Environmental Chemistry and Chemical Hazards

Earth's System Science

earth interacting with physical, chemical and biological processes

the 5 spheres

atmosphere, hydrosphere, biosphere, anthrosphere, geosphere

atmosphere

A thin layer of gases surrounding Earth. contains O for human life, CO2 for photosynthesis, N for life molecules. protects life from UV

biosphere

the part of Earth where life exists

geosphere

all of the rock at and below Earth's surface

Anthrosphere

the part of earth made by humans for use in human activities and human habitats such as buildings, roads, farms, mining, etc.

Hydrosphere

All the water at and near the surface of the earth

Two great fluids

surface water and air in the atmosphere

environmental chemistry

discipline that describes the origin, transport, reactions, effects and fates of chemical species in the 5 spheres

pollutant

substance present in greater concentration due to human activity and having a detrimental effect upon its environment/something valuable in the environment

contaminant

substance that causes a deviation of the normal composition of an environment (impurity)

source

of a pollutant is the logical place to eliminate pollution (source can be used to eliminate)

receptor

anything that's affected by pollutant

sink

long term repository (storage) of the pollutant

Carbon Cycle Steps

1. C moves from atmosphere to plants

2. C enters food chain

3. C enters through decomposition

2. C moves from plants to animals

3. C moves from plants and animals to soil

4. C moves from living things to the atmosphere

5. C moves from fossil fuels to the atmosphere when fuels are burned

6. C moves from the atmosphere to the oceans

nitrogen cycle

1. nitrogen fixation (N moves from atmosphere to soil via oxides or fixation)

2. mineralisation (N moves from organic to inorganic matter which plants can use)

3. nitrification (mineralised N is converted to NO2 and NO3)

4. immobilisation

5. denitrification

nitrogen fixation

process of converting nitrogen gas into nitrogen compounds that plants can absorb and use

mineralisation

The conversion of an organic form of an element to an inorganic (mineral) form. removal of carbon

Nitrification

mineralised N is converted to NO2 and NO3

Immobilisation

process where nitrate and ammonium are taken up by soil organisms and become unavailable to crops

Denitrification

process by which bacteria convert nitrates into nitrogen gas

The Geosphere

the solid part of the earth. layered structure. good source of natural capital (oil, gas, Al etc)

the productivity of soil is affected by...

environmental conditions and pollutants

crust

Earth's outermost layer. thin, most of solid earth crust consists of rock

rocks are composed of...

minerals

mineral

naturally occurring inorganic solid with a definite internal crystal structure and chemical composition

rock

solid, cohesive mass of pure mineral

Earth's crust is made of

oxygen (49.5%), silicon (25.7%), aluminium (7.4%), iron (4.7%), calcium (3.6%), sodium (2.8%), Potassium (2.6%), Magnesium (2.1%) and other (1.6%)

types of rock

igneous, sedimentary, metamorphic

igneous rock

a type of rock that forms from the cooling of molten rock at or below the surface

types of sedimentary rocks

detrital (clastic), chemical, organic

sedimentary rock

A type of rock that forms when particles from other rocks or the remains of plants and animals are pressed and cemented together

metamorphic rock

A type of rock that forms from an existing rock that is changed by heat, pressure, or chemical reactions.

Weathering

The chemical and physical processes that break down rock to soil

soil

a variable mixture of minerals, organic matter and water capable of supporting plant life of earths crust

organic matter in soil

plant biomass in various forms of decay. some organic compounds act as ion-exchangers. food for micro-organisms

inorganic material in soil

clay. holds water and is in plant nutrient cation exchange

sand

the largest particles that make up soil

silt

fine grayish-brown powder of fertile soil. 1/20th of a mm.

clay

Smallest soil particle. very fine. formed during weathering and erosion of rock. contain silicate and most Al and H2O.

clays are...

secondary minerals and serve to bind cations Ca2+. Mg2+, K+, Na+, NH4+ to protect them from excessive leaching by rain water

3 major groups of clay minerals:

montmorillonite, illite, kaolinite

soil porosity

a measure of the volume of pores or spaces per volume of soil and the average distances between those spaces. pore spaces allow air and water to move

Leaching

Downward movement of water in soil

Structure of soil

contains air pockets and with increasing depths, layers called horizons

horizons of soil

form as a result of complex interactions among processes that occur during weathering

soil fraction of productive soil:

5% organic, 95% inorganic matter

topsoil

top layer of soil. plant roots permeate it and take nutrients and water from it

Rhizosphere

where plant roots are most active. elevated levels of biomass and composed of plant roots and microorganisms associated with them

Humus

material formed from decaying leaves and other organic matter. final product of decay

Chelate

a substance that can grasp the positive ions of a mineral

chelation in soil

inorganic nutrients that are enclosed by an organic molecule

Soil acts as a...

buffer and resists change in pH because of its ability to take up and release H+ ions

Buffer

weak acid or base that can react with strong acids or bases to help prevent sudden changes in pH

The higher the cation exchange capacity of a soil...

the greater the buffering capacity

Cations

positively charged ions

Anions

negatively charged ions

cation exchange capacity

the ability of a particular soil to absorb and release cations

Macronutrients

The six key elements that organisms need in relatively large amounts: C, H, N, P, Ca, Mg, S

Micronutrients

essential nutrients in soil in smaller amounts: vitamins and minerals

nitrogen fixation bacteria

form nodules on the roots of some plants to provide nitrates from nitrogen gas for the plants

soil fertilisers contain

6%N, 12%P(P2O5), 8%K(K2O) and micro of MG2+ and SO42-

Adsorption in the soil

pesticides and other toxins can be adsorbed to prevent water leaching and spread of pollution

Biodegradation

the disintegration of materials by bacteria, fungi into less toxic products

Photochemical degradation

chemical degradation brought about by exposure to sunlight

degradation by hydrolysis

gives rise to less toxic products that are easily leached

major components in the atmosphere

Nitrogen and Oxygen

minor components in the atmosphere

Argon, CO2 & other noble gases

Trace gases in atmosphere

water vapour, methane, CO, NO, NO2

greenhouse effect

increase in atmospheric temperature due to the retention of solar radiation

Conduction

The direct transfer of heat from one substance to another substance that it is touching. relatively slow

Convection

The transfer of heat by the movement of a fluid.

Radiation

the transfer of energy as electromagnetic waves in infrared region of spectrum. only type of energy that can travel through space

carbonate compensation depth

the water depth at which the rate of supply of calcium carbonate from the surface = the rate of dissolution

dissolution

the breaking up or dissolving of something into parts; disintegration

factors which affect carbonate compensation depth:

water temp, depth, CO2 conc, pH, amount of carbonate sediment supply

carbon monoxide

a toxic flammable gas formed by incomplete combustion of carbon. reduces oxygen-carrying capacity in blood. reacts with gases to produce ozone

carbon dioxide

generated by burning fossil fuels or natural processes

Nitrogen Oxides (NOx)

created by combustion in road transport. nitrous oxide contributes to global warming, nitrogen dioxide - ground level ozone forming reactions and smog

volatile organic compounds (VOCs)

emitted by vegetation. road transport, solvents. contribute to forming ground level ozone and smog

Ozone

shields us from UV radiation. on ground level, pollutant

persistant organic pollutants (POPs)

volatile chemical released from agricultural or industrial. persist in environment. health effects on wildlife & humans

sulfur dioxide

generated by burning fossil fuels for electricity. with water, creates acid rain. contributes to smog

Ammonia

use in agriculture e.g. manure & fertiliser. reacts with other pollutants to produce particulate matter. overenrichs ecosystems with N

particulate matter

the mix of both solid and liquid particles in the air. cause haze and lung problems

heavy metals

release into atmosphere by burning fossil fuels, road transport emissions. can have toxic effect on humans

ozone layer

Protective layer in atmosphere that shields earth from UV radiation. absorbs IR radiation, trapping heat in troposhere

ozone depletion

thinning of Earth's ozone layer caused by CFC's leaking into the air and reacting chemically with the ozone, breaking the ozone molecules apart

acid rain

Rain containing acids that form in the atmosphere when industrial gas emissions (especially sulfur dioxide and nitrogen oxides) combine with water.

Effects of acid rain:

erodes buildings, destructs forests, respiratory effects on animals, toxic to plants

primary pollutants

pollutants that are put directly into the air by human or natural activity. wild fires, agriculture, factories, cars