Coupling
of Oxygen and pH Requirements for Effective
Microwave-assisted Digestion of Tungsten in Soils
Christopher S.
Griggs,
U.S.
Army Corps of Engineers Engineer Research and
Development
Center
–Environmental Laboratory,
Vicksburg
,
MS
Steven L. Larson,
U.S.
Army Corps of Engineers Engineer Research and
Development
Center
–Environmental Laboratory,
Vicksburg
,
MS
Catherine C. Nestler, Applied Research Associates,
Vicksburg
,
MS
Soil
Microbial Community Response to Weathered Tungsten
David
B. Ringelberg,
USACE
Engineering Research & Development Center
,
Hanover
, NH
Anthony J.
Bednar,
USACE
Engineering
Research & Development
Center
,
Vicksburg
,
MS
Laura L. Inouye,
USACE
Engineering
Research & Development
Center
,
Vicksburg
,
MS
David R. Johnson,
USACE
Engineering
Research & Development
Center
,
Vicksburg
,
MS
Charles M. Reynolds,
USACE Engineering Research & Development Center
,
Hanover
, NH
Coupling
of Oxygen and pH Requirements for Effective
Microwave-assisted Digestion of Tungsten in Soils
Christopher S.
Griggs,
U.S.
Army Corps of Engineers Engineer Research and
Development
Center
–Environmental Laboratory (ERDC-EL)
3909 Halls Ferry Rd
,
Vicksburg
,
MS
39180
, Tel: 601-634-4821, Email:
Chris.S.Griggs@erdc.usace.army.mil
Steven L. Larson,
U.S.
Army Corps of Engineers Engineer Research and
Development
Center
–Environmental Laboratory (ERDC-EL)
3909 Halls Ferry Rd
,
Vicksburg
,
MS
39180
, Tel: 601-634-3431, Email: Steven.L.Larson@erdc.usace.army.mil
Catherine C. Nestler, Applied Research Associates,
119 Monument Place
,
Vicksburg
,
MS
39180
, Tel: 601-634-4650, Email: Catherine.C.Nestler@erdc.usace.army.mil
Fully understanding
the environmental fate of tungsten is an ongoing
critical challenge from an analytical perspective.
At issue is the lack of effective laboratory
methods for quantifying tungsten in soil. Developing the
methods necessary to accurately and consistently monitor
tungsten in soil matrices is an essential tool for
modeling W migration towards groundwater resources.
Traditional digestion procedures such as SW-846 Method
3051B usually employed for the analysis of heavy metals
are not uniformly useful for Tungsten. The chemistry of
W presents unique challenges due to the metals ability
to polymerize under acid conditions. Currently, the
standard method utilizes nitric acid to solubilize the
metals but, in the case of tungsten, this acidification
encourages the formation of insoluble polytungstates
resulting in unrecoverable solid tungstate residues in
the digestion vessels and filters and a decrease in
recovery. This compromises the ability to accurately
compare data directly. Therefore method modifications
are required to the digestion procedure outlined in
SW-846 Method 3051B to enhance W recovery from soils. To
this end, several method modifications were evaluated
for determining tungsten concentration in five soil
types. The new method modifications of SW-846 Method
3051B increased the average tungsten percent recovery
from 10.2% in the standard method, to 88.2% over the
five soil types evaluated. This presentation will
discuss these analytical procedures in terms of
efficiency and laboratory implementation.
Soil
Microbial Community Response to Weathered Tungsten
David B.
Ringelberg,
USACE Engineering
Research & Development Center
,
Hanover
, NH, 03755,
USA
, 603-646-4744, Email: David.B.Ringelberg@usace.army.mil
Anthony J. Bednar,
USACE
Engineering
Research & Development
Center
,
Vicksburg
,
MS
,
39180
,
USA
, 601-634-3652, Email: Anthony.J.Bednar@usace.army.mil
Laura L. Inouye,
USACE
Engineering
Research & Development
Center
,
Vicksburg
,
MS
,
39180
,
USA
, Email: inouyel@comcast.net
David R. Johnson,
USACE
Engineering
Research & Development
Center
,
Vicksburg
,
MS
,
39180
,
USA
, 601-634-2910, Email: David.R.Johnson@usace.army.mil
Charles M. Reynolds,
USACE Engineering Research & Development Center
,
Hanover
, NH, 03755,
USA
, 603-646-4394, Email: Charles.M.Reynolds@usace.army.mil
Tungsten metal, deposited
onto soils as a result of private, industrial and military
activities, often persists as a tungstate anion or, via
polymerization, as a variety of poly-tungstate species.
An ongoing research effort by Engineering Research
and
Development
Center
investigators has examined tungsten speciation in soils
and toxicity to earthworms and plants.
In the present study, the impact of weathered
tungsten on an indigenous soil microbial community was
measured. Metallic
tungsten was loaded into a soil to obtain 5 exposures, 0
to 6500 mg W kg-1 soil, and then aged for a
period of 6 months. Weathering
was indicated by the recovery of half of the added
tungsten, via water extraction, in the form of polymers.
Analysis of extracted fatty acid profiles
identified a significant affect of increasing soil
tungsten concentration on microbial community composition.
Community shifts were measured in response to 325,
2600, and 6500 mg W kg -1 soil exposures.
A small positive, hysteresis, effect on microbial
biomass was observed at 2600 mg W kg-1 soil,
which coincided with a percent increase in
Gram-negative bacterial fatty acids.
In contrast, fatty acids indicative of
actinomycetes and Gram-positive bacteria were more
abundant at the greater, 3900 and 6500 mg kg-1
tungsten exposures. Analysis
of terminal restriction fragment length polymorphisms
identified a loss
in diversity and persistence of actinobacteria and gamma-proteobacteria
with increasing soil tungsten concentrations.
The weathered tungsten was also found to
inhibit the N2 fixing activity of a free living
diazotroph at ≥ 1300 mg W kg-1 soil.
The results of this study indicated that the
weathering of tungsten metal in a soil can induce changes
to the structure and, potentially, the function of an
indigenous soil microbiota.
Future studies will examine specific links between
metal speciation and microbial response.
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