Document mqk6D7MYEXZGV5xE90mLJVwdZ

Nature Vo!. ?52 November 29 1974 J. A. M'. M. Kors J. F. v;d. Vate JAN--6 `1975 L. T. Hermans G. Diddets Slichting Reactor Centrum Nederland, Hoofdkantaor-'Sehevcningsweg 112, 'S-Crnvcnhopc^Ondcrsoekcentrnni: Petten (N-H),,} The Netherlands ' Received June 28zrcviscd August 28, 1974. V i 1 Vometn, R. A'., find Whitby, K. T., J. Colloid Interface Set., 25' 368-576 (1967). ' . * Sibber, W., nfid llachsbart, H,, Env. Set. Tcclmol,,3, 1280-1296 (1969). r '" * Wriglcy, N. CV, J. Ultrnslnicl. Rex., 24, 454-464 (l?'68). , 4 Slblxr. W., F-lnclisbart, II., and Hochralncr, D., Stanh, 30, 277-285 .1 Sib(,b9e7r0,)'W., in Assessment of Airborne Partlelex (canrt, by Mercer, Morrow, nmj Sibber), 249 (C. C. Thomas, Springfield. 1972). * Drake, R. Lv in Topics In Current Aerosol Research (t'arlz) (edit. by Hidy, arid ftrock), 201, (Pergamon, Oxford, 19(2). j. Decline of PCD conccnfralions in Norlh Allantic surface water PoLVCitLOlUmiflTtNYi. (PClt) concentrations iiTNbrth Atlanlic surface wa(cr5,buvc declined forlyfold since 1972, following the cessation of .Certain industrial uses of those veompounds. Industrial sales of PCD for use in products which'would allow leakage to thc-Cnvironmcnt, for example in plastits, inks and paints were stopped in the United States and Swpdcn during 1970-71'; and`in 1972-73 other European countries and Japan initiated a similar action*. In 1971 and 1972 overage surface conccntration^of PCD in the open North Atiantifc.Ocean were about 30 ng H (ref. 3 and C. E. Olncy and J. J. Quinn, unpublished), fiy April of 1973 the concentration in )hc Sargasso Sea had been reduced to I ng l-1 (ref. 4); five months later we found that the`decline had levelled at 0.8 ng 1~', a concentration which was still present in February 1974 in thd. north-west Atlantic. The accumulated data arc presented in Table 1. These observations revealing a reduction in surface water concentra tions of PCD compare well with our February 1^74 measure ments of a tenfold decrease of PCD in the atmosphere over the north-west Atlantic since 1973 (ref. 5), and a fivefold decrease -------- -- *- - _- ____ . .. *, Table 1 PCB concentrations In North Atlantic surface waters* ' 1971-74 ` Date McanPCBt (ng 1 _1> Sampling region No. of Ana'lyticalf Ref. samples nf?thod 8/71 7/72 1/72 9/72 4/73 . 9/73 9/73 a/?4 25 / Iceland lo Nova Scotia 8 41 u Newfoundland to Portugal 6 36 Porlugallo Norwegian Sea II 30 Woods Hole lo Bermuda 27 1 Sargasso Sea 6 2 i Aeorcsto09N,40W l to Barbados . 10 0.8 t Sargasso Sea lo , New York Bight 9 0.8 ( New England ; Continental Shelf 6 I 3s 3 3 4 3* 3 3 * 0-30 m. ----------------- t Blank values for PCB in methods A, B and C werfc 0.9, 0.5 and 0.3 ng 1respectively. Replicate analyses using mc(hods B or C showed an average variation or;| 20%atlhc 1 ng|-' Icy'cl. Quantita tion methods arc presented in refs 3, 5, 6. e I A, Extraction of 0.5-3.R I with chloroform or dichloromcthanc: J, extraction of.20I wilh 5% erher in hexane; C, pissing 40-60 ( through Ambcrlllc XAD-2 resin followed by elution-with boiling acetonitrile. *' 1C. E. OIney and J. J. Quinn, unpublished information. . 387 since 1972 in . PCB content of mixed plankton collected along 09"N latitude in September of 1973 (ref. fi). The data require (hat about 2x10' tons of PCD 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 and horizontal advcction and diffusion; (2) association of PCB with sedimenting particles; (3) evaporative codistillation into the atmosphere and (4) bio logical and chemical degradation. . The information obtained from the monitoring of bomb fallout radionuclides is relevant lo 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 PCD concentrations in North Atlantic subsurface waters*, 1973 Date of collection Position *nd analyses! Latitude Longitude Depth PCD (m) (ng I'M 19/9/73 09 00' N 40'00'W f 2/10/73 32 25' N 70 20' W 10 100 200 400 500 700 1,000 2,000 3,000 10 100 300 600 900 5,100 4.3 2.0 1.4 1.1 J.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 I *' level was 40%. The blank was produced by recycling 40 I of XAD-2 extracted seawater through the entire procedure and averaged 0.3 ng l **. t Method C was used. 1963. For example, stronlium-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 too slow to explain the observed rate. The rate of PCB removal from the surface waters more closely resembles the behaviour of the plutonium nuclides "-*,0Pu 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 rates of 70-392 m yr_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 2x 104 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 water column, the concentrations to 3,500 m would still be Jess than 2 ng l"'. Two 1973 profiles of PCB 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 VV revealing very low PCB levels at the surface, was simitar to nine other stations In the Norlh American Basin the same year. We are, at present, unable lo ascertain the relative Importance of evaporative codistillation of PCB from the surface water or of biogcochcmicat dcgradalion. Eilhcr process could explain the lower surface water concentrations in the Norlh American Basin. There is, as yet, no evidence of biological 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 OSW 0 2 8 8 1 6 STLCOPCB4012778 *... ' s determine the mcclfanism of this clucicnt transfer ptqccss are in progress. . , This work was supported by an NSF grant to the Jnterna- tionnl Decade of Ocean Exploration. * ** Georoe R. Harvey V William G. Steinmaver Helen P. Miklas.' Woods Hole Oceanographic Institution, '. . Woods Hole, Massachusetts 02543 * * Received June 27; rtfviscd Joly 15, 1974. . # ; * Chem. Lttgng. Hen}, July 20, 31 (1970). ,, ... * O.E.C.D. Press Release,Paris,February1, 197J. : * Harvey, <3. R., Stefnhaucr, W. G., and Teat, J. M., Science, 180, 643-644 (1973). * Itidlcman, T. F., and Olncy, C. E., Science, 1R3, 516-518 j(l974). * Harvey, O. R., and>S(cinhaucr, W, G., Atmos. Environ., 8,--777--782 (1974). : * Harvey, O. R., Miklas. H. P., Bowen, V. T., and Swinhaucr, W. O.. J. Mar. firs., 32,103-118(1974). ./ * Bowen, V. T., Noshkin, V. E., Volchok, H. L., and Suglhara, T. T., Science, 164, 825 -287 (1969). * Nosbkin, V, E,, nn'<} Bowen, V. T., in Radioactive Contamination of the Marine Lnvifonment, 671-686 (IAEA, Vienna, 1973), ....... .... ............. .................. ...----I........in................ ~i| ...... Origin proposed for non-protein anumrricids ifi meteorites ' ^ The amino acids thal have been identified in several meteorites'-* can be divided into'.two classes: those present in prot'ejns and those which arc not. The presence of the non-protcio amino elds, D- and L-&-amioisobutyric acid and p-atapine, is described as evidence for the indigenous origin of mttcorite amino acids and against terrestrial contamination1. It is implied that these p-amino' acids arise by prebiolic condensation of ammonia, methand," hydrogen, water and other simple prim ordial molecules*. T^hc P-amino acids and other amino acids can arise from simple molecules by Fischer-Tropsch synthesis in the laboratory. Hydrogen, carbon dioxide and ammorua 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 amirjit? acids occurred in a sirqulated primitive atmosphere of methane, ammonia and water, followed by acid hydrolysis of the products. P-AJanlnc was obtained in high yield, relative to other, amino acids, end the straight-chain compound, p-amino-n-butyric acid*. These amino'acids were postulated to arise respectively from hydrolysis of P-aminopropionitrile and the nitfjlc inter mediate arising from addition of ammonia to crotononitrile. Evidence for this route was tire identification of succinic acid and N-mcthyl-p-al^ninc which arc likely hydrolysis products of nitrile intermediate?. Production of P-aminoisobutyric Jfeid was not reported in these experiments*. P-Amlnoisobulyric acid is a rare amino acid with a curious distribution in natliirc. It has been isolated only from human urine', iris bulbs', flatworms* and edible mussels*. \Man is probably the only mammalian species to excrete d-(--)f\-amino- Isobutyric acid10 though there is chromatographic evidence for Its presence fn rabbit urine". Metabolic experiments suggest that the pyrimidine bast thymine, from nucleic acid catabolism, is Che precursor of p-aminoisobutyric acid in the human'*'1*. Similarly, metabolic production of P-alanine in rat liver is from the pyrimidine uracil". 4. By analogy with.-jhese known reaction sequences catalysed biologically, I suggest that heterocyclic compounds could also act as precursors for the P-amino acids found in meteorites. In this case, scission of the ring of heterocyclic compouncfs'formcd preblolically .woulrj' occur under the catalytic conditions of extremes of temperature and radiation thought to occulta space. Nature Vtd. 252 N.ovri.nhcr 29 1974 The purines, adci,.,ic and guanine, and a substance resembling uracil have been detected in the Orgucil meteorite". Xanthine, thymine, uracil und detivatives have also l>ccn obtained experi mentally by mimicking supposed prcbiotic conditions*. Tin's chemical route to certain non-protein amino acids described above would presumably give racemic mixtures Of both stereoisomers, for example, both D-, and L-fi-aminoisobutyric acid, as found in meteorites1. It would be interesting to know if thymine, dihydroihyminc, uracil and related com pounds, when heated under supposed prcbiotic conditions, did give traces of the p-amino acids. - Department of Biochemistry, Chelsea College, University of London, Monresa Road, Chelsea, London SWJ 6LX, UK D. F. Evered ' Received July 4, 1974. ' 1 Lawless, J. O., Kvcnvotdcn, K. A., Peterson, E.. Ponnamperuma, . C., and Moore, C,, Science. 173, 626 (1971). * Lawless, J. G., Kvcnvoldcn, K, A., Peterson, E., Ponnamperuma, C,, and Jaroscwick, E., Nature, 236, 66 (1972). ' Miller, S. L,, Science, 117, 528 (1953). * Anders, E., Hayatsu, R., and Sludicr, M. H., Science, 182, 781 . (1973). * Lawless, J. G., ond Boynton, C. D., Nature, 243, 405 (1973). * Crumplcr, H. R., Dent, C. E., Harris, H., and Wcslalt, R. O., Nature, 167, 307(1951). ' Asen, S., Thompson, J. f:., Morris, C. J., and Irreverre, F., J. btol. Chem., 234, 343 (1959). * Campbell, J. W,, Biol. Dull., 119, 7} (I960). * Awapara, J., and Allen, K., Science, 130, 1250 (1959). 10 Evered, D. F., Comp. Bioehem. Physiol., 23, 163 (1967). 11 Block, W. D., and Hubbard, R. W., Acelts Dioclicm. Biophys., 96, 557 (1962). 15 Awapara. J., and Shullcnberger, C. C., Clin. Chim. Acta. 2, 119 , (1957). *' Fink, K., Henderson, R. N,,and Fink, R. M,,J. biol. Chem., 197, 441 (1957). *4 Gartlcr, S. M., Archs Bioehem. Biophys., 80, 400 (1959). ** Cannelakis, E. S ,J. biol. Chem.. 221, 315 (1956). ' " Hayatsu, R., Science, 146, 1291 (1964). Evidence for downwind flights by host-seeking mosquitoes The behaviour of (lying 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 (he attractant plume and the approach (light leading them to its source1-*. The second phase is characterised by upwind orientation in response to the appropriate chemical stimuli5-*. Mosquitoes arc known to fly upwind as they approach a warm-blooded host'-*. 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 upwind1. 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 of a host (ref. 10 and W. F. Snow, unpublished). Here we report experiments that unexpectedly provide evidence for the opposite type or bchnviour. If the search flight is in a generally upwind direction, It should be possible to divert mosquitoes round a host by selling up a barrier on the downwind side and so provide 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 the presence of the host, So that directed responses towards the host would not be elicited. 1 his distance was estimated by Gillies and Wilkes" to be less than 18 m for a host the size of a man. A host stationed at this distance upwind DSW 0 2 8 8 1 7 STLCOPCB4012779