Environmental Engineering Reference
In-Depth Information
7
Tools for assessing contaminated sediments in
freshwater, estuarine, and marine ecosystems
Donald D. MacDonald
1
& Christopher G. Ingersoll
2
1
MacDonald Environmental Sciences Ltd., Canada
2
United States Geological Survey, USA
7.1 Introduction
from remote sources. Owing to their physical and
chemical properties, many of these substances tend
to accumulate in sediments. In addition to providing
sinks for many chemicals, sediments can also serve
as potential sources of pollutants to the water column
when conditions change in the receiving water system
(for example during periods of anoxia, after severe
storms).
Traditionally, concerns about the management of
aquatic resources in aquatic ecosystems have focused
primarily on water quality. As such, early water
resource management efforts were often directed at
assuring the potability of surface water or ground-
water sources. Subsequently, the scope of these man-
agement initiatives expanded to include protection
of instream (i.e., fi sh and aquatic life), agricultural,
industrial, and recreational water uses. Although ini-
tiatives undertaken in the past 30 years have unques-
tionably improved water quality conditions, a
growing body of evidence indicates that management
efforts directed solely at the attainment of surface-
water quality criteria may not provide an adequate
basis for protecting the designated uses of aquatic
ecosystems.
In recent years, concerns about the health and
vitality of aquatic ecosystems have begun to re-
emerge in North America. One of the principal
reasons for this is that many toxic and bioaccumula-
tive chemicals, which are found in only trace amounts
in water, can accumulate to elevated levels in sedi-
ments. Some of these pollutants, such as organochlo-
rine (OC) pesticides and polychlorinated biphenyls
(PCBs), were released into the environment long ago.
The use of many of these substances has been banned
in North America for 30 years or more; nevertheless,
these chemicals continue to persist in the environ-
ment. Other contaminants enter our waters every
day from industrial and municipal discharges, urban
and agricultural runoff, and atmospheric deposition
7.2 Sediment quality issues and
concerns
Sediments represent essential elements of freshwater,
estuarine, and marine ecosystems. Nevertheless, the
available information on sediment quality conditions
indicates that sediments throughout North America
are contaminated by a wide range of toxic and bioac-
cumulative substances, including metals, polycyclic
aromatic hydrocarbons (PAHs), PCBs, OC pesti-
cides, pyrethroid pesticides, a variety of semi-volatile
organic chemicals (SVOCs), and polychlorinated
dibenzo
-p-
dioxins and furans (PCDDs and PCDFs)
(International Joint Commission (IJC) 1988; US
Environmental Protection Agency (USEPA) 1997,
2000a). Contaminated sediment has been identifi ed
as a source of ecological impacts throughout North
America. In the Great Lakes basin, for example, sedi-
ment quality issues and concerns are apparent at 42
of the 43 areas of concern (AOCs) that have been
identifi ed by the International Joint Commission (IJC
1988). In British Columbia, such issues and concerns
have been identifi ed in the lower Fraser River basin,
the lower Columbia River basin, and elsewhere in the
province (Mah
et al.
1989; MESL 1997; Macfarlane
1997). Such issues have also emerged in Florida, in
some cases raising concerns about human health
and aquatic-dependent wildlife (MacDonald 2000).
