Halogenated hydrocarbons Flashcards
Give examples of low molecular weight halogenated hydrocarbons?
industrial solvents - vinyl chloride, carbon tetracholride
Give examples of high molecular weight halogenated hydrocarbons?
Agriculture - DDT, DDE, Drins (aldrin, dieldrin), dioxins and furans
Industrial - PCBs (polycholrinated biphenyls)
what increases volatility?
volatility is increased the lower the molecular weight
give 2 examples of persistent organic pollutants (POPs)?
PBTs- persistent bioaccumulative toxics
TOMPs - toxic organic micro pollutants
What increases persistence?
persistent POPs are those with a greater molecular weight and those that bacteria have not yet evolved to degrade e.g PBTs/TOMPs
Give examples of agricultural pollutants?
pesticides - DDT
insecticides - lindranes e.g toxaphene
seed dressings (Drins) - aldrin, dieldrin
soil fumigants - hexachlorobenzene
What can PCBs be used for ?
Industrial - plastics, textiles, electrical equipment and paints
Agriculture - pesticides, insecticides etc
Name 2 point sources from which PCBs may enter the marine environment?
Incinerator plants and Industrial waste (sewage sludge)
Name two PCB pathways to the ocean?
Atmospheric adsorption onto dust particles e.g DDT detected on remote islands.
Fluvial - runoff/irrigation.
What happens on the surface microlayer of the ocean
POPs accumulate on the surface, here they may effect skimming Birds via bioaccumulation. They are relatively insoluble therefore form air bubbles that may be released to the air - transfer of aerosols.
What are the issues associated with storage and bioaccumulation.
Once ingested POP’s are difficult to excreta. they are lipid soluble and are therefore stored in the fat cells of organisms. results in bioconcentration. During periods of starvation fat cells are mobilised as a source of energy, this releases the bio accumulated pollutants into organism.
what may affect their toxicity?
The lipid content of organism.
The phyla of organism e.g bivalves are less sensitive than crustacea
Biomagnification
What are the effects of DDT on birds?
DDT is especially dangerous to falcons bald eagles and ospreys. DDT is biomagnified across trophic level and is found in much greater concentrations in these top predators. DDT reduces the thickness of the birds egg shells. This results in many eggs cracking and being destroyed before chick hatches. Causes a decline in population.
What are the effects of pesticides on populations?
pesticides cause the initial drop of pests, which in turn disrupts the natural interaction between pest/predator. results in predator numbers decreasing. Pests may then develop genetic resistance and numbers quickly rebound, however there is no natural predator to control numbers so continue to increase.
Furthermore these pests may have negative effects on the reproductive capabilities of species such as seals, reducing population.
What are the impacts of POPs on human populations, examples?
Short term exposure - mild cases may cause nausea, whilst sever case may damage CNS and Respiratory system.
Long term exposure - may be linked to Parkinson disease and cancer.
E.g Yusho disease, Japan. caused by PCBs on rice and resulted in respiratory diseases
or Bhopal incident, India. At the union Carbide plant 36 t of methyl isocynate was released. caused the instant death of 2500 and has resulted in respiratory diseases for 50,000+
