| 英文摘要 |
This project aims to monitor and inspect the concentration of vinyl chloride in the environmentally sensitive points near the offshore island industrial zone. It is continuously monitored by two gas chromatography/photoionization detectors, combined with multi-point stainless steel cylinder for sampling and detection. The plan, coupled with the unmanned aircraft's aerial sampling detection and analysis, is expected to understand the time and 3D spatial change of vinyl chloride concentration, and then clarify the "Xucuo public health incident" caused thiodiacetic acid (biological indicators, hereinafter referred to as TdGA), the high value of possible air pollutants, distributed through the air, is evidenced by the respiratory system being inhaled into the human body, and it can be used as a reference basis for subsequent relevant control.
The ground monitoring is divided into two parts. One is the continuous on-line monitoring of the gas chromatography/ photoionization detector installed in Fengan and Haifeng Elementary Schools. The instrument (with default) can be measured 9 volatile organic compounds; the measured concentrations are all below 55 ppb. As far as the trend is concerned, the emissions of vinyl chloride and butadiene mainly come from the industrial zone; the concentration trends of benzene, toluene, xylene and ethylbenzene are similar, and the sources of higher concentrations are from the eastward wind. In addition to the impact of the return flow from the area, there are also some contributions due to mobile pollution sources. In winter (as December), the concentration of the species at the downwind of the Haifeng site is higher than Fengan site. Investigating from the results of vinyl chloride monitoring conducted by different instruments on the perimeter of the industrial area over the years, the concentration of vinyl chloride measured in the area has shown the reduction, and there is no tendency to deteriorate. Monitoring in this year results at sensitive points of neighboring industrial areas and it shows that the concentration of vinyl chloride in the environment is low (as average concentration is 0.3 ppb).
The second part is the multi-point sub-grid inspection, which is carried out on the sampling and analysis of the selected 8 sensitive points. These compounds measured in this project include methanol, acetone and methylene chloride, among which methylene chloride concentration is inversely proportional to the distance from the industrial zone, and the closer to the industrial zone as the higher to the measurement. Sort out the test results of stainless steel canisters at environmentally sensitive points near the No.6 Naphtha Cracker Complex over the years. Compounds include propane, methanol, acetone, methyl ethyl ketone, and toluene, which can be measured regardless of the distance from No.6 Naphtha Cracker Complex; in the method of cylinder detection and analysis, no vinyl chloride value was found. Only low concentrations of vinyl chloride were measured on the roof of the vinyl chloride plant in the plant area (average concentration was measured 1.77 ppb).
The emission methods of harmful air pollutants are divided into two types: factory effusion and pipeline emissions. In addition to the monitoring (inspection) of nearby sensitive points, this project also uses drone for high-altitude sampling and analysis to understand whether are TdGA metabolic interference compounds, which may affect the perimeter environment of the plant through the stack emissions. During the two high-level sampling and analysis carried out during the project, no vinyl chloride and other related TdGA metabolic interference compounds were detected. The plan analyzes the trajectory of the airflow passing through the hexachloroethylene discharge port in the air mass trajectory mode (FYTRAJ) on the same day. Two results show that the smog flow passes through the ground sampling point, and the measured values and concentration of volatile organic compounds are both higher than other measuring points.
The meteorological conditions of the mixed layer are important factors affecting the diffusion of pollutants. This project uses aircraft and meteorological observation instruments for observation, and BC and ozone sensors to understand whether to stratification over the industrial area. During the project implementation period from November 13, 2019 to December 31, 2019, the prevailing wind direction is north-north-east wind, with an average wind speed of 5.60 m/s, which belongs to the northeast monsoon pattern used in high-altitude of aircraft. After observing and selecting the typhoon away from this project, the atmospheric isobaric evacuation and low wind speed weather patterns were sampled at high altitude from November 23 to 24, 2019. Observation results show that within the maximum height (639 meters), there is no obvious stratification in the atmosphere. The height of the surface boundary layer during the observation period is distributed between 40 and 100 m, which also shows that if the inverse trajectory air mass model is used to estimate the source of the air mass in this area, the assumptions in this range are representative. Observation results of pollutants show that ozone and black carbon concentrations have not measured high concentration changes, and ozone is generally the lowest when it is close to the surface, and it increases to the highest concentration of each observation as the altitude rises; it may be caused by dry sedimentation or ground surface Ozone titration reaction (O3+NO→NO2+O2), but atmospheric conditions are not a typical case-the mixing process is not uniform, which causes the lowest ground concentration to increase with increasing altitude. In addition, the concentration of black carbon is higher on the ground or at a height of 500 meters, indicating that there may be sources of black carbon emissions on the ground and high altitude.
Through high-altitude observation and inverse trajectory of the air mass, it is shown that the air mass that reached the observation site on the south side of the industrial zone during this monitoring period is because the northern offshore industrial zone passed through the industrial zone and then reached the observation site. There was no impact on nearby schools along the way. The reason is speculated that this observation is due to the winter period. In this season, the characteristic wind direction is mainly north wind, and the adjacent school is located on the east side of the industrial zone, so it is not affected by the industrial area.
For this year's monitoring and integration, the concentration of vinyl chloride in the atmospheric environment investigated in recent years has not exceeded the regulations and carcinogenic standards. In addition, the research found a high value of the biological index TdGA, which is not a specific biological index of vinyl chloride. Other air pollutants such as ethylene oxide, smoking or vitamin intake, and other common factors in life also make the body metabolize TdGA, but all need further investigation to confirm. According to the survey results of the local atmospheric environment of vinyl chloride in the past years and the monitoring results of this project, the concentration of vinyl chloride in the industrial zone's perimeter environment is lower than the concentration standards of the current regulations. So it is speculated that it is not the reason for the high TdGA value of Xucuo school children.
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