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Environmental fate & pathways

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Potassium phosphite is considered a very stable substance. It is not subject to biodegradation, even if some literature demonstrates that some microorganisms are able to transform phosphite ion in phosphate: Foster and Winans (1977) and Foster et al. (1978) isolated from Cape canaveral soils microorganisms (identified as Bacillus spp., a ubiquitous spore former) that are capable of utilizing phosphite as their phosphorus source, under anaerobic conditions. Quantitative essays of labelled phosphorous demonstrated the incorporation of phosphorus from phosphite into the cell as organic phosphate. It was assumed that more microorganisms with such ability exist. Foster et al. (1978) further investigated the anaerobic phosphite utilisation by Bacillus spp., and found that it is a facultative anaerobe, which uses phosphite in preference to hypophosphite. It should be noted that when phosphate was present in the medium, no metabolism of phosphite occurred.

Nevertheless other sources related to PPP reports a DT50 soil of 157 days.

The substance could be considered persistent (DT50>120) but not very persistent (DT50>180). Further information is reported in the soil degradation section (5.2.3)

Reference:

T L Foster, L Winans, Jr, andS J Helms, Anaerobic utilization of phosphite and hypophosphite by Bacillus sp., Appl Environ Microbiol.1978 May;35(5): 937–944.