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Gao N.,Tianjin University | Du Z.-H.,Tianjin University | Tang M.,Tianjin Environmental Monitoring Center | Yang J.-W.,Tianjin University | And 2 more authors.
Guang Pu Xue Yu Guang Pu Fen Xi/Spectroscopy and Spectral Analysis | Year: 2010

The system performance of tunable diode laser absorption spectroscopy (TDLAS) is affected by the modulation parameters such as modulation index, modulation frequency, scanning amplitude and scanning frequency. There is a lack of definite parameters selection basis in practical measurement. Aiming at this problem, the influence of modulation parameters on second harmonic signals was observed by experiment based on a certain theory in the present paper, and the basis and method of modulation parameters optimization for various system functions and demands were summarized by analyzing the signal characteristic including amplitude, signal to noise ratio, symmetry and peak width. For the system of concentration or temperature detection the amplitude and signal to noise ratio will be taken into prior consideration which require optimum modulation index, lower modulation frequency and lower scanning frequency. In condition of pressure detection deduced by lineshape the signal symmetry and peak width are more important to ascertain the modulation parameters according to practical demands. Scanning amplitude will be adjusted to obtain complete signal waveforms, then scanning frequency can be adjusted according to system speed and accuracy requirement. The result of the experiment provided a definite basis for conforming the working state of such system. Source

Li T.,Appraisal Center for Environment and Engineering | Wang H.,Tianjin Academy of Social science | Deng B.,Tianjin Environmental Monitoring Center | Ren W.,Oxford Brookes University | Xu H.,Nankai University
Environmental Impact Assessment Review | Year: 2016

Strategic Environmental Assessment (SEA) has been seen as a preventive and participatory environmental management tool designed to integrate environmental protection into the decision-making process. However, the debate about SEA performance and effectiveness has increased in recent decades. Two main challenges exist in relation to this issue. The first is identifying the key influencing factors that affect SEA effectiveness, and the second is analyzing the relationship between SEA and these influencing factors. In this study, influencing factors were investigated through questionnaire surveys in the Chinese context, and then a Structural Equation Model (SEM) was developed and tested to identify potential links and causal relationships among factors. The associations between the independent factors were divided into direct and indirect causal associations. The results indicate that the decision-making process and policy context directly affect SEA implementation, while information and data sharing, public participation, expertise and SEA institutions are indirectly related with SEA. The results also suggest that a lack of cooperation between different sectors is an obstacle to the implementation of SEA. These findings could potentially contribute to the future management and implementation of SEA or enhance existing knowledge of SEA. The results show that the proposed model has a degree of feasibility and applicability. © 2016 Elsevier Inc. Source

Chen L.,Tianjin Normal University | Han T.-T.,Nankai University | Li T.,Nankai University | Ji Y.-Q.,Nankai University | And 2 more authors.
Huanjing Kexue/Environmental Science | Year: 2012

Due to the lack of a prediction model for current wind erosion in China and the slow development for such models, this study aims to predict the wind erosion of soil and the dust emission and develop a prediction model for wind erosion in Tianjin by investigating the structure, parameter systems and the relationships among the parameter systems of the prediction models for wind erosion in typical areas, using the U.S. wind erosion prediction system (WEPS) as reference. Based on the remote sensing technique and the test data, a parameter system was established for the prediction model of wind erosion and dust emission, and a model was developed that was suitable for the prediction of wind erosion and dust emission in Tianjin. Tianjin was divided into 11080 blocks with a resolution of 1×1 km2, among which 7778 dust emitting blocks were selected. The parameters of the blocks were localized, including longitude, latitude, elevation and direction, etc.. The database files of blocks were localized, including wind file, climate file, soil file and management file. The weps.run file was edited. Based on Microsoft Visualstudio 2008, secondary development was done using C++ language, and the dust fluxes of 7778 blocks were estimated, including creep and saltation fluxes, suspension fluxes and PM10 fluxes. Based on the parameters of wind tunnel experiments in Inner Mongolia, the soil measurement data and climate data in suburbs of Tianjin, the wind erosion module, wind erosion fluxes, dust emission release modulus and dust release fluxes were calculated for the four seasons and the whole year in suburbs of Tianjin. In 2009, the total creep and saltation fluxes, suspension fluxes and PM10 fluxes in the suburbs of Tianjin were 2.54×106 t, 1.25×107 t and 9.04×105 t, respectively, among which, the parts pointing to the central district were 5.61×105 t, 2.89×106 t and 2.03×105 t, respectively. Source

Tang G.,CAS Institute of Atmospheric Physics | Wang Y.,CAS Institute of Atmospheric Physics | Li X.,CAS Institute of Atmospheric Physics | Ji D.,CAS Institute of Atmospheric Physics | And 2 more authors.
Atmospheric Chemistry and Physics | Year: 2012

The Project of Atmospheric Combined Pollution Monitoring over Beijing and its Surrounding Areas, was an intensive field campaign conducted over Northern China between June 2009 and August 2011 to provide a comprehensive record of ozone (O 3) and nitrogen oxides (NO x) and contribute to an in-depth understanding of air pollution in Northern China and its driving forces. In this campaign, 25 stations in an air-quality monitoring network provided regional-scale spatial coverage. In this study, we analyzed the data on O3 and NO x levels obtained at 22 sites (out of 25 sites due to data availability) over Northern China between 1 September 2009 and 31 August 2010. Our goal was to investigate the O 3 spatial-temporal variations and control strategy in this area. Significant diurnal and seasonal variations were noted, with the highest concentrations typically found at around 03:00 p.m. (local time) and in June. The lowest concentrations were generally found during early morning hours (around 06:00 a.m.) and in December. Compared with July and August, June has increased photochemical production due to decreased cloud cover coupled with reduced O3 loss due to less dry deposition, inducing an O 3 peak appearing in June. The averaged O 3 concentrations were lower in the plains area compared with the mountainous area due to the titration effects of high NO x emissions in urban areas. When the characteristics of O 3 pollution in different regions were distinguished by factor analysis, we found high levels of O 3 that exceeded China's National Standard throughout the plains, especially over Beijing and the surrounding areas. An integrated analysis with emissions data, meteorological data, and topography over Northern China found that the meteorological conditions were the main factors that dominated the spatial variations of O 3, with the presence of abundant emissions of precursors in this area. The smog production algorithm and space-based HCH O/NO 2 column ratio were used to show the O 3-NO x-VOC s sensitivity and examine the control strategy of O 3 over Northern China. The results show that summer O 3 production in the plains and northern mountainous areas was sensitive to VOC s and NOx, respectively. The presented results are intended to provide guidance for redefining government strategies to control the photochemical formation of air pollutants over Northern China and are relevant for developing urban agglomerations worldwide. © Author(s) 2012. CC Attribution 3.0 License. Source

Chen L.,Tianjin Normal University | Li T.,Nankai University | Han T.-T.,Nankai University | Ji Y.-Q.,Nankai University | And 2 more authors.
Zhongguo Huanjing Kexue/China Environmental Science | Year: 2012

Based on U.S. wind erosion prediction system (WEPS), secondary development of this model was done in order to estimate the effect of wind-blown dust came from suburban on air quality of central district. The database files of blocks were localized, including wind file, climate file, soil file and management file. The dust flux of each dusting block was estimated, including creep and saltation fluxes, suspension fluxes and PM 10 fluxes. In 2009, the maximum emission fluxes per block and emission fluxes occurred in winter. In winter, the creep and saltation fluxes, suspension fluxes and PM 10 fluxes pointing to central district were the most comparing to other seasons. In spring, emission fluxes mainly came from east, in summer, mainly came from west; in autumn, mainly came from west, and in winter, mainly came from north. In 2009, PM 10 fluxes came from north was 9.67×10 4 t, and accouted for 81.7% in winter. So, PM 10 came from northern suburban districts in winter affected deeply on the air quality of central district. Source

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