8273

• UCREFRP Catalog Number: 8273
• Author: U.S. Bureau of Reclamation, U.S. Fish and Wildlife Service, U.S. Geological Survey and U.S. Bureau of Indian Affairs.
• Title: Guidelines for Interpretation of the Biological Effects of Selected Constituents in Biota, Water, and Sediment.
• USFW Year: 1998.
• USFW - Doc Type: \
• Copyright Material: NO

I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I

( CONSTITUENTS OF" CONCERN :)

M~enlc

Descri ption

Arsenic (As) is a metalloid, with properties
intermediate between those of a metal and a
nonmetal. In its pure state, it generally takes
the fon:n of a dense, gray metal, although a
much lighter, yellowish powder may be
formed through sublimation of the vapor. In
nature, arsenic exists in four oxidation states
(As-3, Aso, As+3 [referred to as MAs (ill)"], and
As+s ["As (V)"]), and it may be in either
organic or inorganic forms. Its common ores
include the minerals arsenopyrite (FeAsS) and
realgar (As2S2). Arsenopyrite is a white to
gray orthorhombic mineral resembling pyrite,
commonly found in lead and silver veins.
~ealgar ~orms red to reddish-orange nodules
more vems and similarly colored coatings
around some hot springs.

Occurrence

Arsenic is ubiquitous-present in air, water,
soil, plants, and other living organisms. In
water, common forms of arsenic are As (III),
As (V), methane arsonic acid, and dimethyl-
arsinic acid (EP A 1985). Inorganic As (V) is
the most common species in water. As (III) in
water converts readily to As (V) under aerobic
conditions (Clement and Faust 1973), but
some As (III) may persist depending on
microorganisms, temperature, and other
factors.

Background Concentrations.-The arsenic
concentration in soil normally ranges from
1 to 50 mg/kg, though it does not generally
exceed 10 mg/kg (Brown et al. 1983), and in
water it is normally <10 pg/L (Eisler 1988).
Terrestrial flora and fauna, birds, and
freshwater biota usually contain <1 mg As/kg

by wet weight (ww). Arsenic at 0.27 mg/kg
ww (=: 1 mg/kg dry weight [dw]) is reported
to be the 85th percentile concentration for
freshwater fish (Schmitt and Brumbaugh
1990), and background concentrations in
terrestrial plants range from 0.01 to 1.7 mg/kg
dw (Bodek et al. 1988). Concentrations of
arsenic in livers of adult amphibians collected
in an apparently uncontaminated area
averaged 0.164 mg/kg ww (Byrne et al. 1975).
These levels are sometimes much higher in
biota collected near areas with high geo-
thermal activity and near manufacturers of
arsenical defoliants and pesticides (Eisler
1988).

Each year, as a result of agricultural and
industrial activities, large quantities of
arsenicals that may be hazardous to fish and
wildlife are released into the environment
(Eisler 1988). Agricultural applications
provide the largest artificial source of arsenic
in the environment (Eisler 1988). It is
contained in wastes from the production of
certain herbicides, fungicides, insecticides,
algicides, and wood preservatives (Brown et
al. 1983); in particular, sodium arsenite was
commonly used as an aquatic herbicide
between 1940 and the 1970's, especially in the
United States (Tanner and Clayton 1990).
Arsenic is also present in large amounts in
water contaminated by mine tailings, smelter
wastes, and natural mineralization (Eisler
1988). EP A also states that sources of arsenic
in drinking water include glass, electronic
wastes, and orchards (EPA 1994).

Summary of Effects

Arsenic is not normally considered an
essential element to most species, and it has
been shown to be both teratogenic and

8