2.2 Environmental partitioning and distribution of pollutants

Environmental pollutants move and accumulate in complex ways. This section explores how chemicals distribute between air, water, and soil, and how they build up in living things. Understanding these processes is key to predicting a pollutant's impact.

We'll look at sorption, partition coefficients, and Henry's law to see how pollutants spread in the environment. Then we'll dive into bioaccumulation and biomagnification to grasp how chemicals concentrate in food chains, affecting ecosystems and human health.

Partitioning Processes

Sorption Mechanisms

Top images from around the web for Sorption Mechanisms

• 

  Frontiers | The Role of Soil Microorganisms in Plant Mineral Nutrition—Current Knowledge and ... View original

  Is this image relevant?

• 

  Frontiers | Role of fungi in bioremediation of emerging pollutants View original

  Is this image relevant?

• 

  Summary on Adsorption and Photocatalysis for Pollutant Remediation: Mini Review View original

  Is this image relevant?

• 

  Frontiers | The Role of Soil Microorganisms in Plant Mineral Nutrition—Current Knowledge and ... View original

  Is this image relevant?

• 

  Frontiers | Role of fungi in bioremediation of emerging pollutants View original

  Is this image relevant?

1 of 3

Top images from around the web for Sorption Mechanisms

• 

  Frontiers | The Role of Soil Microorganisms in Plant Mineral Nutrition—Current Knowledge and ... View original

  Is this image relevant?

• 

  Frontiers | Role of fungi in bioremediation of emerging pollutants View original

  Is this image relevant?

• 

  Summary on Adsorption and Photocatalysis for Pollutant Remediation: Mini Review View original

  Is this image relevant?

• 

  Frontiers | The Role of Soil Microorganisms in Plant Mineral Nutrition—Current Knowledge and ... View original

  Is this image relevant?

• 

  Frontiers | Role of fungi in bioremediation of emerging pollutants View original

  Is this image relevant?

1 of 3

• Sorption describes the process by which a chemical substance becomes attached to a solid surface
• Adsorption occurs when a chemical adheres to the surface of a solid material (soil particles, sediments)
  • Involves interactions between the chemical and the surface, such as van der Waals forces, hydrogen bonding, or electrostatic interactions
  • Adsorption can be reversible or irreversible depending on the strength of the interactions
• Absorption involves the penetration of a chemical into the interior of a solid material (uptake by plants, diffusion into microplastics)
  • Absorbed chemicals are incorporated into the internal structure of the solid
  • Absorption is often a slower process compared to adsorption

Partition Coefficients

• Soil-water partition coefficient ($K_d$) describes the distribution of a chemical between soil and water phases at equilibrium
  • Represents the ratio of the concentration of a chemical in soil to its concentration in water
  • Higher $K_d$ values indicate a greater affinity of the chemical for soil, leading to reduced mobility and bioavailability
  • Depends on soil properties (organic matter content, clay content) and chemical properties (hydrophobicity, polarity)
• Air-water partition coefficient ($K_{AW}$) describes the distribution of a chemical between air and water phases at equilibrium
  • Represents the ratio of the concentration of a chemical in air to its concentration in water
  • Higher $K_{AW}$ values indicate a greater tendency for the chemical to partition into the air phase
  • Influenced by the chemical's vapor pressure and water solubility

Environmental Distribution

Henry's Law Constant

• Henry's law constant ($H$) describes the partitioning of a chemical between air and water at equilibrium
  • Represents the ratio of a chemical's partial pressure in air to its concentration in water
  • Higher $H$ values indicate a greater tendency for the chemical to volatilize from water to air
  • Temperature-dependent, with higher temperatures favoring volatilization
  • Important for predicting the fate and transport of chemicals in the environment (pesticides, industrial solvents)

Fugacity

• Fugacity is a measure of a chemical's escaping tendency from a particular phase or compartment
  • Expressed in units of pressure (pascals) and represents the partial pressure of a chemical in a mixture
  • Chemicals move from high fugacity to low fugacity compartments to achieve equilibrium
  • Fugacity models are used to predict the distribution of chemicals in the environment (air, water, soil, sediment)
  • Considers the chemical's properties, environmental conditions, and transfer processes between compartments

Biological Accumulation

Bioaccumulation

• Bioaccumulation refers to the uptake and accumulation of a chemical in an organism's tissues over time
  • Occurs when the rate of uptake exceeds the rate of elimination or metabolism
  • Can occur through various routes (ingestion, inhalation, dermal absorption)
  • Bioaccumulation factor (BAF) quantifies the extent of accumulation relative to the chemical's concentration in the environment
  • Lipophilic and persistent chemicals (PCBs, DDT) are more likely to bioaccumulate in organisms

Biomagnification

• Biomagnification describes the increasing concentration of a chemical in organisms at successively higher trophic levels in a food chain
  • Occurs when a chemical is transferred from prey to predator, resulting in higher concentrations at each trophic level
  • Biomagnification potential depends on the chemical's persistence, bioaccumulation potential, and trophic transfer efficiency
  • Can lead to high concentrations of chemicals in top predators (mercury in fish, PCBs in marine mammals)
  • Has implications for ecosystem health and human exposure through consumption of contaminated organisms