Snapshots of wintertime urban aerosol characteristics: Local sources emphasized in ultrafine particle number and lung deposited surface area.

Urban air fine particles are a major health-relating problem. However, it is not well understood how the health-relevant features of fine particles should be monitored. Limitations of PM2.5 (mass concentration of sub 2.5 µm particles), which is commonly used in the health effect estimations, have been recognized and, e.g., World Health Organization (WHO) has released good practice statements for particle number (PN) and black carbon (BC) concentrations (2021). In this study, a characterization of urban wintertime aerosol was done in three environments: a detached housing area with residential wood combustion, traffic-influenced streets in a city centre and near an airport. The particle characteristics varied significantly between the locations, resulting different average particle sizes causing lung deposited surface area (LDSA). Near the airport, departing planes had a major contribution on PN, and most particles were smaller than 10 nm, similarly as in the city centre. The high hourly mean PN (>20 000 1/cm3) stated in the WHO's good practices was clearly exceeded near the airport and in the city centre, even though traffic rates were reduced due to a SARS-CoV-2-related partial lockdown. In the residential area, wood combustion increased both BC and PM2.5, but also PN of sub 10 and 23 nm particles. The high concentrations of sub 10 nm particles in all the locations show the importance of the chosen lower size limit of PN measurement, e.g., WHO states that the lower limit should be 10 nm or smaller. Furthermore, due to ultrafine particle emissions, LDSA per unit PM2.5 was 1.4 and 2.4 times higher near the airport than in the city centre and the residential area, respectively, indicating that health effects of PM2.5 depend on urban environment as well as conditions, and emphasizing the importance of PN monitoring in terms of health effects related to local pollution sources.

Determination of atmospheric amines by on-fiber derivatization solid-phase microextraction with 2,3,4,5,6-pentafluorobenzyl chloroformate and 9-fluorenylmethoxycarbonyl chloride.

Alkylamines play an important role in atmospheric chemistry and are of concern for human health. Determining them from the vapor phase is challenging owing to their high polarity and volatility, water solubility, low concentrations, and poor chromatographic properties. We propose on-fiber derivatization solid-phase microextraction (SPME) to increase sensitivity and selectivity for the determination of alkylamines in air samples. SPME fibers coated in head-space with 2,3,4,5,6-pentafluorobenzyl chloroformate (PFBCF, 10min) or 9-fluorenylmethoxycarbonyl (FMOC) chloride (5min) were exposed to the sample for 5-120min, after which the derivatized alkylamines were thermally desorbed in the GC injection port and analyzed by GC-MS. The specific focus of the research was dimethylamine (DMA) but, as well as secondary amines, both coating agents readily react with primary and tertiary amines and with ammonia at ambient temperatures. The fiber coating procedures, sampling times, and analytical conditions were optimized, and methods were tested with natural samples. PFBCF was more selective and almost an order of magnitude more sensitive than FMOC chloride. Both reagents are applicable, however, depending on the requirements. With scan mode and use of molecular ion for quantification, the limit of quantification for DMA was 0.17µgL(-1) when derivatized with PFBCF and 3.4µgL(-1) when derivatized with FMOC chloride. When selected ion monitoring was used with the most abundant ion, the limit of quantification for DMA was 2.8ngL(-1). Intermediate reproducibility expressed as relative standard deviation was around 30% with PFBCF and less than 20% with FMOC chloride. Fibers coated with PFBCF could be used at least up to 24h when stored at 4°C and for 5 to 7h when stored at room temperature. After sampling/derivatization, storage time before analysis should not exceed 48h at 4°C or 24h at room temperature. At maximum, the PFBCF-coated fiber can be used in 100 coating/sampling/analysis cycles.

Solid phase microextraction Arrow for the sampling of volatile amines in wastewater and atmosphere.

A new method is introduced for the sampling of volatile low molecular weight alkylamines in ambient air and wastewater by utilizing a novel SPME Arrow system, which contains a larger volume of sorbent compared to a standard SPME fiber. Parameters affecting the extraction, such as coating material, need for preconcentration, sample volume, pH, stirring rate, salt addition, extraction time and temperature were carefully optimized. In addition, analysis conditions, including desorption temperature and time as well as gas chromatographic parameters, were optimized. Compared to conventional SPME fiber, the SPME Arrow had better robustness and sensitivity. Average intermediate reproducibility of the method expressed as relative standard deviation was 12% for dimethylamine and 14% for trimethylamine, and their limit of quantification 10µg/L and 0.13µg/L respectively. Working range was from limits of quantification to 500µg/L for dimethylamine and to 130µg/L for trimethylamine. Several alkylamines were qualitatively analyzed in real samples, while target compounds dimethyl- and trimethylamines were quantified. The concentrations in influent and effluent wastewater samples were almost the same (∼80µg/L for dimethylamine, 120µg/L for trimethylamine) meaning that amines pass the water purification process unchanged or they are produced at the same rate as they are removed. For the air samples, preconcentration with phosphoric acid coated denuder was required and the concentration of trimethylamine was found to be around 1ng/m(3). The developed method was compared with optimized method based on conventional SPME and advantages and disadvantages of both approaches are discussed.