Ammonia (${\mathrm{NH}}_3$) is an important atmospheric pollutant and despite significant management efforts, trends of ${\mathrm{NH}}_3$ concentrations have not shown progressive decreases over the last few decades across much of Europe. To investigate this issue, long-term ${\mathrm{NH}}_3$ concentrations from passive sampling tubes were analysed at 32 locations across Switzerland and Liechtenstein. A trend analysis controlling for changes in meteorology employing generalised additive models (GAMs) between 2000 and 2021 showed that 29 of the 32 (91 %) sites experienced no significant change or increasing ${\mathrm{NH}}_3$ concentrations with the greatest trend being 0.17 $\mathrm{\mu g}{\mathrm{m}}^{-3}{\mathrm{y}}^{-1}$. These results conflict with an indicated 13 % reduction in ${\mathrm{NH}}_3$ emissions from the Swiss emission inventory. The sensitivity of the ${\mathrm{NH}}_3$ -ammonium (${\mathrm{NH}}_4^{+}$) system to reductions of ${\mathrm{NH}}_3$ ‘s acidic sinks (mostly in the form of nitric and sulfuric acids) was investigated with thermodynamic equilibrium modelling to explain this disconnect. The simulations indicated that the reductions in ${\mathrm{NH}}_3$ ‘s acidic sinks resulted in less ${\mathrm{NH}}_4^{+}$ transformation, thus increasing the ${\mathrm{NH}}_3$/${\mathrm{NH}}_{\mathrm{x}}$ ratio and this process has compensated for the reduction in ${\mathrm{NH}}_3$ emissions. The average effect of the sink reductions was an increase of 0.9 $\mathrm{\mu g}{\mathrm{m}}^{-3}$ in ${\mathrm{NH}}_3$ between 2004 and 2021. Increases in the ${\mathrm{NH}}_3$/${\mathrm{NH}}_{\mathrm{x}}$ ratio have likely occurred in many European countries due to reductions of acidic precursor emissions and will have consequences for reactive nitrogen deposition and alter import-export budgets among neighbouring regions and countries.

氨（${\mathrm{NH}}_3$）是一种重要的大气污染物，尽管做出了巨大的管理努力，但${\mathrm{NH}}_3$过去几十年来，欧洲大部分地区的浓度并未出现逐步下降的情况。为了研究这个问题，需要长期${\mathrm{NH}}_3$对瑞士和列支敦士登 32 个地点的被动采样管的浓度进行了分析。采用广义加性模型 (GAM) 控制 2000 年至 2021 年间气象变化的趋势分析表明，32 个站点中有 29 个 (91%) 没有经历显着变化或增加${\mathrm{NH}}_3$最大趋势为 0.17 的浓度$\mathrm{微克}{\mathrm{米}}^{-3}{\mathrm{y}}^{-1}$。这些结果与 13% 的减少相冲突${\mathrm{NH}}_3$瑞士排放清单中的排放量。的灵敏度${\mathrm{NH}}_3$-铵（${\mathrm{NH}}_4^{+}$）系统减少${\mathrm{NH}}_3$通过热力学平衡模型研究了酸性汇（主要以硝酸和硫酸的形式），以解释这种脱节。模拟表明，减少${\mathrm{NH}}_3$的酸性水槽导致减少${\mathrm{NH}}_4^{+}$转变，从而增加${\mathrm{NH}}_3$/${\mathrm{NH}}_{\mathrm{X}}$比率，并且该过程补偿了${\mathrm{NH}}_3$排放。汇减少的平均效果增加了 0.9$\mathrm{微克}{\mathrm{米}}^{-3}$在${\mathrm{NH}}_3$2004 年至 2021 年间。${\mathrm{NH}}_3$/${\mathrm{NH}}_{\mathrm{X}}$由于酸性前体排放量的减少，许多欧洲国家可能出现了这种情况，并将对活性氮沉积产生影响，并改变邻近地区和国家之间的进出口预算。