Using Stable Isotope Ratio Analysis to Distinguish

Perchlorate Sources

Paul B. Hatzinger, Ph.D. Shaw Environmental, Inc.

03/30/2011

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4. TITLE AND SUBTITLE Using Stable Isotope Ratio Analysis to Distinguish Perchlorate Sources

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Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18

2

Perchlorate Contamination in the United States:

Historical

Military and Aerospace Issue

• Rocket Testing• Hog-Out• Manufacturing• Training Areas• OB/OD Areas• Few Commercial Sites

Limited Sources

3

Perchlorate Detections in the United States (2005)

Map source: US EPA

One siteMultiple sites

DODDOE, NASA, DOIPrivately-owedUCMR detectionsUniversity study detections

Legend

Puerto Rico

* Lower Detection Limits - 1998

* UCMR Testing - 2001

4

A. Natural Perchlorate1. Chilean Caliche – Atacama Desert

- natural nitrogen fertilizer2. Mineral deposits – Death Valley, CA3. Southwest soils and groundwater

B. Other Anthropogenic1. Fireworks2. Road Flares3. Perchloric Acid and Reagents4. Chlorate (herbicide) 5. Chlorine Bleach

Sylvinite (NM)

Other (Non-Military)Sources??

Chilean Nitrate

Uses Critical N fertilizer during 19th & early

20th C (cotton, tobacco and citrus) Explosives manufacture

Perchlorate Source 1910-1960

US imported 109kg fertilizer /year 0.2% ClO4

- (highly variable) 106kg ClO4

- /year

Historical Impact Citrus or cotton ~50 mg/m2-year Possible large local Impacts

* Dasgupta, PK, et al. 2006. Perchlorate in the United States. Analysis of Relative source contributions to the Food Chain. Environ. Sci. Technol. 40;6608-6614

6

Perchlorate Sources

Indigenous Perchlorate* Natural nitrate deposits* Perchlorate in soils* Perchlorate in groundwater & rainwater

• Atmospheric formation with O3• Other mechanisms – UV, TiO2

Natural Perchlorate in the USA

Death Valley Nitrate Deposits

< 0.

1

0.1

- 1.0

1.0

-10.

0

10.0

- 10

0.0

> 10

0

% D

ata

Poin

ts

0

2 0

4 0

6 0

8 0

Concentrations in in Western USGroundwater

Perchlorate ug/l

Courtesy of Dr. W. Andrew Jackson,Texas Tech

• Study area >59,000 mi2• 89% > 0.1 ppb• Estimated Mass of ClO4

-

– Saturated >2 X 106 Kg

West Texas –Southern High Plains

(ClO)x+O2→ClO4-

µV

(ClO)x+O3 → ClO4-

DepositionDry &WetEvapotranspiration

ClO4- AccumulationPlant uptake

ClO4-

ClO4- Flushing

Evapotranspiration

Re-concentration

Land Use Change

ClO4-

Dep

th (M

)

0

5

10

15

20

0 50 100 150 200

PerchlorateChloride Nitrate D

epth

(M)

0

5

10

15

20

0 50 100 150 200

PerchlorateChloride Nitrate

10

Can You Distinguish Natural from Synthetic Perchlorate?

Stable Isotope Ratio Analysis of Chlorine and Oxygen in Perchlorate

•Other Lines of Evidence- 36Cl Analysis- Groundwater Dating - Co-Contaminants- Other Geochemical Data

Methods developed for analysis of both chlorine and oxygen isotopes in perchlorate. Dual isotope comparisons possible.

Analyzed by IRMS with a precision of about ± 0.1 to 0.4‰

Sample preparation is critical. Methods have been developed to collect, recover, and purify perchlorate.

Stable Isotope Ratio Analysis: Perchlorate

ClO4-

3516

16

1616 16 16

6

Hydrogen 1H, 2HOxygen 16O, 17O, 18OCarbon 12C, 13CChlorine 35Cl, 37Cl Nitrogen 14N, 15NSulfur 32S, 34S

Elements in a compound can have widely different isotopic ratios based on mode of formation (e.g.,18O in NO3 from nitrification vs. atmospheric). Stable isotope ratios can provide a unique “fingerprint”

Cl O

Stable Isotope Analysis: Perchlorate

Sample Collection (5-10 mg)

ClO4- on IX

resin (NO3-,

SO42-, ReO4)

Preserved with HCland 4oC

Leach with 1M FeCl3 + 4MHCl (FeCl4) -collect fractions

Sample Extraction & Purification

0 1 2 3 4 50

5000

10000

15000

20000

25000

Sulfate

SO42-

des

orbe

d (m

g/L

)

Bed Volume

0

200

400

600

800

1000

Perchlorate Nitrate

NO

3- or

ClO

4- (mg/

L)

Leach with 4M HCl to remove NO3

- & SO42-,

CO3- & some humics

0 1 2 3 40

250

500

750

1,000

Perchlorate

Flow = 0.5 gal/min

ClO

4- des

orbe

d (m

M)

Bed Volume

0

100

200

300

400

500 Nitrate Sulfate

NO

3- or

SO42-

(mM

)

* Neutralize -Remove FeO3* Concentrate ClO4 supernatant* Filter unwanted precipitates * Crystallize ClO4 as CsClO4 or KCO4* Wash crystals with MeOH

Verification of Purity

40060080010001200

1085

1110

627

460

332

937 Sample-1

Sample-2 Sample-3

Inte

nsity

(a.u

.)

Raman shift (cm-1)

970

a

Crystal morphologyIon chromatography(lg sample)Micro-Raman spectroscopy

Impurity detected

IRMS – 18O/17O

Weigh crystal18O: Combust to CO(18O & 17O): decompose to O2IRMS (CO & O2)Measure yieldsDetermine O isotope ratios

IRMS – 37Cl

Weigh crystalCombust to Cl saltConvert to CH3ClPurify via GCIRMSDetermine Cl isotope ratio

Cl-

13

Terminology:*Isotopic compositions of light elements are generally reported as “delta” ()

values in parts-per-thousand (denoted “‰” = per mil) deviations (enrichments or depletions) relative to a known standard

Equation 1. (in ‰) = (Rx/Rs-1) * 1000R = ratio heavy/light isotope (e.g., 37Cl/35Cl)Rx = sample (e.g., 37Cl/35Cl in environmental sample)Rs = standard (e.g., 37Cl/35Cl in chlorine standard “SMOC”)

* Example: 37Cl = + 30 ‰30 parts-per-thousand (3 %) more 37Cl in sample relative to a known

standard (Standard Mean Ocean Chloride; SMOC). (18O = SMOW)

Terminology:Stable Isotope Ratio Analysis

7

-20

-15

-10

-5.0

0.0

5.0

-30 -25 -20 -15 -10 -5 0 5 10

Laboratory SaltsMilitaryHerbicidesGunpowderFireworksRoad FlaresTaiwaneseNatural (Chile)

37C

l (p

er m

il)

18O (per mil)

Forensic Isotopic Analysis: Chilean vs. Synthetic37Cl and 18O

Chlorine markedly “heavier” in syntheticperchlorate (n = 43).

Oxygen consistently“heavier” in natural (Chilean) perchlorate (n = 13).

37Cl: 0.5 + 1.0

37Cl: -12.6 + 1.5

18O: -17.5 + 2.7

18O: -6.7 + 2.2

9

Synthetic

Natural-Chilean(Mineral & fertilizer)

-4.0

-2.0

0.0

2.0

4.0

6.0

8.0

10

12

-30 -25 -20 -15 -10 -5 0 5

1

7O

(pe

r m

il)

18O (per mil)

mass-dependentfractionation

Forensic Isotopic Analysis: Chilean vs. Synthetic17O and 18O

Chilean perchlorateExcess 17O (n = 13)

Synthetic perchlorate “mass dependent”fractionation (n = 43)

17O: + 9.3 + 0.7Range: 7.9 to 10.5

17O: 0.01 + 0.06Range: - 0.24 to 0.11

Synthetic

Natural-Chilean

17O = ~ 0.52 x 18O

17O = 17O -0.52 x 18O (= O)

Bohlke, J.K., N.C. Sturchio, B. Gu, G.M. Brown, J. Horita, W. A. Jackson, J. Batista, and P. B. Hatzinger. 2005. Perchlorate isotope forensics. Analytical Chemistry, 77; 7838-7842.

-10

-5.0

0.0

5.0

10

-26 -24 -22 -20 -18 -16 -14 -12 -10

37C

l

18O

Can You Differentiate Synthetic Sources?

1. There are some isotopic differences between manufacturers – but only in 18O.

2. H2O is the source of oxygen in synthetic perchlorate and 18O in H2O varies globally.

3. Small dataset - batch to batch variation?- variation with time?- different “sources” in products

(e.g., flares)?

Utah Nevada China

Oregon

17

Groundwater: Long Island Case Study

Perchlorate isotopesNitrate isotopes

Major ions, trace elementsDissolved gases

Groundwater dating

North Fork(Depot Lane)

Westhampton(BOMARC)

Northport(SCWA)

Preliminary data (2007) **not for distribution**

Analytical: 7 Wells

SCWA

Preliminary data (2007) **not for distribution**

Depot Lane

BOMARC

SCWA

-20

-16

-12

-8.0

-4.0

0.0

4.0

8.0

-30 -25 -20 -15 -10 -5 0 5 10

37C

l (p

er m

il)

-4.0

-2.0

0.0

2.0

4.0

6.0

8.0

10

12

-30 -25 -20 -15 -10 -5 0 5 10

1

7O

(pe

r m

il)

18O (per mil)

mass-dependentfractionation

North Fork(Depot Lane)

Westhampton(BOMARC)

Northport(SCWA)

SyntheticBomarc

ChileanSCWA/DL

ChileanSCWA/DL

SyntheticBomarc

20Case Study: Long Island, NY

Long Island, NYDepot Lane Transect

0 500 1000 1500

Distance from DL6 (m)

-40

-30

-20

-10

0

10

20

Ele

vatio

n (m

) 13.6

8.6

8.9

1.0

1.1

6.3

9.1

8.0

8.0

0.9

1.0

4.5

0.10.3

9.9

0.8

0.6

4.6

DL1 DL4DL6

Pleistocene clay confining layer

Northwest Southeast

Upper glacial aquifer

Water table

Nearrecharge

basin

NO3--N ClO4-(mg/L) (µg/L)GW flow

1

40

Age(yrs)

18

AnthropogenicLong Island, NYAmherst, MAEdwards AFB, CAHenderson, NVSouthern California (2)Elkton, MDDahlgren, VAIsrael

Chilean FertilizerLong IslandSouthern California (3 )New Jersey

Mixtures:Southern California (2)

Comparison of 37Cl and 18O of perchlorate in groundwater from to synthetic solids and natural Chilean sources

Comparison of 18O and 17O of perchlorate in groundwater to various synthetic solids and natural Chilean sources

-20

-16

-12

-8.0

-4.0

0.0

4.0

8.0

-30 -25 -20 -15 -10 -5 0 5 10

37C

l (p

er m

il)

18O (per mil)

Isotope Results: Groundwater Data from Various Sites Compared to Chilean and

Synthetic Sources

-5.0

0.0

5.0

10

15

-30 -25 -20 -15 -10 -5 0 5 10

17O

(pe

r m

il)18O (per mil)

synthetic

Chilean

synthetic

Chilean

Mixtures Mixtures

Death Valley Caliche

Rio Grande Basin Groundwater (Ancient)

SHP Groundwater and Vadose Soil

Indigenous NaturalPerchlorate

-20

-16

-12

-8.0

-4.0

0.0

4.0

8.0

-30 -20 -10 0 10 20 30

37C

l (p

er m

il)

18O (per mil)

Synthetic

Chilean

Southern High PlainsTexas GWTexas Soil

Rio Grande, NM GW

Death Valley caliche

Comparison of 37Cl and 18O in perchlorate from indigenous US sources with Chilean and synthetic perchlorate.

Indigenous Perchlorate: 37Cl and 18O

1. There are multiple signatures for natural perchlorate but all are readily distinguished from synthetic sources via 37Cl and 18O.

2. West Texas vadose (soil) perchlorate has a similar isotope signature to that inWest Texas & NM groundwater.

Chilean caliche & fertilizer, and GW

-5.0

0.0

5.0

10

15

20

-20 -10 0 10 20 30

1

7O

(pe

r m

il)

18O (per mil)

Synthetic

Chilean Death Valleycaliche

Southern High PlainsWT GW

West Texas SoilRio Grande, NM GW

Comparison of 17O and 18O in perchlorate from indigenous US sources with Chilean and synthetic perchlorate.

Indigenous Perchlorate: 17O and 18O

17O: + 0.4 + 0.2

18O: 2.6 + 1.5

17O: 12.7 + 4.2

1. Like Chilean samples, Death Valley deposits have significant excess 17Oin perchlorate.

2. SHP soil and groundwater has only slight 17O excess –no difference between saturated and unsaturated zone??

3. Understanding the origin of natural perchlorate (and the resulting isotope values) is currently the subject of significant research.

Perchlorate Origin - Why different signatures?

Understanding of Natural Perchlorate Origin: Why is 17O so low in SHP Perchlorate ?

(1) Different reaction mechanism and/or location. - Ozone vs. UV reaction? - Atmosphere vs. surface catalyzed? - What does 36Cl tell us?

(2) Post-depositional modification. - Does oxygen in perchlorate exchange

with water?- Role of plants or microorganisms?

(ClO)x+O2→ClO4-

µV

(ClO)x+O3 → ClO4-

ClO4

ClO4

ClO4

ClO4

H2O

17O18O

Perchlorate generated with O3

-5.0

0.0

5.0

10

15

20

-30 -20 -10 0 10 20 30

17

O (

per

mil)

18O (per mil)

Synthetic solids

Atacama caliche/fertilizer

Death Valley caliche

West Texas

OCl- + O3

ClO2 + O

3

-5.0

0.0

5.0

10

15

20

-30 -20 -10 0 10 20 30 40 50

1

7O

(pe

r m

il)

18O (per mil)

Synthetic solids

Atacama caliche/fertilizer

Death Valley caliche

West Texas

OCl- + UVClO

2 + UV

Perchlorate generated with UV

36Cl Analysis

Long-lived radioisotopeproduced in the stratosphere from 40Ar(T1/2 = ~ 301,000 yrs)

36Cl/Cl = ~ 700 x 10-15

Analyzed by AcceleratorMass Spectrometry (AMS)

Analyzed purified perchlorate samples- Southwest US- Atacama- Synthetic

1. Southwest perchlorate (SHP and DV) significantly enriched in 36Cl –Irrespective of 17O.

2. Suggests significant component of “young” atmospheric perchlorate.

3. Atacama most likely “old” atmosphericperchlorate

Sturchio N.C., Caffee M.R., Beloso A. D., Heraty L.J., Böhlke J.K., Gu B., Jackson W.A., Hatzinger P.B., Heikoop J.R., and Dale M., 2009. Chlorine-36 as a tracer of perchlorate origin. Environmental Science & Technology 43, 6934–6938.

Atacama

Southwest US

Synthetic

Perchlorate Forensic Analysis: Summary25

When perchlorate is detected at low concentrations (< 10 g/L) in groundwater, natural sources should be considered.

Isotope analyses (37Cl, 18O, 17O and 36Cl/Cl) can be used to distinguish between synthetic and natural sources – Four independent measurements.

Natural perchlorate (from Chilean fertilizer and from “indigenous” sources) has been detected in numerous wells in the US via isotope analysis.

A “Guidance Manual” for perchlorate isotope sampling is presently under development by SERDP/ESTCP.

Contact Information

Paul Hatzinger, Ph.D.Shaw Environmental IncPaul.hatzinger@shawgrp.com1-609-895-5356

Neil C. Sturchio, Ph.D.University of Illinois at ChicagoChicago, ILTel. (312) 355-1182sturchio@uic.edu

ER-0509 Project Team

John Karl Bohlke, Ph.D.US Geological SurveyReston, VA(703) 648-6325jkbohlke@usgs.gov

Baohua Gu, Ph.D.Oak Ridge National Lab Oak Ridge, TN(865)-574-7286gub1@ornl.gov

We gratefully acknowledge SERDP and ESTCP for supporting this work