Aliphatic amines in the tropical marine environment: Sources, budgets and phase partitioning phase II
Analytical Chemistry
Final Report Abstract
Within the DFG project ALAMARE II, the role of sub micrometer low molecular aliphatic amines in the tropical marine environment was investigated in detail. An analytical method for the qualitative and quantitative analysis of the amines has been conducted in cooperation with the research group of M. Fitzsimons at the University of Plymouth, UK. A novel extraction method (SPME) combined with GC-NPD was successfully applied and allowed a robust determination of the amines in trace levels. This led to the determination of amines in high saline complex matrices such as Atlantic seawater. The analysis of SML and bulk water samples from previous campaigns showed that concentrations of the amines were in the nmol/L range and they seems to be enriched in the SML. The data are well in agreement with other seawater measurements of amines (e.g. van Pinxteren et al. 2012). Perspectively we plan to apply the method to samples from a planned campaign at the CVAO where we will carefully adopt all necessary sample preparation steps (e.g. immediately filtering and acidifying of the samples). A comprehensive data interpretation of amines on aerosol particles revealed, that the amines are not directly correlated to distinct sources. As a qualitative tool to distinguish between different sources of the amines, a statistical source apportionment approach (principal component analysis, PCA) was applied to the data set. Three factors could be extracted from the statistical analysis: sea spray, photochemical production and a third factor that seemed to be correlated to calm, sunny weather and warm temperatures, but could not be clearly be attributed to one distinct source or formation mechanism. Especially this third factor will be elucidated in more detail in future studies. Furthermore, DMA and DEA seemed to be of the same origin (mainly factor 3), whereas MA is anti-correlated with factor 3. Finally, from the concentrations of dimethylamine in seawater and in the gas phase (together with wind speed data) mass fluxes between sea and air were calculated and varied between 1.6E-12 and -3.2E-12 mol m^-2 s^-1. This suggests that the ocean can act as sink (negative flux) or source (positive flux) for amines. It is likely that the source/sink capabilities of the ocean vary due to different ambient conditions e.g. a diurnal oxidation capacity of the atmosphere. To further investigate air-sea exchange of the amines, (atmospheric) measurements with a high special resolution and diurnal investigation of the amines in the gaseous phase as well as in the aerosol phase are required.
