The Tekran® Model 1135 Particulate Mercury Unit is used together with the Model 1130 Speciation Unit and the Model 2537A Mercury Analyzer to simultaneously monitor particulate bound mercury (HgP), elemental mercury (Hg0) and reactive gaseous mercury (RGM) in ambient air. The system allows fully automated, unattended operation with all three components being concurrently measured.
Although the majority of atmospheric mercury is present in elemental form, differentiation among the three types is important due to the widely varying local impacts of each type. (Particulate and reactive gaseous mercury have higher wet and dry deposition rates than does elemental.) Ambient air speciation is of particular interest close to industrial sources such as waste incinerators which often discharge the majority of their mercury emissions in particulate or ionic form.
One of the greatest problems with conventional particulate mercury measurement methods is that reactive gaseous mercury will be trapped on the filter medium along with the particulate bound mercury. This can result in large measurement artifacts. The Tekran speciation system solves this problem by removing the reactive gaseous component using a denuder before sampling the particulate mercury.
Principles of Operation
During sampling, reactive gaseous mercury in the atmosphere is captured in the Model 1130 Denuder Module. Particulate bound mercury is trapped onto a unique quartz regenerable filter located within the Model 1135. Elemental mercury passes through both units and is continuously analyzed by the Model 2537A. The components are then sequentially desorbed during the analysis phase.
Desorption Cycle
| Zero Air |
The sampling system is flooded with zero air. This air acts as a carrier during subsequent analysis steps.
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| Pyrolyzer |
The pyrolyzer is heated. This will convert to elemental form any mercury compounds that are eluted during subsequent steps
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Particulate
Trap |
The regenerable particulate trap is heated. This desorbs the particulate bound mercury captured on the trap. The Model 2537A quantitates the mercury released during this step. The heating process also reconditions the trap for subsequent cycles.
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Annular
Denuder |
The denuder is then heated, releasing the RGM that was trapped during the previous sampling period. The pyrolyzer and particulate trap continue to be heated during this step, allowing the eluted mercury to pass through without losses.
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Data Handling
Tekran provides a Windows® based application, Combine with every Model 2537A. This program provides proper time alignment for any set of data readings, leaving appropriate gaps during periods of no data and combining results from several capture files. Combine also separates data based on the status of the speciation system. Readings for RGM, HgP and Hg0 can thus be placed into separate columns, making subsequent processing by spreadsheet or database programs straightforward.
Due to continuing development, all specifications are subject to change.
