An optical hydrogen sulfide(H_2S) sensor based on wavelength modulation spectroscopy with the second harmonic(2f) corrected by the first harmonic(1f) signal(WMS-2f/1f) is developed using a distributed feedback(DFB) la...An optical hydrogen sulfide(H_2S) sensor based on wavelength modulation spectroscopy with the second harmonic(2f) corrected by the first harmonic(1f) signal(WMS-2f/1f) is developed using a distributed feedback(DFB) laser emitting at 1.578 μm and a homemade gas cell with 1-m-long optical path length. The novel sensor is constructed by an electrical cabinet and an optical reflecting and receiving end. The DFB laser is employed for targeting a strong H_2S line at 6 336.62 cm^(-1) in the fundamental absorption band of H_2S. The sensor performance, including the minimum detection limit and the stability, can be improved by reducing the laser intensity drift and common mode noise by means of the WMS-2f/1f technique. The experimental results indicate that the linearity and response time of the sensor are 0.999 26 and 6 s(in concentration range of 15.2—45.6 mg/m^3), respectively. The maximum relative deviation for continuous detection(60 min) of 30.4 mg/m^3 H_2S is 0.48% and the minimum detection limit obtained by Allan variance is 79 μg/m^3 with optimal integration time of 32 s. The optical H_2S sensor can be applied to environmental monitoring and industrial production, and it has significance for real-time online detection in many fields.展开更多
This study aimed to investigate the effect of economic growth, agricultural growth and energy use on methane (CH<sub>4</sub>) and nitrous oxide (N<sub>2</sub>O) emissions in Sudan. Within the c...This study aimed to investigate the effect of economic growth, agricultural growth and energy use on methane (CH<sub>4</sub>) and nitrous oxide (N<sub>2</sub>O) emissions in Sudan. Within the context of the EKC, the study applies the OLS, cointegration, vector error correction modelling (VECM) and Granger causality methods. The study has established a long run equilibrium relationship for both CH<sub>4</sub> and N<sub>2</sub>O in their relation to economic growth, agricultural growth and energy use in presence of trade openness (TOP) and inflows of foreign direct investments (FDI). The estimated VECM shows that emissions of CH<sub>4</sub> are significantly affected by economic growth, TOP, and FDI with no effect of agricultural growth in the short run while CH<sub>4</sub> is found to be significantly affected by economic growth, agricultural growth, TOP and FDI in the long run. The estimated VECM for N<sub>2</sub>O shows that N<sub>2</sub>O emissions are more significantly affected by energy use, agricultural growth and FDI with no effect of economic growth in the short run, while N<sub>2</sub>O is found to be significantly affected by economic growth, agricultural growth, TOP and FDI in the long run. Consistently, findings from the estimated OLS and VECMs show that the EKC does not hold for either CH<sub>4</sub>, or N<sub>2</sub>O emissions, and that N<sub>2</sub>O emissions are more significantly affected by economic growth, agricultural growth and energy use than emissions of CH<sub>4</sub>. Findings from impulse response and variance decomposition analysis confirm that emissions of N<sub>2</sub>O are more responsive to economic growth, agricultural growth and energy use than emissions of CH<sub>4</sub>. Granger causality analysis shows existence of bidirectional relationship between CH<sub>4</sub> and agricultural growth, but a unidirectional relationship from CH<sub>4</sub> to FDI. For N<sub>2</sub>O, the study finds a unidirectional relationship running from agricultural growth to N<sub>2</sub>O, while N<sub>2</sub>O emissions are found to cause GDP per capita, the squared GDP per capita, OIL consumption and FDI. In terms of causality, these results suggest that emissions of CH<sub>4</sub> and N<sub>2</sub>O have been generated more by agricultural activities than by overall economic activity, and that activities generating N<sub>2</sub>O emissions in particular have been contributing significantly to economic growth. Within the context of the country’s intended nationally determined contributions, the findings of this study suggest that policies should be directed cautiously but more effectively to control N<sub>2</sub>O than CH<sub>4</sub> emissions. Economic growth could be pursued without significant environmental harm from both CH<sub>4</sub> and N<sub>2</sub>O emissions. However, Sudan should expand adoption of energy efficiency measures, expansion of renewable energy use, place restrictions on production and use of fuel woods and charcoal for low carbon economy and green growth.展开更多
基金supported by the National Natural Science Foundation of China(Nos.60808020 and 61078041)the Natural Science Foundation of Tianjin(Nos.16JCQNJC02100,15JCYBJC51700 and 16JCYBJC15400)the National Science and Technology Support(No.2014BAH03F01)
文摘An optical hydrogen sulfide(H_2S) sensor based on wavelength modulation spectroscopy with the second harmonic(2f) corrected by the first harmonic(1f) signal(WMS-2f/1f) is developed using a distributed feedback(DFB) laser emitting at 1.578 μm and a homemade gas cell with 1-m-long optical path length. The novel sensor is constructed by an electrical cabinet and an optical reflecting and receiving end. The DFB laser is employed for targeting a strong H_2S line at 6 336.62 cm^(-1) in the fundamental absorption band of H_2S. The sensor performance, including the minimum detection limit and the stability, can be improved by reducing the laser intensity drift and common mode noise by means of the WMS-2f/1f technique. The experimental results indicate that the linearity and response time of the sensor are 0.999 26 and 6 s(in concentration range of 15.2—45.6 mg/m^3), respectively. The maximum relative deviation for continuous detection(60 min) of 30.4 mg/m^3 H_2S is 0.48% and the minimum detection limit obtained by Allan variance is 79 μg/m^3 with optimal integration time of 32 s. The optical H_2S sensor can be applied to environmental monitoring and industrial production, and it has significance for real-time online detection in many fields.
文摘This study aimed to investigate the effect of economic growth, agricultural growth and energy use on methane (CH<sub>4</sub>) and nitrous oxide (N<sub>2</sub>O) emissions in Sudan. Within the context of the EKC, the study applies the OLS, cointegration, vector error correction modelling (VECM) and Granger causality methods. The study has established a long run equilibrium relationship for both CH<sub>4</sub> and N<sub>2</sub>O in their relation to economic growth, agricultural growth and energy use in presence of trade openness (TOP) and inflows of foreign direct investments (FDI). The estimated VECM shows that emissions of CH<sub>4</sub> are significantly affected by economic growth, TOP, and FDI with no effect of agricultural growth in the short run while CH<sub>4</sub> is found to be significantly affected by economic growth, agricultural growth, TOP and FDI in the long run. The estimated VECM for N<sub>2</sub>O shows that N<sub>2</sub>O emissions are more significantly affected by energy use, agricultural growth and FDI with no effect of economic growth in the short run, while N<sub>2</sub>O is found to be significantly affected by economic growth, agricultural growth, TOP and FDI in the long run. Consistently, findings from the estimated OLS and VECMs show that the EKC does not hold for either CH<sub>4</sub>, or N<sub>2</sub>O emissions, and that N<sub>2</sub>O emissions are more significantly affected by economic growth, agricultural growth and energy use than emissions of CH<sub>4</sub>. Findings from impulse response and variance decomposition analysis confirm that emissions of N<sub>2</sub>O are more responsive to economic growth, agricultural growth and energy use than emissions of CH<sub>4</sub>. Granger causality analysis shows existence of bidirectional relationship between CH<sub>4</sub> and agricultural growth, but a unidirectional relationship from CH<sub>4</sub> to FDI. For N<sub>2</sub>O, the study finds a unidirectional relationship running from agricultural growth to N<sub>2</sub>O, while N<sub>2</sub>O emissions are found to cause GDP per capita, the squared GDP per capita, OIL consumption and FDI. In terms of causality, these results suggest that emissions of CH<sub>4</sub> and N<sub>2</sub>O have been generated more by agricultural activities than by overall economic activity, and that activities generating N<sub>2</sub>O emissions in particular have been contributing significantly to economic growth. Within the context of the country’s intended nationally determined contributions, the findings of this study suggest that policies should be directed cautiously but more effectively to control N<sub>2</sub>O than CH<sub>4</sub> emissions. Economic growth could be pursued without significant environmental harm from both CH<sub>4</sub> and N<sub>2</sub>O emissions. However, Sudan should expand adoption of energy efficiency measures, expansion of renewable energy use, place restrictions on production and use of fuel woods and charcoal for low carbon economy and green growth.
