Environmental Engineering Reference
In-Depth Information
• Geologic environment. The most significant geologic factors include
• Soil composition and other physical characteristics such as permeability,
porosity, moisture content, composition, extent and distribution, thickness,
total organic carbon content, pH, redox potential, dissolved oxygen (if satu-
rated), and other parameters
• Depth to bedrock, type, composition, distribution, fractures, permeability,
porosity of bedrock, and other parameters
• Terrain and topography
• Potential surface and subsurface migration pathways
• Climatic factors
• Release location. Different climates—deserts, mountains, humid areas, or tem-
perate regions can influence the type and rate of degradation
• Surface water features
• Distance to surface water bodies and their type. Immature streams, mature
streams, rivers, lakes, wetlands, and bogs can differ in pH due to the rock
composition of their channels and bottoms and the amount of organic matter
they receive from outside, inputs termed allochthonous
• Weather conditions at the time of the release. Weather conditions are often impor-
tant and sometimes overlooked as potentially significant. Those conditions affect-
ing degradation and migration include
• Temperature
• Humidity
• Precipitation
• Wind speed and direction
• Biologic factors
• The type, distribution, and amount of microorganisms will influence the rate
and can determine if degradation even occurs
• Anthropogenic factors. Anthropogenic factors are often overlooked and frequently
significant. These include
• Physical landscape alteration (i.e., buildings, roads, parking lots, etc.)
• Surface water drainage modifications including stormwater control and wet-
land destruction
• Alteration of native vegetation
• Introduction of invasive vegetation
• Regional contaminant loading, including sources, duration, type, release
points, and physical state of contaminants (i.e., solid, liquid, or gas)
• Developmental history of the area and region
8.3.2.1 Biotic Degradation
Microbes have the ability to oxidize a variety of organic contaminants including many
VOCs, polynuclear aromatic hydrocarbons (PAHs), and other compounds. This capa-
bility arises from their enormous variety, populations, rapid growth, and diversity of
environmental niches. Soluble organic compounds with low molecular weights such as
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