Masks As a New Hotspot for Antibiotic Resistance Gene Spread: Reveal the Contribution of Atmospheric Pollutants and Potential Risks.

The consumption of disposable surgical masks (DSMs) considerably increased during the coronavirus pandemic in 2019. Herein, we explored the spread of antibiotic resistance genes (ARGs) and the potential risks of antibiotic resistant bacteria (ARB) on DSMs. At environmentally relevant concentrations, the conjugate transfer frequency (CTF) of ARGs increased by 1.34-2.37 folds by 20 µg/m3 of atmospheric water-soluble inorganic ions (WSIIs), and it increased by 2.62-2.86 folds by 80 ng/m3 of polycyclic aromatic hydrocarbons (PAHs). Total suspended particulates (TSP) further promoted the CTF in combination with WSIIs or PAHs. Under WSII and PAH exposure, gene expression levels related to oxidative stress, cell membrane, and the adenosine triphosphate (ATP) were upregulated. WSIIs predominantly induced cellular contact, while PAHs triggered ATP formation and membrane damage. Molecular dynamics simulations showed that WSIIs and PAHs reduced membrane lipid fluidity and increased membrane permeability through interactions with the phosphatidylcholine bilayer. DSM filtering performance decreased, and the CTF of ARGs increased with the wearing time. The gut simulator test showed that ARB disrupted the human gut microbial community and increased total ARG abundance but did not change the ARG abundance carried by ARB themselves. A mathematical model showed that long-term WSII and PAH exposure accelerated ARG dissemination in DSMs.

Tyrosine nitration enhances the allergenic potential of house dust mite allergen Der p 2.

Nitration of allergenic proteins caused by atmospheric pollutants O3 and NO2 may enhance their allergenic potential. In the study, the influence of nitration was investigated on the allergenicity of Der p 2, which is a main allergen from house dust mites and plays an important role in allergenic rhinitis and asthma. The results reveal that nitrated Der p 2 enhanced the IgE-binding capacity, upregulated the mRNA expression and release of IL-6 and IL-8 from bronchial epithelial cells, and induced higher levels of specific-IgE, TH2 cytokines and white blood cells in mice. Besides, nitrated Der p 2 caused more severe oxidative stress and allergenic symptoms in mice. It is concluded that nitration enhanced the allergenicity of Der p 2 through not only directly inducing higher amount of specific-IgE and stronger responses of TH2 cytokines, but also indirectly aggravating allergic symptoms by oxidative stress and adjuvant-like activation airway epithelial cells. The study suggests that the contribution of nitration to the promotion in allergenicity should not be ignored when precisely assessing the risk of house dust mite allergens in real environment.

Assessing Tunisia's urban air quality using combined lichens and Sentinel-5 satellite integration.

In Tunisia, urban air pollution is becoming a bigger problem. This study used a combined strategy of biomonitoring with lichens and satellite mapping with Sentinel-5 satellite data processed in Google Earth Engine (GEE) to assess the air quality over metropolitan Tunis. Lichen diversity was surveyed across the green spaces of the Faculty of Science of Tunisia sites, revealing 15 species with a predominance of pollution-tolerant genera. The Index of Atmospheric Purity (IAP) calculated from the lichen data indicated poor air quality. Spatial patterns of pollutants sulfur dioxide (SO2), ozone (O3), nitrogen dioxide (NO2), carbon monoxide (CO), and aerosol index across Greater Tunis were analyzed from Sentinel-5 datasets on the GEE platform. The higher values of these indices in the research area indicate that it may be impacted by industrial activity and highlight the considerable role that vehicle traffic plays in air pollution. The results of the IAP, IBL, and the combined ground-based biomonitoring and satellite mapping techniques confirm poor air quality and an environment affected by atmospheric pollutants which will enable proactive air quality management strategies to be put in place in Tunisia's rapidly expanding cities.

Gas Sensing and Half-Metallic Materials Design Using Metal Embedded into S Vacancies in WS2 Monolayers: Adsorption of NO, CO, and O2 Molecules.

The adsorption of CO, NO, and O2 molecules onto Cu, Ag, and Au atoms placed in the S vacancies of a WS2 monolayer was elucidated within dispersion-corrected density functional theory. The binding energies computed for embedded defects into S vacancies were 2.99 (AuS), 2.44 (AgS), 3.32 eV (CuS), 3.23 (Au2S2), 2.55 (Ag2S2), and 3.48 eV/atom (Cu2S2), respectively. The calculated diffusion energy barriers from an S vacancy to a nearby site for Cu, Ag, and Au were 2.29, 2.18, and 2.16 eV, respectively. Thus, the substitutional atoms remained firmly fixed at temperatures above 700 K. Similarly, the adsorption energies showed that nitric oxide and carbon oxide molecules exhibited stronger chemisorption than O2 molecules on any of the metal atoms (Au, Cu, or Ag) placed in the S vacancies of the WS2 monolayer. Therefore, the adsorption of O2 did not compete with NO or CO adsorption and did not displace them. The density of states showed that a WS2 monolayer modified with a Cu, Au, or Ag atom could be used to design sensing devices, based on electronic or magnetic properties, for atmospheric pollutants. More interestingly, the adsorption of CO changed only the electronic properties of the MoS2-AuS monolayer, which could be used for sensing applications. In contrast, the O2 molecule was chemisorbed more strongly than CO or NO on Au2S2, Cu2S2, or Ag2S2 placed into di-S vacancies. Thus, if the experimental system is exposed to air, the low quantities of O2 molecules present should result in the oxidation of the metallic atoms. Furthermore, the O2 molecules adsorbed on WS2-Au2S2 and WS2-CuS introduced a half-metallic behavior, making the system suitable for applications in spintronics.

Needle age and precipitation as drivers of Hg accumulation and deposition in coniferous forests from a southwestern European Atlantic region.

Vegetation and climate are critical in the biogeochemical cycle of Hg in forest ecosystems. The study assesses the influence of needle age and precipitation on the accumulation of Hg in needle biomass and its deposition by litterfall in thirty-one pine plantations spread throughout two biogeographical regions in SW Europe. Well-developed branches of Pinus pinaster were sampled and pine needles were classified according to 4 age classes (y0, y1, y2, y3). The concentration of total Hg (THg) was analyzed in the samples and Hg content in needle biomass and its deposition by litterfall were estimated. The concentration of total Hg (THg) increased with needle age ranging from 9.1 to 32.7 µg Hg kg-1 in the youngest and oldest needles, respectively. The rate of Hg uptake (HgR) three years after needle sprouting was 10.2 ± 2.3 µg Hg kg-1 yr-1, but it decreased with needle age probably due to a diminution in photosynthetic activity as needles get older. The average total Hg stored in needle biomass (HgWt) ranged from 5.6 to 87.8 mg Hg ha-1, with intermediate needle age classes (y1 and y2) accounting for 70% of the total Hg stored in the whole needle biomass. The average deposition flux of Hg through needle litterfall (HgLt) was 1.5 µg Hg m-2 yr-1, with the y2 and y3 needles contributing most to the total Hg flux. The spatial variation of THg, HgWt and HgLt decreased from coastal pine stands, characterized by an oceanic climate, to inland pine stands, a feature closely related to the dominant precipitation regime in the study area. Climatic conditions and needle age are the main factors affecting Hg accumulation in tree foliage, and should be considered for an accurate assessment of forest Hg pools at a regional scale and their potential consequences in the functioning of terrestrial ecosystems.

Evaluation of Coriolis Micro Air Sampling to Detect Volatile and Semi-Volatile Organic Compounds.

There are several analytical procedures available for the monitoring of volatile organic compounds (VOCs) in the air, which differ mainly on sampling procedures. The Coriolis micro air sampler is a tool normally designed for biological air sampling. In this paper, the Coriolis micro bio collector is used to evaluate its ability to sample organic contaminants sampling and detecting them when combined GC-MS. We also compare the use of the Coriolis micro with a standardized sampling method, which is the use of a lung box with a Nalophan® bag. The results show that the Coriolis micro sampling method is suitable for the sampling of organic contaminants. Indeed, the Coriolis micro allows to sample and detect mainly semi-volatile molecules, while the lung box/Nalophan® bags allow to sample more volatile molecules (highly volatile and volatile). These results were confirmed in the controlled air lab with a slight difference with the field. The simultaneous use of the both techniques allow to sample and detect a larger number of molecules with specific physicochemical properties to each sampling technique. In conclusion, the Coriolis micro can sample and detect volatile organic compounds present in air. We have shown that the development of alternative sampling methods and the use of non-target analysis are essential for a more comprehensive risk assessment. Moreover, the use of the Coriolis micro allows the detection of emergent molecules around the Thau lagoon.

Spatial patterns and temporal variations of pollutants at 56 air quality monitoring stations in the state of São Paulo, Brazil.

This study applied two data mining tasks: clustering and association rules to a dataset of pollutants in the state of São Paulo. The clustering task was applied to temporal patterns and geospatial distributions of pollutants, and the association rules were used to identify prevailing meteorological conditions when there were high concentrations of pollutants from 2017 to 2019. The results indicated good adequacy of the cluster, indicating different pollution levels per group, with a silhouette coefficient from 0.26 to 0.72. In the spatial evaluation, the groups severely polluted were located in the metropolitan region, on the coast and, some inland cities, by industrial, vehicular, burning, agriculture, and other emissions. The cluster identified a strong presence of O3 and PM2.5 in 65% and 72% of the monitored stations in several areas of the state. As for the distance between the sources of pollution, the groups of PM10 and NO2 were geographically distant, while PM2.5, CO, SO2, and O3 were closer, suggesting a spatial relationship of exposure. Seasonality was similar between groups, with significantly higher concentrations in winter, except for O3, for which higher concentrations occurred in summer. Meteorological conditions contributed to critical episodes of pollution (support and confidence greater than 80%), with low temperature and humidity, low rainfall, and milder wind associated with increased pollutants. In conclusion, investigating spatial representativeness allows revealing spatial and temporal patterns of pollutants and unfavorable meteorological conditions to diffusion. Thus, ideal and effective measures can be taken to avoid critical periods of exposure based on the behavior of pollutants in different regions and related climate changes.

Diurnal and Seasonal Variation of Atmospheric Particulate Matter and Trace Gases in Industrial Area of Delhi: A Study.

The diurnal and seasonal variation of PM10, SO2, NO2, NH3 and water-soluble compounds were studied in Naraina industrial area; Delhi from January to December, 2017. It was observed that annual average concentrations of PM10, SO2, NO2, NH3, SO42-, NO3-, NH4+,Na+, K+, Ca2+, Mg2+, Cl- and F- in the day time were 227 ± 91, 9 ± 5, 59 ± 22, 65 ± 15, 17.45 ± 5.14, 17.60 ± 4.94, 8.66 ± 2.94, 4.05 ± 1.08, 3.46 ± 0.91, 10.38 ± 4.48, 3.15 ± 0.99, 43.06 ± 5.20 and 0.50 ± 0.12 µg m-3, respectively and night time were 320 ± 127, 14 ± 7, 82 ± 25, 83 ± 20, 22.64 ± 5.22, 21.66 ± 5.0, 11.81 ± 3.47, 3.29 ± 0.87, 3.02 ± 1.19, 7.55 ± 3.16, 2.49 ± 0.95, 31.86 ± 4.70 and 0.37 ± 0.12 µg m-3, respectively. PM10 and sometimes NO2 concentrations exceeded the Indian National Ambient Air Quality Standards. SO2, and NH3 concentrations were within the standard. The selected parameters varied from season to season. In the night time, selected parameters concentrations were high in comparison to day time might be due to formation of inorganic secondary particulate matters and low wind speed in the ambient air.

Ten-year emission characteristics of atmospheric pollutants from incineration of sacrificial offerings in China.

The incineration of sacrificial offerings is a significant widely practiced custom that is also a kind of neglected air pollution source in China. Our results showed that the emission factors of particulate matter, SO2, CO, NOx, and VOCs emitted from the incineration of sacrificial offerings with purification systems were reduced by 95%, 19%, 9%, 82%, and 42%, respectively, compared with those without a purification system, revealing a significant effect of the flue gas purification system on reducing particulate matter and gaseous pollutants. The emission level of air pollutants from the incineration of sacrificial offerings remained stable before 2013 and then showed a remarkable decrease after the implementation of China´s Air Pollution Prevention Action Plan in 2013. The emissions of TSP (total suspended particulate), PM10, PM2.5, and NOx in 2009 were 8222, 6106, 5656 and 15,878 ton, respectively, obviously higher than 3434, 2551, 2305 and 8579 ton in 2019. Such trend was affected by both the quantity of incineration and the installation rate of purification systems after the Emission Standard of Air Pollutants for Crematory (GB 13801-2015) issued in China. Distinct spatial distribution of atmospheric pollutants from incineration of sacrificial offerings was found with higher in the east and south of China than the west and north of China, which is proportional to the regional economy and population. The maximum ground-level concentration typically occurred at 0.12-0.2 km from the pollution source, posing potential health risks to people entering and exiting funeral and burial sites and nearby residents.

Gas-phase catalytic hydration of I2O5 in the polluted coastal regions: Reaction mechanisms and atmospheric implications.

Marine aerosols play an important role in the global aerosol system. In polluted coastal regions, ultra-fine particles have been recognized to be related to iodine-containing species and is more serious due to the impact of atmospheric pollutants. Many previous studies have identified iodine pentoxide (I2O5, IP) to be the key species in new particles formation (NPF) in marine regions, but the role of IP in the polluted coastal atmosphere is far to be fully understood. Considering the high humidity and concentrations of pollutants in the polluted coastal regions, the gas-phase hydration of IP catalyzed by sulfuric acid (SA), nitric acid (NA), dimethylamine (DMA), and ammonia (A) have been investigated at DLPNO-CCSD(T)//ωB97X-D/aug-cc-pVTZ + aug-cc-pVTZ-PP with ECP28MDF (for iodine) level of theory. The results show that the hydration of IP involves a significant energy barrier of 22.33 kcal/mol, while the pollutants SA, NA, DMA, and A all could catalyze the hydration of IP. Especially, with SA and DMA as catalysts, the hydration reactions of IP present extremely low barriers and high rate constants. It is suggested that IP is unstable under the catalysis of SA and DMA to generate iodic acid, which is the key component in NPF in marine regions. Thus, the catalytic hydration of IP is very likely to trigger the formation of iodine-containing particles. Our research provides a clear picture of the catalytic hydration of IP as well as theoretical guidance for NPF in the polluted coastal atmosphere.

Improvement in air quality and its impact on land surface temperature in major urban areas across India during the first lockdown of the pandemic.

The SARS CoV-2 (COVID-19) pandemic and the enforced lockdown have reduced the use of surface and air transportation. This study investigates the impact of the lockdown restrictions in India on atmospheric composition, using Sentinel-5Ps retrievals of tropospheric NO2 concentration and ground-station measurements of NO2 and PM2.5 between March-May in 2019 and 2020. Detailed analysis of the changes to atmospheric composition are carried out over six major urban areas (i.e. Delhi, Mumbai, Kolkata, Chennai, Bangalore, and Hyderabad) by comparing Moderate Resolution Imaging Spectroradiometer (MODIS) Aerosol Optical Depth (AOD) and land surface temperature (LST) measurements in the lockdown year 2020 and pre-lockdown (2015-2019). Satellite-based data showed that NO2 concentration reduced by 18% (Kolkata), 29% (Hyderabad), 32-34% (Chennai, Mumbai, and Bangalore), and 43% (Delhi). Surface-based concentrations of NO2, PM2.5, and AOD also substantially dropped by 32-74%, 10-42%, and 8-34%, respectively over these major cities during the lockdown period and co-located with the intensity of anthropogenic activity. Only a smaller fraction of the reduction of pollutants was associated with meteorological variability. A substantial negative anomaly was found for LST both in the day (-0.16 °C to -1 °C) and night (-0.63 °C to -2.1 °C) across select all cities, which was also consistent with air temperature measurements. The decreases in LST could be associated with a reduction in pollutants, greenhouse gases and water vapor content. Improvement in air quality with lower urban temperatures due to lockdown may be a temporary effect, but it provides a crucial connection among human activities, air pollution, aerosols, radiative flux, and temperature. The lockdown for a shorter-period showed a significant improvement in environmental quality and provides a strong evidence base for larger scale policy implementation to improve air quality.

An investigation of the impacts of a successful COVID-19 response and meteorology on air quality in New Zealand.

The COVID-19 pandemic brought about national restrictions on people's movements, in effect commencing a socially engineered transport emission reduction experiment. In New Zealand during the most restrictive alert level (Level 4), roadside concentrations of nitrogen dioxide (NO2) were reduced 48-54% compared to Business-as-usual (BAU) values. NO2 concentrations rapidly returned to near mean levels as the alert levels decreased and restrictions eased. PM10 and PM2.5 responded differently to NO2 during the different alert levels. This is due to particulates having multiple sources, many of natural origin and therefore less influenced by human activity. PM10 and PM2.5 concentrations were reduced during alert level 4 but to a lesser extent than NO2 and with more variability across regions. Particulate concentrations increased notably during alert level 2 when many airsheds reported concentrations above the BAU means. To provide robust BAU reference concentrations, simple 5-year means were calculated along with predictions from machine learning modelling that, in effect, removed the influence of meteorology on observed concentrations. The results of this study show that latter method was found to be more closely aligned to observed values for NO2 as well as PM2.5 and PM10 away from coastal regions.

New insights into heavy metal elements deposition in the snowpacks of mountain glaciers in the eastern Tibetan Plateau.

Atmospheric heavy metals have important environmental and health threats. To investigate atmospheric deposition and contamination of heavy metal elements in the glaciers of the eastern Tibetan Plateau (ETP), we collected the surface snow (cryoconites) samples in the Lenglongling Glacier (LG), the Gannan Snowpack (GS), the Dagu Glacier (DG), the Hailuogou Glacier (HG) and Yulong Snow-mountain Glacier (YG) in summer 2017. Samples were analyzed for concentrations and enrichment factors (EFs) of Al and trace elements (Pb, Co, Cd, Ba, Mn, Ga, Sc, V, Zn, Cr, Ni, Cu, Rb, Sb, Cs, As, Mo, Li) using inductively coupled plasma-mass spectrometry (ICP-MS). Results showed that the concentrations and EFs of heavy metals (e.g. Sb, Cu, Cr, Ni, As, Mo) were generally high value in YG, GS and LG, while were relatively low value in DG and HG, implying that ETP glaciers may have been affected by atmospheric anthropogenic pollutants deposition to varying degrees. Comparing the heavy metal concentrations in the glaciers with those in the precipitation of middle/eastern China cities and also the South Asian cities, we find that the glacial heavy metal concentrations were generally low level, though the anthropogenic pollutants were still significantly enriched. Taking the spatial distribution of As and Ni concentration/EFs in the glaciers and surrounding urban precipitation as an example, we find that the heavy metal pollutants were probably transported to the glaciers through three routes from the surrounding densely populated area of Asia. The MODIS AOD and NCEP/NCAR wind vector also demonstrated that the atmospheric pollutants originated from anthropogenic emissions of urban areas of both South Asia, and northwest and east China, mainly caused by the large scale atmospheric circulation (e.g. the South Asian Monsoon, westerlies and Eastern Asian Summer Monsoon). Therefore, control of these potential pollution emission sources of the surrounding densely populated areas in Asia could be important to ETP glaciers in future perspectives.

Cladonia verticillaris (lichen) indicates negative impacts derived from the combustion of biodiesel blends: an alert for the environmental management for biofuels use.

The use of biodiesel blends with petroleum diesel in vehicular engines demands the evaluation of the possible impacts and effects of the gases emitted from their combustion on the environment. Among studies on these questions, biomonitoring using lichens is a viable alternative, given their interactions with the elements dispersed in the atmosphere, as well as its sensitivity and capacity to retain contaminants. In this study, we analyzed the effects of gas emissions from the combustion of biodiesel mixture with petroleum diesel on Cladonia verticillaris thalli. Samples of the lichen (10 g) were exposed to the gases emitted by the exhaust of the generator engine during the combustion process of biodiesel mixtures to petroleum diesel (7% (B7), 10% (B10), 40% (B40), 50% (B50), and 70% (B70)). At 90 days after exposure, samples were analyzed for n-alkane profiles, thallus morphology, photosynthetic pigment contents, and secondary lichen metabolites (protocetraric and fumarprotocetraric acids). Sets B7 and B10 showed better resistance of the lichen to pollutants. Set B40 showed a high stress evidenced by the chain elongation of n-alkanes structure and high chlorophyll production, presenting high morphological damages when compared to the control sets, B7 and B10. The results showed significant reductions of n-alkanes profiles for mixtures with high concentrations of biodiesel (B50 and B70), as well as decreases in the chlorophyll content. These groups showed an increase in the synthesis of secondary metabolites, corroborating the hypothesis that high concentrations of biodiesel in the mixture with petroleum diesel have greater impacts on the lichen. Schematic model for demonstration of using the lichen Cladonia verticillaris as biomonitor of effects from gas emissions from the combustion of biodiesel blends with petroleum diesel by a stationary engine.

Occurrence of polar organic compounds in atmospheric particulate matter: a system review in South America.

Particulate matter (PM) is one of the existing air pollutants, which can cause damages to human health, public property, and the environment. The chemical composition of this pollutant greatly varies, mainly its organic fraction. Thus, our objective was to carry out a literature review based on articles, considering studies conducted in South America, whose authors address the characterization of the polar organic fraction of PM. We performed the review using the Scopus, SciELO, and Web of Science databases, considering publications dated from the years 2010 to 2019. A total of 14,575 articles were found, of which only 12 met the predefined selection criteria. According to our research, the most studied compound is levoglucosan, a biomass burning marker belonging to the group of anhydrous sugars. Besides, nitro-PAHs, which usually originate from vehicular sources and are compounds with mutagenic and carcinogenic characteristics, have also been found. Moreover, we concluded that, currently, there are few studies on the subject in South America, requiring more research on polar organic compounds present in PM in countries of this region. These studies are of great importance because some compounds can cause great damage to human health, such as the nitro-PAHs; furthermore, PM may still have unknown compounds that need identification and elucidation of their toxicity.

Mutual relationship between surface atmospheric pollutants and CG lightning in Tehran area.

The mutual relationship between surface atmospheric pollutants and Cloud-to-Ground (CG) lightning is studied in the Tehran area for the first time. The impact of surface pollutant concentration of PM10 on CG lightning initiation, as well as the production of NO2 and surface ozone derived by lightning occurrence is investigated. To proceed, the reports of thunderstorm occurrence, including CG lightning in the Tehran area have been collected for years of study from the Iran meteorological organization (IRIMO). The surface pollution data are obtained from the Air Quality Control Center (AQCC) for several stations in the area of interest. The number of lightning (NoL) associated with the selected dates is obtained using the World Wide Lightning Location Network (WWLLN). The correlation coefficients associated with the CG lightning and the concentrations of PM10, NO2, and surface ozone are calculated. The hourly variations of accumulated NoL and NO2 and surface ozone are also compared for 24 hours before and after the lightning activity for four days of study during the years of 2009-2013. The results show that there is a positive correlation between PM10 concentration and lightning flash number, obtained from observational data of WWLLN. Moreover, the comparison of NoL and surface pollutant concentration indicates a clear positive contribution from CG lightning in NO2 and ozone production. In days with a considerable number of lightning occurrences, the comparison of the hourly average of NO2 and O3 concentrations with the lightning flash number reveals that NO2 decreases, and O3 increases due to the significant increases of lightning strikes.

The Impact of COVID-19 Partial Lockdown on Primary Pollutant Concentrations in the Atmosphere of Rio de Janeiro and São Paulo Megacities (Brazil).

As COVID-19 spread all over the world, most of the countries adopted some kind of restrictions to avoid the collapse of health systems. In Brazil, São Paulo and Rio the Janeiro, the two most populated cities in the country, were the first to determine social distancing. In this study, the impact of the social distancing measures on the concentrations of the three main primary air pollutants (PM10, NO2 and CO) was analyzed. CO levels showed the most significant reductions (up to 100%) since it is related to light-duty vehicular emissions. NO2 also showed reductions (9.1%-41.8%) while PM10 levels were only reduced in the 1st lockdown week. The decrease of pollutants was not directly proportional to the vehicular flux reduction, because it depends on other factors such as the transport of air masses from industrial and rural areas. The differences observed can be explained considering the fleet characteristics in the two cities and the response of the population to the social distancing recommendations.

Influencing factors and prediction of ambient Peroxyacetyl nitrate concentration in Beijing, China.

Peroxyacyl nitrates (PANs) are important secondary pollutants in ground-level atmosphere. Accurate prediction of atmospheric pollutant concentrations is crucial to guide effective precautions for before and during specific pollution events. In this study, four models based on the back-propagation (BP) artificial neural network (ANN) and multiple linear regression (MLR) methods were used to predict the hourly average PAN concentrations at Peking University, Beijing, in 2014. The model inputs were atmospheric pollutant data and meteorological parameters. Model 3 using a BP-ANN based on the original variables achieved the best prediction results among the four models, with a correlation coefficient (R) of 0.7089, mean bias error of -0.0043 ppb, mean absolute error of 0.4836 ppb, root mean squared error of 0.5320 ppb, and Willmott's index of agreement of 0.8214. Based on a comparison of the performance indices of the MLR and BP-ANN models, we concluded that the BP-ANN model was able to capture the highly non-linear relationships between PAN concentration and the conventional atmospheric pollutant and meteorological parameters, providing more accurate results than the traditional MLR models did, with a markedly higher goodness of R. The selected meteorological and atmospheric pollutant parameters described a sufficient amount of PAN variation, and thus provided satisfactory prediction results. More specifically, the BP-ANN model performed very well for capturing the variation pattern when PAN concentrations were low. The findings of this study address some of the existing knowledge gaps in this research field and provide a theoretical basis for future regional air pollution control.

Observations of atmospheric pollutants at Lhasa during 2014-2015: Pollution status and the influence of meteorological factors.

Atmospheric pollutants including SO2, NO2, CO, O3 and inhalable particulate matter (PM2.5 and PM10) were monitored continuously from March 2014 to February 2015 to investigate characteristics of air pollution at Lhasa, Tibetan Plateau. Species exhibited similar seasonal variations except O3, with the peaks in winter but low valleys in summer. The maximum O3 concentration was observed in spring, followed by summer, autumn, and winter. The positive correlation between O3 and PM10 in spring indicated similar sources of them, and was assumed to be turbulent transport. Temperature was the dominant meteorological factor for most species in spring. High temperature accelerates O3 photochemistry, and favors air disturbance which is conductive to dust resuspension in spring. Relative humidity (RH) and atmospheric pressure were the main meteorological factors in summer. RH showed negative correlations with species, while atmospheric pressure posed opposite situation. Wind speed (WS) was the dominant meteorological factor in autumn, the negative correlations between WS and species indicated diffusion by wind. Most species showed non-significant correlations with meteorological factors in winter, indicating the dependence of pollution on source emission rather than restriction by meteorology. Pollution weather character indicated that emissions were from biomass burning and dust suspension, and meteorological factors also played an important role. Air stream injection from the stratosphere was observed during O3 pollution period. Air parcels from Southwest Asia were observed during air pollution period in winter. An enhancement in air pollutants such as O3 would be expected in the future, more attention should be given to countermeasures for prevention of air pollution in the future.

Air contaminants and litter fall decomposition in urban forest areas: The case of São Paulo - SP, Brazil.

BACKGROUND: Urban forests are usually affected by several types of atmospheric contaminants and by abnormal variations in weather conditions, thus facilitating the biotic homogenization and modification of ecosystem processes, such as nutrient cycling. Peri-urban forests and even natural forests that surround metropolitan areas are also subject to anthropogenic effects generated by cities, which may compromise the dynamics of these ecosystems. Hence, this study advances the hypothesis that the forests located at the margins of the Metropolitan Region of São Paulo (MRSP), Brazil, have high concentrations of atmospheric contaminants leading to adverse effects on litter fall stock. METHODS: The production, stock and decomposition of litter fall in two forests were quantified. The first, known as Guarapiranga forest, lies closer to the urban area and is located within the MRSP, approximately 20km from the city center. The second, Curucutu forest, is located 70km from the urban center. This forest is situated exactly on the border of the largest continuum of vegetation of the Atlantic Forest. To verify the reach of atmospheric pollutants from the urban area, levels of heavy metals (Cd, Pb, Ni, Cu) adsorbed on the litter fall deposited on the soil surface of the forests were also quantified. RESULTS: The stock of litter fall and the levels of heavy metals were generally higher in the Guarapiranga forest in the samples collected during the lower rainfall season (dry season). Non-metric multidimensional scaling multivariate analysis showed a clear distinction of the sample units related to the concentrations of heavy metals in each forest. A subtle difference between the units related to the dry and rainy seasons in the Curucutu forest was also noted. Multivariate Analysis of Variance revealed that both site and season of the year (dry or rainy) were important to differentiate the quantity of heavy metals in litter fall stock, although the analysis did not show the interaction between these two factors. Precipitation appeared to be an important factor to disperse air pollutants; one method to better regulate this process is the development and integration of green infrastructure at city level, which might contribute to nature-based solutions. CONCLUSIONS: Results suggest that although the Curucutu forest is not very far from the MRSP, which could result in heavy metal levels similar to those observed in the Guarapiranga forest, the weather conditions, geographic location and rainfall rates might act as efficient physical barriers against the dispersion of pollutants in the urban area. However, it is important to highlight that in the period studied (2012-2013), MRSP presented unusual features during the winter period marked by the highest levels of precipitation which was due to several numbers of frontal systems and also due to their permanence for a couple days in the region. Thus, it is recommended to continue this study in order to obtain a database for characterizing the seasonal variation of air pollution levels in the litter fall and their adverse effects on ecosystem processes in these remnants of the Atlantic Forest.