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Plummers Island

Studies of element accumulation by lichens

Background:

· Lichens have been used to study changes in air quality in the Washington D.C. area since the work by Mason E. Hale, Jr. beginning in 1970.

· The first studies were of the saxicolous lichen Flavoparmelia baltimorensis, a common lichen at Plummers Island and elsewhere in the region.

· Lichens were sampled from Plummers Island and nearby Bear Island 6 km upstream from Plummers Island. In addition, comparable samples were collected from Stony Man Mountain in the Shenandoah National Park, and historical collections dating to 1907 were obtained from the U.S. National Herbarium.

· All specimens were analyzed initially for elemental Pb using inductively coupled plasma spectroscopy.

Pb conc in F. baltimorensis (mean µg/g ± SE):

Year	Plummers Is	Bear Is	Stony Man
1907	82.3 ± 8.2
1938	127.8 ± 14.8
1958	327.9 ± 12.6
1970	1160.5 ± 148.8
1979	1131.0 ± 179.3	273.0 ± 50.6	218.5 ± 100.9
1982	787.2 ± 25.3	174.0 ± 53.2
1988	418.3 ± 44.8	123.4 ± 18.6	66.7 ± 1.0
1992	136.8 ± 7.21	49.4 ± 3.2	25.5 ± 2.3
2000	72.8  ± 13.2	29.0  ± 5.4	18.6  ± 7.1
2004	30.7 ± 4.7	26.4 ± 2.7	15.5 ± 0.7
2009	76.7 ± 0.8	14.9 ± 3.1	12.4 ± 1.9

Changes in air quality at Plummers Island:

§ Earliest recorded concentrations of Pb in lichens were around 100 μg/g and concentrations steadily increased until 1965, when the American Legion Memorial Bridge was built.

§ After 1965, the concentrations of lichen Pb increased dramatically until the early 1980's when Pb began o be eliminaated from gasoline.

§ Recent samples show historically low Pb levels at all three locations.

Sulfur and other elements also show reductions:

§ A similar trend has been found for other elements (S, N, Cd, Cr, Cu, Ni, Zn) and in other lichen species. Given here are sulfur concentrations (mean µg/g ± SE) for Flavoparmelia baltimorensis at Plummers Island additional study sites:

Year	Plummers Is	Bear Is	Stony Man
1983	2500 ± 50.0
1988	1860 ± 15.0	2070 ± 6.0	1340 ± 11.0
1992	1560 ± 3.0	1800 ± 0.0	1300 ± 5.0
2000	1500  ± 4.0	1580  ± 1.0	1330  ± 2.0
2004	1660 ± 19.0	1660 ± 49.0	1250 ± 17.0
2009	1673 ± 44.1	1677 ± 73.5	1307 ± 48.8

Further information can be obtained from published papers, including:

· Lawrey, JD, Hale, ME, Jr. 1979. Lichen growth responses to stress induced by automobile exhaust pollution. Science 204: 423-424.

· Lawrey, JD, Hale, ME Jr. 1981. Retrospective study of lichen lead accumulation in the northeastern United States. Bryologist 84: 449-456.

· Lawrey, JD. 1993. Lichens as monitors of pollutant elements at permanent sites in Maryland and Virginia. Bryologist 96: 339-341.

Mason E. Hale, Jr. (1928-1990) was curator of lichens at the Smithsonian Institution. He began a series of long-term studies of lichens (such as Flavoparmelia baltimorensis and F. caperata - shown) as biomonitors of air quality in the 1970's at Plummers Island.

Location of sampling sites at Bear Island and Plummers Island, Maryland.