Section A Definitions Flashcards
Contaminant
The presence of a substance where it would not be present naturally and present at above background concentrations.
Pollutant
the accumulation of contaminats which have an adverse effect on biological and/or environmental health.
what are the physical pathways of contaminant transport?
MADT—-> Mass transfer, Advection, Dispersion and Transformation.
Define bioaccumulation
when a pollutant concentrates on the body to a level higher than in the environment. eg; lead and fluoride bioaccumulate in bones.
Define bioconcentration
Bioconcentration is the accumulation of a chemical in or on an organism when the source of chemical is solely water.
For example contaminated fish.
The equation for concentration in fish:
concentration in fish = (conc. in water) x (bioconcentration factor(BCF)).
Define biomagnification
Biomagnification is the process by which a compound (such as a pollutant or pesticide) increases its concentration in the tissues of organisms as it travels up the food chain.
For example, fish accumulate mercury more rapidly than they excrete it, and therefore up the food chain the concentration increases and each fish has moe mercury than the one it ate.
Define emerging contaminants
Emerging contaminants are synthetic or naturally occurring chemicals or any microorganisms that are not commonly monitored in the environment but have the potential to enter the environment and cause known or suspected adverse ecological and/or human health effects.
What are the key pollutant types
Physical, chemical and biological
Define Mass transfer
Mass transfer is the process that transfers contamination mass between phases in response to chemical and concentration gradients.
Define advection and give examples
Advection is the transport of a pollutant via the movement of a fluid. It is a passive process as it is the medium moving (eg. water, air) and it is the fastest/most important of the pollutant pathways.
examples:
- Convection due to density differences in air/water.
- Wind generated mixing across the surface of a lake
- flow in a stream- silt in a river by bulk water flow downstream.
Define dispersion
The spreading of the pollutant around the centre of mass. Due to Molecular Diffusion, which is the movement of a pollutant from an area of high concentration to low.
Due to Non uniform flow – i.e. flow pathways and velocities through the environment are not uniform.
Define transformation
- Wide-ranging – the physicochemical nature of the contaminant is altered.
- Such that the original mass of the contaminant is reduced e.g. radioactive decay or biotransformation and degradation.
Give examples of physical pollutants
radioactivity, light pollution and noise pollution
Give examples of chemical pollutants
metals (arsenic, mercury), inorganic (salinity, nitrates), organic (Organic e.g., pesticides, hydrocarbons, plastics)
Give examples of biological pollutants
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Define point sources
Sources of pollution from a discrete, confined and detectable output- for example pipe, ditch, conduct, etc.
the source is easy to identify.
easy to regulate through discharge consents- eg STWs.
Define diffuse sources
Pollution spread over wide areas with no identifiable source.
diffusion refers to the transport of compounds through the action of random motions. Diffusion works to eliminate sharp discontinuities in concentration and results in smoother, flatter concentration profiles.
Usually involves transport via air-soil-water pathways, so pollution is transformed or dispersed.
Atmospheric discharge, surface run-off from agricultural, residential and urban
areas. Difficult to identify, source, quantify and manage.
Defra (2012): run-off from contaminated land/historic landfills, misconnected
sewers and release from legacy sediment contamination – most significant diffuse pollutants in UK surface waters.
Why is water a good solvent?
Water is a good solvent because it is a polar molecule. The partial charges in the oxygen and hydrogen atoms attract molecules oppositely charged. ir dissolves ions and polar molecules. for example breaks the ionic bonding in salts. Also, fats and oils for eg are not polar and herefore do not dissolve.
what are the mass transfer processes?
sorption, evaporation, volatilisation and dissolution.
check diagram in notes to see thier associations.
Define sorption
Sorption(retention)- association of a chemical to a solid phase eg soil particle.
Any removal of a compound from solution to a solid phase we define as sorption.
absorption, adsorption and precipitation are sorption processes.
what is the equation for flux, when looking at a fuid during advection?
J = CV
J is flux (ML-2T-1), C is chemical concentration (ML-3), V is flow velocity (LT-1)
- i.e. transport rate of contaminant will be proportional to the velocity of the water body.
What is a xenobiotic source of pollution?
Xenobiotic sources are synthetic materials that do not come from natural sources. For example, plastics, microplastics, synthetic organic compounds (DDT, PCBs, organophosphates etc) —> like herbicides, pesticides, and other chemicals that come from agriculture, stormwater runoff etc.
Caesium 137- from nuclear testing in the 1952- found in sediment records around the world; ice cores, peatlands, lakes, marine etc. Also, from the Chernobyl accident,the half life is approx 30 yrs. however, other radionuclides will be present approx 20k years.
what are natural pollution sources?
Metals, hydrocarbons, noise, some radioactivity (e.g. radon gas), nutrients (inorganics)…
Challenge can be to distinguish between natural background levels and elevated levels – need to determine adverse biological affect (Chapman 2007).
Radon gas from uranium decay from rocks can infiltrate homes through the water supply and air.
what is the Water Framework Directive?
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