Transcript NH 3

Effects of Ammonia on Terrestrial Vegetation
Speaker
Dr. Sagar Krupa
University of Minnesota
The Nitrogen Cycle
Soil
organic
material
NO3–
–NH2
NO2–
NH4+
2NH4 + 3O2  2NO2 + 2H2O + 4H
2NO2 + O2  2NO3
Source: Modified from Brady (1990)
and Krupa (2003)
(2N)
ADP
H2O, P1
2-oxoglutarate
glutamine
2e–, 2H+
glutamate
synthase
GOGAT
glutamine
synthase
GS
ATP
NHy
NAD(P)H, Fdred
glutamate
(1N)
glutamate
amino acids
proteins
metabolism
Source: Modified from Fangmeier et al. (1994)
(3N)
(3N)
(2N)
(4N)
Source: Modified from
Garrett and Grisham (1997)
Summary Examples of Atmospheric
NH3 Concentrations*
Location
Concentration**
Comment
Remote
<50 ppt (0.035)
Background mean
UK
0.085–15.40 ppb
(0.06–11)
Annual mean (1996–2000)
Alberta,
Canada
0.37 ppb (0.26)
2.16–2.88 ppb (1.5–2.0)
11.62–16.66 ppb (8.3–11.9)
2-year background mean
Agricultural area: mean
Maximum
California
57 ppb (39.67)
<1–2 ppb (0.70–1.4)
Winds from cattle feedlots,
dairy and poultry farms
Winds from other directions
UK
84 ppb (60)
4.2 ppb (3.0)
Close to poultry farm bldg.
650 m from bldg.
Canada
350 ppb (250)
Forest fires
*Source: Modified from Krupa (2003).
**Values in parentheses are in µg m–3.
Summary Examples of Deposition
Velocities (Vd) for NH3 and NH4+ (cm s–1)*
Chemical
Species
Receptor
Range Vd
NH3
Soil
0.06–1.0
Bog
0.10–1.9
Herb
1.6
Different species (Day)
(Night)
0.30–1.3
0.03–0.13
Tree species
0.50–3.6
Bog
0.20
Herb
0.44–0.60
Tree species
0.50–1.5
NH4+
*Source: Modified from Krupa (2003).
Concentration gradient
Compensation point
Stomatal opening
Shoot uptake
(NH3/NH4+)
NHy
accumulation
NHy pool
Shoot NHy
assimilation
N organic
Root uptake
(NH4+)
Toxicity
Primary
effects
Root NHy
assimilation
Assimilation capacity
Developmental stage
Secondary
effects
Pathways and factors governing the effects of NH3 on plants.
Source: Modified from Fangmeier et al. (1994).
Summary Examples of Experimental NH3
Exposures in Chambers or Greenhouse
Conditions in Vegetation Effects Studies*
Parameter
Measured
N and nutrient content
Visible foliar injury
Dry weight
Mean
Exposure
Exposure
Duration
Concentration (Weeks)
(ppb)
~35
~69
~125–1250
32
38
13
~21
~167
~104–208
~3
2–3
~7
~35–70
~140
~12–32
12
~69
~104
20
21
~125–139
~12
Frost hardiness
Mycorrhizae
*Source: Modified from Krupa (2003).
Source: Krupa (2003)
Source: Krupa (2003)
Summary of Examples of Plant
Responses to NH3 Exposures:
General Trends*, **
Parameter
Effect***
N content
Visible foliar injury
Parameter
Nutrient content
(e.g., P, K)
0
Flowering
Dry weight
Height growth
Shoot : Root ratio
Survival rate
Frost hardiness
Mycorrhizae
Visible injury (NH3 –
SO2)
Survival rate (NH3 –
SO2)
Frost hardiness (NH3 –
SO2)
Visible injury (NH3 –
O3)
*Source: Modified from Krupa (2003).
**Most results based on chamber or greenhouse studies.
*** = Increase, = Decrease, 0 = No change.
Effect
Selected Plant Species Very Sensitive to
Acute or Visible NH3 – Induced Foliar
Injury*,**
Common
Name
Latin Name
Common
Name
Latin Name
Barley
Hordeum vulgare
Bean
Phaseolus vulgaris
Cauliflower
Brassica oleracea
Pea
Pisum sativum
Crops
Trees & Shrubs
Hawthorn
Crataegus spp.
Pine, white
Pinus strobus
Poplar,
balsam
Populus balsamifera
Spirea
Spirea vanhouttei
Rhacomitrium
lanuginosum
Ragweed
Ambrosia
artemisifolia
Others
Moss
*Source: Modified from Krupa (2003).
**There are a total of more than 150 plant species that contain cultivars, varieties and
genotypes that are either sensitive or intermediate in their response.
Summary Examples of the Range of NH4+ –
N Deposition (kg ha–1 yr–1) in Open Fields
and Under Different Plant Canopies*
Plant Species
Canopy
Deposition
(1)**
Bulk
Deposition
(2)**
Ratio (1):
(2)***
Conifer
30.1–95.6
9.2–14.1
2.70–6.80
Deciduous
42.0
16.8
2.50
Grass
28.0
14.0
2.00
Heather
19.6
11.2
1.75
*Source: Modified from Fangmeier et al. (1994).
**Canopy deposition = Through-fall + stem-flow, Bulk deposition = open area.
***Range calculated from individual data points.
Some Examples of N Saturated Forests
in North America*
Location
Forest
Type
Elevation N Input
(m MSL)
(kg ha–1 yr–1)
N Output
(kg ha–1 yr–1)
Cascade Mts., WA
Red alder
220
4.7 + >100 (N2 38.9
fixation)
Turkey Lakes, ON,
Canada
Sugar maple,
yellow birch
350–400
7.0–7.7 (as
throughfall)
17.9–23.6
Whitetop Mt., VA
Red spruce
1650
32**
47**
Great Smoky
Mt. Natl. Park, NC
Red spruce
1800
10.3
19.2
Front Range, CO
Alpine
tundra, subalpine conifer
3000–
4000
7.5–8.0
7.5
*Source: Modified from Fenn et al. (1998).
–
**Values appear high. However, according to the specific authors, NO3 concentrations in the
soil solutions were high and there was a lack of tree growth response to N fertilization and
therefore, N saturation.
Some Examples of Distribution and fate of
NH4+ - N Applied to Forest Ecosystems*
Location
Forest Type
Elevation
(m, MSL)
N input
(kg ha–1
yr–1)
N output
(kg ha–1
yr–1)
Thompson Forest,
Cascade Mts., WA
Red alder
220
4.7 + >100
N2 fixation
38.9
Adirondack Mts.,
NY
Northern
hardwoods,
hardwood/conifer
396–661
9.3
Stage 1 N
loss
San Gabriel Mts.,
CA
Chaparral,
grasslands
580–1080
23.3
0.04–10
Great Smoky Mts.
Natl. Park, NC
Red spruce
1800
10.3
19.2
Front Range, CO
Alpine tundra,
sub-alpine conifer
3000–4000
7.5–8.0
7.5
*Source: Modified from Fenn et al. (1998).
Critical Loads for Total N Deposition*
Ecosystem
Critical Load
(kg N ha–1 yr–1)
Forests on silicate soil
3–14
Forests on calcareous soil
3–48
Acidic (managed) coniferous forest
15–20
Acidic (managed) deciduous forest
<15–20
Lowland dry-heathland
15–20
Lowland wet-heathland
17–22
Species-rich heaths/acidic grasslands
<20
Arctic and alpine heaths
5–15
Calcareous species-rich grassland
14–25
Neutral-acid–species-rich grassland
10–15
Montane-subalpine grassland
10–15
Mesotrophic fens
20–35
Ombotrophic bogs
5–10
Heather, bogs
5–10
Forests
10–20
*Source: Modified from Fangmeier et al. (1994).
Importance of Environmental Variables with
a Significant (p ≤ 0.05) Effect on Lichens*
Variable
% Variance
SO2
15
NO2
5
Tree species
9
Bark pH
4
NH3
2
Others (tree diameter, interactions)
Bark SO42-, NO3-, NH4+
10
n.s.
Sub-total
45
Variability not accounted or variability
accounted by parameters not measured
55
*Source: Modified from Van Dobben and Ter Braak (1998).
Fundamental Differences in the Effects of
Atmospheric SO2 and NH3 on Terrestrial
Higher Plants and Epiphytic Lichens*
Variable
Higher Plants
Lichens
Sulfur dioxide
(SO2)
Soil acidification, mobilization of Al
and mobilization of transition metals
within wood
Toxicity
Ammonia (NH3)
Soil acidification due to nitrification,
mobilization of Al, increased N
availability
Increase in
bark pH
Other
environmental
factors
Changes in inter-species competition
due to N availability
Adverse
effect
*Source: Modified from Van Dobben and Ter Braak (1998).
“Critical Levels”
The concentrations of pollutants in the atmosphere
above which direct adverse effects on receptors, such as
plants, ecosystems or materials may occur according to
present knowledge (UN-ECE, 1988).
“Critical Loads”
A quantitative estimate of an exposure to one or more
pollutants below which harmful effects on specified
sensitive elements of the environment do not occur
according to present knowledge
(Nilsson and Grennfelt, 1988).
Critical Levels (Exposures) for NH3*
NH3 – Concentration
ppb (µg m–3)
Duration
4752 (3300)
1 hour
389–397 (270–276)
1 day
29–72 (20–50)
1 month
11.5 (8)
1 year
*Source: Modified from Fangmeier (1994).
Critical Loads for Total N Deposition
(Summary)
5–10 kg ha-1 yr-1 of Total (dry + wet) N
Deposition would protect heaths, bogs, cryptogams, etc.
10–20 kg ha-1 yr-1 of Total (dry + wet) N
Deposition would protect forests (depending on the soil
conditions)
Atmospheric Ammonia Eco-toxicology:
Terrestrial Vegetation
1. Air Concentrations: Expected No Effects Value (ENEV)
NH3 concentration 48 µg m-3 = Load Flux 24–290 kg N ha-1 yr-1
2. ENEV – Mean Compensation Point (ENEVcp)
5.1 µg m-3 = Load Flux 4.8–58 kg N ha-1 yr-1
3. Critical Load Threshold Flux Density
10 kg N ha-1 yr-1
(Sheppard, 2002)
Critical Loads
1.
Most Sensitive Ecosystems
5–10 kg N ha-1 yr-1
2.
Forests
10–20 kg N ha-1 yr-1