Portable fluxmeter

The portable flux-meter West Systems is an instrument for the evaluation of gas exchange at interface between soli and atmosphere or between the atmosphere and liquid surfaces (lakes, swamps, etc.)

The main applications are:

Soil respiration in agronomy;
Monitoring of volcanic and geothermal areas
Determination of biogas emission in MSW landfills
Methane and carbon dioxide seepage in wet-lands areas (swamps, rice fields, etc…)

The extreme versatility of the instrument allowsthe use of a wide range of detectors for different gas species, concentration and sensitivity.

The flux rate measurement, executed on spot, is based ona non-stationary static accumulation chamber technique. This measure is indirectly obtained, by recording the specific gases concentration trendtime function, and extrapolating the increasing rate,as a proportionof the flux.

A PDA/palmtop computer allows the real time display of concentration curves versus time, and the computing of the flux value, expressed in moles/m2/day,which is proportional to the measured concentration gradient.

The following table reports different sensitivity levels (LDL) and maximum measurable flux values (FS)

	Method	LDL [moles/m^2/day]	FS [moles/m^2/day]
CH4	IR Spectrometry based on TLD Tunable Laser Diode withmultipass cell	0.001	750
CO2	IRSpectrometry	0.001	600
VOC	PID - Photo Ionization detector	2.5 x 10^-5	0.5
H2S	Electrochemical Cell	0.05	0.5

The portable flux-meter kit includes:

An accumulationchamber
A back-pack suitcase containing sensors, pump, battery and electronic interface
A PDA/palmtopcomputer with integrated GPS, to allow the control of the instrument, the real-time display of concentrations and the extrapolation of the geo-referenced flux rate measurement

The execution of each measurement (shown in the photo sequence below) requires from 2 to 4 minutes for every measured spot.