(a) Natural sources of pollutants (b) Anthropogenic sources of pollutants (c) Main pollutants (d) Dispersal

Transcription

1 (a) Natural sources of pollutants (b) Anthropogenic sources of pollutants (c) Main pollutants (d) Dispersal Irish context A chemical at the wrong place and at the wrong concentration maybe either a pollutant or a contaminant Ozone maybe either beneficial or harmful depending upon its position in the atmosphere.

2 120 Stratospheric ozone absorbs much of the earth s incoming UV solar radiation and thereby shields organisms from its deleterious effects. Thermosphere Mesopause Stratopause Mesosphere Tropopause Stratosphere Troposphere Temperature (degrees centigrade) From Wellburn (1994) UV light breaks off Cl Cl CFC Cl O 2 Cl is free to attack another ozone molecule Cl attacks ozone pulling oxygen atom off O 3 Cl ClO Free oxygen atom pulls O off Cl ClO Cl and O form chlorine monoxide O 2

3 Dangerous for humans because of elevated UV exposure in early Australian summer UV radiation levels can increase up to 20% 120 Thermosphere Mesopause Stratopause Mesosphere Tropopause Stratosphere Troposphere Temperature (degrees centigrade) From Wellburn (1994)

4 after van Dingenen et al., (2008) Air pollution covers those pollutants that are emitted into the atmosphere as gases or particulates which then, directly or indirectly, degrade or adversely affect physical and biological systems. In atmosphere, pollutants may move from dry gaseous phase into liquid phase before falling to surface (wet deposition) or return to the surface of the earth as dry deposition

5 The distance that these pollutants may travel is staggering. In the Eastern USA, one third of the sulphur compounds deposited originate from sources greater than 500 km (300 miles away), another one-third comes from sources between 200 and 500 km away ( miles), and the remainder comes from sources less than 200 km away. Much of air pollution in central and northern Europe arises outside of national boundaries

6 Fires particulates, smoke, ash, soot Volcanoes acid mists, sulphur dioxide, other toxic gases Storms particulates, dust and soil Fires particulates, smoke, ash, soot Volcanoes acid mists, sulphur dioxide, other toxic gases Vegetation some trees and bushes emit volatile organic compounds, pollen spores, fungal spores

7 Primary Pollutants Pollutants emitted directly into the atmosphere from the source Secondary Pollutants Pollutants formed in atmosphere from chemical reactions often utilising solar radiation as a source of energy for these reactions. Primary Pollutants Pollutants emitted directly into the atmosphere from the source Sulphur dioxide Carbon monoxide Particulates Hydrocarbons Nitrogen oxides Lead

8 Secondary Pollutants Pollutants formed in atmosphere from chemical reactions often utilising solar radiation as a source of energy for these reactions. Photochemical oxidants Ozone Nitrogen oxides Hydrocarbons after Cunningham et al., (2003)

9 Sulphur Dioxide SO 2 Sulphur dioxide is a corrosive acid gas which combines with water vapour in the atmosphere to produce acid rain. Oxidises in the atmosphere to form SO 3, which then reacts with water in the atmosphere to give sulphuric acid, H 2 SO 4 Sulphur Dioxide SO 2 Sulphur dioxide is a corrosive acid gas which combines with water vapour in the atmosphere to produce acid rain. Both wet and dry deposition have been implicated in the damage and destruction of vegetation and in the degradation of soils, building materials and watercourses. SO 2 in ambient air is also associated with asthma and chronic bronchitis.

10 Sulphur Dioxide SO 2 Since the decline in domestic coal burning in cities and in power stations overall, SO 2 emissions have diminished steadily and, in most European countries, they are no longer considered to pose a significant threat to health. This is not the case for USA and China where SO 2 is still a problem.

11

12 Europe Emissions of most key air pollutants have declined over the whole of Europe since the early 1980s. By the end of 2000, emissions of sulphur compounds have been reduced to less than one-third of 1980 levels in Western Europe, and to two-thirds of those levels in CEE. Average figures, however, mask a wide variation among countries and sub-regions. SO 2 emissions increased by 7 per cent in Greece and 3 per cent in Portugal between 1990 and 1998 while reductions of 71 per cent and 60 per cent were observed in Germany and Finland respectively (EEA 2000). In Ireland SO 2 is clearly no longer a problem. The 98- percentile concentrations are typically about 50 µg/m 3 whereas the applicable limit value is 250 µg/m 3.

13 The sale, marketing and distribution of bituminous coal, primarily used for domestic heating, was banned in Dublin in Box-and-whisker plot of annual mean Black Smoke (BS) levels in Dublin between two study periods (pre and post- ban periods),

14 SO 2 emissions in Ireland reduced considerably between 1990 and The latest estimates indicate a decrease of 82.1 per cent from kt in 1990 to 32.7 kt in Power stations remain the principal source of SO 2 emissions, contributing 48 per cent of the total in 2009 Flue gas desulphurisation material

15 USA EPA 2011

16 In terms of air pollution NOx are nitrogen dioxide (NO 2 ), nitric oxide (NO) and nitrous oxide (N 2 O). NO 2 and NO are formed primarily from the internal combustion engine (therefore a direct link with vehicular traffic), whilst N 2 O is formed primarily by bacterial reactions in soil (direct link with agriculture). Nitrogen oxides are formed during high temperature combustion processes from the oxidation of nitrogen in the air or fuel. The principal source of nitrogen oxides - nitric oxide (NO) and nitrogen dioxide (NO 2 ), collectively known as NOx - is road traffic, which is responsible for approximately half the emissions in Europe. NO and NO 2 concentrations are therefore greatest in urban areas where traffic is heaviest. Other important sources are power stations, heating plants and industrial processes.

17 Nitrogen dioxide has a variety of environmental and health impacts. It is a respiratory irritant, may exacerbate asthma and possibly increase susceptibility to infections. In the presence of sunlight, it reacts with hydrocarbons to produce photochemical pollutants such as ozone in the trophosphere, and photochemical smog. Through conversion to nitric acid in the atmosphere is also a significant contributor to acid rain Unlike SO 2, NOx emissions have not decreased significantly in Europe. On a global scale this class of pollutant is increasing.

18 In Ireland, NO 2 is one of the highest priority pollutants for monitoring and control even though urban data shows compliance with the current 98-percentile hourly limit value of 200 µg/m 3. Mean annual data hides a multitude of sins. In 2002 this limit was breached on 15 days (a limit to the number of days being 18). In 2001 this hourly limit was breached on 178 days!

19 Ireland s national emission ceiling for NOx under the NEC Directive is 65 kilotonnes (kt), to be achieved by This is equivalent to a 49.7 per cent reduction from the 1990 baseline level of kt NOx. Photochemical oxidants Products of secondary atmospheric reactions driven by solar energy

20 Ozone can irritate the eyes and air passages causing breathing difficulties and may increase susceptibility to infection. It is a highly reactive chemical, capable of attacking surfaces, fabrics and rubber materials. Ozone is also toxic to crops, vegetation and trees. Since the 1980 s it has been widely accepted that of all the atmospheric pollutants, ozone is the most important with regard to crop production in Europe and North America, whether by reductions in potential crop yield or by unsightly damage.

21 Ozone is one of the most powerful oxidants known, with only a slightly lower oxidation potential than fluorine. Reactions of ozone with water and solutes in the apoplast lead to the formation of free radicals, such as the hydroperoxide (. O 2 H) and the superoxide (. O 2- ) radicals

22 Unlike the United States of America where significant crop loss and forest damage to ozone is commonplace, in Ireland ozone is not considered a problem. Median hourly ozone concentrations typically range from 40 to 80 µg/m 3 and maximum values very rarely exceed the population information threshold of 180 µg/m 3.

23 EPA web site Bush (2003) Ecology of a Changing Planet. Chapter 22 Cunningham et al., (2003) Environmental Science: a Global Concern. McGraw Hill. Chapter 18 (Hamilton N06*2) Wellburn (1999) Air Pollution and Climate Change. Longman (Hamilton M8*1)