8153

• UCREFRP Catalog Number: 8153
• Author: Jacobs, e. L. W.
• Title: Editor
• USFW Year: Series
• USFW - Doc Type: 1989
• Copyright Material: YES

38 MAYLAND ET AL.
riches Se in wet depositional fluxes to western Atlantic surface waters. They
measured an average of 30 and 170 ng Se/L in rainwater samples collected
over Bermuda and Lewes, DE, respectively. On occasion, values as high as
300 ng Se/L were encountered over the Lewes site. They calculated that the
wet depositional flux at Lewes, DE, was about 15 ng Se/cm2 per year (given
as 190 pmol/cm2 per year). That amount is equivalent to 1.5 g Se/ha an-
nually, which is about one-tenth the amount of fertilizer Se that is applied
annually in Se-deficient areas such as Finland and New Zealand. The wet
depositional flux calculated by Cutter and Church (1986) falls between the
values estimated by Ross (1985) for remote continental (75 pmol/cm2 per
year) and urban (840 pmol/cm2 per year) wet deposition.
Selenium's oxidation state in precipitation may be a sensitive oxidation-
reduction (redox) tracer (Cutter & Church, 1986). The authors found that
the range of selenite/selenate values was generally small [Se(IV)/5e(VI) _
1.26 ± 0.95]. Two samples with the highest selenite/selenate ratios (15-20)
came from storms traveling in northerly directions, placing the coal-fired
Indian River Station power plant 30 km upwind of the rain sampler. They
calculated an apparent redox intensity of the precipitation, but suggested that
more data were needed to accurately determine the oxidation intensity of
air masses.
Andren et al. (1975) reported that Se in the fly ash and aerosols retrieved
from the Allen Steam Plant was all in the elemental form (Se °). Cutter and
Church (1986) detected selenide plus elemental Se in only one sample account-
ing for 28~Io of the total Se. The remaining (72%) Se occurred as selenite
and selenate. Fly ash has been shown to contain sufficient concentrations
of bioavailable Se that it could serve as a supplemental nutrient source for
plants and animals (Furr et al., 1975, 1976a, 1977, 1978).
Suzuki et al. (1981) and Cutter (1978) reported that selenite was the major
Se species in rainwater samples collected in Japan and on the California coast.
Robberecht and van Grieken (1980) reported variable quantities of both
selenite and selenate in the rain and snow samples collected from an urban
area in Belgium.
Bioavailability of Aerosol Selenium
The chemical speciation of Se and the particle size of the carrier aerosol
are important in assessing its bioavailability. Oral ingestion is the primary
route of entry into the animal body for most trace elements, although in-
halation of Pb may be an important route for body Pb loads. Aerosols may
enter the body through the respiratory system and serve as another source
of Se. While the larger 1 to 20 µm MMAD particles are deposited primarily
in the nasal and bronchial region of the respiratory system, the submicron
particles are deposited predominantly in the lungs and have the greatest en-
richment in many of the trace elements, including Se (Campbell et al., 1978).
Medinsky et al. (1981) modeled the distribution and retention of Se in
rats after inhalation of elemental Se and selenious acid aerosols (0.6 µm
MMAD). They noted that the rate of absorption of these two Se forms into