ACTA PEDOLOGICA SINICA Mar.,2008 N 2 O CH 4 CO 2. Finnigan MAT2253, PreCon 2 ( < 012 ) Mg(ClO 4 ) 2, %, ( GC/ MS) ; CaSO 4 + CoCl 2

Transcription

1 45 2 Vol145,No ACTA PEDOLOGICA SINICA Mar.,2008 N 2 O CH 4 CO 2 (( ), ) GC (PreCon), N 2 O CH 4 CO 2,, ;; X13111 ;O A,,, CO 2 ( GC) ( PreCon) Thermo CH 4 N 2 O, CO 2 CH 4 N 2 O 3 [1 ],,,,,( ), [27 ],, ( < 012 ) (C 11111, N O) 100 ml,,,, 11112, Mg(ClO 4 ) 2, %, ( GC/ MS),, N 2 O 15 N/ 14 N [812 ],,CH 4,50 L Finnigan MAT2253, 100 ml N 2 O CH 4 [13 ],,, N 2 O CH 4 CO PreCon GC,5 (1) ;CaSO 4 + CoCl 2,He PreCon 2 T 2 T 3 1 T 1, :(1943),,, : ;:

2 Fig11 Sketch map of the pre2concentrating device (PreCon) T 1, CO 2 T 2 1 mm, N 2 O CH 4 CO 2,(Valco) T mm, T 2 T 3,T 3 GC, T mm 018 mm, : 4NiO + CH 4 CO 2 + 2H 2 O + 4Ni (Valco) PreCon GC,2 3,,He (2) : ( Inject), He PreCon, GC,He T 2 T 3,GC, (Load), T 2,,N 2 O CH 4 CO 2 T 2, He T 3,GC 2 Fig12 Two working modes of valco

3 2 :N 2 O CH 4 CO Trace GC,25 m 0132 mm Pora plot Q GC : 25, : Pa,:, 113 2( Thermo Finnigan) MAT2253,6, CO 2,45/ 44 ISODAT NT 114,N 2 O CH 4 CO 2 2 N 2 O,N 2 O Finnigan Delta plus, SHOKO N 2 O ( 15 N Air = , 18 O SMOW = ),10 N 2 O 15 N Air ( Air ), 18 O SMOW (SMOW ) CH 4 CO 2, CO 2 CO 2, GW 04407, 13 C PD (PD ), 18 O SMOW ,- 196 T 3, T 3 GC 30 s 3 N 2 O,Cup2 Cup3 Cup4 m/z 44 [ 14 N 14 N 16 O ] + m/ z 45 [ 14 N 15 N 16 O ] + m/ z 46[ 14 N 14 N 18 O] +,m/ z V2 235 s N 2 O, N 2 O 530, CO 2 N 2 O,CO 2 N 2 O 40 s 2 N 2 O m/ z44 m/ z45 m/ z46 3, N 2 O N 2 O 15 N 18 O N 2 O,N 2 O 15 N Air 18 O SMOW, N 2 15 N 18 O 15 N N 2 O, 15 N 15 N %,N 2 O 15 N N 2 O, 303 l m - 3 N 2 O,N 2 O 10, 15 N Air 61943, 18 O SMOW 44195, (1) 2 ( PreCon),,, 211 N 2 O 15 N 18 O 21111, 100 ml 100 ml, N 2 O, PreCon,He,, 25 ml min - 1 He,99199 %CO 2 N 2 O T min,t 2, 1 N 2 O Table 1 Repeated measurements of N stable isotope ratios Measurement number of N 2 O in compressed air in a steel cylinder 15 N Air 18 O SMOW X S1D : 303 l m - 3 N 2 ONote : Concentration of N 2 O in the compressed air is 303 l m - 3

4 252 45,5 d, (2), 15 N, 015, N 2 O Table 2 Repeated measurements of N stable isotope ratios of N 2O Date A in air samples collected on different dates 15 N Air 18 O SMOW N 2 O 15 N Table 4 Repeated measurements of 15 N enrichment of N 2 O Sample No1 in paralled sampling bottles 15 N 15 N atm % CSWT SO62154 A CSWT SO52023 A CSWT SO42064 A CSWT SO32064 A A A CSWT SO62064 A A CSWT SO22074 A A , N 2 O, 15 N 68, 18 O 43 45, 2,5 d ( 3), 15 N 18 O, 3 N 2 O Table 3 Repeated measurements of N and O isotope ratios of N 2O in the same air sample collected from Antarctica Sample No1 Date 15 N Air 18 O SMOW A : 25 ml Note : Sampling volume is 25 ml for measurement 15 ml N 2 O 15 N, 15 N, % (01367 atm %), N 2 O 15 N 6125 %(4), 15 ml,n 2 O 15 N 3 4 N 2 O 15 N 15 N :1815 ml,15 ml Note : Volume of the sampling bottle is 1815 ml, of which only 15 ml is available for measurement, N 2 O CO 2, 23 s,co 2 N 2 O N 2 O,T s,n 2 O 212 CH 4 13 C ml 100 ml, CH 4, T 1, PreCon,He,,He T 1-196, (N 2 O 2 Ar CH 4 ) 1 000, mm CH 4 CO 2 H 2 O CH 4 CO 2 T 2,T 3, GC 30 s 3 CO 2,Cup2 Cup3 Cup4 m/ z 44 [ 12 C 16 O 16 O ] + m/ z45 [ 13 C 16 O 16 O] + m/ z 46[ 12 C 16 O 18 O] +,m/ z44 23 V,2 870 s CH 4,

5 2 :N 2 O CH 4 CO N 2 O Fig13 Mass spectrum of N 2 O in the sample of natural2abundance 4 15 N N 2 O Fig14 Mass spectrum of N 2O in the 15 N2enriched sample CO 2 CO 2 (,Lab1Gas), 2 CO 2 m/ z44 m/ z45 m/ z46, CH 4 CO 2 PD, 13 C PD l L - 1 CH 4, 25 ml 100 ml,, 9 (5),, CH 4 13 C PD , , 5 CH 4, CH 4,m/ z46 50 V,ml 100 ml CH 4,1 ml 7 ml CH 4, CH 4 m/ z44, CH 4,870 s CH 4 CO 2,

6 CH 4 Table 5 Repeated measurements of carbon isotope ratios of CH 4 in Measurement number compressed air in a steel cylinder m/ z44 Ion current intersity of m/ z 44 (V) 13 C PD CH 4 Table 7 Effect of sampling quantity (ml) on carbon isotope ratio of CH 4 Sample No1 Volume of sampling (ml) 13 C PD Y Y Y Y X S1D : 2102 l L - 1 CH 4,25 ml Note : Concentration of CH 4 in a compressed air sample is 2102 l L - 1, sampling 25 ml for measurement 6 CH 4 ( ) Table 6 Measurements of carbon isotope ratios of CH 4 in air samples collected at different times on November 22, 2005 Time 13 C PD 10 : : : : : CH 4 m/ z 44 Fig15 Correlation of CH 4 concentration in an air sample with ion current intensity of m/ z 44 6 CH 4 Fig16 Mass spectrum of CH 4 in the air sample

7 2 :N 2 O CH 4 CO CO 2 13 C 18 O CO 2 CH 4 N 2 O,, CO 2, CO 2, m/ z44 10 V, 100 ml, 5 ml 5 3 CO 2 m/ z 44 m/ z 45 ml m/ z 46 3, CO 2 CaSO 4 + CoCl 2 PreCon 13 C PD 18 O SMOW,He, 21312,,He - 196,, T 2, CO 2,60 s T 2 5 ml,co 2 T 3, 8 9, GC CO 2 (8) 30 s 3,CO 2 CO 2,m/ z V 13 C PD 18 O SMOW, Cup2 Cup3 Cup4 m/ z 44[ 12 C 16 O 16 O] + m/ z 45[ 13 C 16 O 16 O ] + m/ z 46[ 12 C 16 O 18 O] + CO 2 Lab1 Gas, 3,214 s,, CO 2 Table 8 Repeated measurements of C and O stable isotope ratios of CO 2 in two air samples Ambient air sample Compresed air sample Measurement number C PD O SMOW C PD O SMOW X S1D m/ z 44 CO 2 Fig17 Effect of m/ z 44 peak intensity on determination of carbon isotope ratio of CO 2 8 m/ z 44 CO 2 Fig18 Effect of m/ z 44 peak intensity differential on repeated measurements of carbon isotope ratio of CO 2

8 256 45,ml, m/ z 44 CO 2 7,m/ z V, 0127, m/ z 44,8 9, m/ z V 16 V, 0134, 012 CO 2,ml 13 C PD,,, 9 CO 2 Fig19 Mass spectrum of CO 2 in the air sample 9 CO 2 Table 9 Repeatability of measurements of C and O stable isotope ratios of CO 2 in the air sample from the same bottle Sample No1 m/ z 44 m/ z 44 peak intensity (V) Peak intensity differential (V) 13 C PD 18 O SMOW 13 C 13 C value differential FAC 80 A FAC 27 A FAC 03 A FAC 06 A FAC 02 A FAC 14 A

9 2 :N 2 O CH 4 CO CO 2 13 C PD , CO 2 13 C PD - 7 [14 ], CO 2 13 C PD 9 CO 2,,5 ml CO 2,T 2 60 s,m/ z V, 3,GC ( Pre2 Con),, 100 ml, PreCon GC,, GC ( PreCon) N 2 O,CH 4 CO 2,, N 2 O CH 4 CO 2,,, [ 1 ],.. :,, Zhu Z L,Xing GX. eds. Nitrogen Cycling ( In Chi2 nese). eijing : Tsinghua University Press, Jinan University Press, [ 2 ].., 1993, 30 (2) : Cai Z C. Prespects for the research on soil trace gases ( In Chinese). Acta Pedologica Sinica, 1993, 30 (2) : [ 3 ],.., 2002, 22 : Ding W X, Cai Z C. Methane emission from mires and its influencing factors ( In Chinese). Scientia Geo2 graphica Sinica, 2002, 22 : [ 4 ].. :, Gong Z T. ed. Environmental Change of Soil ( In Chinese). eijing : China Science and Technology Press, [ 5 ] Cai Z C, Xing G X, Yan X Y, et al. Methane and nitrous oxide emissions from rice paddy fields as affected by nitrogen fertilizers and water management. Plant and Soil, 1997, 196 : 714 [ 6 ] Xu H, Cai Z C, Tsuruta H. Soil moisture between rice2growing sea2 sons affects methane emission production, and oxidation. Soil Science Socienty of America Journal, 2003, 67 : [ 7 ] Xing G X, Zhu ZL. Preliminary studies on N 2 O emission fluxes from upland soils and paddy soils in China. Nutrient Cycling in Agroe2 cosystems, 1997, 49 : 1722 [ 8 ] Wuebbles D J, Hayhoe K. Atmospheric methane and global change. Earth2Science Reviews, 2002, 57 : [ 9 ] Kim K R, Craig H. Nitrogen215 and Oxygen218 characteristics of ni2 trons oxide : A global perspective. Science, 1993, 262 : [10 ] Yashida N, Norimoto H, Hirano M, et al. Nitrification rates and 15 N abundance of N 2 O and NO - 3 in the Western North Pacific. Nature, 1989, 342 : [11 ] Elkins J W, Wofsy S C, McElroy M, et al. A quatic sources and sinks for nitrous oxide. Nature, 1978, 275 : [12 ] Tanaka N, Rye D M, Rye R, et al. High precision mass spectromet2 ric analysis of isotopic abundance ratios in nitrous oxide by direct in2 jection of N 2 O. International Journal of Mass Spectrometry and Ion Processes, 1995, 142 : [ 13 ] rand W A. PreCon : A fully automated interface for the pre2gc con2 centration of trace gases in air for isotopic analysis. Isotopes Environ2 ment Health Stud., 1995, 31 : [14 ],,.. :, Zheng S H, Zheng S C, Mo Z C. eds. Analysis on Stabl Isotopic Geochemistry ( In Chine2 ses). eijing : eijing University Press,

10 DETERMINATION OF NITRO GEN, CARON AND OXY GEN STAL E ISOTOPE RATIOS IN N 2 O, CH 4, AND CO 2 AT NATURAL AUNDANCE LEVELS Y MASS SPECTROMETER Cao Yacheng Sun Guoqing Han Yong Sun Deling Wang Xi ( State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing , China ) Abstract The increasing effect of greenhouse gases is arousing more and more concern of the people in the world and soil as both a source and a sink of these trace gases has been studied1 Accurate determination of stable isotope composition of these trace gases will help people trace their sources and find out their release patterns1 Isotopic mass spectrometers with a fully automated in2 terface for pre2gc concentration ( PreCon) of trace gases can be used with high precision to determine stable isotope ratios of car2 bon, nitrogen, and oxygen in N 2 O, CH 4, and CO 2 at atmospheric concentrations1 A series of tests including sampling, concentrat2 ing, and mass spectrometric determination were conducted, and accurate and reliable results were obtained, confirming that the method is feasible and applicable to air quality monitoring and the study of atmospheric chemistry, plant respiration, and soil gas generation1 Key words Greenhouse gas ; Stable isotope ratio ; Mass spectrometer