Particulate Iodine Research Articles

Early Diagenetic Controls on Sedimentary Iodine Release and Iodine‐To‐Organic Carbon Ratios in the Paleo‐Record

AbstractIodine cycling in the ocean is closely linked to productivity, organic carbon export, and oxygenation. However, iodine sources and sinks at the seafloor are poorly constrained, which limits the applicability of iodine as a biogeochemical tracer. We present pore water and solid phase iodine data for sediment cores from the Peruvian continental margin, which cover a range of bottom water oxygen concentrations, organic carbon rain rates and sedimentation rates. By applying a numerical reaction‐transport model, we evaluate how these parameters determine benthic iodine fluxes and sedimentary iodine‐to‐organic carbon ratios (I:Corg) in the paleo‐record. Iodine is delivered to the sediment with organic material and released into the pore water as iodide (I−) during early diagenesis. Under anoxic conditions in the bottom water, most of the iodine delivered is recycled, which can explain the presence of excess dissolved iodine in near‐shore anoxic seawater. According to our model, the benthic I− efflux in anoxic areas is mainly determined by the organic carbon rain rate. Under oxic conditions, pore water dissolved I− is oxidized and precipitated at the sediment surface. Much of the precipitated iodine re‐dissolves during early diagenesis and only a fraction is buried. Particulate iodine burial efficiency and I:Corg burial ratios do increase with bottom water oxygen. However, multiple combinations of bottom water oxygen, organic carbon rain rate and sedimentation rate can lead to identical I:Corg, which limits the utility of I:Corg as a quantitative oxygenation proxy. Our findings may help to better constrain the ocean's iodine mass balance, both today and in the geological past.

Factors regulating the concentration of particulate iodine in coastal seawater

AbstractTo investigate the factors regulating the concentration of particulate iodine (PI) in seawater, it was measured in two Pacific coastal areas adjacent to Japan (offshore Aomori and offshore Fukushima) in two seasons (May and October) along with parameters such as particulate organic carbon (POC) and nitrogen (PON), dissolved iodine (DI), and phytoplankton pigments. The observed PI concentrations ranged from 0.0068 to 2.2 nmol L−1, with uncertain seasonal and regional differences. The atomic ratio of PI to POC (I/C) ranged from 4.4 × 10−7 to 1.1 × 10−4, in line with previous studies on marine phytoplankton, although the lower part of the range of the I/C in this study was found to be somewhat lower compared to the previous studies. The dataset was divided in three groups namely, lower (Group A), average (Group B), and higher (Group C) I/C because the I/C is an indicator of the accumulation efficiency of PI in particles in seawater and POC is the main carrier of PI. Based on the observed POC concentrations, the atomic ratio of POC to PON (C/N), and the ratio of carbon derived from chlorophyll a to POC, the three groups were characterized by phytoplanktonic physiological states as highly productive, steady, and senescent states for Groups A, B, and C, respectively. Based on the finding that PI production is associated with the phytoplankton physiological state, the seasonal and regional differences in PI concentration and I/C in the observation areas were consistently explained. Finally, we suggest that the phytoplanktonic physiological state is one of the vital factors regulating the PI concentration in seawater.

Ultra-Sensitive Determination of Particulate, Gaseous Inorganic and Organic Iodine-129 and Iodine-127 in Ambient Air.

Atmospheric iodine cycling is of significance in climate change and environmental and health impacts. To better explore speciation transformation of atmospheric stable and radioactive iodine, an ultra-sensitive analytical method was established for determination of 129I and 127I in particulate, gaseous inorganic, and gaseous organic species, which was conducted with a self-designed cascade sampling apparatus, followed by their separation with a pyrolysis system and accelerator mass spectrometry and ICP-MS measurements. Combustion protocols for three sampling matrices and NaOH concentration for iodine trapping were optimized to achieve a safe analytical procedure with a high chemical yield of iodine. Based on the lowest concentrations of 129I and 127I, a suitable activated carbon product for adsorption of gaseous organic iodine was carefully selected. The detection limits of the three species were 0.30-2.21 ng m-3 for 127I and 0.05-0.22 × 105 atoms m-3 for 129I. This newly established method was successfully applied to analyze the levels and species of 129I and 127I in ambinet air from Xi'an, China, from May to August, 2020. Gaseous organic iodine was found to be the dominant species of 127I and 129I, accounting for about half of total iodine, and gaseous inorganic iodine and particulate iodine accounted for one-quarter each during the whole sampling period. Speciation variation of 129I and 127I indicates that speciation transformation apparently occurred at the turn of spring and summer, mainly between particulate and gaseous organic iodine. This study has implications on delicate tracing of the atmospheric behavior of iodine with long-lived anthropogenic 129I.

Mixing state and distribution of iodine-containing particles in Arctic Ocean during summertime

Iodine chemistry plays a key role in ozone destruction and new aerosol formation in the marine boundary layer (MBL), especially in polar regions. We investigated iodine-containing particles (0.2-2 μm) in the Arctic Ocean using a ship-based single particle aerosol mass spectrometer from July to August 2017. Seven main particle types were identified: dust, biomass combustion particles, sea salt, organic S, aromatics, hydrocarbon-like compounds, and amines. The number fraction of iodine-containing particles was higher inside the Arctic Circle (>65°N) than outside (55–65°N). According to the air mass back trajectories, the latitudinal distribution of iodine-containing particles can be mainly attributed to iodine emissions from the sea ice edge region. Diurnal trends were found, especially during the second half of cruise, with peak iodine-containing particle number fractions during low-light conditions and relatively low number fractions at midday. These results imply that solar radiation plays a significant role in modulating particulate iodine in the Arctic atmosphere.

Bifunctional conjugated microporous polymer based filters for highly efficient PM and gaseous iodine capture

Cross-linked conjugated microporous polymers (CMPs) based air filters obtained by a one-step cross-coupling reaction for effective capture of particulate matter and gaseous iodine from dusty air.

Penetration factor and indoor deposition rate of elementary and particulate iodine in a Japanese house for assessing the effectiveness of sheltering for radiation exposures

Sheltering is one of the countermeasures for protection against radiation exposures in nuclear accidents. The effectiveness of sheltering is often expressed by the reduction factor, that is the ratio of the indoor to the outdoor cumulative radioactivity concentrations or doses. The indoor concentration is mainly controlled by the air exchange rate, penetration factor, and indoor deposition rate. The penetration factor and indoor deposition rate depend on the surface and the materials and structure of windows and doors as it is these openings in the building envelope that control penetration. We investigated experimentally these parameters of I2 and particles. The experiment was performed in two apartment houses, three single-family houses, and chambers. The obtained penetration factor ranged from 0.3 to 1 for particles of 0.3–1 μm and 0.15–0.7 for I2 depending on the air exchange rate. The indoor deposition rate for a house room ranged from 0.007 to 0.2 h−1 for particles of 0.3–1 μm and 0.2–1.5 h−1 for I2.

Quantitative detection of iodine in the stratosphere

Oceanic emissions of iodine destroy ozone, modify oxidative capacity, and can form new particles in the troposphere. However, the impact of iodine in the stratosphere is highly uncertain due to the lack of previous quantitative measurements. Here, we report quantitative measurements of iodine monoxide radicals and particulate iodine (Iy,part) from aircraft in the stratosphere. These measurements support that 0.77 ± 0.10 parts per trillion by volume (pptv) total inorganic iodine (Iy) is injected to the stratosphere. These high Iy amounts are indicative of active iodine recycling on ice in the upper troposphere (UT), support the upper end of recent Iy estimates (0 to 0.8 pptv) by the World Meteorological Organization, and are incompatible with zero stratospheric iodine injection. Gas-phase iodine (Iy,gas) in the UT (0.67 ± 0.09 pptv) converts to Iy,part sharply near the tropopause. In the stratosphere, IO radicals remain detectable (0.06 ± 0.03 pptv), indicating persistent Iy,part recycling back to Iy,gas as a result of active multiphase chemistry. At the observed levels, iodine is responsible for 32% of the halogen-induced ozone loss (bromine 40%, chlorine 28%), due primarily to previously unconsidered heterogeneous chemistry. Anthropogenic (pollution) ozone has increased iodine emissions since preindustrial times (ca. factor of 3 since 1950) and could be partly responsible for the continued decrease of ozone in the lower stratosphere. Increasing iodine emissions have implications for ozone radiative forcing and possibly new particle formation near the tropopause.

Preparation and characterization of TiO2 nanotubes antimicrobial coating of iodine-supported titanium implants

TiO2 nanotubes have a good application prospect in the field of drug load and delivery. In this study, TiO2 nanotubes were prepared by electrochemical anodic oxidation with voltage and time of 60 V and 2 hours, respectively. After anodization, it was annealed at 450 ° C for 2 hours. The crystalline phases as well as the morphology and structure of nanotubes were characterized by XRD, field-emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy (EDS), respectively. The results show that surface of TiO2 nanotubes are clean and highly ordered construction. In addition, the diameter and wall thickness of the nanotubes are about 110 nm and 5 μm, respectively. Finally, the TiO2 nanotubes which load iodine by electrodeposition method have polymer particulate iodine on the surface, thereby developed a kind of orthopaedic implants with antibacterial properties, which is expected to be widely used in clinical practice.

Iodine balance, growth and biochemical composition of three marine microalgae cultured under various inorganic iodine concentrations

Marine phytoplankton have been found to be involved in the biogeochemical cycle of iodine in the ocean. However, the role of iodine in the metabolism of marine microalgae has hardly been studied and whether iodine is an element required for growth is not known. In this study, three species of marine microalgae were grown in batch cultures at various concentrations of iodide (I−) or iodate (IO3 −) in order to evaluate their effect on growth rate and biochemical composition. Changes in inorganic iodine concentrations in the culture medium were also determined. Growth rate was not affected by external inorganic iodine concentration in cultures of Dunaliella salina and Tisochrysis lutea. In cultures of Phaeodactylum tricornutum, growth was inhibited at 2500 µM IO3 −. No clear effects of I− or IO3 − were observed on biochemical composition, except for the particulate iodine content of the microalgae, which increased with increasing dissolved iodine concentration. Results of dissolved inorganic iodine measurements indicated that IO3 − was reduced to I− during the exponential growth phase of microalgae cultures, under both natural and higher IO3 − concentrations. Iodine balance calculations showed that the amount of disappeared IO3 − was higher than the amount of I− produced in several cultures and that this discrepancy could not be explained by the formation of particulate iodine. I incorporation rates into biomass were low compared to I− production rates. We conclude that although iodine is clearly taken up from the external medium and it is transformed by microalgae, it seems unlikely that it is an element required for growth or that it plays an essential role in microalgal metabolism.

Detection and Quantification of Gaseous and Particulate Fukushima Fission Products at Orangeburg, South Carolina.

Large amounts of fission products were released from the Fukushima nuclear accident after a devastating earthquake and subsequent tsunami hit the northeast coast of Japan on 11 March 2011. The radioactive mass was sent high into the atmosphere by hydrogen explosions and fires in the reactor buildings at Fukushima Daiichi Nuclear Power Plant and spread all over the world. A relatively complete detection of both gaseous and particulate fission products was conducted during 15 March and 30 May 2011 at Orangeburg, South Carolina, located along the southeast coast of the United States, 11,000 km from the accident site. The histograms of gaseous and particulate radionuclides were obtained, and the major radioactivity plateaus were found between 18 March and 7 April 2011. The maximum levels of particulate and gaseous 131I were 1.0 ± 0.1 and 5.0 ± 0.4 mBq m-3, respectively. The maximum radioactivities of 134Cs and 137Cs were 10 times less than that of the particulate 131I. The average activity ratio of 134Cs to 137Cs was determined as 0.98 ± 0.26 throughout the observation. It was found that the plateaus and spikes in the histogram curves corresponded to the nuclear release events at Fukushima Daiichi. The arrival times of the particulate and gaseous nuclear fallout were determined to be 8 and 10 d, respectively. The deposition rates of gaseous and particulate iodine and the mass transfer between the two phases were discussed based on the radioactivity ratios of the fission products. By comparing with the radionuclide effluent concentrations issued in NRC 10 CFR 20, it was concluded that the Fukushima fallout presented negligible radiation risk to the public at Orangeburg as well as in the southeastern coastal region of the U.S.

Iodine containing species in the remote marine boundary layer: A link to oceanic phytoplankton

[1] Iodine containing species have been measured in the particle phase (PM2.5) and the gas phase during a ship campaign between January and February 2007 in the South Atlantic marine boundary layer (MBL). Methyl iodide (CH3I) in the gas phase and soluble iodine species, i.e. iodide, iodate and an unidentified organic iodine species (UOI), in PM2.5 were measured. Temporal variations of gaseous and particulate iodine species were investigated. The exposure of the sampled air masses to phytoplankton along the back-trajectories was studied using a lagrangian transport model and satellite observations of oceanic chlorophyll-a concentration. Significant correlations were found between the concentrations of iodine species and the average chlorophyll exposure along back-trajectories, indicating an emission from phytoplankton in the open ocean. Good correlations were found when the ship approached or crossed the active biological region in the West-southern Atlantic. These results strongly suggest a connection between iodine species and the phytoplankton in the ocean. This study was extended to examine the relation of the iodine measurements to satellite derived phytoplankton distributions. We show that specific phytoplankton species may have impact on different iodine containing species.

Characterization of iodine species in the marine aerosol: To understand their roles in particle formation processes

In this contribution, iodine chemistry in the Marine Boundary Layer (MBL) is introduced. A series of methodologies for the measurements of iodine species in the gas and particle phases of the coastal atmosphere has been developed. Iodine species in the gas phase in real air samples has been determined in two field campaigns at the west coast of Ireland, indicating that gaseous iodo-hydrocarbons and elemental iodine are the precursors of new particle formation. Particulate iodine speciation from the same measurement campaigns show that the non-water-soluble iodine compounds are the main iodine species during the marine particle formation. A seaweed-chamber experiment was performed, indicating that gaseous I2 is one of the important precursors that lead to new particle formation in the presence of solar light in the ambient air at the coastal tidal area.

Iodine chemistry and its role in halogen activation and ozone loss in the marine boundary layer: A model study

A detailed set of reactions treating the gas and aqueous phase chemistry of the most important iodine species in the marine boundary layer (MBL) has been added to a box model which describes Br and Cl chemistry in the MBL. While Br and Cl originate from seasalt, the I compounds are largely derived photochemically from several biogenic alkyl iodides, in particular CH2I2, CH2ClI, C2H5I, C3H7I, or CH3I which are released from the sea. Their photodissociation produces some inorganic iodine gases which can rapidly react in the gas and aqueous phase with other halogen compounds. Scavenging of the iodine species HI, HOI, INO2, and IONO2 by aerosol particles is not a permanent sink as assumed in previous modeling studies. Aqueous-phase chemical reactions can produce the compounds IBr, ICl, and I2, which will be released back into the gas phase due to their low solubility. Our study, although highly theoretical, suggests that almost all particulate iodine is in the chemical form of IO-3. Other aqueous-phase species are only temporary reservoirs and can be re-activated to yield gas phase iodine. Assuming release rates of the organic iodine compounds which yield atmospheric concentrations similar to some measurements, we calculate significant concentrations of reactive halogen gases. The addition of iodine chemistry to our reaction scheme has the effect of accelerating photochemical Br and Cl release from the seasalt. This causes an enhancement in ozone destruction rates in the MBL over that arising from the well established reactions O(1D) + H2O → 2OH, HO2 + O3 → OH + 2O2, and OH + O3 → HO2 + O2. The given reaction scheme accounts for the formation of particulate iodine which is preferably accumulated in the smaller sulfate aerosol particles.

Determination of organic, inorganic and particulate iodine in the coastal atmosphere of Japan

A reliable method for the sampling and analysis of atmospheric iodine species was developed. The air filtering system consisted of a 0.4 μm Nuclepore® filter, 47 mm in diameter, for particulate collection followed by two, 47 mm in diameter, cellulose filters for inorganic iodine collection. The latter filters had been impregnated with 1N LiOH in a 10% glycerol-water mixture. The organic iodine was collected by two beds holding 0.2 g of fibriform activated charcoal produced from phenol resin. Supplementation of the charcoal with triethylendiamine (TEDA) enhanced the sorption ability for gaseous iodine. The filters were analyzed by neutron activation analysis. The background radioactivity could be reduced by using the fibriform activated charcoal due to the low content of impurities in the phenol resin. The background count for128I (443 keV) obtained from the fibriform activated charcoal was about one order of magnitude lower than that of the conventional granular one (plant origin). Approximate detection limits for particulate, inorganic and organic iodine were 1, 0.5 and 0.5 ng/m3, respectively, when 50 m3 of air was sampled by this system. The air was sampled at two locations along the coast of Ibaraki, Japan. The concentration ranges of particulate, inorganic and organic iodine were 0.3–3.4, 1.2–3.3 and 7.8–20.4 ng/m3, respectively. Almost 90% of the atmospheric iodine was in a gaseous form in which organic iodine was dominant.

Determination of Particulate Iodine in Aerosols from Different Regions by Size Fractionating Impactor Sampling and IDMS

Abstract Concentrations of particulate iodine in aerosols depending on the particle size were determined after sampling with an impactor system by isotope dilution mass spectrometry (IDMS) using the production of negative I thermal ions. The collection efficiency of the impactor system was compared with a filter system by parallel samplings and agreed well. By different leaching processes, using sodium sulfite solution and distilled water, it was shown that various iodine species are incorporated in the aerosol particles. Determinations were carried out with samples from different areas, two continental places in Germany, which are more or less anthropogenically influenced, one location with marine and anthropogenic influences (North Sea) and one in the Weddell Sea, Antarctica, not anthropogenically influenced. In all cases we found the major part of the total iodine in the smallest aerosol particles with an aerodynamic diameter of <0.49 μm. Investigations of the continental iodine in aerosols over a two-...

Determination of atmospheric iodine species using a system of specifically prepared filters and IDMS

A system was developed which allowed the determination of four different atmospheric iodine species by preparing glass microfibre filters, which were arranged in consecutive order, in a specific way. Particulate iodine was collected by a particle filter, HI and I2 by a NaOH impregnated filter, HOI was adsorbed on a TBAH impregnated filter and organoiodine was adsorbed on a filter loaded with activated charcoal. These behaviours were checked by extensive model experiments. Two or more filters of the same type were used in series to show the degree of collection of one iodine species. Two European samples, one of continental and one of marine origin, and two Antarctic samples were analysed by this filter system using isotope dilution mass spectrometry (IDMS) for quantification. The distribution pattern for the different iodine species is similar for the two European samples. Organoiodine is found to be the most abundant species whereas in Antarctica the HI/I2 fraction is up to nearly 50% of the total iodine. The particulate iodine fraction is higher in Europe than in Antarctica, which is due to the low particle concentration in the remote area of Antarctica. The higher HI/I2 and HOI fractions found at the North Sea compared with the continental sample indicate that the ocean is a primary source of these species. Concentrations in the range of (0.3–3.1) ng I/m3 were analysed for particulate iodine, (0.4–1.3) ng I/m3 for HI/I2, (0.2–1.8) ng I/m3 for HOI and (0.4–7.6) ng I/m3 for organoiodine. The detection limits varied with the variances of the blank values of the different filters and lay between 0.02 ng I/m3 and 0.24 ng I/m3 using sample volumes of 70 m3 air.

Are there interactions of iodine and sulfur species in marine air photochemistry?

Portions of the global cycles of sulfur and iodine could be intertwined in reactions resulting from the emissions of dimethyl sulfide (DMS) and methyl iodide. A two‐dimensional photochemical model of a marine tropical tropospheric synoptic system is used to analyze the consequences of these emissions through their atmospheric transformation cycles to aerosols. Following one line of analysis, the reaction of IO+DMS → DMSO+I could play a significant role, ∼30–50%, in destroying DMS, if the reaction proceeds at the published fast rate. Under these assumptions, the concentrations of DMSO (dimethyl sulfoxide), dimethyl sulfone (DMSO2), and sulfate appear to set rather strict upper limits on the extent of the reaction over the global oceans, and hence, on [IO], which is &lt; 2×105 molecule cm−3. DMS plays an important role in the iodine cycle by converting IO into I. The formation of a reservoir species HOI, following H abstraction by IO, may help explain the high concentrations and apparent strong diurnal variation of filter‐sampled inorganic iodine gases and help to explain low [IO] values. In an alternate, preferred, line of analysis, the rate of reaction of IO+DMS may be much slower, &lt; 10−12 cm3 molecule−1s−1 and the I and S cycles remain decoupled: in this case, it appears that the OH+DMS addition reaction could proceed ∼30% to form DMSO. The mean concentration and variations of gaseous and particulate iodine species are also better simulated. A simple aerosol model describing fine and coarse particles is used to close the S budget, and, if only a minor role is played by DMSO, the budget compares well with data. Simulated SO2 concentrations for the upper troposphere are highly dependent on upper tropospheric [OH]. The paper concentrates on remote tropical ocean regions and includes simulations of the spatial and diurnal variation of iodine species I, IO, HI, HOI, IONO2, I2O2 and Itot(particulate) the sulfur species DMS, DMSO, DMSO2, MSA (methane sulfonic acid), SO2, and SO4=(particulate), as well as the species OH, HO2, and H2O2.

大気エアロゾルに対する放射性元素状ヨウ素ガスの吸着特性

Laboratory scale experiments on the adsorption of radioactive elemental iodine (I2) gas onto atmospheric aerosol showed that the adsorption reached an equilibrium state in about twelve minutes at high initial I2 concentrations. The proportion of iodine which was adsorbed on the aerosol gradually decreased with increasing initial I2 concentration ranging over 10-13 to 10-9g/cm3 at a reaction time of 31min but was almost constant at a reaction time of 2min. A fraction of iodine desorbed from particulate iodine as mainly I2 gas. An adsorption isotherm of atmospheric aerosol for I2 gas was estimated from the experimental data of long reaction time and high I2 concentrations. Using this adsorption isotherm, a theoretical equation, which was similar to our previous equation, was derived to explain the experimental results. A geometric mean and standard deviation of sticking probability in the equation were estimated to be 1.2×10-2 and 2.7, respectively. Almost all experimental data were within ranges of calculated results considering the geometric standard deviation of sticking probability.

Iodine-129 in the environment of a nuclear fuel reprocessing plant: VII. Concentrations and chemical forms of 129I and 127I in the atmosphere

Gaseous and particulate iodine samples have been collected simultaneously from the atmosphere around the Karlsruhe Reprocessing Plant (WAK) using a three-component sampler which separates the iodine into three fractions, namely: (a) associated with aerosol particles, (b) gaseous inorganic and (c) gaseous organic. These field measurements were conducted at five sampling sites located between 0·7 and 23·0 km from the WAK exhaust air stack in the dominant downwind direction. In 1986 the air samples were collected between October and December and in 1987 between June and September. The aerosol fraction of 129I in 1986 ranged between 5·2 and 30·8% and in 1987 between 1·7 and 9·7%. The corresponding values for 127I were 12·9 and 28·0% (1986) and 16·4 and 9·4% (1987). The gaseous inorganic 129I fraction varied between 26·8 and 35·2% (1986) and between 17·2 and 27·3% (1987). Corresponding 127I data were: 1·6 and 26·2% (1986) and 18·7 and 26·6% (1987). The gaseous organic fraction of 129I accounted for 34·0–65·9% (1986) and 62·9–88·8% (1987). Corresponding 127I values were: 46·1–73·8% (1986) and 59·3–71·9% (1987). A corresponding data set from a ‘control’ site in Bonn gave the following results: aerosol fraction: 129I: (6·0 ± 1·0) × 10 −16 g/m 3; 127I: (2·0 ± 1·9) × 10 −9 g/m 3; gaseous inorganic iodine: 129I: (1·1 ± 4·2) × 10 −15 g/m 3; 127I: (1·5 ± 0·9) × 10 −9 g/m 3; gaseous organic iodine: 129I: not detectable; 127I: (8·7 ± 3·5) × 10 −10 g/m 3.

放射性元素状ヨウ素ガスのフライアッシュエアロゾルに対する吸着特性

The adsorption of radioactive elemental iodine (I2) gas onto fly-ash aerosol has been studied to provide basic data for the realistic and precise assessment of dose to the general public from radioiodine released from nuclear facilities.A mixture of fly-ash aerosol and 131I2 gas was passed through a cylindrical glass vessel so that particulate iodine was formed by adsorption of I2 onto aerosol. Then the concentrations of I2 and particulate iodine were measured.It was found that the adsorption reached an equilibrium state between 5 and 12min and that the proportion of iodine which was adsorbed on the aerosol decreased with increasing initial I2 concentration ranging over 10-13 to 10-19g/cm3.The adsorption isotherm of the aerosol for I2 gas approximately followed Freundlich isotherm. Using the adsorption isotherm, a theoretical equation was derived to explain the adsorption on the basis of FUCHS' theory on the evaporation of droplets. A sticking probability in the equation decreased with increasing adsorbed amount. The calculated results were in good agreement with the experimental ones.