Sediment cores from nine lakes in southern Norway (N) and six in northern New England (NE) were dated by 37 Cs, 210Pb and in NE also by pollen, and were analyzed geochemically and for diatoms. Cores from two N and three NE lakes were analyzed for cladocerans. 37 Cs dating is unreliable in these lakes, probably due to mobility of Cs in the sediment. In Holmvatn sediment, an up-core increase in Fe, starting ca. 1900, correlates with geochemical indications of decreasing mechanical erosion of soils. Diatoms indicate a lake acidification starting in the 1920's. We propose that soil Fe was mobilized and runoff acidified by acidic precipitation and/or by soil acidification resulting from vegetational succession following reduced grazing. Even minor land use changes or disturbances in lake watersheds introduce ambiguity to the sedimentary evidence relating to atmospheric influences. Diatom counts from surface sediments in 36 N and 31 NE lakes were regressed against contemporary water pH to obtain coefficients for computing past pH from subsurface counts. Computed decreases of 0.3-0.8 pH units start between 1890 and 1930 in N lakes already acidic (pH 5.0-5.5) before the decrease. These and lesser decreases in other lakes start decades to over a century after the first sedimentary indications of atmospheric heavy metal pollution. It is proposed that the acidification of precipitation accompanied the metal pollution. The delays in lake acidification may be due to buffering by the lakes and watersheds. The magnitude of acidification and heavy metal loading of the lakes parallels air pollution gradients. Shift in cladoceran remains are contemporary with acidification, preceding elimination of fishes.
The distribution of 222Rn has been measured in the sixteen counties of Maine, U.S.A. by liquid scintillation counting of water samples from more than two thousand public and private wells. Three hundred and fifty of these wells have been characterized for geology and hydrology. Airborne radon has been measured in seventy houses with grab samples and in eighteen houses for 5-7 days each with continuously recording diffusion-electrostatic radon detectors. Concentrations of radon in water ranged from 20 to 180,000 pCi/l. Granite areas yielded the highest average levels (mean = 22,100 pCi/l.; n = 136), with considerable intra-granite variation. Metasedimentary rocks yielded levels characteristic of the lithology for metamorphic grades ranging from chlorite to andalusite. Sillimanite and higher-grade rocks yielded higher 222Rn levels, probably due to the intrusion of uranium-bearing pegmatites in these terranes. Airborne 222Rn in homes ranged from 0.05 to 210 pCi/l. At the high end of this range, doses will exceed recommended industrial limits. In some homes only a small fraction of the airborne 222Rn was due to the water supply. Average 222Rn levels in domestic water supplies for each of the 16 counties, calculated by areally averaging rock types and their associated 222Rn levels, were found to be significantly correlated with rates for all cancers combined and rates for lung and reproductive cancers in the counties. Although numerous factors other than cancer induction by indoor daughter exposures may be responsible for the observed correlations, these have not been investigated in detail.
In
greater Augusta of central Maine, 53 out of 1093 (4.8%) private
bedrock well water samples from 1534 km2 contained [U]
>30 μg/L, the U.S. Environmental Protection Agency’s
(EPA) Maximum Contaminant Level (MCL) for drinking water; and 226
out of 786 (29%) samples from 1135 km2 showed [Rn] >4,000
pCi/L (148 Bq/L), the U.S. EPA’s Alternative MCL. Groundwater
pH, calcite dissolution and redox condition are factors controlling
the distribution of groundwater U but not Rn due to their divergent
chemical and hydrological properties. Groundwater U is associated
with incompatible elements (S, As, Mo, F, and Cs) in water samples
within granitic intrusions. Elevated [U] and [Rn] are located within
5–10 km distance of granitic intrusions but do not show correlations
with metamorphism at intermediate scales (100−101 km). This spatial association is confirmed by a high-density
sampling (n = 331, 5–40 samples per km2) at local scales (≤10–1 km) and
the statewide sampling (n = 5857, 1 sample per 16
km2) at regional scales (102–103 km). Wells located within 5 km of granitic intrusions are at risk
of containing high levels of [U] and [Rn]. Approximately 48 800–63 900
and 324 000 people in Maine are estimated at risk of exposure
to U (>30 μg/L) and Rn (>4000 pCi/L) in well water, respectively.
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