Contaminants entering an aquatic system via a spill are often associated accidents occurring
during transportation of the chemical, inadvertent spills associated with agricultural and industrial
operations, or improper disposal. Known incidents of chemical spills can be monitored for movement
within and impacts to the aquatic system. If the spilled chemical is hydrophobic, it will often remain
relatively unmixed with the aquatic system allowing easier tracking and cleanup.
Spillage or leakage of gasoline (and additives) associated with boats and refueling stations is
also a source of contaminants to the water and sediment. Yagecic and Moy (1995) have demonstrated
that lead concentrations in sediments are greater near refueling points. CONTAMINANT DETECTION
The detection of contaminants in an aquatic system is usually through one of three ways, 1)
direct observation such as in oil spills, 2) indirect evidence such as a fish kill, an unusually large number
of physical deformities in biota, or a high incidence of illness in the local population, or 3) chemical
analyses ranging from screening levels to extensive surveys. The latter of these methods are often the
result of one of the first two since, typically, the analytical costs for the analysis of most of these
methods are often quite high. In addition to sample collection for analysis, in situ techniques such as
fluorescence (Cremeans et al. 1995) and remote sensing techniques such as aerial/satellite detection
methods may be used to monitor the transport of spills. CONTAMINANT MANAGEMENT AND REMEDIATION
Often techniques used to manage for water quality problems associated with eutrophication are
applicable to management of contaminants discussed in this section. For example, heavy metals
mobilized by low or undetectable concentrations of dissolved oxygen may be successfully managed
with aeration devices. Methods, such as chemical additions to alter pH may be applicable for
decreasing contaminant mobility. A "no action" alternative which allows contaminated sediments to be
buried with time (for sediments subjected to minimal disturbances or redistribution, e.g., sediments in
accumulation zones (Figure 2.1.3)) may be feasible. This method works for contaminants that remain
bound to the sediments. Other alternatives may involve operational techniques, such as manipulation of
residence time and dilution, and specific clean up methods used for spills. For contaminants in aquatic
sediments that are primarily cycled via biotic mechanisms, separation of the contaminated sediments
from the biota using capping, removal (dredging), or isolation (dikes, etc.), is a possible means of


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