Document zoqdN2apGJpQ4vEnmGKpdyv16

Nature Vtd. fo2 November 29 1914 2. A. N* M. KOPI i. F. vjo. Vati JAW 6 1975 L. T. M, Hexmamb O. Dinars Stkkttng Praetor Centrum Nederland, Ho*ftlknntoor-'$chnrninfs*nr 112. t 'S'Cmxenhngex Ondcrsoektentmm: Petten (N-/f ),..* The Nethtrlandt ' Itaeivrd Juno 21; revised August 22, 1974. Vnmdn, R. A.. M)d Whitby, K T., J. CoffWd Intrrforr Sti., 25' 56H-S76 (1967). v StOhcr, W.. afid Plachsbort, H., tv. Sei. TeehmL 3. 1290-1296 (1969). ' .. Wriftlry. N. ., /. WPwifriw/. Arj., 24. 494-464 (lfo). , * Slhhcr, W.. Pfechsbarl, IL, and Hochrainct. D.> Sun*, 30, 277-215 (1970). T 1 SttHwr, W,, in Ashesnwnt of Airborne Portieks (con. by Mcrccr. Morrow, mm) Xtfihcr), 249 (C C. Thoms*. Springfield. >972). Drake. R. L.,*- In Tofdr* ht Cnrrrnt Amuoi Prteareb (Portt) (edit. by HWy, uid Brock), 201, (PerRamon, Oxford, 1912). X Decline of-PCB concentrations ;! in North Atlantic surface water POLroiLonofurttitNYi (PCD) concentration* in N$rth Atlantic surface walcrsjtavc declined forlyfold since 1972, following the oesntkm of .derlain industrial uses of those ^compounds. Industrial sales of PCD for use in products whichVwould allow leakage to the*6nvironment. for example in plastfei, inks and potots were slopped in (he United Stales and Sweden durini 1970-71'; andln 1972-73 other European countries and Japan Initiated a similar action*1. In 1971 and 1972 average surface cnnreninMion^cf PCD in the open North Atlantic.Ocean were about 30 ng I"* (ref. 3 and C. E. Olncy and J. J. Quinn, unpublished). $y April of 1973 Ihc concentration in |he Sargasso Daa had been ipducod to I ng I*' (ref. 4); five months later we found tint the'decline had levelled at 0.8 ng I a concentration which was still present in February 1974 in ihd. north-west Atlantic. The accumulated data are presented in Table I. These observations revealing a reduction in surface watdr concentra tions of PCD compare well with our February l$74 measure ments of a tenfold decrease of PCD in the atmosphere over the north-west Atlantic since 1973 (ref. 5). and a fivefold decrease Tobt* I PCD1 concentrations In North Atlantic surface waters* 1971-74 ; Deis Mean rCDt (rat'1). SoMpttni No. of Analytical) Ref. 1/71 7/72 V 9/72 m 9/7J 9/75 1/74 25 Instead to Nov Scotia 41 t Newfoundland to H . NorweglanSes It 30 Wood* Hole to Bermuda 27 I * Sargasso Sea 2 * Azores to 09"N, 40*W t to Barbados 0.1 '* Sargasso Sea to . New York Bi|hl 0.1 t, New Itnelamt t Cuntinrntal Shelf :a ;B *C ..*C /.A *C a #,c .c OOOm J t Bleak value*for PCI) In method* A, B and C werh 0.9,0.5 at M H.l ruMttively. Replicate analyses using method* P or mowed an averojw variation of ;j 20%atths I nar' leyel. Qwsntiii lion method* are presented In ref* 3,5.6. ! I A, Extraction of 0.5-31 I with cbbtroferm or dkhlnromcthan E astrestion of.201 with 5% ether in hriane: C, pawing 40-66 Sa.Amberl(o XAD-2 min followed by elution* with boihf 1C E Ofoeypnd J. J. Quinn. unpubHahed Informpllon. 3B7 since 1972 in the PCD content of mixed plankton collected long 09*N latitude in September of 1973 (ref. A). The data require that about 2 x to* tons of l*CB were lost from the upper 200 m in less than one year'. To explain this loss, four processes must be seriously considered: (I) apparent dilution of dissolved PCB by vertical nod hmi/rrolal odvcction end diffusion; (2) association of PCD with sedimenting particles; (3) evaporative codisiHlation into the atmosphere and (4) bio logical and diemical degradation. The information obtained from the monitoring of bomb fallout radionuclides is relevant to the present problem because like PCD, they are delivered to the ocean from the atmosphere, can exist in dissolved and particulate phases, and experienced a similar decreased input after tire nuclear test ban agreements of Table 2 PCB concentrations in North Atlantic subsurface waters*. 1973 Date of collection; Position and analyses) Latitude Longitude Depth PCB (m) (mi") 19/9/73 09*06* N 40*00* W 2/19/73 32* 25' N 70*20'W 10 100 200 400 500 700 1.000 2.000 3,000 10 too 300 600 900 5.100 4.3 2.0 1.4 1.1 1.3 1.3 1.0 2.1 1.0 0.6 0.1 0.9 0.5 1.9 0.4 * Reproducibility at (he 0.5 ng I *' level was -f 40%. Tha Monk was produced by rrcvcling 401 nr XAD-2 extracted seawater through the entire procedure and averaged 0.3 ng \ t Method C was used. 1963. For example, strontium-90 which is mainly in the dissolved slate in seaweter, required more than live 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 (he upper ocean by adveetton and diffusion seems too slow to explain the observed rate. The rale of PCD removal from the surface waters more closely resembles the behaviour of the plutonium nuclides -*pu which are believed to be associated with particulates'. The vertical distribution of plutonium Isotopes in the Atlantic was best explained as being associated with particles falling at rales of 70-392 m yr"'. The well known affinity of PCB for solid surfaces suggests that adsorption on falling particles could be a major transfer mechanism. In fact, if 2x HP tons or less of PCD 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 water column, the concentrations to 3,500 m would still be less than 2 nt I Two 1973 profiles of PCD In the water column are presented in Table 2. The profile at 40* 00'W was typical of eight other stations In the North African and Cape Verde Basins; in contrast, the station at 70* 20'W revealing very low PCD levels at the surface, was similar to nine other stations in the North American Basin the same year. We are, at present, unable to ascertain the relative Importance of evaporative codlstHlaiion of PCB from the surface water or of Mogeochcmieal degradation. Either process eouM explain the lower surface water concentrations in the North American Dssin. Three is, as yet, no evidence of biological metabolism of PCB In the marine environment. We note the tepid response of the opcn*occan mixed layer to the reduction of Industrial discharges of PCB. Efforts to E *? B O SNOW Nature Vat. 252 November 79 1974 determine the mechanism of this efficient transfer process are In progress. , This work was i(ipporte<l by an N5F rant to the interna* ttenal Decade of Ocean Exploration. ** Oeoaoi R. Harvcy \* WtLUAM O. STnmiAYIR Hbun P. Miklas/ Waadt Hate Oceanographic Institution, `, Waadt Hate, Masmhnsetts 0254$ \ Received June 27; revised July 15, 1974. Ckem. /Tri*. Uni. July , 31 ? (. 1 O.D.C.D. Press Retruc, Peril, February I, 1973. 1 1 Harvey, 0. R., Stefnhauer, W. O., and Teal, J. M., Science, 160, 43*644 (1973). a . SMIeman, T. P,, arid Otney, C. B.. Jrtmrr. l3.316-311.(1974). Harvey. 0. R., sruLSteinhsuer, W. G., Atmos, tnviron., I,-777-712 0974). : Harvey, 0. R . Mlkhu, II. P., Bowen. V. Tn and Sftfnhauer. W, 0,,/. Mm, ftr*., 32, 103-IIS (l74). .- Bowen, V. T . NmtjMn. V. U , Volchek, II. L., and Sugihara, T. T.. Science, 164. I2J2I7 (1969). . Noshkia, V. li., aiid Bowen, V. T., in BmHoartivt Contamination of ike Marine bnmmncnt, 671-666 (IAEA, Vienna, 1973). Origin propond for non-protein Mfao'scids ill' meteorites '/ "1 Tm amino acids tha* have been identified in several meteorites'-* ean be divided inter,two daises: those present in proteins and thoaa which are not. The presence of the non-protein amino aids, D* and i*|*aminoisobu(yrtc acid and O-alanmc, is datedbod as evidehes for the indigenous origin nf mbicoritc Mdno adds and against terrestrial contamination,. It is implied Hal these fl-amlnb adds arise by probiotic condensation of ammonia, fnethand; hydrogen, water and other simnlb prim* ordiai molecules'. TJhe fr-amino acids and other amino acids can adaa from simple iholccules by Fischcr-Tropsch synthesis in the laboratory. Hydrogen, carbon dioxide and ammonEs were heated to high temperatures in the presence of natural 'catalysts expeeted to be present in the solar nebula4. _ In other experiments, thermal synthesis of amino acids aaaurved in a thqfatated primitive etmosohere of methane, ammonia and water, followed by acid hydrolysis of the products. Mlanlm was obtained in high yield, relative to othqr. amino addR and the ttrnight-chain compound, fl-ammo-Q-butyric arid*. These amino acids were poettrialed to arise respectively from hydrolysis offl-amioopropionitrite and the nitrite inter* mediate arising from addition of ammonia to crotononitrile. Evidence for this some was the identification of succinic acid and N-methyi-fl-alapina which are tikcly hydrolysis products of nitric intermediate*. Production of g-aminoisobutyric fteid was not reported in thete experiments*. I-Amiflotiobgtyric acid is a rare amino acid with a-curious distribution in natbre. It hns been Isolated only from human wins', iris bulbs',-Aatworrm* and edible mussels'. *,Man is probably the only mammalia" species to excrete t>*( - WUaminoisobutyric acid" tHpugh there is chromatographic evidence for Hi presence In rabbit urine". Metabolic experiments suggest that He pyrimidine base thymine, from nucleic acid catabolism, is He precursor of Q-aminoisobutyric acid kt the human'**". HmNarly, metabolic production of 0*atanine In rat liver is from He pyrimidine uracil". hteiegkaNy, I suggest that heterocyclic compounds cdatld also PI M precursors for the ftanino adds found b meteorites. In HH ansa, scission of the ring of heterocyclic compounrfrformcd pssbiotisMIy wouty' oocur under the ostalytie conditions of eairsmssoftsmpsmtuie and radiation thought to occur^in space. The purines, adenine and guanine, and a substance resembling uracil have been detected in the Orgucil meteorite". Xanthine, thymine, uracil ami derivatives have also been obtained expert* menially by mimicking supposed prcbiotic conditions'. This chemical route to certain non*protein amino adds described above would presumably give racemic mixtures of both stereoisomers, for example, both t>*, and i.-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 prcbiotic conditions, did give traces of the P*emino acids. - Department af Biochemistry, Chelsea Coltene, University of London, Monresa Rood, Chelsea, London SW3 6LX, UK Received July 4, 1974. I Lawless, J. G.. Kvcnvotdcn. K. A.. Peterson. E.. Ponnamperuma, C.,and Moore,C,Scimcr. 173,626(1971). * Lawtess, J. G., Kvenvohten. K. A., Peterson, Km Ponnamperuma, C.. and Jaroscwick. E., Natarr. 236,6611972). * Mttkr. S. I... Science, 117, S2I (1933). 4 Anders, Em Hnyaltu, R., and Slodicr, M. H.. Science, 112, 711 (1973). ' Lawless, J. C., and Boynton, C. I)., Notme, 243,403 (1973). 'Crwmpter, It. R.. Dent. C. E., Harris, II., and WcstaH, R. Om Nature, 167.307(1931). * Amo, S., Thompson. J. I*'., Morris, C. J.. and Irreverrc, F., J. Mat. Ckem., 234.343 (1939). Campbell, J. W.. AM. Unit . 119, 75 (i960). * Awapara, J.. and Aden, K.. Science. 130. 1230 (1939). " Everod, D. F,, Con*. Bioekem. Physiol., 23, )6) (1967). II Block, W. D., and Hubbard, R. W,, Areht Bioekem. Btopkys., 96, 557(1962). " Awapara, J., and ShuHenberger, C. C., Clin. Cktm. Acta. 2,1 If (1937). '* Fink, K., Henderson. R. N.. and Fink. R. Mbbt. Cheat., 197, 44) (J957). 14 Gsrtier, S. M., Arehs Bioekem. Bbpkys., 60,400 (1939). * Caimclakis, E. S.,J. bM. Ckem., 221. 315 (1936). Hayatsu. R,, Science, 146, 1291 (1964). Evidence for downwind flights by host-seeking mosquitoes Tits behaviour of flying insects which make use of airborne chemicals in their search for food, oviposition sites or sexual partners can be separated into two phases, the search flight bringing them into contact with tite attraetant 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 are known to fly upwind as they approach a warm-blooded hoslT For most Insects relatively little is known of the pattern of the preceding search flight which i laskdl* 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 tire downwind side, that is they nppeuted to have been flying upwind, regardless of the presence or absence of a host (ref. 10 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 and so provlde a measure of protection from their attacks. The barrier would need lo be sufficiently far away for the mosquitoes to encounter it before they detected Ihc presence of the host, so tha) directed responses towards the host would not be elicited. This distance was estimated by Gillies and Wilkes" to be less than II m for host the stee of a man. A host stationed at this distance upwind