Week 8- Biosphere Pollution Flashcards by Rebecca Payne

Types of pesticide

*Herbicide
*Insecticide
*Fungicide
* Bactericide

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Desirable characteristics of pesticides:

*usable in small quantities
* low toxcicity to non target species
* Non persistent
* degrades to benign products
* Doesn’t run off with water
* Pests are slow to develop resistance

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How does DDT work?

Opens Na ion channels in neurons causing them to fire spontaneously and disorganises the nervous system of insects

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Impact of DDT on the wider environment

Penetrated coastal ecosystems through indiscriminate spraying onto water surfaces –> fish –> birds–> thins bird shells

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Impacts of chlorinated organic compounds on the environment?

Generally detrimental

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Properties of DDT

Very water insoluble in water but very soluble in lipids/fats- lipophilic

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Method of detection for DDT,DDE,DDD (Liquid-Liquid Extraction)

LLE using a solvent
NaCl added to create a saturated solution- aids transfer of DDT and metabolites into environment
Organic phase= separated by passing through a filter coated with anhydrous sodium sulphate
Organic phase= dried down and redissolved in n hexane
Gas chromotography -> separates compounds based on their volatility

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What is bioconcentration?

Higher concentration of a chemical in an organism than in an environmental medium to which it is exposed

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What is bioaccumulation?

Uptake of a chemical by an organism , following consumption of a food source

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What is biomagnification?

Sequence of processes by which higher concentrations of a chemical are reached in organisms higher up the food chain

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Half life of DDT in water

10 years

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Two main classes of insecticides that are widely used globally

Organophosphates and pyrethroids

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2 main types of organophosphate

Parathion and Malathion

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What is the toxicity of parathion?

Highly toxic to non-target organisms including humans.
-> Inhibit cholinesterase which disrupts the nervous system
-> Absorbed through skin/mucous membrane
-> rapidly metabolised- paraxon

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Toxicity of malathion?

Low toxicity

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Why is accumulation in living organisms important

Toxicity
Chemical burdens reduce fitness and resilience
Food chain impacts
Endocrine disruption

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What are pyrethroids?

Naturally occurring with insecticide properties- can act as a nerve agent and penetrate the exoskeleton of insects

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What is pyrethroid used in conjunction with?

Piperonyl butoxide (PBO) - prevents enzymes in insects body from removing pyrethroids to max out lethal effect

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Toxicity of pyrethroids

Harmless in humans but toxic to beneficial insects e.g. bees, dragonfiles

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Conventional methods of pytheroid pesticide monitoring?

GC-ECD/MS
UV visible spectroscopy
FTIR spectroscopy

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Biosensors for pytheroid pesticide monitoring?

Whole cell biosensor
Antibodies/Immunoassay based biosensor
Enzymatic biosensor
Molecularly imprinted polymer based biosensor

Risks associated with Emerging Organic Pollutants (EOPS)

*Endocrine disruption potential
* Bioaccumulative and persistent
* Carcinogenic properties

Impact of EOPs on endocrine system?

Blocks effects of hormones
Mimics natural hormones leading to over/under production
Hormones released at inappropriate times
Stimulates/inhibits endocrine system

What two compounds to ibuprofen consist of?

50% R
50% S- anti inflammatory properties

Excretion of ipubrofen:

Largely excreted as parent compound or in the form of metabolites

How does the human body convert the compounds within ibuprofen

Human body converts the inactive R form to the active S form

How does ibuprofen behave in aquatic environments?

High mobility- in high concentrations can impact the reproducibility of fish

Ibuprofen and waste treatment plants

Influent waste- contains active drug/metabolites In treatment/natural waters the active form degrades faster

Toxicity of triclosan

- Highly toxic to algae- detrimental to algal communities and the balance of the ecosystem - Acute toxicity on humans e.g. contact dermatitis but may also affect endocrine system

Half life of triclosan?

≤ 2000 days

How does triclosan act?

Triclosan binds to the ENR enzyme and makes it interact more strongly with NAD

Wastewater treatment and triclosan

Wastewater plants don't remove triclosan - it only ionises (becomes biodegradable at pH >8

Policies against triclosan

* US FDA- banned triclosan in 2016 * ECHA and EU - acknowledged triclosan as a pollutant in 2016

Uses of PFOS

Key ingredient in fabric protector and fire fighting foams

Health effects of PFOS

PFOS= persistent and bioaccumulative - Affects immune system of mice at concs of >90ugL-1 - Studies on animals showed PFOS caused endocrine disruption, neonatal mortality etc. - In humans may Icrease risk of pre-eclampsia, increased cholesterol, altered thyroid risk and risk of ADHD

Examples of environmental impact of PFOS

- Buncefield Depot fire 2005 = contamination of river and groundwater but not drinking water - Jersey airport fire-1991 = some properties supplies w water from boreholes = elevated concs of PFOS 7 years later confirming persistance

The Stockholm Convention-2009

Band production and limits use of PFOS

Organic pollutants - behaviour and fate- Ionisation

Some chemicals can exist in 2 forms : neutral and ionised Acidic conditions favour neutral form Alkaline conditions favour ionised

What form of chemical is most table ionically?

Non ionic

Organic pollutants - behaviour and fate- Solubility

High- >100 mg/L Medium- 10-100mg/L Low- <10mg/L

Organic pollutants - behaviour and fate- Octanol water partitioning

Kow=conc in cotanol/conc in water

Octanol vs water

Octanol= non polar - density =0.824 gcm-3 Water= polar- density =1gcm-3

How can we use LogKow to determine properties of organic pollutants?

LogKow < 3 : Organic chemical remains in water LogKow >3 : Organic chemical partitions into soil e.g. DDT

What is vapour pressure?

Tendency of a pollutant chemical to vaporise - higher VP= higher potential to go into atmosphere

How can we use vapour pressure to determine organic pollutant properties?

If < 1 : Non volatile If >1 : Volatile

What can be used if there is no vapour pressure?

Henry's law constant Kh= Partial pressure in atmosphere/conc in water Kh= p organic chemical/[organic chemical]

How can we use Henry's Law constant to determine organic pollutant properties?

If KH< 100 Pam3mol-1 : Non volatile If >100 Pam3mol-1 : Volatile

Organic pollutants - behaviour and fate- Bioconcentration factor

BCF= conc. in living organism/conc. in water

How can we use Bioconcentration factor determine organic pollutant properties?

If : - BCF< 100 = low tendency to bioconcentrate - 100 < BCF < low 1000s= medium tendency to bioconcentrate - BCF >5000 = higher tendence to bioconcentrate

3 main degradation times

- Photolysis - Hydrolysis - Biodegradation

DT50 - degradation time 50% in different mediums?

Water > 2 months Soil > 6 months Sediment > 6 months

Properties influencing environmental behaviour and fate of organic pollutants

* Ionisation * Solubility * Octanol water partitioning * Vapour Pressure * Degradation times * Bioconcentration factor (BCF)