Pollution (AS) (Complete) Flashcards
What is pollution and what is it usually caused by?
-Release of substances/forms of energy into environment that cause harm, especially to living organisms
-Usually caused by human activities, but natural processes can have same effects; eg oil leaks from natural oilfields, smoke from forest fires, volcano eruptions releasing acidic gases & dust
What do the properties of pollutants determine?
-Length of time it may cause a problem
-Level of harm it can cause
-Where, how far it may travel
Properties of pollutants; how does the state of matter affect a pollutant?
-Whether a polluting material= solid, liquid or gas affects its ability to be dispersed by moving water/air
-In general, solids are deposited close to source while gases are transported easily in atmosphere
Properties of pollutants; how does energy form affect a pollutant?
The different pollutants that are energy forms like noise, heat, ionising radiation or light have widely varying impacts due to way energy behaves
Properties of pollutants; how does density affect a pollutant?
-Density of material will affect its dispersal
-Denser materials need more kinetic energy to keep them suspended, so are more likely to be deposited closer to source, eg lead dust has ↑ density
-Some gases= denser than air, settle close to ground if there’s insufficient wind to disperse them, eg hydrogen cyanide released at Bhopal, India 1984 remained very close to source
Properties of pollutants; what is persistence, how is it measured + why is this not precise?
-Measure of length of time pollutant remains in environment before breaking down chemically (degrading)
-Can be measured as time it takes for 1/2 of pollutant to break down= environmental half-life. It’s not a precise measure as rate of breakdown can be affected by environmental conditions Ike light, temp, O2 levels, pH, presence of bacteria
Properties of pollutants; what are examples of pollutants with high & low persistences?
-High= CFCs, organochlorine insecticides like DDT
-Low= sewage, pyrethroid insecticides
Properties of pollutants; what is the process of pollutant breakdown and how is it categorised?
-Degradation
-Categorised according to feature causing breakdown;
-Biodegradation: caused by living organisms, usually bacteria
-Photodegradation: caused by light
-Thermal degradation: caused by heat
Properties of pollutants; what is toxicity and how is harm usually caused?
-Measure of how poisonous a substance to living organisms
-Harm usually caused by damage to proteins, especially inhibition of enzyme action
Properties of pollutants; what are examples of toxic pollutants and their actions?
-Carbon monoxide; prevents blood from carrying oxygen by binding to haemoglobin in red blood cells
-Lead; inhibits enzyme action in nerve cells
-Acids; inhibit protein action by changing molecular shape, eg active site of enzyme
-Cyanide; inhibits enzymes involved in aerobic respiration
Properties of pollutants; why is specificity used for and how does it affect pollutants? + eg
-Used to describe variations in toxicity to different groups of organisms
-Specific toxins= more toxic to some groups than others
-Non-specific pollutants= similar toxicities to all groups
-Pyrethroid insecticides have ↑ toxicity to insects &↓ toxicity to mammals so is relatively safe for humans to use in pest control in areas of livestock, but have ↑toxicity in fish so shouldn’t be used near rivers or fish farms
Properties of pollutants; how does reactivity affect pollutants?
-Can affect severity of pollution caused, either↑or ↓ problems caused
-Reactive pollutant may degrade rapidly like sewage, or may react w/ other substances to produce secondary pollutants, eg action of ozone in acid rain & photochemical smog
Properties of pollutants; what are primary and secondary pollutants?
Primary - released by human activities
Secondary - produced by chemical reactions between one or more primary pollutants, often w/ non-pollutants
Properties of pollutants; what is adsorption and how does this affect the pollutant?
-Some pollutants can become attached to surface of materials, eg soil particles/aquatic sediments
-This can immobilize them so can’t cause pollution problems but it’s also possible they may be released later to cause problems after period of time when their presence isn’t obvious, eg disturbance of lake sediments by storms releasing phosphates/PCBs
Properties of pollutants; how does solubility in lipids/water affect pollutants?
-Substances w/ ↑ solubility in water= easily dispersed in water bodies, eg nitrates. Can ↓ pollutant conc but may allow pollutant to affect larger area
-Lipids= organic compounds, fatty acids/derivatives and are insoluble in water. Substances dissolving in lipids may be able to pass through phospholipid cell membranes & be stored in oil/fat deposits within cells, eg mercury/DDT
Properties of pollutants; what is bioaccumulation and what does this involve?
-Process by which # of substance within organism ↑
-Often involves long-term ingestion of small doses of liposoluble pollutant
-OG doses may’ve been too small to be toxic, but may eventually build up to reach toxic levels
-Liposoluble pollutants= more likely to bio-accumulate as may be stored in lipids
-Water-soluble pollutants tend to be excreted from body more easily
Properties of pollutants; what is biomagnification and what does it involve?
-Substances bioaccumulating may become more conc as they pass along food chains, becoming concentrated into progressively ↓ biomass w/ each successive tropic level
-Organisms in later trophic levels often have longer lifespans & build up even ↑ conc, esp if they’re endotherms (warm-blooded) that have ↑ food intake bc of their ↑ metabolic rates so are likely to ingest more of pollutant
Properties of pollutants; what is synergism and what does it involve?
-Involves 2+ pollutants where their effects interact to create diff effect, usually more serious one
-Pollutants themselves don’t interact to produce new pollutant (would be secondary pollutant), it’s their effects that interact, eg ozone damages leaf cuticles & enables sulfur dioxide to cause more damage to newly exposed living cells
Properties of pollutants; what is mutagenic action?
Mutagens= agents causing changes in chemical structure of DNA by damaging chromosomes by rearrangement of DNA structure. Changes are known as mutations
Properties of pollutants; mutagenic action- what are gonadic and somatic effects?
-Gonadic effects (cells in ovaries/testes); mutation in egg/sperm cell/embryo may cause birth abnormality in offspring produced
-Somatic effects (general body cells); mutation in body cell may make it behave abnormally as damaged DNA can’t control normal cell function. Death of individual cells—> rarely issue as can be replaced by division of other healthy cells. Serious consequences of these are if not killed= cancer
Properties of pollutants; mutagenic action- what are examples of mutagenic pollutants?
-Ionizing radiation
-UV light
-Chlorinated organic substances, eg PCBs, dioxins
-Cadmium
-Asbestos
Properties of pollutants; mutagenic action- what is carcinogenic and teratogenic action?
-Carcinogens; mutations causing cancer. Cell multiplication due to a carcinogen produces mass of tissue (tumour). This may eventually cause health issues by preventing normal tissue function
-Teratogens; cause birth abnormalities by preventing normal gene expression. They don’t change DNA structure but inhibit function of proteins & enzymes that DNA would’ve normally controlled. The abnormality can’t be inherited by future generations bc DNA structure isn’t affected. Examples= mercury, herbicide 2,4,5-T
Properties of pollutants; what is mobility and how does it affect a pollutant?
-Ability of pollutant to move in environment depends upon other properties, esp state of matter, density & solubility in water
-More mobile pollutants= likely to travel greater distances & affect larger areas, although dilution may ↓ severity of effect
Properties of pollutants; what are examples of pollutants with different degrees of mobility?
-Lead dust; ↑ density of atmospheric lead dust causes most particles to be deposited close to source
-Smoke particles; easily washed out of atmosphere by rain/settle if air is relatively static. Smaller particles settle more slowly
-Sulfur dioxide gas; is soluble in water & easily removed from atmosphere by rain, usually within 250km of source
-CFCs; chemically stable & ↓ solubility in water, so remain in atmosphere for long time & disperse throughout whole atmosphere