Aquatic Biology Acidification Causes, Consequences and Solutions
Introduction to Acidification By Alastair Frater
Introduction to Acidification n Acidification - definition n Acidification - basic description n Social considerations n Legal considerations
Acidification - definition n Change towards more acidic conditions in: n Rain and cloud water n Lakes n Rivers n Groundwater n Soils
Acidification - basic description n Two speeds of acidification n Slow - due to biological and geological processes n Fast - due to climatic fluctuations or volcanic eruptions; or by human activity n Air pollution - direct and indirect n Emissions from industry
Aquatic environment acidification n Three criteria to be met n 1 - Increase of atmospheric anion deposition n 2 - Poor anion retention of soils n 3 - Low alkalinity
Social considerations n Industries important to society n Problems of control n Location of source n Location of affected area n Emission producer & importer co- operation
Legal considerations n International legal considerations n International co-operation on control n Complications?
Acidification n Domestic and commercial waste /general pollution n Agricultural input n Acid Rain
Domestic and commercial waste /general pollution n Water stores throughout the world are subject to stress; because its used for water supplies, industry and recreation. n Even though the wastewater's are treated, large quantities of contaminants flow downstream. n Domestic sewage includes human wastes and a variety of waste materials that arise from household products.
Agricultural input n Plants need nutrients in order to complete their life cycles. n Fertiliser are used to supplement or replace, the nutrients supplied by natural processes. n These artificial chemicals contain pollutants that will ultimately change the pH of surface water, through runoff.
Acid Rain n Rainwater was once the purest form of water available but now is often contaminated by pollutants in the air. Acid rain is caused when industrial emissions mix with atmospheric moisture. Pollutants may be carried in clouds for long distances before falling., which means that forests and lakes far away from factories may be damaged by acid rain. In the near vicinity of the factories, additional damage is caused by the deposition of larger pollutant particles falling to the ground in dry form. Air pollution has been increasing since the Industrial Revolution but only recently have side effects such as acid rain become severe and widespread enough to evoke international concern.
n Forests, lakes, ponds, and other terrestrial and aquatic environments throughout the world are being severely damaged by the effects of acid rain. Acid rain is caused by the combination of sulphur dioxide and nitrogen compounds with water in the atmosphere. In addition to chemically burning the leaves of plants, acid rain poisons lake water, killing most, if not all, the aquatic inhabitants.
Intro n Direct effects of Sulphuric acid. n Indirect effects of Sulphuric acid. n Case Study.
Direct Effects n Sulphuric acid (H2SO4) directly interferes with the fishs ability to take in oxygen, salt and nutrients. n Acid causes mucus to form in the gills and can lead to suffocation. n Salt levels such as Ca²+ cannot be maintain and results in failure of reproduction.
n Eggs become too weak or brittle to survive. n Ca²+ deficiency also causes weak spines and deformities. n Crayfish need Ca²+ to maintain healthy exoskeleton.
Indirect effects n Sulphuric acid causes heavy metals to be released from soils. n Al²+ is released from a harmless compound into soils and eventually into lakes. n Al²+ Burns the gills of fish causing respiratory problems.
n It also accumulates in the organs causing damage and eventually death. n Although many fish can tolerate a pH of 5.9, this is enough to release Al² from the soil to enter the aquatic environment. n This is further augmented by spring acid shock.
Spring Acid Shock n When snow melts in spring a large quantity of acids and chemicals are released into the soils. n The acids and chemicals will make their way into lakes. n This causes a dramatic change in the pH in lakes.
n The aquatic water system has no time to adjust to the sudden change. n Springtime is a vulnerable time for many aquatic species since it is the time for reproduction. n This may cause severe deformities or even annihilate the whole species.
Case Study - Lake 223 n Since 1976 Lake 223 was monitored n Over the years man crustaceans died out due to reproduction failures. n At a pH of 5.6 algae growth was hindered. n Larger fish died due to problems in reproduction n There were more adult fish in the lake than young ones.
n By 1983 Lake 223 had reached a pH of 5 and the surviving fish were thin and deformed and unable to reproduce.
Solutions to acidification n Two ways of attacking acidification – Stop air pollution at its source and so reduce acid rain. –Combat the effect of acidification.
Attacking the Source n This involves reducing the emissions of SO 2 and NOx gases n E.C. directives such as BATNEEC and the Helsinki agreement in 1985
Controlling the effects of acidification n This involves increasing a streams or lakes buffering capacity. BUT – Only a temporary solution –Can kill aquatic organism –How much and where?
Recovery n If pollution is cut off at its source then lakes and streams will recover firstly chemically and then biologically. However due to the complexity of natural habitats the time of recovery can vary a huge amount between aquatic environments.