Atmospheric Composition & Air Quality (MAQ-34806)

Lecturers: Maarten Krol Wouter Peters

Last week

We saw the photochemistry of the troposhereNOx-HOx cycle, role of VOCs, P(O3)

We saw the photochemistry of the stratosphereChapman (O+O3) + catalytic cycles of HOx, NOx, ClOx,...

We learned what controls the production or destruction of ozone in the troposphere

This week

We will study the many forms and effects of nitrogen (N) in our atmosphere

We will perform measurements of NO2

We will interpret them in a practical

N-cycle: reactive vs. non-reactive

Forms of Nr:NH3/NH4

+

NO3-, HNO3

NO, NO2, …orgN (e.g. amino-acids)

N-cycle

N-cycle

N-cycle

N-cycle

N-cycleEfficiency of fertilizer N

100

FertilizerN

N-cycleEfficiency of fertilizer N

100

FertilizerN

14

ConsumedN

N-cycleEfficiency of fertilizer N

100

FertilizerN

14

ConsumedN

94

EffectiveN

-6

N-cycleEfficiency of fertilizer N

100

FertilizerN

14

ConsumedN

94 47

EffectiveN

PlantN

-6 -47

N-cycleEfficiency of fertilizer N

100

FertilizerN

14

ConsumedN

94 47 31

EffectiveN

PlantN

YieldedN

-6 -47 -16

N-cycleEfficiency of fertilizer N

100

FertilizerN

14

ConsumedN

94 47 31 26

EffectiveN

PlantN

YieldedN

FoodN

-6 -47 -16 -5

N-cycleEfficiency of fertilizer N

100

FertilizerN

14

ConsumedN

94 47 31 26

EffectiveN

PlantN

YieldedN

FoodN

-6 -47 -16 -5 -12

14% of the produced reactive Nitrogen is consumed………if you are vegetarian!

N-cycleEfficiency of fertilizer N

100

FertilizerN

4

ConsumedN

94 47 31 7

EffectiveN

PlantN

FoodN

MeatN

-6 -47 -16 -24 -3

4% of the produced reactive Nitrogen is consumed………if you eat the vegetarian!

N-cycle

Intensive agriculture

Industrialisation

Historic development

Closed cycles of nutrients

Labour and Transport

N-cycle

0

1000

2000

3000

4000

5000

6000

7000

1850 1900 1950 2000

Jaar

Worl

d p

opula

tion a

nd

Agri

cult

ura

l are

a

0

10

20

30

40

50

60

70

80

90

Fert

ilize

r and

N

Ox

World population (10^6)

Agricultural area 10^6 ha

Fertiliser Tg

NOx emission

N= Food; Energy = NCarl Bosch Fritz Haber

Nitrification and de-nitrification

1960-1970: Scandinavia, Scotland, US dying off of fish, lakes very blue but little fish population.

1980: Reports of damage to forests in Germany, Scandinavia, Canada, Netherlands, Czecho-Slowakia, Poland.

1985: Effects of eutrophication, too much nitrogen deposition, too much nitrate in drinking water, loss of species in ecosystems, algae blooms

Acid deposition

A short history of acidification:t

99

Robert Angus Smith (1817-1884)Introduced term: Acid RainOld English painting nineteenth

century

Wet deposition and Precipitation chemistry

1717

pH

Pure water H2O ↔ H+ + OH- 7

+ dissolved CO2

CO2(g) + H2O ↔ H2CO3*

H2CO3* ↔ HCO3- + H+

HCO3- ↔ CO3

2- + H+

5.6-5.7

+ dissolved other natural acids

• HNO3 (NOx, lightning, soils, and fires)

• H2SO4 (sulfur gases, volcanoes and biosphere)

• Cl- (ocean)

• Formaldehyde [HCHO]

• Organic acids: formic acid, acetic acid (biosphere)

5 - 7

+ cations • NH4+ (natural, agriculture) (NH3 base in rainwater)

• Ca2+, Mg2+, K+, Na+ (wind blow)

Acid rain: pH < 5

The pH of precipitation

1818

The pH-values in atmospheric water of various types

Why so low? (lower than pH rain)

The pH of rain water (13.1)

But NH3 is a base? What now acid rain?

➡In soils by bacteria:➡NH4

+ + H2O + 2O2 --> NO3- + H2O + 2 H+

(nitrification)➡but also: fertilization (NO3

2-)➡over-fertilization: eutrophication

NH3

Sources: Mainly agriculture (94%)

Fertilizer Liquid manure Animal house

European NH3 emissions

Global sources of NH3 in the troposphere

Source, Tg N yr-1

Anthropogenic

Biomass burning 2

Fertilizers 6

Domestic animals 22

Subtotal 30

Natural

Soils and vegetation 5

Oceans 7

Wild animals 2.5

Subtotal 14.5

Rodhe et al. (1995)

NOx

Envisat picture of NO2 column

Main sources;

Traffic

60 %

Power plants

12%

Industry

15%

Global NOx emissions

European NOx emissions

Current sources of NOx in the troposphere

Source, Tg N yr-1

Anthropogenic

Fossil fuel combustion 21

Biomass burning 12

Aircraft 0.5

Subtotal 33.5

Natural

Soils 6

Lightning 3

NH3 oxidation 3

Transport from stratosphere

0.1

Subtotal 12.1

(1) Dignon et al.,1991;(2) Atherton et al.,1991;(3) Hameed and Dignon,1992;(4) Dignon and Penner, 1991

What goes up, must come down: global N deposition:

mg N m-2 yr-1

Millennium assessment

Growth mainly through increased energy use and more intense agriculture

Sensitivity of EU soils for Acid

Sensitivity of European soils.

5 classes are used,

from white (very insensitive), over light yellow, dark yellow and light red to dark red (very sensitive)

Critical loads for Europe, acidification eutrophication

Translation of sensitivity to acid deposition and eutrophication in critical loads

in moles per hectare per year

Potential acid deposition in Europe in moles per ha per year

F(potential acid)= 2F(SOx) + F(NOy) + F(NHx)

F = Load

F(SOx) = F(sulfate) + F(SO2)

F(Noy ) = sum fluxes of HNO3 and NOx

F(NHx) = sum fluxes NH3 and NH4

Correction for base cations:

F(corrected pot. acid) = 2F(SOx)+F(NOy) + F(NHx) - F(base cations)

Exceedence of critical loads in moles per ha per year

Exceedence in southern Scandinavia because of sensitive soil

Exceedence in middle Europe because of high load

No exceedence in South Europe because of insensitive soil

The Dutch situation for Acid

The Dutch situation for Nitrogen

Wrap-Up

Reactive Nitrogen is central to many environmental issues

The use of fertilizer, meat production, and the burning of fossil fuels are the main sources

The lifetime of Nr is relatively short, so the effects are strongly regional