Rainwater Concentrations Research Articles

An analytic study on the evolution of the vertical profile of rain water concentration

This contribution hints at a serious problem in modelling the vertical profile of rain water concentration, which evolves under the effect of sedimentation, when cloud microphysical processes are represented in terms of a familiar one‐variable parameterization. If the parameterized precipitation flux increases faster than linearly with rain water concentration, as e.g. in the original Kessler‐concept, then the prognostic equation for this concentration takes the form of a quasi‐linear advection equation. The analytic solution is a transient ‘signal’ that ultimately breaks at some time and location and the solution becomes multivalued, that is physically meaningless. If, however, the problem is treated according to shock waves in nonlinear wave dynamics, a weak solution can be constructed. In that case, the multivalued solution is replaced by a discontinuous one.

Erosion by acid rain, accelerating the tracking of polystyrene insulating material

Because outdoor insulating materials in service are subjected to numerous wet and dry cycles, it is necessary to establish their performance in acid rain. The erosion effect of acid rain on atactic polystyrene insulating material is investigated using accelerated ageing by artificial acid rain. The degradation mechanisms of material structure and tracking resistance are discussed. The experimental results reported here show that the erosion of acid rain causes the degradation of the surface chemical and physical structures of polystyrene (PS) material so that the surface conductivity of aged material increases. Under electrical stress, the surface discharge current increases, and the local surface is deteriorated so that the tracking is initiated earlier and the material rapidly fails. The degradation rate of PS material in acid rain varies as function of the ion concentration, pH and conductivity of acid rain. Only the severe acid rain of high acidity and conductivity can exert an influence on PS insulating material. The concentration of actual rainwater is insufficient to lead to obvious erosion on PS insulation. PS insulation could resist on the erosion of normal acid rainwater. Even though clear degradation occurs with strong acid rain, PS could behave quite well in mild acid rain conditions.

Concentrations of nitrogen and sulfur species in gas and rainwater from six sites in Indonesia.

Gas mixing ratios of SO2, NO2 and HNO3 and nitrate and sulfate concentrations in rainwater have beenmeasured at six sites in Indonesia. The sites, Jakarta, Serang,Cilegon, Merak and Bogor, in Java, and Bukit Koto Tabang inSumatra, provide a range of pollution regimes in Indonesia.Jakarta and Bogor are heavily polluted sites in Java, whereasBukit Koto Tabang is a clean air station in a relativelyunpopulated area on the west coast of equatorial Sumatra. At thesesites rainwater was collected daily and gas samples weeklyduring 1996. The other three sites Serang, Cilegon and Merakrepresent smaller regional towns in west Java. At these sitesrainwater samples were collected weekly from June 1991 untilJune 1992.The results show that Jakarta has the highest volume-weightedmean sulfate concentrations in rainwater while the lowest weremeasured at Bukit Koto Tabang. Volume-weighted mean nitrateconcentration was about 24 μeq L-1 at Jakarta and Bogor,significantly higher than the 0.8 μeq L-1 measured atBukit Koto Tabang.Sulfur dioxide mixing ratios ranged from 4–7 ppbv in Jakarta toan average of 1.3 ppbv at Bukit Koto Tabang. Nitrogen dioxidemixing ratio was highest in Jakarta averaging 28 ppbv comparedwith the background mixing ratio of 1.2 ppbv at Bukit KotoTabang. Using dry deposition velocities estimated during aseparate study in the similar conditions of Malaysia enabled drydeposition estimates of SO2, HNO3 and NO2.Results of estimated total acidic S and N deposition (wet anddry) were greater than 250 meq m-2 yr-1 at the Jakartaand Bogor sites compared with about 23 meq m-2 yr-1 atBukit Koto Tabang. At Jakarta and Bogor dry deposition accountedfor more than 50% of the total deposition estimates compared with about 20% at Bukit Koto Tabang. Such deposition rates arehigh when compared to critical loads estimated for Indonesia bythe RAINS-Asia model. In this model, critical loads in western Java and equatorial western Sumatra fall into one of twoclasses: 50–100 and 20–50 meq m-2 yr-1. Thus acidic deposition flux at Jakarta and Bogor wasfound to be above the predicted critical loads even for the moreacid insensitive soils.

The variation of hydrogen peroxide in rainwater over the South and Central Atlantic Ocean

The concentration of hydrogen peroxide in rainwater over the South and Central Atlantic Ocean was determined. The rainwater samples were collected during an Intergovernmental Oceanographic Commission (IOC) sponsored baseline expedition in May and June 1996. The concentration of hydrogen peroxide was determined on diluted samples using a cobalt-catalyzed luminol chemiluminesence method. The concentration of hydrogen peroxide in rainwater varied from 3.5 to 71 μM with an average ( n=25) and standard deviation of 26 and 22 μM, respectively. These are similar to previously reported average hydrogen peroxide concentrations in marine rainwater of the Gulf of Mexico (40 μM), the western Atlantic Ocean (13 μM), and Florida Keys (28 μM). The concentration of hydrogen peroxide in rainwater varied with time of the day, with lower concentrations in early morning and higher concentrations in the late afternoon. The rainwater concentration of hydrogen peroxide also decreased during a rainstorm that may be an indication of a washout effect. The general levels of hydrogen peroxide in rainwater reported here and elsewhere together with the satellite-measured global distribution of precipitation indicate that wet deposition could affect water column hydrogen peroxide significantly in certain parts of the world.

Modelling and measurements of below cloud scavenging processes in the highly industrialised region of Cubatão-Brazil

Below cloud scavenging has been investigated from rainwater chemistry measurements using a one-dimensional scavenging numerical model and surface data from the local atmospheric conditions. The local emissions of pollutants from a large industrial complex in the south-eastern Brazil were also evaluated in the modelling. The scavenging model was coupled to the measurements of SO 2− 4, NO − 3 and NH + 4 found in the rainwater samples. The concentration of gases and particles samplings and meteorological parameters measured during the study of rain episodes were used as input data in the numerical model, which simulates the raindrop interactions associated with the removal process. The results were compared with those actually measured. The variability of the rainwater concentrations estimated through the scavenging model was also compared to the chemical analysis of the rainwater collected by fractionated rain samplers. The results show a good agreement between both modelled and observed data as seen from the role of the raindrop size distribution in the below cloud scavenging of pollutants

Resistance to Tracking and Erosion of Silicone Rubber Material under Various Types of Precipitation

Environment stress and contaminants have become more and more severe due to the development of industry. Outdoor polymer insulating materials in use may suffer from rainwater containing various chemical contaminants so that their resistance to tracking degrades. In this paper, the tracking resistance of high-temperature vulcanized silicone rubber (HTVSR) under various types of precipitation is evaluated by the incline-plane method, using artificial rainwater as a contaminant. The influences of ion concentration, acidity, and conductivity of rainwater on the energized silicone rubber material are studied. Experimental results reported here show that the degradation of the energized material increases with the ion concentration of the rainwater; the discharge current and the erosion of material increase. The conductive ions in rainwater could induce more tracking and discharge on the energized material surface, and acidic rainwater could accelerate the electrolyte process in the materials and dissolve the inorganic filler in silicone rubber. Although silicone rubber degrades under our process of accelerated aging using artificial rainwater, the ion concentration, acidity and conductivity of actual precipitation is insufficient to exert a significant degradation effect on silicone rubber. Silicone rubber can resist the erosion of even the most corrosive rainwater and does not fail.

Significance of the Long Range Transport of Pesticides in the Atmosphere

Abstract Synopsis:Since the 1960’s there has been a growing body of data regarding the presence of pesticides in the atmosphere. The monitoring results obtained show that traces of pesticides may undergo long range transport and be deposited considerable distances away from the treatment areas, including remote areas such as the Arctic and Antarctic regions. Pesticides have been found in air, rain, cloud water, fog and snow. The appearance and subsequent behaviour of pesticides in the atmosphere are complex processes and the concentrations found depend on several variables such as their volatility, photostability, method of application and extent of use. Whilst volatility of pesticides can be linked to their Henry’s Law constant this is very much a simplification since it is also influenced by the surfaces treated, e.g. soil or leaves, and by the extent to which aerosols are formed during the application. The disappearance of pesticides from the atmosphere is due to hydrolysis, indirect photolysis via OH. radicals and to deposition in rain. Pesticides which are resistant to hydrolysis and photolysis can be transported over great distances, for example, organochlorine insecticides have been detected in the Arctic regions. In general, concentrations in rainwater are, when detected, in the low or sub mg/l range and highest concentrations are found during the time of application. The use of fugacity models has been shown to be a useful approach to predict concentrations in air. Under most conditions the presence of pesticides in air, or rainwater, has no significant effects on non-target systems, including direct and indirect effects. Exceptions to this are damage by auxin-type herbicides to sensitive plants which has resulted on restrictions in their use in certain areas and transient chlorotic spotting thought to be caused by drift of aerosols from application of low rate sulfonyl urea herbicides. For animal species one possible exception has been postulated. This is for persistent organochlorine pesticides in Arctic regions where, due to the very oligotrophic nature of the Arctic ocean, they are more liable to bioaccumulate and be transported in the food web giving enhanced levels in mothers’ milk.

The soil surface characteristics of vegetation stripes in Northern Mexico and their influences on the system hydrodynamics: An experimental approach

Vegetation stripes were described in arid areas of Africa, Australia and México. They depend on the local concentration of rain water after runoff. In México, we described the soil surface characteristics of vegetation stripes and performed rainfall simulations to analyze its hydrodynamic behaviour. Simulations were performed on plots characterized by the four soil surface features represented in the stripes. Four types of surface crusts were found in the stripes, erosion, sedimentation, and two types of structural crusts. The less vegetated plots had relatively impervious crusts with low preponding rains and high constant runoff rates. On the contrary, the highly vegetated plot had a thin crust and abundant litter which allowed a high infiltration rate. Runoff rates were positively related to rainfall intensity. Those relationships between surface characteristics and runoff determine the fate of rain water and may allow the prediction of the amount of runoff for a specific rain on a given plot.

Black carbon concentrations in precipitation and near surface air in and near Halifax, Nova Scotia

Black carbon (soot) concentrations have been measured in rain water, snow samples and near surface air at several locations in Nova Scotia, Canada. The average black carbon concentration in near surface air in summer was found to be 0.54 μg m -3 compared to 1.74 μg m -3 in the winter season. These values are comparable to black carbon concentrations found in other mid-size urban areas. The black carbon concentration in rain water and snow samples varied between an undetectable amount to about 20 μg kg -1 of rain (or melt) water. The relatively low concentrations of black carbon in precipitation are attributed to extratropical cyclones that often develop off-shore to the east and south of Nova Scotia in relatively clean conditions of the marine boundary layer.

Phosphorus in rainwater: Partitioning inputs and impact on the surface coastal ocean

Phosphate concentrations in rainwater were measured at a Ligurian coastal sampling site (Cap Ferrat, France) from February 1997 to February 1998 to study the impact of wet atmospheric phosphorus (P) input on the surface ocean. Soluble and particulate fractions were differentiated to evaluate the atmospheric supply of bioavailable P. Complexed and reactive phases within the dissolved fraction were also separated. Preliminary results showed a high temporal variability in total concentration (0.05–4.3 μmol liter−1). The factors controlling the partitioning between reactive and complexed components are not clear. However, the partitioning between dissolved and particulate fractions is linked to emission sources. Soil‐derived dust from the Sahara was identified as an important source of atmospheric P, mainly insoluble. Conversely, anthropogenic emissions are sources of soluble P (i.e., basically bioavailable). A significant part of these emissions could originate from incinerators and/or biomass burning. The different wet fluxes are calculated to total 165 μmol m−2 yr−1, and the dissolved and particulate inputs are 95 and 70 umol m−2 yr−1, respectively. Taking into account the respective sol ubility of such inputs, anthropogenic emissions appear to be responsible for relatively high amounts of bioavailable P. Even if the atmosphere is globally a minor source of nutrients (compared with riverine inputs and marine vertical mixing), it might be the only source of P in oligotrophic conditions. For example, assuming that P is a limiting factor in the Mediterranean Sea, the rain event of 19 June 1997 (17 μmol m−2 of bioavailable P) potentially induced a new production of 0.02 g C m−2, which is a significant value in such conditions. Converted into biomass and integrated over a 5‐‐thick water layer, such an atmospheric input represents 0.35–0.45 mg chlorophyll a m−2, an appreciable portion of the total biomass during this period. This observation underlines the major role of the atmosphere during oligotrophic periods in the western Mediterranean.

Factors affecting the levels of hydrogen peroxide in rainwater

Measurements of hydrogen peroxide (H 2O 2) and several meteorological and chemical parameters were made for 34 rain events which occurred in Miami, Florida between April, 1995 and October, 1996. The measured H 2O 2 concentrations ranged from 0.3 to 38.6 μM with an average concentration of 6.9 μM. A strong seasonal dependence for H 2O 2 concentrations was observed during this period, with highest concentrations in the summer and lower levels in the winter, which corresponds to the stronger solar radiation and higher vaporization of volatile organic compounds (VOCs) in the summer and fall, and the weaker sunlight and lower vaporization in the winter and spring. Measurements also showed a significant increase trend of H 2O 2 with increasing ambient rainwater temperature. Rains that were out from lower latitude were exposed to higher solar irradiation and contained relatively higher levels of H 2O 2 than those from the north. All these observations indicate that photochemical reactions that involved volatile organic compounds are the predominant source of H 2O 2 observed in rainwater. During several individual rainstorms, H 2O 2 concentration was found to increase as a function of time due to electrical storm activities. This finding suggests that lightning could be an important factor that determines the level of H 2O 2 during thunderstorms. Statistical data showed that the highest concentrations of H 2O 2 were observed only in rains containing low levels of nonsea-salt sulfate (NSS), nitrate and hydrogen ion. H 2O 2 concentrations in continental originated rains were much lower than marine originated ones, indicating that air pollutants in continental rains could significantly deplete the H 2O 2 concentration in atmospheric gas-phase, clouds and rainwater.

Water-soluble organic nitrogen in atmospheric aerosol: a comparison of UV and persulfate oxidation methods

Two well established methods that are widely applied in the determination of marine dissolved organic nitrogen (DON) have been investigated in their application to the determination of rainwater DON and the water-soluble organic nitrogen component of atmospheric aerosol. Empirical observation highlighted some difficulties in the analysis of DON in these non-marine matrices, so some practical suggestions for the extension of the oxidative methods to atmospheric samples are proposed. Ten rain samples, 20 aqueous aerosol extracts, and a suite of commercially obtained organic nitrogen compounds were both chemically oxidised by persulfate and oxidised by exposure to high-intensity ultraviolet light. The total dissolved nitrogen concentration of the rains in this study ranged from 4 to 35 μM nitrogen. The aerosol extracts were diluted to a pre-oxidation concentration range of 12–65 μM N for oxidation and analysis. Both UV and persulfate methods require the aqueous extract of the aerosol organic nitrogen to be diluted approximately to rainwater concentrations for optimal oxidation efficiency, since sub-optimal recoveries and high analytical variability arise at high concentration. Some potential causes of analytical interference at higher concentration are discussed. This study shows that total dissolved nitrogen results obtained by the two methods are linearly correlated (with an R 2 of 0.87 for 30 samples) over the full range of natural rainwater concentrations, but results obtained using the persulfate oxidation are about 30% lower than those obtained by photo-oxidation.

Evaluation of the Characteristics of Acid Precipitation in Taipei, Taiwan Using Cluster Analysis

This work investigated the characteristics of acid precipitation collected in Taipei, Taiwan during 1991–1995 by performing cluster analysis. The extent to which meteorological conditions influence precipitation chemistry was also elucidated. Three potential sources of water-soluble ions in rainwater were identified: seasalt aerosols (Na+, Cl- and Mg2+), anthropogenic pollutants (H+ and NO3-), and mixing sources associated with sulfate (nss-SO42-, NH4+ and Ca2+). As the northeast flow prevailed during the northeast monsoon season, the concentrations of seasalt and sulfate ions in rainwater were significantly high. During that season, a typically high ratio of nss-SO42-/NO3- was also observed, indicating that Taipei might receive foreign pollutants via a long-range transport. In contrast, when the Pacific high dominated the region, nitrate concentration in rainwater was significantly elevated. Also during that period, the ratio of nss-SO42-/NO3- was substantially lower, indicating the prominence of acidic substances contributed by local sources.

Determination of trace amounts of boron in rainwater by ICP-IDMS and NTI-IDMS and the dependence on meteorological and anthropogenic influences

Two different mass spectrometric methods, inductively coupled plasma isotope dilution mass spectrometry (ICP-IDMS) and negative thermal ionisation isotope dilution mass spectrometry (NTI-IDMS), were applied to the determination of trace concentrations of boron in rainwater samples. After carrying out the isotope dilution step, ICP-MS was directly used for the measurement of the 11 B/ 10 B ratio. For NTI-IDMS, the isotope diluted boron was first separated by a boron selective ion exchanger and then the boron isotope ratio was determined by measuring negative BO 2 – thermal ions. Boron concentrations of 21 rainwater samples from different parts of Germany and from the Jungfraujoch in Switzerland at an altitude of about 3600 m were determined to be in the range 0.3-7 ng ml –1 . The detection limits were 0.2 and 0.3 ng ml –1 for ICP-IDMS and NTI-IDMS using 3 and 50 ml sample volumes, respectively. NTI-IDMS determinations were about a factor of 2.5 more time-consuming compared with ICP-IDMS. However, the boron concentrations determined by ICP-IDMS often showed slightly higher values than those determined by NTI-IDMS, which was due to contributions of relatively high 12 C + ion intensities to the 11 B + intensity when using a quadrupole ICP-MS instrument with insufficient mass resolution. ICP-IDMS is a fast and reliable method for the determination of boron concentrations down to <1 ng ml –1 in aquatic systems if mass resolution between mass numbers 11 and 12 is under control, whereas NTI-IDMS can be best applied as an accurate reference method at these low concentration levels. Significant dependence of the boron concentration in rainwater on the meteorological conditions, but not on the season of sampling, as well as anthropogenic influences, especially on the altitude of the sample collection place, was found by applying both mass spectrometric methods.

Impact of rainwater hydrogen peroxide on chlorophyll a content of surface Gulf Stream seawater off North Carolina, USA

Bioassays indicate addition of hydrogen peroxide in concentrations similar to rain sometimes decreases chlorophyll a (chl a) production in surface Gulf Stream seawater. Bioassays were conducted on shipboard in the spring and autumn of 1993, 1994, and 1995, using surface Gulf Stream seawater collected off the coast of North Carolina. Chl a increases were observed after addition of FeCl 3 (in 1 of 5 bioassays), iron (III) EDTA (6 of 6 bioassays), or EDTA alone (4 of 4 bioassays). The chl a increases were suppressed significantly in 7 of 1 1 of these bioassays when the bioassay seawater was initially diluted by 1% with a 30 or 40 μM solution of hydrogen peroxide (a concentration similar to rainwater). Hydrogen peroxide induced inhibition of chl a production was not observed in bioassays in which chl a increased in response to addition of nitrate or ammonium, hence the growth inhibition was associated with added metal or complexing agent. Rainwater therefore plays a complex role in primary productivity in surface seawater, with the specific effect dependent upon rainwater concentrations of nitrate, ammonium, trace metals and hydrogen peroxide, as well as on the extent of nitrogen limitation and the oxidant concentration in the surface seawater.

Summertime Seawater Concentrations of Dimethylsulfide in the Western Indian Ocean: Reconciliation of Fluxes and Spatial Variability with Long-Term Atmospheric Observations

Dimethylsulfide (DMS) measurements in the seawater of the subtropical and the temperate western Indian Ocean were conducted for the first time from 3 December to 20 December 1997. In total, 443 surface seawater DMS determinations were performed between 24°–49° S and 50° E–77° E with a frequency of 1 sample every 10 km. An important spatial variability was observed in seawater DMS concentrations with values ranging from 0.9 to 35.8 nM. DMS maxima coincided in most cases with thermal fronts and were in reasonable agreement with mean pigment figures obtained from satellite observations. The deduced DMS fluxes are consistent with long-term observations of atmospheric DMS and rainwater concentrations of nss- SO4= and MSA measured at Amsterdam island (37° S, 77° E); then account for the differences observed in atmospheric DMS concentrations between Amsterdam island and Cape Grim, Indian Ocean monitoring stations.

The chemistry of copper patination

The chemistry of copper patination was investigated by two series of experiments. The chemistry of an aqueous copper-sulphate solution was studied at concentrations and pH values near those predicted in an electrolyte on copper exposed to the atmosphere. The electrochemical reactions in an electrolyte in contact with cuprite were investigated in a reaction vessel which used cuprite powder in artificial rainwater to study the electrochemistry of the atmospheric corrosion and patination of copper. Typical sulphate concentrations in rainwater are sufficient to precipitate posnjakite (Cu 4SO 4 (OH) 62H 2O)), a possible precursor to brochantite, within an hour of wetting a cuprite surface. Brochantite (Cu 4SO 4 (OH) 6), the most commonly found copper salt in natural patinas is responsible for their green appearance. Precipitation of brochantite from the electrolyte resulted from an increase in pH due to the cathodic reduction of oxygen and an increase in cupric ion concentrations by cuprite oxidation.

Spectrophotometric determination of hydrogen peroxide in rainwater

Hydrogen peroxide in rainwater has been determined from the measurement of absorption at 432 nm after the formation of the stable oxo-peroxo-pyridine-2,6-dicarboxylatovanadate(V) complex (OPDV) in acid media. Determinations were in good agreement with those using a modified p-hydroxyphenylacetic acid (PHPA) emission method. The linear range for the OPDV method is from 0.05 to 50 ppm H 2O 2, and the limit of detection under the analytical conditions employed was 5.8 nmol H 2O 2 for a 20 cm 3 rainwater sample. The volume weighted mean H 2O 2 concentration in rainwater collected at roof-top level in central Kowloon was 15.9 μM ( N=10), and the ratio of non-sea salt sulphate and H 2O 2 concentrations was significantly correlated with pH. The OPDV absorption method was also employed for the determination of ambient gaseous H 2O 2, and liquid-nitrogen cold-trap collection gave results about 30% lower than impinger sampling, where artifact H 2O 2 formation occurred.

Relations between acid atmospheric deposition and the surface pH of some ombrotrophic bogs in Britain

1 Analyses are presented of major ion concentrations in surface water samples, and exchangeable cations in peats, collected in November–December 1992 from 16 ombrotrophic bogs in England and Wales and one in Scotland, spanning most of the range from the lowest (Dartmoor, west Wales, west Highlands) to the highest (south Pennines, north Yorkshire) of the mean 1986–88 rainwater concentrations of hydrogen ions and non‐marine sulphate (NMS). 2 There was a strong positive correlation (r = +0.89) between surface water pH and mean rainwater pH, and a less close correlation (r = +0.71) between surface water pH and total hydrogen ion deposition. 3 The correlation between surface water pH and mean concentration of rainwater NMS (which may be taken as a surrogate measure of acid deposition) was r = –0.85, and that between surface water pH and total deposition of NMS was r = –0.65. 4 The intercept of the regression of surface water pH on NMS is at pH 4.40 (95% confidence limits 4.22–4.58), suggesting this as the winter pH of an ombrotrophic bog surface in the absence of acid atmospheric pollution. 5 Total sulphur content of intact surface peats from 11 sites correlated well (r = +0.90) with mean rainwater total sulphate concentration. 6 The H+ ion concentration in wet deposition, plus the net H+ input resulting from metabolism of deposited NO3– and NH4+, is insufficient to account for the difference between the inferred pH of an unpolluted bog surface and pH values (up to 0.8 pH units lower) measured in the field in polluted sites. Analogy with deposition of NMS suggests that this discrepancy is accounted for quantitatively by seeder–feeder enhancement, cloudwater deposition, and dry deposition of acidity. 7 Ombrotrophic bog surface waters are buffered by the cation‐exchange properties of the peat. They are likely to be less sensitive to moderate acid deposition than weakly bicarbonate‐buffered near‐neutral peats, soils and fresh waters.

Trifluoroacetic acid from degradation of HCFCs and HFCs: A three‐dimensional modeling study

Trifluoroacetic acid (TFA; CF3 COOH) is produced by the degradation of the halocarbon replacements HFC‐134a, HCFC‐124, and HCFC‐123. The formation of TFA occurs by HFC/HCFC reacting with OH to yield CF3COX (X = F or Cl), followed by in‐cloud hydrolysis of CF3COX to form TFA. The TFA formed in the clouds may be reevaporated but is finally deposited onto the surface by washout or dry deposition. Concern has been expressed about the possible long‐term accumulation of TFA in certain aquatic environments, pointing to the need to obtain information on the concentrations of TFA in rainwater over scales ranging from local to continental. Based on projected concentrations for HFC‐134a, HCFC‐124, and HCFC‐123 of 80, 10, and 1 pptv in the year 2010, mass conservation arguments imply an annually averaged global concentration of 0.16 μg/L if washout were the only removal mechanism for TFA. We present 3‐D simulations of the HFC/HCFC precursors of TFA that include the rates of formation and deposition of TFA based on assumed future emissions. An established (GISS/Harvard/ UCI) but coarse‐resolution (8° latitude by 10° longitude) chemical transport model was used. The annually averaged rainwater concentration of 0.12 μg/L (global) was calculated for the year 2010, when both washout and dry deposition are included as the loss mechanism for TFA from the atmosphere. For some large regions in midnorthern latitudes, values are larger, 0.15–0.20 μg/L. The highest monthly averaged rainwater concentrations of TFA for northern midlatitudes were calculated for the month of July, corresponding to 0.3–0.45 μg/L in parts of North America and Europe. Recent laboratory experiments have suggested that a substantial amount of vibrationally excited CF3CHFO is produced in the degradation of HFC‐134a, decreasing the yield of TFA from this compound by 60%. This decrease would reduce the calculated amounts of TFA in rainwater in the year 2010 by 26%, for the same projected concentrations of precursors.