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An environmental record of lead isotopes over four centuries at Law Dome, Antarctica

Entry ID: ASAC_1092

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Summary

Abstract: Antarctic ice provides an archive of Earths atmospheric composition over time. It therefore records evidence of human impact on the atmosphere. Lead is a toxic element, whose isotopic fingerprint can also be used as a tracer. This project will investigate a 400 year Pb pollution record in ice from Law Dome.

From the abstracts of the referenced papers:

Techniques for Pb measurements have ... reached the stage where Antarctic ice with sub-picogram per gram concentrations can be reliably analysed for isotopic composition. Here, particular attention has been given to measuring the quantity of Pb added during the decontamination and sample storage stages of the sample preparation process because of their impact on accuracy at low concentrations. These stages, including the use of a stainless steel chisel for the decontamination, contributed ~5.2pg to the total sample analysed, amounting to a concentration increase of ~13fg per gram, which is significantly less than expected. Consequently the corrections to the isotopic ratios and concentration were also smaller. Other contributions to the blank, such as Pb fallout onto critical working areas in the HEPA-filtered laboratories, were also relatively small as was the amount of Pb leached from preconditioned perfluoroalkoxy (PFA) beakers during sample processing. The ion source contributed typically 89plus or minus 19 fg to the blank. Although this was relatively large, its influence depended upon the amount of Pb available for analysis and it had the greatest impact when small volumes of samples with a very low concentration were analysed. A 15 months investigation of the leaching characteristics of Pb from a low-density polyethylene (LDPE) sample storage bottle showed 11 fg per cm per cm per day was released immediately following the initial 2 months cleaning process, but this decreased to immeasurable values after a further 3 months of cleaning.

Lead isotopic compositions and Pb and Ba concentrations have been measured in ice cores from Law Dome, East Antarctica, covering the past 6500 years. 'Natural' background concentrations of Pb (~0.4 pg/g) and Ba (~1.3 pg/g) are observed until 1884 AD, after which increased Pb concentrations and lowered 206Pb/207Pb ratios indicate the influence of anthropogenic Pb. The isotopic composition of 'natural' Pb varies within the range 206Pb/207Pb=1.20-1.25 and 208Pb/207Pb=2.46-2.50, with an average rock and soil dust Pb contribution of 8-12%. A major pollution event is observed at Law Dome between 1884 and 1908 AD, elevating the Pb concentration four-fold and changing 206Pb/207Pb ratios in the ice to ~1.12. Based on Pb isotopic systematics and Pb emission statistics, this is attributed to Pb mined at Broken Hill and smelted at Broken Hill and Port Pirie, Australia. Anthropogenic Pb inputs are at their greatest from ~1900 to ~1910 and from ~1960 to ~1980. During the 20th Century, Ba concentrations are consistently higher than 'natural' levels and are attributed to increased dust production, suggesting the influence of climate change and/or changes in land coverage with vegetation.

The fields in this dataset are:

Sample
Date
206Pb/207Pb
208Pb/207Pb
206Pb/204Pb
Pb concentration
Ba concentration

Related URL

Link: GET DATA

Description: Download point for the data

Geographic Coverage

(Click for Interactive Map)

Spatial coordinates

N: -66.0

S: -66.0

E: 110.0

W: 110.0

Temporal Coverage

Start Date: 1998-09-30

Stop Date: 2001-03-31

Paleo Temporal Coverage

Paleo Start Date: 7500 YBP
Paleo Stop Date: 0 YBP
Chrono Unit:

PHANEROZOIC > CENOZOIC > QUATERNARY > HOLOCENE

Location Keywords

CONTINENT > ANTARCTICA

GEOGRAPHIC REGION > POLAR

Data Resolution

Latitude Resolution: 1 deg.
Longitude Resolution: 1 deg.
Horizontal Resolution Range: 100 km - < 250 km or approximately 1 degree - < 2.5 degrees
Temporal Resolution: eight-day
Temporal Resolution Range: Weekly - < Monthly

Science Keywords

ATMOSPHERE > AEROSOLS > AEROSOL BACKSCATTER

ATMOSPHERE > AEROSOLS > AEROSOL EXTINCTION

ISO Topic Category

BIOTA

GEOSCIENTIFIC INFORMATION

OCEANS

Quality At this juncture this dataset is complete. As no evidence to the contrary has been established, it is concluded that this dataset is logically consistent.

Access Constraints See the investigator for details.

Use Constraints This data set conforms to the PICCCBY Attribution License
(http://creativecommons.org/licenses/by/3.0/).

Must be cited properly

Data Set Progress

IN WORK

Originating Center

AAD

Data Center

Australian Antarctic Data Centre, Australia

Data Center URL: http://data.aad.gov.au

Data Center Personnel
Name: DATA OFFICER AADC Phone: +61 3 6232 3244 Fax: +61 3 6232 3351 Email: metadata at aad.gov.au Contact Address: Australian Antarctic Division 203 Channel Highway City: Kingston Province or State: Tasmania Postal Code: 7050 Country: Australia

Personnel

HARVEY MARCHANT

Role: INVESTIGATOR

Role: TECHNICAL CONTACT

Role: DIF AUTHOR

Phone: +61 419390492

Fax: +61 2 6125 5544

Email: harvey.marchant at anu.edu.au

Contact Address:

Department of Earth and Marine Sciences

Australian National University

City: Canberra

Province or State: ACT

Postal Code: 0200

Country: Australia

Creation and Review Dates

DIF Creation Date: 1999-10-07

Last DIF Revision Date: 2009-08-14

Future DIF Review Date: 1999-10-07

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