Dimethylsilanediol Research Articles

Volatilization of dimethylsilanediol (DMSD) under environmentally relevant conditions: Sampling method and impact of water and soil materials

Dimethylsilanediol (DMSD) is the common breakdown product of methylsiloxanes such as polydimethylsiloxane (PDMS) and volatile methylsiloxanes (VMS) in soil. In this work, we first present a sorbent selection experiment aiming to identify a sorbent that can trap gas-phase DMSD without causing DMSD condensation and VMS hydrolysis at environmentally relevant humidities. With a proper sorbent (Tenax) identified, the volatilization of DMSD from water and various wet soil and soil materials were measured in a controlled environment. It was demonstrated that DMSD underwent volatilization after soil water was completely evaporated. Various types of soil constituents show drastic differences in preventing DMSD from volatilization. Analysis of the sorbent-captured products provides further insight, most notably that virtually no cyclic methylsiloxanes are formed during the volatilization of DMSD from water or soil materials, except in one extreme case where only traces are detected.

Fate of dimethylsilanediol (DMSD) in outdoor bare surface soil and its relation to soil water loss

Dimethylsilanediol (DMSD) is a primary degradation product of silicone materials in the environment. Due to its low air/water partition coefficient and low soil/water distribution coefficient, this compound is not expected to undergo sorption and volatilization in wet soil. In an accompanying paper, we confirm that under controlled indoor conditions in test tubes, there is little to no volatilization of DMSD from soil and soil constituents if soil is wet. However, a significant amount of DMSD was volatilized when the soil substrates became air dried. Given the importance of water on the partition and fate of DMSD, we now report a continuation of this study focusing on the relation between DMSD removal and water loss in re-constituted soil columns under outdoor conditions. Consistent with predictions based on its partition properties and reconciling this evidence with previously reported field and laboratory studies, DMSD distribution was found to be largely dependent on water partitioning. The results suggested that DMSD moved upward in soil profile as soil water was evaporated from topmost layers with little DMSD retention by the soil matrix. As soil dried, a fraction of DMSD was sorbed by the soil matrix in the topmost layer, while most of the spiked radio-labeled DMSD was removed from soil through volatilization.

Fate of dimethylsilanediol (DMSD) in soil-plant systems

Dimethylsilanediol (DMSD) is the degradation product of methylsiloxane polymers and oligomers such as volatile cyclic methylsiloxanes (cVMS). To better understand the environmental fate of this key degradation product, we conducted a three-part study on the movement of DMSD in soil. The objective of this third and final study was to determine the fate of DMSD in soil-plant systems under constant irrigation. Soil columns were constructed using two soils with the upper 20 cm layers spiked with 14C-labeled DMSD. Corn seedlings were transplanted into the soil columns and placed in a field plot underneath a transparent cover that prevented rainwater from reaching the soil columns while allowing soil water to be volatilized freely. The soil-plant columns were regularly irrigated with known amounts of DMSD-free plant growth solution to sustain the plant growth. At pre-determined time intervals (15–67 days), the plant and soil columns were sectioned and the distribution of 14Corganosilicon species in the soil profile and plant parts was determined using a combination of Liquid Scintillation Counting and High-Performance Liquid Chromatography-Flow Scintillation Analysis, while soil water loss was determined gravimetrically. It was found that the majority (>92 %) of DMSD initially spiked into the soil was removed from the soil-plant systems. Although DMSD was transported from the soil to the plant, it was subsequently volatilized from the plant via transpiration, with only a small fraction (∼5%) remaining at the conclusion of the experiments. In addition, little non-extractable DMSD was found in the top layer of soil in the soil-plant systems, suggesting that the air-drying of soil is a necessary pre-condition for the formation of such non-extractable silanol residue on topsoil.

Dimethylsilanediol from silicone elastomers: Analysis, release from biopharmaceutical process equipment, and clearance studies

Polysiloxanes are considered one of the most important commercial families of synthetic elastomers. They are frequently employed in biopharmaceutical manufacturing equipment as flexible single-use solutions due to superior material properties and compatibility with diverse sterilization methods. Extractables and leachables (E&L) testing is essential in qualifying such equipment, involving extraction studies to assess the potential release of compounds from plastic components for risk assessment. Silicone releases oligomeric siloxanes and small hydrolysis products, with dimethylsilanediol (DMSD) being the main hydrolysis product found in significant concentrations in aqueous process solutions. DMSD presents challenges for analysis, requiring specifically tailored analytical methods to detect it, which are commonly not applied in standard E&L screening tests. In biopharmaceutical manufacturing, it is relevant to consider the potential of DMSD to repolymerize into silicone oil when specific process parameters are altered. This may lead to interactions with drug ingredients, including proteins, resulting in the formation of aggregates. We synthesized and characterized DMSD using X-ray structure analysis and established an HPLC method with a refractive index detector to investigate the release of DMSD from commercially available silicone tubing used in drug manufacturing following autoclaving and irradiation. Subsequently, we assessed typical biopharmaceutical downstream operations for effectively removing this compound from the process stream.

Synthesis and flame retardant behavior of siloxane functionalized polyethylene

AbstractTo improve the flame retardancy of polyethyelene (PE), this work realized an effective in‐situ synthesis of siloxane functionalized PE via continuous process with two stages: in the first stage, reactive olefin monomers containing dichlorosilane group were designed and utilized in ethylene copolymerization catalyzed by Ziegler‐Natta catalyst; in the second stage, by injecting dimethylsilanediol (DMS) directly into the unterminated polymerization solution, siloxane was grafted onto PE side group via the reaction between the pendant chlorosilane groups on PE and hydroxyl on DMS. Owing to the carbonization effect of silica produced by siloxane combustion, the combustion residue of PE was significantly increased to 20.8 wt% in the TGA test after grafting 0.58 mol% DMS. The siloxane functionalized PE was then added into PE/magnesium hydroxide (MH) composites to investigate the materials burning behavior. By grafting 0.15 wt% siloxane, the limited oxygen index of PE was increased from 18% to 21% and that of PE/MH increased from 28% to 30%, indicating the flame retardancy of PE was improved with grafted siloxane modification. It was also found that the nanoscale silica in‐situ generated by the graft siloxane groups efficiently assisted the formation of a dense residual layer of MgO and amorphous carbon.

An in situ gas chromatograph with automatic detector switching between PTR- and EI-TOF-MS: isomer-resolved measurements of indoor air

Abstract. We have developed a field-deployable gas chromatograph (GC) with thermal desorption preconcentration (TDPC), which is demonstrated here with automatic detector switching between two high-resolution time-of-flight mass spectrometers (TOF-MSs) for in situ measurements of volatile organic compounds (VOCs). This system provides many analytical advances, including acquisition of fast time–response data in tandem with molecular speciation and two types of mass spectral information for each resolved GC peak: molecular ion identification from Vocus proton transfer reaction (PTR) TOF-MS and fragmentation pattern from electron ionization (EI) TOF-MS detection. This system was deployed during the 2018 ATHLETIC campaign at the University of Colorado Dal Ward Athletic Center in Boulder, Colorado, where it was used to characterize VOC emissions in the indoor environment. The addition of the TDPC-GC increased the Vocus sensitivity by a factor of 50 due to preconcentration over a 6 min GC sample time versus direct air sampling with the Vocus, which was operated with a time resolution of 1 Hz. The GC-TOF methods demonstrated average limits of detection of 1.6 ppt across a range of monoterpenes and aromatics. Here, we describe the method to use the two-detector system to conclusively identify a range of VOCs including hydrocarbons, oxygenates, and halocarbons, along with detailed results including the quantification of anthropogenic monoterpenes, where limonene accounted for 47 %–80 % of the indoor monoterpene composition. We also report the detection of dimethylsilanediol (DMSD), an organosiloxane degradation product, which was observed with dynamic temporal behavior distinct from volatile organosiloxanes (e.g., decamethylcyclopentasiloxane, D5 siloxane). Our results suggest DMSD is produced from humidity-dependent heterogeneous reactions occurring on surfaces in the indoor environment, rather than formed through gas-phase oxidation of volatile siloxanes.

Simultaneous removal of siloxanes and H2S from biogas using an aerobic biotrickling filter

The feasibility of simultaneous removal of siloxane and H2S from biogas was investigated using an aerobic biotrickling filter (BTF). The biodegradation of H2S in the BTF followed a first-order kinetic model and more than 95 % H2S was eliminated within a residence time of 0.3 min. The removal of decamethylcyclopentasiloxane (D5) increased with longer empty bed residence time (EBRT). The partition test and microbial community analysis further reveals that up to 52 % removal of D5 was reached mainly by the chemical-absorption in acid recycling liquid. Finally, D5 was converted into mixtures of dimethylsilanediol (DMSD) and hexamethyldisiloxane (L2) via ring-opening hydrolysis in acid liquid and ring-shrinking polyreaction using CH4 derived from biogas. These operational characteristics demonstrate that the abiotic removal of D5, in addition to biological removal of H2S in an aerobic BTF can significantly decrease the siloxane loading to the downstream siloxane removing units.

Removal, potential reaction pathways, and overall cost analysis of various pollution parameters and toxic odor compounds from the effluents of turkey processing plant using TiO2–assisted UV/O3 process

In the present study, removal of hazardous toxic odor compounds with color, COD and turbidity were concurrently investigated for the effluents of a turkey processing plant located in Bolu, Turkey. A hybrid TiO2-assisted photo-ozonation (UV/TiO2/O3) process was set to address this issue. Subsequently, a comprehensive GC/MS method was developed for quantification of odor compounds. Finally, a complete overall cost analysis was incorporated with the findings of the study to demonstrate an economic analysis of the process. Descriptive results showed that the effluents had high pollution content in terms of color (0.374 IU; b = −0.06), COD (146 mg/L O2) and turbidity (15.52 NTU). Moreover, dimethyl silanediol (DS, 34.3%), acetic acid (AA, 20.5%), and diisobutyl phthalate (DP, 32.5%) were determined as major odor compounds of the effluents. After UV/TiO2/O3 process, DS, AA, and DP were reduced to 12.4%, 12.0%, and 8.4%, respectively under the operating conditions of ozone dose of 16 mg/L, initial pH of 7.5, reaction time of 25 min, and catalyst dose of 3 g/L TiO2. At the same conditions removal efficiencies of color, COD and turbidity were obtained %99, %85, and 78%, respectively. These values demonstrated the accuracy of UV/TiO2/O3 process in terms of removal of hazardous odor compounds and the other pollution parameters. Studies on reaction mechanism showed that main degradation mechanism occurred in three ways: formation of long-chained cyclic compounds from DS (1), formation of acetamide and ammonium acetate from AA (2), and formation of phthallic acid from DP (3). Finally, overall cost analysis showed that the current process costed 0.014 $ per 1 L of treated effluent and this value showed that the current process met the economic criteria in terms of feasibility.

Decomposition of environmentally persistent cyclic methylsiloxanes in subcritical water

The cyclic methylsiloxanes octamethylcyclotetrasiloxane (D4) and decamethylcyclopentasiloxane (D5) were reacted in subcritical water at temperatures of 150–350 °C under argon, under O2, or in the presence of H2O2. When the reactions were performed in pure subcritical water (under argon) at 300 °C for 6 h, both D4 and D5 were almost completely hydrolyzed to water-soluble and hexane-non-extractable compounds such as dimethylsilanediol (DMSD). However, the high percentages of total organic carbon (TOC) remained in the aqueous phase [87% and 81% of the carbon atoms in the initial D5 (26.6 μmol) and D4 (30.6 μmol), respectively] and the low silicate yields (both 3% of the silicon atoms in the initial D5 and D4) indicated that little mineralization had occurred. Although the presence of O2 had no significant effect on the reactivity of these substrates in subcritical water at temperatures up to 300 °C, the presence of H2O2 enhanced the decomposition of these substrates. Raising the temperature to 350 °C greatly enhanced the mineralization. Specifically, when the reactions were performed in 2.0 M H2O2 for 2 h, the percentages of TOC that remained in the aqueous phase decreased markedly (to 2% and 10% of the carbon atoms in the initial D5 and D4, respectively) and IR spectral measurements indicated that most of the substrates had been oxidized to silicate.

Quantitative analysis of trace- and ultratrace-level Dimethylsilanediol (DMSD) in water, soil, sediment and biosolids by liquid chromatography-triple quadrupole tandem mass spectrometry

ABSTRACTDimethylsilanediol (DMSD) is a highly water-soluble degradation product of dimethylsiloxane oligomer and polymer materials that may be found in the environment. In this project, we have developed a water analysis method for DMSD based on liquid chromatography-triple quadrupole tandem mass spectrometry (LC/QQQ MS/MS) using 13C-DMSD as an internal standard with and without solid phase extraction (SPE). This included the modification of SPE extraction method for water samples with colloidal particles that may plug the SPE cartridge, the use of a water-based solvent mixture for DMSD elution to promote better ionisation in instrumental analysis and optimisation of instrumental operation conditions for higher sensitivity in QQQ MS/MS analysis. The water method was successfully applied for analysis of DMSD in soil, sediment and biosolids by coupling the water extraction of DMSD from solid samples with the pre-column SPE extraction of the water extracts. The method detection limit (MDL) for direct water analysis was found to be as low as 2 μg L−1, while the current MDLs for sediment, soil and biosolids are in the range of 10 to 100 ng g−1 dw. The matrix spike recovery varied from 79% to 99% for all samples, confirming its general validity of the method. Compared with the published methods, this method requires less sample processing and has lower MDLs for DMSD analysis in environmental samples.

Extraction and quantitative analysis of water by GC/MS for trace-level dimethylsilanediol (DMSD)

Dimethylsilanediol (DMSD) is related to the most important bifunctional building block for silicone oligomers and polymers, although DMSD itself is not used in any commercial applications. The environmental release of DMSD is linked to the hydrolytic degradation of other silicone materials in soil and water as DMSD is usually one of the major products. Most common extraction and quantification methods are not suitable for the analysis of trace- and ultratrace-levels of DMSD in water. This is because DMSD is highly water soluble and can readily undergo self-condensation when concentrated. In addition, DMSD may also coexist with DMSD precusors such methylsiloxanes in water. In the present study, solid-phase extraction (SPE) in combination with gas chromatography-mass spectrometry (GC/MS) without pre-column derivatization was tested for analyzing water samples for DMSD. It was found that direct analysis by GC/MS can be used for a wide range of concentrations if DMSD was extracted into a dry organic solvent. Isolute® ENV + may be used for such extraction at higher DMSD concentrations, while Supelclean™ ENVI-Carb™ Plus was found to be better for trace and ultratrace analysis. Increased salt content in water can increase its DMSD extraction efficiency, while polarity of the eluting solvents is a determining factor for eluting efficiency. Moisture in the final extract is a detrimental factor for direct GC/MS analysis. With a proper moisture removal procedure and a suitable internal standard, coupling of SPE and direct GC/MS analysis reduces the method detection limits for DMSD to lower ppb levels. Based on field sample analysis, solvent and instrumental background, not instrumental sensitivity, was found to be the limiting factor in lowering the detection limits for this analysis.

Acceptable Levels for Ingestion of Dimethylsilanediol in Water on the International Space Station

Water is recovered aboard the International Space Station (ISS) from humidity condensate and treated urine. The product water is monitored for total organic carbon (TOC). In 2010 the TOC readings indicated that a new contaminant had entered the potable water and was steadily increasing toward the TOC screening limit of 3 mg x L(-1). In a ground-based laboratory, chemists discovered that dimethylsilanediol (DMSD) was the principal new contaminant. As no standard existed for safe levels of DMSD in water, the Toxicology Office at Johnson Space Center was asked to set such a standard. The Toxicology Office used methods developed over the past decade, in collaboration with the National Research Council Committee on Toxicology, for setting Spacecraft Water Exposure Guidelines (SWEGs). These methods require a thorough literature search and development of an acceptable concentration (AC) for each potential toxic effect, keeping in mind that the adverse effects that accompany spaceflight could increase toxicity for certain end points. Benchmark dose modeling was encouraged if sufficient data were available. The most sensitive AC becomes the driver for the SWEG. Hematotoxicity, hepatotoxicity, and possibly neurotoxicity were the most sensitive toxicological endpoints for DMSD. The SWEG for DMSD for 100 d of ingestion was set at 35 mg x L(-1), which is equivalent to 9 mg x L(-1) as TOC. This is well above the TOC SWEG of 3 mg x L(-1) and the peak DMSD level of processed water observed on orbit, which was 2.2 mg x L(-1) asTOC (8.5 mg x L(-10 of DMSD).

Dimethylsilanediol: Structure and vibrational spectra by IR and Raman spectroscopies and quantum chemical calculations

Despite the predictable relation between the structure of the silanediol group and its biological activity (some peptidomimetics containing the R′R″Si(OH) 2 group have proven efficiency as inhibitors of aspartyl and metalloproteases), few theoretical or experimental works deal with the study of the structural and/or vibrational properties of this functional group. Thus, intending to overcome this lack of information, the present paper is focused on one of the simplest possible alkylsilanediols, namely, dimethylsilanediol (DMSD). In this way, a thorough quantum chemical analysis allowed us identifying two different conformations that represent minima in the potential energy surface (PES) of the molecule, depending on the relative orientation that the OH groups would adopt respect each other. Natural bond orbital calculations confirm that the anomeric effect would be responsible of the higher stability of the so-called conformer II ( C 2 symmetry, structure classically assumed as the unique possible conformation of the silanediol group) compared with conformer I ( C 1 symmetry), although the energy difference between both structures steadily decreases with the increase of the size of the basis set chosen (Δ E 0 = 0.84 kcal/mol; B3LYP/aug-cc-pVQZ). In addition to the theoretical work, DMSD was synthesized and its IR spectra (in solid phase and dimethylsulfoxide solution) and Raman spectrum (in solid phase) were, for the first time, completely assigned with the support of DFT calculations. Besides the above mentioned conformers, and in order to achieve a better description of the vibrational bands that are shifted in the experimental spectra due to intermolecular interactions, two hydrogen bonded dimers of DMSD were modeled and their vibrational spectra were calculated. The results of this work point to the plausible presence of stable moderate-size hydrogen bonded oligomers of DMSD even in solution.

Degradation of silicone polymer in a field soil under natural conditions

Silicone polymers (PDMS=polydimethylsiloxane) are used in numerous consumer and industrial products. Our previous work showed that they will degrade in soil under laboratory conditions. This paper investigates PDMS degradation in the field. Four soil plots (each 2.44 m×2.44 m ) in Michigan were sprayed in May, 1997, with aqueous emulsion to achieve nominal soil PDMS concentrations of 0 (control), 215 (low), 430 (medium), and 860 (high) μg/g. Over the following summer, soil cores (0–5 and 5–10 cm) were collected every two weeks and analyzed for decrease in total soil PDMS, and decrease in molecular weight of remaining PDMS. PDMS concentrations decreased 50% in 4.5, 5.3, and 9.6 weeks for the low, medium, and high treatments, respectively. Degradation rates were 0.26 (low), 0.44 (medium), and 0.44 (high) g PDMS/m 2 day, indicating that degradation capacity of the soil was exceeded by the High treatment. Dimethylsilanediol (DMSD), the main degradation product, was detected in most samples at <5% of original PDMS. This is consistent with laboratory data showing biodegradation and volatilization of DMSD. Deeper sampling (to 20 cm) found only trace amounts of DMSD, and minor downward movement of the polymer. Respraying and subsequent analysis of one plot with a medium treatment in late August showed slow PDMS degradation during the cool, wet fall, followed by a 40% decrease over winter and extensive degradation during the summer of 1998. The study thus shows that PDMS will degrade under field conditions as predicted from laboratory experiments.

Degradation of polydimethylsiloxane fluids in the environment — a review

Due to their insolubility in water and high adsorption coefficient, liquid polydimethylsiloxanes (PDMS) discharged as effluent will adsorb to particulate matter and, therefore, will become a component of sewage sludge during waste water treatment. The subsequent environmental fate of PDMS will depend on the fate of the sludge. Due to increasing practices of soil amendment with sewage sludge the principal environmental compartment receiving PDMS fluids is the soil. Degradation of PDMS is a common process taking place in many different types of soils. It occurs through a unique combination of environmental degradation processes. Initial hydrolysis of PDMS is catalysed by clay minerals, the principal component of soil. The primary hydrolysis product, dimethylsilanediol (DMSD), is then either biodegraded, or evaporated into the atmosphere, where it is subsequently oxidised in the presence of sunlight. The end products in both cases are expected to be CO 2, SiO 2 and H 2O.

HPLC/ICP-OES determination of water-soluble silicone (PDMS) degradation products in leachates

Inductively coupled plasma optical emission spectrometry (ICP-OES) was used for the element-specific determination of water-soluble organosilicon species separated by high-performance liquid chromatography (HPLC). Leachates from different waste deposit sites were investigated. The polydimethylsiloxane (PDMS) degradation product dimethylsilanediol (DMSD) could be detected in almost all samples in the low mg L–1 range, and it was furthermore possible to determine trimethylsilanol (TMSOL) in some leachate samples in the μg L–1 range. TMSOL was additionally analyzed by a method established before (LT-GC/ICP-OES). This study proved the occurrence of silanol compounds in leachates from locations were silicone material is deposited.

Fate of Cyclic Methylsiloxanes in Soils. 1. The Degradation Pathway

To determine the degradation pathway for cyclic volatile methylsiloxanes (cVMS) in soil, 40−200 mg kg-1 of 14C-labeled octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6) were incubated in a soil sample at room temperature (∼22 °C) and ∼30% relative humidity. The organosilicon species extracted at different times were analyzed by gas chromatography/mass spectroscopy (GC/MS), gel permeation chromatography (GPC), and reverse-phase high-performance liquid chromatography (RP-HPLC). It was found that the degradation of cVMS was a multistep process, initiated by ring-opening hydrolysis of the cyclics to form linear oligomeric siloxane diols, followed by further hydrolysis of these oligomeric diols to the monomer dimethylsilanediol (DMSD). For D4, the ring-opening hydrolysis was faster than the subsequent degradation of tetramer and trimer diols {H[OSi(CH3)2]nOH, n = 3 and 4}, resulting in substantial accumulation of these oligomeric siloxane diols at early stages. In contrast, ring-opening was the rate-limiting step for D5 and D6, as indicated by the lack of oligomeric diol accumulation at any stage of the cVMS degradation. Nevertheless, all oligomeric siloxane diols were unstable in air-dried soil and ultimately hydrolyzed to DMSD within a few hours to a week, depending on the humidity. When the soil was re-wetted to water saturation, some of the intermediates continued to hydrolyze to DMSD, and some were converted back to cVMS, which then evaporated from wet soil.

Microbial degradation of dimethylsilanediol in soil.

Dimethylsilanediol (DMSD) is the ultimate hydrolysis product of silicone (polydimethylsiloxane = PDMS) polymer in soil. Our previous paper showed that it would volatilize from soil, and the present study investigates the importance of microbial degradation in removing DMSD from soil. DMSD (14C-labeled) was thus incubated (1 mg kg-1) for 30 wk at 25 °C in soils from a permanent grass field, a corn field, a deciduous woodland, and a pine woodland. Release of14 CO2 varied from 0.4 to 1.6% wk-1. For 3 of the soils, 14CO2 increased with higher microbial biomass, while organisms in the deciduous woodland soil were more active in degrading DMSD than organisms in the other soils. After 30 weeks, most of the remaining 14C in the soil had moved from freely available water extractable to less available acid and base extractable fractions. Similar incubations with 2% plant litter showed extensive transfer of the DMSD into the litter layer. Incubations with a microbial inhibitor showed less DMSD degradation, while cold storage of soils almost completely stopped degradation. These results suggest that microbial degradation is an important mechanism of DMSD loss from soil.

Volatilization and sorption of dimethylsilanediol in soil

AbstractOur previous studies showed that dimethylsilanediol (DMD) was the main hydrolysis product of slicone (polydimethylsiloxane) polymer in soil. In the present study, volatilization of 14C‐DMSD from soil (1 mg kg−1) was investigated in open tubes, with weekly remoistening. Losses of 14C from Londo sandy clay loam and Pipestone sand were about 3.6 and 7.7% wk−1, respectively, and were attributed mostly to volatilization. For select samples, DMSD was trapped and identified as the volatilized compound. From 12 soils of variable properties, losses ranged from 1.4 to 6.4% wk−1, with higher rates correlated with sandier textures. An estimated Kd of 0.1 L kg−1 in wet soil suggests potential mobility of DMSD, but increased bonding with soil drying means that mobility will be retarded under field conditions. Results suggest that volatilization will be a major route of loss of DMSD from soil.

VOLATILIZATION AND SORPTION OF DIMETHYLSILANEDIOL IN SOIL

Our previous studies showed that dimethylsilanediol (DMD) was the main hydrolysis product of slicone (polydimethylsiloxane) polymer in soil. In the present study, volatilization of 14C-DMSD from soil (1 mg kg−1) was investigated in open tubes, with weekly remoistening. Losses of 14C from Londo sandy clay loam and Pipestone sand were about 3.6 and 7.7% wk−1, respectively, and were attributed mostly to volatilization. For select samples, DMSD was trapped and identified as the volatilized compound. From 12 soils of variable properties, losses ranged from 1.4 to 6.4% wk−1, with higher rates correlated with sandier textures. An estimated Kd of 0.1 L kg−1 in wet soil suggests potential mobility of DMSD, but increased bonding with soil drying means that mobility will be retarded under field conditions. Results suggest that volatilization will be a major route of loss of DMSD from soil.