第五讲 稳定氮同位素
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A DELTA 15-N = +10 ‰ means there is 10 parts per thousand (or permil) more 15-N in the sample than in the standard. A DELTA 15-N = -10 ‰ means there is 10 parts per thousand (or permil) less 15-N in the sample than in the standard.
第五讲
稳定氮同位素
氮同位素及其循环 Nitrogen Isotopes and Nitrogen Cycling
稳定氮同位素: 14N: 99.64% 15N: 0.36%
standard = N2 in air (15N/14N = 0.00368) measured as: N2
典型氮库的同位素组成: Nitrate, rain: -13 to +2 Organic N, soil: 0 to +9 Fertilizer: -5 to +5 Animal waste: +8 to +22
氮同位素及其循环 Nitrogen Isotopes and Nitrogen Cycling
heavy vs. light isotopes the “heavy” isotope is the one with more neutrons; it is also generally the less abundant isotope. enriched vs. depleted remember to state what isotope is in short supply: does “enriched nitrogen” mean that: the nitrogen is enriched in heavy nitrogen OR the nitrogen is enriched in light nitrogen? positive vs. negative -10 ‰ is more positive than -20 ‰ .
Volatilization of NH3
Hog Hog Waste in Lagoon Lagoon
maturation
Mature Lagoon Residual waste
d15Nhog +3‰
d15Nwaste +2‰
d15NNH3 -15 to -25‰
d15NNH4 +30‰
氮同位素分馏 Nitrogen Isotope Fractionation
Primary production in a closed system – Raleigh fractionation
氮来源示踪 Trace the of sources of N
NH4的示踪:
The d15N of NH4 derived from volatilization of NH3 from animal waste lagoons is very low compared to the d15N of other N sources. Nitrification of NH4 produces NO3 with a d15N that is only about 0 to 2‰ higher than the d15N of the NH4 (if most of the NH4 is nitrified).
d15N
氮来源示踪 Trace the of sources of N
•High natural backgrounds, especially in arid and semi-arid environments.
•Widespread use as fertilizer. •Byproduct of animal waste. •Common constituent of chemical processing
(w/r to products) 0 to -24 ‰; -10 ‰ -4 to –5 ‰ 0 to -15 ‰; -3 to -27 ‰ -10 ‰ 0 to -20 ‰ -20 to -40 ‰ ~0‰ ~ -3 to +1 ‰ -3 to -5‰ (?) mM NO3; µM NO3 µM NO3 mM NH4; µM NH4 µM NH4 Concentration dependent Concentration dependent Little enzymatic fractionation Hard to measure NH4+
During biological processes (e.g., assimilation, nitrification, denitrification), the lighter isotope (14N) ends up being concentrated in the products while the heavier isotope (15N) ends up being concentrated in the residual reactants. Hence, during the reaction NO3 N2, the resulting N2 has a lower d15N than the residual NO3. Biological fractionations can make it very difficult to identify sources and quantify mixing proportions.
Sediment denitrification = -0‰
NO3
= 0 to -1‰
[Nitrification]
0
0 100 % of Original Pool 200
氮同位素分馏 Nitrogen Isotope Fractionation
20
Nitrification = 0 to -20‰
d18O (per mil)
(Modified from Kendall, 1998)
氮来源示踪 Trace the of sources of N
地表水体中NO3
Mississippi River Basin (Chang et al., 2002) San Joaquin River Basin (Kratzer et al., 2003) NE USA rivers, (Mayer
氮同位素分馏 Nitrogen Isotope Fractionation
Global average = 4.5 to 5.0 ‰
20
Pelagic denitrification = -20‰
Nitrate uptake
d15N 10
= -5‰
Addition of diazotroph N to nitrate pool
et al., 2002)
氮来源示踪 Trace the of sources of N
地下水环境中NO3可能经历了反硝化作用过程，因此，当用15-N对地下水中 NO3进行示踪时：对化学肥料来源？ 动物排泄物？？ How to estimate the effects of de-nitrification can be estimated using: analysis of dissolved N2 for d15N (to correct for the N2 produced by denitrification), nitrate-δ18O (this tracer usually is not as useful for this purpose as N2-d15N); and geochemical modeling using chemical data and perhaps DIC-d13C, SO4-d34S, etc. use of all 3 methods, along with age-dating of the water using CFCs or 3He/T, will improve quantification of source contributions.
氮同位素及其循环 Nitrogen Isotopes and Nitrogen Cycling
一般讲，城市地下水的δ15N 值较 高，而农村地区较低；
在生活污水和畜禽废水为污染源 的地下水层， δ15N 一般在1%以 上；
农业用地的地下水δ15 N值为0.10% -1.08% ，化肥施用地区地下水δ15 N值较低，有机肥施用地区地下 水δ15N 值较高，有时候超过1.0 %； 当然，施肥的方法、灌溉的情况 及土壤的特性等都会影响同位素 值。
氮同位素及其循环 Nitrogen Isotopes and Nitrogen Cycling 17
不同氮源的δ15 N值分布图
16 15 14 13 12 11 10 9 8 7 6 5 4 3 2
1
-50
-40
-30 -20
-10
0
10
20
30
40
50
1 天然气；2 火成岩；3 火山气；4 受粪肥污染土壤中的氮；5 动物粪便(厩肥)或污水中的 NO3-；6 沉积岩中的有机质；7 石油；8 非豆科植物；9 垦植土壤和受生活污水污染土壤中 的氮；10 土壤有机氮矿化形成的NO3- ；11天然土壤中的氮 ；12 雨水；13 煤；14 受化肥和 工业废水污染土壤中的氮；15 含氮化肥的NO3-；16 豆科植物；17 泥炭
氮同位素及其循环 Nitrogen Isotopes and Nitrogen Cycling
People usually find the negative d values a bit confusing, but they are just a product of what material was chosen as the standard. Example:
Process
NO3 assim: culture, field NH4 assim: culture field Nitrification Denitrification, pelagic sediment N2 Fixation Ammonification
Enrichment factor () Comments
氮同位素及其循环 Nitrogen Isotopes and Nitrogen Cycling
Delta (d) value =
Ratio sample - Ratio standard Ratio
standard
x 1000
Where Ratio is the ratio of 2 isotopes of an element, such as 15N/14N for nitrogen, for a sample or a standard.
氮来源示踪 Trace the of sources of N
环境介质中NO3-的示踪
Just using 15-N isotope
Cannot easily distinguish between: (1) a manure source and
NO3
(2) a fertilizer source that has denitrified to have the same d15N as manure.
氮同位素分馏 Nitrogen Isotope Fractionation
Karl et al., 2002
0‰
0.6‰
-1 to 0‰
-1 to 0‰
light
20-30‰
heavy
氮同位素分馏 Nitrogen Isotope Fractionation
表生环境中，某些作用过程会导致环境中N组分的同位素发 生分馏，这些过程包括：
For N, the ratio of 15N/14N in Air is about 1/250.
If a sample has 1% more 15N than Air (=1/250), its ratio would be: 1.01/250. This 1% corresponds to +10‰. If a sample has 1% less 15N than Air -- (= 0.99/250), this is -10‰.
d15N 10
Ammonium uptake = (-5‰ ??)
Addition of diazotroph N to NH4 pool
NH4
= 0 to -1‰
= (-3 to -5‰ ??)
ห้องสมุดไป่ตู้
Ammonification
0
0 100 % of Original Pool 200
氮同位素分馏 Nitrogen Isotope Fractionation
第五讲
稳定氮同位素
氮同位素及其循环 Nitrogen Isotopes and Nitrogen Cycling
稳定氮同位素: 14N: 99.64% 15N: 0.36%
standard = N2 in air (15N/14N = 0.00368) measured as: N2
典型氮库的同位素组成: Nitrate, rain: -13 to +2 Organic N, soil: 0 to +9 Fertilizer: -5 to +5 Animal waste: +8 to +22
氮同位素及其循环 Nitrogen Isotopes and Nitrogen Cycling
heavy vs. light isotopes the “heavy” isotope is the one with more neutrons; it is also generally the less abundant isotope. enriched vs. depleted remember to state what isotope is in short supply: does “enriched nitrogen” mean that: the nitrogen is enriched in heavy nitrogen OR the nitrogen is enriched in light nitrogen? positive vs. negative -10 ‰ is more positive than -20 ‰ .
Volatilization of NH3
Hog Hog Waste in Lagoon Lagoon
maturation
Mature Lagoon Residual waste
d15Nhog +3‰
d15Nwaste +2‰
d15NNH3 -15 to -25‰
d15NNH4 +30‰
氮同位素分馏 Nitrogen Isotope Fractionation
Primary production in a closed system – Raleigh fractionation
氮来源示踪 Trace the of sources of N
NH4的示踪:
The d15N of NH4 derived from volatilization of NH3 from animal waste lagoons is very low compared to the d15N of other N sources. Nitrification of NH4 produces NO3 with a d15N that is only about 0 to 2‰ higher than the d15N of the NH4 (if most of the NH4 is nitrified).
d15N
氮来源示踪 Trace the of sources of N
•High natural backgrounds, especially in arid and semi-arid environments.
•Widespread use as fertilizer. •Byproduct of animal waste. •Common constituent of chemical processing
(w/r to products) 0 to -24 ‰; -10 ‰ -4 to –5 ‰ 0 to -15 ‰; -3 to -27 ‰ -10 ‰ 0 to -20 ‰ -20 to -40 ‰ ~0‰ ~ -3 to +1 ‰ -3 to -5‰ (?) mM NO3; µM NO3 µM NO3 mM NH4; µM NH4 µM NH4 Concentration dependent Concentration dependent Little enzymatic fractionation Hard to measure NH4+
During biological processes (e.g., assimilation, nitrification, denitrification), the lighter isotope (14N) ends up being concentrated in the products while the heavier isotope (15N) ends up being concentrated in the residual reactants. Hence, during the reaction NO3 N2, the resulting N2 has a lower d15N than the residual NO3. Biological fractionations can make it very difficult to identify sources and quantify mixing proportions.
Sediment denitrification = -0‰
NO3
= 0 to -1‰
[Nitrification]
0
0 100 % of Original Pool 200
氮同位素分馏 Nitrogen Isotope Fractionation
20
Nitrification = 0 to -20‰
d18O (per mil)
(Modified from Kendall, 1998)
氮来源示踪 Trace the of sources of N
地表水体中NO3
Mississippi River Basin (Chang et al., 2002) San Joaquin River Basin (Kratzer et al., 2003) NE USA rivers, (Mayer
氮同位素分馏 Nitrogen Isotope Fractionation
Global average = 4.5 to 5.0 ‰
20
Pelagic denitrification = -20‰
Nitrate uptake
d15N 10
= -5‰
Addition of diazotroph N to nitrate pool
et al., 2002)
氮来源示踪 Trace the of sources of N
地下水环境中NO3可能经历了反硝化作用过程，因此，当用15-N对地下水中 NO3进行示踪时：对化学肥料来源？ 动物排泄物？？ How to estimate the effects of de-nitrification can be estimated using: analysis of dissolved N2 for d15N (to correct for the N2 produced by denitrification), nitrate-δ18O (this tracer usually is not as useful for this purpose as N2-d15N); and geochemical modeling using chemical data and perhaps DIC-d13C, SO4-d34S, etc. use of all 3 methods, along with age-dating of the water using CFCs or 3He/T, will improve quantification of source contributions.
氮同位素及其循环 Nitrogen Isotopes and Nitrogen Cycling
一般讲，城市地下水的δ15N 值较 高，而农村地区较低；
在生活污水和畜禽废水为污染源 的地下水层， δ15N 一般在1%以 上；
农业用地的地下水δ15 N值为0.10% -1.08% ，化肥施用地区地下水δ15 N值较低，有机肥施用地区地下 水δ15N 值较高，有时候超过1.0 %； 当然，施肥的方法、灌溉的情况 及土壤的特性等都会影响同位素 值。
氮同位素及其循环 Nitrogen Isotopes and Nitrogen Cycling 17
不同氮源的δ15 N值分布图
16 15 14 13 12 11 10 9 8 7 6 5 4 3 2
1
-50
-40
-30 -20
-10
0
10
20
30
40
50
1 天然气；2 火成岩；3 火山气；4 受粪肥污染土壤中的氮；5 动物粪便(厩肥)或污水中的 NO3-；6 沉积岩中的有机质；7 石油；8 非豆科植物；9 垦植土壤和受生活污水污染土壤中 的氮；10 土壤有机氮矿化形成的NO3- ；11天然土壤中的氮 ；12 雨水；13 煤；14 受化肥和 工业废水污染土壤中的氮；15 含氮化肥的NO3-；16 豆科植物；17 泥炭
氮同位素及其循环 Nitrogen Isotopes and Nitrogen Cycling
People usually find the negative d values a bit confusing, but they are just a product of what material was chosen as the standard. Example:
Process
NO3 assim: culture, field NH4 assim: culture field Nitrification Denitrification, pelagic sediment N2 Fixation Ammonification
Enrichment factor () Comments
氮同位素及其循环 Nitrogen Isotopes and Nitrogen Cycling
Delta (d) value =
Ratio sample - Ratio standard Ratio
standard
x 1000
Where Ratio is the ratio of 2 isotopes of an element, such as 15N/14N for nitrogen, for a sample or a standard.
氮来源示踪 Trace the of sources of N
环境介质中NO3-的示踪
Just using 15-N isotope
Cannot easily distinguish between: (1) a manure source and
NO3
(2) a fertilizer source that has denitrified to have the same d15N as manure.
氮同位素分馏 Nitrogen Isotope Fractionation
Karl et al., 2002
0‰
0.6‰
-1 to 0‰
-1 to 0‰
light
20-30‰
heavy
氮同位素分馏 Nitrogen Isotope Fractionation
表生环境中，某些作用过程会导致环境中N组分的同位素发 生分馏，这些过程包括：
For N, the ratio of 15N/14N in Air is about 1/250.
If a sample has 1% more 15N than Air (=1/250), its ratio would be: 1.01/250. This 1% corresponds to +10‰. If a sample has 1% less 15N than Air -- (= 0.99/250), this is -10‰.
d15N 10
Ammonium uptake = (-5‰ ??)
Addition of diazotroph N to NH4 pool
NH4
= 0 to -1‰
= (-3 to -5‰ ??)
ห้องสมุดไป่ตู้
Ammonification
0
0 100 % of Original Pool 200
氮同位素分馏 Nitrogen Isotope Fractionation