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Description

Enviromonitor

The main objective of the ENVIROMONITOR project is to develop a mobile instrument for qualitative and quantitative analysis of breathable particles. Measurements will be done continuously in real-time, and fast data processing will facilitate the utilization of an alarm function for critical monitoring tasks and in emergency situations. The latest developments in X-Ray Diffraction (XRD) are used to meet these needs. The main challenges to realize this are the collection and automatic transportation of airborne particles into the instrument, development of suitable data processing algorithms for automatic analysis and the limited portability of XRD instruments.

To download : "Air Quality Monitoring : Particulate Matter 10 and 2,5"

Description of the device

Enviromonitor is a transportable system and is easy to install in any place. The main requirement is a power supply (220v- 600watt), which can be achieved by a generator.
The system can be installed outside and weather improved (IP63) for mining survey or close to factory (cement), or close to the cheminey for the industrial emission control.
The system is self. It can repeat a loop task from the aerosol sampling, the analysis and data treatment, defined by operator. It is network with other system.

Vue schématique

 

 

 

Selected housing is composed by two resin epoxy boxes. Air conditionning is attached on the cover of the upper box, and can be removed. For transportation, the system is dismanteled in several parts :

- Electronic box, bottom
- Pumping assistance (which is introduced in a lodging inside the electronic box)
- The air conditionning (optional) which is attached to the rear cover of the instrument box
- Instrument box

An accessory box should be added, in which is stored the heads, pipe, roll, and tools.  

 

 Caisson ouvert

 

 Enviromonitor is composed by :

A gravimetric aerosol sampler
A mini X-ray diffractometer
A filter band sample-changer
A housing
Computer for driving the system and perform the data treatment

 

The sampling device is compatible with the norm EN 12341 and EN 14907. the flow is kept constant to 2.3m3/h.

Because of the improvement in the field of X-ray sources, Enviromonitor has the full capacity of a X-ray diffractometer but with a small volume and electrical consumption. Indeed, the weight of the XRD part is about 30kg only. The XRD instrument is compatible with the norm EN 61010-1.

The sample changer is able to drive a filter band from the dust collection chamber to XRD with a good accuracy.

All components are driven by TCPIP, and can be remote controlled.

 

 

 

To download : "Enviromonitor Project, a new system for Air Monitoring"

 

Determination of the detection limit of Enviromonitor

The determination of the detection limit has been done by recording a known amount of a given aerosol. Individual teflon filters have been exposed to a controlled flow of nanoparticles of TiO2 (NP25). This is achieved by using a designed setup (figure). A solution containing nanoparticles of TiO2 is vaporized in a tubular circuit. The flow is dried by using silicagel. The dry stream is pumped through a teflon filter disk (41mm diameter), set in a millipore filter holder. Since th flow is constant, several filters have been exposed at different time. The weight of deposit has been determined with a microbalance.

 

 

 

 

 

 

Setup for TiO2 deposition on PTFE membranes 

Each filters have been analysed by XRD with an acquisition time of 1hour. The figure 2 shows the superimposition of the different XRD curves vs weight. The signal was still detected for the filter containing 95mg of TiO2. By considering the ratio between beam size and filter surface, there is a high potential of resolution increased. In other words, a concentration of dust on a surface of 9mm diameter will allow to reach a limit of detection of 5mg.

 

 

   

 XRD patterns on filters after various content of TiO,
for 1h data acquisition

 Plot of integrated peak of TiO2 vs weight deposit
 

 Path of the filter band, inside the system

The filter band (B) is stored in a reel (A). the filter band pass through the dust collection chamber, DCC in (D), and aerosol comes from the upper chimney (C). After a given collection time, the aerosol deposition is analysed by moving the band position to (E). In (E) is shown the dust coating in ambient. Both, DCC and XRD are working together, but when DCC is collecting, XRD is analysing the previous collection.

Data storage in SQL

Configuration of the system, raw data and result are save in a designed SQL database. The goal is to permit special requests with one or several connected system, in order to perform combined analysis. This will be a core for developping maps vs time, in order to follow the evolution of aerosol spreading.

Enviromonitor and the automatic XRD expertise

The XRD method allows to perform phase identification and quantification along with crystallites/microstrains (by XRD). In the Nanoair project, a software was developed in order to perform an automatic data treatment of XRD patterns, based on the Rietveld method. During the Enviromonitor project, the program has been interfaced in TCPIP, and tested on real cases. The storage interface is the SQL format.

For the XRD automatic analysis objective, we recognized :

• Actual search-match softwares require still human intervention to judge which phases are to be accepted or rejected after identification
• The only quantification method easily automatizable and reliable for such task is the Rietveld method but we are limited to the phases with a structure already refined (and deposited in one of the databases) unless also the PONKS method is used
The idea is to use the Rietveld (+ PONKS) also for the search-match step (as we are in any case limited to phases usable in the Rietveld).
A Full Pattern Search-Match method has been built and tested using the COD archive (imported to a local database) plus we can add specific phases missing if necessary. COD: www.crystallography.net

 

The FPSM (Full Pattern Search-Match method)
Pro :
• No user intervention, automatic analysis
• No peaks identification required (works with nano materials/particles
• Full Rietveld quantitative analysis provided
• Works for neutron and electron diffraction
Cons :
• Only phases with know crystal structure are ready to be used (unknown structures require a list of peaks and calibrated intensities, PONKS)
• Available databases are still uncompleted
• If no elemental composition provided → requires > 20 minutes on 12 cores computer
• Good ranking algorithm required for very small phase amount

Search and quantification is limited by the time required (or better server response time) so it should be used restricting the composition as much as possible to speed up computation. A limited number of concurrent connections are supported also. INEL SAS can be inquired for the full version.

A demo version has been setup online at: http://cod.iutcaen.unicaen.fr/

To download : "Full Pattern Search-Match and Quantitative Phase Analysis"

 

The previous figure represents a comparison of refinement between SFPM and MAUD. With Maud, the operator should first identify the phase, by using a search match software. Then, he should introduce the structural card in Maud to perform the refinement and get a precise result on quantitative analysis. Estimated time and efforts can be measured in hours or days, and the reliability depends on the accuracy of the simplified search match database. Each steps are manually performed, and need some skillfulness and experience.
With SFPM, the raw data are submitted to the program and a test an trial analysis is automatically done by using structural database from COD. From this comparison we can conclude that results are consistent.
This method can be extended to many fields, such as mining, geology, pharmacy, metallurgy, forensic...

Analysis of a synthetic mixture deposit on a mylar film. comparison between SFPM and MAUD

 

 

Enviromonitor in action 

Measurement in ambient air have been performed.

The system was controlled from a minivan.