Air Quality Monitoring
In order to assess and maintain air quality in the district, we
monitor air pollution at specific locations every day of the year.
The two sampling methods we use are described below:
Passive Sampling
This form of sampling involves using diffusion tubes, which
measure Nitrogen Dioxide (NO2). These are small, clear plastic
tubes which are typically placed at roadside locations for a month
at a time and positioned on posts approximately two metres above
the ground. The top of a tube has a cap which contains steel gauze
and a reactive chemical material, whilst the bottom of the tube is
open. This allows air contact with the reactive material within the
tube, as well as protection from the weather.
The material at the top of the tube reacts with the Nitrogen
Dioxide (NO2) in the air, and converts this to Nitrate (NO-3). The
Nitrate is then trapped in the steel gauze. At the end of the
month, all the tubes are replaced and those collected are sent to
an accredited laboratory to be examined.
Diffusion tubes offer an inexpensive and easy way of obtaining
an indication of the average air pollution over a known period of
time. We currently have diffusion tubes at 11 roadside locations
across Rayleigh and Rochford.
The latest diffusion tube results can be viewed and downloaded
by following the link to the Essex Air Quality Consortium
website.
Note to air quality professionals: The data contained in the
spreadsheet is raw, uncorrected data.
Automatic Sampling
We occasionally use continuous analysers to measure air
pollution at particular locations.
Automatic analysers are available to monitor a wide range of
pollutants very accurately and reliably. Because the results taken
from an analyser are in real time, it is possible to understand
when a period of poor air quality may occur and why.
In the past, we have used continuous analysers to monitor
Nitrogen Dioxide (NO2) in Rayleigh High Street and fine airborne
dust (PM10) close to Rawreth Industrial Estate.
We currently have an NO2 analyser located in Rayleigh High
Street and it will be there until Autumn 2010. We will also shortly
be re-introducing a PM10 analyser to Victoria Avenue, Rayleigh, to
monitor emissions coming from Rawreth Industrial Estate for
approximately one year.