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The impact of local sources and meteorological factors on and particulate matter concentrations

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The impact of local sources and meteorological factors on nitrogen oxide and particulate matter concentrations:A case study of the Day of Atonement in IsraelUri Dayan a ,*,Yigal Erel b ,Jacob Shpund b ,Levana Kordova c ,Arye Wanger d ,James J.Schauer eaDepartment of Geography,The Hebrew University,Mt.Scopus,91905Jerusalem,Israel bInstitute of Earth Sciences,The Hebrew University,Givat Ram,91904Jerusalem,Israel cMinistry of Environmental Protection,125Menachem Begin Rd.,Tel Aviv 61071,Israel dAdam Teva VaDin (IUED),48Yehuda Ha-Levi St.,Tel Aviv 65115,Israel eCivil and Environmental Engineering,University of Wisconsin-Madison,WI 53706,USAa r t i c l e i n f oArticle history:Received 24April 2010Received in revised form 6January 2011Accepted 3February 2011Keywords:PM NO xPollution sourcesShort-lived pollutants Long-lived pollutantsa b s t r a c tMeasurements of the atmospheric concentrations of NO x and particulate matter (PM)in three urban centers in Israel before,during,and after the Day of Atonement were performed for nine consecutive years (2000e 08).This enabled to investigate the signi ficance of local versus long-range sources of pollution and probe the effect of meteorological conditions (synoptic systems,ventilation rates,height of surface boundary layer,and wind speed)on level of pollution.During the Day of Atonement all traf fic and most of the industrial activities cease in the Jewish populated parts of the country.We observed that in spite of this,concentrations of particulate matter (PM 2.5and PM 10)are very similar in all three urban centers during the Day of Atonement to the days before and after.Moreover,PM levels during the Day of Atonement are generally higher during Red Sea trough synoptic conditions which carry air from the Saudi and Jordanian deserts in the east and southeast relative to Persian Trough synoptic conditions which bring air from the eastern Mediterranean and the Black Sea region in the north-west.In addition,55%of the variation in PM values during the nine days of Atonement included in this study can be explained by changes in ventilation rates of the atmosphere,namely the product of the mixing depth and a representative boundary layer wind speed.Thus,long-range sources and local mixing conditions determine the concentrations of PM in the atmosphere of Israel as expected from their long residence time.On the other hand,NO x concentrations during the Day of Atonement are signi ficantly lower than the days before and after,re flecting NO x short residence time in the atmosphere and the strong in fluence of local emission sources.Furthermore,the difference in concentrations of NO x in different Days of Atonement cannot be accounted for either by different synoptic conditions or by variations in ventilation rates,height of surface boundary layer,and wind speed.They are determined by the combination of local and regional sources of emission and the meteorological conditions which control their transport from these nearby sources to the sampling station.Ó2011Elsevier Ltd.All rights reserved.1.IntroductionThe concentrations of air pollutants in the tropospheric boundary layer are determined by the interactions between emis-sion fluxes and synoptic circulation types as well as regional wind flow pattern induced by mesoscale meteorological processes (i.e.,land e sea breeze).Each synoptic type dictates the long-range transport and a distinctive air mass affecting dispersion condi-tions (Kulmala et al.,2000)while mesoscale meteorology controlthe transport of regional air pollution.These interactions between long-range and air movements on the regional scale,were used to explain the concentrations of air pollutants in several regions of the world including the eastern Mediterranean (e.g.,Dayan and Graber,1981;Koch and Dayan,1992;McKendry,1994;Moulin et al.,1998;Shwarzhoff and Reid,2000;Yarnal et al.,2001;Kahana et al.,2002;Dayan and Levy,2002;Dayan et al.,2007).The signi ficance of transboundary air pollution contribution to the local or regional budget of atmospheric pollution has been recognized in the last decade.Studies based on trajectory models and recent developments in satellite remote sensing technologies and on chemical and isotopic tracers resulted in the ability to observe major pollution events in which,foreign sources contribute*Corresponding author.Tel.:þ97225883340;fax:þ97225820549.E-mail address:msudayan@mscc.huji.ac.il (U.Dayan).Contents lists available at ScienceDirectAtmospheric Environmentjournal homep age:www.elsevi/locate/atmosenv1352-2310/$e see front matter Ó2011Elsevier Ltd.All rights reserved.doi:10.1016/j.atmosenv.2011.02.017Atmospheric Environment 45(2011)3325e 3332non-trivial amounts of pollution especially to the atmosphere in countries where local emission have declined(Xiao-Yang et al., 2007;Zhao et al.,2007;Avise et al.,2008).Israel is known to receive significant contribution of atmospheric pollution from foreign sources in addition to local sources(Wanger et al.,2000; Matvev et al.,2002;Erel et al.,2002,2006,2007;Falkovich et al., 2004;Rudich et al.,2008).This is especially applicable tofine (PM2.5and PM10)atmospheric particles which have long residence time in the atmosphere.The estimation mean-residence time of atmospheric aerosols as applied to particles in the lower atmo-sphere below precipitation cloud levels is about eight days (Papastefanou,2006).The Day of Atonement is observed in Israel every fall(either in September or October).During this day,all motorized trans-portation and most of the industrial activities in the Jewish parts of the country cease for24h,hence,it provides a unique opportunity to test the relative contribution of pollution sources within urban centers versus regional and foreign sources.Previous studies have observed significant reduction in atmospheric pollution in Israel during the Day of Atonement(e.g.,Mamane et al.,1981;Stanhill and Moreshet,1992).The later have analyzed the reduction in insolation in Beit Dagan,Israel,as related to motor traffic,but have not measured the impacts of such traffic on air pollutant concen-trations(trace gases and particulates).Moreover,they did not relate theirfindings to meteorological conditions.The former study conducted by Mamane et al.(1981)has not dealt with synoptic conditions and meteorological parameters in tandem with pollutant concentrations,but rather used the soiling index as surrogate for trace gases and particulates.Measurements at an air quality monitoring station in the center of Tel Aviv have shown that on this day the soiling index,a measure of the concentration of particles of anthropogenic origin,was less than10%of that measured during the preceding and following seven days(Mamane et al.,1981).These observations are interesting in light of the well documented“ozone weekend effect”where urban areas might have higher ozone(a secondary pollutant)concentrations on weekends than on weekdays although NO x(primary pollutant) emissions are usually lower during weekends(Cleveland et al., 1974;Lebron,1975;Marr and Harley,2002a,b;Blanchard and Tanenbaum,2003;Fujita et al.,2003;Heuss et al.,2003;Pun et al.,2003;Murphy et al.,2007;Tonse et al.,2008;Yarwood et al.,2008).In addition,it was shown lately that during week-days the concentrations of EC(elemental carbon),TC(total carbon), certain metals,and the ultrafine(0.05e0.14m m)and coarse (1.2e10m m)fractions of suspended particulate matter in an urban center in Germany are higher than during weekends when traffic density is30%lower(Bruggemann et al.,2009).Also,Khoder and Hassan(2008)report higher weekdays TSP levels in Cairo relative to weekends(454m g mÀ3on weekdays and298m g mÀ3on weekends).In the current study we use measurements of several atmo-spheric pollutants(NO x,PM,O3,SO2)prior,during,and after the Day of Atonement in three urban centers in the country in nine consecutive years from2000to2008in order to quantify the impact of local urban versus regional and foreign sources on the concentrations of these pollutants which vary in their atmospheric fate and residence time.We also examine the effect of meteoro-logical conditions on the ratio between local and foreign sources.During the part of the year when the Day of Atonement is celebrated(September,October)one of the following two synoptic systems prevail in the region,(1)a Persian Gulf trough or(2)Red Sea trough.Persian Gulf trough is a surface thermal barometric trough,extending from the south-west Asian Monsoon.The Persian Gulf Trough begins to occur in the middle of June and remains until October.Because of its thermal origin its height is restricted to about500e1500m,above which dominates an extension of the subtropical high pressure system(Dayan et al.,2002).The transi-tional zone between these two pressure systems defines an inver-sion layer.In general,aerosol loading in the Eastern Mediterranean troposphere associated with this system is characterized by low variability from day to day(Dayan and Levy,2005).Red Sea trough is an extension of a low surface pressure from a tropical depression toward the Red Sea,which sometimes penetrates up north as far as Turkey.Its energy and humidity sources are from the tropical regions and it migrates along a mostly North-South direction.It is especially frequent during the autumn season and generates east-erly surface winds which might transport dust from Jordan and Saudi Arabia toward the eastern Mediterranean.2.Experimental methodsAtmospheric measurements used in the study were collected from three urban centers in Israel(Fig.1).In the Tel Aviv area,the most populated region in the country which is located in the coastal plain,we used data collected from two stations,one in a regular middle class neighborhood(Yad Avner),and one from abusyFig.1.Map of Israel and the major urban centers,Tel Aviv,Jerusalem,and Beersheba included in the present study.Blue arrows mark the synoptic-scale wind directions during Persian Trough condition,and brown arrows mark the synoptic-scale wind directions during Red Sea trough conditions.(For interpretation of the references to color in thisfigure legend,the reader is referred to the web version of this article.)U.Dayan et al./Atmospheric Environment45(2011)3325e3332 3326intersection in one of the most religious towns in Israel(Remez,in Bnei Brak).One station is located in Jerusalem,approximately 60km in-land,700m asl,and one station is from Beersheba,in the semi-arid part of the country,approximately50km from the coastal plain,and at200m asl.The air monitoring stations operated by the Israeli Ministry of Environmental Protection measure several major pollutants: particulate matter(PM10at Yad Avner,Jerusalem,and Beersheba and PM2.5in Remez),sulfur dioxide(SO2),nitrogen oxides(NO x),carbon monoxide(CO),and ozone(O3).The analytical monitors in each station are fully automated and employed U.S.Environmental Protection Agency(EPA)approved methods and procedures.The monitors were equipped with daily automated calibration systems. Once a year,the stations conduct quality control and quality assur-ance tests.Sulfur dioxide is measured by Fluorescence SO2analyzer (Thermo Environmental Instruments A,Model43C).Nitrogen dioxide is determined by Chemiluminescence NO e NO2e NO x analyzer(Thermo,Model42C).Ozone is measured by U.V.Photo-metric O3Analyzer(Thermo,Model49C).Carbon monoxide is measured by Gas Filter Correlation(GFC)CO Analyzer(Thermo, Model48C).PM10and PM2.5are measured by Verewa Extractive Beta Gauge Particulate Monitor(Durag A,Model F-701).3.ResultsSynoptic classification reveals that during the Day of Atonement of2001,2004,2006,and2007Persian trough synoptic system prevailed,accompanied by westerly winds;while the Day of Atonement of2000,2002,2003,2005,and2008experienced weak easterly winds generated by the Red Sea Barometric trough (Table1).A common methodology to assess the dispersion condi-tions of the atmosphere over the region is by calculating the ventilation rates(VR e Table1).This term is the mixed layer depth multiplied by the mean wind speed in the mixed layer,representing the ability of the atmosphere to dilute and transport contaminants away from a source region.The results obtained prior,during,and after the Day of Atonement indicate that NO x and PM represent the two extreme cases,where NO x,which is emitted mostly from combustion sources,displays the largest reduction in concentrations during the Day of Atonement relative to the days before and after,while PM vary the least(Table2; Figs.2and3).NO x values decrease during the Day of Atonement,and the ratio of the average NO x values during the Day of Atonement and either the day before or after is always lower than one(Table2).These daily variations are,by far,larger than the inter-annual variations in NO x concentrations measured in Remez(Tel Aviv area).The relative standard deviation for the former,calculated for the period2000e08 is0.18as compared to the much larger value of0.57obtained for the later.The average ratio values of NO xðthe ratio of NO x during the Day of Atonement and the day before¼NO xDA=NO xbeforeand the ratio of NO x during the Day of Atonement and the day after¼NO x DA=NO xafterÞduring the nine years included in this study change from one station to the other.The station with the lowest ratio is as expected the Remez station in the Tel Aviv area.This is because it is the most polluted station during most of the year,located near a major road.NO xDA=NO xbeforeand NO xDA=NO xaftervalues are approxi-mately0.10in Remez,0.25in Yad Avner(both in the Tel Aviv urban center),0.45in Beersheba,and0.50in Jerusalem(Table2).The same trend and more or less the same ratios hold for the lowest and highest values of NO x measured in each station(Table2).During the Day of Atonement a substantial decrease in emis-sions is observed.Newmark(2007)found that in Tel Aviv city buses produce39% of the PM emissions.Trucks and taxis contribute,each,a quarter of the total PM emissions.Since all motorized transportation cease for 24h in the whole country during this day,it seems evident that such a substantial decrease occurs in all major towns of Israel.PM concentrations on average do not change in spite of this substantial decrease in emissions during the Day of Atonement.The PM DA/PM before and PM DA/PM after values range between0.66and 1.27,with no significant difference between the stations.In general, PM DA/PM before and PM DA/PM after are higher during Red Sea trough synoptic conditions as compared with Persian Trough synoptic conditions(Tables1and2).4.DiscussionThe decreases in NO x concentrations observed in the current study resemble results obtained in previous studies.For example, the reduction in NO x concentrations in Remez is very similar to the concentration reduction reported by Wanger(1999)for the1998 Day of Atonement.Ozone concentrations show a mirror image of the NO x,and on certain Atonement Days have higher values than the days before of after(Table2).As explained by numerous studies,O3concentrations are sometimes expected to increase during days of reduced traffic as ozone production depends on a combination of several factors,including time profiles of ozone precursors(NO x and VOCs),their relative ratios,water vapor content,solar UV intensity,and meteorological conditions(Dayan and Levy,2002).This phenomenon(the ozone weekend effect) was observed more than30years ago(e.g.,Cleveland et al.,1974; Lebron,1975;Tonse et al.,2008).Hence,we focus on NO x and PM concentrations and compared24-h averages,and ten(for NO x)and three(for PM)lowest and highest values of the day prior,during, and after Day of Atonement(Table2).The difference between the three urban centers in NO xDA=NO xbefore and NO xDA=NO xaftervalues(0.10in Remez,0.25in Yad Avner(both in the Tel Aviv urban center),0.45in Beersheba,and0.50in JerusalemTable1Classification of nine Days of Atonement along synoptic categorization and local potential conditions for dispersion.Date Inv.base BD12Z height(m)Wind speed BD12Z(m sÀ1)Vent.rates WS BD(m2sÀ1)Synoptic catThursday:9e10/10/081460 3.04380Red Sea trough Saturday:21e22/09/07766 3.632781Persian trough(modal) Monday:01e02/10/061768 4.057160Persian trough(deep) Thursday:12e13/10/05476 5.382561Red Sea trough Saturday:24e25/09/041276 3.584568Persian trough(deep) Monday:05e06/10/03466 3.51631Red Sea trough Monday:15e16/09/02323 4.251373ColeThursday:26e27/09/01614 4.52763Persian trough(modal) Monday:08e09/10/00284 5.381528Red Sea troughSources of data:Inversion base,wind speed and ventilation rates are from:/upperair/sounding.html.Synoptic Categories from:/cgi-bin/db_search/DBSearch.pl.BD¼Beit Dagan,the central meteorological station in Israel,located near the Tel Aviv urban center.U.Dayan et al./Atmospheric Environment45(2011)3325e33323327Table 2(a)Concentrations of NO x (ppb)and PM (m g m À3)of the lowest and highest values (ten for NO x ,and three for PM)during the Day of Atonement (DA)and the day before or after.(b)NO x and PM ratios of the same samples.Year/day RemezYad Avner Jerusalem Beersheba NO xPM 2.5NO xPM 10NO xPM 10NO xPM 10Before ADAfter Before ADAfter Before ADAfter Before ADAfter Before ADAfter Before AD After Before ADAfter Before AD After(a)Lowest 20088.10.3914 2.7 4.8 1.02 3.0161314200712 1.0922 5.3 4.111 2.50.81 4.0 3.61529117.6131714207.6 3.17.320112820068.90.8715 5.7 1.8 6.09.113217.4 3.18.5201317 6.2 4.0 6.2161624200519 2.712 3.31015 4.2 1.9 2.922 4.41411 4.0 6.21731318.3 5.77.32631312004120.7517 6.4 4.47.1 6.5 1.4228.4 4.07.8131115 5.9 3.2 5.9191016200310 6.112 4.2 2.3 4.721202711 4.91126315111 3.4 5.6343037200221 2.530101015 2.9 2.47.01934267.4 4.17.2266436 6.0 3.07.61740572001211.223212724 5.8 3.9 6.148472012 2.9 3.85561437.2 3.1 4.133373020009.1 3.7 3.9 4.3 1.7 3.8259.3136 4.510262842 4.7 1.6 2.5221115Highest 20087714 6.99.45616603812322007899.41361916348411634838624629312435291931433557200648 6.610182336648305418 6.0355********.4235828442005119298823294967 6.4408813279514526575373291318504844200413116129611153564053211637453337258.0244535492003242924441569727374343075611111248.5 5.7208280712002101223643356353710135869712823139552120174259.44069891212001130241171307546458.2317569812611291009987279.4145563582000423625587.7437212073211137957687241014997355Ratios Year/dayRemez Yad Avner Jerusalem Beersheba NO x PM 2.5NO x PM 10NO x PM 10NO x PM 10DA/beforeDA/afterDA/beforeDA/afterDA/beforeDA/afterDA/beforeDA/afterDA/beforeDA/afterDA/beforeDA/afterDA/beforeDA/afterDA/beforeDA/after(b)Average 20080.140.510.230.270.460.640.360.560.520.800.360.420.400.6120070.090.06 1.070.540.110.130.790.520.270.310.710.640.440.460.710.5220060.120.060.450.470.820.560.340.190.490.630.600.400.610.5720050.190.29 1.380.710.120.34 1.03 1.160.66 1.30 1.320.860.530.73 1.050.9720040.080.090.290.230.710.520.510.370.800.770.400.370.650.722003 1.030.930.310.29 1.050.890.530.34 1.430.740.290.350.960.9620020.160.07 1.26 1.090.350.11 1.510.800.610.22 2.45 1.010.470.31 1.760.6720010.150.170.96 1.340.250.510.93 1.040.320.410.97 1.180.310.56 1.030.9620000.74 1.110.160.28 1.05 1.210.590.310.880.870.340.570.76 1.07Average 0.130.120.930.890.230.270.930.820.470.44 1.060.830.420.460.880.78Stdev 0.040.070.330.320.090.130.290.270.140.340.610.170.100.130.390.21Lowest 20080.050.190.210.340.790.9120070.090.050.770.370.330.20 4.020.510.670.580.840.700.400.420.570.4020060.100.060.310.30 1.470.650.420.370.670.770.640.650.990.6720050.140.22 3.000.670.440.640.200.320.350.64 1.820.990.680.78 1.18 1.0020040.060.040.700.620.210.060.480.520.820.700.550.540.510.6020030.600.530.550.490.950.730.440.43 1.220.610.300.610.870.8220020.120.09 1.000.670.820.34 1.79 1.330.560.57 2.42 1.770.490.39 2.360.7020010.060.05 1.34 1.150.680.650.97 2.290.240.76 1.12 1.420.430.74 1.12 1.2620000.400.940.390.440.370.720.340.640.500.77Average 0.090.080.950.660.560.48 1.250.830.450.55 1.270.990.480.60 1.010.78Stdev 0.030.070.910.310.180.17 1.260.700.140.130.630.440.140.140.610.26Highest 20080.19 1.360.280.260.310.3720070.100.070.840.470.130.170.790.610.790.700.640.610.810.6220060.140.070.410.500.620.550.330.170.460.710.630.320.480.6320050.240.33 1.270.590.100.16 1.51 1.670.89 1.730.930.720.450.740.97 1.0820040.120.130.190.210.700.750.750.430.730.880.320.330.790.722003 1.23 1.230.330.21 1.020.990.880.40 1.810.890.670.290.98 1.1220020.210.06 1.70 1.600.280.08 1.120.750.560.14 2.290.690.370.24 1.290.7320010.180.200.58 1.630.180.270.920.860.440.400.99 1.140.350.69 1.15 1.1020000.85 1.440.130.18 1.67 1.630.410.700.74 1.33Average 0.170.14 1.03 1.070.190.18 1.040.980.640.55 1.140.820.480.490.900.92Stdev0.050.110.430.530.090.060.380.440.230.590.660.160.140.210.250.27U.Dayan et al./Atmospheric Environment 45(2011)3325e 33323328(Table 2))probably re flects population differences.Whereas the Tel Aviv area has a vast majority of Jews (98.7%;CBS,2010),and hence there is very little traf fic,Beersheba is located between Gaza Strip and the southern part of the West Bank (Fig.1),and might be getting pollution from there during the Day of Atonement.Jerusalem and its vicinity are inhabited by both Jews and Arabs (82.15and 17.1%,respectively;CBS,2010)and pollution emitted from cars in east Jerusalem and from other urban centers in the West Bank reaches Jerusalem during the Day of Atonement.Hence,our results suggest that approximately 10e 25%of the NO x load in Tel Aviv (similar to results obtained by Wanger,1999),45%in Beersheba and 50%in West Jerusalem originate from sources outside the urban centers them-selves.The large differences in NO x reduction between the urban centers are expected as NO x have low residence time in the atmo-sphere,less than 12h (Mamane et al.,1981;Wanger,1999).The reduction in NO x concentrations during the Day of Atonement in different years and the differences between the three urban centerscannot be explained by either,synoptic classi fications or by meso-scale meteorological conditions (i.e.,ventilation rate,inversion base height multiplied by wind speed)(Tables 1and 2,Figs.4and 5).For example,Remez (within the Tel Aviv urban center)and Jerusalem stations behave similarly and Remez station behaves differently than the other station (Yad Avner)within the Tel Aviv urban center (Fig.5).In both Remez and Jerusalem stations NO x DA =NO x before decreases as ventilation rates and inversion base heights increase,and NO x DA =NO x before increases when wind speed increases.In Beer-sheba NO x DA =NO x before increases with increasing ventilation rates,inversion base height,and wind speed (Fig.5).In Yad Avner (the other station within Tel Aviv),NO x DA =NO x before values do not change with ventilation rates,inversion base height,but slightly decrease with wind speed (Fig.5).These observations can be explained by the geographical settings and the types of neighborhood (i.e.,urban,suburban or rural)in which the stations are located.The lowest immediate sources of pollution are around Remez and the Jerusalem stations as both are located in religious neighborhoods where traf fic and industrial activities completely cease during the Day of Atone-ment.These stations are most sensitive to neighboring pollution sources carried by local winds (and expressed by wind speed)and being diluted when ventilation rates and inversion base height are high.Both monitoring stations,Remez (Bnei Brak)and Jerusalem are020406080100120c o n c e n t r a t i o nhalf hours19/9/0720/9/0721/9/0722/9/0723/9/0724/9/07Fig.2.Concentrations of PM 10(mgmÀ3),NOx(ppb),O 3(ppb),and SO 2(10Âppb)in the residential station,Yad Avner,in the Tel Aviv urban center in September 2007.The thick arrow marks the Day of Atonement.Fig.3.Column charts of the 24-h average concentration values of NO x (ppb)and PM (m g m À3)before,during and after the Day of Atonement for Remez (a),Yad Avner (b),Jerusalem(c)and Beersheba (d).0.02.04.06.08.010.012.0Avg NOxm (s e t a R .t n e V 2)c e s /Fig.4.The relationships between NO x concentrations (average values of the foururban stations)during the Day of Atonement and ventilation rates (inversion base height multiplied by wind speed)in the four stations.U.Dayan et al./Atmospheric Environment 45(2011)3325e 33323329Fig.5.The relationships between NO x ratios and(a)ventilation rates,(b)inversion base height,and(c)wind speed(WS)in the four stations.U.Dayan et al./Atmospheric Environment45(2011)3325e33323330located within road intersections and affected mainly by local traf fic.This is especially the case for Remez exposed often to pollutants emitted from the congested traf fic.The only difference between these stations is that the station in Jerusalem is much less polluted on regular days than Remez.Therefore,the average NO x DA =NO x before and NO x DA =NO x after are lower in Remez than in Jerusalem.The other station in Tel Aviv,is located in a residential neighborhood where values of NO x during regular days are low (Table 1)and there are no nearby or distant pollution sources during the Day of Atonement.The station in Beersheba is located down wind from either Gaza Strip or the southern part of the West Bank and hence receives more pollution during the Day of Atonement when the regional air velocity is high,as expressed by ventilation rate and boundary layer height,and less by local wind speed.These results demonstrate the complexity of predicting concentrations and changes in concentra-tions of short-lived pollutants in urban centers,as they undergo chemical transformations (e.g.,NO x e O 3titration,Sillman,1999),are affected by immediate sources around the stations,by other parts of the same urban center which are more polluted during the sampling campaign,and by more distant sources.The behavior of PM is entirely different than that of NO x .In all stations the nine-year average ratio of the PM values during the Day of Atonement and either the day before or after is always around unity (Table 2).PM concentrations sometimes increase during the Day of Atonement relative to either the day before or after (Table 2).In general,PM DA /PM before and PM DA /PM after are higher during Red Sea trough synoptic conditions which carry air from the Saudi and Jordanian deserts (east e southeast of Israel)relative to Persian Trough synoptic conditions which bring air from the eastern Mediterranean and the Black Sea region in the north-west (Fig.1,Tables 1and 2).Furthermore,during 2004,2006,and 2007(all have Persian trough synoptic conditions)the ratios of PM during Day of Atonement and the days before and after are below one in all stations and PM DA /PM before and PM DA /PM after are very similar (with only a few exceptions;Table 2).Furthermore,in every station the average PM DA /PM before and PM DA /PM after values of the Persian trough synoptic conditions are lower than the average PM DA /PM before and PM DA /PM after values of the Red Sea conditions (Tables 1and 2).In addition,the average of PM DA /PM before and PM DA /PM after values of all stations during Persian trough synoptic conditions is 0.76Æ0.12while the average of PM DA /PM before and PM DA /PM after values of all stations during Red Sea synoptic condi-tions is 0.99Æ0.10(Tables 1and 2).These results are consistent with Dayan and Levy (2005)who found a signi ficant difference in PM concentrations over Israel for the different synoptic systems (RST as compared to PT).The expected effect of 24-h cease in PM emissions (based on PM residence time in the atmosphere)should be around 10%,within the uncertainty of our data,but much lower than the difference between the PM behavior during the two synoptic systems.This suggests that long-range sources play important role in deter-mining the concentrations of PM in the atmosphere of Israel as suggested by Erel et al.(2006,2007).Additionally,a clear effect of ventilation rate on PM load in the three urban centers during the nine years of the study is observed (Fig.6).Approximately 55%of the variation in PM load during Day of Atonement is accounted for by ventilation rate.This finding is in accordance with Matvev et al.(2002)who derived the long-term mean values of ventilation rates over Israel,its seasonal variation and impacts on pollutant concentrations.This effect is superimposed on the impact of long-range sources determined by synoptic conditions.Hence,the behavior of PM is clearly controlled by long-range transport as determined by the synoptic conditions and by the ability of the atmosphere to dilute and transport contaminants away from a source region manifested by local dispersion conditions.5.Summary and conclusionsThe Day of Atonement,during which,all traf fic and most industrial activities cease over Israel,provides a unique opportu-nity to distinguish between the behavior of short and long-lived pollutants and the impact of atmospheric conditions on such pollutants.This is demonstrated by the temporal behavior of their concentrations prior,during and after this special day.Conclusions derived from the analysis of the atmospheric concentrations of NO x and PM for a 9-yr period at three major urban centers in Israel are as follows:1)NO x and PM represent the two extreme cases where NO x displays the largest reduction in concentrations during the Day of Atonement relative to the days before and after,while PM vary the least.2)Variation in PM concentrations,as pollutant of long residence time,is more affected by long-range sources determined by speci fic synoptic con figurations,3)Diurnal varia-tion in NO x concentrations re flects its short residence time and the strong in fluence of local emission sources,4)As expected for a short-lived pollutants,large differences in NO x concentrations during the Day of Atonement were observed between the three urban centers.This study has presented further evidences on the complexity of assessing the day-by-day variations in concentrations of short-lived pollutants.ReferencesAvise,J.,et al.,2008.The impact of global changes on the long-range transport ofAsian emissions to the western United States,and the implications on regional air quality.In:10th Conference on Atmospheric Chemistry,the 88th AMS Annual Meeting New Orleans,LA,USA.Blanchard,C.L.,Tanenbaum,S.J.,2003.Differences between weekday and weekendair pollutant levels in southern California.Journal of the Air &Waste Management Association 53,816e 828.Bruggemann,E.,Gerwig,H.,Gnauk,T.,Muller,K.,Herrmann,H.,2009.In fluence ofseasons,air mass origin and day of the week on size-segregated chemical composition of aerosol particles at a kerbside.Atmospheric Environment 43,2456e 2463.Central Bureau of Statistics,2010.Statistical Abstract of Israel,2010.Cleveland,W.S.,Graedel,T.E.,Kleiner,B.,Warner,J.L.,1974.Sunday and workdayvariations in photochemical air-pollutants in New-Jersey and New-York.Science 186,1037e 1038.Dayan,U.,Graber,M.,1981.Analysis of synoptic conditions in the Eastern Medi-terranean that led to elevated air pollution concentrations in Israel.In:Shuval,H.(Ed.),Developments in Arid Zone Ecology and Environmental Quality.Balaban ISS,Philadelphia,pp.383e 397.Dayan,U.,Levy,I.,2002.Relationship between synoptic-scale atmospheric circu-lation and ozone concentrations over Israel.Journal of Geophysical Research 107(D24),4813.doi:10.1029/2002JD002147.Avg PMV e n t . R a t e s (m 2/s e c )Fig.6.The relationships between average PM load of the four stations during the Day of Atonement and ventilation rates (inversion base height multiplied by wind speed)in the four stations.U.Dayan et al./Atmospheric Environment 45(2011)3325e 33323331。

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四年级下册第二单元英语作文我想发明的一种眼镜

四年级下册第二单元英语作文我想发明的一种眼镜

四年级下册第二单元英语作文我想发明的一种眼镜全文共3篇示例，供读者参考篇1The Glasses I Want to InventHave you ever wished you had a special pair of glasses that could do amazing things? Well, I have! I dream of inventing a pair of high-tech glasses that can make our lives easier and more fun. Let me tell you all about the incredible features I'd love these glasses to have.First of all, my invented glasses would have a built-in translation feature. Imagine being able to understand any language just by looking at the person speaking! The glasses would instantly translate the words into your native tongue and display the subtitles right before your eyes. This would be so helpful when traveling to different countries or meeting people from other cultures. No more struggling to communicate – my translation glasses would break down all language barriers!But that's not all. My dream glasses would also have x-ray vision capabilities. With the push of a button, you could see through solid objects! This would be incredibly useful in so manysituations. Lost your keys or phone? Just use the x-ray vision to locate them behind the couch cushions. Or imagine being able to check if there are any pipes or wires behind the walls before drilling a hole. The x-ray vision would prevent lots of accidents and save us from having to tear down walls unnecessarily.Another awesome feature would be augmented reality games and adventures. By activating this mode, the glasses would project interactive holograms into the real world. You could battle virtual monsters on your street, explore magical realms in your backyard, or even go on exciting treasure hunts around your neighborhood! The possibilities for augmented reality fun would be endless with my invented glasses.But my dream glasses wouldn't just be for entertainment –they would also have important safety functions. They could detect danger and warn you about potential threats. If there was a fire, gas leak, or other hazard nearby, the glasses would immediately alert you with flashing lights and sound effects. They might even be able to suggest the quickest escape route! Parents would feel much safer letting their kids play outside while wearing these protective glasses.Furthermore, the glasses would have a built-in camera and recording capabilities. At the touch of a button, you couldcapture photos and videos of your adventures without needing a separate device. The recordings would be stored right in the glasses' memory, allowing you to relive your favorite moments again and again. This would be perfect for documenting fun trips, events with friends and family, or even just your everyday life.And if you ever needed help with something, the glasses would have a virtual assistant to guide you. Looking for instructions on how to tie shoelaces or bake cookies? The virtual assistant would walk you through each step with clear visuals and audio explanations. You could even ask it random questions about any topic and get a wealth of information instantly displayed before your eyes. It would be like having a personal tutor and encyclopedia inside your glasses!But perhaps the most mind-blowing feature would be the teleportation function. That's right – my invented glasses could actually teleport you to different places! All you'd have to do is think about your desired destination, and the glasses would instantly transport you there in a blinding flash of light. Can you imagine being able to teleport to your friend's house for a playdate without needing a ride from your parents? Or being able to visit the Great Pyramids or the Amazon rainforest just bythinking about it? With teleportation abilities, the entire world would be at your fingertips.Of course, the glasses would also have some fun cosmetic features to personalize your look. You could change the frame color and style with a simple voice command. Or project different graphics and animations onto the lenses for an awesome visual effect. The possibilities for self-expression would be limitless!I know this all might sound like a crazy sci-fi fantasy, but I believe that with continued advancements in science and technology, inventions like my dream glasses could someday become a reality. And just think about how incredible that would be! A single pair of glasses that combine language translation, x-ray vision, augmented reality gaming, safety alerts, camera functions, a virtual assistant, and even teleportation? It would truly be the most versatile, amazing gadget in the world.So there you have it – my vision for the ultimate pair of high-tech glasses that could revolutionize the way we live, learn, and experience the world around us. If you ever come across someone working to make these dream glasses a reality, be sure to let me know. Because I would give anything to get my handson an invention like that! With those magical glasses, our lives and the boundaries of our imaginations would be limitless.篇2An Invention I Would Like to Make: A Special Kind of GlassesIf I could invent anything in the world, I would invent a really cool and awesome pair of glasses! These wouldn't be just any ordinary glasses though. My special glasses would have some extraordinary features that could help make the world a better place.First of all, my invention would allow the wearer to see through obstacles and other solid objects. With X-ray vision built right into the lenses, you could easily find lost objects or see what's inside things without having to break them open. Imagine being able to instantly locate your missing toy or see if there were any fun surprises tucked inside a present before opening it!But that's not all my miraculous spectacles could do. They would also give you the power of zoom vision, like a camera lens or binoculars. With a few blinks, you could zoom in on things that are really far away, bringing them up close for a better view. That means you could read the writing on a billboard fromblocks away or watch birds making their nests high up in the trees.My super glasses would even let you slow down time itself with their special slo-mo capability. Everything around you would start moving in slow motion, almost like being frozen, while you could move around at regular speed. That would be so handy for all sorts of things like dodging balls during gym class, pulling epic pranks on your friends, or just seeing how things look when slowed waaaaay down.Another awesome feature would be the ability to see infrared and ultraviolet light that is normally invisible to human eyes. With infrared vision, you could easily spot warm-blooded animals hiding in bushes or see which parts of a building aren't insulated properly. UV vision would let you see rays from the sun that cause sunburns, which would be really cool for science projects about the effects of different light waves.Of course, no pair of super glasses would be complete without night vision for seeing clearly in total darkness. That way you'd never need a flashlight to find your way around at night. You could have secret night adventures exploring the backyard and woods without waking your parents. Or read under the covers without getting caught!Heat vision would be another epic ability built into my invention. Similar to infrared, it would allow you to detect heat signatures and see things that are hot or cold compared to the surrounding area. You could find hot spots in electrical wiring before anything catches fire. Or easily locate buried gems, energy sources, or meteor impacts since they retain or give off heat. That would be amazingly useful for so many things!With all of these superpowers combined into one pair of glasses, I could become a pint-sized science detective or kid explorer extraordinaire! I'd be able to see the world in entirely new ways and make all sorts of crazy discoveries. Losing toys and belongings would be a thing of the past. I could inspect anything from the inside out without damaging it. And who knows what kinds of mysteries and secrets I might unveil with my super vision?!Just imagine how helpful these glasses would be for policemen, detectives, scientists, mechanics, archaeologists, and anyone else who needs to investigate things closely. They could aid in search and rescue efforts, finding missing people and items in no time. Contractors could use the X-ray feature to easily locate problems areas inside walls. Scientists couldobserve animals without disturbing them. Really, the possibilities would be endless!Creating an invention like this would require figuring out lots of difficult technology and engineering challenges. Things like powering all of those special vision modes, fitting them into a compact and durable design that's easy to wear, and maybe even adding voice commands or virtual displays. It would take a lot of hard work and perseverance to make it all come together flawlessly. But that just makes the idea even more exciting to me!Some people might be concerned about potential downsides of super vision glasses, like invasion of privacy or using them irresponsibly. Those would definitely be important considerations to think through carefully. Maybe there could be settings to turn off certain capabilities in specific areas or situations where they shouldn't be used. And definitely some rules about respecting people's privacy. As long as the glasses were used responsibly and ethically, though, I believe the positive benefits would far outweigh any negatives.In the end, my dream invention of multi-vision glasses could revolutionize how we perceive and interact with the world around us. With such an incredible tool at our disposal, just imagine what we might discover or achieve! Who knows, maybethey could even help solve some of the big problems facing our planet, like locating new energy sources or protecting endangered species. If I could make them a reality, it would be like giving everyone their own superpowers. Now how unbelievably cool would that be?!篇3The Glasses I Want to InventDo you ever wish you had special glasses that could do amazing things? I sure do! I've been thinking a lot about inventing a really cool pair of glasses. These wouldn't be ordinary glasses to help you see better. No, my invention would give glasses abilities that are totally out of this world! Let me tell you all about the incredible features I'd include.First of all, my glasses would let you see through anything. That's right - anything at all! Walls, floors, ceilings, you name it. With x-ray vision built right into the lenses, you could look inside closets, cabinets, boxes, purses, and every other container or concealed space. No more having to search forever when you misplace something - just slip on the x-ray specs and locate it instantly!But x-ray vision is just the start. These super glasses would also allow you to zoom in on faraway objects. Imagine being able to read the tiniest print from across the room or see the details on a bird perched on a high branch. The zoom capabilities would be so powerful, you could even see things on the moon up close! Just twist a little knob on the frames and zoom in as much as you need.My invention would include night vision too. The lenses would pick up infrared light, letting you see clearly even in total darkness. No more fumbling around and bumping into things at nighttime or in dark closets and basements. The night vision mode would make everything easily visible, just like during the day. You'd never be afraid of the dark again!Speaking of cool night vision tricks, the glasses would also have a thermal imaging function. This would make warm objects show up in different colors based on their temperature. You could actually see heat signatures of people, animals, computers, ovens, or anything else that gives off heat. Wouldn't that be such a neat effect?Besides all those awesome vision upgrades, my glasses would have some other amazing features too. Like built-in camera and video capabilities to snap pictures or recordhands-free video at any time. Or voice control to adjust the settings by simply speaking。

陨石撞地球英语作文简单

陨石撞地球英语作文简单

陨石撞地球英语作文简单Title: A Close Encounter: When a Meteorite Strikes Earth。

Introduction:The universe is an awe-inspiring expanse, filled with celestial bodies ranging from distant stars to wandering asteroids. Occasionally, these cosmic travelers venture too close to home, leading to dramatic events like meteorite impacts on Earth. In this essay, we delve into the phenomenon of meteorite impacts and their implications.What is a Meteorite?A meteorite is a solid piece of debris from an object such as a comet, asteroid, or meteoroid that survives its passage through Earth's atmosphere and lands on theplanet's surface. These fragments can vary in size fromtiny grains to massive boulders weighing several tons. Whenthey collide with Earth, they can cause significant damage depending on their size and velocity.The Impact Process:When a meteorite enters Earth's atmosphere, it encounters resistance from air molecules, causing it to heat up and glow brightly, creating a spectacular sight known as a meteor or shooting star. Most meteoroids burn up completely during this fiery descent, never reaching the surface. However, if the meteorite is large enough and robust, it can withstand the intense heat and pressure, making it through to impact the Earth's surface.Consequences of Impact:The consequences of a meteorite impact can be profound, ranging from localized destruction to global cataclysms. Small meteorites may create impact craters and cause minimal damage, while larger ones can unleash devastation on a much grander scale. Historical records and geological evidence indicate that several mass extinction events inEarth's history, including the demise of the dinosaurs, may have been triggered by massive meteorite impacts.Scientific Importance:Despite the potential for destruction, meteorite impacts also present invaluable scientific opportunities. The study of meteorites provides insights into the composition and evolution of our solar system. By analyzing the chemical and isotopic signatures of meteorites, scientists can unravel the mysteries of planetary formation and early solar system dynamics.Mitigation and Preparedness:Given the potential threat posed by meteorite impacts, scientists and policymakers are actively engaged in efforts to mitigate the risks and enhance preparedness. Advanced telescopes and monitoring systems are deployed to track near-Earth objects (NEOs) and identify potential impact threats well in advance. Additionally, international collaborations facilitate the development of strategies fordeflecting or intercepting incoming asteroids or comets, thus reducing the likelihood of catastrophic impacts.Conclusion:In conclusion, meteorite impacts represent afascinating yet potentially hazardous aspect of our dynamic universe. While these cosmic collisions have shaped Earth's history and continue to pose risks to our planet, they also offer valuable opportunities for scientific discovery and exploration. Through continued research, vigilance, and collaboration, we can better understand and mitigate the impact of these celestial visitors, ensuring the safety and resilience of our planet for generations to come.。

雅思考试阅读常见题材-11自然 detection of a meteorite lake

雅思考试阅读常见题材-11自然 detection of a meteorite lake

Detection of a meteorite LakeA A s the sun rose over picturesque Lake Bosumtwi, a team of SyracuseUniversity researchers prepared for another day of using state-of-the-art equipment to help unlock the mysteries hidden below the lake bottom.Nestled in the heart of Ghana (加纳）,the lake holds an untapped reservoir of information that could help scientists predict future climate changes by looking at evidence from the past. This information will also improve the scientists’understanding of the changes that occur in a region struck by a massive meteorite (陨石）.B T he project, led by earth sciences professor Christopher Scholz of the Collegeof Arts and Sciences and funded by the National Science Foundation (NSF), is the fi rst large-scale effort to study Lake Bosumtwi, which formed 1.1 million years ago when a giant meteor crashed into the Earth’s surface. The resulting crater is one of the largest and most well-preserved geologically young craters (火山口）in the world, says Scholz, who is collaborating on the project with researchers from the University of Arizona, the University of South Carolina, the University of Rhode Island, and several Ghanaian institutions. “Our data should provide information about what happens when an impact hits hard, pre-Cambrian (前寒武纪),crystalline rocks (结晶岩）that are a billion years old, he says.C E qually important is the fact that the lake, which is about 8 kilometers indiameter, has no natural outlet. The rim of the crater rises about 250 meters above the water’s surface. Streams flow into the lake, Scholz says, but the water leaves only by evaporation, or by seeping through the lake sediments.For the past million years, the lake has acted as a tropical rain gauge (测量器）,fi lling and drying with changes in precipitation and the tropical climate.The record of those changes is hidden in sediment below the lake bottom. “The lake is one of the best sites in the world for the study of tropical climate (热带气候)changes,” Scholz says. “The tropics are the heat engine for the Earth’s climate. To understand global climate, we need to have records of climatechanges from many sites around the world, including the tropics.”D B efore the researchers could explore the lake’s subsurface, they needed aboat with a large, working deck area that could carry eight tons of scienti fi c equipment. The boat—dubbed R/V Kilindi—was built in Florida last year. It was constructed in modules that were dismantled, packed inside a shipping container, and reassembled over a 10-day period in late November and early December 1999 in the rural village of Abono, Ghana. The research team then spent the next two weeks testing the boat and equipment before returning to the United States for the holidays.E I n mid-January, fi ve members of the team—Keely Brooks, an earth sciencesgraduate student; Peter Cattaneo, a research analyst; and Kir am Lezzar, a postdoctoral scholar, all from SU; James McGill, a geophysical fi eld engineer;and Nick Peters, a Ph.D. student in geophysics from the University of Miami—returned to Abono to begin collecting data about the lake’s subsurface using a technique called seismic re fl ection pro fi ling. In this process, a high-pressure air gun is used to create small, pneumatic explosions in the water. The sound energy penetrates about 1,000 to 2,000meters into the lake’s subsurface beforebouncing back to the surface of the water.F T he reflected sound energy is detectedby underwater microphones—calledhydrophones—embedded in a 50-meter-long cable that is towed behind the boat asit crosses the lake in a carefully designedgrid pattern. On-board computers recordthe signals, and the resulting data are thenprocessed and analyzed in the laboratory.“The results will give us a good idea ofthe shape of the sediment are, and whenand where there were major changes insediment accumulation,” Scholz says. “Weare now developing three-dimensional perspective of the lake’s subsurface and the layers of sediment that have been laid down.”G T eam members spent about four weeks in Ghana collecting the data. Theyworked seven days a week, arriving at the lake just after sunrise. On a good day, when everything went as planned, the team could collect data and be back at the dock by early afternoon. Except for a few relatively minor adjustments, the equipment and the boat worked well. Problems that arose were primarily non-scientific— tree stumps, fishing nets, cultural barriers, and occasional misunderstandings with local villagers.H L ake Bosumtwi, the largest natural freshwater lake in the country, is sacred tothe Ashanti people, who believe their souls come to the lake to bid farewell to their god. The lake is also the primary source of fi sh for the 26 surrounding villages. Conventional canoes and boats are forbidden. Fishermen travel on the lake by fl oating on traditional planks (木板）they propel with small paddles (船桨）.Before the research project could begin, Scholz and his Ghanaian counterparts had to secure special permission from tribal chiefs to put the R/V Kilindi on the lake.I W hen the team began gathering data, rumors (谣言）fl ew around the lake asto why the researchers were there. “Some thought we were dredging the lake for gold, others thought we were going to drain the lake or that we had bought the lake,” Cattaneo says. “But once the local people understood why we were there, they were very helpful.”Questions 14-18 .............................................................................Do the following statements agree with the information given in Reading Passage 1?In boxes 14-18 on your answer sheet, writeTRUE if the sataement agrees with the informationFALSE if the statement contradicts the informationNOT GIVEN if there is no information on this14W ith the analysis of the bottom of the lake, scientist will predict the climate changes in the future.15T he water stored in lake Bosumtwi was gone only by seeping through the lake sediments.16T he crater resulted from a meteorite impact is the largest and most preserved one in the world.17H istorical climate changes can be detected by the analysis of the sediment of the lake.18R esearch of scientist and co-workers had been interfered by the locals due to their indigenous believes.Questions 19-22 .............................................................................There are three steps of collecting data from the lake as followings, please filling the blanks in the Flow Chart below:Step 1a 50-meter 19 ,with many 20embededStep 2a 21 isneeded to create theexplosion into thewaterStep 3the 22enters deep intothe water andreturn backQuestions 23-27 ............................................................................. SummaryComplete the following summary of the paragraphs of Reading Passage, using no more than three words from the Reading Passage for each answer. Write your answers in boxes 23-27 on your answer sheet.The boat-double R/V Kilindi crossed the lake was dismantled and stored in a 23. The technology they used called 24; They created sound energy in to 1000-2000 metres in to the bottom of the lake, and used separate equipment to collect the returned waves. Then the data had been analyzed and processed in the 25. Scholz also added that they were now building 26view of the sediment or sub-image in the bottom of the lake. Whole set of equipment works well yet the ship should avoid tree stumps or 27fl oating on the surface of the Bosumtwi lake.。

流星是怎么回事英语作文

流星是怎么回事英语作文

流星是怎么回事英语作文In the vastness of the night sky, meteors often leave a beautiful and mysterious sight. Let's explore what exactly meteors are and how they occur.Meteors are small particles of cosmic matter that enter the Earth's atmosphere at high speed.When these particles collide with the atmosphere, they begin to heat up and produce a brilliant light, creating a streak of light in the sky.The speed at which meteors travel is extremely fast, reaching thousands of miles per hour.This high speed causes the particles to ionize the air around them, resulting in the visible light we see.Meteors can originate from various sources such as comets or asteroids.As these objects pass close to the Earth, they release particles that enter our atmosphere.The sight of a meteor is a random and unpredictable event, making each encounter a special and memorable moment.Observing meteors can be a breathtaking experience, especially during meteor showers when many meteors can be seen in a short period of time.Meteor showers are often associated with specific constellations and occur at specific times of the year.Studying meteors helps us better understand the universe and the processes that occur within it.It provides insights into the formation and evolution of celestial objects and the interactions they have with our planet.。