ntly contributing approximately forty-five to sixty percent of the NOxemissions and about eighty-five percent of the CO emissions in typical Chinese cities.8Recent data collected in Shanghai ，for example，show that in 1996，vehiclesemitted eighty-six percent of the CO，fifty-six percent of the NOx ，and ninety-sixpercent of the non-methane hydrocarbons （NMHC）of the total air pollution loadin the downtown area.9In Beijing in recent years ，the NOx concentration showsa clear increasing trend.Annual average NOx concentrations ，average concentrationsduring the heating season ，and those during the non-heating season in 1997were133mg/m3，191mg/m3，and 99mg/m3，respectively.These emissions were seventy-threepercent ，sixty-six percent，and eighty percent higher than those ten years ago.The annual daily average NOx concentration in 1998was 14.3percent higher thanin 1997.Since the amount of coal burned has remained stable for many years ，Beijinglocal authorities attribute the increases in these pollutants to vehicular emissions.10Poor vehicle maintenance is one leading cause of mobile source pollution problems.This deficiency in vehicle maintenance is reflected in the high failure rate inthe existing，relatively lenient Inspection and Maintenance（I/M ）programs.Poortraining of inspectors has meant repair workers lack the necessary professionalknow
LEDge and expertise in repair and maintenance service of emission equipment.11Many vehicles seem to be operating with a rich air fuel mixture，which whileproducing relatively good drivability and low NOx emissions ，leads to high fuelconsumption and excessive CO and HC emissions.Furthermore，the vehicle technologybeing produced tends to be primarily carburetor-equipped with mechanical ratherthan electronic controls.Recently collected emissions data in China show that currentvehicles are typical of the cars used in the United States in the late 1960/ear
上一页 [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] ... 下一页 >>
特别声明：本站除部分特别声明禁止转载的专稿外的其他文章可以自由转载，但请务必注明出处和原始作者。文章版权归文章原始作者所有。对于被本站转载文章的个人和网站，我们表示深深的谢意。如果本站转载的文章有版权问题请联系编辑人员，我们尽快予以更正。本站所有技术文章、专业软件资料仅供技术人员、高校师生学习交流之用，目的旨在促进与提高中国的交通技术水平；用户获取后不得用于商业目的，否则，所产生的法律责任本站概不负责。
