Title: Laboratory test system to measure microbial respiration rate

Authors: M. Van Afferden, A.M. Hansen, C. Kaiser, N. Chapelain

Addresses: Instituto Mexicano de Tecnologia del Agua, Paseo Cuauhnahuac 8532, Col. Progreso, Jiutepec, Mor., 62550 Mexico. ' Instituto Mexicano de Tecnologia del Agua, Paseo Cuauhnahuac 8532, Col. Progreso, Jiutepec, Mor., 62550 Mexico. ' Instituto Mexicano de Tecnologia del Agua, Paseo Cuauhnahuac 8532, Col. Progreso, Jiutepec, Mor., 62550 Mexico. ' Instituto Mexicano de Tecnologia del Agua, Paseo Cuauhnahuac 8532, Col. Progreso, Jiutepec, Mor., 62550 Mexico

Abstract: This study reports a sensible, accurate and economic method for continuous measuring microbial respiration. The measuring principle is an open system, with a continuous air-flow through. Evolved CO2 is absorbed and precipitated as carbonate by a Ba(OH)2 solution, causing a stoichiometrical decrease in ionic strength of the solution and in electrical conductivity. Conductivity and Ba(OH)2 concentration correlate over a range of more than three orders of magnitude with a determination coefficient of r2 = 0.999. Between 20°C and 50°C and Ba(OH)2 concentrations of up to 0.099M, an automated temperature correction was developed. The system detects evolved CO2 quantitatively up to a maximum of 0.22 mmol O2 min-1 (825 mbar, 20°C) before limiting microbial respiration. A maximum CO2 flow of 1.06 mmol min-1 is quantitatively absorbed under these conditions. The method was applied to characterise soil respiration of a soil sample from an agricultural experimental site in Tabasco, Mexico.

Keywords: soil respiration; CO2 evolution measurements; online conductivity measurement; soil studies; carbon dioxide; soil pollution; soil contamination; microbial respiration rate.

DOI: 10.1504/IJEP.2006.009108

International Journal of Environment and Pollution, 2006 Vol.26 No.1/2/3, pp.220 - 233

Available online: 02 Mar 2006 *

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