Research On Detection Technique Of Marine Diesel Engine Unregulated Emissions

The dissertation focuses on systematically research of unregulated emissions produced by marine diesel engine.Enrichment materials and methods are key techniques that affected the accuracy of analysis. Sixteen EPA PAHs were selected as the object compounds. Aqueous-capture-collection (ACC),low-pressure-purge-and-trap (LPPT) and GC/MS were combined to solve the key problems in the detection of gaseous phase PAHs emitted from marine diesel engine, and invested a set of detection method. ACC method instead of the traditional solid adsorption method was used to trap gaseous PAHs.The functional additives of different properties were added into the solution, which could change the polarity of solution, synergistic effect, and increase the solubility of PAHs. The optimized concentration of hexadecyl trimethyl ammonium bromide (CTAB) was added firstly. Inorganic salt solution was added to eliminate emulsifications and organic solvent and sampling temperature was also tested to gradually improve the recovery of PAHs.Finally, recoveries achieved above76%. In order to solve the problem of low enrichment efficiency and poor recoveries of PAHs with boiling point higher than250℃, we modified a traditional purge-and-trap (P&T) system by introducing the pressure control system to form a LPPT system.Atmospheric pressure P&T and reformed LPPT system were compared. PAHs such as indeno[1,2,3,cd]pyrene, benzo[g,h,i]perylene and dibenz[a,h]anthracene rates improve significantly, from less than22%to more than81%.The linearity was good between peak area and concentration of PAHs at concentrations in the range of0.02-50)μg/L. The correlation coefficient of16PAHs was in the range of0.9981-0.9995.Blank recovery rates were in the range of81.5-98.5%.The PAHs limits of detection (LOD) were in the range of0.005-0.025μg/L. The limit of quantification (LOQ) was in the range of0.002-0.050μg/L. The LOD reached to nanogram grade, which realized trace analysis.The parallel comparison of the new method and the traditional method showed that the traditional method detected the total PAHs was232.481μg/kWh, and the result of new method was351.39μg/kWh. The new method was33.83%less than the loss rate of traditional method. The novel method for determination of PAHs costed less than30minutes from the samples collection to analysis, which saved90%time than the traditional method. The method solved the problems such as poor adsorption performance, low recovery rate, high loss rate and time consuming. The new method can realize fast, accurate, reliable and trace detection, which can effectively make the qualitative analysis and the quantitative detection of unconventional emissions. It can be promoted as one of standard methods for detection of unconventional emissions.Combining the established ACC method, nanomedium was modifed as the solid phase microextraction (μSPE) adsorption material. TiO2nanotube array was made in labortory, and modification conditions of cationic surfactant CTAB was explored as μSPE absorption material. New materials showed good performance in adsorption and desorption. Blank recoveries of16PAHs were ranged from83%to97.2%.The relative standard deviations (RSD) of the intra-day precision were ranged from3.7%to9.1%. The recovery rates were in the range of81-97%, and the RSD were in the range of1.13-8.75%. As the traditional enrichment methods have the problems such as low adsorption performance and low recovery rate, the method was simple and favorable popularization and application. In order to examine effects of different methods for extraction of particle matters (PM), several extraction methods were compared. Finally Soxhlet combining microwave extraction method was adopted for extraction of PAHs their derivatives. Through optimization of GC/MS method, effectively preseparation of nitro-PAHs in PM was used. Negative ion chemical ionization source was used for detection, and the LOD in the range of0.001-0.040μg/L. PAHs adsorbed in blank recoveries were in the range of82.5-98.5%. Repeatability RSD was in the range of0.239-8.786%. It was less than10%that illustrated high precision. Sample recovery rates of PAHs were in the range of78-98%and recoveries of nitro-PAHs in the range of79-95%that indicated the sample pretreatment process was not obvious polluted. The method can be applied to trace analysis of diesel PM. The results of this study not only useful for the research of generation mechanism, emission performance, emission toxicology and optimization of emissions properties, but also can recognize the dangers of unconventional emissions, and promote the formulation of the unconventional emission standards and related regulations, so as to protect environment for human survival and health.