chapter 6: Water quality managment Flashcards
Primary fate and transport mechanisms for contaminants potentially present include the following:
- Volatilization of chemicals from soil
- Degradation of chemicals in soil and groundwater
- Erosion of particulate-bound chemicals from soil
- Leaching from soil with infiltrating water
- Transport of chemicals with groundwater flow.
Volatilization can significantly affect
the distribution of a chemical in the environment
Volatilization can significantly affect the distribution of a chemical in the environment. In soils, the result is
a decrease in the amount of a chemical in soil
In soils, the result is a decrease in the amount of a chemical in soil as the chemical
volatilizes to soil gas and ultimately discharges to the atmosphere
. In soils, the result is a decrease in the amount of a chemical in soil as the chemical volatilizes to soil gas and ultimately discharges to the atmosphere. Volatilization reactions are most significant in
surface soils that are in direct (or near-direct) contact with the atmosphere.
Numerous chemicals in the environment are subject to
naturally occurring biotic (biologically based) and abiotic (non-biologically based) transformation reactions
Numerous chemicals in the environment are subject to naturally occurring biotic (biologically based) and abiotic (non-biologically based) transformation reactions that result in
the degradation of the chemical
Numerous chemicals in the environment are subject to naturally occurring biotic (biologically based) and abiotic (non-biologically based) transformation reactions that result in the degradation of the chemical. Many organic compounds are subject to
biodegradation reactions
Numerous chemicals in the environment are subject to naturally occurring biotic (biologically based) and abiotic (non-biologically based) transformation reactions that result in the degradation of the chemical. Many organic compounds are subject to biodegradation reactions under
aerobic (in the presence of oxygen) and anaerobic (in the absence of oxygen) conditions
During biodegradation, naturally occurring microorganisms in the ………………….
subsurface
During biodegradation, naturally occurring microorganisms in the subsurface transform
a chemical to another state as a direct or indirect consequence of their metabolic processes
During biodegradation, naturally occurring microorganisms in the subsurface transform a chemical to another state as a direct or indirect consequence of their metabolic processes. Biodegradation reactions often
break down organic chemicals to less toxic forms
Several naturally occurring abiotic reactions can significantly affect
the fate of chemicals in the environment
Several naturally occurring abiotic reactions can significantly affect the fate of chemicals in the environment. Common abiotic reactions include
photodegradation and hydrolysis
Photodegradation is
the process of decomposition of a chemical upon exposure to radiant energy such as the action of light
Photodegradation is the process of decomposition of a chemical upon exposure to radiant energy such as the action of light, and is most significant to chemicals in
surface soil that are in direct contact with sunlight
Hydrolysis is
the degradation reaction of the chemical with components of water
Hydrolysis is the degradation reaction of the chemical with components of water (e.g.,
hydroxyl and hydronium ions)
Hydrolysis is the degradation reaction of the chemical with components of water (e.g., hydroxyl and hydronium ions) and is thus most important in
saturated environments
Erosion processes can substantially affect the
distribution of soil-bound particulates in the environment
Erosion processes can substantially affect the distribution of soil-bound particulates in the environment and thus influence the
distribution of soil contaminants
Erosion processes can substantially affect the distribution of soil-bound particulates in the environment and thus influence the distribution of soil contaminants. High winds can scour
fine particles from the soil surface and redistribute these particles downwind
Similarly, runoff resulting from heavy precipitation events can scour
fine soil particles from surface soils
Similarly, runoff resulting from heavy precipitation events can scour fine soil particles from surface soils, eventually
depositing the particles during sedimentation downstream.
Similarly, runoff resulting from heavy precipitation events can scour fine soil particles from surface soils, eventually depositing the particles during sedimentation downstream.
These physical processes often represent the
primary mechanism for transport of otherwise immobile chemicals such as metals.
Chemicals in soils have the potential to
migrate to greater depths
Chemicals in soils have the potential to migrate to greater depths with
infiltrating water.
Chemicals in soils have the potential to migrate to greater depths with infiltrating water. As rainwater infiltrates, chemicals may be
be leached from the soil and carried to greater depths and potentially to groundwater
Chemicals in soils have the potential to migrate to greater depths with infiltrating water. As rainwater infiltrates, chemicals may be leached from the soil and carried to greater depths and potentially to groundwater. The degree to which a chemical is leached is strongly influenced by
the chemical’s tendency to partition to the solid or aqueous phases
Chemicals in soils have the potential to migrate to greater depths with infiltrating water. As rainwater infiltrates, chemicals may be leached from the soil and carried to greater depths and potentially to groundwater. The degree to which a chemical is leached is strongly influenced by the chemical’s tendency to partition to the solid or aqueous phases, which is largely a function of
the chemical’s solubility and particle affinity.
Water solubility describes
the amount of a chemical that will dissolve in a given quantity of water
Water solubility describes the amount of a chemical that will dissolve in a given quantity of water, and thus is
a primary determinant in the transport of a chemical in the environment
Highly soluble chemicals can often
readily dissolve in water
Highly soluble chemicals can often readily dissolve in water and are thus
susceptible to being mobilized from the soil matrix with infiltrating water and migrate to groundwater
The solubility of organic chemicals is typically a
function of the hydrophobic nature of the chemical
The solubility of organic chemicals is typically a function of the hydrophobic nature of the chemical. Many organic chemicals are
non-polar
The solubility of organic chemicals is typically a function of the hydrophobic nature of the chemical. Many organic chemicals are non-polar and thus
do not dissolve readily into water
Metals, which are naturally occurring, were detected in virtually
all groundwater samples
The relative proportion of metals between the dissolved and particulate phases is controlled by
a complex combination of precipitation and sorption reactions
The relative proportion of metals between the dissolved and particulate phases is controlled by a complex combination of precipitation and sorption reactions. In addition, metals in solution may exist as
“free” ions
The relative proportion of metals between the dissolved and particulate phases is controlled by a complex combination of precipitation and sorption reactions. In addition, metals in solution may exist as “free” ions or with other
dissolved inorganic or organic compounds
The relative proportion of metals between the dissolved and particulate phases is controlled by a complex combination of precipitation and sorption reactions. In addition, metals in solution may exist as “free” ions or with other dissolved inorganic or organic compounds. Water solubility is a primary determinant in the
transport of a chemical in the environment.
Solubility of metals will be controlled by
precipitation and adsorption reactions
Solubility of metals will be controlled by precipitation and adsorption reactions, which are likely to be the most significant factors affecting
metals migration
Metals have a large range in the
migration rates and retardation
Metals have a large range in the migration rates and retardation. The magnitude of these mechanisms on metals migration and retardation will be a function of
solution chemistry
Metals have a large range in the migration rates and retardation. The magnitude of these mechanisms on metals migration and retardation will be a function of solution chemistry, including
pH, oxygen concentration, and the concentrations of other chemicals in groundwater.
Variations in the oxidation conditions in the aquifer can lead to
the precipitation or dissolution of hydrous ferric oxide from the aquifer matrix
Variations in the oxidation conditions in the aquifer can lead to the precipitation or dissolution of hydrous ferric oxide from the aquifer matrix. Generally, dissolved iron will precipitate as
hydrous ferric oxide in the presence of oxygen in the aquifer
Variations in the oxidation conditions in the aquifer can lead to the precipitation or dissolution of hydrous ferric oxide from the aquifer matrix. Generally, dissolved iron will precipitate as hydrous ferric oxide in the presence of oxygen in the aquifer, resulting in
depletion of dissolved metal mass from groundwater
Variations in the oxidation conditions in the aquifer can lead to the precipitation or dissolution of hydrous ferric oxide from the aquifer matrix. Generally, dissolved iron will precipitate as hydrous ferric oxide in the presence of oxygen in the aquifer, resulting in depletion of dissolved metal mass from groundwater as the metal
adsorbs to the oxide surface
Conversely, if reduced conditions are established in the aquifer (e.g., ………………………………………..)
as the result of the release of an organic-rich solution
Conversely, if reduced conditions are established in the aquifer (e.g., as the result of the release of an organic-rich solution), hydrous ferric oxide may be
dissolved and the adsorbed metals will be released to groundwater.
In general, sorption to organic matter and dissolution rates are important factors limiting
the mobility and transport of pesticides in groundwater
In general, ………………………………………………………………… are important factors limiting the mobility and transport of pesticides in groundwater
sorption to organic matter and dissolution rates
In general, sorption to organic matter and dissolution rates are important factors limiting the mobility and transport of pesticides in groundwater. Solubility and volatility tends to be
low for these chemicals
In general, sorption to organic matter and dissolution rates are important factors limiting the mobility and transport of pesticides in groundwater. Solubility and volatility tends to be low for these chemicals, indicating that they are
not readily dissolved in groundwater
In general, sorption to organic matter and dissolution rates are important factors limiting the mobility and transport of pesticides in groundwater. Solubility and volatility tends to be low for these chemicals, indicating that they are not readily dissolved in groundwater. Furthermore, the high retardation factors that characterize these chemicals highlight
the tendency for the migration of these chemicals to be greatly slowed by sorption reactions
Estimated retardation factors indicate the
chemical migration rates for dissolved pesticides are 50 to 3,500 times slower than the rate of groundwater movement
