Declining ammonia emissions are not always reflected in ammonia concentrations due to physicochemical processes and meteorology. Here we present a trend analysis of reduced nitrogen components over the Netherlands using two different types of atmospheric transport models: the Eulerian grid model EMEP/MSC-W and the plume model OPS.

We employ calculations with the Eulerian grid model EMEP/MSC-W for the Netherlands in its EMEP4NL configuration. Using the Weather Research Forecast (WRF) model as meteorological driver plus detailed emission data over the Netherlands as input into the EMEP4NL model, we present simulation results over the Netherlands of reduced nitrogen components from this model at a horizontal resolution of 1.3 × 2.1 km.

Using this configuration of the EMEP/MSC-W model (EMEP4NL), a trend analysis is performed over the period 2006–2015 for concentration and deposition of reduced nitrogen components over the Netherlands. The same analysis is performed with the OPS-model, a plume model with a Lagrangian trajectory model for long range transport. Both models use the same MACC III emission distribution for countries outside of the Netherlands, and spatially more detailed emissions for the Netherlands itself. Emission totals per SNAP (Supporting National Action and Planning) sector per country are used over the period 2006–2015, according to the latest CEIP (Centre on Emissions Inventories and Projections) expert estimates. The OPS-model is driven with yearly specific meteorological fields provided by the Royal Netherlands Meteorological Institute (KNMI). Furthermore, the OPS-model parameterizes its chemistry, whereas EMEP4NL uses a state-of-the-art chemistry scheme.

Results from ammonia concentrations, ammonium concentrations and wet deposition as calculated with both models, are first compared with observations from the National Air Quality Monitoring Network in the Netherland (LML). Calculations of ammonia and wet deposition both agree well with the measurements in the OPS and the EMEP4NL model. Ammonium is better represented by calculations with the EMEP4NL model than by the OPS-model. Measurements of dry deposition of reduced nitrogen are very limited, therefore only a comparison is made between the model results of EMEP4NL and OPS.

Subsequently, a trend analysis is performed over the period 2006–2015 for the reduced nitrogen components for both model calculation results and the measurements. The trends of all components are calculated over the mean values of monitoring stations over the Netherlands. The reported decline in the emissions of ammonia is not reflected in the ammonia concentrations and wet deposition of reduced nitrogen as measured and calculated with the OPS and the EMEP4NL model. Ammonium concentrations on the other hand are declining (also) due to the decrease of the SO_x emissions over the period 2006–2015. Finally, both models show a slight decline in the dry deposition values, despite the fact that both models (and observations) do not show a decrease in the ammonia concentrations. A more detailed analysis of the comparison of dry deposition of reduced nitrogen between both models, and the influence of the physicochemical processes and meteorology is in preparation. Overall, it is found that the calculated trends for the different reduced nitrogen components with a grid model like EMEP4NL and a plume model like OPS are roughly in line with each other.

由于物理化学过程和气象学的原因，氨气排放量的下降并不总是反映在氨气浓度中。在这里，我们使用两种不同类型的大气传输模型：欧拉网格模型EMEP / MSC-W和羽流模型OPS，对荷兰减少的氮成分进行趋势分析。

我们在其EMEP4NL配置中使用荷兰的欧拉网格模型EMEP / MSC-W进行计算。使用气象研究预报（WRF）模型作为气象驱动因素，再加上荷兰的详细排放数据作为EMEP4NL模型的输入，我们以水平分辨率1.3×2.1 km给出了该模型在荷兰减少的氮成分的模拟结果。

使用EMEP / MSC-W模型（EMEP4NL）的这种配置，在2006-2015年期间进行了趋势分析，以分析荷兰各地还原氮成分的浓度和沉积。使用OPS模型执行相同的分析，这是一种具有拉格朗日轨迹模型的羽状模型，用于长距离运输。两种模型在荷兰以外的国家/地区使用相同的MACC III排放分布，并在荷兰本身使用空间更详细的排放。根据最新的CEIP（排放清单和预测中心）专家估计，每个国家SNAP（支持国家行动和计划）部门的排放总量在2006-2015年期间使用。OPS模型由荷兰皇家气象学院（KNMI）提供的年度特定气象领域驱动。此外，

首先将两种模型计算出的氨浓度，铵浓度和湿沉降的结果与荷兰国家空气质量监测网（LML）的观测结果进行比较。氨气和湿沉降的计算均与OPS和EMEP4NL模型中的测量值非常吻合。用EMEP4NL模型进行计算比用OPS模型更好地表示铵。还原氮干沉降的测量非常有限，因此仅在EMEP4NL和OPS的模型结果之间进行比较。

随后，针对模型计算结果和测量结果，对2006-2015年间减少的氮成分进行了趋势分析。所有组成部分的趋势均根据荷兰监测站的平均值计算得出。使用OPS和EMEP4NL模型进行测量和计算，所报告的氨气排放量的减少并未反映在氨气浓度和还原氮的湿沉降中。另一方面，由于SO _x的减少，铵浓度也在下降（也）2006-2015年的排放量。最后，尽管两个模型（和观测值）均未显示氨浓度降低，但两个模型均显示干沉降值略有下降。两种模型之间的还原氮干沉降比较的比较，以及理化过程和气象学的影响正在准备中。总体而言，发现使用网格模型（如EMEP4NL）和羽状模型（如OPS）计算出的不同还原氮组分的计算趋势大致一致。