Development And Primary Application Of Online VOCs Mass Spectrometry Underway Monitoring System

Volatile Organic Compounds（VOCs）are one of the main components of air pollution.VOCs pose a direct hazard to human health.Moreover,as a precursor of secondary aerosols,VOCs can form PM_2.5.5 through a series of chemical and physical reactions.Therefore,the detection of VOCs in the atmospheric environment has important research significance.The traditional VOCs detection method is to collect VOCs first and then transport them back to the laboratory for off-line analysis.Although this method can accurately detect VOCs,it has poor timeliness and low efficiency because the sample needs to be pre-treated and transported.Online time-of-flight mass spectrometry is widely used in real-time online detection of VOCs due to its high detection time resolution and multi-component simultaneous detection..The development of an on-line VOCs underway monitoring system was introduced in this paper,include the following（1）The design of the underway monitoring system;（2）The development of the application method of the underway monitoring system;（3）The application of the underway monitoring system.The system is based on time-of-flight mass spectrometry technology.The mobile monitoring vehicle is used as the carrier.It integrated the key equipment such as retractable atmospheric sampling tube,meteorological instrument,GPS,industrial computer,UPS,gas dilution device and so on.Through the above work,a set of high spatial-temporal resolution and high sensitivity underway monitoring system has been developed.The development of the underway monitoring application method mainly includes the performance test of the mass spectrometer,the development of the calibration method,and the development of the experimental method.The calibration method was mainly based on the EPA standard,using PAMS,TO-14 and organic sulfur compound standard gas as the main gases of calibration method.The experiment proved that there were 84 kinds of VOCs can be detected.It can be used to monitor most VOCs in atmospheric environment.The undway monitoring system monitors along the route in the target area,and establishes the pollution map of the whole area.According to the pollution map,the system quickly locks the key polluted areas.Then the system carries out detailed undway monitoring for the key polluted areas.It studies the spatial distribution,concentration and variation law of VOCs in the key areas,and finally locks the source of VOCs.The developed on-line VOCs underway monitoring system was applied in a high-tech zone in Guangdong.The underway monitoring area was 83.64km² and the VOCs distribution map of the whole area was established.Two key areas were found through the map,and the concentration,type,geographical distribution,peak concentration,and average concentration of the VOCs in the key areas were obtained.The average values of the total VOCs in the two key areas were 74 ug/m³⁴21 ug/m³ and 51 ug/m³⁵77ug/m³,lower than the relevant emission standards;the highest concentration values are 1302 ug/m³⁸010 ug/m³ and 358 ug/m³⁴4563 ug/m³.After analyzing the data of the two key areas,10 points with abnormal concentration were found.By analyzing the main components and geographical location of the abnormal points,the sources of the five abnormal points were finally found.The underway monitoring system can quickly screen VOCs pollution sources.In this study,an on-line VOCs cruise monitoring system based on time-of-flight mass spectrometry（TOFMS）technology was developed,which can be used to monitor VOCs pollution of whole area and to locate VOCs pollution sources at abnormal points,providing an effective technical means for rapid and efficient screening of pollution sources in the area.