Facilitating Probabilistic Characterization Factors for Emerging Contaminants

Alex Cano, Dr. Valentina Prado, Dr. Thomas Seager, Ben WenderMS Graduate Student

May 19, 2015

Traditional Life Cycle Assessment

Material &energy inputs

Emissions to air, water & soil

Raw materials

Manufacturing

Product use

End of life

Recycling

Per Functional Unit

?

[CTUe ≡ PAF m3 day / kg] = [day] [%] [PAF m3 / kg]

FFmolecular weightoctanol-water part. coef.carbon-water part. coef.henry's law coef.vapor pressuresolubilitydisol. carbon-water part. coef.degredation rates; air, water…bioaccumulation factor

Multi species toxicology indicator

Multi-media nested box models

Material parameters

surv

ival

concentration

Species 1 2 3

PAF

Current practices in LCA are retrospective

Current practices in LCA are retrospective

USETox Characterization Factor Calculation

Early estimates for freshwater ecotoxicity CFs for CNTs demonstrate high uncertainty

0 20K 40K 60K0

50u

25u

75u

CF

Proba

bility

Dens

ity

Characterization factor value, [CTUe ≡ PAF m3 day/ kg]

CNT, worst case, Eckelman 2012~29,000 CTUe

CNT, realistic, Eckelman 2012~3,700 CTUe

MWCNT, Rodriguez 2014~750 CTUe

SWCNT, Rodriguez 2014 ~.125 CTUe

Partly due to high parameter uncertainty and lack of consensus regarding key properties

USETox designed to operate with point values

fr.waterC6.60E+01 [CTU e = PAF.m 3 .d.kg emitted

-1 ]

Parameter inputs →

CF output →

Misrepresents certainty of results

Provides no indication of CF sensitivity to input parameters

USETox Analysis through Probabilistic Distributions

Probabilistic Operation

0 20K 40K 60K0

50u

25u

75u

CF

Pro

bab

ility

Den

sity

CNT FW ecotox CF [CTUe]

Rela

tive

Cont

ributi

on

b

Rotenone ~70K

TCE ~ 80

Prob

abili

ty D

ensit

y

Developing CFs for DNAN: Army Corps of Engineers

Data provided by ERDC used to build uniform distributions for USETox-required parameters and program operated stochastically

Parameter Units Modeled as References

MW g/mol Point value: 183 Chemical formula

Kow [none] Uniform: 43 to 83 Boddu et al, 2008

Koc [L/kg] Uniform: 158 to 1258 ERDC/CRREL TR-14-23

Kh Pa m3 / mol Uniform: 1.5e-5 to 6.5e-5 EPIsuite & USETox QSARs; Boddu et al, 2008

Pvap Pa Uniform: 1.5e-3 to 9.2e-3 EPIsuite & USETox QSARs

Sol mg/L Uniform: 248 to 304 Taylor et al, 2013; Taylor et al 2015; +/-10%

Kdoc L/kg Uniform: 2.7 to 3.3 USETox QSAR, +/- 10%

Kdeg, air

1/s

Uniform: 2.2e-6 to 2.7e-6

EPIsuite, +/- 10%Kdeg, water

Uniform: 2.6e-6-2.6e-7Kdeg, soil

Kdeg, sed

Ave log LC50 Log (mg/L) Uniform: 1 to 1.2 ERDC/EL TR-13-2; Private communication

BAF fish L/kg Uniform: 1.9 to 4.4 EPIsuite & USETox QSARs

Fate factor represents the residence time in freshwater column for which DNAN is bioavailable and is obtained from multi media box model

Freshwater fate factor, [day]

Freq

uenc

y di

strib

ution

Toluene, <5 day

Tetrachloroethylene ~ 5 day

Trinitrotoluene (TNT) ~ 50 day

• Despite uncertainty, DNAN has shorter residence time in freshwater than TNT

Freshwater ecotox. effect factor, [PAF m3 / kg]

Freq

uenc

y di

strib

ution

Toluene, ~15 PAF m3 / kg

Trinitrotoluene (TNT) ~190 PAF m3 / kg

Effect factor represents toxicological response of aquatic organisms based on aggregated data from multiple species and trophic levels

• Despite uncertainty, DNAN has lower aggregate toxicity than TNT

Freshwater ecotoxicity characterization factor, [CTUe ≡ PAF m3 day / kg]

Freq

uenc

y di

strib

ution

Toluene, ~56 CTU

Tetrachloroethylene ~607 CTU

Trinitrotoluene (TNT) ~9400 CTU

Characterization factor represents time and space integrated aquatic ecotoxicity impacts per kg released DNAN

• Despite uncertainty, DNAN has much lower aquatic ecotox potential than TNT

Rank correlation analysis identifies those uncertainties most influential to CF results, in the case of DNAN uncertainty in fate-relevant parameters

Relative influence on CF uncertainty

EF

FF

XF

• Exposure factor contributes little, is effectively same as for TNT• DNAN exhibits significant reductions in aquatic ecotoxicity

potential compared to TNT• Need to revisit assumptions and distributions and get further

granularity in sensitivity analysis

• Representing both TNT and DNAN• Probability distribution

• Calculate overlapping area

Next Step

Freshwater ecotoxicity characterization factor, [CTUe ≡ PAF m3 day / kg]Freq

uenc

y di

strib

ution

Trinitrotoluene (TNT) ~9400 CTU

• United States Army Corps of Engineers • Research and Coordination Network

Thank you & Questions