Lect 5 Fate and Bioaccumulation - ENSC

Page 1: Course Introduction

Environmental Compartments: Various ecosystems including:
- Saltmarsh
- Floodplain
- Mangroves
- Intertidal mudflat
- Marine
- Freshwater
- Estuarine
- Subtidal sand and mud
Toxicant Sources:
- Pesticides and heavy metals from:
  - Mining
  - Agriculture
  - Urban land uses
  - Industrial point sources
  - Boating activities (e.g., antifoulants)
Transport Mechanisms:
- Toxicants may be transported:
  - Attached to sediments
  - Dissolved in water.
- Resuspension: Natural or anthropogenic processes can make toxicants available again.
Effects on Biota:
- Pesticide settlement affects photosynthesis and plant health in various habitats.

Environmental Compartments: Toxicants can transfer between air, soil, water, and sediment over time.
Individual Behaviors: Molecules can behave differently in mixtures.
Transformations: Chemical and biological changes occur during transfer.

Lifetime: Average duration of a toxicant in a compartment (Residency Time).
Persistence: Tendency of toxicants to remain in a compartment.
- Longer lifetime equates to higher persistence.
Persistent Organic Pollutants (POPs): Organic toxicants with a lifetime greater than one year.

Importance of Persistence: The persistence of a toxicant directly influences its travel distance in the environment.

Definition: The accumulation of toxicants in the biological organism compartment over time.
Food Web Influence: Bioaccumulation correlates with persistent levels in organism tissues.
Chemical Properties: Dependence on the chemical properties of the toxicant.
Components of Bioaccumulation:
- Bioconcentration: Partitioning of toxicants into organisms.
- Biomagnification: Concentration increase through the food web.

Bioconcentration: Refers to partitioning of toxicants into biological organisms.
- Equilibrium between water and organisms.
Hydrophobicity: The relationship of toxicant's partitioning to its hydrophobic nature.
Partition Coefficient (Kow): Models bioconcentration using a chemical partition constant.

Data on DDT:
- Water concentration: 0.003 ppm
- Octanol concentration: 24,000 ppm
- Kow calculation: Kow = 24,000/0.003 = 8.0 x 10^6
Logarithmic Scale: Log Kow = 6.9 indicates lipophilicity.

Polycyclic Aromatic Hydrocarbons (PAHs): Variations in toxicant properties:
- Log KOW, solubility, vapor pressure, half-life, and sorption coefficients listed for 16 PAHs.

Measurement: BCF measured in laboratory settings:
- Single toxicant exposure in controlled conditions.
Importance: Relates to hydrophobicity (Kow) and concentration in tissues versus water.

Experiment Methodology: Fish placed in contaminated water (gill exposure only).
- No food, levels measured at steady-state to establish BCF.

Graph Relation: Log BCF shows strong correlation with log Kow across toxicant series:
- Higher log Kow often correlates with higher BCF.

Complex Realities: Laboratory conditions differ from natural water phases
- Presence of dissolved organic carbon and particulates complicates measurements.
Key Reminders: Bioaccumulation incorporates both bioconcentration and biomagnification effects.

Definition: Concentration increases in predators through consumption of contaminated prey.
- Assumes nearly all contaminants from prey are retained by predators.
Example Calculation: A 1 kg fish consumes smaller fish and accumulates significant DDT over time.

BCF: Laboratory experiment considering direct water exposure.
BAF: Includes all uptake routes, emphasizing comprehensive accumulation processes.

Historical Context: Use of DDD at Clear Lake, California to control pests, leading to significant ecological impact.
- Notable deaths in Western Grebe, the need for investigation arose after continued usage.

Analysis Findings: High levels of DDD in fish and grebe tissue noted after pesticide application, highlighting historical bioaccumulation issues.

Trophic Effects: DDT concentration increases noted with higher trophic levels in the food chain, especially for humans through dietary intake.

PCBs: Persistent, hydrophobic compounds; water and sediment persistence studied, highlighting extended biological effects in Great Lakes.

Understanding Relationships: Bioaccumulation and chemical properties are crucial for risk assessments of new contaminants.
Persistence vs. Toxicity: Greater persistence may lead to unexpected toxicity in low concentrations, even when inherent toxicity is low.