危险化学品大气污染事故模拟

Simulation to an air pollution accident caused by the hazard chemicals

近年来国内突发性危险化学品大气污染事故频繁发生,为及时做出风险评估及救援决策,需要在事故初发阶段快速模拟确定其危害程度和范围。以东部沿海地区某一假想化工厂突发性泄漏事故为例,对其可能的危害范围进行模拟,采用WRF-CALMET模式模拟事故区域的高分辨率气象场,耦合随机模式模拟污染物的扩散过程。结果表明,WRF能精确地模拟1 km分辨率的近地面气象场的演变趋势。将该结果用于CALMET模式获得了高分辨率风场数据,再输入随机模式中进行扩散模拟,结果显示该模式能合理地模拟出污染物的危害范围及地面最高浓度。

The paper is aimed at introducing an air pollution modeling system for hazard chemicals accidents,in which,WRF is coupled with CALMET to simulate the high-resolution meteorological status-in-situ.For the purpose of simulation,we have taken a random walk model to simulate the pollutant diffusion situation in an imaginative coastal area of China East with a hypothetical leakage event taking place in a chemical plant over there.First of all,WRF has been adopted to imitate for the meteorological status in the accident area in a scale of four-layer nested grid from 27 km down to 1 km horizontal plane.Then,we have calculated and compared the simulated values of the four layers with the data measured at the meteorological stations of WMO statistically.In turn,we have worked out the WRF simulated data accurately,which has been increasing with the continuous improvement of the grid resolution.What is more,the accuracy tends to remain almost constant when the grid resolution is about 1 km in size.Secondly,the data gained in a grid resolution of 1 km under study is used as the input of CALMET,which was used to simulate for the meteorological field at 100 m-spatial resolution and 5min-temporal resolution.At the same time,the simulated wind direction should be close to the WRF＇s simulated one,though the grid resolution tends to be higher and therefore more applicable to the pollutant diffusion simulation.Moreover,we have also taken the wind field,the turbulent flow field and the planetary boundary layer of parameters from the CALMET simulation as the input of random walk model.And,then,we have successfully worked out the highest pollutant concentration every 5 min at the altitude of10 m up after the pollutant release in the risk area.Thus,the results of our simulation tend to demonstrate that the pollutants tend to diffuse mostly to the southwest,which is consistent with the wind field near the ground and the risk area turns to be growing gradually larger.Our simulated study also proves that the spread diffusion can be made steady with the highest concentration of 10 m remaining hardly being unchanged and approximately worked out as 0.093 9 g/m3.All the results show the random walk model with the WRF-CALMET can be trustable in reasonable simulation of the diffusion area trend whereas the risky area trace of the pollutants can serve as a certain guide for the risk assement and emergency treatment approach to the hazardous chemicals air accidents.