PlasticPlastic FilmFilm PermeabilityPermeability toto FumigantsFumigants HuseinHusein A.A. AjwaAjwa andand WonsookWonsook HaHa UniversityUniversity ofof CaliforniaCalifornia--Davis,Davis, Salinas,Salinas, CACA IntroductionIntroduction Plastic tarp (film) is usually used to reduce fumigant volatilization losses from soil. Quantifying fumigant mass transfer through plastic films is important for the development of practical management practices to reduce volatilization losses and enhance weed and pathogen control. VIFVIF VirtuallyVirtually impermeableimpermeable filmfilm PE Polyamide PE VIF film is about 200 to 300 times less permeable to methyl bromide than HDPE TIFTIF TotallyTotally impermeableimpermeable filmfilm PE ADMER™ Adhesive EVAL™ resin ADMER™ PE Adhesive New film by Eval/Mitsui that was tested recently The film is 1.38 mil multilayer with an EVAL™ resin SIFSIF SemiSemi--impermeableimpermeable filmfilm Semi-impermeable LDPE Polymer PE LDPE Tri-extruded, low density polyethylene film RelativeRelative PlasticPlastic PermeabilityPermeability Tarping can change film permeability FilmFilm permeabilitypermeability afterafter tarpingtarping /hr) 14 2 Watsonville Santa Maria 12 Oxnard 10 8 6 4 2 Relative permeability to MB (mg/m permeability Relative 0 VIF 1 VIF 2 SIF HDPE Rimini Klerk's ObjectiveObjective TheThe objectiveobjective ofof thisthis studystudy waswas toto determinedetermine filmfilm (tarpaulin)(tarpaulin) permeabilitypermeability toto fumigantsfumigants (as(as massmass transfertransfer coefficient,coefficient, MTC)MTC) forfor commercialcommercial filmsfilms usedused inin strawberrystrawberry andand cutflowercutflower productionproduction systems.systems. MeasuringMeasuring FilmFilm PermeabilityPermeability FourFour soilsoil fumigantsfumigants werewere tested:tested: methylmethyl bromidebromide (MB),(MB), iodomethaneiodomethane (IM),(IM), 1,31,3--DichloropropeneDichloropropene (1,3(1,3--D),D), andand chloropicrinchloropicrin (CP).(CP). TheThe permeabilitypermeability ofof commercialcommercial filmsfilms toto fumigantfumigant vaporsvapors waswas measuredmeasured usingusing staticstatic sealedsealed chamberschambers atat 2020 ±± 22oC.C. Plastic Permeability Measurement Plastic film is mounted between two chambers. Fumigant is applied to the lower chamber. Plastic Permeability Measurement Fumigant is measured by GC in both chambers. The Mass Transfer Coefficient (MTC) was calculated. Diffusion of MB through standard LDPE 100 90 S-Modeled 80 Source (lower) chamber R-Modeled 70 S-Measured R-Measured 60 50 40 Relative con'c Relative 30 Receiving (top) chamber 20 10 0 012345678 Time [hr] Diffusion of MB through metalized film 100 90 Source (lower) chamber 80 70 60 S-Modeled 50 R-Modeled S-Measured 40 R-Measured Relative con'c 30 20 10 Receiving (top) chamber 0 012345678 Time [hr] Diffusion of MB through Bromostop VIF 100 90 Source (lower) chamber 80 70 60 S-Modeled 50 R-Modeled S-Measured 40 Relative con'c Relative R-Measured 30 20 10 Receiving (top) chamber 0 012345678 Time [hr] MassMass TransferTransfer CoefficientsCoefficients (cm/h)(cm/h) (High(High permeabilitypermeability film)film) Cis Trans Film type MB IM CP 1,3-D 1,3-D Pliant black embossed 4.57 4.11 18.12 18.94 10.95 (1.25 mil) Pliant white/black white/black 4.48 3.09 17.21 17.51 10.75 embossed (1.25 mil) MassMass TransferTransfer CoefficientsCoefficients (cm/h)(cm/h) (Low(Low permeabilitypermeability film)film) Cis Trans Film type MB IM CP 1,3-D 1,3-D PolyPak Std 4.95 0.46 3.80 5.28 1.60 (1.5 mil) PolyPak SIF 0.82 0.42 1.42 1.50 0.67 (2.0 mil) Metalized /stripe 3.53 0.55 3.84 5.68 1.67 (1.3 mil) Metalized /shiny 2.61 0.50 4.82 6.02 2.24 (1.3 mil) MassMass TransferTransfer CoefficientsCoefficients (cm/h)(cm/h) (Impermeable(Impermeable film)film) Cis Trans Film type MB IM CP 1,3-D 1,3-D Pliant (B-A) 3.60 0.02 1.17 2.28 0.22 (1.25 mil) C&B, micro- embossed 4.42 0.02 0.86 1.65 0.11 (1.25 mil) T&F, micro- embossed 3.05 0.04 1.18 1.51 0.21 (1.25 mil) MassMass TransferTransfer CoefficientsCoefficients (cm/h)(cm/h) (Virtually(Virtually impermeableimpermeable film)film) Cis Trans Film type MB IM CP 1,3-D 1,3-D IPM clear VIF 0.13 0.01 0.17 0.36 0.001 (1.38 mil) Bromostop 0.18 0.02 0.16 0.32 0.05 VIF (1.38 mil) Eval/Mitsui film (1.38 mil) 0.20 < 10-13 < 10-13 < 10-13 < 10-13 TIF AverageAverage MassMass TransferTransfer CoefficientCoefficient forfor CPCP 8 7 6 ] 5 -1 4 [cm h [cm 3 2 1 0 Averaged mass transfer coefficient transfer mass Averaged High Low Impermeable VIF permeability permeability film Film permeability groups AverageAverage MassMass TransferTransfer CoefficientCoefficient forfor 1,31,3--D,D, andand CPCP 8 7 6 5 ] -1 4 [cm h [cm 3 2 1 0 Averaged mass transfer coefficient transfer mass Averaged High Low permeability Impermeable film VIF permeability Film permeability groups AverageAverage MassMass TransferTransfer CoefficientCoefficient forfor MB,MB, 1,31,3--D,D, andand CPCP 8 7 6 5 ] -1 4 [cm h 3 2 1 Averaged mass transfer coefficient 0 High Low permeability Impermeable film VIF permeability Film permeability groups SUMMARYSUMMARY TheThe averageaverage massmass transfertransfer coefficientcoefficient (MTC)(MTC) ofof IMIM waswas generallygenerally smallsmall forfor allall films,films, exceptexcept forfor thethe embossedembossed highhigh permeabilitypermeability film.film. TheThe averageaverage MTCsMTCs ofof allall otherother fumigantsfumigants were:were: • >> 44 cmcm hh-1 forfor highhigh permeabilitypermeability filmfilm • << 4.04.0 cmcm hh-1 forfor lowlow permeabilitypermeability filmfilm • << 2.02.0 cmcm hh-1 forfor impermeableimpermeable film,film, andand • << 0.20.2 cmcm hh-1 forfor VIF.VIF. Thank you very much AcknowledgementsAcknowledgements California Strawberry Commission USDA-ARS, PAW program USDA-CSREES PolyPak TriCal Mark Lauman Bruno Rimini Eval/Mitsui.