Geochemistry: Exploration, Environment, Analysis; May 2002; v. 2; no. 2;
p. 175-184; DOI: 10.1144/1467-787302-021
© 2002 Geological Society of London
An atmospheric pollution history for leadzinc mining from the Ystwyth Valley, Dyfed, mid-Wales, UK as recorded by an upland blanket peat
T. M. Mighall1,
J. P. Grattan2,
S. Timberlake3,
J. A. Lees4 and
S. Forsyth1
1 Centre
for Quaternary Science, Geography, School of Science and the
Environment, Coventry University, Priory Street, Coventry
CV1 5FB, UK (e-mail:
GEX043{at}COV.AC.UK)
2 Institute
of Geography and Earth Sciences, University of Wales,
Aberystwyth SY23 3DB,
UK
3 Early Mines Research
Group, 98 Victoria Road, Cambridge CB4
UK
4 CERC, Geography, School
of Science and the Environment, Coventry University, Priory Street,
Coventry CV1 5FB,
UK
This
paper presents records of the atmospheric deposition of lead and zinc
close to a former metal mining area as recorded by an upland blanket
peat that has accumulated on the northern slopes of the Ystwyth valley,
Dyfed, mid-Wales, UK. The research objective was to explore the
possibility that the peat contained a geochemical record of the
pollution generated by mining activity during the last four millennia.
Four monoliths were extracted from the blanket peat to reconstruct the
pollution history of lead and zinc mining. Three different geochemical
measurement techniques were employed, and five lead and zinc profiles
have been reconstructed, two of which are radiocarbon-dated. In the
radiocarbon-dated monoliths lead enrichment occurs in the peat during
the Roman occupation whilst both lead and zinc concentrations increase
from the Mediaeval period until the early part of the 20th century.
Similar enrichment of lead and zinc is shown in the remaining profiles.
Whilst other possible explanations are discussed, it is argued that the
high lead concentrations represent evidence of atmospheric pollution
caused by mining. Zinc, however, may have suffered from
post-depositional mobility. The results of this suggest that lead is
largely rendered immobile in blanket peat and can be used to
reconstruct atmospheric pollution histories in former lead mining
areas.
KEYWORDS: peat, geochemical
monitoring, lead, zinc, mining, Ystwyth
valley, Wales
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