Document 6w7a9kBLYgDpnw7KOkbBvJka1

Nature Vol. $S2 November 7V 9974 * J. A. Mi M. Kors JM$ 6 1975 Sttchtifig Reactor Cc/ifnttn Nederland, J, F, v;o. VATE L.. T. HtRMANS G. Diurets flooftikatitoor-'Schc vettingsweg 112, *S-Gn>v<*ntiftiicf'Omittr,'sockccutrum: Petfen (/V-//),..' The Netherlands *' l *? Received June 2Ri-revised Augi*t 28, 1974. *> 1 Voida. R. A*-, nnd Whitby, K. T. J. Colloid fnter/acr ScL, 25* 568-576 1967). * * Stbtvr, W., ofid Flachsbarl, H., Env. Sei. 7ec/rHo/.', 3, 12SO-1296 ^ (1969). ' *: * WrigU-y. N. C*., J. Uftra.uruct. Rex.. 24, 454-464 (1^68). * Sthher, \V., Ftch&bnrl. H., and Hochraincr, D., .Sto/ifr, -30, 277-285 (1970). * * Stoher, W,t ift <4.TMrr.micr nf Airborne Panicles (cart, by Mercer, nnd Stober), 249 <C. C. Thomas, Springfield, 1972X * Or-ikc. R. L / in Topics in Current Aerosol Research {Parts') (edit. by Hidy, arid Brock), 201, (Pcrganion. Oxford, 1972). Decline of I'CB conccnlrafions in Norlli Atlantic surface wafer Poi.YCitLORDiiiPiii.tsiYi. concentrations in Njyrlh Atlantic lurfiicc valcrSthavc declined fortyfold since 1972, following the cessation or .dcrlain industrial uses of thoseVcompounds. Industrial sales of PCB for use in products which-'wouid allow leakage to thc-Cnvironmcnt, for example in plastics, inks and paints were stopped in the United States and Sweden during 1970-71 *; and 'in 1972--73 other European countries and Japan initiated a similar action1. In 1971 and 1972 average surface concentration^of PCI) in the open North Atlantic.Ocean were J,About 30 ng (rcT, 3 and C E. Olncy and J. Quinn, unpublished). |$y April of 1973 the concentration in jhc Sargasso Sea had been rpduccd to 1 ng ! "* (ref. 4); five months later we found that the'decline had levelled at 0.8 Tig l-1, a concentration which was still present m February 1974 in th& north-west Atlantic. The accumulated data arc presented in Table I. These observations revealing a reduction in surface watdr concentra tions of rCB compare well with our February \$74 measure ments of a tenfold decrease of PCB in the atmosphere over the tiotth-wcst Atlantic since 1973 (ref. 5), and a fivefold decrease Table 1 PCB'concentrations in North Atlantic surface waters* 1971-74 Date McanPCBf <ng 1 ->>. Sampling region samples lrfbthod ' 8/71 7/72 8/72 9/72 4/73 9/73 9/73 2/74 25 41 >0 1 2 0.8 Of IcelnndtoNovaScotla u Newfoundland to Portugal Portugal to Norwegian Sea s Woods Hole to Rcrmucda - -Sargasso Sea # Azoresto09N, 40r>W f Id Barbados Sargasso Rea lo New York Bight 4 New Pngland s Continental Shelf 8 8 1! 37 8 10 V ;a i ; \c *rC t7A c < .c 4 3 3 3 4 3 3 3 * 0-30 m. * J Blank value*? for PC.R In methods A. B and C werfc 0.9, 0.5 and CK3 Tib I*', rospetlively. Replicnlc analyses using mclhmls H or C Showed nrtnrrr,Vrxvariationrr i 20%jM the I ngf-* level. Quantita tion nieihndt Arc presented in refs 3, 5, 6. J A, Extraction of 0.3--3.8 I with chloroform or dieMornme thane; , extrachon of.70| with 5% ether in hexane; C, passing 40-60 1 through AmbcrIUc XAD-2 tciin followed by elution* with boiling tbcetorutrile. -* t C. . Ofney >nd J. J, Quinn, unpublished Information. #. 3B7 since 1972 in . PCI! content of mixed plankton collected along 09'N latitude in September of 1973 (rcl\ 6). The da la require that about 2x 101 tons of PCH were lost from the upper 200 m in less than one ycar;T. To explain this loss, four processes must be seriously considered : (I) apparent dilution of dissolved PC*li by vertical and horizontal advection and diffusion; (2) association of PCB with sedimenting part iclcs; (3) evaporative codislillation into the atmosphere and (4) bio logical nnd chemical degradation. The information obtained from the monitoring of bomb fallout radionuclides is relevant to the present problem because like PCB, they arc delivered to the ocean from the atmosphere, can exist in dissolved and particulate phases, and experienced a similar decreased input after the nuclear test ban agreements of Table 2 PCB concentrations in North Atlantic subsurface waters*, 1973 . Oatc of collection Position and analytcst Latitude Longitude Depth PCI) (m) (nE l-J 19/9/73 * 2/10/73 09 00* N 40' 00' W 32" 25' N 70 20' W 10 100 200 400 500 700 1,000 2,000 3,000 to 100 300 600 900 3.100 4.3 2.0 1.4 1.1 1.3 1.5 1.0 2.1 1.0 0.6 0.8 0.9 0.5 1.9 0.4 * Reproducibility at the 0.5 ng 1 "* level was 40%. The blank was produced by recycling 40 I oT XAD-2 extracted seawater through the entire procedure and averaged 0.3 ng 1 ~l. 7 Method C was used. 1963. For example, strontium-90 which is mainly In the dissolved state in seawater, required more than five years after the test ban treaty to decline to one-half the surface water concentrations of 1963 (ref. 7). Thus, depletion of dissolved PCB from the upper ocean by advection and diffusion seems loo slow to explain the observed rate. The rate of PCB removal from the surface waters more closely resembles the behaviour of the plutonium nuclides which are believed to be associated with particulates*. The vertical distribution of plutonium isotopes in the Atlantic was besl explained as being associated with particles falling at rates of 70-392 m yf"1. The well known affinity of PCB for solid surfaces suggests that adsorption on falling particles could be a major transfer mechanism. In fact, if 2 x JO* tons or less of PCB has been transferred to the deep ocean each year (1970 was the peak -production year) for the past 10-15 yr and was dispersed throughout the entire waler column, the concentrations to 3,500 m would still be less than 2 ng I"1. Two 1973 profiles of PCB in the water column arc presented in Table 2. The profile at -40 OO'W was typical of eight other stations in the North African and Cope Verde Basins; in contrast, the station at 70 20'W revealing very low PCB levels at the surface, was 'similar to nine Other stations-In the North American Basin the same year. We arc, at present, unable to ascertain the relative Importance of evaporative codistillation of PCB from the surface water or of blogcochcmical degradation. Either process could explain the lower surface water concentrations in the North American Basin. There is, as yet, no evidence of biotogical metabolism of PCB in the marine environment. We note the rapid response of the open-ocean mixed layer to the reduction of industrial discharges of PCB. Efforts to O ^tO O ZdF STLCOPCB4044457 5T1'8 , - ", - . deHminc the medumism of this elucient transfer prgeest Arc fn progress. " t* This work was supported by an NSF grant to the4nlcrria- tionnl Decade or Ocean Exploration. -e '* George R. Harvey \ Wjiuam G, SteiNhaver Helen P. Miklas. * Woods Hole OceanographicInstitution, Woods Hole, hfass/fchusctts02543 -* * Received June 27; revised Juiy 15, 1974. *, ,v ,,* * *; * Chan. Itagns. Nett 's. July 20, 3J (1970). [. * O.LCD, I'ress Release, Paris, February 1, 1975. 4 * Harvey, G. R., Stefnhauer, W. G., and Teal, J. M., SeteAee, 180, 643-644 <1973). -* 4 Bidlcman, T. F., and Olncy, C, B>, Science, 1*3, 516-518;{I974), 9 Harvey, G. K., and'Stcinhaucr, W. C., Almas* Environ., bV-7'^'?--782 (1974). \ * Harvey, G. R., Mifclas. H. P_, Bowen, V. T., and Sftlinhaucr, W. O., J, Mar, firs., 32, I03--118 (1974). .- * Bowen. V.T.. Moslikin, V. 1-., Volchok, II, L-.,and Suglhnra.T.T., Sconce, 164, 825 -287 <1969). * 'Norlikin. V. I*., and Bowen. V. 7'.. in Radioactive Contamination of the Marine finvifontncM, 671-686 (IAEA, Viertnn, J973). Origin proposed for non-protein aniino'ncids ip meteorites ' 1 Tire aminoacids that have been identified m several mcto'riics'a* can be divided into',two classes: those present in proteins and those which are not. The presence of the non-protcio amino acids, x>- and l>&-aminOisobutyric acid and fl-alapmc, is described as evidence for the indigenous origin of njfctcoritc amino acids and against terrestrial contamination1. It is implied that these fl-amino acids arise by probiotic condensation of ammonia, methant*,' hydrogen, water and other simpjfc prim ordial molecules'. T^c fl-amino acids and ether amino-acids can arise from simple rnoJcculcs by Fischcr-Tropsch synthesis m the laboratory. Hydrogen, carbon dioxide and ammonia were heated to high temperatures in the presence of natural 'catalysts expected to be present in the solar nebula*. -- In other experiments, thermal synthesis of amino acids occurred in a simulated primitive atmosphere of methane, ammonia and water, followed by acid hydrofysisof tltc products. fWAIaninc was obtained In high yield, relative to other, amino acids, and the straight-chain compound, 0-amino-iV'butyric acid*. These amino*acids were postulated to arise respectively from hydrolysis of'^P-aminopropionitrilc and the nitrile inter mediate arising from addition of ammonia to crotonjcmitrHc. Evidence for this soule was the identification of succinic acid and N-rriethyl-fl-fllqnmc which arc likely hydrolysis products of nitrile intermediate^. Production of ^nminoisobuiyric-atrid was not reported in these experiments*. y Jl-Aminoisolnityric acid is a rare amino acid with a.curious distribution in naibrc. Il has been isolated only from*-human urine*, iris bulbs1, flatworms* and edible mussels*. '.Man is probably the only ipammalian species to excrete i>(--)-amino- isobutyrtc acid10 though there is chromatographic evidence for Its presence In rabbit urine". Metabolic experiments suggest that the pyrimidine base thymine, from nucleic acid catabolism, is the precursor of (f-aTninaisobutyric acid in ihe human5'*'*4. Similarly, metabolic production or(Kalanme in rat liver is from the pyrimidine uracil1*. %. Ey analogy with:*thesc known reaction sequences catalysed biologically, I suggest that heterocyclic compounds could also loci as precursor!* far the fl-amtno acids found in meteorites. In this cose, scission of the ring of heterocyclic compouneftt'formed prebiotically .would' occur under the catalytic condUions of extremes of temperature and radiation thought tooccur.ktspace. * '% % Nature Vat. 2S2 November 29 1974 The purines* adci...*e and guanine, and a substance resembling uracil have been delected in die Orgueil meteorite**. Xanthine, thymine, uracil and derivatives have also been obtained experi mentally by mimicking supposed prcbiolic conditions4. This chemical route lo certain non-protein amino acids described above would presumably give racemic mixtures of both stereoisomers, for example, both d-, and L-p-aminoisobutyric acid, as found in meteorites*. It would be interesting to know if thymine, dihydrothymine, uracil and related com pounds, when heated under supposed prcbiolic conditions, did give traces of the p-amino acids. Deportment of Biochemistry, Chelsea College, University of London, Alanresa Road, Chelsea, London SW3 6LX, UK D. F, Evered Received July 4, 1974. 1 Lawless. J. O., Kvcnvoldcn, K. A., Peterson. E.. Ponntimpcruma, C., and Moore, C., Science, 173, 626 (1971). a Lawless, J. C., Kvcnvoldcn, K. A., Polmon, E., Honnamperuma, C., and Jarosewick, E., Nature, 236, 66 (1972). * Miller, S. L.. Science, 117, 528 (1953). .. * Antlers. E., Hayalsu. R. and Studicr. M. H., Science, 182, 781 (1973). * Lawless, J. G., and floynion, C. D., Nature, 243, 405 (1973). Grumpier, H. R,, Dew, C. E., Harris, H., and West all, R. G., Nature, 167, 307 (1951). ,,, , 7 Asen, S,, Thompson, J. I*., Morris, C. 3., and Irrcvcrre, F-.3. bio/. Chem., 234, 343 <1959). * Campbell, J. W.. Biot. Bull., 119, 75 (i960). * Awapnra. J., and Allen, K., Science. 130, 1250(1959). 10 Evered, O. F\, Comp, Riochrni. physio/., 23, 163 (1967), 11 Block, W. D., and Hubbard, R. W,, Archs ISiochem, Biaphys-, 96, 557 (1962). ,^ ** Awapnra, J., and Shullenberger, C. C., Clin. Chun, Ada, 2,119 (1957). __ " Pink, K.. Henderson, R. N-, and Fink. R. M.,J. bio/. Chem., 197, -441 (1957). w Cartier, S. M.. Archs Bioeftem. Wap/tys., 80, 400 (1959). 44 Cannclakis. E. S.,^. bio/. Chent., 221, 315 (1956). ` ** Hayatsu, R,, Science, 146, 1291 (1964). Evidence for downwind flights by host-seeking mosquitoes The behaviour of flying insects which make use of airborne chemicals in their search for food, oviposilion sites or sexual partners can be separated into two phases, the search flight bringing them into contact with the ottractant plume and the approach flight leading them to its source1**. The second phase is characterised by upwind orientation in response to the appropriate chemical stimuli*"*. Mosquitoes arc known to fly upwind as they approach a warm-blooded host7"*. For most insects relatively little is known of the pattern of the preceding search flight which Haskell* described as `wandering*, but where the wind is light it may be upwind*. Experiments in West Africa have shown that the majority of mosquitoes entered flight traps from the downwind side, that is they appeared to have been -flying upwind, regardless of the presence or absence or a host (ref, ID and W. F. Snow, unpublished). Here we report experiments that unexpectedly provide evidence for the opposite -type of behaviour. ^ If the search flight is in a generally upwind direction. It Should be possible to divert mosquitoes round a host by setting up a barrier on the downwind side nnd so provide a measure of protection from their attacks. The barrier would need to be sufficiently far away for the mosquitoes to encounter It before they detected the presence or the host, so that directed responses towards the host would not be elicited. This distance was estimated by Gillies and Wilkes1* to be less than 18 m for a host the fixe of a man. A host stationed at this distance upwind ee?ooso STLCOPCB4044458