Fate bioavailability

Fate of organic contaminants in the environment and in biota depends on

• Chemical properties → persistence, solubility, vapor pressure...

• Transport/transformation: local – global

• Biotic uptake

Two PBTs

PCB polychlorinated biphenyl, PBDE tetrabrominated diphenylether

What structural properties signify PBTs

Aromatic hydrocarbons + Halogens: Cl, F, Br, I

Stabilise the molecule, increase hydrophobicity and persistence

Partitioning thresholds

log kow >3 = bioaccumulationg compounds

log kow >5 = very hydrophobic

log kow >7 super hydrophobic

List from lowest to highest log kow:

• Polychlorinated biphenyls (PCB)

• Polycyclic aromatic hydrocarbons (PAH)

• Organic pesticides

• Halogenated aliphatic hydrocarbons

• Methyl mercury

• PCB 4-10

• PAH 3-7

• Organic pesticides 0-7

• Halogenated aliphatic hydrocarbons 1-3

• Methyl mercury 0.3

What does increasing log kow mean

Decreasing solubility on water, increasing solubility in non-polar substances

Kow

octanol/water

Koc

organic matter/water

Koa

octanol/air

Kaw

air/water

Kow range for persistent polutants

10^4-10^7

Koa range for persistent polutants

10^6-10^12

Kaw range for persistent polutants

10^-1-10^-3

Abiotic chemical transformation

Potolysis - light (UV)

Hydrolosis - water, OH

Dissociation - pH

Oxidation/reduction

Biotic chemical transformation

Microbial

Macrobial

Microbial chemical transformation ex

Aerobic ring clevage

Anareobic dehalogenation

Macrobial chemical transformation ex

p450 monooxygenase system phase I and phase II enzymes

Transport - across phases

The grasshopper effect

Global distrubution of persistent organic pollutants

Sorption def

associations between contaminants and particles

sorption depends on

• Chemical properties of the contaminant

• Quality/chemical properties of organic matter

• Quantity of organic matter

DOM def

Disolved organic matter

POM def

Particulate organic matter

Sorption Relative contaminant concentration: perticle size ration

decreses with particle size. Because surfece:volume ratio is high for small particles. And small particles have high organic content

Effects of bioturbation processes

Particle mixing, Irrigation, Redox conditions

Particle mixing effects (bioturbation)

Affects distrubution of sediment associated contaminants

• Organisms affect contaminant fate, thereby affecting their own exposure

• Contaminant fate and effects are intimately connected

Irrigation effects (biotubation)

Affects distrobution of disolved contaminants (flushing the sediment)

Redox condition effects (bioturbation)

Stimulates aerobic microbial degredation of sediment associated contaminants

PCB concentration in biota – decreased over time Marenzelleria spp

1. Arrived in southern Baltic Sea in mid 80s rapidly spreading invading species

2. Lives in organically enriched oreutrophicated sediments

3. Tolerates low oxygen and high sulphideconditions

4. Burrow depth 35 cm

5. Average bioturbation depth by indigenous fauna is 5 cm

6. Reach densities of 40 000 ind. m -2

7. Bioturbation increases the release of PCBs from sediment to water

Bioconcentation def

Accumulation from water exposure (Cbiota>Cwater)

Bioaccumulation def

Accumulation from differet exposure routes (Cbiota>Cwater/particles)

Biomagnification def

Accumulation through trophic levels (Cbiota3>Cbiota2>Cbiota3)

BCF def

Bioconcentration factor. Net accumulation of a contaminant in an organisim from water at steady state

Bioconcentration of organic contaminant - ex lipid content

Very fat fish concentrate more lipids (water+prey)

Fat fish concentrate more lipids (water)

Lean fish concentratte less lipids (water)

BAF def

BioAccumulation factor. Net accumulation of contaminant in an organisim from all sources, includiing water, food, and sediment at steady state

Good to know about bioaccumulation

Grat variation in bioaccumulation among species exposed to the same sediment.

Routes of uptake (bioaccumulation)

• Respiration (water or air)

• Diffusion over skin

• Food

Routes of depuration (bioaccumulation)

• Respiration (water or air)

• Feaces

• Diffusion over skin

• Metaolic conversion

• Reproduction

• Growth

Life strategy

exposure differs depending on life strategy and feeding

Top predators (biomagnification)

Air-breathers, cannot eliminate contaminants efficently

ower trophic levels (biomagnification)

Extremley efficient at extraction food from sediments. POPs associated with food particles

Marine sediments (biomagnification)

Main source/sink for POPs

How to measure bioavailability

• bioconcentration, bioaccumulation, biotransformatio

• Factros that affect those

• Mimic uptake by use of special samplers

Bioavailability and organic matter

More POC and DOC = less truly dissolved contaminant

→ Bioavailability decreases with increasing POC, DOC

→ Bioacumulatoin depends on particle characteristics

Metal def

Basic substance with a shiny surface that can transfer heat and electricity, often with good tensile strength

Metal uptake in organisms occurs through

• Water, food, air (hg), Me absorbed on fine particles

• Free etal ions through ion- channels, pumps, carriers

• HG, organometals, natural complexes straight over the cell membrane

Assimilation efficency of metals from feed

Co 46%, Zn 41%, cd 17%, ag 7%

Abiotic factors influence metal bioavialability and toxicity

Ph and metals

affects speciation of metals. some are more toxic

DOC and metals

DOC binds free metal ions. UV radiation decreases this capacity by breakdown of DOC

Carbon qualit and metals

Allochontous carbon more effective att lowering toxicity than autochtonous carbon

Humic/fluvic acids and metal

Have phenol and carboxylic groups that can bind metals

Considerations for sampling to assess environmental status

Taking a representative sample:

• sample matrices

• time of sampling

• sampling sites

Getting a correct measurment:

• analytical method

• QA/QC

Accuracy - precicion

Factors that influence analytical quality

• Accuracy

• Repetability

• Reproducability

• Limit of detection