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TECHNICAL REPORTS

Heavy Metals in the Environment

Tungsten Effects on Microbial Community Structure and Activity in a Soil

^a US Army ERDC-CRREL, 72 Lyme Rd., Hanover, NH 03755
^b US Army ERDC-EL, 3909 Halls Ferry Rd., Vicksburg, MS 39180

^* Corresponding author (David.B.Ringelberg{at}usace.army.mil).

Received for publication January 14, 2008. Tungsten, once deposited onto a soil as a result of private, industrial, and military activities, may persist as tungstate anion or, via polymerization, as a variety of poly-tungstate species, each with varying solubility and soil sorption characteristics. In this study, the impact of weathered tungsten on a soil microbial community was measured. Fatty acid analyses indicated that weathered tungsten at 2500 mg kg^–1 was associated with a significant increase in microbial biomass and that concentrations up to 6500 mg kg^–1 did not result in a significant decrease in measured biomass, relative to the control. Analysis of cellular fatty acids also identified significant microbial community shifts between 0 and 325, 1300 and 2600, and 3900 and 6500 mg W kg^–1 soil. In general, the positive effect of tungsten on microbial biomass coincided with an increase in Gram-negative bacterial fatty acids, whereas fatty acids indicative of actinomycetes and Gram-positive bacteria were more abundant at the highest soil tungsten concentrations. The weathered tungsten also inhibited N₂ fixing activity of a free living diazotroph at 1300 mg W kg^–1 soil. These results indicate that tungsten in soil can alter both the structure and the function of an indigenous soil microbial community.

Abbreviations: PC, principal component • TLFA, total lipid fatty acid • W, tungsten