CEM - Abstract

Abstract Information :

Ship emissions of particles, SO2 and NOx (the sum of NO and NO2) are a significant contribution to air pollution, in particular in coastal areas and close to busy in-land shipping routes. Therefore, national and international regulations have been put in place to limit emissions and thereby minimize the impact of shipping on air quality. However, the monitoring of ship emissions is challenging, and so far, no automated systems are operational for systematic surveillance of compliance with regulations. Active Optical Remote Sensing is one possible approach to measuring ship emissions. Briefly, a light source is set-up on one side of a river or port, and a reflector on the other side. The light path is positioned in such a way that the emission plume of passing ships is sampled. Using spectroscopic methods, the amounts of trace gases in the plume can be determined. With Automated Identification System (AIS) data, the plumes can be assigned to individual ships. The advantage of remote sensing over in-situ observations is a reduced dependence on wind direction, increasing the rate of successful measurements. A second important advantage is the self-calibration of the method, facilitating long-term autonomous operation without the need for on-site calibration. Using a long-path Differential Optical Absorption Spectroscopy (DOAS) system, more than one year of measurements were performed at the location of Wedel, a small town at the river Elbe, 10 km downriver of the port of Hamburg, Germany. The instrument measured SO2, NO2 and O3 in the plumes of more than 7400 passing ships. Based on these data and a plume model, emission rates of NOx and SO2 in g s-1 could be determined with an automated method. While this type of measurement is useful in determining emission rates, often specific emissions relative to the amount of fuel burnt are of interest. This is particularly the case for SO2, where regulations are based on limits for the fuel sulphur content. In order to extend the method to these quantities, an additional channel measuring CO2 in the IR part of the spectrum has to be added to the instrument. The CO2 can be used as a proxy of the amount of fuel burnt, and thereby also the energy used. In addition, direct NO measurements in the IR would reduce the uncertainties of the NOx measurements. The SEICOR project aims at developing such a system for automated long-term surveillance of emissions from ships and other, similar sources. It is based on the experience and tools from the measurements performed in Wedel. The new system will cover all parts of the measurements, from the instrument over data analysis of the emission factors to direct generation of warnings in case of high emissions. An automated reporting to the authorities, port operators and / or ship owners is planned. This work was supported by the University of Bremen, the by the German Federal Maritime and Hydrographic Agency and the Federal Ministry for economic affairs and climate action.