Measurements of ship emissions using in-situ and LP-DOAS instruments

Abstract

Ships are an important source of pollutants along busy waterways. Depending on the type of ship, sea going or inland vessel, different key pollutants are emitted. In all cases, ships equipped with combustion engines are strong emitters of NOx (NO + NO2) and other pollutants emitted by combustion processes. Additionally, sea going ships are also strong emitters of SO2. Generally, NOx and SO2 are key parameters of air quality. These pollutants can be monitored by different kinds of instruments, e.g. in-situ instruments and remote sensing instruments.

In the first part of this thesis, the capabilities of active remote sensing to monitor ship emissions will be presented. A LP-DOAS instrument specifically designed by the company Airyx to monitor ship emissions will be presented and compared to a scientific LP-DOAS instrument. To highlight the opportunities offered by LP-DOAS measurements for the monitoring of ship emissions, one year of LP-DOAS measurements made across the river Elbe close to Hamburg are evaluated. Elevated concentrations of NO2 and SO2 are assigned to individual ship passages and a method to derive emission rates of SO2, NO2, and NOx using a Gaussian plume model is presented. More than 7000 individual ship passages have been monitored and their respective emission rates have been derived. The emission rates have been analysed in the context of ship type (inland or sea going), length, and speed over ground. The emission rates were compared to emission factors from previous studies and show good agreement.

In the second part, ship emission rates of individual inland vessels are derived from several years of measurement in the lower Rhine area, specifically in Duisburg and Neuss. The emission rates were derived from on-shore in-situ measurements using an improved version of the algorithm presented in the first part. Elevated concentrations of NOx were assigned to the corresponding source ships and each ship passage was simulated a Gaussian-puff model to derive the NOx emission rate of the respective source ship. In total over 32900 ship passages have been monitored in a time frame of four years of measurement. The emission rates were analysed in the context of the ship size, ship speed over ground, ship speed in water, and direction of travel. Comparison of on-board and on-shore emission rates for selected ships participating in the EU Life project CLINSH showed good agreement between both methods. The derived emission rates also agree with emission factors from previous studies. In most cases, the ships comply with emission regulations.