Characterization of 1233zd(E) leaching potential using numerical simulation

Transcription

1 Characterization of 1233zd(E) leaching potential using numerical simulation Michael K. Mrozik, Ph. D. 1 ; Sandeep Mukhi, Ph. D. 2 ; Daniel Perkins, Ph. D. 1 ; Kevin Wright 1 ; Gregg Hancock 3 ; Mark Cheplick 4 1 Waterborne Environmental Champaign, IL 2 Product Stewardship and Toxicology, Honeywell Performance Materials and Technologies, Morristown, NJ 3 Waterborne Environmental, Midland MI 4 Waterborne Environmental, Leesburg, VA 1

2 Motivation for research: better represent fate and transport of volatile compounds in real world conditions EPI Suite 1 and PRZM 2 approach Analysis from EPI Suite provides: Screening level evaluation of numerous chemical properties and environmental fate EPI Suite insufficiencies for volatile compounds Lacking consideration of complex intermolecular forces EPI Suite is not representative of volatile chemical fate under real world conditions To better characterize, a conservative but representative chemical transport and exposure model is needed PRZM. Refined modeling, such as PRZM, not a substitute for targeted exposure studies, but can better represent real environmental conditions 1 US EPA. [2012]. Estimation Programs Interface Suite for Microsoft Windows, v United States Environmental Protection Agency, Washington, DC, USA. 2 Suarez, L.A., PRZM-3, A Model for Predicting Pesticide and Nitrogen Fate in the Crop Root and Unsaturated Soil Zones: Users Manual for Release EPA/600/R-05/111 September 2006, Revision A. 2

3 Project Scope: - Simulate and characterize environmental fate of 1233zd(E) - Benchmark these properties against some well studied chemicals - Methyl-bromide (MeBr) - Trans-1,2- dichlorethylene (DCE) - Tri-chloroethylene (TCE) - Run simulations using Epi Suite and PRZM to determine mass partitioning behavior in different environmental compartments 3

4 Studies of TCE transport suggest: Transport to groundwater by molecular diffusion (a) (b) Adapted figures 2 from which details (a)large scale investigation into TCE transport and (b) temperature dependence at varying depths both experimentally and carrying out simulations. < 95% of applied TCE transferred to the atmosphere % of injected TCE was observed at outlet 2 Volatile concentrations did indicate greater volatility and gas phase concentration temperature dependence at greater depths 2 1 Schafer, G et al. J. Cont. Hydro. 2003, 60, Bohy, M. et al. Vadose Zone J. 2006, 5(2), ; 4

5 MeBr and DCE leaching behavior: MeBr: While methyl bromide has certain properties and characteristics in common with chemicals that have been detected in ground water (methyl bromide is highly soluble in water and has low adsorption to soil), volatilization is this chemical s most important route of dissipation. 1 DCE Volatilization is the major fate process when the chemicals are released to surface water, with an estimated half-life of about 3 6 hours. In soil, cis- and trans-1,2-dce may leach through the subsurface and contaminate groundwater. The chemicals may also be found in groundwater due to anaerobic degradation of more highly chlorinated chemicals, such as trichloroethylene and tetrachloroethylene. 2 1 US EPA. [2008]. Reregistration Eligibility Decision for Methyl Bromide (soil and non-food structural uses). United States Environmental Protection Agency, Washington, DC, USA. 2 US EPA [2010]. Toxicological Review of cis-1,2-dichoroethylene and trans- 1,2-dichloroethylene. United States Environmental Protection Agency, Washington DC, USA. 5

6 Relevant chemical properties MeBr t-dce TCE 1233zd(E) Molecular weight Boiling Point (Kelvin) Vapor Pressure (Pa) 2.18 x x x 10 3,β 1.07 x 10 5 Solubility (mg L -1 ) 1.75 x x x x 10 3 Henry s Constant (calc.) 4.85 x x x x 10 0 Sorption Partition Coefficient (log K oc ) Mackay, D. et al. Handbook of Physical Chemical Properties and Environmental Fate for Organic Chemicals, Hulse, R. J. et al. J. of Chem. & Eng. Data,2012, 57,

7 A Little more depth about 1233zd(E) (trans-1-chloro-3,3,3- trifluoropropene) History: CFC and HCFC usage and complications necessitated an environmentally preferable alternative Olefins have been developed as a contending alternative Intended Uses: Refrigerant Foam expansion agent Solvent Additional Properties: 1233zd(E) 2 atmospheric lifetime of 26 days Global warming potential (GWP) value of 1 1 Inventory of U.S. Greenhouse Gas Emissions and Sinks: , U.S. Environmental Protection Agency, Office of Atmospheric Programs, EPA 430- R , April zd(E) is marketed by Honeywell as Solstice Performance Fluid (honeywell-solvents.com) 7

8 Simulation Methods used: EPI Suite 1 Physical/chemical property and environmental fate estimation programs developed by the EPA s Office of Pollution Prevention Toxics and Syracuse Research Corporation (SRC). A screening-level tool EPI Suite used as an interface to run fugacity calculation Assigning rough partitioning through thermodynamic values determined in other EPI Suite programs Used to generate a baseline, but does not have scenario control to desired level of detail. PRZM 2 One-dimensional, finite-difference model that accounts for pesticide and nitrogen fate in the crop root zone. PRZM3 includes modeling capabilities include: soil temperature simulation volatilization and vapor phase transport in soils irrigation simulation microbial transformation method of characteristics (MOC) algorithm to eliminate numerical dispersion PRZM is capable of simulating transport and transformation of the parent compound and as many as two daughter species Probability-based exposure assessments utilize a pre-equipped Monte Carlo pre- and post-processor. 1 US EPA. [2012]. Estimation Programs Interface Suite for Microsoft Windows, v United States Environmental Protection Agency, Washington, DC, USA. 2 Suarez, L.A., PRZM-3, A Model for Predicting Pesticide and Nitrogen Fate in the Crop Root and Unsaturated Soil Zones: Users Manual for Release EPA/600/R-05/111 September 2006, Revision A. 8

9 EPI Suite: Fugacity estimates raise questions about model capability to adequately incorporate volatility MeBr DCE TCE 1233zd(E) Persistence Time (hr.) Reaction Time (hr.) Advection Time (hr.) Percent Reacted Percent Advected Mass Balance MeBr DCE TCE 1233zd(E) Air Water Soil Predicted reaction and persistent times indicate deviations from known behavior for each compound Standardized environmental system, excludes groundwater does not replicate desired system EPI Suite does not fully account for the complexity of molecular interactions that govern fate and transport within the system Lack of explicit dipole-dipole/ van-der waals interactions will limit true representations of complex systems Sediment These results represent a default model system that included default river and lake parameters (River parameters: 1m depth; wind velocity: 5 m s -1 ; current velocity: 1 m s -1. Lake parameters: 1m depth; wind velocity: 0.5 m s -1 ; current velocity: 0.05 m s -1 ) 9

10 PRZM model: a refined conservative approach beyond EPI suite Volatile compound enhancements from EPI suite: PRZM incorporates additional experimentally determined chemical properties: BP, VP, K OC, dynamic phase exchange Ground water specific environment: System and scenario specific controls can be adjusted to represent a highly conservative scenario Shallow water table 1 m to ground water Porous soil Sandy soil low organic carbon Weather that is least conducive to evaporation Rainfall conditions WI-Sweet Corn scenario 1 selected with crop parameter set to year long turf to simulate residential scenario Layout of generic sub-surface layers and ground water location relative to surface Figure adapted from original source: 10

11 PRZM Benchmarking for MeBr, DCE and TCE: 1 year 15 years Different time scales of each data set are shown on the same vertical axis at 1 year and at the full 15 year simulation, and color coded. 11

12 Looking at behavior over the first year for TCE: - A growing percentage of TCE volatilizes while a decreasing storage percentage, indicates limited soil adsorption forces - Majority of applied TCE either volatilizes or is stored over the first simulated year 12

13 Looking at behavior over the 15 year simulation for TCE: - Annual temperature and general weather fluctuations lead to periodic spikes visible over full 15 year simulation. - Over the 15 years simulated, the volatile and stored fractions dominate the mass balance - The volatile percentage appears to oscillates 90-95% of the applied TCE 13

14 1233zd(E) PRZM 15 year simulation results: - Periodic spikes in TCE are not as prevalent over the 15 year span for 1233zd(E) - Equilibration is rapid and nears asymptotic limit of 100% volatilized of applied 1233zd(E) 14

15 1233zd(E) PRZM 1 st year simulation results: - On the time scale of a single year, one can discern the individual spikes in concentrations due to application interval of 1 week - Response time for each application is much more rapid than other compounds studied - % Volatile and % Stored reach equilibrium nearly after 4 or 6 months 15

16 Under the conservative PRZM scenario (15 yr comparison): 99.77% Volatilized 93.96% Volatilized 0.35 % Stored in top 1m 0.04 % Stored in top 1m 1.71 % Leached 0.05 % Degraded 0.14 % Leached 3.98 % Degraded 1233zd(E) TCE Percent volatilized Percent storage (within 1 m) Percent degraded Percent leached (below 1 m) 1233zd(E) MeBr TCE DCE

17 Model Conclusions: 99.77% Volatilized 0.04 % Stored in top 1m Modeling data from PRZM suggests that: 1233zd(E) 0.05 % Degraded 0.14 % Leached PRZM represents a refinement to EPI Suite Better representation of real world condition Mass balance results generally agree with literature results TCE % Volatilized: ( 93.96% calculated, < 95% lit value) 1233zd(E): High volatility reproduced with PRZM This approach may be applicable for evaluation of environmental risk 17

18 Conclusion: Leaching Potential: 1233zd(E) < MeBr < TCE << DCE PRZM simulation results indicate that a small percentage of 1233zd(E) (~0.008 %) penetrates below 1m over 15 years simulated Smallest leached percentage of compounds studied DCE highest percentage leached 18

19 Waterborne Environmental Company Overview Service Areas Human & Environmental Risk Assessment Environmental Modeling Chemical fate and transport modeling Geospatial Information & Data Science Field Studies/ Monitoring Ecotoxicology/Toxicology Support Statistics & Data Analysis Registration Support Documentation Development of peer-review publications Incorporated March 1993 ~70 staff; experienced staff; many with MS or PhD level of education Success based on long-term client relationships since inception 19