206Pb/207Pb Ratios in Tree Rings as Monitors of Environmental Change

详细信息    查看全文

• 作者：Shaun A. Watmough ; Richard J. Hughes ; and Thomas C. Hutchinson
• 刊名：Environmental Science & Technology
• 出版年：1999
• 出版时间：March 1, 1999
• 年：1999
• 卷：33
• 期：5
• 页码：670 - 673
• 全文大小：47K
• 年卷期：v.33,no.5(March 1, 1999)
• ISSN：1520-5851

文摘

Lead concentrations and ²⁰⁶Pb/²⁰⁷Pb ratios were measuredin annual tree rings of sycamore (Acer pseudoplatanusL.) growing at two woodland sites in northwest England.One site, at Prescot, was adjacent to a metal refinery in thecenter of a large urban conurbation while the site atCroxteth was part of an urban woodland at least 2 kmfrom the nearest major road. Lead concentrations and²⁰⁶Pb/²⁰⁷Pb ratios in surface soil were higher at Prescot thanat Croxteth. At both sites, Pb concentrations decreasedconsiderably in tree rings formed after 1970. At Croxteth,²⁰⁶Pb/²⁰⁷Pb ratios in tree rings formed between 1965 and 1987were relatively constant, around 1.16, but increasedsharply in wood formed after 1987 to over 1.17 in woodformed in 1993. This increase in the ²⁰⁶Pb/²⁰⁷Pb ratio reflectsthe recent reduction in Pb derived from vehicle emissionsthat has a characteristically low ²⁰⁶Pb/²⁰⁷Pb ratio. Therewas no corresponding increase in the ²⁰⁶Pb/²⁰⁷Pb ratio intree rings at Prescot, although Pb concentrations in treerings formed after 1986 remained unchanged. In addition,²⁰⁶Pb/²⁰⁷Pb ratios at Prescot were generally higher than atCroxteth, and there was considerable annual variation,which is probably due to the multiple sources of Pb at thissmall woodland site. ²⁰⁶Pb/²⁰⁷Pb ratios in sycamore treerings may be used to document historical changes in thesources of bioavailable Pb, which differ between sites,although the majority of Pb in tree rings at these two woodlandsites appears to have been derived from industrial andurban sources rather than from motor vehicle emissions.