adsorption isotherm models, including Langmuir, Temkin, Freundlich, and Langmuir-Freundlich, were applied to theoretically describe the adsorption mechanism. Equilibrium thermodynamic results demonstrated that the calculated equilibrium adsorption capacity (qe) aligned well with the experimentally obtained data. These findings of the study provide valuable insights into the thermodynamics and kinetics of methylene blue dye adsorption, with potential applications beyond this specific dye type. The utilization of rice straw as an adsorbent material presents a novel and cost-effective approach for MB dye removal from wastewater.

Smart optical sensing of multiple antibiotic residues from wastewater effluents with ensured specificity using SERS assisted with multivariate analysis.

Surface-enhanced Raman spectroscopy offers great potential for rapid and highly sensitive detection of pharmaceuticals from environmental sources. Herein, we investigated the feasibility of label-free sensing of antibiotic residues from wastewater effluents with high specificity by combining with multivariate analysis. Highly ordered silver nanoarrays with ∼34 nm roughness have been fabricated using a cost-effective electroless deposition technique. As-fabricated Ag arrays showed superior LSPR effects with an enhancement factor of 8 × 107. Excellent reproducibility has also been noticed with RSD values within 11%, whilst the sensor showed good stability and reusability characteristics for being used as a low-cost and reusable sensor. SERS studies demonstrated that antibiotics-spiked wastewater effluents can be detected with high efficiency in a label-free method. The molecular fingerprint bands of antibiotics such as sulfamethoxazole, sulfadiazine, and ciprofloxacin were well analyzed in effluent, tap, and deionized water. It has been found that antibiotics can be detected near picomolar levels; meanwhile, liquid chromatography-mass spectrometry (LC-MS) exhibited a detection limit within nanomolar concentrations only. Furthermore, the specificity of SERS sensing has been further analyzed using a multivariate analysis method, principal component analysis followed by linear discriminant analysis (PCA-LDA); which showed prominent discrimination to distinguish each antibiotic residue from wastewater effluents. The current study presented the potential of Ag nanoarray sensors for rapid, highly specific, and cost-effective analysis of pharmaceutical products for environmental remediation applications.

Occurrence, spatial and seasonal variations of emerging contaminants in the aquatic environment of Sharjah, United Arab Emirates.

The occurrence, seasonal variations and spatial distribution of emerging contaminants (ECs) in wastewater effluents from wastewater treatment plant (WWTP) and UAE's receiving coastal aquatic environment (seawater and sediments) were evaluated in the present study. A total of 21, 23, and 22 contaminants in the effluents, seawater, and sediments, respectively, at concentrations ranging from low ng L-1 up to 1782 ng L-1 in effluents, from low ng/l up to 236.10 ng L-1 in seawater, and from low ng g-1 up to 60.15 ng g-1 in sediments were recorded. The study revealed that imidacloprid, thiabendazole, and acetaminophen were the most ubiquitous compounds in effluents, seawater, and sediments, respectively, since they were found in all samples collected with a detection frequency of 100%. The study also revealed that the higher concentrations of most contaminants were recorded in autumn. However, thiabendazole in effluents and seawater, acetamiprid in effluents, and sulphapyridine in seawater and sediments showed a higher load in winter. This study highlights the need for proper monitoring and management of ECs in wastewater effluents, seawater, and sediments, especially during the autumn and winter seasons, to minimize their impact on the marine ecosystem and public health.

Novel composites of activated carbon and layered double oxide for the removal of sulfate from synthetic and brackish groundwater.

Sulfate (SO42-) is a major water and environmental concern that causes severe diarrhea, death of invertebrates and plant species, and clogging of industrial pipes. In the current work, treatment of SO42- from synthetic and real groundwater having 3901 mg(SO42-)/L was investigated for the first time using Zn-Al and Mg-Al layered double oxides doped granular activated carbon (GAC/Mg-Al LDO and GAC/Zn-Al LDO). The co-precipitation method was followed to synthesize the GAC/LDO composites using an Mg or Zn to Al molar ratio of 3:1. The GAC/Mg-Al LDO possessed a higher specific surface area (323.9 m2/g) compared to GAC/Zn-Al LDO (195.1 m2/g). The GAC/Mg-Al LDO demonstrated more than 99% removal of SO42- from synthetic water, while it was 50.9% for GAC/Zn-Al LDO and less than 1% for raw GAC at an initial concentration of 50 mg/L. The GAC/Mg-Al LDO was selected for further batch experiments and modeling investigation. The equilibrium data followed the Redlich-Peterson and Langmuir models with determination coefficients of 0.943 and 0.935, respectively. The maximum Langmuir adsorption capacity was 143.5 mg/g. In the real groundwater adsorption study, the screening experiment revealed high selectivity towards SO42- with 62% removal efficiency. The optimum dosage was found to be 50 g/L with an uptake capacity of 61.5 mg/g. The kinetic data of SO42- removal from synthetic and brackish water were in excellent agreement with the pseudo-second order model, and the equilibrium was attained in 5 h. Accordingly, it can be concluded that the GAC/Mg-Al LDO is an efficient material for treating SO42- from real groundwater and can be utilized as a pretreatment unit for high sulfate water resources.

Design of tropinium-functionalized anion exchange membranes for acid recovery via diffusion dialysis process.

Diffusion dialysis (DD) process utilizing anion exchange membranes (AEMs) is an environmentally-friendly and energy-efficient technology. From acidic wastewater, DD is needed for acid recovery. This research reports the development of a series of dense tropinium-functionalized AEMs via solution casting method. Fourier Infrared transform (FTIR) spectroscopy verified the successful preparation of AEMs. The developed AEMs exhibited a dense morphology, featuring 0.98-2.42 mmol/g of ion exchange capacity (IEC), 30-81% of water uptake (WR) and 7-32% of linear swelling ratio (LSR). They displayed exceptional mechanical, thermal and chemical stability and were employed for acid waste treatment from HCl/FeCl2 mixtures via DD process. AEMs possessed 20 to 59 (10-3 m/h) and 166 to 362 of acid diffusion dialysis coefficient (UH+) and separation factor (S) respectively at 25 °C. Compared to DF-120 commercial membrane (UH+ = 0.004 m/h, S = 24.3), their DD efficiency was improved under identical experimental conditions.

Correction to "Adsorption of Methyl Orange from an Aqueous Solution onto a BPPO-Based Anion Exchange Membrane".

[This corrects the article DOI: 10.1021/acsomega.2c03148.].

Application of QPPO/PVA based commercial anion exchange membrane as an outstanding adsorbent for the removal of Eosin-B dye from wastewaters.

Commercially available QPPO/PVA based anion exchange membrane (AEM) BIII was to inquire the percentage discharge of anionic dye Eosin-B (EB) at terrain temperature from wastewater. The impact of EB initial concentration, membrane dosage, ionic strength, contact time and temperature on EB percentage removal was contemplated. The EB percentage removal was increased from 22 to 99.56% and 38.15-99.56% with contact time and membrane dosage respectively while decreased from 99.56 to 29%, 99.56 to 54.61% and 99.56 to 92.22% with enhancing initial concentration of EB, ionic strength and temperature respectively. Nonlinear isotherm models were utilized to demonstrate EB adsorption onto AEM BIII. Attained results exhibited that nonliner Freundlich isotherm model best fitted to EB adsorption onto AEM BIII. For EB adsorption onto AEM BIII, adsorption kinetics were inquired in detail by using several kinetic models but EB adsorption nicely fitted to pseudo-second-order kinetics. Similarly thermodynamic analysis was performed and results pointed to an exothermic adsorption of EB onto AEM BIII. The membrane could be reused for four concecutive cycles with loosing its efficiency.

Molecularly imprinted ormosil as a sorbent for targeted dispersive solid phase micro extraction of pyriproxyfen from strawberry samples.

Novel molecularly imprinted organically modified silica was prepared by reacting acrylamide and 3-(tri-methoxysilyl) propyl methacrylate followed by condensation and hydrolysis with tetraethyl ortho-silicate for the determination of pyriproxyfen. The sorbent proved to be highly selective for the template molecule, pyriproxyfen. The characterization of sorbent was carried out using SEM, BET and TGA. The prominent peaks in FTIR at 3700 cm-1 and 1071 cm-1 confirmed the stretching of amide group's N-H and Si-O-Si bond linkage of MIOrmosil. The pseudo-first-order model (R2 0.99) described the adsorption kinetics of the MIOrmosil, whereas among adsorption isotherms, Freundlich model showed the best fit (R2 0.99). The molecularly imprinted silica was applied for the determination of target analytes from strawberries sample using dispersive solid-phase micro extraction (DSPME) followed by high-performance liquid chromatography (HPLC). The LOD (4.93 x10-5 µg mL-1) and LOQ (1.49 x10-4 µg m-1) values were calculated by signal to noise ratio through HPLC. Results show that the maximum binding capacity and percentage recovery values of MIOrmosil were 13 mg g-1 (n = 5) and 97.3% respectively.

Oxidized carbide-derived carbon as a novel filler for improved antifouling characteristics and permeate flux of hybrid polyethersulfone ultrafiltration membranes.

Polyethersulfone (PES) is a widely used polymer for ultrafiltration (UF) membrane fabrication. In the current study, carbide-derived carbon (CDC) oxidized by acid treatment was utilized as a filler to fabricate a novel PES composites UF membranes. The successful oxidation of CDC was validated from presence of oxygen containing functional groups and improved oxygen content, from 5.08 at.% for CDC to 26.22 at.% for oxidized CDC (OCDC). The OCDC PES UF membranes were prepared at different loadings of OCDC between 0.5 and 3.0 wt%. The membrane porosity, pore size and surface free energy found to be improved while a noticeable reduction in water contact angle was observed with OCDC loading implying the improved hydrophilicity of PES membranes. Consequently, the pure water flux found to improve from 151.6 to 569.6 (L/(m2. h)) for the 3.0 wt% modified OCDC membrane (M-3) which is 3.8 folds of the bare PES membrane. The antifouling characteristics were evaluated by humic acid (HA) filtration. The results revealed a significant enhancement in HA rejection with OCDC loading, the highest rejection was 96.8% for M-3 membrane. Additionally, the adsorption capacity of OCDC modified membranes found to decrease with OCDC loading indicating improved rejection of HA from the membrane surface. Moreover, M-3 demonstrated the maximum flux recovery ratio (FRR) of 92.3%. Reusability of the fabricated membranes was evaluated by deionized water/humic acid cycling filtration. The FRR was higher than 86.7% over three cycles of pure water/HA filtration for 140 min, indicated the excellent stability and reusability of the membranes. Overall, the OCDC was an effective filler for enhancing the PES UF membranes antifouling and permeability properties.

An eco-friendly approach on green synthesis, bio-engineering applications, and future outlook of ZnO nanomaterial: A critical review.

Synthesizing ZnO nanostructures ranging from 1 nm to 4 nm confines the electron cloud and exhibits a quantum effect generally called as quantum confinement effect attracting many researchers in the field of electronics and optics. ZnO nanostructures are used in medical applications to formulate antioxidant, antibacterial, antifungal, anti-inflammatory, wound healing, and anti-diabetic medications. This work is a comprehensive study of green synthesis of ZnO nanomaterials using different biological sources and highlights different processes able to produce nanostructures including nanowires, nanorods, nanotubes and other nano shapes of ZnO nanostructures. Different properties of ZnO nanostructures and their targeted bioengineering applications are also described. The strategies and challenges of the eco-friendly approach to enhance the application span of ZnO nanomaterials are also summarized, with future prospects for greener design of ZnO nanomaterials are also suggested.

Tumor micro-environment sensitive release of doxorubicin through chitosan based polymeric nanoparticles: An in-vitro study.

Conventional chemotherapy poses toxic effects to healthy tissues. A therapeutic system is thus required that can administer, distribute, metabolize, and excrete medicine from human body without damaging healthy cells. This is possible by designing a therapeutic system that can release drug at specific target tissue. In current work, novel chitosan (CS) based polymeric nanoparticles (PNPs) containing N-isopropyl acrylamide (NIPAAM) and 2-(di-isopropyl amino) ethyl methacrylate (DPA) are designed. The presence of available functional groups i.e. OH- (3262 cm-1), -NH2 (1542 cm-1), and CO (1642 cm-1), was confirmed by Fourier Transform Infra-red Spectrophotometry (FTIR). The surface morphology and average particle size (175 nm) was determined through Scanning Electron Microscope (SEM). X-Ray Diffractometry (XRD) studies confirmed the amorphous nature and excellent thermal stability of PNPs up to 100 °C with only 2.69% mass loss was confirmed by Thermogravimetric analysis (TGA). The pH sensitivity of such PNPs for release of encapsulated doxorubicin at malignant site was investigated. The encapsulation efficiency of PNPs was 89% (4.45 mg/5 mg) for doxorubicin (a chemotherapeutic) measured by using UV-Vis Spectrophotometer. The drug release profile of loaded PNPs was 88% (3.92 mg/4.45 mg) at pH 5.3, in 96 h. PNPs with varying DPA concentration can effectively be used to deliver chemotherapeutic agents with high efficacy.

Experimental design by response surface methodology for efficient cefixime uptake from hospital effluents using anion exchange membrane.

The excessive use of antibiotics and their ultimate routes to the environment have prompted the drug resistance, which is becoming a major ecological issue. In this work, we have evaluated the performance of quaternary ammonium poly (2, 6-dimethyl-1,4-phenylene oxide) and polyvinyl alcohol (QPPO/PVA) based anion exchange membrane against cefixime (a third generation cephalosporin antibiotic) present in hospital effluents. The membrane's surface morphology was studied through scanning electron microscopy. The optimization of experimental parameters through Response Surface Methodology helped to evaluate the inter parameter dependence and predict maximum uptake capacity (qe). The speculated value of qe (6.72 mg g-1) obtained through central composite design was close to the experimental value of 7.01 mg g-1 with percent relative error of 4.31%. Further, the evaluation of experimental data using isotherms (Langmuir and Freundlich) and kinetic models (pseudo-first-order and second-order) proposed that the interactions between cefixime and the membrane were physisorptive in nature. The intra-day and inter-day assays exhibited lower %RSD values of 0.4% (n = 5) and 0.3% (n = 5). Furthermore, a percentage recovery of 98.2% (n = 9) and limit of detection 1 × 10-5 µg mL-1 was observed. The chromatogram of the treated water samples presented only negligible amount of cefixime indicating a great potential of QPPO/PVA membrane for the removal of cefixime from real water samples. The membrane could be regenerated for three consecutive cycles without any prominent loss in efficiency.

Tailoring Vanadium-Based Magnetic Catalyst by In Situ Encapsulation of Tungsten Disulfide and Applications in Abatement of Multiple Pollutants.

A magnetic nanocomposite of tungsten and vanadium was employed as a catalyst for the mitigation of water contaminants, including a carcinogenic dye (Congo red, CR), a widely used pesticide (glyphosate), and the bacterial strain Escherichia coli. Additionally, it was subjected to several characterization techniques. X-ray diffraction spectroscopy examination validated the synthesized nanoparticles' crystalline nature, and scanning electron microscopy and energy-dispersive X-ray analysis were employed to examine the morphology and elemental composition of the catalyst. The use of thermogravimetric analysis enabled the elaboration of the thermal behavior of tungsten sulfide-vanadium decorated with Fe2O3 nanoparticles. The experiments were conducted under visible light conditions. The highest levels of photodegradation of 96.24 ± 2.5% for CR and 98 ± 1.8% for glyphosate were observed following a 180 min exposure to visible light at pH values of 6 and 8, respectively. The quantum yields for CR and Gly were calculated to be 9.2 × 10-3 and 4.9 × 10-4 molecules photon-1, respectively. The findings from the scavenger analysis suggest the involvement of hydroxyl radicals in the degradation mechanism. The study evaluated the inhibition of E. coli growth when exposed to a concentration of 0.1 g/10 mL of the photocatalyst, utilizing a 1 mL sample of the bacterial strain. The successful elimination of CR and glyphosate from water-based solutions, along with the subsequent antibacterial experiments, has substantiated the efficacy of the photocatalyst in the field of environmental remediation.

A Comparative Analysis of the Effect of Carbonaceous Nanoparticles on the Physicochemical Properties of Hybrid Polyethersulfone Ultrafiltration Membranes.

Numerous studies have been previously reported on the use of nanoscale carbonaceous fillers, such as multi-walled carbon nanotubes (MWCNTs) and graphene oxide (GO), in polymeric ultrafiltration (UF) membranes; however, no insight has been clearly reported on which material provides the best enhancements in membrane performance. In this study, a comparative analysis was carried out to establish a comprehensible understanding of the physicochemical properties of hybrid polyethersulfone (PES) UF membranes incorporated with MWCNTs and GO nanoparticles at various concentrations. The hybrid membranes were prepared via the non-solvent-induced phase separation process and further characterized by field emission scanning electron microscopy and atomic force microscope (AFM). The AFM images showed homogeneous membrane surfaces with a reduction in the membrane surface roughness from 2.62 nm for bare PES to 2.39 nm for PES/MWCNTs and to 1.68 nm for PES/GO membranes due to improved hydrophilicity of the membranes. Physicochemical properties of the hybrid PES membranes were assessed, and the outcomes showed an enhancement in the porosity, pore size, water contact angle, and water permeability with respect to nanoparticle concentration. GO-incorporated PES membranes exhibited the highest porosity, pore size, and lowest contact angle as compared to PES/MWCNTs, indicating the homogeneous distribution of nanoparticles within the membrane structure. PES/MWCNTs (0.5 wt.%) and PES/GO (1.0 wt.%) hybrid membranes exhibited the highest water flux of 450.0 and 554.8 L m-2 h-1, respectively, at an applied operating pressure of 1 bar. The filtration and antifouling performance of the PES hybrid membranes were evaluated using 50 mg L-1 of humic acid (HA) as a foulant at pH = 7. Compared to the bare PES membrane, the MWCNTs and GO-incorporated PES hybrid membranes exhibited enhanced permeability and HA removal. Moreover, PES/MWCNTs (0.5 wt.%) and PES/GO (1 wt.%) hybrid membranes reported HA rejection of 90.8% and 94.8%, respectively. The abundant oxygen-containing functional groups in GO-incorporated PES membranes resulted in more hydrophilic membranes, leading to enhanced permeability and fouling resistance. The antifouling properties and flux recovery ratio were improved by the addition of both nanoparticles. Given these findings, although both MWCNTs and GO nanoparticles are seen to notably improve the membrane performance, PES membranes with 1 wt.% GO loading provided the highest removal of natural organic matter, such as HA, under the same experimental conditions.

Molecularly Imprinted Polymeric Sorbent for Targeted Dispersive Solid-Phase Microextraction of Fipronil from Milk Samples.

Fipronil, a phenyl pyrazole insecticide, is extensively used in agriculture to control insect infestation. It has the potential to assimilate into the food chain, leading to serious health concerns. We report molecularly imprinted polymer (MIP)-based dispersive solid-phase microextraction for the targeted determination of fipronil in milk samples. Designing such a sorbent is of paramount importance for measuring the accurate amount of fipronil for monitoring its permissible limit. Response surface methodology based on a central composite design following a face-centered approach was used to optimize experimental conditions. The maximum binding capacity of 47 mg g-1 was achieved at optimal parameters of time (18 min), temperature (42 °C), pH (7), and analyte concentration (120 mg L-1). Under these conditions, a high percentage recovery of 94.6 ± 1.90% (n = 9) and a low limit of detection (LOD) and limit of quantitation (LOQ) (5.64 × 10-6 and 1.71 × 10-5 µg mL-1, respectively) were obtained. The MIP was well characterized through a scanning electron microscope (SEM) as well as Brunauer-Emmett-Teller (BET), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA) methods. Adsorption kinetics of the MIP followed the pseudo-first-order model (R 2 0.99 and χ2 0.96), suggesting the MIP-analyte interaction to be a physiosorptive process, while adsorption isotherms followed the Freundlich model (R 2 0.99). The real sample analysis through high-performance liquid chromatography (HPLC) confirmed the selective determination of fipronil from milk samples.

Effects of the COVID-19 lockdown and recovery on People's mobility and air quality in the United Arab Emirates using satellite and ground observations.

The stringent COVID-19 lockdown measures in 2020 significantly impacted people's mobility and air quality worldwide. This study presents an assessment of the impacts of the lockdown and the subsequent reopening on air quality and people's mobility in the United Arab Emirates (UAE). Google's community mobility reports and UAE's government lockdown measures were used to assess the changes in the mobility patterns. Time-series and statistical analyses of various air pollutants levels (NO2, O3, SO2, PM10, and aerosol optical depth-AOD) obtained from satellite images and ground monitoring stations were used to assess air quality. The levels of pollutants during the initial lockdown (March to June 2020) and the subsequent gradual reopening in 2020 and 2021 were compared with their average levels during 2015-2019. During the lockdown, people's mobility in the workplace, parks, shops and pharmacies, transit stations, and retail and recreation sectors decreased by about 34%-79%. However, the mobility in the residential sector increased by up to 29%. The satellite-based data indicated significant reductions in NO2 (up to 22%), SO2 (up to 17%), and AOD (up to 40%) with small changes in O3 (up to 5%) during the lockdown. Similarly, data from the ground monitoring stations showed significant reductions in NO2 (49% - 57%) and PM10 (19% - 64%); however, the SO2 and O3 levels showed inconsistent trends. The ground and satellite-based air quality levels were positively correlated for NO2, PM10, and AOD. The data also demonstrated significant correlations between the mobility and NO2 and AOD levels during the lockdown and recovery periods. The study documents the impacts of the lockdown on people's mobility and air quality and provides useful data and analyses for researchers, planners, and policymakers relevant to managing risk, mobility, and air quality.