A novel active personal nanoparticle sampler (PENS), which enables the collection of both respirable particulate mass (RPM) and nanoparticles (NPs) simultaneously, was developed to meet the critical demand for personal sampling of engineered nanomaterials (ENMs) in workplaces. The PENS consists of a respirable cyclone and a micro-orifice impactor with the cutoff aerodynamic diameter (d(pa50)) of 4 μm and 100 nm, respectively. The micro-orifice impactor has a fixed micro-orifice plate (137 nozzles of 55 μm in the inner diameter) and a rotating, silicone oil-coated Teflon filter substrate at 1 rpm to achieve a uniform particle deposition and avoid solid particle bounce. A final filter is used after the impactor to collect the NPs. Calibration results show that the d(pa50) of the respirable cyclone and the micro-orifice impactor are 3.92 ± 0.22 μm and 101.4 ± 0.1 nm, respectively. The d(pa50) at the loaded micro-Al(2)O(3) mass of 0.36-3.18 mg is shifted to 102.9-101.2 nm, respectively, while it is shifted to 98.9-97.8 nm at the loaded nano-TiO(2) mass of 0.92-1.78 mg, respectively. That is, the shift of d(pa50) due to solid particle loading is small if the PENS is not overloaded. Both NPs and RPM concentrations were found to agree well with those of the IOSH respirable cyclone and MOUDI. By using the present PENS, the collected samples can be further analyzed for chemical species concentrations besides gravimetric analysis to determine the actual exposure concentrations of ENMs in both RPM and NPs fractions in workplaces, which are often influenced by the background or incident pollution sources.

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A standard rotating drum with a modified sampling train (RD), a vortex shaker (VS), and a SSPD (small-scale powder disperser) were used to investigate the emission characteristics of nano-powders, including nano-titanium dioxide (nano-TiO 2 , primary diameter: 21 nm), nano-zinc oxide (nano-ZnO, primary diameter: 30-50 nm), and nano-silicon dioxide (nano-SiO 2 , primary diameter: 10-30 nm). A TSI SMPS (scanning mobility particle sizer), a TSI APS (aerodynamic particle sizer), and a MSP MOUDI (micro-orifice uniform deposit impactor) were used to measure the number and mass distributions of generated particles. Significant differences in specific number and mass concentration or distributions were found among different methods and nano-powders with the most specific number and mass concentration and the smallest particles being generated by the most energetic SSPD, followed by VS and RD. Near unimodal number or mass distributions were observed for the SSPD while bi-modal number or mass distributions existed for nano-powders except nano-SiO 2 which also exhibited bimodal mass distributions. The 30-min average results showed that the mass median aerodynamic diameter (MMAD) and number median diameter (NMD) of the SSPD ranged 1.1-2.1 lm and 166-261 nm, respectively, for all three nano-powders, which were smaller than those of the VS (MMAD: 3.3-6.0 lm and NMD: 156-462 nm), and the RD (MMAD: 5.2-11.2 lm and NMD: 198-479 nm). For nano-particles (electric mobility diameter \ 100 nm), specific mass concentrations were nearly negligible for all three nano-powders and test methods. Specific number concentrations of nano-particles were low for the RD tester but were elevated when more energetic VS and SSPD testers were used. The quantitative size and concentration data obtained in this study is useful to elucidate the field emission and personal exposure data in the future provided that particle loss in the generation system is carefully assessed.

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A novel multifilter PM 10 -PM 2.5 sampler (MFPPS) that enables the collection of four PM 10 and four PM 2.5 samples simultaneously has been developed and tested. The MFPPS uses a PM 10 impactor as the inlet and operates at 33.4 L/min. After the inlet, the aerosol flow is divided half by a Y-type fitting. Half of the flow is directed into four PM 10 filter cassettes, while the other half is directed into four PM 2.5 filter cassettes after the aerosols are further classified by a PM 2.5 impactor. An active flow control system consisting of two mass flow controllers (MFCs), one for PM 10 and the other for PM 2.5 , is used to fix the total flow rate of 16.7 L/min for four PM 10 or four PM 2.5 channels based on the ambient pressure and temperature. To ensure flow rate uniformity through each of the four PM 10 or four PM 2.5 filter cassettes, an orifice is assembled behind each of the filter cassettes to increase the pressure drop, such that the flow rates of eight sampling lines are nearly equal using just two MFCs. The MFPPS was calibrated in the laboratory for particle collection efficiency curves first. Then, the ambient PM concentrations were compared with those of other two collocated FRM samplers, the dichotomous PM 10 and the EPA WINS PM 2.5 sampler in the field study. Calibration results showed the cutoff aerodynamic diameters of the PM 10 and PM 2.5 impactors were 9.8 ± 0.1 and 2.5 ± 0.05 µm, respectively. Field comparison results indicated PM 10 and PM 2.5 concentrations agreed well with the other two PM samplers.

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