Field test of available methods to measure remotely SO2 and NOx emissions from ships

Methods for the determination of ship fuel sulphur content and NOx emission factors based on remote measurements have been compared in the harbour of Rotterdam and compared to direct stack emission measurements on the ferry Stena Hollandica. The methods were selected based on a review of the available literature on ship emission measurements. They were either optical (LIDAR, DOAS, UV camera), combined with model based estimates of fuel consumption, or based on the so called ‘sniffer’ principle, where SO2 or NOx emission factors are determined from simultaneous measurement of the increase of CO2 and SO2 or NOx concentrations in the plume of the ship compared to the background. The measurements were performed from stations at land, from a boat and from a helicopter. Mobile measurement platforms were found to have important advantages compared to the landbased ones because they allow to optimize the sampling conditions and to sample from ships on the open sea. Although optical methods can provide reliable results it was found that at the state of the art, the “sniffer” approach is the most convenient technique for determining both SO2 and NOx emission factors remotely. The average random error on the determination of SO2 emission factors comparing two identical instrumental set-ups was 6%. However, it was found that apparently minor differences in the instrumental characteristics, such as response time, could cause significant differences between the emission factors determined. Direct stack measurements showed that about 14% of the fuel sulphur content was not emitted as SO2. This was supported by the remote measurements and is in agreement with the results of other field studies.JRC.H.2-Air and Climat

Two instruments based on differential optical absorption spectroscopy (DOAS) to measure accurate ammonia concentrations in the atmosphere

We present two Differential Optical Absorption Spectroscopy (DOAS) instruments built at RIVM: the RIVM DOAS and the miniDOAS. Both instruments provide virtually interference-free measurements of NH3 concentrations in the atmosphere, since they measure over an open path, without suffering from inlet problems or interference problems by ammonium aerosols dissociating on tubes or filters. They measure concentrations up to at least 200 mu g m(-3), have a fast response, low maintenance demands, and a high up-time. The RIVM DOAS has a high accuracy of typically 0.15 mu g m(-3) for ammonia for 5-min averages and over a total light path of 100 m. The miniDOAS has been developed for application in measurement networks such as the Dutch National Air Quality Monitoring Network (LML). Compared to the RIVM DOAS it has a similar accuracy, but is significantly reduced in size, costs, and handling complexity. The RIVM DOAS and miniDOAS results showed excellent agreement (R-2 = 0.996) during a field measurement campaign in Vredepeel, the Netherlands. This measurement site is located in an agricultural area and is characterized by highly variable, but on average high ammonia concentrations in the air. The RIVM-DOAS and miniDOAS results were compared to the results of the AMOR instrument, a continuous-flow wet denuder system, which is currently used in the LML. Averaged over longer time spans of typically a day, the (mini) DOAS and AMOR results agree reasonably well, although an off-set of the AMOR values compared to the (mini) DOAS results exists. On short time scales, the (mini) DOAS shows a faster response and does not show the memory effects due to inlet tubing and transport of absorption fluids encountered by the AMOR. Due to its high accuracy, high uptime, low maintenance and its open path, the (mini) DOAS shows a good potential for flux measurements by using two (or more) systems in a gradient set-up and applying the aerodynamic gradient technique

Drift Corrected Trends and Periodic Variations in MIPAS IMK/IAA Ozone Measurements

Drifts, trends and periodic variations were calculated from monthly zonally averaged ozone profiles. The ozone profiles were derived from level-1b data of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) by means of the scientific level-2 processor run by the Karlsruhe Institute of Technology (KIT), Institute for Meteorology and Climate Research (IMK). All trend and drift analyses were performed using a multilinear parametric trend model which includes a linear term, several harmonics with period lengths from 3 to 24 months and the quasi-biennial oscillation (QBO). Drifts at 2-sigma significance level were mainly negative for ozone relative to Aura MLS and Odin OSIRIS and negative or near zero for most of the comparisons to lidar measurements. Lidar stations used here include those at Hohenpeissenberg (47.8° N, 11.0 ° E), Lauder (45.0 ° S, 169.7 ° E), Mauna Loa (19.5 ° N, 155.6 ° W), Observatoire Haute Provence (43.9 ° N, 5.7 ° E) and Table Mountain (34.4 ° N, 117.7 ° W). Drifts against the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) were found to be mostly insignificant. The assessed MIPAS ozone trends cover the time period of July 2002 to April 2012 and range from -0.56 ppmv decade-1 to +0.48 ppmv decade-1 (-0.52 ppmv decade-1 to +0.47 ppmv decade-1 when displayed on pressure coordinates) depending on altitude/ pressure and latitude. From the empirical drift analyses we conclude that the real ozone trends might be slightly more positive/ less negative than those calculated from the MIPAS data, by conceding the possibility of MIPAS having a very small (approximately within -0.3 ppmv decade-1 negative drift for ozone. This leads to drift-corrected trends of -0.41 ppmv decade-1 to +0.55 ppmv decade-1 (-0.38 ppmv decade-1 to +0.53 ppmv decade-1 when displayed on pressure coordinates) for the time period covered by MIPAS Envisat measurements, with very few negative and large areas of positive trends at mid-latitudes for both hemispheres around and above 30 km (similar to 10 hPa). Negative trends are found in the tropics around 25 and 35 km (similar to 25 and 5 hPa), while an area of positive trends is located right above the tropical tropopause. These findings are in good agreement with the recent literature. Differences of the trends compared with the recent literature could be explained by a possible shift of the subtropical mixing barriers. Results for the altitude-latitude distribution of amplitudes of the quasi-biennial, annual and the semi-annual oscillation are overall in very good agreement with recent findings

Atmospheric NO

From 12 to 28 September 2016, the CINDI-2 NO2 intercomparison campaign took place at the Cabauw research site in the Netherlands. Aimed principally at MAX-DOAS instruments, other techniques participated as well. The RIVM mobile lidar measured atmospheric NO2 profiles on six campaign days. Results show the development of NO2 concentrations during the day, as well as layered structures in the profiles. These were compared with profiles from other instruments

Atmospheric NO2 profiles measured with lidar during the CINDI-2 campaign

From 12 to 28 September 2016, the CINDI-2 NO2 intercomparison campaign took place at the Cabauw research site in the Netherlands. Aimed principally at MAX-DOAS instruments, other techniques participated as well. The RIVM mobile lidar measured atmospheric NO2 profiles on six campaign days. Results show the development of NO2 concentrations during the day, as well as layered structures in the profiles. These were compared with profiles from other instruments