Test 2.3 Acidification of Freshwaters

Question 1

Natural pH of rainfall

Answer 1

5.6 due to CO2 reaction and rainfall

Question 2

What is the cause of anthropogenic acidification?

Answer 2

Burning of fossil fuels and wet & dry deposition of acids

Question 3

Equation for acidification of rain

Answer 3

CO2 + H2O H2CO3 (Carbonic acid)

Question 4

At what pH determines whether rain is acidic or not

Answer 4

<5.6

Question 5

Causes of acid rain

Answer 5

1. Industrial pollution 9SO2 & H2S) from oil & coal burning power stations and industrial plants. - Forms sulphuric acid
2. NOX from car exhausts, power stations and industrial combustion. Forms nitric acid with rainfall
3. Land use change, such as afforestation, has enhanced acidification processes

Question 6

What is wet acid deposition?

Answer 6

Acids in forms of precipitation

Question 7

What is dry deposition?

Answer 7

Oxides of sulphur and nitrogen adsorbed onto surface of particles in the atmosphere e.g. fine dust & sand

Can be intercepted by ground e.g. trees

Question 8

Global biggest 3 sources of sulphur and oxides of nitrogen production?

Answer 8

Europe, China & North America

Westerly flow of air wafts pollution across Scandinavia: killing off artic char & brown trout

Question 9

Globally where are soils most sensitive with the lowest buffering capacity?

Answer 9

North America

Northern & western Britain, parts of Ireland

Question 10

How can afforestation of conifers cause more acid pollution?

Answer 10

Afforestation of conifers
-Increased deposition of gases and particles intercepted by canopy

Ion exchange of nutrients in roots as they pump hydrogen ions into soil.

Al3+ released where soils lack Ca2+ & Mg2+: Increased conc.s enter streams
-Al complexes with P making it biologically unavailable and lakes become oligotrophic

Increased acidity from litter fall

Increased base cation uptake (Ca, Mg) lowers buffering capacity

More rapid runoff due to drainage; reduced buffering capacity

Question 11

What are the impacts of acid pollution on fish?

Answer 11

Eggs, juveniles and adults cannot survive pH lower than 5

Particularly in NW Britain, Scandinavia; salmonids and trout

Question 12

Impacts on fish in water with pH <5.0

Answer 12

Ionic damage occurs: blood has high levels of Na and Cl ions

Reduces osmotic potential of gills

Aluminium causes secretion of mucous on gill surface: cannot take up oxygen

Question 13

How does species abundance in terms of vertebrates and invertebrates change in acidic waters?

Answer 13

System dominated by vertebrate predators –> Dominated by invertebrate predators e.g. caddisflies

Question 14

What are the tolerance pH levels of macro invertebrates?

Answer 14

Gammarus very sensitive pH <7

Mayflies pH <6.5 lose Baetidae and Heptageniidae

Most tolerant are stoneflies where pH 4-5

Question 15

How do acidic waters affect snails?

Answer 15

Calcium difficult to obtain in low pH

Shells become thin and break

Question 16

How do acidic waters affect microbes?

Answer 16

Loss of aquatic fungi

reduce nutrient procession- reduction in decomposition

Extends amount of CPOM available for shredders as it not broken down by fungi

Question 17

How do acidic waters affect algae?

Answer 17

Change from diverse and complex diatom algal community in non acid streams to more specialised group.

Eutonia very acid tolerant

Question 18

How are grazers, collectors and shredders affected by acid waters?

Answer 18

Grazers and collectors are eliminated

Shredders dominant

Question 19

What are the solutions to acid pollution?

Answer 19

Liming: added powdered limestone to catchment rivers and lakes: rehabilitation by natural processes

Question 20

What are acid reference sites?

Answer 20

Streams that are acid polluted but unlined

Question 21

What are the reasons for improvement in water quality but not biodiversity after liming?

Answer 21

Adults would need to fly in and lay eggs to repopulate. Have not arrived or cannot physically get there yet: geographical isolation

Question 22

What is community closure?

Answer 22

Chemical problems still, resources altered. System has been changed due to pollution.
Animals can and do get there but conditions don’t allow them to colonise

Question 23

Malaise trap

Answer 23

Black mesh; heats in sun> attracts insect> hide underneath in shade> crawl up and fall in pots

Question 24

How do malaise traps work and what do they show?

Answer 24

Show adult fly populations surrounding the streams

Black mesh; heats in sun> attracts insect> hide underneath in shade> crawl up and fall in pots

Question 25

What are the differences in malaise trap findings between polluted & unpolluted sites

Answer 25

Unpolluted: lots of adult and larvae on bank

Polluted: missing larvae from stream and adults from the bank

Post limed sites: Adults present at banks but larvae not in water; shows they can reach the stream but conditions aren’t quite right yet