Pima County's DEQ staff mounted this tower 30 feet in the air

Pima County, Ariz. (Dec. 22, 2011) – Pima County’s Department of Environmental Quality (PDEQ) has been singled out for praise by the U.S. Environmental Protection Agency’s Office of Air Quality Planning and Standards (OAQPS).

In its December 2011 issue, the OAQPS newsletter, The QA Eye, says Pima County found a creative solution to a problem at its ambient air monitoring station in Tucson.

It said this work “serves as a great example to other agencies around the nation.”

In response to a query from another air quality monitoring agency, Pima County sent its hand-crafted solution to setting up a nitrogen converter box to the publication.

Staff working in the county’s Ambient Air Monitoring Program sent the EPA its solution to mounting a remote “NOy converter box” some 30 feet (10 meters) in the air to help measure trace concentrations of reactive oxides of nitrogen, normally lost or destroyed by a standard NOx analyzer.

NOx is a generic name for various nitrogen oxides primarily produced by cars, trucks, buses and trains. These pollutants can cause breathing difficulty in people with asthma, lung or heart disease and the elderly.

DEQ staff determined that in order to preserve the reactive oxides for analysis, part of the ambient air analyzer must be installed 10 meters above ground level.

That is where a catalytic conversion of the reactive oxides converts them to nitric oxide, a more stable gas, which can then be drawn down through connecting tubing and into an analyzer housed within a shelter below it.

By using this method of collecting air samples 30 feet up, county staff is able to detect trace reactive oxides of nitrogen. They then can be compared to the measurements of a standard NOx analyzer to mathematically determine how much of the trace reactive oxides are present in the air.

The original and seemingly simple question posed in the EPA newsletter by a Primary Quality Assurance Organization was how to properly install a remote “NOy converter box.’’

Pima County’s DEQ staff did the job for less than $300 in materials.  The solution was “simple, effective and cheap,” PDEQ staff said.

The staff machined and assembled the parts themselves and then successfully installed the converter box at the county’s air monitoring station at Children’s Park, 400 W. River Road.

PDEQ staff explains in more detail:

“An NOy converter box is part of a complicated electronic analysis of oxides of nitrogen commonly found in the air we breathe.

 “The NOy analyzer is a modified form of a standard NOx analyzer, which has been in use for decades to determine concentrations of nitrogen dioxide, a U.S. Environmental Protection Agency criteria pollutant.

 “The NOy analyzer is a fairly recent development that is intended to measure trace concentrations of reactive oxides of nitrogen that are normally lost or destroyed by a NOx analyzer.

 “It’s a complicated process, made more complicated by the necessity of mounting a 40-pound converter box and 50 pounds of interconnecting tubing and cables 10 meters (30 feet) in the air, with the means to lower it for servicing.

 “In lieu of an expensive telescopic winch-operated triangular tower, DEQ staff designed and fabricated a simple winch and pulley arrangement to raise a section of square steel tubing straight up and down through roller guides bolted to the shelter.

 “The converter is mounted to the top of the tube and is accessible when the tube is all the way down.”

Several PQAOs throughout the country also responded to the query in the EPA newsletter but The QA Eye reported that Pima County’s solution and recommendations led the pack.

Here’s what the EPA publication said about Pima County DEQ’s NOy converter installation:

“Pima’s (recommendation) was not just a recommendation but an example that made one pause and take notes on what is possible.”

Pima County’s work showed a “well-designed and crafted custom monitoring station” made from material that had been “creatively repurposed” and “re-crafted by very dedicated Pima AAMP personnel.”

“Like Pima AAMP staff, the NCORE station is first rate and serves (as) a great example to other agencies around the nation.”

A Region 9 Technical System Audit at the Tucson site in September 2011 found the AAMP Children’s Park NCORE station “impressive.”

The county is required by the federal government to measure air quality on an ongoing basis. The designated ambient air pollutants monitored and reported by PDEQ are carbon monoxide, ozone, nitrogen dioxide, sulfur dioxide and particulate matter.

This data is submitted by Pima County to the EPA Air Quality System (AQS) database. The EPA determines compliance with National Ambient Air Quality Standards (NAAQS).