unit 4 ess

Water pollution

The contamination of streams, rivers, lakes, oceans, or groundwater with substances produced through human activities.

Water quality

The degree of purity of water, determined by measuring substances in the water, such as phosphate and nitrate.

Direct measures of water pollution

Measuring the levels of:

• Phosphate

• nitrates

• salt

• ammonia

Biochemical oxygen demand (BOD)

Amount of oxygen required by aerobic organisms to decompose a given load of organic waste; a measure of water pollution.

Indirect measures of water pollution

• Species present/absent

• PH

• DO

Indicator species

Their presence can be indicative of the level of pollusion. E.g. if salmo and mayfly are present the water quality is good and can be used for domestic supply.

Trent Biotic Index

A measurement of levels of pollution in aquatic ecosystems, based on indicator species which tend to disappear from a river as the level of pollution increases.

Eutrophication

Excessive richness of nutrients in a water body which causes a dense growth of plant life and death of animal life from lack of oxygen. Can be both anthropogenic from fertilizers and natural from decaying matter.

Negative effects of eutrophication

• Other species than algae in the eutrophic water body may die out due to lack of sunlight.

• The water becomes undrinkable and species dependent on the water might get sick or even die. There are studies done that show a correlation between drinking eutrophic water and getting stomach cancer for humans.

• Farmers can get economic losses due to being forced to stop using the fertilizers that created the eutrophication.

Management strategies for eutrophication

• Reducing the human activities that produce pollutants, e.g. using alternative fertilizers.

• Reducing release of pollution into the environment. E.g. treatment of waste water to remove the nitrates and phosphates.

• Removing the pollutant from the environment and restoring ecosystems. E.g. removing mud and reintroducing plant and fish species.

Dead zones

Areas in oceans and fresh water where there is an extremely low oxygen concentration and very little life.

Red tides

A discoloration of seawater caused by a bloom of the toxic red algae (dinoflagellates).

The impacts of waste on the marine environment

Over 80% of marine pollution is cause by land-based activities. This includes dumping very concentrated waste directly into the water. E.g. industrial waste, sewage sludge, and radioactive waste.

60+ L of oil end up in the oceans each year in the US.

Oil pollution

Oil spills happen from time to time. Those are disasters, but it is possible to clean up most of the damage. However, certain species might digest the oil or they might be too far gone already.

Radioactive waste pollution

Radioactive waste is another pollutant that is dumped into the ocean. Between 1958-1992 the USSR and Russia dumped 18 unwanted nuclear reactions containing nuclear fuel into the Arctic Ocean.

Plastic pollution

This is a huge type of water pollution. There are even trash islands floating around in the ocean. 100 million tonnes of plastic waste was found in the central Pacific in 2006.

The hydrological cycle

• The cycle of water, the movement of water and its transformation between the gaseous, liquid, and solid forms.

• Solar radiation drives the cycle.

• Important terms here: evaporation, transpiration, evapotranspiration, precipitation, sublimation, groundwater, run-off, melting.

Sublimation

A change directly from solid to gaseous state without becoming liquid, from ice to vapour.

Evapotranspiration

The evaporation of water from soil plus the transpiration of water from plants.

Advection

The horizontal transfer of energy or matter, usually by the wind.

Percolation

The downward movement of water through soil and rock due to gravity.

Evaporation

The change of water from liquid to gas.

Transpiration

Evaporation of water from the leaves of a plant.

Infiltration

The process by which water on the ground surface enters the soil.

Condensation

The change of water from gas to liquid.

Freezing

The change of water from liquid to solid.

Stream-flow/currents

The movement of water in channels, like streams and rivers.

Flooding

The covering of normally dry land by water. It occurs because the water body is unable to contain the amount of water added to it, e.g. due to heavy rainfalls.

Global water stores

• Only about 2.5% of Earth's water storages are fresh water.

• 97.4% is oceans.

• Storages include: various water bodies (oceans, lakes, rivers, groundwater, glaciers), organisms, soil water, and the atmosphere.

Flows in the hydrological cycle

• Evapotranspiration.

• Sublimation.

• Evaporation.

• Condensation.

• Advection.

• Precipitation.

• Melting.

• Freezing.

• Flooding.

• Surface run-off.

• Percolation.

• Stream flow/currents.

Turnover time

The time taken for water to completely replace itself in a part of the system. Polar ice caps take 10 000 years, while biological water only needs a few hours. Large lakes require 17 years.

Ocean circulation systems

• Oceans cover about 70% of the Earth's surface.

• They are very important to humans, especially as they regulate climatic conditions.

• They are driven by differences in temperature and salinity that affect water density. The resulting difference in water density drives the ocean conveyer belt which distributes heat around the world and affects climate.

• Warm ocean currents move water away from the equater to the poles, and cold ocean currents move water away from the cold regions towards the equator.

Oceanic salinity

• Oceanic water varies in salinity, the average being about 35 ppt.

• Concentrations of salt are higher in warm seas because of the increased evaporation rates of the water.

• In tropical seas, salinity decreases rapidly with depth.

• Run-off from rivers has little effect on reducing salinity. However, very large rivers like the Amazon in South America can result in less or no salt in over a kilometer out to sea.

• The freezing and thawing of ice affects salinity. Thawing decreases it, while freezing increases it temporarily.

• The mineral ions in seawater, chloride and sodium, combine and form salt.

Ocean temperature

• Temperatures vary a lot on the surface of the ocean, but barely at all at depth.

• In tropical and subtropical areas, sea surface temperatures exceding 25C are caused by insolation. From about 300-1000m, temps decline steeply to about 8-10C. Below 1000m, the temps are about 2C.

Water density

• Density in the ocean varies due to water temperature and salinity levels.

• As temperature increases, water becomes less dense.

• As salinity increases, water becomes more dense.

• As pressure increases, water becomes more dense.

• Cold, salty water is more dense than warm, less salty water.

• When large water masses with different desnities meet, the denser water slips under the less dense one. This is one reason for deep ocean circulation patterns.

The Great Ocean Conveyer Belt

• A global thermohaline circulation, driven by the formation and sinking of deep water.

• It's responsible for the large flow of upper ocean water, as well as the transfer of energy by wind, ocean currents, and deep-sea currents.

• The amount of heat given up is about 33% of the energy we receive from the sun.

Specific heat capacity

• The amount of energy required to raise the temperature of a body.

• Water needs more energy than land, which is why the sea is cooler than land during the day, but warmer than land at night.

• Places close to the sea are cool by day, but mild by day. This effect is reduced with increased distance from the sea.

Access to fresh water

• Humans use fresh water for all kinds of things, but the supply is scarce and the demand is high.

• There are over a billion people who don't have access to clean drinking water.

• The availability of fresh water is likely to become more stressed in the future. E.g. due to climate change and rising temps.

• The scarcity of water resources can lead to conflict between human populations, especially on places where the water sources are shared.

Unsustainable demands of water resources

• As population, irrigation, and industralization increase, the demand for fresh water increases.

• In LEDCs, the expanding populations require more water.

• In MEDCs, people require more water for FWPs (washing cars, gardening, etc).

• In LEDCs, 82% of fresh water is used for farming, while in MEDCs it's only 30%.

• There is a risk that fresh water supplies may become limited through contamination and unsustainable extraction.

• Water supplies can be enchanced through reservoirs, redistribution, desalination, artificial recharge of aquifers, and rainwater harvesting-schemes.

• Water conservation, e.g. grey-water recycling, can help to reduce demand, but often requires a change in attitude by the water users.

Sustainably managing water resources

• Individuals and local communities, as well as national governments need to make efforts to make this happen.

• E.g. individuals can take shorter showers and turn off the tap when washing dishes.

• Education campaigns can increase local awareness of issues and encourage water conservation.

• Retain water in reservoirs for use in dry seasons.

• Redistribute water from wetter areas to drier areas.

• Desalinate sea water (expensive).

• Water conservation, e.g. recycle grey-water.

• Making new buildings more water-efficient (e.g. recycling rainwater).

• In agriculture, one could focus on drought-resistant crops and use organic fertilizers and pesticides as they don't contaminate the water as much. One can also invest in efficient sprinklers and irrigation.

Water harvesting

• Making use of available water before it drains away or is evaporated. One can do this by:

• Extraction from rivers and lakes.

• Trapping behind dams and banks.

• Pumping from aquifers.

• Desalinating saltwater to produce fresh water.

• These can be achieved with either high tech or low tech.

World fisheries

• World fisheries and aquaculture produced almost 150 million tonnes of fish in 2010 valued at over $215 billion.

• Over 125 million tonnes were for food. 2/3 of the consumption was in Asia.

• China is the most responsible for the increase in aquaculture.

Fish stocks

• Production of the world's marine fisheries increased from 16.8 million tonnes in 1950 to a peak of 86.4 million tonnes in 1996, and then stabilized at about 80 million tonnes.

• In 2010 it was 77.4 million tonnes.

Global overfishing

• Modern fishing ships can sail further out on the seas and remain there for days and weeks. They can therefore fish less touched areas, which is not good.

• In LEDCs dynamite and cyanide fishing is still common, which isn't great because those methods kill reefs.

• In 2010 a peak in overfishing was reached, namely 32%.

• A solution to this is to improve the technology. E.g. to hinder huge nets from catching all kinds of stuff, one can have sensors that will only target a specific type of fish.

• More than 50% of the fish consumed in Europe is imported because Europe itself is so extremely overfished.

Strategies for the European fishing industry

• Use small meshed nets.

• Protect young fishes and encourage breeding

• Discourage the black fish market.

• Have restrictions on the total allowed catches.

• Match supply to demand.

• Protect sensitive stocks.

• Have tradable fishing permits (like the CO2 thing).

• Restrict number of fishing vessels allowed on the sea.

• Apply penalties to overfishing and other illegal actions.