贵阳市燃煤烟气中汞在大气中传输的数值模拟

利用中尺度非静力大气化学模式(MESO-NHC)，以及目前大气中臭氧(O₃)和氢氧基(OH)对汞氧化的研究成果，研究贵阳市原煤燃烧产生的大气汞传输，以及φ(大气汞)对Hg0的干沉积速率,OH与元素汞(Hg0)的反应率常数的敏感性. 结果表明:①模拟区内实际大气中φ(Hg0)为局地人为排放源和自然排放源共同作用的结果，二者所占比例大致相当. ②由于化学和沉积特性不同，φ(Hg0)，φ〔Hg(Ⅱ)〕和φ(HgP)随着与排放源距离增加而衰减的程度存在差异，排放源对附近地区φ(大气汞)及各种形态汞所占比例影响较大；在远离排放源的地方，大气中的Hg(Ⅱ)和HgP主要来自于Hg0不断的氧化作用. ③φ(大气汞)表现出2种不同的垂直分布特征，在一定高度以下φ(Hg0)随高度线性递减，而在该高度之上直到对流层顶φ(Hg0)几乎保持同样的数值；φ〔Hg(Ⅱ)〕和φ(HgP)随高度的变化遵循指数递减规律. φ(Hg0)随高度和与排放源距离增加而衰减的程度不及φ〔Hg(Ⅱ)〕和φ(HgP)，主要是由于Hg0通过化学反应和沉积而离开大气的量少，能较充分通过平流扩散和垂直输送作用输送到离排放源较远和较高的地方. ④排放源附近φ(大气汞)较高的地方φ(大气汞)对Hg0的干沉积速率敏感性较高，而φ(大气汞)较低的地方其敏感性较低. ⑤φ(大气汞)对Hg0被OH氧化的反应率常数(k)的变化普遍很敏感，在较大的反应率常数kHg-OH3.55×10-14×e294/T情况下，Hg0所占比例偏低，而Hg(Ⅱ)和HgP所占比例偏高，与监测结果偏差较大；在kHg-OH2.94×10-14情况下模拟结果更为合理. 

Numerical Simulation of Mercury Transport and Sensitivity of Flue Gas from Coal Burning in Guiyang City

The meso-scale non-hydrostatics model (MESO-NHC) was used to simulate the transport of mercury from coal burning, and the sensitivity of mercury on dry deposition velocity of Hg0 and on rate constants of OH and Hg0 in Guiyang with recent research results of air mercury oxidation by O₃ and OH. The results show that: ①Anthropogenic and natural sources share the contribution to the actual air mercury concentrations in the simulated domain. ②The variations of chemistry and deposition of air mercury formations make the reductions of their concentration with the distance from the source different. The emission source is important to air mercury concentrations and their percentages. In areas far from the source, Hg(Ⅱ) and HgP come from the oxidation of Hg0. ③There were two different vertical profiles for Hg0 and for HgP and Hg(Ⅱ). Hg0 concentration was almost constant through the troposphere, and decreased linearly below a certain height. For HgP and Hg(Ⅱ), the concentrations reduce exponentially with height. The attenuation degree of Hg0 with height and distance from the emission source is inferior to that of Hg(Ⅱ) and HgP, mainly because less Hg0 leaves the atmosphere through chemical reaction and deposition, and can be sufficiently transported to farther and higher areas from an emission source through diffusion and vertical transport. ④Air mercury concentrations are sensitive to dry deposition velocity of Hg0 in places where air mercury concentrations are high near sources, and are not sensitive at places where air mercury concentrations are low.⑤Air mercury concentrations are very sensitive to the rate constant k of oxidation of Hg0 by OH generally. Under the condition of bigger rate constant kHg-OH3.55×10-14×e294/T, the percentage of Hg0 is on the low side, while the percentages of Hg(Ⅱ) and HgP are on the high side, which has a bigger discrepancy with the actual measurements. Under the condition of rate constant kHg-OH2.94×10-14, the simulation results are much more reasonable.