Remote Measurement of Tropospheric NO 2 by a Dual MAX-DOAS over Guangzhou During the 2008 PRD Campaign

Transcription

1 Session h A&WMA International Specialty Conference, May 2010, China Ih: Remote Sensing Technologies for Source Monitoring Remote Measurement of Tropospheric NO 2 by a Dual MAX- over Guangzhou During the 2008 PRD Campaign May 13, 2010 Jihyo Chong Hwa Y. Jeoung Jong H. Beak Hanlim Lee Young J. Kim Y. Zhang Gwangju Institute of Science and Technology ADvanced Environmental Monitoring Research Center

2 Outline Introduction Measurement & Analysis Results and discussions Summary and conclusions 2

3 Effect of Nitrogen Oxides Introduction Atmospheric NO x (NO + NO 2 ) 1.Involved in chemical reactions that lead to catalytic formation in the troposphere 2. Harmful to vegetation and human health: Short-term exposure => airway responsiveness Long-term exposure => malfunction of the human immune system and respiratory infections [US EPA, 2003] 3. Estimated total global NO x emissions: Tg N yr -1 [Dignon, 1992; Benkovitz et al., 1996] 3

4 Nitrogen Oxides in the troposphere When sunlight is introduced in the presence of NO and NO 2, ozone formation occurs as a results of the photolysis of NO 2 at wavelength < 424 nm NO 2 + hv NO + O (1) O + O 2 + M O 3 + M (2) There are no other significant chemical production routes of ozone in the atmosphere other than reaction (2). Once formed, O 3 reacts with NO to regenerate NO 2, NO + O 3 NO 2 + O 2 (3) 4

5 Recent trend in NO 2 loading Introduction Spectra measured by satellite-borne UV/Vis. spectrometers (GOME-2 and SCIAMACHY) are analyzed using the so-called * technique. *Differential Optical Absorption Spectroscopy

6 NO 2 Trend in Northeast Asia(1996~2002) Introduction Constantly increased for 6 years! (East Asia) The NO 2 column observation and trend from a satellite. 6 ACCENT Emissions Workshop Laxenburg, 4 December 2007 Andreas Richter and John P. Burrows [Richter et al, Nature, 2005]

7 Objectives 1. To investigate oxidation processes and determine the rate of NO 2 increase in Pearl River Delta area. 2. To provide quantitative information on the characteristics of temporal variations in the distributions of trace gases, thereby enabling the identification of the emission directions of the major trace gases over PRD. Objective 3. To investigate the performance and capability of the new methodology to retrieve NO 2 profiles in the lower atmosphere with a simple instrumental setup (dual MAX-) To demonstrate novel applications of Differential Optical Absorption Spectroscopy () to study temporal variations of trace gases (nitrogen oxides) 7

8 History of development and application LP- design and measurement of trace gases (Platt et al.,1977; Noxon et al., 1975) Measurement of nitrate radicals (Platt et al., 1979) Measurement of OH radicals (Dorn et al., 1988) Ground-based passive (Noxon et al, 1975; Pfeilsticker et al, 1999) for satellite remote sensing (Richter et al. 1997; Wagner et al., 1999) Ground-based MAX- (Hoenninger and Platt, 2002; Loewe et al., 2002; Lee C. 2005; Lee C. 2008) -Tomography for spatial mapping of atmospheric trace gases by long-path (Laepple et al., 2004) Imaging- for 2-D mapping of atmospheric trace gases by passive (Lohberger et al., 2004; Lee H. et al., 2008) Retrieval of aerosol vertical distribution using MAX- (Sinreich et al., 2005; Friess et al., 2006; Irie et al., 2008) 8

9 Dual MAX- Mini MAX- in 2009 Instrument Telescopes and stepper motor Sealing chamber Schematic of Dual MAX- 9

10 Site Information: Wanqingsha Measurement Viewing direction Site Site Information Wanqingsha, China Latitude : N Longitude : E CAPs NO 2 (ppm) Period China *Class Ⅰ *Class Ⅱ *Class Ⅲ 1-year average (40 μg / m3 ) (40 μg / m3 ) (80 μg / m3 ) 24-hour average (80 μg / m3 ) (80 μg / m3 ) (120 μg / m3 ) 1-hour average (120 μg / m3 ) (120 μg / m3 ) (240 μg / m3 ) 10

11 Gist Dual MAX- Measurement Specification Viewing site clear day Measuring Period : ~ Spectra Range : 290nm ~ 740nm Spectrum resolution : 0.78 Viewing Azimuth Direction : 30 Elevation angles :1, 3, 5, 10, 15, 20, 30, 90 Each measurement sequence: ~ 30 min Measuring site Gas species : NO 2, O 4, SO 2 11

12 Principle Remove by high-pass filtering Lambert-Beer s Law: I(λ) = I 0 (λ) e - [Σσ i (λ) c i L + (σ bi c i + ε Ray (λ) + ε Mie (λ)) L] T(λ)) principle Rayleigh scattering ~ λ -4 narrow- wide band extinction Trace gas absorption absorption cross section σ i (λ) turbulence Lamp I 0 (λ) Mie Scattering ~λ -(1 3) 12 Detector I(λ) [Platt, 1994]

13 MAX- viewing geometry Solar zenith angle θ Zenith principle Vertical Column Density (VCD) Slant Column Density (SCD) Differential SCD (DSCD)= SCD (α)-scd(90) α 3 Stratospheric layer α 2 α 1 Trace gas layer A 4 A 3 A 2 A 1 O Elevation angle α Observer [Hoenninger, 2002] 13

14 Molecular absorption cross sections ( nm) NO 2 ( nm) NO 2 ( nm) Analysis O 4 NO 2 [Courtesy of H. Irie] 14

15 Parameters for NO 2 analysis Analysis Subject Setting Reference spectrum Spectrum measured at noon Cross-sections NO 2, O 4, O 3, Ring, FRS Fitting window nm (UV) nm (visible) Polynomial order 3 (241K ) (223K) 15

16 NO 2 differential slant column density Result Mean DSCD at 3 8.3(±4.8) molecules cm -2 Mean DSCD at 3 1.3(±5.3) molecules cm -2 NO 2 differential slant column densities at different elevation angles in two spectra regions 16

17 NO 2 temporal variation Result [Park et al, ANTL] 17

18 Meteorological parameters (2008 Oct. 27-Nov. 18) Result 18

19 3-day backward trajectory Result Three-day backward trajectories arriving in Wanqingsha at 1200 LT on Oct. 28,

20 Mixing ratios of NO 2 in an UV region Preliminary result MR: the mixing ratio, R: molar gas constant (8.314 J mol -1 K -1 ), T: temperature, P: pressure, M i :the molecular weight of species, LPL: light path length, β constant for unit conversion The mean mixing ratios converted from the DSCDs of NO 2 in a UV region: 42.5(±24.3) ppbv assuming that the trace gas was well mixed within 1-km height of the boundary layer with 1 km LPL. In-situ NO 2 levels was 42.0(±19.8) ppbv. 20

21 Mixing ratios of NO 2 in a visible region Preliminary result The mean mixing ratios converted from the DSCDs of NO 2 in a visible region: 42.2(±17.9) ppbv, assuming that the trace gas was well mixed within 1-km height of the boundary layer with 1 km LPL. In-situ NO 2 levels was 42.0(±19.8) ppbv. 21

22 NO 2 concentration in UV range ( nm) Preliminary result 22

23 NO 2 concentration in visible range ( nm) Preliminary result 23

24 Summary and Conclusion Conclusion We presented that dual MAX- was applied in 2008 PRD campaign and NO 2 have been observed in the polluted area by technique. It is demonstrated that the MAX- technique is capable of measuring trace gases in the boundary layer. The diurnal behavior of NO 2 was U-shape due to the photolysis during daytime. The mean DSCDs of NO 2 in UV and visible regions at 3 elevation angle were 8.3(±4.8)x and 1.3(±5.3) x molecules/cm 2. It was observed that NO 2 came from local areas. NO 2 plays an important role in atmospheric chemistry by acting as a catalyst in the photochemical production of O 3. 24

25 Future plans Future plan The Dual MAX- is mainly planed to observe the temporal variations of NO 2 at each site in lower troposphere, providing the vertical profile. NO 2 profile -Measurement Uncertainty -Measurement by LP Aerosol profile -O 4 measurement with Integration of LIDAR profile data NO 2 mixing ratios with Light path length -Light extinction coefficient by a transmissometer -Angstrom exponent by sunphotometer 25

26 Gwangju Institute of Science and Technology ADvanced Environmental Monitoring Research Center

27 Dis/Advantages of passive measurements Option Advantages Problems Many instruments LIDAR true in-situ measurements proven spatial resolution for some species limited coverage complicated instruments for a single species measurement combination of spatial resolution and sufficient sensitivity problematic expensive solution Passive high sensitivity daytime only relatively cheap (passive technique) Multi-species detection limited spatial resolution (Many trace gases, aerosol)