Background Trace Element Concentrations in the Franciscan Complex, San Francisco, CA MS Thesis...

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Background Trace Element Concentrations in the Franciscan Complex, San Francisco, CA MS Thesis Defense Megan Simpson March 16, 2004

Transcript of Background Trace Element Concentrations in the Franciscan Complex, San Francisco, CA MS Thesis...

Page 1: Background Trace Element Concentrations in the Franciscan Complex, San Francisco, CA MS Thesis Defense Megan Simpson March 16, 2004 MS Thesis Defense Megan.

Background Trace Element Concentrations in the Franciscan Complex,

San Francisco, CA

Background Trace Element Concentrations in the Franciscan Complex,

San Francisco, CA

MS Thesis Defense

Megan Simpson

March 16, 2004

MS Thesis Defense

Megan Simpson

March 16, 2004

Page 2: Background Trace Element Concentrations in the Franciscan Complex, San Francisco, CA MS Thesis Defense Megan Simpson March 16, 2004 MS Thesis Defense Megan.

The ProblemThe Problem

•Superfund clean-up sites are overwhelming problem in US

-Hunter’s Point Shipyard

-Presidio

•To assess a site for contamination, background trace element levels need to be determined

•Superfund clean-up sites are overwhelming problem in US

-Hunter’s Point Shipyard

-Presidio

•To assess a site for contamination, background trace element levels need to be determined

Page 3: Background Trace Element Concentrations in the Franciscan Complex, San Francisco, CA MS Thesis Defense Megan Simpson March 16, 2004 MS Thesis Defense Megan.

IntroductionIntroduction

• This study examines background trace element levels in the Franciscan Complex

(chert, sandstone, greenstone, serpentinite)

• Samples analyzed for trace element levels (chromium, cobalt, nickel, lead, strontium)

• Performed statistical analyses and created trace element distribution maps

• This study examines background trace element levels in the Franciscan Complex

(chert, sandstone, greenstone, serpentinite)

• Samples analyzed for trace element levels (chromium, cobalt, nickel, lead, strontium)

• Performed statistical analyses and created trace element distribution maps

Page 4: Background Trace Element Concentrations in the Franciscan Complex, San Francisco, CA MS Thesis Defense Megan Simpson March 16, 2004 MS Thesis Defense Megan.

PurposePurpose• Will aid in understanding of the distribution of

background trace elements– data reflects naturally occurring levels found in

native bedrock

• Assist environmental clean-up projects by providing source of baseline data for measuring soil quality

• Expand current trace element level database

• Will aid in understanding of the distribution of background trace elements– data reflects naturally occurring levels found in

native bedrock

• Assist environmental clean-up projects by providing source of baseline data for measuring soil quality

• Expand current trace element level database

Page 5: Background Trace Element Concentrations in the Franciscan Complex, San Francisco, CA MS Thesis Defense Megan Simpson March 16, 2004 MS Thesis Defense Megan.

Previous ResearchPrevious Research• Work by Kearney Foundation in 1996

– looked at trace elements in soil– often referenced in remediation projects, land use planning– only two samples close to San Francisco Area

• Work by Schlocker in 1974– looked at potassium feldspar in sandstone– fewer samples (5-7) for each rock type

• My work enhances the range of sample locales and quantities

• Work by Kearney Foundation in 1996– looked at trace elements in soil– often referenced in remediation projects, land use planning– only two samples close to San Francisco Area

• Work by Schlocker in 1974– looked at potassium feldspar in sandstone– fewer samples (5-7) for each rock type

• My work enhances the range of sample locales and quantities

Page 6: Background Trace Element Concentrations in the Franciscan Complex, San Francisco, CA MS Thesis Defense Megan Simpson March 16, 2004 MS Thesis Defense Megan.

What elements are we looking for?

What elements are we looking for?

• Previous work shows Cr, Co, Ni, Pb and Sr to be prominent in soil and rock within SF

• Presidio and Hunter’s Point have high levels– much time and energy dedicated to clean-

up of these sites

• Previous work shows Cr, Co, Ni, Pb and Sr to be prominent in soil and rock within SF

• Presidio and Hunter’s Point have high levels– much time and energy dedicated to clean-

up of these sites

Page 7: Background Trace Element Concentrations in the Franciscan Complex, San Francisco, CA MS Thesis Defense Megan Simpson March 16, 2004 MS Thesis Defense Megan.

Geologic BackgroundGeologic Background

San Francisco is part of the Mesozoic Franciscan Complex, which formed in accretionary wedge

San Francisco is part of the Mesozoic Franciscan Complex, which formed in accretionary wedge

Subduction zone ~200-80 myaSource: U.S. Geological SurveySource: U.S. Geological Survey

Franciscan ComplexFranciscan Complex

Page 8: Background Trace Element Concentrations in the Franciscan Complex, San Francisco, CA MS Thesis Defense Megan Simpson March 16, 2004 MS Thesis Defense Megan.

Franciscan Complex

Serpentinite

Greenstone

Sandstone

Melange up to 10,000 ft thick

Also chert, shale, limestone, conglomerate

Page 9: Background Trace Element Concentrations in the Franciscan Complex, San Francisco, CA MS Thesis Defense Megan Simpson March 16, 2004 MS Thesis Defense Megan.

Depositional EnvironmentDepositional Environment• Most likely a low latitude marine environment:

– marine fossils in some clastic rocks, Radiolaria in chert

– highly fractured, interbedded greenstones (rapid cooling of hot lava)

• Conglomerate and massive graywacke beds created by turbidity currents– further evidence:

• shale layers between graded beds, small scale current bedding, ripple marks

• Most likely a low latitude marine environment:– marine fossils in some clastic rocks, Radiolaria in

chert– highly fractured, interbedded greenstones (rapid

cooling of hot lava)

• Conglomerate and massive graywacke beds created by turbidity currents– further evidence:

• shale layers between graded beds, small scale current bedding, ripple marks

Page 10: Background Trace Element Concentrations in the Franciscan Complex, San Francisco, CA MS Thesis Defense Megan Simpson March 16, 2004 MS Thesis Defense Megan.

Methods and MaterialsMethods and Materials

• Prior to sampling– aerial photographs

• Sampling– Samples were collected from 45 accessible

outcrops around SF– Clean hands/dirty hands technique (minimizes

cross contamination)– At least 5 fresh rock chips collected from

outcrop and pooled– Latitude/longitude of location noted with GPS

unit

• Prior to sampling– aerial photographs

• Sampling– Samples were collected from 45 accessible

outcrops around SF– Clean hands/dirty hands technique (minimizes

cross contamination)– At least 5 fresh rock chips collected from

outcrop and pooled– Latitude/longitude of location noted with GPS

unit

Page 11: Background Trace Element Concentrations in the Franciscan Complex, San Francisco, CA MS Thesis Defense Megan Simpson March 16, 2004 MS Thesis Defense Megan.

Aerial PhotographyAerial Photography

• USGS collection from 1940s-1970s

• Provided insight into previous industrial activity

• Showed sampling areas free from major contaminating factors

• No evidence of alteration of background levels

• USGS collection from 1940s-1970s

• Provided insight into previous industrial activity

• Showed sampling areas free from major contaminating factors

• No evidence of alteration of background levels

Presidio Area

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45 sample locations45 sample locations

Presidio

Twin Peaks/

Glen Park

Potrero Hill

McLaren Park

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Chert Sample LocationsChert Sample Locations

• 15 samples• Glen Canyon Park,

Twin Peaks• light tan to red• distinct bedded

layers with folding

• 15 samples• Glen Canyon Park,

Twin Peaks• light tan to red• distinct bedded

layers with folding

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Greenstone Sample LocationsGreenstone Sample Locations

• 8 samples• McLaren Park, Corona

Heights, Twin Peaks• highly fractured• extensively weathered• dark gray to dark

reddish-brown

• 8 samples• McLaren Park, Corona

Heights, Twin Peaks• highly fractured• extensively weathered• dark gray to dark

reddish-brown

Page 15: Background Trace Element Concentrations in the Franciscan Complex, San Francisco, CA MS Thesis Defense Megan Simpson March 16, 2004 MS Thesis Defense Megan.

Sandstone Sample LocationsSandstone Sample Locations

• 10 samples• McLaren park, Castro• large, thick bedded

outcrops• randomly fractured• highly weathered• brown to gray

• 10 samples• McLaren park, Castro• large, thick bedded

outcrops• randomly fractured• highly weathered• brown to gray

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Serpentinite Sample LocationsSerpentinite Sample Locations

• 12 samples• Potrero Hill, Presidio,

Baker Beach• greenish-gray to blue• highly weathered,

sheared• soft, friable

• 12 samples• Potrero Hill, Presidio,

Baker Beach• greenish-gray to blue• highly weathered,

sheared• soft, friable

Page 17: Background Trace Element Concentrations in the Franciscan Complex, San Francisco, CA MS Thesis Defense Megan Simpson March 16, 2004 MS Thesis Defense Megan.

Geochemical AnalysisGeochemical Analysis• 48 samples submitted to SGS Mineral Services in

Toronto (45 plus 2 blind duplicates and 1 reference sample)

• Tested for 40 trace elements using ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry)

– Samples decomposed using mixture of HCl, Nitric, Perchloric, HF

– Digestion is aspirated and elemental emission signal is measured for elements

• 48 samples submitted to SGS Mineral Services in Toronto (45 plus 2 blind duplicates and 1 reference sample)

• Tested for 40 trace elements using ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry)

– Samples decomposed using mixture of HCl, Nitric, Perchloric, HF

– Digestion is aspirated and elemental emission signal is measured for elements

Page 18: Background Trace Element Concentrations in the Franciscan Complex, San Francisco, CA MS Thesis Defense Megan Simpson March 16, 2004 MS Thesis Defense Megan.

•Identification of outcrop samples

•Geochemical results

•Statistical analysis

•Mann-Whitney and ANOVA

•Developed trace element distribution maps

•Identification of outcrop samples

•Geochemical results

•Statistical analysis

•Mann-Whitney and ANOVA

•Developed trace element distribution maps

Results and DiscussionResults and Discussion

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Identification of Outcrop SamplesIdentification of Outcrop Samples

• Field Identification

• Thin sections from each rock type (Univ of Utah)

• X-ray Diffraction (XRD) evaluation

• Field Identification

• Thin sections from each rock type (Univ of Utah)

• X-ray Diffraction (XRD) evaluation

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Thin Sections (USGS Petrographic Microscope)

Page 21: Background Trace Element Concentrations in the Franciscan Complex, San Francisco, CA MS Thesis Defense Megan Simpson March 16, 2004 MS Thesis Defense Megan.

Thin Sections (USGS Petrographic Microscope)

Page 22: Background Trace Element Concentrations in the Franciscan Complex, San Francisco, CA MS Thesis Defense Megan Simpson March 16, 2004 MS Thesis Defense Megan.

X-ray DiffractionX-ray Diffraction

• Scattering of x-rays from a crystal where resulting interference pattern determines structure of crystal

• Performed by Mineral Services Lab at USGS• Showed minerals consistent with each rock type

– Serpentinite (lizardite, chrysotile)– Chert (quartz)– Sandstone (quartz)– Greenstone (albite, diopside)

• Scattering of x-rays from a crystal where resulting interference pattern determines structure of crystal

• Performed by Mineral Services Lab at USGS• Showed minerals consistent with each rock type

– Serpentinite (lizardite, chrysotile)– Chert (quartz)– Sandstone (quartz)– Greenstone (albite, diopside)

Page 23: Background Trace Element Concentrations in the Franciscan Complex, San Francisco, CA MS Thesis Defense Megan Simpson March 16, 2004 MS Thesis Defense Megan.

XRD of Chert

Quartz

0

7000

40 2 theta

Count/s

Page 24: Background Trace Element Concentrations in the Franciscan Complex, San Francisco, CA MS Thesis Defense Megan Simpson March 16, 2004 MS Thesis Defense Megan.

Geochemical ResultsGeochemical Results• Results for Cr, Co, Pb, Ni, Sr compared to

data from Schlocker show:• Results for Cr, Co, Pb, Ni, Sr compared to

data from Schlocker show:

Chromium

Lead

Cobalt

Nickel

Strontium

Page 25: Background Trace Element Concentrations in the Franciscan Complex, San Francisco, CA MS Thesis Defense Megan Simpson March 16, 2004 MS Thesis Defense Megan.

Statistical analysis comparing my data to

Schlocker’s data

Statistical analysis comparing my data to

Schlocker’s data

• Assists in description and analysis of data– generated descriptive statistics (mean, std

dev, ranges, etc.)– histograms (show distribution and

observations of sample)– tests for normality (data fits bell shaped curve)

• Komolgorov-Smirnov, Shapiro-Wilk

– Q plots (compare data to linear ideal)

• Assists in description and analysis of data– generated descriptive statistics (mean, std

dev, ranges, etc.)– histograms (show distribution and

observations of sample)– tests for normality (data fits bell shaped curve)

• Komolgorov-Smirnov, Shapiro-Wilk

– Q plots (compare data to linear ideal)

0

0.5

1

1.5

2

2.5

3

3.5

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4.5Fr

eq

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ncy

Page 26: Background Trace Element Concentrations in the Franciscan Complex, San Francisco, CA MS Thesis Defense Megan Simpson March 16, 2004 MS Thesis Defense Megan.

Statistical TestingStatistical Testing

• If data is ‘normally distributed’, randomly collected, Student ‘t’ test can be used

• If data is not ‘normally distributed’, Mann-Whitney U test is appropriate

• Tests on Schlocker data showed data not not normally distributed, therefore Mann-Whitney U analyses most appropriate to demonstrate significant differences between datasets

• If data is ‘normally distributed’, randomly collected, Student ‘t’ test can be used

• If data is not ‘normally distributed’, Mann-Whitney U test is appropriate

• Tests on Schlocker data showed data not not normally distributed, therefore Mann-Whitney U analyses most appropriate to demonstrate significant differences between datasets

Page 27: Background Trace Element Concentrations in the Franciscan Complex, San Francisco, CA MS Thesis Defense Megan Simpson March 16, 2004 MS Thesis Defense Megan.

Mann-Whitney U TestMann-Whitney U Test

• Data obtained from two random samples (n1 and n2)

• Samples are combined, each value assigned a rank (smallest is rank 1, largest is rank n1+ n2)

• U statistic based on totals of ranks (Ta, Tb)

• The smaller value of either Ta or Tb, the greater the

evidence that samples from different populations

• Tests were performed using 95% confidence level (95% of all samples give interval that includes the mean, 5% would give interval that does not)

• Data obtained from two random samples (n1 and n2)

• Samples are combined, each value assigned a rank (smallest is rank 1, largest is rank n1+ n2)

• U statistic based on totals of ranks (Ta, Tb)

• The smaller value of either Ta or Tb, the greater the

evidence that samples from different populations

• Tests were performed using 95% confidence level (95% of all samples give interval that includes the mean, 5% would give interval that does not)

Page 28: Background Trace Element Concentrations in the Franciscan Complex, San Francisco, CA MS Thesis Defense Megan Simpson March 16, 2004 MS Thesis Defense Megan.

HypothesisHypothesis

• Null hypothesis states:– ‘the difference between the mean ranks of

the datasets is not statistically significant’– OR

– average level of specific trace element found in given rock type in Schlocker’s data is not statistically different from average level of same element, same rock type found in my data

• Null hypothesis states:– ‘the difference between the mean ranks of

the datasets is not statistically significant’– OR

– average level of specific trace element found in given rock type in Schlocker’s data is not statistically different from average level of same element, same rock type found in my data

Page 29: Background Trace Element Concentrations in the Franciscan Complex, San Francisco, CA MS Thesis Defense Megan Simpson March 16, 2004 MS Thesis Defense Megan.

Comparison of Trace Element Levels between Schlocker and Simpson Datasets using Mann Whitney TestComparison of Trace Element Levels between Schlocker and Simpson Datasets using Mann Whitney Test

ChromiumChromium

•significant differences seen in serpentinite (means of 564 vs. 1384 mg/kg) and chert (means of 3 vs. 22 mg/kg) data

•no significant differences seen in greenstone and sandstone

ChromiumChromium

•significant differences seen in serpentinite (means of 564 vs. 1384 mg/kg) and chert (means of 3 vs. 22 mg/kg) data

•no significant differences seen in greenstone and sandstone

CobaltCobalt

•significant differences seen in sandstone (means of 25 vs. 7 mg/kg) and serpentinite (means of 59 vs. 81 mg/kg)

•no significant differences seen in chert and greenstone

Page 30: Background Trace Element Concentrations in the Franciscan Complex, San Francisco, CA MS Thesis Defense Megan Simpson March 16, 2004 MS Thesis Defense Megan.

NickelNickel

•significant differences seen in all rock types: chert (means of 43 vs. 22 mg/kg), greenstone (means of 180 vs. 46 mg/kg), sandstone (means of 57 vs. 27 mg/kg), serpentinite (means of 3000 vs. 1773 mg/kg)

LeadLead

•significant differences seen in chert (means of 0.25 vs. 40 mg/kg) and sandstone (means of 2.6 vs. 14 mg/kg)

•no test on greenstone and serpentinite

StrontiumStrontium

•significant difference seen only in chert (means of 5 vs. 38 mg/kg)

Page 31: Background Trace Element Concentrations in the Franciscan Complex, San Francisco, CA MS Thesis Defense Megan Simpson March 16, 2004 MS Thesis Defense Megan.

ANOVAANOVA

• Determines significant differences in the means of two or more datasets

• Performed on my data comparing means of same trace element between four rock types– Data is normally distributed, equal

variances, from randomly collected samples

• Null hypothesis: means of sample populations are statistically equal

• Determines significant differences in the means of two or more datasets

• Performed on my data comparing means of same trace element between four rock types– Data is normally distributed, equal

variances, from randomly collected samples

• Null hypothesis: means of sample populations are statistically equal

Page 32: Background Trace Element Concentrations in the Franciscan Complex, San Francisco, CA MS Thesis Defense Megan Simpson March 16, 2004 MS Thesis Defense Megan.

Mean (mg/kg) and Standard Deviation for each rock type in conjunction with ANOVA resultsMean (mg/kg) and Standard Deviation for each rock type in conjunction with ANOVA results

a Identical letters indicate no significant difference at the 95% confidence level.b,c Non-identical letters indicate a significant difference at the 95% confidence level

• Chromium and nickel concentrations are ~15-35 times higher in serpentinite

Page 33: Background Trace Element Concentrations in the Franciscan Complex, San Francisco, CA MS Thesis Defense Megan Simpson March 16, 2004 MS Thesis Defense Megan.

Trace Element Distribution MapsTrace Element Distribution Maps

• Created to illustrate levels of trace elements throughout San Francisco

• Within sampled areas, data is accurate

• Outside of sampled areas (west, upper northeast, southeast corners) data is interpolated

• ArcInfo/ArcMap 8.3 Inverse Distance Weighted (IDW) interpolation method– assumes each sample point has a local influence that

decreases with distance

• Created to illustrate levels of trace elements throughout San Francisco

• Within sampled areas, data is accurate

• Outside of sampled areas (west, upper northeast, southeast corners) data is interpolated

• ArcInfo/ArcMap 8.3 Inverse Distance Weighted (IDW) interpolation method– assumes each sample point has a local influence that

decreases with distance

Page 34: Background Trace Element Concentrations in the Franciscan Complex, San Francisco, CA MS Thesis Defense Megan Simpson March 16, 2004 MS Thesis Defense Megan.

N

Chromium Distribution Map

Page 35: Background Trace Element Concentrations in the Franciscan Complex, San Francisco, CA MS Thesis Defense Megan Simpson March 16, 2004 MS Thesis Defense Megan.

Cobalt Distribution Map

Page 36: Background Trace Element Concentrations in the Franciscan Complex, San Francisco, CA MS Thesis Defense Megan Simpson March 16, 2004 MS Thesis Defense Megan.

Strontium Distribution Map

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Lead Distribution Map

Page 38: Background Trace Element Concentrations in the Franciscan Complex, San Francisco, CA MS Thesis Defense Megan Simpson March 16, 2004 MS Thesis Defense Megan.

Nickel Distribution Map

Page 39: Background Trace Element Concentrations in the Franciscan Complex, San Francisco, CA MS Thesis Defense Megan Simpson March 16, 2004 MS Thesis Defense Megan.

ConclusionConclusion• This study:

– enhances understanding of background trace element distribution in Franciscan Complex

– will assist in development of future environmental clean-up studies

– expands trace element database

• Improvements to this dataset:– increasing sample size/location– examining other trace elements– sampling soil

• This study: – enhances understanding of background trace element

distribution in Franciscan Complex– will assist in development of future environmental

clean-up studies– expands trace element database

• Improvements to this dataset:– increasing sample size/location– examining other trace elements– sampling soil