Buck Instrument AAS 200A

8/13/2019 Buck Instrument AAS 200A

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Harvey LaRocque, student intern

A. LaVallie, faculty P.I., Turtle Mountain Community

College

2010 Research Project for TCU REU


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- I am testing high risk areas across the reservation

where heavy metals contaminates maybe found.

- I expect to find moderately high levels of heavy

metal containments across the reservation.


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Objectives of the study:

-Evaluation of effectiveness of chosen methodologyin use of microwave digestion and atomicabsorption spectrometry in measurement of

various metal concentrations: Pb, Cd, Ni, Ag.

-Evaluation of random field samples from wastelocations on the Turtle Mountain Reservation to

tentatively identify potential areas of high metalconcentrations.


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- DH (destroyed housing)

- HS (new high school)

- ID (illegal dump)- LF (landfill proper)

- MC (manufacturing plant)

- NLF (North landfill slope)

- OD (old dump)

- SLF (South landfill slope) Illegal dump site


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Scale: Reservation outline is in purple, 6 mi x 12 mi.


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- DH: Destroyed housing site of 30 public housing units which

were destroyed due to flooding and mold growth.

-HS: The new high school site, where elders report that a dump

once existed.

-ID: An illegal dump located near the destroyed housing site. The

dump is fairly large and contains unknown substances.-LF: The main landfill on the reservation, located on clay soil on a

hill. Limitation of types of waste disposed there in years past

is somewhat doubtful.

-MC: A manufacturing site where metal fabrication of military

trailers took place. Various solvents and metal wastes were

reported by tribal EPA.- NLF: The north slope of the landfill hill.

- SLF: The south slope of the landfill hill.

- OD: An old dump located in the Northeast area of the

reservation, which, according to older residents, was filled

in. The surface shows no waste.


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Part of illegal dump

Destroyed housing site


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Upper left and right: landfill

Bottom left: industrial waste

near manufacturing plant


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Our Selected Procedure for Metal

Evaluation:

1. Digestion of soil samples by acid.

2. Continued soil chemical digestion by microwave.

3. Extraction of solution containing metals.

4. Dilution to standard volume.

5. Preparation of metal standards for use in AA.

6. Evaluation of metal samples by AA andcomparison to standards.


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- Field samples were crushed mildly with mortar and pestle,

and then baked at 180 C for 30 minutes.

- Then 0.50-gram samples were digested overnight with 9.0 ml

of redistilled nitric acid, 3.0 ml hydrochloric acid and 2.0 ml

30% hydrogen peroxide and 2 ml water.


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- Samples weremicrowaved at 180 Cfor 5.5 minutes andthen maintained at180 C for 4.4 minutesin a Milestone Ethosmodel.

- Samples were filteredand solution wasdiluted withdeionized water to

produce100 ml of sample witha 5% HNO3background.


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Atomic Absorption

Protocol

Buck 200A model: an old reliable,

manual AA (emphasis on the

manual). Settings controlled by

hand include:

-Current (must not exceed lamp current maximum)

- Continuous zeroing of absorbance (during drift).

-Slit and wavelength settings-Level of voltage to maximize absorption readings

-Fuel and oxygen levels (reducing or oxidizing flame)

-lighting of the flame


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Analyte detection limit(ppm) (nm) flame type

Pb 0.6 217.0 oxidizing

Cd 0.01 228.8 oxidizingNi 0.02 232.0 oxidizing

Cr 0.01 357.9 reducing

Ag 0.02 328.1 oxidizing


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- AA Theory: Electricity in metal gas lamps producesspecific UV radiation which is absorbed in turn bythe same metal present in the flame.

- Standards preparation: Stock solution is diluted to

specific concentrations to produce an absorbancevs concentration curve.

- Detection limit: 3X the standard deviation of

variances in blank readings.

- Sensitivity: The concentration which corresponds toone absorbance unit (out of 1000).


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1) Evaluation of methodology:a. Production of standards easy and accurate-

especially with commercial stocks (1000 ppm).

b. AA easy to operate with experience- need to be

able to feed solution, adjust wavelength and zeroabsorbance at the same time.

2. Evaluation of concentrations of metal in

field samplesa. Results are reliable within limit of detection-

which is amplified for soil ppm.

b. Results should be checked with another lab-

(Gary Halvorson at SBC?)


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- 1000-ppm stock solutions (Buck Scientific) were diluted toproduce at least five standards within recommended range

for each metal.

- Standards graphs (concentration vs absorbance) were fit

with trendlines for later calculation of sample

concentrations.

- Solution concentrations were converted to soil

concentrations by factoring in dilution factors and soil mass.

AA: Standards Curves


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Concentration (y axis) vs absorbance (x axis) graphs.

y = 43.868x - 0.4616

0

2

4

6

8

10

12

14

16

0 0.1 0.2 0.3 0.4

Pbconcppm

absorbance AA

Pb Standards Curve (AA)

y = 4.6777x + 0.0275

0

0.5

1

1.5

2

2.5

0 0.1 0.2 0.3 0.4 0.5

Cdconc.ppm

absorbance AA

Cd Standards Curve (AA)

y = 42.22x - 0.6975

-1

0

1

2

3

4

5

6

0 0.05 0.1 0.15

Niconcinppm

absorbance AA

Ni Standards Curve (AA)

y = 30.321x - 0.135

0

1

2

34

5

6

0 0.05 0.1 0.15 0.2

Crconcpp

m

absorbance AA

Cr Standards Curve (AA)


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Site Pb soil ppm Cd soil ppm Ni soil ppm Cr soil ppm Ag soil ppm

DH#2 D-S 0 23.53 4.42 4.98 27.70

DH#2 D-12 59.07 31.95 0 50.46 20.57

HS#4 D-S 72.23 29.15 0 0 27.70

HS#4 D-12 6.44 50.19 3.16 23.17 32.45

ID# 1 D-S 0 43.18 0 41.36 22.94

ID# 1 D-12 0 30.55 0 50.46 27.70

LF#1 D-S 203.81 27.74 0.62 32.27 25.32

LF#1 D-12 0 26.34 0 41.36 22.94

LF#2 D-S 85.39 27.74 0 23.17 34.83

LF#2 D-12 0 24.94 4.42 77.75 27.70

MC#4 D-S 98.54 38.97 0 68.65 27.70

MC#4 D-12 0 26.34 0 77.78 34.83

MC#9 D-S 59.07 26.34 0 0 25.32

MC#9 D-12 72.23 30.55 0 4.98 25.32

NLF#1 D-S 45.91 33.36 4.42 68.65 30.08

NLF#1 D-12 0 31.95 0 50.46 37.21

OD#3 D-S 59.07 26.34 0 59.56 30.08

OD#3 D-12 59.07 27.74 0.62 32.27 32.45

SLF#1 D-S 85.39 36.16 NA 23.17 25.32

SLF#1 D-12 85.39 36.16 0 68.65 22.94

SLF#2 D-S 124.86 24.94 0 0 22.94

SLF#2 D-12 6.44 36.16 0 77.75 25.32

Soil ppm


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Sample Soln. conc. (ppm) Soil conc. (ppm)

range range .

Pb 0 - 0.42 0 - 204

Cd 0.08 0.17 23.53 50.19

Ni 0 0.15 0 4.42

Cr 0.- .26 43 - 77.75

Ag 0.08 0.12 20.57 - 34.83


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- Microwave digestion and atomic absorption

spectrometer methodology gave good results

- (standards read well).

- Preparation time (crushing, drying, digesting) was

time-consuming, but AA evaluation was rapid.

- Water samples had also been collected, but time

was limited and samples were not evaluated.


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- Metal levels were not above EPA soil screeninglevels (ingestion), but may have been problems interms of EPA soil screening levels (groundwater) insome cases.*

- All Cd levels over 8 ppm (SSL groundwater)

- Nine Cr levels over 38 ppm (SSL gw)- Three Ag levels over 34 ppm (SSL gw)

* (Caution: generic soil screening levels give an average value;actual limits must be based on soil conditions likepermeability, pH, texture. Sloughs tend to have high clayand actual limits may be above the SSL.)


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Metal ingestion groundwaterlimit (ppm) limit (ppm)

Pb 400 -

Cd 78 8

Ni 1600 130

Cr 390 38

Ag 390 34

Fe (can occur naturally in soils up to 20%)

* (to be used as guidelines; actual limits must be based on soilconditions)


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- Soil metal contamination can be a huge problemwith land use change; land use maps are essential.

- This study helped increase the number of samplesin an overall metal contaminants study, which wasstarted last year.

- Further summer studies will increase the number ofsamples and attempt to pinpoint any problemareas.


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A&L Eastern Laboratories, Inc. Interpreting Soil Heavy Metals;

retrieved July 2009 fromhttp://al_labs_eastern.com/forms/HeavyMetals/Chasteen, Thomas (2000).Atomic Absorption Spectroscopy, retrieved July

2008 from http://faculty.sdiramar.edu/

Day, Robert W (2000). Soil-Testing Manual(1st Ed.) McGraw-Hill.

EPA method 3051: Microwave Assisted Acid Digestion of Sediments, Sludges,Soils and Oils (2009). Retrieved July 2009 fromhttp://www.epa.gov/epawaste/hazard/testmethods/sw846/

EPA method 7000b: Analysis of Metals in Solution by Flame AtomicAbsorption Spectrophotometry (2009). Retrieved July 2009 fromhttp://www.epa.gov/epawaste/hazard/testmethods/sw846/

Jury, William and Horton, Robert (2004). Soil Physics (6th Ed.). Wiley.

Liu, David and Liptak, Bela (1999). Groundwater and Surface WaterPollution (1st Ed.). CRC Press.
http://al_labs_eastern.com/forms/HeavyMetals/http://faculty.sdiramar.edu/http://www.epa.gov/epawaste/hazard/testmethods/sw846/http://www.epa.gov/epawaste/hazard/testmethods/sw846/http://www.epa.gov/epawaste/hazard/testmethods/sw846/http://www.epa.gov/epawaste/hazard/testmethods/sw846/http://www.epa.gov/epawaste/hazard/testmethods/sw846/http://www.epa.gov/epawaste/hazard/testmethods/sw846/http://faculty.sdiramar.edu/http://al_labs_eastern.com/forms/HeavyMetals/


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NIOSH method Lead by FAAS; Retrieved July 2010 from

http://www.cdc.gov/niosh/nmam/method-8000.html

Soil series maps for Rolette County, N.D. Retrieved July 2010 from:

http://websoilsurvey.nrcs.usda.gov/app/WebSoilSurvey.aspx

Sumner, M, (editor, 1999). Handbook of Soil Science (1st Ed.). CRC

Press.

USEPA Generic SSLs (1996); retrieved July 2010 from Table A- 1

http://www.epa.gov/superfund/health/conmedia/soil/

USEPA Regional Screening Levels (2009); retrieved July 2010 from

http://www.epa.gov/region09/superfund/prg/files/
http://www.cdc.gov/niosh/nmam/method-8000.htmlhttp://www.epa.gov/superfund/health/conmedia/soil/http://www.epa.gov/superfund/health/conmedia/soil/http://www.cdc.gov/niosh/nmam/method-8000.htmlhttp://www.cdc.gov/niosh/nmam/method-8000.htmlhttp://www.cdc.gov/niosh/nmam/method-8000.html


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Buck Instrument AAS 200A

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