Erratum to the Influence of Gaseous Pollutants on Silver Artifacts Tarnishing, Vol. 6 (2017), 135-148

The original online version of this article Salem, Y. (2017) The Influence of Gaseous Pollutants on Silver Artifacts Tarnishing. Open Journal of Air Pollution, 6, 135-148. doi: 10.4236/ojap.2017.64011 unfortunately contains grammar mistakes. The author wishes to correct the errors. The present work investigated the effect of common gaseous pollutants on silver artifacts. The study was carried out on coupons made of a silver alloy (91 silver and 9% copper) with chemical composition similar to ancient Egyptian silver artifacts. These coupons were exposed to gaseous pollutants such as sulfur dioxide, nitrogen dioxide, carbon dioxide, hydrogen sulfide and chlorine, each gas separately. The exposure period was four weeks inside a climate chamber with 10 PPM concentration of each gas. After each test, examinations by SEM and PM were used to evaluate the effect of each gas and observe the formed tarnish layers. The results revealed that all gases reacted with the surface except carbon dioxide. The formed tarnish layers varied in coverage and density rate, and the heaviest layer was of H2S coupons. The tested coupons were analyzed by XRD and the results revealed Ag2S, AgCl, Ag2SO4, Ag(NO3)3(NO)3, AgO and Ag2O as corrosion products.

Systematic control technologies for gaseous pollutants from non-ferrous metallurgy

Air pollutant emissions represent a critical challenge in the green development of the non-ferrous metallurgy industry.This work studied the emission characteristics,formation mechanisms,phase transformation and separation of typical air pollutants,such as heavy metal particles,mercury,sulfur oxides and fluoride,during non-ferrous smelting.A series of purification technologies,including optimization of the furnace throat and hightemperature discharge,were developed to collaboratively control and recover fine particles from the flue gas of heavy metal smelting processes,including copper,lead and zinc.Significant improvements have been realized in wet scrubbing technology for removing mercury,fluoride and SO_(2)from flue gas.Gas-liquid sulfidation technology by applying H_(2)S was invented to recycle the acid scrubbing wastewater more efficiently and in an eco-friendly manner.Based on digital technology,a source reduction method was designed for sulfur and fluoride control during the whole aluminum electrolysis process.New desulfurization technologies were developed for catalytic reduction of the sulfur content in petroleum coke at low temperature and catalytic reduction of SO_(2)to elemental sulfur.This work has established the technology for coupling multi-pollutant control and resource recovery from the flue gas from non-ferrous metallurgy,which provides the scientific theoretical basis and application technology for the treatment of air pollutants in the non-ferrous metallurgy industry.

Spatio-temporal distribution of gaseous pollutants from multiple sources in industrial buildings with different flow patterns

Energy consumption of industrial buildings has remained continuously high,and the environmental quality requirements are also constantly improving.Only by improving industrial environmental control technology based on the transport mechanism of the pollution,can the energy consumption of industrial building environmental control be further reduced,and the environmental quality of industrial buildings can be improved as well.Therefore,after verifying the numerical simulation by experiments,this study uses a self-label method to investigate the spatio-temporal distribution of gaseous pollutants from multiple time-series sources in industrial plants with different length-span ratios.The results show that,the polluted flow in plants with different aspect ratios have different flow patterns:(i)the,,Back-mixingw flow pattern occurs when the ratio of ventilation rate 6 and polluted flow rate at the exhaust height b is less than 1,i.e.,G/L_(p)<1,and(ii)the"One-way"flow pattern occurs when G/L_(p)>1.For plants with the"Back-mixing"pattern,the following source pollutants enter a density stratified environment induced by the retained pre-source pollutants.The flow of following source pollutants released at the same intensity as the precursor source can reach the roof,while those with low velocity and density difference may be blocked during the ascending process.The maximum height zm of the flow of the following source is related to both the initial Froude number Fr_(o)of the following source and the unsteady vertical density gradient of the fluid in the indoor environment dpa/dz.For plants with the,,One-way,/pattern,the flow from the following source enters into an environment with approximately uniform density.Under the condition of positive buoyancy,design parameters of ventilation corresponding to the vicinity of G/L_(p)=1 may be the optimal solution for safety and energy conservation.

3D modeling of transformation of gaseous pollutants in the high-pressure turbine of an aircraft engine

Aircraft emissions contribute to global climate change and regional air pollution near airports.Understanding the formation and the transformation of emissions in the aircraft engine is essential to properly quantify the environmental impact and air pollution.However,precise investigation of chemical process in the turbine is challenging because of the complexity of the transformation process in the complex flow relating to the moving blade at high temperature and high pressure.We present here,the first published model study of 3D chemical formations inside a high-pressure turbine and first time to compare three numerical solutions(1D,2D and 3D calculations)of transformation of trace species inside an aircraft engine.The model has simulated the evolution of principal precursor pollutant gases(NOx and SOx)and other species(hydrogen,oxygen species and carbon oxides).Our results also indicated strong dissimilarities in chemical transformations of 3D calculations.In comparing the three solutions,the results obtained showed that the difference of mole fractions of species can be under predicted by 75%between 1D and 2D calculations and in the comparison of 2D and 3D calculation,the under predicted difference may be 90%.

Spatial and temporal variation of particulate matter and gaseous pollutants in 26 cities in China

O3 and PM2.5 were introduced into the newly revised air quality standard system in February 2012, representing a milestone in the history of air pollution control, and China＇s urban air quality will be evaluated using six factors （SO2, NO2, O3, CO, PM2.5 and PM10） from the beginning of 2013. To achieve the new air quality standard, it is extremely important to have a primary understanding of the current pollution status in various cities. The spatial and temporal variations of the air pollutants were investigated in 26 pilot cities in China from August 2011 to February 2012, just before the new standard was executed. Hourly averaged SO2, NO2 and PMlo were observed in 26 cities, and the pollutants O3, CO and PM2.5 were measured in 15 of the 26 cities. The concentrations of SO2 and CO were much higher in the cities in north China than those in the south. As for O3 and NO2, however, there was no significant difference between northern and southern cities. Fine particles were found to account for a large proportion of airborne particles, with the ratio of PM2.5 to PMI0 ranging from 55% to 77%. The concentrations of PM2.5 （57.5 μg/m3） and PMlo （91.2 μg/m3） were much higher than the values （PM2.5：11.2μg/m3; PMI0：35.6 μg/m3） recommended by the World Health Organization. The attainment of the new urban air quality standard in the investigated cities is decreased by 20% in comparison with the older standard without considering O3, CO and PM2.5, suggesting a great challenge in urban air quality improvement, and more efforts will to be taken to control air pollution in China.

Working principle and application of photocatalytic optical fibers for the degradation and conversion of gaseous pollutants

Photocatalytic optical fibers are promising for the degradation of gaseous and volatile pollutants in air due to their high specific surface area,high light utilization efficiency,easy regeneration,and sustainability.In particular,photocatalytic optical fibers have proven highly useful for the removal and conversion of different kinds of air pollutants in air.However,these fibers suffer from low photocatalytic degradation efficiencies.In this review,we have focused on introducing photocatalytic quartz optical fibers and photocatalytic plastic optical fibers for the degradation and transformation of gas-phase air pollutants.The principle of photocatalytic optical fibers and main methods for improving their photocatalytic and light utilization efficiencies based on semiconductor photocatalytic coatings are summarized.Moreover,the Langmuir-Hinshelwood kinetic rate equation was summarized to analyze the photocatalytic reduction of gaseous pollutants.Finally,an outlook on the future of photocatalytic optical fibers toward the removal and conversion of gaseous air pollutants is discussed.

The Vertical Transport of Air Pollutants by Convective Clouds Part Ⅱ：Transport of Soluble Gases and Sensitivity Tests

A two-dimensional, non-reactive convective cloud transport model is used to simulate in detail the vertical transport and wet scavenging of soluble pollutant gases by a deep thunderstorm systems Simulations show that for gases with not very high solubility, a deep and intense thunderstorm can still rapidly and efficiently transport them from boundary layer(PBL) up to mid and upper troposphere. resulting in a local significant increase of concentration in the upper layer and a reduction in PBL. Dissolution effects decrease both the incloud gas concentration and the upward net fluxes. The higher the solubility is, the more remarkable the decrease is. However, for very low soluble gases (H<102 Matm-1), the influences are very slight. In addition, the effects of irreversible dissolution and aqueous reactions in drops on the vertical transport of gaseous pollutants are estimated in extreme.

The Vertical Transport of Air Pollutants by Convective Clouds．Part Ⅲ：Transport Features of Different Cloud Systems

The vertical transport features of gaseous pollutants, with a negative exponent profile of concentration, by different types of convective cloud systems are numerically investigated by using a two-dimensional, reactlonless convective cloud transport model. The results show that an isolated, weak storm is able to pump pollutant gas out PBL and transport it to the mid-troposphere, whereas a deep. intense thunderstorm can very efficiently transport air pollutants up to the mid and upper troposphere and laterally spread with anvil, forming an extensive concentration surge layer at aliitnde of ten odd kilometers altitude. Each type of convective transport results in concentration reduction in PHL. In a wind shear environment the transport efficiency of deep thunderstorm significantly increases and the pollutants enter into clouds on the downshear side at low level and spread downwind in anvil layer. On the other hand, for a cumulus cloud with plenty of liquid water. the gas dissolution effect is increased, and the irreversible aqueous reactions, in extreme, may significantly weaken the vertical transports of pollutant gases even with solubility coefficients no more than 103 M atm-1.

No difference in activity of Sod-1 genotypes of Poa annua to short-term treatment of ambient gaseous organic pollution

Our previous studies indicated that genotypes at locus Sod-1 of Poa annua changed clinally along a gradient of gaseous organic pollution. In the present study, we aimed to know whether there were differential responses of activities of different superoxide dismutase （SOD） genotypes to short-term treatment of ambient gaseous organic pollution. Significant bias from Hardy-Weinberg equibrium was observed on locus Sod-1, and no genotype Sod- l-BB was found. Significantly increased activities were observed in most treatments for genotype Sod-1-AA and in one treatment for genotype Sod-1-AB. However, no significant difference in SOD activities was found between the two genotypes. It was interpreted that fitness difference between the two genotypes was small and treatment duration was too short or extent of ambient organic pollution was too low to lead to differential responses. Other environmental factor effects on activities of superoxide dismutases can also explain the results.

A theoretical study on gaseous pollutant flushing of natural ventilation driven by buoyancy forces in industrial buildings

The acceleration of industrialization worsening indoor environments of industrial buildings has drawn more attention in recent years.Natural ventilation can improve indoor air quality(IAQ)and reduce carbon emissions.To evaluate gaseous pollutant levels in industrial buildings for the development of buoyancy-driven natural ventilation,two theoretical models of pollutant flushing(Model I and Model II)are developed based on the existing thermal stratification theory in combination with the mixing characteristics of lower pollutant.The results show that indoor pollutant flushing is mainly dependent on the pollution source intensity and effective ventilation area.The mixing characteristics of lower pollutant has an important effect on pollutant stratification and evolution during ventilation,but it does not change the prediction results at steady state.When the dimensionless pollution source intensity is larger than 1,the pollution source should be cleaned up or other ventilation methods should be used instead to improve IAQ.In addition,the comparisons between Model I and Model II on instantaneous pollutant concentration are significantly influenced by the pollution source intensity,and the actual pollutant concentration is more likely to be between the predicted values of Model I and Model II.To reduce pollutant concentration to a required level,the pollution source intensity should be in a certain range.The theoretical models as well as the necessary conditions for ventilation effectiveness obtained can be used for the ventilation optimization design of industrial buildings.

Characteristics of air pollution events over Hotan Prefecture at the southwestern edge of Taklimakan Desert, China

Hotan Prefecture is located at the southwestern edge of Taklimakan Desert, the world＇s largest shifting sand desert, of China. The desert is one of the main sources for frequent sand-dust weather events which strongly affect the air quality of Hotan Prefecture. Although this region is characterized by the highest annual mean PMlo concentration values that are routinely recorded by environmental monitoring stations across China, both this phenomenon and its underlying causes have not been adequately addressed in previous researches. Reliable pollutant PM_10 data are currently retrieved using a tapered element oscillating microbalance （TEOM） 1400a, a direct real-time monitor, while additional concentration values including for PM_2.5, sulfur dioxide （SO_2）, nitrogen dioxide （NO_2）, carbon monoxide （CO） and ozone （O_3） have been collected in recent years by the Hotan Environmental Monitoring Station. Based on these data, this paper presents a comparison of the influences of different kinds of sand-dust weather events on PM_10 （or PM_2.5） as well as the concentrations of other gaseous pollutants in Hotan Prefecture. It is revealed that the highest monthly average PM_10 concentrations are observed in the spring because of the frequent occurrence of three distinct kinds of sand-dust weather events at this time, including dust storms, blowing dust and floating dust. The floating dust makes the most significant contribution to PM_10 （or PM_2.5） concentration in this region, a result that differs from eastern Chinese cities where the heaviest PM_10 pollution occurs usually in winter and air pollution results from the excess emission of local anthropogenic pollutants. It is also shown that PM_10 concentration varies within wpical dust storms. PM_10 concentrations vary among 20 dust storm events within Hotan Prefecture, and the hourly mean concentrations tend to sharply increase initially then slowly decreasing over time. Data collected from cities in eastern China show the opposite with the hourly mean PM_10 （or PM_2.5） concentration tending to slowly increase then sharply decrease during heavy air pollution due to the excess emission of local anthropogenic pollutants. It is also found that the concentration of gaseous pollutants during sand-dust weather events tends to be lower than those cases under clear sky conditions. This indicates that these dust events effectively remove and rapidly diffuse gaseous pollutants. The analysis also shows that the concentration of SO_2 decreases gradually at the onset of all three kinds of sand-dust weather events because of rapidly increasing wind velocity and the development of favorable atmospheric conditions for diffusion. In contrast, changes in O_3 and NO_2 concentrations conformed to the opposite pattern during all three kinds of sand-dust weather events within this region, implying the inter transformation of these gas species during these events.

A Clean Technology for Future Prospective: Emission Modeling of Gas Based Power Plant

The aim of present research is to study the dispersion of air pollutants using the air quality model, AERMOD and to predict the impact of pollutants (PM10, NO2 and CO) at the receptor level released from Gas Based Power Plant (GBPP). The net-concentrations including monitored data plus predicted values of PM10, NO2 and CO would be increased from base value 75 to 77.61 μg/m3 with an increase of 3.48%, 22 to 26.66 μg/m3 with an increase of 21.18% and 428 to 538.37 μg/m3 with an increase of 25.79% respectively. The study of hill effect showed that it had profound impact upon the dispersion of pollutants and the ratio (with hill and without hill) of each pollutant was 3.89 for PM10 (24 hr), 2.40 for NO2 (24 hr) and 13.98 for CO (1 hr). The natural gas based plant not only decreases the pollution level but also reduces the hospital treatment cost and protects the public health. The modeling results suggest that the GBPP could be a clean technology as replacement of coal power plants located in the city which pollute the environment considerably in spite of control measures installed.

Real-world gaseous emission characteristics of natural gas heavy-duty sanitation trucks

As compared to conventional diesel heavy-duty vehicles,natural gas vehicles have been proved to be more eco-friendly due to their lower production of greenhouse gas and pollu-tant emissions,which are causing enormous adverse effects on global warming and air pol-lution.However,natural gas vehicles were rarely studied before,especially through on-road measurements.In this study,a portable emission measurement system(PEMS)was em-ployed to investigate the real-world emissions of nitrogen oxides(NO_(x))(nitrogen monoxide(NO),nitrogen dioxide(NO_(2))),total hydrocarbons(THC),carbon monoxide(CO),and carbon dioxide(CO_(2))from two liquified natural gas(LNG)China V heavy-duty cleaning sanitation trucks with different weight.Associated with the more aggressive driving behaviors,the ve-hicle with lower weight exhibited higher CO_(2)(3%)but lower NO_(x)(48.3%)(NO_(2)(78.2%)and NO(29.4%)),CO(44.8%),and THC(3.7%)emission factors.Aggressive driving behaviors were also favorable to the production of THC,especially those in the medium-speed range but sig-nificantly negative to the production of CO and NO_(2),especially those in the low-speed range with high engine load.In particular,the emission rate ratio of NO_(2)/NO decreased with the increase of speed/scaled tractive power in different speed ranges.

A three-dimensional variational data assimilation system for a size-resolved aerosol model: Implementation and application for particulate matter and gaseous pollutant forecasts across China

A three-dimensional variational(3DVAR)data assimilation(DA)system is presented here based on a size-resolved sectional aerosol model,the Model for Simulating Aerosol Interactions and Chemistry(MOSAIC)within the Weather Research and Forecasting model coupled to Chemistry(WRF-Chem)model.The use of this approach means that both gaseous pollutants such as SO2,NO2,CO,and O3 as well as particulate matter(PM2.5,PM10)observational data can be assimilated simultaneously.Two one-month parallel simulation experiments were conducted,one with the assimilation of surface hourly concentration observations of the above six pollutants released by the China National Environmental Monitoring Centre(CNEMC)and one without assimilation in order to verify the impact of assimilation on initial chemical fields and subsequent forecasts.Results show that,in the first place,use of the DA system can provide a more accurate model initial field.The root-mean-square error of PM2.5,PM10,SO2,NO2,CO,and O3 mass concentrations in analysis field fell by 29.27μg m-3(53.5%),34.5μg m-3(50.9%),30.36μg m-3(64.2%),8.91μg m-3(39.5%),0.46 mg m-3(47.4%),and 15.11μg m-3(51.0%),respectively,compared to a background field without assimilation.At the same time,mean fraction error was reduced by 42.6%,53.1%,45.2%,43.1%,69.9%,and 48.8%,respectively,while the correlation coefficient increased by 0.51,0.55,0.48,0.38,0.47,0.65,respectively.Secondly,the results of this analysis reveal variable benefits from assimilation on different pollutants.DA significantly improves PM2.5,PM10,and CO forecasts leading to positive effects that last more than 48 h.The positive effects of DA on SO2 and O3 forecasts last up to 8 h but that remains relatively poor for NO2 forecasts.Thirdly,the influence of assimilation varies in different areas.It is possible that the positive effects of DA on PM2.5 and PM10 forecasts can last more than 48 h across most regions of China.Indeed,DA significantly improves SO2 forecasts within 48 h over north China,and much longer CO assimilation benefits(48 h)are found in most regions apart from north and east China and across the Sichuan Basin.DA is able to improve O3 forecasts within 48 h across China with the exception of southwest and northwest regions and the O3 DA benefits in southern China are more evident,while from a spatial distribution perspective,NO2 DA benefits remain relatively poor.

Impact of gravitation on gaseous pollutant source identification

It is necessary to identify a gaseous pollutant source rapidly so that prompt actions can be taken, but this is one of the difficulties in the inverse problem areas. In this paper, an approach to identifying a sudden continuous emission pollutant source based on single sensor information is developed to locate a source in an enclosed space with a steady velocity field. Because the gravity has a very important influence on the gaseous pollutant transport and the source identification, its influence is analyzed theoretically and a conclusion is drawn that the velocity of fluid is a key factor to effectively help weaken the gravitational influence. Further studies for a given 2-D case by using the computational fluid dynamics （CFD） method show that when the velocity of inlet is less than one certain value, the influence of gravity on the pollutant transport is very significant, which will change the velocity field obviously. In order to quantitatively judge the practical applicability of identification approach, a synergy degree of the velocity fields before and after a source appearing is proposed as a condition for considering the influence of gravity. An experimental device simulating pollutant transmission was set up and some experiments were conducted to verify the practical application of the above studies in the actual gravitational environment. The results show that the proposed approach can successfully locate the sudden constant source when the experimental situations meet the identified conditions.

Outdoor air pollution and the onset and exacerbation of asthma

Exposure to outdoor air pollution has been consistently associated with asthma.In this study,we reviewed the epidemiological studies published within the last 5 years on the association between outdoor air pollution and exacerbation and onset of asthma.A large number of studies have been published within the last 5 years.Short-term exposure to outdoor air pollution is associated with exacerbation of pre-existing asthma,manifested as worsening of symptoms and increasing of asthma-related emergency room visits and hospital admissions.Furthermore,increasing evidence suggests that long-term exposure to outdoor air pollution can result in onset of asthma.Children are more susceptible to outdoor air pollution.Future studies should be conducted to explore the mechanisms underlying the association between air pollutants and onset of asthma,including gene involvement.In addition,disentangling the effect of a mixture of air pollutants and identifying the key components of air pollution will complete the existing evidence.More importantly,a better understanding is required on the future impact of air pollution on asthma under a changing climate.

Incineration experiment of medical waste of novel coronavirus pneumonia(COVID-19)in a mobile animal carcass incinerator

Incineration experiment of medical waste was carried out in a mobile animal carcass incinerator.Simulated medical waste(69%cotton,1.5%wood product,4.5%mask and 25%moisture)was used as raw material.The temperature trend of first and second combustion chamber,the operating conditions and the emission characteristics of gaseous pollutants were studied.The results indicated that the temperature of first combustion chamber can be maintained at 550-650℃ without external heating,while in the final stage a burner was used to realize the burnout of material.The temperature of the second combustion chamber was always lower than that of the first combustion after the burner stopped working.The concentration of CO emission in flue gas was high due to the low disposal efficiency of the mobile incinerator,while NOX and SO2 emission concentrations were far below the standard limit value(GB 18484-2001).

A photo-catalytic reactor for degrading volatile organic compounds(VOCs)in paper mill environment

Volatile organic pollutants such as benzene and formaldehyde are commonly detected in the ambient air of paper mills.To remove these pollutants from the air,a photo-catalytic reactor was developed in this study.The reactor had a series of honeycomb aluminum meshes coated with nanosized titanium dioxide as the catalyst for the degradation reactions of gaseous pollutants.Both formaldehyde and benzene could be completely degraded in the reactor.However,the degrading time for benzene was much longer than that for formaldehyde,and the degradation rate of benzene decreased with increasing initial benzene concentration.It was found that the reaction pathway for formaldehyde in the mixture was different from that in its single component form,and it took about two times longer time to be degraded than that for its single component form.The reaction pathway of benzene was similar in either case although the degradation time for benzene was about 50%shorter in the mixture form.