Section A Definitions

Question 1

Contaminant

Answer 1

The presence of a substance where it would not be present naturally and present at above background concentrations.

Question 2

Pollutant

Answer 2

the accumulation of contaminats which have an adverse effect on biological and/or environmental health.

Question 3

what are the physical pathways of contaminant transport?

Answer 3

MADT—-> Mass transfer, Advection, Dispersion and Transformation.

Question 4

Define bioaccumulation

Answer 4

when a pollutant concentrates on the body to a level higher than in the environment. eg; lead and fluoride bioaccumulate in bones.

Question 5

Define bioconcentration

Answer 5

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)).

Question 6

Define biomagnification

Answer 6

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.

Question 7

Define emerging contaminants

Answer 7

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.

Question 8

What are the key pollutant types

Answer 8

Physical, chemical and biological

Question 9

Define Mass transfer

Answer 9

Mass transfer is the process that transfers contamination mass between phases in response to chemical and concentration gradients.

Question 10

Define advection and give examples

Answer 10

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.

Question 11

Define dispersion

Answer 11

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.

Question 12

Define transformation

Answer 12

• 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.

Question 13

Give examples of physical pollutants

Answer 13

radioactivity, light pollution and noise pollution

Question 14

Give examples of chemical pollutants

Answer 14

metals (arsenic, mercury), inorganic (salinity, nitrates), organic (Organic e.g., pesticides, hydrocarbons, plastics)

Question 15

Give examples of biological pollutants

Answer 15

r

Question 16

Define point sources

Answer 16

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.

Question 17

Define diffuse sources

Answer 17

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.

Question 18

Why is water a good solvent?

Answer 18

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.

Question 19

what are the mass transfer processes?

Answer 19

sorption, evaporation, volatilisation and dissolution.

check diagram in notes to see thier associations.

Question 20

Define sorption

Answer 20

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.

Question 21

what is the equation for flux, when looking at a fuid during advection?

Answer 21

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.

Question 22

What is a xenobiotic source of pollution?

Answer 22

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.

Question 23

what are natural pollution sources?

Answer 23

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.

Question 24

what is the Water Framework Directive?

Answer 24

a

Question 25

what and how do soil properties affect pollutants

Answer 25

• Clay minerals and organic matter are negatively charged and can sorb pollutants depending on their cation exchange capacity. Small, with large surface areas.
• Soil pH affects the solubility of chemicals in soil. Generally, acid pH (high concentration of H+) solubilises chemicals by promoting ionization.

Question 26

What is Organic matter content and how does it affect the transport of pollutants?

Answer 26

e

Question 27

what is bioavailability?

Answer 27

How available the contaminant is to be transported.

• Bioavailability describes many complex processes, including the mass transfer and uptake of contaminants into organisms, which are determined by substance properties, compartment properties, the biology of organisms, and climatic influences.

How available the contaminant is to be mass transported.

bioavailability as the fraction of chemical that is available or can be made available for uptake and, as a consequence, for potentially causing effects in organisms. Bioavailability is dependent on many abiotic and biotic factors, like soil characteristics, route of exposure, and the physiological attributes of the exposed organisms. As a consequence, bioavailability differs among organisms

Question 28

explain the role of microorganisms in soil and water

Answer 28

Highly variable depending on the environmental compartment - particularly light and oxygen availability, but also pH and nutrient availability.
• Critical to degrade and cycle organic matter and nutrients, and potentially control the transport and fate of pollutants.
• Occupythelowesttrophiclevels.
• Autotrophs–energycomesfrom
inorganic sources (e.g., C from CO2)
• Heterotrophs – energy comes from inorganic and organic sources (e.g., C from organic matter).

Question 29

Define biodegradation

Answer 29

• Biodegradationisthebreakdownof organic material by micro-organisms (through heterotrophic micro- organisms).
• In order to thrive and reproduce micro-organisms need an energy source (food).
• Biodegradation can consist of multiple steps – complete degradation converts a carbon source to carbon dioxide and water

Biodegradation of organic pollutants:
Simple carbohydrates – glucose.
• Organic matter from leaf litter,
plant debris – humic substances.
• Organic pollutants which contain C
as part of their molecular
structure.
• E.g. herbicides, hydrocarbons,
solvents.

Question 30

What do the rates of biodegradation depend on?

Answer 30

Nature of soil and water:

• presence or absence of oxygen
• microbial density and organic matter abundance
• nitrogen availability- accelerate biodegradation by adding N
• solubility enhances bioavailability and hence utilisation by microbes
• adding surfactants increases the rate

Question 31

What are POPs?

Answer 31

Persistent organic pollutants