A LIGHT SCATTERING METHOD TO MEASURE REAL-TIME PARTICULATE EMISSIONS

Transcription

1 A Lght Scatteng Method to Measue Real-tme Patculate Emssons Rose Gong & Keyn Wllams 6 th Austalasan Tanspot Reseach Foum Wellngton New Zealand -3 Octobe 003 A LIGHT SCATTERING METHOD TO MEASURE REAL-TIME PARTICULATE EMISSIONS Rose Gong, Keyn Wllams School of Chemcal and Physcal Scences, Vctoa Unvesty of Wellngton, PO Box 600, Wellngton, New Zealand.. ABSTRACT Dynamc analyss of patculate emssons fom vehcles has been a challenge. A dynamc patculate measuement method applyng lght scatteng theoy s beng developed at Vctoa Unvesty. A patcle model has to be set to apply lght scatteng theoy. To smplfy the poblem, a Faunhofe dffacton model has been used. The scatteed lght ntenstes have been measued at dffeent scatteed angles fom the patcles n an exhaust steam wth a lock-n amplfe system, and then the scatteed lght ntenstes wee used n the model to solve the patcle sze dstbutons. Snce the model equatons ae non-lnea, analytcal solutons cannot be obtaned easly. The fst dak ng theoy was appled ntally to ovecome nonlneaty. Howeve ths method ove estmates small szed patcles. To solve the non-lnea equatons, numecal calculatons based on the least squaes method wee caed out. Fstly we woked on numecal calculatons wth the scatteed lght ntensty-scatteed angle pofles poduced by a sngle detecto measuement system. Dffeent sze goups have been chosen fo the calculaton. Reasonably good ageement was obtaned wth the dffeent choces. Secondly, we modfed the optcal desgn of the lght ntensty measuement, n patcula, fo lage angle aea, whch the scatteed lght s much weake than that n the small angle aea. Optcal lenses wee ntoduced n the system. Ths modfed desgn has nceased the sgnal qualty of lage-angle scatteed lght ntensty sgnfcantly, and enables us to take eal-tme measuements fom dynamc patculate emssons. Howeve usng lenses deceases the numbe of data ponts used n the numecal calculatons.. INTRODUCTION Patculate emssons fom desel vehcles have been ecognsed as a sgnfcant souce of suspended patculate matte n the atmosphee. In uban aeas the popoton of desel patcle matte n the atmosphec patculate matte s hghe than non-uban aeas, f the patculate matte fom natual souces s excluded. Fo example, a epot of U.S. EPA (Envonmental Potecton Agency) [] showed that the estmated ange of desel PM.5 contbuton to the total nventoy was fom 0% to 3% n some uban aeas n Calfona, Coloado and Azona. Desel patculate emssons can have seous mpacts on human health. Chambellan and colleagues [] explaned the effects of desel patcles on asthma and allegc hnts. Studes caed out n US [, 3, 4] and n Euope [5] showed that desel patcles wee elated to espatoy dseases, n patcula, lung cance, and nceased motalty and mobdty. The fne the patcles, the lage the suface aea whee chemcals can attach, and the deepe they can penetate nto the espatoy system. Desel exhaust patcles can also contbute to clmate change. The black cabon patcles not only Page

2 A Lght Scatteng Method to Measue Real-tme Patculate Emssons Rose Gong & Keyn Wllams have a wate nucleaton effect n the atmosphee causng nceased cloud fomaton [6], but they mght be patally esponsble fo the global wamng effect as well, accodng to Jacobson s eseach [7]. Desel patcles ae the poducts of ncomplete combuston. Desel patculate emsson s one of the mpotant paametes fo engne pefomance and engne combuston effcency. The physcal chaactestcs of desel patculate emssons vay unde dffeent opeatonal condtons. Fo example, the patcle sze ange and sze dstbutons and the mass of desel patcles wll change f an engne s unnng unde dffeent speeds o dffeent loads. Patculate emssons fom dffeent types of desel engnes ae vey dffeent. To undestand the physcal chaactes of desel patcles and how they change s vey mpotant fo the analyss of engne pefomance and ts effcency and fo the nvestgatons of the elatonshp between patcle sze and the ts effects on human health and clmate changes. So t s vtal to study the desel patculate emssons as a functon of vehcle type and engne opeatonal condtons, patculaly, tansent opeatng condtons. The analyss of eal-tme measuements of desel patculate emssons wll eveal the functon. In ecent yeas, much of the eseach wok on desel patculate emssons has been concentated on eal-tme measuements. The eal-tme measuement of collectve desel patculate emssons has been caed out n a mountan tunnel epoted by Cadle [8]. An nstument sampled the ambent a nsde the tunnel contnuously and measued the patcle sze. The chaactestcs of patculate matte (PM) emssons wee dffeent between heavy-duty desel vehcles and lght-duty desel vehcles. Indvdual vehcle s eal-tme patculate measuements on a chasss dynamomete wth a dluton tunnel ftted wth soknetc patculate samplng pobes wee epoted by Moosmülle and colleagues [9], who used fve dffeent methods to measue PM mass n a dvng cycle test. Expements on a smla dynamomete testng faclty wth a photomete wee caed out by Cheung [0] to measue the nstant PM mass unde defned speeds and tansent opeatng condtons. The esults showed that PM mass vaed wth changes of vehcle speeds, and at the begnnng of a speed change, the PM mass nceased. Howeve, the dluton tunnel samplng pocess could smooth out some shap changes. Both the mass and sze dstbuton of desel PM exhaust wll change f the vehcle opeatonal condton changes. In ode to obseve the changes of patcle sze dstbuton mmedately afte the exhaust ppe, a lght scatteng method s beng developed at Vctoa Unvesty of Wellngton, whch wll enable us to measue patculate emssons wthout dstubng them. It s ctcal to be able to measue patcle sze dstbutons emotely (open-path) dectly fom the exhaust ppe n ode to undestand the elatonshp of sze dstbutons and engne pefomances. When exhausts ae cooled down n a o n a dluton tunnel, thee s a chance that volatle compounds wll condense on the sufaces of the patcles, and that patcle aggegatons could be encouaged. Ths pape explans the ealy stage of the development of ths lght scatteng method, and dscusses the esults of dffeent methods of calculatng patcle sze dstbuton fom the scatteed lght measuements 3. LIGHT SCATTERING Patcles scatte lght when they ae n a lght beam. The patten of scatteed lght ntensty fom a patcle could be a functon of ncdent lght ntensty, the wavelength of the ncdent lght, scatteng angle, the sze and shape of the patcle and the efactve ndex. If the scatteed lght fom patcles can be measued, the patcle Page

3 A Lght Scatteng Method to Measue Real-tme Patculate Emssons Rose Gong & Keyn Wllams sze dstbuton can be obtaned by applyng the pope lght scatteng theoy o model and an appopate calculaton method. 3. LIGHT SCATTERING FOR SMALL PARTICLES Thee ae dffeent lght scatteng theoes fo dffeent lght scatteng poblems. In geneal, a patcle scattes lght as shown n Fgue, whee θ s the scatteng angle. It can be descbed by equaton () as gven n efeence []: θ I I o F( θ, ϕ) =, () k whee I o s the ntensty of ncdent lght, I s the ntensty of scatteed lght at a pont, whch s at a lage dstance fom the patcle, and k s the wave numbe defned by k = π/λ, whee λ s the wavelength of the lght. F(θ, ϕ) s a dmensonless functon of the decton of Fgue A patcle scattes lght scatteng, n whch ϕ s an azmuth angle. It also depends on the oentaton of the patcle wth espect to the ncdent lght and on the state of polasaton of the ncdent lght. F(θ, ϕ) can be defned n dffeent foms to deal wth dffeent scatteng poblems. The classc method to descbe the scatteng by a patcle, whose sze s n the same magntude as λ, o lage than λ, s Me scatteng theoy. In Me scatteng, scatteed lght wll be examned n two wave planes pependcula to each othe, and the ampltudes of the components of the scatteed lght ae the functon of the oentatons of detectng of scatteng n the two planes, the physcal appeaance of the patcle,.e. the shape and sze, and the composton of the patcle,.e. the efactve ndex. To apply Me theoy to desel patcle emssons s complex. Based on the eseach budget of ths poect, a modfed smple scatteng model has been chosen to test the pncple of measung the sze dstbutons of dynamc patcles emotely, befoe the moe sophstcated Me theoy s used. 3. OUR MODEL The model we used s not an accuate descpton of a eal desel patcle. The electonc mcoscope mage of eal desel patcles s shown n Fgue. Ou model descbes an dealsed patcle wth a smla physcal effect to the eal one. We teated the desel patcles as: Patcles fom the exhaust ae homogenous sphees; The szes of the patcles ae much geate than the wavelength of the ncdent lght; The ncdent lght s unpolased lght; Thee s suffcent oom between patcles, so the scatteng patten of each ndvdual patcle s undstubed by the pesence of othe patcles; Page 3

4 A Lght Scatteng Method to Measue Real-tme Patculate Emssons Rose Gong & Keyn Wllams The thckness of the exhaust cloud n the lase beam s so small compaed wth the dstance between the exhaust and the detecto that the thckness s neglgble. All of the scatteng souces come fom the same ogn. Lght scatteng of ou model then can be descbed by Faunhofe dffacton as explaned by van de Hulst []. The lght scatteng patten of a sngle patcle descbed by Faunhofe dffacton theoy s shown as, Fgue Electonc mcoscope mage of desel patcles I( α, θ ) I ( α, θ ) = = I o x J( xsnθ ) xsnθ k () whee k = π / λ, and x = kα. I : I : I o : λ : : α : θ : J : Relatve ntensty of scatteed lght; Intensty of scatteed lght; Intensty of ncdent lght; Wavelength of the ncdent lght; Dstance fom the patcle to the detecto; Radus of the patcle; Scatteng angle; Bessel functon ( st ode). In a desel exhaust cloud, thee ae N patcle wth adus α. N(α ) s the patcle sze dstbuton of the desel exhaust, and the total scatteed lght of the exhaust patcles at scatteng angle θ s I θ = I ( α, θ ) N( α ). (3) s(θ) s the measued scatteed lght ntensty sgnal at θ, then s ( θ ) = Iθ = I ( α, θ ) N( α ). (4) If the scatteed lght ntensty s measued at n scatteng angles, the followng set of equatons can be obtaned: s ( θ ) = Iθ = I ( α, θ ) N( α ), =,,.m. (5) Page 4

5 A Lght Scatteng Method to Measue Real-tme Patculate Emssons Rose Gong & Keyn Wllams α and N(α ) ae both unknown, so equatons (5) ae a set of nonlnea equatons. Once those equatons ae solved, the patcle dstbutons wll be obtaned. 3.3 FIRST LIGHT SCATTERING EXPERIMENT A lase lock-n amplfe detectng system was bult to wok wth a VM 9 twocylnde desel engne to measue the scatteed lght fom desel exhaust as t was descbed n ou eale pape [], and ts schematc dagam s shown n Fgue 3. The lght souce s a 484 nm agon lase wth the capablty of 00 mw powe output. The detecto was wokng togethe wth a lock-n amplfe to elmnate stay lght and the ambent backgound lght, because the detecto woked unde outdoo open atmosphee Engne Exhaust Ppe condtons, and the sgnals fom the scatteed souce wee vey weak compaed to Lase Io daylght. The θ scatteed lght ntensty was ecoded by a Detecto Unt laptop compute wth 0.5 to degee ncement along Data Acquston Compute Fgue 3 Schematc dagam of lght scatteng expement the scatteng angle fom 0 o up to 5 o. A typcal measued scatteed lght pofle s shown n Fgue 4..00E-0.00E-0.00E-03 I.00E-04.00E-05.00E Angle (degee) Fgue 4 Scatteed lght pofle of desel exhaust Page 5

6 A Lght Scatteng Method to Measue Real-tme Patculate Emssons Rose Gong & Keyn Wllams 4. CALCULATION METHODS TO OBTAIN N(a ) Thee ae no analytcal solutons fo equatons (5). Ethe addtonal condtons ae ntoduced, o numecal calculaton s used to solve those equatons. The fst method was used s Fst Dak Rng (FDR) method. The second one s a numecal method to solve the nonlnea equatons. 4. THE FDR METHOD The FDR method eques addtonal nfomaton to calculate the patcle sze dstbuton N(α) fom equaton (4). In ths secton, the featues of the scatteed lght patten of a sngle patcle ae analysed 3.00E-08.50E-08.00E-08.50E-08.00E-08 5 mm and used n the 5.00E-09 FDR calculaton fo N(α). The patten of scatteed lght ntensty of a patcle s expessed by equaton Degee 0.00E (). The ntensty of the scatteed lght vaes wth scatteng angles. Fgue 5 Scatteng patten of a sngle patcle When the lght ntensty s hgh, t appeas bght and foms a bght ng. When the lght ntensty s low, t s dak, and foms a dak ng. Fgue 5 shows the scatteed lght patten of a 5 µm patcle as an example. Howeve, at the fst dak ng, the adus α of a patcle and the scatteng angle θ d of ts FDR follow α 3.83λ = π sn. (6) θ d We assume that the ntensty of the scatteed lght of a patcle at θ < θ d compang wth that wthn the FDR can be neglected. Based on ths assumpton, an algothm fo calculatng patcle sze dstbuton N(α) s outlned as follows:. The smallest dentfed adus α o of the patcles s detemned by the scatteed angle θ o, fom whee s(θ) becomes constant o 0.. Set the adus ncement α of patcles, so the next consdeed patcle sze s α = α o + α. 3. The FDR of patcle α s at 3.83λ θ = sn ( ). πα Relatve Lght Intensty Page 6

7 A Lght Scatteng Method to Measue Real-tme Patculate Emssons Rose Gong & Keyn Wllams 4. The numbe of patcles α 0, N 0 can be calculated fom the measued sgnal, snce the scatteed lght ntensty at θ s contbuted by patcles α 0 accodng to the assumpton. Theefoe, s( θ) N o =. I ( α, θ ) 5. N can be calculated at θ, the FDR of patcle α : s( θ ) N oi ( α o, θ ) N =. I ( α, θ ) o 6. So, fo patcle α, and α = α - + α, then N = θ 3.83λ = sn ( ), πα s( θ + ) N k = 0 I ( α k, θ k I ( α + ) k, θ + ). N(α) wll be obtaned, when the calculaton along s(θ) s completed. The calculatons nvolved n ths algothm ae vey easy, and can be caed out by seveal commonly used Mcosoft-Wndow s pogammes. Howeve ths method oveestmates small patcles because the assumpton neglects the scatteed lght ntensty afte the FDR. So the scatteed lght ntensty afte the FDR of each patcle would be collected by the smalle patcles. The esult by usng ths method wll be pesented and dscussed n Results and Dscusson Secton. 4. THE LEAST-SQUARES METHOD To avod the assumpton stated n the last secton, the nonlnea equatons (5) at the measuement ponts s(θ ) should be used. Snce the analytcal solutons could not be calculated, we have to use numecal methods to solve the set of nonlnea equatons. In equatons (5), both patcle sze α and patcle numbe N ae vaables. If thee wee K bns n ou patcle sze dstbutons, we would have K of vaables, and n theoy, K data ponts would be needed to solve the equatons. The numecal method we use s fo optmsaton poblems, whch s one of the commonly used methods to solve nonlnea equatons (See efeence [3]). The type of the functon we tageted fo optmsaton s nonlnea least-squaes. The obectve functon fo calculaton s the sum of squaes of nonlnea equatons. The pncple of ths calculaton s to educe the dffeences between measued values of scatteed lght and the values of scatteed lght poduced by the estmated patcle dstbutons. So, n ths pactce, ou optmsaton s a mnmsaton poblem. It has the fom of: Page 7

8 A Lght Scatteng Method to Measue Real-tme Patculate Emssons Rose Gong & Keyn Wllams m mn F( y) = mn f ( y) (6) = whee y = (y, y,., y n ) T, and m > n. n s the numbe of vaables, and m s the numbe of equatons. Rewte equatons (5), I ( α, θ ) s ( θ ) Iθ = s( θ ) N( α ), =,,.m. The functon n equaton (6) becomes and K I ( y, yk + f ( y) = s( θ ) Iθ = s( θ ) θ ), =,,.m. m = K F( y) = [ s( θ ) I ( y, θ ) y ]. K + The value of m depends on the measued data ponts, and K s the numbe of sze goups (o bns) n the estmated sze dstbuton calculated. In ou case, n = K. The numecal calculaton pogamme codes n FORTRAN poduced by Numecal Algothms Goup (NAG) wee used to cay out the calculatons. The least-squaes method can avod oveestmatng small patcles when calculatng the sze dstbutons. Howeve, how detaled (how many szes) sze dstbutons that can be acheved ae lmted by the numbe of data ponts obtaned fom lght scatteng expements, and the moe sze goups (sze bns) wee n the functon, the longe calculatng tme t would need to each a soluton. 5. RESULTS AND DISCUSSION Expements of the lght scatteng fom desel patcles wee caed out on the faclty descbed n secton 3.3. The scatteed lght sgnals wee measued fom 0 o up to 5 o by sweepng the detecto am along the angles. The movements nvolved n the lght scatteng measuements equed pecson, but the envonment close to the engne was vey nosy wth vbaton. It was a vey delcate opeaton, equng a geat deal of pepaaton and patence to get a easonable scatteed lght pofle. The scatteed lght pofle obtaned wth an engne speed 000pm shown n Fgue 4 was used n these two dffeent calculaton methods fo ths pape. The esults of these two calculaton methods wee compaed wth the sze dstbuton obtaned by mcoscopy. In ode to cay out ths compason, desel exhaust samples wee taken by puttng clean mcoscope sldes nto the exhaust plume whle the scatteed lght measuement was caed out. The sample sldes wee pepaed and gold coated, then studed n a Scannng Electon Mcoscope (SEM). Images taken by SEM wee analysed by an mage pocessng compute pogamme. The sze of patcles on the sldes was measued, the numbe of patcles was counted, and the sze dstbuton was poduced by the pogamme. Fgue 6 shows the patcle sze dstbuton on the desel patcle sample slde. The two calculaton methods Page 8

9 A Lght Scatteng Method to Measue Real-tme Patculate Emssons Rose Gong & Keyn Wllams dscussed above wee used to calculate patcle sze dstbutons fom the same scatteed lght pofle. The esults fom the calculatons and fom SEM mage analyss ae shown n Table Numbe n % Patcle damete n mm Fgue 6 Patcle sze dstbuton fom SEM mage In Table, the data unde SEM, ae fom the SEM mage; the data unde FDR ae the esult calculated by FDR method, and those unde Least-squaes ae the esult obtaned by least-squaes numecal calculaton. The sze expessed n the table s Table SEM FDR Lesat-squaes Sze N% Sze N% Sze N% the damete of patcles, n µm. The numbe of patcles at each sze ange s pesented n pecentage to the total numbe of patcles. All of the thee data sets n Table show that most of the patcles fom the desel exhaust ae small patcles, <.5 µm, and vey small amount of elatvely lage patcles, no lage than 50 µm. In the smalle sze ange, e.g. unde.8 µm, nealy 60% of the patcles wee counted fom the SEM mage; the Least-squaes esult shows about 80% n ths ange, whle the esult fom FDR s ove 90% at. µm only. As t was pedcted befoe, the FDR method would ove estmated small patcles, and t does not show any patcles lage than 5 µm, but both SEM mage and Least-squaes esults show the occasonal lage patcles pesent n the desel sample. The SEM mage shows thee s a small peak, moe than 0% at nea 5 µm egons n ts sze dstbuton. Both of the calculated esults do not have ths peak n a smla Page 9

10 A Lght Scatteng Method to Measue Real-tme Patculate Emssons Rose Gong & Keyn Wllams egon. The Least-squaes esult shows a small ncease at about 8 µm and the FDR esult has an even weake ncease at nea 7 µm. Fgue 7 shows the same sets of esults n accumulatve dstbutons. All thee esults have the same tend of the sze dstbuton. Oveall, Least-squaes esult s close to that deved fom the SEM mage than FDR esult. The popoton of small patcles n FDR Accumulatve pecentage of patcle numbe 0.9 esult s clealy moe than those n the othes. 0.8 Seven sze SEM Image goups wee the best choce we 0.7 FDR Least-squaes could do wth the Least-squaes 0.6 method due to the numbe of 0.5 expemental data ponts. The 0.4 lmt of choces of patcle szes Patcle damete n mm made the Fgue 7 Compason of accumulatve pecentages of patcle appoach to the numbe eal dstbuton less easy than t could have been. Apat fom ths weakness of Less-squaes calculaton and the addtonal assumpton made n the FDR method, thee s a common aspect fo those two calculatons not to have same detaled featues n the sze dstbutons as the SEM mage, that s the accuacy of scatteed lght sgnal measuements n the elatve lage angle ange. The dffeence between the sgnal levels fom a small angle to a elatvely lage angle, > 0 o, was moe than 0,000 tmes. A sngle detecto system could not keep the same senstvty wthn such a lage ange of the sgnal level. The sgnals measued n the lage angle ange had a elatvely hgh nose level, whch dectly affected the esults fo small patcles patculaly. Howeve, the lght scatteng method has shown encouagng esults, and to ncease the accuacy of scatteed lght measuements, the expemental system eques mpovements. 6. IMPROVEMENT IN EXPERIMENT AND FUTURE WORKS The followng mpovements n the expemental system have been made: A mult-detecto system has been desgned, so all of the scatteed sgnals can be ecoded at the same tme. Unexpected dstubance fom the backgound can be lmted, and nstantaneous measuements can be caed out easly. Lenses ae used fo each detecto to ncease the scatteed lght ntensty. In patcula, the qualty of scatteed lght sgnals n the lage angle egon has been sgnfcantly mpoved []. A mult-channel lock-n amplfe and synchonsed data contolle system s used. Page 0

11 A Lght Scatteng Method to Measue Real-tme Patculate Emssons Rose Gong & Keyn Wllams The mpoved system, whch s shown n Fgue 8, s moe obust than the pevous one. Lght scatteng expements wth unnng engne can be caed out easly and quckly. The scatteed lght fom evey angle can be ecoded at same tme. It s a eal-tme spontaneous measuement. Ths system s one step close to a eal-wold vehcle testng system Snce the system of the measuements of lght scatteng has been changed, the qualty of sgnals has been geatly mpoved. Unfotunately as a consequence of usng lenses the numbe of data ponts s less than befoe, as a lens coves a ange of scatteng angles. The obectve functon n the method to solve non-lnea equatons wll theefoe have to be changed. Othe numecal methods athe than the Least-squaes method wll be Fgue 8 The mpoved system analysed and tested, snce the Leastsquaes method s no longe appopate to solve sze dstbutons fom the data obtaned fom the new sgnal collectng system. A moe compehensve desel patcle model should also be nvestgated. The shape facto as well as the fne patcles should be consdeed n futue models. The szes of the fne patcles ae compaable to the wavelength of the ncdent lght. In the futue, the appopate numecal method and a compehensve patcle model wll fom a new softwae package. Once the scatteed lght of patcles fom an exhaust ppe s ecoded, ths softwae wll poduce the sze dstbuton. So the expements wth dffeent desel engnes, unde dffeent opeatonal condtons can be undetaken. In patcula, the capablty of the lght scatteng method to measue patcle szes dung engne s tansent opeatons should be assessed. 7. ACKNOWLEDGEMENTS Fundng assstance fom the Publc Good Scence Fund of the New Zealand Govenment s gatefully acknowledged. Beaglehole Instument desgned and bult the mult-channel lock-n amplfe system to mpove the qualty of the expements. 8. REFERENCES. Natonal Cente fo Envonmental Assessment Offce of Reseach and Development, Health Assessment Document fo Desel Engne Exhaust, EPA/600/8-90/057F, May 00. Chambellan, A, Cestan, B. Sole P., Moeau, J., Aube, M., Desel Patcles and Allegy: Cellula Mechansms, Alleg Immunol (Pas), 000, Feb. 3():43-8, Unque dentfe: AIDSLINE MED/ Smth, R.; Davs, J.M.; Sacks, J.; Speckman, P.; Stye, P. Envonmentcs 000,, Mchaels, R.A.; Klenman, M.T. Aeosol Sc. Technol. 000, 3, Page

12 A Lght Scatteng Method to Measue Real-tme Patculate Emssons Rose Gong & Keyn Wllams 5. Seethale R. Economc Costs of A Polluton-elated Health Impacts - an Impact Assessment Poect of Austa, Fance and Swtzeland, Poceedngs of 6 th Intenatonal Clean A and Envonment Confeence of the Clean A Socety of Austala & New Zealand, Chstchuch, New Zealand, 9- August Lammel, G.; Novakov, T., Wate Nucleaton Popetes of Cabon Black and Desel Soot Patcles, Atmosphec Envonment, 995, 9, (7), Levy, D., Desel Soot Added to Lst of Global Wamng Culpts, Stanfod Repot, Dec., Cadle, S.H.; Gose, R.A.; Baley, B.K. and Lawson, D.R., Real-Wold Vehcle Emssons: A Summay of the 0 th Coodnatng Reseach Councl On-oad Vehcle Emssons Wokshop, ISSN Jounal of the A & Waste management Assocaton, 00, 5: Moosmülle, H.; Anott, W.P.; Roges, C.F., et al, Tme Resolved Chaactezaton of Desel Patculate Emssons.. Instuments fo Patcle Mass Measuements, Envonmental Scence & Technology, 00, 35, No 4, Cheung, S.K.; Elde, S.T.; Ran, R.R., Desel Patculate Measuements wth a Lght Scatteng Photomete, SAE Techncal Pape Sees, Gong, R., Analyss of Optons fo Inceasng the Senstvty of a Lght Scatteng Method fo Measung the Sze Dstbutons of Desel Patculate emssons, Poceedngs of 4 th Wold Congess on Patcle Technology, 00, Sydney, Austala, ISBN van de Hulst, H.C., Lght Scatteng by Small Patcles, publshed by John Wley & Sons, Inc NAG Manual, Fotan 77 Lbay, Mak 9. Page