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Giordan Lighthouse
-NO2-
| Observation |
| Category |
: |
Air sampling observation |
| Situation |
: |
ongoing |
| Time zone |
: |
Local time +1 |
| Sampling |
| Sampling height |
: |
7 |
| Description |
: |
continuous |
| Sampling and analysis frequency |
: |
Continuous at ambient pressure |
| Sampling environment |
: |
When wind is blowing from 120-150 (over Malta), it is affected by local pollution and therefore ozone is depleted. |
| Description for sampling analysis |
: |
PTFE intake 4.5 m long with an internal diameter 0.04 m. Intake height: 7 metres above ground. The intake is connected to a glass manifold approximately 0.64 meters long. The manifold consists four nipples to feed trace gases instruments. The flow rate through the complete inlet is supported by a blower. Ambient air is supplied to the analysers via 6mm PTFE tube connected between the manifold and the inlet of the analyser. The analyser is assigned with a 5 micron filter which is changed every two weeks. Air is sampled every 10 seconds and a 1 minute average is stored in the Web Data logger from Envirologger Limited. |
| Instrument and Analysis |
| Measurement method |
: |
Chemiluminescence |
| Current status and history of instrument |
: |
2011 January - present Model 42i Thermo electron corporation |
| Description of instrument |
: |
LDL: 0.40ppb
measurement range: 0-200ppb
linearity: ± 1% of full-scale
Zero drift: < 0.40 ppb/24 hour
Span drift: ± 1% full-scale
Response time: 80 sec
|
| Calibration |
| Current scale employed in the measurement |
: |
traceable to national standard scale |
| Measurement calibration |
: |
The instrument is automatically calibrated daily with calibration gases supplied by Air Liquide. The instrument is given the zero span followed by the span cycle. |
| Scale and calibration(treasability) |
: |
Calibration gases are calibrated every 12 months. |
| Data Processing |
| Measurement unit |
: |
ppb |
| Data processing |
: |
The raw data from the instrument is collected by the data acquisition
system, and stored in the system as one minute average raw data. The
minutely averaged raw data is converted to physical data using
zero/calibration factors measured in the observation sequences.
Invalid data caused by instrumental malfunction are checked by
comparison/correlation with other trace substances and meteorological
data or with information from the station logbook. |
| Processing for averaging |
: |
Processing for Hourly Data:
Hourly data are generated by arithmetic means from the per-minute
data without including invalid data. If the number of valid data
within an hour is less than 30, the hourly mean value is flagged as 2.
If all data within an hour are invalid, the hourly mean value is no data.
Processing for Daily Data:
Daily data are generated by arithmetic means from the per-minute
data without including invalid data. If more than 80% of hourly data with a 0 flag are available daily data is flagged as 0.Otherwise, daily data is flagged as 2. If all data within a day are invalid, the daily mean data is no data.
Processing for Monthly Data:
Monthly data are generated by arithmetic means from the per-minute
data without including invalid data.0 flag if more than 1/3 of daily data with a 0 flag are available.Otherwise, monthly data is flagged as 2. If all data within a month are invalid monthly data is no data. |
| Data flag |
: |
0: Background Data
2: insufficient number of averaging data |
| Data remarks |
: |
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| Other Information |
| Scientific aim |
: |
to provide data for research and study to reveal long term trends |
| Reference |
: |
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| submitted by University of Malta |
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