Properties of pollutants and what impacts their dispersal
properties of pollutants
state of matter - can impact how far it is dispersed and its ability to be dispersed
energy form - type of energy the pollution is e.g heat or noise
density - denser materials require more kinetic energy to keep suspended
persistence - the length of time a pollutant remains in the atmosphere before degrading
toxicity - how poisonous a substance is to living organisms - damage to proteins
e.g CFCs have a high persistence and pyrethroids have low persistance
properties of pollutants cont.
specificity - variations in toxicity to different groups of organisms
reactivity - the likelihood to undergo a chemical reaction e.g Nox and ozone are reactive
adsorption - attachment to surface of materials which immobilises them e.g lake sediment disturbance releases phosphates and PCBs
solubility in lipids/water - affects whether a pollutant bioaccumulates/biomagnifies
bioaccumulation of mercury in small fish and biomagnification of pollutants like DDT and PCBs
synergism - pollutants acting together to have different, more serious effects
mutagenic action e.g gonadic is to egg,sperm or embryo, somatic is to a body cell and carcinogenic are cancer causing mutations
teratogenic action - causing birth abnormalities by NOT changing or altering the structure of DNA
mobility - ability of pollutant to move in the environment - more mobile means they travel greater distances like CFCs
primary pollutant - released directly from human activities e.g CO2, CH4 and NOx
secondary pollutant - pollutant produced from chemical reactions with more than one primary pollutant and right conditions acquired
e.g NOx, tropospheric ozone and UV light produce photochemical smog
Impact of environment on pollution
direct effects
the pollutant itself harms the organism
DDT kills insects and thins egg shells
lead is a neurotoxin
indirect affects
pollutant modifies other features of the environment to reduce survival
CO2 acts like greenhouse gas
CFCs release chlorine
Nitrates contribute greatly to eutrophication
Factors affecting degradation of a pollutant
temperature - chemical reactions occur more rapidly at higher temperatures
increased rate of degradation of sewage by bacteria can lead to an increased rate of deoxygenation
light - can provide the energy to drive the chemical reactions of pollutants
can lead to production of secondary pollutants e.g photochemical smog and photodegradation of pesticides
oxygen - presence of oxygen can lead to aerobic decomposition of sewage by bacteria
can lead to production of pollutants such as the oxidation of sulphide ores to produce sulphur dioxide
pollutant interaction - presence of one pollutant can impact behaviour of another
e.g NOx interacting with hydrocarbons to produce the secondary pollutant, photochemical smog
Factors impacting dispersal of pollutants
PH - affects solubility of substances
many heavy metals like lead become more soluble in low ph, more acidic conditions
wind and water currents - impacts direction and pathway of pollutant
adsorbent materials - pollutants and toxic metal ions may adsorb onto materials like clay
Caesium 137 adsorbed onto clat during the Chernobyl nuclear accident
temperature inversions - normally effluent gases have a lower density than the surrounding air so rise to disperse
during a temperature inversion the layer above the air is warmer causing gases below to cool and become more dense and so don't disperse as widely
factors leading to temperature inversions
valleys where colder, denser air collect
fog has a high albedo so reflects sunlight therefore warming upper atmospheric layers
cloduless skies means IR radiated from the ground to cool
low wind velocity so layers of different temps don't mix
Sources, Pathways and sinks
e.g pesticides/fertilisers and liquid manure - source is agriculture, pathway is run-off, leaching, biomagnification/accumulation and sink is water and biota
e.g solids, mining leachate, heavy metals and radiation - source is mining, pathways are spoil heaps, spills, accidents and leaching and sinks are water, soil and biota