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Naneum instruments

Nano-ID NPS 500


The Nano-ID NPS500 sets a new standard for high sensitivity and selectivity aerosol measurements. It provides the ability to measure particle size distributions over a range of 5 nm to 500 nm with 128 user-selectable channels. Read More

Nano-ID Select

The Nano-ID Select is a wide-range sampler and is unique in that it spans the entire aerosol range from 2 nm up to 20 μm. Read More

 

 


Welding facility in USA

Airborne particles in the size range from 2nm to 30μm were sampled using the Nano-ID Select at a flow rate of 20 l/min at a welding facility in the USA.  Particles fractionated into sizes according to 12 separate size “bins”. By analyzing the amount of substance of interest in each of the size bins it was possible to derive the mass size distribution over the entire aerosol particle size range. Chemical analysis of the samples was carried out using ICP to identify the size distributions of various materials.

Figure 3.1 shows an aerosol mass size distribution, fa(D), of Zn sampled at a welding facility in 2008. The distribution has a broad mode in the micron size range and a large maximum centred at 10 nm. The majority of the Zn mass (82%) is found to be in the nano range. The nano range mode is centred at about 10 nm. A wider mode or possibly two modes are located at the sub-micron and micron ranges.  The total mass concentration of Zn in the air is 2,020ng/m3, which is much lower than the mass concentration of atmospheric background aerosol particles.

Table I: Equivalent mass concentrations of materials in the air and deposited in the respiratory tract according to various metrics and the TSP for the background aerosol.

 

Material

Aerosol particle mass concentration, ng/m3

Total in the air, mta

In the respiratory tract, mtd

Alveolar and TB regions

PM10

Respirable fraction, PM4

Al

1,390

793

150

985

830

Cr

48

30

12

39

39

Fe

252

150

46

192

190

Zn

2,020

1,550

870

1,870

1,820

Figure 3.1: Zn aerosol particle mass size distributions dm/dLogD in ng/m3 measured at a welding facility in the USA. White bars represent aerosol in the air, grey bars represent size distribution corresponding to particles deposited in the entire respiratory system, and dark bars represent the size distribution corresponding to particles deposited in the alveolar and trachea bronchial range.

Figure 3.2 shows an aerosol mass size distribution fa(D) of Al sampled in the same welding site. The distribution has a broad mode in the micron size range and a small maximum centred at ~3 nm. This is a typical multi-modal distribution similar to the results observed earlier for lead in the work place (Gorbunov et al., 2009). The total amount of Al in the nano-range (D<100nm) is about 3%. The total mass concentration of Al in the air is 1,390ng/m3, much lower than the mass concentration of background aerosol particles (20,000-100,000ng/m3).

These are typical size distributions obtained over the full size range. The distributions exhibit three main features: 1. the majority of the distributions are bi-modal and have a distinct mode in the nano-range, 2. the mass fraction of nanoparticles (1nm<D<100nm) ranges from 3 to 80% w/w, and 3. the total mass of substances of interest is often much lower than the total mass of atmospheric background aerosol.

Figure 3.2: Al aerosol particle mass size distributions dm/dLogD in ng/m3 obtained at the welding facility. White bars represent aerosol in the air, grey bars represent size distribution corresponding to particles deposited in the entire respiratory system, and dark bars represent the size distribution corresponding to particles deposited in the alveolar and trachea bronchial range.

References:
Gorbunov B., N. D. Priest, R. B. Muir, P. R. Jackson and H. Gnewuch  (2009) A Novel Size-Selective Airborne Particle Size Fractionating Instrument for Health Risk Evaluation. Ann. Occup. Hyg., Vol. 53, No. 3, pp. 225–237.
Acknowledgement: Dr D. Belo for supplying the size distributions.

 
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