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Glindemann, D., Stottmeister, U., Bergmann, A.:
Free phosphine from the anaerobic biosphere. Environ.Sci.&Pollut.Res. 3 (1996) 17-19

D. Glindemann1), U. Stottmeister2) and A. Bergmann1)
1) Institute of Animal Hygiene and Public Veterinary Health
University of Leipzig
Semmelweisstr. 4
D-04103 Leipzig
Germany
Phone: +49-(0)341-9738-165, -158 Fax:+49-(0)341-9738198
e-mail dglinde@rz.uni-leipzig.de

2) Department of Remediation Research, Centre for Environmental Research Leipzig-Halle Ltd.

ABSTRACT: The possible liberation of highly toxic and mutagenic phosphine from putrefying media raises the question of its significance as a problem of hygiene. Free phosphine was established by gas chromatography as a universal trace component in gas emitted from the anaerobic biosphere. Sources of phosphine include landfills, compost processing, sewage sludge, animal slurry and river sediments. We detected maximum concentrations in the order of 20 ppb(v/v).

INTRODUCTION: Phosphine PH3, an input and output component of the chemical industry, metallurgy and fumigation, is known to be highly toxic. Therefore its use and emission requires special hygienic control (see 11 for an overview about aspects of toxicity, analysis, chemical sources and fate). The hygienic problem of phosphine has been under review since GARRY et al (5) and others (1) described the mutagenity of phosphine on humans, animals and plants. In particular, emissions from suspected microbial sources of phosphine must be taken into consideration; DEVAY et al (3) claimed to find up to 382 mg/m3 (538 ppm (v/v)) phosphine in Hungarian digester gas, a concentration which could be fatal when inhaled. The capability of microorganisms to generate phosphine in putrefying media has long been the subject of controversially discussion (2,3,4,6-10). Gassmann and Glindemann (4) developed a reproducible experiment to show the capability of a mixed faecal flora to produce matrix-bounded biogenic phosphine. They detected this "cryptic" phosphine after liberation by alkaline digestion in a variety of bio-sludges under laboratory conditions. However only free phosphine can be inhaled by humans in the environment. The possible liberation of highly toxic and mutagenic phosphine from putrefying media raises the question of its significance as a hygienic problem. The present work was carried out in order to produce a survey of the importance of sources suspected to spontaneously emit free phosphine anticipated to be biogenic. The investigations were carried out during different seasons of a year to register the impact of the climate. The expected results can be interpreted not so much causally but rather as phenomena, because the generation and liberation of phosphine is multicausal. We expected the highest concentrations in landfills, compost processing, sewage, animal slurry and polluted river sediments, where the ancient anaerobic "microbial" capabilities encounter the anthropogenic enrichment of nutrients and can become a "human" problem for environmental investigation.

MATERIAL AND METHODS: (Details of the procedures are available from the authors)

Types of gas samples, principles of their obtainment: Biogas (digester gas, fermentation gas) is the product of regulated methanogenesis in closed anaerobic digesters. It flowed by means of its own overpressure into sampling bags. Putrefaction gas is the product of several unregulated, mainly anaerobic lysis and digestion processes in open sedimenters, tanks or basins. It had to be accumulated in floating funnels prior to mixing with air.
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*This work is supported by the Centre for Environmental Research Leipzig-Halle Ltd., by the Ministry for Education, Science, Research and Technology as by the Saxony State Department of Environment and Geology. It constitutes part of joint project work with the Centre for Environmental Research Leipzig-Halle Ltd., Department of Remediation Research.

It flowed through a tube from the top of the funnel into sample bags owing to the hydrostatic pressure of the suspension replaced by the gas in the funnel. Landfill gas is mainly a product of anaerobic processes in landfills. It had to be sampled by vacuum from a depth of several meters. Interstitial gas is a mixture of gaseous products and strong polluted deoxigenized air in the mainly anaerobic part of solid waste, for example in the composting process. It had to be sampled by vacuum pumps from a depth of about one metre. Marsh gas is chiefly a product of methanogenesis in aquatic sediments. It had to be sampled with flat funnels placed directly upon the sediment to avoid washing out the phosphine by bubbling through the water layer. Sample preparation: The gas samples were transported in Tedlar sampling bags. Bags for atmospheric samples had to be stored in containers free of phosphine. Hydrogen sulfide, carbon dioxide and water were removed prior to analysis using solid NaOH. Trace analysis of phosphine by gas chromatography: The HP 5890 II gas chromatograph was equipped with a thermionic nitrogen phosphorus detector (NPD). The standard column Poraplot Q (Chrompack) was 10 m long with an internal diameter of 0.32 µm. The gas samples (mostly 5 - 50 ml) were cryo-trapped to remove the matrix methane or air and to focus the phosphine peak. The detection limit was 0.1 ppt(v/v) for 50 ml samples and 0.01 ppt for 500ml. Concentration was estimated by comparison with a standard. Each sample was measured twice, with a maximum deviation of about 20%.

RESULTS: Table 1 contains the concentrations and fluxes of free phosphine in gas samples from the anaerobic biosphere. The maximum imission concentration of phosphine in the closed working atmosphere near the sources was 41 ppt (domestic sewage plant, sludge drying process, near centrifuge).

DISCUSSION: Spontaneously free phosphine is universally present in a variety of gases emitted from the biosphere. Landfills liberated the highest concentrations and fluxes. However, chemical source processes of phosphine via the hydrolysis of metal phosphides especially in landfills can not be excluded. Putrefaction processes in open basins also liberated high concentrations but low fluxes. The seasonal trend of the concentration and flux in gas from open putrefaction processes and landfill displays higher values in summer. The composting process (which is perceived as mainly aerobic), produced more phosphine in winter, which seems to be a result of the higher wetness of the medium as a condition for local anaerobiosis. Domestic sewage sludge liberates phosphine immediately after stabilization with lime, which can be interpreted as analogous to the liberation of matrix-bounded phosphine by the process of alkaline digestion suggested by Gassmann and Glindemann (4). The German digester gas analyzed contained about 6 orders of magnitude less phosphine than the Hungarian samples from Devaý (3). This could be caused by the efficient phosphate elimination procedure in the German sewage plants observed. Our future work will investigate both the biogenic and chemogenic mechanisms of the liberation of phosphine in the environmental biosphere.

 

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