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Titolo:
RESPONSE OF LEAD CYCLING IN THE SURFACE SARGASSO SEA TO CHANGES IN TROPOSPHERIC INPUT
Autore:
VERON AJ; CHURCH TM; FLEGAL AR; PATTERSON CC; EREL Y;
Indirizzi:
UNIV AIX MARSEILLE 3,GEOSCI ENVIRONNEM LAB,CNRS,CASE 431 F-13397 MARSEILLE 20 FRANCE UNIV DELAWARE,INST MARINE STUDIES NEWARK DE 19716 UNIV CALIF SANTA CRUZ,INST MARINE SCI SANTA CRUZ CA 95064 CALTECH,DIV GEOL & PLANETARY SCI PASADENA CA 91125
Titolo Testata:
JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS
fascicolo: C10, volume: 98, anno: 1993,
pagine: 18269 - 18276
SICI:
2169-9275(1993)98:C10<18269:ROLCIT>2.0.ZU;2-F
Fonte:
ISI
Lingua:
ENG
Soggetto:
WESTERN NORTH-ATLANTIC; TRACE-METALS; ISOTOPE RATIOS; SUSPENDED PARTICLES; PB-ISOTOPES; OCEAN; INDUSTRIAL; SEDIMENTS; AEROSOLS; PRECIPITATION;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
43
Recensione:
Indirizzi per estratti:
Citazione:
A.J. Veron et al., "RESPONSE OF LEAD CYCLING IN THE SURFACE SARGASSO SEA TO CHANGES IN TROPOSPHERIC INPUT", J GEO RES-O, 98(C10), 1993, pp. 18269-18276

Abstract

Lead and its stable isotopes have been analyzed in surface water samples (0-600 m) and trapped particles collected at the Bermuda Atlantic Time Series Station (U.S. Joint Global Ocean Flux Study) in April and November 1989. These results are compared with wet atmospheric lead deposition as determined from precipitation continuously collected in Bermuda since August 1988 as part of the Atmosphere-Ocean Chemistry Experiment program. Despite an expected seasonal variability, lead concentrations in surface waters have clearly decreased by 30 to 40% since 1979 in response to a corresponding decline by a factor of 5 to 8 of thetropospheric deposition. This result is corroborated by stable lead isotope measurements with Pb-206/Pb-207 ratios which are significantly less radiogenic (1.18-1.20) in the first 500 m of the 1989 profile than those measured in 1984 (1.20-1.21). This isotopic shift reflects changes of lead ore supply in the United States as well as a relative increase of the Eurafrican contribution to lead input in the northwest Atlantic that is likely due to the reduction of lead emissions from gasoline consumption in North America. This fast response of lead to interannual variations of the tropospheric input into surface waters is related to its efficient bioreactivity, as demonstrated with a sediment trip deployed at 150 m in April 1989. Sediment trap results show the rapid penetration of lead into the first 200 m associated with large particles during a period of high plankton activity. Retrospective isentropic air mass trajectories in three dimensions coupled with the precipitation events collected in Bermuda in 1988-1989 show that 30 to 40% of the annual lead deposition originates from the trade easterly meteorological regime. This input is clearly evidenced with lead isotopic signals observed in surface waters (0-100 m) in April and November 1989. We show that lead accumulated in the seasonal mixed layer (0-50 m) reflects this atmospheric input. Taking into account the isotopic signalmeasured in this mixed layer (1.178+/-0.001) as well as the respective contribution of the temperate westerlies and trade easterlies to atmospheric lead deposition to the Sargasso Sea, we calculate that the isotopic signature from the Eurafrican regions is 1.155 (+/-0.004). Based on these results, we calculate that the actual Pb-206/Pb-207 averageratio in surface waters of the Sargasso Sea is 1.188 (+/-0.004).

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Documento generato il 18/09/20 alle ore 20:12:24