MUROZUMI  Masayo

PATTERSON  C.C.

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MUROZUMI, Masayo

室住, 正世

ムロズミ, マサヨ

PATTERSON, C. C.

Muroran-IT Academic Resource Archive

Concentration of Common Lead in Greenland Snow著者 MUROZUMI  Masayo, PATTERSON  C.C.journal orpublication titleMemoirs of the Muroran Institute of Technologyvolume 5number 2page range 611-613year 1966-08-25URL http://hdl.handle.net/10258/3263Concentration of Common Lead in Gr，配置llandSnow M.恥lurozumi*and C. C. Patterson料之Abstract The recent increase of Jead concentration in polar ice sheets is ascribed to smelter fume and lead alkyl decomposition producis originating in the northern hemisphere. The concentration of c_ornmon lead was measured in seven snow samples taken at ten year intervals from layered snow at Camp Centuryラ Greenland. One hundred gallons of snow were collected at each of the seven points distributed throughout a vertical depth of 150 feet， which depth corresponded to sixty years' accumulation. Isotopic dilution analyses， which have been successfully used for studying lead in sea water， were made on these snow samples. As carried out in this instance， the sensitivity of the method was about 5 x 10-12 gm Pbjgm snow. The background of naturallead in the snow was expected to fal in the range of 10-13 gm Pbjgm snow， or below the limit of detection. An additional increment of lead， which came from the washout of lead alkyl decomposition products originating in the United States and Europe， was expected to appear sometime after 1925. As shown in Figure 1， analyses indi-cated a level of 0.5 to 1.5〆:10-10 gm Pbjgm snow in the五vesampled layers dating from 1904 to 1944. After that time， lead concentrations increased. Snow at 1954 contained about 3:< 10 -10 gm Pbjgm snow， and at 1964 the concentration was in one case 7 and in another 25;< 10-10 gm Pbjgm snow. Silica analyses gave Si concentra-tions in the snows of about 1 x 10 -8 gm Sijgm snow， which showed that the ob-served pre-1904 lead concentrations were a thousand times higher than those which would result from natural dusts. 2 '1(3) I i -~/ 一一1964 ? ? ? ? 、 ? ? ? ?/904 /924 A宮EぜS1701-1//デ'4AThere are two alternative explanations Fig. 1. Pb in Greenland Snow for these results. On the one hand， the high background of lead in the older snows could have originated from smelter fume， smelter dust， and contributions from lead alkyls may not have exceeded this background until the late nineteen *室住正世* California Institute of Technology (105) 612 M. Murozumi and C. C. Patterson forties. This is possib1e because the fraction of the total year1y 1ead production in the United States devoted to 1ead alkyls increased from zero in 1923 to about 15% in 1963， while the total yearly lead production together with the fraction 10st to the air as fume remained more nearly constant. The tota1 annua1lead productiod in the United States and the estimated annua1 1ead a1ky1 production in the world at various times are shown in Figure 2. Atmos-〈立E E 占ミ)しペ 6 苫旬) ル、¥KCR。ふ3 :， Et 25 斗ポQ仁¥F~3J  :〉 4 .古32 2 長喜もゼ円 vコ舌s、eミt》 兄f rE J5 ζとっ三1守04 1924 1'l44 864 year Fig. 2. Lead Smelter and Alkyl Production pheric contributions from smelter production may amount to about one part in a hundred， whi1e atmospheric contributions from 1ead a1ky1s may amount to about two parts in three. This 1arge discrepancy between fractiona1 contributions from these two sources combined with di旺erencesin their production histories provides a basis for the interpretation of the 1ead concentration data which has been offered above. 1t is perhaps signi五cantthat the concentration of 1e乱din the air at Camp Table 1. Pb四6jPb207Ratios in Lead from the Air. Snow， Sea "¥司Taterand Gasoline Source of Lead East Coast gasoline Greenland snow West Coast gasoline West Coast snow West Coast air West Coast sea water West Coast ocean s巴diment(deposited 10 -10 yrs. ago) Pb206jPb2仰木1.186 1.177 1.145 1.144 1.154 1.161 1.197 (106) Comment Compositions of Pb 0τes di妊er. Feed to alkyl plants on east and west coasts may di妊erShould be mixture of east and west. If alkyl lead contributions are signi五cant，lead in air， snow， sea wat巴r，and gasoline should be similar localy. Ancient indigenous lead probably difers from non-indigenous alkyl lead. Concentration of Common Lead in Greenland Snow 613 Century， uncontaminated by local gasoline exhausts， was found to be about 0.01 r Pbfm3 in 1964， which is thousands of times higher than would be expected from natural dusts and salts in the air. Fur此the臼r幅τ~mC∞ompo田5討sit江ion0ぱflead in 1964 snow a拭tCentury wa部sintermediate betwe配enthe slightly nonト.固4圃.radioge凹nicleads in gasoline sold on the west coast of t出heUnited States and the slightly radiogenic leads in gasolines sold on the east coast of the United States. On the other hand， gasoline powered vehicles have operated at Camp Century since 1954， and the rise of lead concentratrations in snow during the last decade may have resulted from local sources of lead contamination. 1n addition， the size of the samples was scaled up ten times larger than those successfully analyzed before， and the high background of lead in the older snuws may have originated from improper cleaning of the large polyethylene snow-melting drums which were used. The two di旺erentlead concentrations in 1964 snow shown in Figure 1 ongl岨nate from two di宜erentsites. The high value came from a site located six miles NE of Century. It was collected by using a gasoline powered vehicle to get to the site and the samples were towed back to camp in the exhaust plume of the vehicle. The amount of lead spewed into the air around the samples by the vehicle on the return trip was about 106 times greater than the amount of lead found in the samples. The low value came from a site located three miles E of Century. 1t was collected by traveling to and from the site on foot. 1t is not known whether these two values reflect lateral heterogeneity in real lead concentrations or differences in local contaminaiton during collection. These preliminary results show that it may be possible to evaluate the extent of lead pollution of the atmosphere as a function of time by analyzing fossil snow. It is proposed that additional snow samples older than 1954 be taken at Camp Century and melted in Kel-F coated stainless steel pots to eliminate the possibility of contamination during melting. A grid of surface samples， accessible by heli-copter， would be taken in the NE sector at very remote distances from Camp Century to study lead concentration variability in one time zone in an area known to be free of local sources of lead contamination. Two or three deep trenches would be dug and sampled at very remote distances from Camp Century to provide access to snow accumlated during the last五fteenyears in areas known to be free of local sources of lead contamination. Work at the laboratories in California recceived support from NIH grant No. AP 00251-1 and 2， AEC Contract No. AT (04-3)-427， and ONR Contract No. 2216-01. Logistics and field work at Camp Century were supported by CRREL. Read before at a symposium on marine geochemistry at the University of Rhode lsland， Oct. 1965 (Received March 31， 1966) (107) 

Concentration of Common Lead in Greenland Snow

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