# Presentation: 513963

## Diffusive Air Sampler Constructed fromUsed Plastic Bottles for NO2 Determination

- W. Somboon, E. Chokasut, and S. Kiatsiriphairoj
- Dept. of Chemistry, Faculty of Science,
- King Mongkut’s Univ. of Technology Thonburi

## Ambient Air Quality Study

- Air samplings
- 	- Active samplings
- 	- Passive samplings
- Lab measurements

##  Active air samplings
	   Air suction (Pumping) and storage/absorbed

 Passive sampling
  Diffusion of air and absorbed/reaction

- 	   Air suction (Pumping) and storage/absorbed
-  Passive sampling
-   Diffusion of air and absorbed/reaction

- Ambient Air Quality Study

## Advantages/disadvantages
 Active sampling
	   High accuracy and precision, short time reading
         Expensive, complicated, need electricity

 Passive sampling
      Time integrated conc., low cost, small size and light wt.,  
          no elect. needed, grid monitoring is possible.

-  Active sampling
- 	   High accuracy and precision, short time reading
-          Expensive, complicated, need electricity
-  Passive sampling
-       Time integrated conc., low cost, small size and light wt.,
-           no elect. needed, grid monitoring is possible.

- Ambient Air Quality Study

## Development of passive sampler

- Badge-type PS (Ayers’s protocol)
-   - The sampler body
-   -  Absorption filter
-   - Screen for dust protection
-   - Membrane for well-defined
-         diffusion length
-   - Proper abs. area:diff. path ratio

## Materials

- Development of passive sampler

**Used bottle**

**Cotton cloth**

**Rubber band**

## Development of passive sampler

## Development of passive sampler

- Absorption filter: Whatman no. 1, cellulose filter
- paper, is cut into a proper size.

## Development of passive sampler

- Cotton cloth is for dust protection and
- is to provide a well-defined diffusion length

## Passive sampler assembly

## Filter paper preparation

-    water.
- 2. Place PF in the cap and dry in the NO2 free chamber

- 3. Pipette 5o μl of coating solution into the
-     dried FP and screw-in the neck part.
-      (coating sol. = NaI + NaOH)

**Filter paper preparation**

## Sampler preparation

- 4. Close the open-end with the cotton
-     cloth and tighten it up with a rubber
-     band.

- 5. Keep the finished sampler in a
-    zipped lock plastic bag

**Sampler preparation**

## Ambient air sampling

- Samplers are protected from rain.
- Need to have the face wind velocity.
- Exposure time: 1day to 1 month or longer.
- Height = 1.5 to 2 m above ground.

## Measurements

- At the sorption filter (reaction)
-         2NO2 + 3I-  2NO2- + I3-
- Determination of [NO2-]
-              - water extraction of NO2-
-                 - NO2- + N-1-napthyl ethylenediamine    Pink color soln.
-                              dihydrochloride
-                 - Reading by Spectrophotometer (λmax = 538 nm)

## Monitoring

- Locations
-     - Lignite mining at Lampang Province
-             1. Duplicated sampling for 48 hr exposure period.
-             2. Three stations around the mining pit, 3 stations on
-                  the NE direction, and 4 station on the SW direction.
-      - KMUTT in Bangkok
-             1. Exposure time = 24 hr, duplicated sampling.
-             2. Seven days monitoring.

## Validation of PS

- Comparing
-   1. integrated passive sampling NO2 concentration
-   2. average hourly NO2 continuous monitoring at an air quality monitoring station

- Active continuous measurements

- Passive measurements

## NO2 (ppbv)  =  [nitrate (micro-mole) x hr exposed] / (7.0 x 10-5)	 

_**Comparison of R**__**2**_
**Liard = 0.79**
**Mukerjee = 0.89**
**Ayers = 0.91**
**Bush = 0.97**
**This research = 0.94**

- Validation of PS

- Mean relative error = 8.9%

## Results

| Sampling locations | [NO2], ppbv | Sampling locations | [NO2], ppbv |
| --- | --- | --- | --- |
| A | 15.7 | E | 18.0 |
| B | 15.2 | F | 18.9 |
| I  | 18.7 | G | 13.6 |
| C  | 15.6 | H | 13.3 |
| D | 17.3 | J | 18.7 |

**Table 2  Hourly avg. concentration of NO****2**** at the lignite mining area **

- NE direction

- SW direction

- Ambient NO2 at the mining site (April, 2006)

**Note: The standard ambient NO2 concentration given is ******** 120 ppbv (hourly average) **

## Figure 5  Hourly average of [NO2] monitoring at a lignite mining area (April, 2006)

**Figure 5  Hourly average of [NO****2****] monitoring at a lignite mining area (April, 2006)**

## Table 1  The hourly avg. [NO2] found and their comparison to the various locations

| Date | [NO2], ppbv | Remarks |
| --- | --- | --- |
| May 15-16,06 | 12.4 | At KMUTT, this research |
| May 16-17,06 | 12.5 |  |
| May 17-18,06 | 42.9 |  |
| May 18-19,06 | 44.8 |  |
| May 19-23,06 | 12.5 |  |
| May 23-24,06 | 9.9 |  |
| May 24-25,06 | 17.0 |  |
| In 2004 | 24 - 45 | At El Paso, Texas; by Mukerjee, et al., (2004) |
| In 2001 | 7.0 – 33.0 | At KMUTT, by Panther and Hooper (2001) |
| In 1999 | 10.6 – 58.4 | In Paris, by Liard, et al. (1999) |
| In 1998 | 21 - 29 | At Edinburgh, by Heal, et al., (1999) |
| In 1998 | 8 - 25 | At New South Wales, by Ayers et al., (1998) |

- Note: The standard ambient NO2 concentration given is  120 ppbv (hourly average)

## Conclusions

- The diffusive air sampler is a simple device for sampling of the ambient air.
- They can be self constructed from the plastic bottles, i.c. low cost.(w/o chemical, it costs less than USD 0.5)
- The calibration study indicates a good agreement between the diffusive sampler measurements and the measurement made by continuous instruments.
- Students can use their own PS to monitor NO2 concentrations in their neighborhoods and in the field applications, providing that a spectrophotometer is available.