Document wrz5oM8N1apnGjkJGdj91NYgd

: pyM.^ Hpt ^ pp^ ^ gy y i w !w;pB| np. in .m^..n. ^|,^i!i/i.|!, .,., u, p-yiiwj^ r w^qwBfg^y w ii ffj l^- l^ nl>^-^^^nJ ^ l RESIAJCH PROGRAM PKS8BRATZOI ATJceramc k k h ah zs m urzcnvi a scAvraaxm l ead azf o 60L8 ajrelin lb* objective of thl research prcgr+m 1* to describe tn quantitative tm tb# aechanltas which aa-a Important In thd raeoval of laad aaroaol* froa the atmosphere, to provide i i Uia Ui of their effectiveness, nod to relate tbeee rsaaovul Bechenlan* to urban land serceol Missions. Bk w 1 Zt la obvious that tb* atnoaphara baa various natural aachanlsrs which act to cleanse It of lspurltlaa, both particulate and gaseoua. If thla wara not ao, coodlttooa long ago would haru passed bayood tolarabla levala oo a world-wide seal*. Iha varloua physical aachanlasa active In tba atmosphere for rtnovlng partlculata natarlala Include: (1) settling or fallout, (2) rainout through condensation procaataa, (3) waahout by droplet scrubbing action, and (*) lspactlon oo solid aurfacaa. Thaat varloua mechanises hava baan carafully atudlad In tha paat for varloua natarlala and specially with rafaranca to nuclear fallout frca weapons Uiti. To apply tb**a prlnclplaa to laad aaroaola will require first a consideration of raallatlc aerosol and ateoapharlc eoviraaeectel factor*. Than calculations can bn aada of tha bshavlor of tha laad aerosol for choaan atmospheric and topographic condltloca. Proa thaaa calculations tons raallatlc utLsaUi can bn aada of tha affactlvanaaa of tha atjkospharlQ rsaseval mechanism* for laad aerosols. Research oo ataoepherle scavenging mechanics directly ralatad to laad aerosols can now bn undertaken vlth sane degree of confidence la tha applica bility and usefulness of tba rnsult to urban araaj bacauaa of tha knowledge obtained In previous ranarch by tha Znatltuta oo tha alas distributions of tha urban laad aaroaol. Zt also some qulta 111aly that thla raaaarch progran would be as Informative prograo, c<srpl*m*trtary to tha vsevtatloo dapoaltloo stadias being doce by Z.A. Schuck at the Uiirarvity of California, Riverside. Previous raiaarch work by Cttnford Raaaarch Znatltuta has Indicated that tha urban atmospheric laad aerosol has a ala# distribution which doe* not chang* oarbadly over a wtd# range of locations. A rsprasantatlv# 41*trl- bution bean *hxwr to ham ?pt of tha a*** trailer than 0.16 equivalent diameter, yA lei* ts*n 0.23 , and ?pi larger than 0.1*3 . Thla sld*~dis tribution appe*."* to be generally applicable to a mi-.her of California, mid- western, x~.1 a*, stern W.9. ur'.an area*. It therefore unnecessary at thla the* to cover a v|d* rug* vf partlr'ilat* lte rtlst*i>jtt<'o In any experi mental precraa dealing with ! raew/va.I pr,-'**, Ikvever, at *<* future 11c* tha nature of lvt parti<-ui*t* In a<ir* rraot# art** miy require consider ation of a breeder rang* of alt* distribution*. As nenllc/'t.t bn for#, **Ultng 1* one of the mechanlsa* which should be ceauldarad when studying tha proc**# by vt.Irh lied l**v#s tha atarephar*. If tha aattllng vara solely controlled by gravitational and viscous affect# we vould expect thel pertU 1st would pa** to tha ground at tha Otokaa- 'spans ... ................. " .Iiiwfwjj.- nr, mm....im .w.i .m&vum;#* - r - Cusnlnghui settling velocity, which for a 0.2? particle i about 0.001 ca/sec. ThlM very *-*ii settling velocity it often ignored in diffusion estlsate* of ataospherlo concentration because whether or not it it included nabes little difference in the flwU. calculation. However, there it considerable evidence that the Stokei-Ojnnlngbaa velocity it Dot the factor which tbould he rued to estlsate the deposition of tubedcron particles frea the ataoephere. A.C. Checheriain Hrat defined amt Matured what he cellt a velocity of depoei- Hoc; atmospheric dlffutlcc fcrculat have been derived to incorporate thle factor. /Ta theta formulas, downwind depoeltioo and coocentratloc anountt for aoderate downwind ranges can be calculated bated on source conditlont, eeroeol characterletlet, and the nature of the surface. ChanterIain's velocity of depoeltioo cannot be calculated but xust be detendned experimentally for different surfaces. Qanberlain hat Measured the deposition velocity of uranluo fuse, 0.2 disaster, onto grass and ob tained a value of about 0.2 ca/sec. Thit it larger than the calculated tertdnal velocity by etleeet'2 orders of cagnltude and vculd be an irpcrtaat factor to be Included in estimates of atcospberlc depoeltioo of this aaterlal. tepoeltlco rates were also dependent oo the nature of the surface, l.t., a grass surface had a different depoeltioo rate than a flat filter paper. Thle type of behavior say also be true of lead aerosols in this general site range. Aerosols are also soilfled and scavenged frcei the etaospbsre by oosgulatlcn, rainout, and washout processes. These processes hare been ehcam to be Important factors in deleraining the atnospheric cycles of other aerosols such as sulfates and uuclaar debris, and it is expected that these processes can be shown Vo be effective in modifying and removing urban lead aerosols fWa .j the ataoephere. S' r Method of Apt?reach This research pregrea will be broken deem into two geoerai topics 1 (l) experimental detemtoatloo of the dry deposition characteristics of lead aerosols over the else rang** found In the atmosphere, and (?) calculation of the theoretical efficiency with which lead aerosols are renewed or tearenged froa the atmosphere by other natural aschanliu. .< The first phase of the proposed research vc*uld be directed tc^rd exper imental deteratxatloe of the velocity of deposition of urban aerosols. C r TV* * The experimental program to detemloe the velocity of deposition of urban lead aerosols will be centered around a staple wind tunnel. Tie lead aerosol content of this tAluxel atnosphere In Menlo lark will be used as the etarce aerosol. TMs Is cotsMered to be preferable to setting up a special genera tion systaa. flLnce cur available date c*> urban lead aerosols lrvlloate a g*nerally eor.slsUnt sits distribution, date obtained oo local aerosol characteris tics should be generally afpllcabls to other urban areas. r !i Chanter lain, A.C., Transport of parllMas across bcarvtary layers, AEXK-M 1122. Abasia Zhergy hesearch Establishment, (Unall, England (1962). 2 / Th# wind tuno#l exposure chanter will b* A *qu*r* wooden duet *bout 30 Inch** cn a aid*, loc*t*d on tb* roof of on* of the present build* lngs. Thl* will protect th* *xprlnt frcn direct exposure to wy Io c aI dut And exhAujt *curc*. Th* Air Intel* will not b* filtered, but will cco tein a flow eilgrrxnt #ctloo to r**trlct tb* d*gre* of turbul*nc* in tb* flow through tb* eb*j*b*r. * lb* working **ctloo of tb* cbaaber will p*mlt various typical rurfAces to be *rpoe*d to tb* eerceol itrna under constant known Air fl conditions. After a period of *xpo#ure tbe *urfAe* will be analysed ter 4*polted leed. Haasuremnt* will Alio be tekea of tbe total lead concentration* end particle lxe distribution. fro* tb*e det* tbe velocity of deposition will be celeulAted using CbABberlAln'e expressions D- (Vg) (C) where 1 1* velocity of depoeltloo 0 1* depoeltloo rat* per unit Are* C 1* volua* concentration Th* surfAc** to be studied will include snooth XHlipcre filter a*ter1*1, (rui, leaf type vegetation, rough pevwaact, end v*t*r. Tb# (reel, vegetation. And pavecaot xay bar* to be tiBuleted fraa low-leed BAterlels in order to be Able to detect tbe deposited leed Above a natural background. All of tbe perleant* will be replicated A Dumber of tlM. . In tb* **cood pfc*** of thl* researcb program tb* ether sechanlss* bp which lead can be moored fro* tb* staoepber* would be studied theoretically. Cur present knowledge of tbe characteristic* of urban lead aerosol* should allow the sp-plicstloo of trie ting theories cf coagulation, v*ehout, aol r!out processes. Tb* difference In these latter two processes 1* that la vutxwt tb* particles beeoc* attaebad to tb* precipitation during tb* falling process! whereas particles reoored by ralncut bar* beoco* part of tb* droplet* prior to tb* actual precipitation. A \ ; There hay* been A nueber of studies of wesbout processes, for exanpls. Chanter 1*1d *Y*# used Langaudr'*3calculation* of efficiency of lspnctlon And Aeet'sWalndrop sis* distributions to dsternin* tbs rt of scavenging of noncd.1 spars* Aeroeols. Greenfield'hs* Also studied tb* problsi And tvebertce/ha# ccnaldered tb* spec lei cee* of noo-vettabl* paxtlcles, Tb* Abov* cited studies And others of tb* aso* type would serve *s a taels for estimating tb* affect* of washout css tbe renowl of lead particulate* fro* the atmosphere. |. ,1 i0^Jl V i CtAcbrUln, A.C., Aspect* of travel eral depo* 11loo of eerceol And vapor clc*1s, At'edo finergy research Eatabllatoant, Harwell, Ad KT/H l&l, Hervell, Crgler.l (1^5). 3 langsutr, I., The production of rein by a obaln reaction In ctsailus aloud* At temperatures Above free ling, J. Heteorol. J, 173*92 W beet, A.C., Tt# else distribution cf raindrops, ^art. j.hny. Htenrol. ; Boo. 7*, 16-# (lyso). ) Greenfield, O.H., Hein caverging of radioactive particulate latter fra* 1 th* atmosphere, J. Hetearol. 113-23 (l737) 6 fnb*rtoo,0.8., Scavenging Action of rein on nm-wet table partloulAt* ratter suspended In tbe atmosphere, Item. J. Air follutlon, 3* lA*7fl /..a (I960) J .wnqwy w jr w j w w wn wrwpwa Theoretical and experiaantal itulin of rainout have boon nad*. Bovoral of tboio oro deecribod by Jung* 7 In hii book and it appear* that ouch otudloo could bo applied to the particular problon of load cexpound*. Coagulation and othor pooilbl* Becbaniuu of aoroool nodifleetloo and renoval would alao bo conaldorod. In addition to the mrvoy of the literature relating to theory and *xperl< Mnta oo aoroaol nodlflcatlco and reooval and the application of tboio work* to ataoopherle load aerooola, it would bo worthwhile chocking calculation* agalmt obiervationa vhoro pooilblo. Do*t fall atudloi bare boon node and ocn* of tboio have Matured load ccapcund* (t.g.,John*on and Booaano'a atudy la Seattle 8 ). Attecpt* would bo a*do in the progroa to check calculationa with any obiorvatlcoa which are available in the literature, but no experimental aoaiureaiat program la planned for thli pfc&oo of roioarch. In the final report which would he prepared at the eoocliulon of this progroa the roiulto of the roooarch would bo related to the ataoopherle dia per**! of urban load aorooole. COST zsnxkis Thll roioarch would probably require about 000 year to ca^lote. An approximate oitlnato of the coot* of thll roioarch bai boon made. Thii oitlnato indicate* that the coot of thll roioarch would bo ajprcxlatoly >35,000. Thli roioarch could bo begun early la 1$67. % Auguit 5, 1966 KLaar Kofclmcc, Senior Metoorelogllt beparteeot of Ataoephorlc Science* Stanford Roioarch Institute ; * . ... *s * !T. 3 7 Jung*. C.R., Air Cbmlitry and badloactlrity. Academic Proii, Rrw Tort PP. 291-95 (17TT. 9 John* on, A. I. and A.T. Ronano, Extended Chemical analyali of duet fall, paper preiented it the Seventh Conference on Method* In Air tollutloo Studln, lot Angel**, Jan. 25-16, 1S^5. Dpcniored by California State Department of iUblio Health. ? .i k l-n-ii.M 111|||| I i yyr* [