Inter- and intra-annual variations of Pb/Ca ratios in clam shells (Mercenaria mercenaria): a record of anthropogenic lead pollution?
Gillikin, D.P.; Dehairs, F.A.; Baeyens, W.F.J.; Navez, J.; Lorrain, A.; André, L. (2005). Inter- and intra-annual variations of Pb/Ca ratios in clam shells (Mercenaria mercenaria): a record of anthropogenic lead pollution? Mar. Pollut. Bull. 50(12): 1530-1540. dx.doi.org/10.1016/j.marpolbul.2005.06.020
In: Marine Pollution Bulletin. Macmillan: London. ISSN 0025-326X; e-ISSN 1879-3363
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| Keywords |
Chemical elements > Metals > Heavy metals
Chemical elements > Metals > Heavy metals > Lead
Coastal zone
Man-induced effects
Sediments
Mercenaria mercenaria (Linnaeus, 1758) [WoRMS]; Mollusca [WoRMS]
ANW, USA, North Carolina, Pamlico Estuary [Marine Regions]
Marine/Coastal |
| Author keywords |
lead; anthropogenic pollution; proxy record; metals; mollusk; coastal sediments; North Carolina |
| Authors | | Top |
- Gillikin, D.P.
- Dehairs, F.A., more
- Baeyens, W.F.J., more
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- Navez, J.
- Lorrain, A.
- André, L.
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| Abstract |
In this study, we re-assess the use of bivalve shells as a proxy of lead pollution. Previous studies have stressed that shells display little variability compared to soft tissues and thus are better for pollution biomonitoring. However, in this manuscript we illustrate that there is large inter- and intra-annual Pb variability between shells of the clam Mercenaria mercenaria collected in North Carolina, USA. Therefore, year to year, as well as intra-annual variations in Pb/Ca ratios should be interpreted with caution. Despite this variability, we were able to obtain an annual Pb chronology from 1949 to 2002 using 11 shells collected at different times which clearly exhibited the late 1970’s peak in Pb from leaded gasoline use. This indicates that when enough specimens are pooled together, bivalve shells can be used to reconstruct large, long term changes in environmental Pb concentrations. Our data compare well with other studies of aragonite clams from sites with low regional lead pollution. From this we conclude that the Cape Lookout region of North Carolina has not received extensive pollution over the 1949-2002 period. The Pb concentration in shells growing in the 1949-1976 period was not significantly different from those growing in the 1982-2002 period, although other proxies suggest that the 1949-1976 period should be considerably higher. Therefore, our data suggest that there is still a modern low-level source of Pb in the coastal North Carolina environment. |
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