5:15 PM - 6:30 PM
[MIS06-P03] Observation of O3 flux in red pine forest
Keywords:ozone, flux, forest
The emission and absorption of trace gases at the biosphere affects to atmospheric chemistry, and thus it makes influence with potential indirect effects on carbon cycle and climate (Ollinger et al., 2002). We constructed and tested O3 and NOx flux measurement system with the gradient method at a meteorological tower in red pine forest (Site Code: FJY) in the autumn of 2014 and 2015. We also measured CO2 flux at the same meteorological tower for validation of the system by comparison with CO2 flux determined by the eddy covariance method.
The heights of the forest canopy and the meteorological tower were about 25 m and 32 m. Concentrations of O3, NOx and CO2 were measured at two heights (26 m and 32 m in 2014, 26 m and 34 m in 2015) above the canopy by an ultraviolet absorption O3 analyzer (Thermo: 49C), a chemiluminescence NOx analyzer (Thermo: 42iTL) and an infrared absorption CO2 analyzer (Licor: LI-820). The O3 instrument was calibrated before the observation, and the NOx and the CO2 instruments were calibrated every three weeks at the observation site. The air was sampled every 300 seconds from each two vertical heights and supplied to the analytical instruments through PFA tube. Concentration of CO2 was also measured by an infrared absorption CO2 analyzer (Licor: LI-6262) at 26.5 m to determine CO2 fluxes by the eddy covariance method. Wind speed and wind direction were measured at 26.5 m and they were used to obtain fluxes by the gradient and eddy covariance methods.
The CO2 fluxes in the day time (9:00-16:00) in the autumn of 2014 were observed with the gradient and the eddy covariance method as -9.0±7.3 mmol m-2 s-1 and -8.6±6.5 mmol m-2 s-1, respectively. The CO2 flux obtained by the gradient method was slightly lower and more scattered than CO2 flux obtained by the eddy covariance method; however these values reasonably agreed. We made sure the flux observation system with gradient method worked properly.
The observed O3 concentrations at the two heights differed significantly; however the observed NOx concentrations at the two heights were similar and there were no significant differences, which indicated that it was difficult to obtain NOx fluxes with gradient method in the red pine forest. The primary result indicated that O3 deposition in the red pine forest in the day time (9:00-16:00) were -1.1±1.5 nmol m-2 s-1 in autumn 2014, and -1.9±2.5 nmol m-2 s-1 and 0.9±2.6 nmol m-2 s-1 in autumn and winter 2015. The O3 deposition in winter was smaller than in autumn, which was a similar trend with literature (Fares et al., 2010).
References:
Ollinger et.al., 2002, Global Change Biology 8, 545-562.
Fares et al., 2010, Agric For Meteorol. 150, 420-431.
The heights of the forest canopy and the meteorological tower were about 25 m and 32 m. Concentrations of O3, NOx and CO2 were measured at two heights (26 m and 32 m in 2014, 26 m and 34 m in 2015) above the canopy by an ultraviolet absorption O3 analyzer (Thermo: 49C), a chemiluminescence NOx analyzer (Thermo: 42iTL) and an infrared absorption CO2 analyzer (Licor: LI-820). The O3 instrument was calibrated before the observation, and the NOx and the CO2 instruments were calibrated every three weeks at the observation site. The air was sampled every 300 seconds from each two vertical heights and supplied to the analytical instruments through PFA tube. Concentration of CO2 was also measured by an infrared absorption CO2 analyzer (Licor: LI-6262) at 26.5 m to determine CO2 fluxes by the eddy covariance method. Wind speed and wind direction were measured at 26.5 m and they were used to obtain fluxes by the gradient and eddy covariance methods.
The CO2 fluxes in the day time (9:00-16:00) in the autumn of 2014 were observed with the gradient and the eddy covariance method as -9.0±7.3 mmol m-2 s-1 and -8.6±6.5 mmol m-2 s-1, respectively. The CO2 flux obtained by the gradient method was slightly lower and more scattered than CO2 flux obtained by the eddy covariance method; however these values reasonably agreed. We made sure the flux observation system with gradient method worked properly.
The observed O3 concentrations at the two heights differed significantly; however the observed NOx concentrations at the two heights were similar and there were no significant differences, which indicated that it was difficult to obtain NOx fluxes with gradient method in the red pine forest. The primary result indicated that O3 deposition in the red pine forest in the day time (9:00-16:00) were -1.1±1.5 nmol m-2 s-1 in autumn 2014, and -1.9±2.5 nmol m-2 s-1 and 0.9±2.6 nmol m-2 s-1 in autumn and winter 2015. The O3 deposition in winter was smaller than in autumn, which was a similar trend with literature (Fares et al., 2010).
References:
Ollinger et.al., 2002, Global Change Biology 8, 545-562.
Fares et al., 2010, Agric For Meteorol. 150, 420-431.