Dew Water Research Articles

Dominant factors controlling concentrations of aldehydes in rain, fog, dew water, and in the gas phase

Low-molecular weight aldehyde compounds in rain, fog, dew water, and in the gas phase were measured at urban and suburban mountain sites, to characterize the chemical composition of aldehydes in liquid droplets and in the gas phase in the ambient atmosphere, and discuss the factors controlling wet removal processes of aldehydes. Higher concentrations of total aldehydes were found in dew water than in rain and fog water due to the small amount of water volume. Both formaldehyde and acetaldehyde were detected as dominant aldehydes in the gas phase. Secondary formation processes are dominant sources for both aldehydes in the suburban site, whereas primary sources are relatively important for the urban atmosphere. In rainwater, by contrast, formaldehyde was the most abundant aldehyde, followed by glyoxal. Glyoxal was detected as the most dominant aldehyde in fog and dew water. Acetaldehyde was not detected as a main component in liquid droplets in spite of its abundance in the gas phase. Water solubility of each aldehyde compound and dilution effect by water are critical factors that control the compositions and concentrations of these aldehydes in ambient liquid droplets.

Negative effects of hydroxyl radical‐generating mists (simulated dew water) on the photosynthesis and growth of Japanese apricot seedlings (Prunus mume)

AbstractThe hydroxyl (OH) radical, which is generated in polluted dew water on leaf surfaces of the Japanese apricot (Prunus mume), is known to be a potent oxidant. In order to investigate the effects of the OH radical formed in polluted dew water on the photosynthesis and growth of 3‐year‐old seedlings of P. mume, OH radical‐generating solutions simulating polluted dew water were sprayed in the early morning as a mist throughout a growing season onto the leaf surfaces of seedlings growing in experimental greenhouses. Four OH radical‐generating solutions (0, 6, 18 and 54 μM H2O2 with Fe(III) and an oxalate ion) were used in the mist treatment. Five months after the beginning of treatment, the leaves exposed to the mist containing 54 μM H2O2 showed a significantly smaller maximum CO2 assimilation rate (Amax) and stomatal conductance (gs) as compared to the leaves exposed to the mist containing 0 μM H2O2. Exposure of P. mume seedlings to the OH radical‐generating mist had caused a reduction in the dry weight and relative growth rate (RGR) of the above‐ground parts (stem + branch) at the end of the growing season. A significant positive correlation was shown between RGR and Amax. Thus, the effects of oxidants generated in polluted dew water on leaf surfaces can be considered to be a cause of the decrease in leaf photosynthesis and growth of P. mume.

Enhanced dissolution of volatile organic compounds into urban dew water collected in Yokohama, Japan

Abstract Simultaneous sampling of six chlorinated hydrocarbons (CHs) and five monocyclic aromatic hydrocarbons (MAHs) in dew water and in the ambient air was performed from 1998 to 2000 in Yokohama, Japan. Dichloromethane (volume-weighted mean concentration (VWM): 2.43 nM) and trichloroethylene (VWM: 2.91 nM) were abundant among CHs in dew water, while toluene (VWM: 9.69 nM) and p-dichlorobenzene (VWM: 6.06 nM) were abundant among MAHs. The contribution of total measured volatile organic compounds (VOCs) concentration to dissolved organic carbon (DOC) concentration in dew water was only 0.02 wt% on average. The concentrations of VOCs except for dichloromethane and benzene in dew water were several hundred times higher than those in rainwater collected at the same site. In particular more hydrophobic VOCs with higher octanol–water partition coefficient K OW tended to be concentrated in dew water, indicating that urban dew water has stronger hydrophobicity than rainwater. Dew water contained higher amounts of VOCs than would have been expected from the ambient gas-phase concentrations and Henry's law constants. The enrichment factors, which were defined as the ratio of the observed concentration to the estimated, ranged from 6.98 (for dichloromethane) to 62.7 (for trichloroethylene) on average. Relatively high correlations ( r >0.55) between the enrichment factors of highly hydrophobic VOCs ( K ow >103) and the ratios of DOC to total inorganic ion concentration (TIC), which could be a potential surrogate of surface tension for urban dew water, indicated that the existence of any dissolved organic compounds, which could reduce the surface tension, in dew water also caused the enrichment of highly hydrophobic VOCs.

A comparative study of two large radiative dew water condensers

In order to improve the yield of dew condensation from atmospheric vapor, two large (30 m 2 in area) insulated plane radiative condensers, inclined at 30°, were installed in Ajaccio (Corsica island, France; latitude 41°55′N, longitude 8°48′E). Prototype P1 was elevated such that the underside was open and exposed. Prototype P2, however, was enclosed on all sides and closer to the ground. Both used a special radiative foil that enhances dew formation. The period of observation for P1 was July 22, 2000–November 11, 2001, and for P2 was December 10, 2001–December 10, 2003. All data were compared with respect to the same horizontal calibration plate of polymethylmethacrylate (Plexiglas) placed at 1 m above the ground on a sensitive recording balance. Water yield of both prototypes were compared and correlated against meteorological data (cloud cover, relative humidity, wind speed, condenser temperature and air temperature). Both prototypes exhibit improved performances when compared with the calibration plate: more dew days (+16% and +15% for P1 and P2, respectively); decrease of the humidity threshold (−3% and −4.4% for P1 and P2); increase of dew yields for wind speeds up to 3 m s −1. A model of the mass and thermal exchanges with the ambient air was used. Two adjustable parameters (heat and mass transfer coefficients) are used in the model. The values of these parameters were found larger than the values obtained in continental sites where dew forms with weak wind, thus emphasizing the peculiarities of dew formation in windy islands. When data are reduced with the calibration PMMA data, prototype P1 provided average water yields slightly larger than the enclosed prototype P2, a result that can be attributed to the influence of surface thermal radiation.

Deposition, decomposition and stabilization of peroxides in Santiago City dew waters

Peroxides present in Santiago City dew waters readily decompose with first order kinetics. In order to minimize the loss of peroxides during the time elapsed between deposition and collection, the collectors were pre-treated with a mercury chloride solution. This reduces, but not completely eliminates, the decomposition. A correction is introduced by a comparison of the levels and decomposition kinetics of the samples collected in treated and untreated collectors. The average concentration estimated by this procedure was 8.1 μM. The mechanism of peroxide decomposition and its stabilization is discussed.

Deposition of coarse soil particles and ambient gaseous components dominating dew water chemistry

Dew water characteristics are not as acidic as those of rainwater and fog water, and they are abundant in weak acid components. The dew water components are dominated by the coarse‐mode aerosol rather than the fine‐mode aerosol, and calcium carbonate, the component of soil, is the important chemical species raising the pH of the dew water. Carbon dioxide is deposited as calcium carbonate into dew water and is the only major component released from dew water. The total concentration of carbon dioxide increased with an increase in the dew water pH, while the degassing rate increased with the decrease in dew water pH. In the low‐pH region, the pε values in dew water are lower than those in rainwater, and the dew water is in a reductive state. The concentration of the representative oxidant, hydrogen peroxide, was much lower in the dew water than in the rainwater in Yokohama (dew water, 0.4 μM; rainwater, 13.1 μM in 1998). The representative conjugate base ions of a weak acid, sulfite and hydrogen sulfite ions, are easily oxidized by hydrogen peroxide, and the lower concentration of hydrogen peroxide in dew water may cause the higher concentration of sulfite ion in dew water than in rainwater. The dew water pH is higher than the rainwater and fog water pH, and a weak acid is easily dissolved into the dew water. Therefore these weak acid ions are more abundant in dew water than in rainwater and fog water.

Dew water collector for potable water in Ajaccio (Corsica Island, France)

We report on the development of an inexpensive radiative condenser for collecting atmospheric vapor. Based on the experience gained using a small working model in Grenoble (France), a prototype of 10×3 m 2 was established in Ajaccio (Corsica, France). The condensing surface is a rectangular foil made of TiO 2 and BaSO 4 microspheres embedded in polyethylene and has an angle of 30° with respect to horizontal. The hollow part of the device, thermally isolated, faces the direction of the dominant nocturnal wind. Dew measurements were correlated with meteorological data and compared to dew condensed on a horizontal polymethylmethacrylate (PMMA, Plexiglas) reference plate. The plate served as a reference standard unit and was located nearby. Between July 22, 2000 and November 11, 2001 (478 days), there were 145 dew days for the reference plate (30%), but 214 dew days for the condenser (45%). This yield corresponds to 767 l (3.6 l, on average, per dew day). The maximum yield in the period was 11.4 l/day. Dew mass can be fitted to a simple model that predicts dew production from simple meteorological data (temperature, humidity, wind velocity, cloud cover). Chemical analyses of the water collected from the plate were performed from October 16, 1999 to July 16, 2000 and from the condenser, from July 17, 2000 to March 17, 2001. The following parameters were investigated: suspended solids, pH, concentration of SO 4 2−, Cl −, K +, Ca 2+ ions. Only Cl − and SO 4 2− ions were sometimes found significant. Wind direction analyses revealed that Cl − is due to the sea spray and SO 4 2− to the combustion of fuel by an electrical plant located in the Ajaccio Gulf. Except for a weak acidity (average pH≈6) and high concentration of suspended solids, dew water fits the requirements for potable water in France with reference to the above ions.

Nitrite in rain and dew in Santiago city, Chile. Its possible impact on the early morning start of the photochemical smog

Cations (pH, potassium, sodium, calcium, magnesium, and ammonium) and anions (sulfate, nitrate, nitrite, and chloride) concentrations were measured in Santiago city rain and dew waters collected during the 1995 to 1999. Concentrations measured in dews are considerably higher than those measured in rains. The high ionic concentration present in dew waters could contribute to their corrosion potential. Natural dust makes an important contribution to the ions present in dews, but the presence of rather high sulfate concentrations (up to 900 μeq/l) indicate a significant contribution of anthropogenic sources. A peculiar characteristic of dew waters is the relatively high nitrite concentrations (up to 180 μeq/l). This nitrite can be resuspended into the boundary layer after dew water evaporation, possibly due to the relatively high volatily of ammonium nitrite. This upward flux could constitute an important source of hydroxyl radicals in the early morning, contributing so to the initial steps of the observed photochemical smog.

Variation in CO 2 assimilation rate induced by simulated dew waters with different sources of hydroxyl radical (·OH) on the needle surfaces of Japanese red pine ( Pinus densiflora Sieb. et Zucc.)

The hydroxyl radical (·OH) is generated in polluted dew on the needle surfaces of Japanese red pine ( Pinus densiflora Sieb. et Zucc.). This free radical, which is a potent oxidant, is assumed to be a cause of ecophysiological disorders of declining trees on the urban-facing side of Mt. Gokurakuji, western Japan. Mists of ·OH-generating N(III) (HNO 2 and NO 2 −) and HOOH+Fe+oxalate solutions (50 and 100 μM, pH 5.1–5.4) simulating the dew water were applied to the foliage of pine seedlings grown in open-top chambers in the early morning. Needles treated with 100 μM N(III) tended to have a greater maximum CO 2 assimilation rate ( A max), a greater stomatal conductance ( g s) and a greater needle nitrogen content ( N needle), suggesting that N(III) mist acts as a fertilizer rather than as a phytotoxin. On the other hand, needles treated with 100 μM HOOH+Fe+oxalate solution showed the smallest A max, g s, and N needle, suggesting that the combination of HOOH+Fe+oxalate caused a decrease in needle productivity. The effects of HOOH+Fe+oxalate mist on pine needles were very similar to the symptoms of declining trees at Mt. Gokurakuji.

Harmful effects of radicals generated in polluted dew on the needles of Japanese Red Pine (Pinus densiflora).

• The effects of free radicals, ·OH and ·NO, generated in polluted dew water on needles of Pinus densiflora (Japanese Red pine) were investigated. • ·OH-generating solutions (HOOH with Fe(III) and oxalate ion; ·OH treatment) and ·OH- and ·NO-generating solutions (NO2 - ; ·OH/·NO treatment) were regulated at 25, 50 and 100µmol and pH4.4. HOOH only (HOOH treatment) was used as a control solution. Solutions were applied as a mist to the needle surface of P. densiflora seedlings before dawn twice a week for 3months. • Within a month, net photosynthesis at near saturating irradiance (Pn) and stomatal conductance (gl) of ·OH-treated needles decreased with increasing solution concentration. The HOOH treatment had no effects on any of the measured parameters. Therefore, ·OH in the artificial dews caused the decreases in Pn and gl. In ·OH/·NO-treated needles, gl increased during the experiment, but Pn was unchanged. In all experiments, the characteristics of PSII were not significantly altered. • Free radicals in polluted dew water have harmful effects on the photosynthesis of P. densiflora and compound effects of ·OH and ·NO are different.

Photochemical Formation of OH Radicals in Dew Formed on the Pine Needles at Mt. Gokurakuji

Photochemical formation rates and sources of the hydroxyl (OH) radical were determined in dew water formed on the surface of Japanese red pine (Pinus densiflora) needles of declining (NO2 polluted area) and healthy pine stands at Mt. Gokurakuji located west of Hiroshima city in western Japan. The measured OH radical photoformation rates in dew water (n=10), which were normalized to the rate at midday on May 1 at 34°N, ranged from 0.67 to 5.18 µM h−1 (1M=1mol L−1). The mean value (2.69 µM h−1) was higher than that in dew water collected on a Teflon board and higher than the mean value in rain water published previously. Of the total OH radical formation rate observed in dew water on the pine needles, 16.4 % was estimated to originate from N (III) (NO2− and HNO2) and 24.6 % was estimated to originate from NO3−. There were other sources of OH radical photochemical formation in dew water on the pine needles besides photolysis of NO2− and NO3−.

Use of condensed water vapour from the atmosphere for irrigation in Bahrain

Atmospheric moisture can be condensed as dew and used for small-scale irrigation. In Bahrain, we found that the most favourable conditions for dew condensation persist at dawn. The maximum amount of dew water can be collected in January and the least in August. Three condensation surfaces have been tested; aluminum, glass and polyethylene foils. The average quantity of dew collected on these surfaces was 1.3, 0.8 and 0.3 kg/m 2 per h, respectively. The condensation rate, water vapour content of the air, and the dew points of Bahrain's climate have been reported.

Hydrogen peroxide deposition and decomposition in rain and dew waters

Peroxides and hydrogen peroxide were determined by a fluorometric method in dew and rain collected in the atmosphere of Santiago of Chile city. The measured peroxides comprise hydrogen peroxide (the main component) and peroxides not decomposed by catalase. The collected natural peroxides readily decompose in the natural matrix, rendering difficult an estimation of the values present in real-time. In order to establish the kinetics of the process and the factors that condition their decomposition, the kinetics of the decay at several pHs and/or the presence of metal chelators were followed. The kinetics of hydrogen peroxide decomposition in the water matrix was evaluated employing the natural peroxides or hydrogen peroxide externally added. First-order kinetics was followed, with half decay times ranging from 80 to 2300 min. The addition of Fe(II) in the micromolar range increases the decomposition rate, while lowering the pH (<3) notably reduces the rate of the process. The contribution of metals to the decomposition of the peroxides in the natural waters was confirmed by the reduction in decomposition rate elicited by its treatment with Chelex-100. Dew and rain waters were collected in pre-acidified collectors, rendering values considerably higher than those measured in non-treated collectors. This indicates that acidification can be proposed as an easy procedure to stabilize the samples, reducing its decomposition during collection time and the time elapsed between collection and analysis. The weighted average concentration for total peroxides measured in pre-treated collectors was 5.4 μM in rains and 2.2 μM in dews.

Detection of Chlorothalonil in Dew Water Following Aerial Spray Application and Its Role in the Control of Black Sigatoka in Banana.

A standardized bioassay measuring the growth inhibition of Aspergillus niger in vitro allowed the detection of small concentrations (0.1 to 20 μg/ml) of chlorothalonil present in dew water on both the adaxial and abaxial surface of banana leaves in a commercial plantation receiving aerial sprays. Chlorothalonil concentrations detected in dew water on the banana leaf surface were within the range of concentrations required to prevent Mycosphaerella fijiensis (causal agent of black Sigatoka) ascospore germination in laboratory bioassays. When 9-cm-diameter banana leaf disks inoculated with M. fijiensis ascospores were immersed for 4 h in water containing 0.1 to 0.6 μg of chlorothalonil per ml, ascospore germination was inhibited by 96.9%. The EC50 values for inhibition of ascospore germination were between 0.01 and 0.03 μg/ml for chlorothalonil and between 3.2 and 3.7 μg/ml for mancozeb. Following a 4-h exposure to chlorothalonil and mancozeb, and subsequent removal of the fungicides by a washing step, ascospores failed to germinate, indicating that both fungicides are fungicidal to M. fijiensis, not fungistatic. Recovery analysis of chlorothalonil spray droplet deposits and active ingredient on deposition cards in the field during aerial spray applications indicated that detectable fungicide deposition on the abaxial leaf surface occurs only when the banana leaf-target is vertical or nearly so. The significance of this observation in relation to the control of black Sigatoka with protectant fungicides is discussed.

Effect of Acid Deposition on Urban Dew Chemistry in Yokohama, Japan

Abstract Dews or frosts formed on artificial collectors were collected during the early morning in Yokohama in 1993 and 1994 and analyzed for weak acids as well as major inorganic ions. In 1993 (n = 21) the dew pH ranged from 3.23 to 7.12 and averaged 4.60; in 1994 (n = 56) it ranged from 4.11 to 7.74 and averaged 5.41. Based on the average, NH4+ and Ca2+ were major cations (423 and 178 μequiv L−1 for NH4+ and Ca2+ in 1993, respectively, and 454 and 274 μequiv L−1 in 1994, respectively) and SO42− was the dominant anion (344 μequiv L−1 in 1993 and 271 μequiv L−1 in 1994) in dew water. The dew chemistry was characterized by relatively high concentrations of weak acid anions, particularly hydrogensulfite ion (HSO3−). Dew water sometimes had very high acidity (the minimum pH was 3.23 during the period of this research), which might have been due to the aqueous oxidation of S(IV). From a resistance model calculation, the S(IV) concentration in dew water was suggested to be influenced by the dissolution of HCHO from the atmosphere and the subsequent formation of HMSA.

Initial experiments on dew collection in Sweden and Tanzania

Moisture in the air can be condensed as dew and used for drinking and irrigation. The radiative cooling properties of polymer foils can enhance the performance of dew collecting surfaces. The main restrictions in condensing water in warm and arid locations are climatic factors, the dew collector design, and the optically selective and adhesive properties of the condensing surface itself. This paper concerns observations of dew formation on radiatively cooled pigmented polyethylene foils. The experiments were carried out in Sweden and in arid Dodoma, Tanzania. The results are in agreement with thermodynamical calculations, though the variation is large in the daily measured dew water volumes. This variation is caused by the hourly and daily changes in wind-speed, cloud cover, dry bulb temperature, and dew point temperature. The results are compared with earlier outdoor observations in Tanzania.

Atmospheric aerosol particles and their role in the formation of dew on the surface of plant leaves

Measurements of the electrical conductivity along the surface of leaves or conifer needles show that the wetting of such surfaces coated with wax already starts below a relative humidity of 100%. To explain the observations, the deposition of water soluble atmospheric aerosol particles on these surfaces is taken into account. It is shown that the capillary space between particle and settling surface and, as an additional indispensable condition, the water solubility of at least some constituents of the atmospheric aerosol particle (i.e. a combined capillary-solution effect), permits the formation of condensate or dew water significantly below a r.h. of 100%.

BEHARRA SPRINGS—FAST TRACK DEVELOPMENT OF A SMALL GAS FIELD UTILISING MEMBRANE SEPARATION TECHNOLOGY

The Beharra Springs gasfield was discovered in 1991 in EP320 in the northern Perth Basin. Two wells were drilled on the upthrown side of the Beharra Springs Fault and intersected a gas bearing sandstone near the top of the Early Permian Carynginia Formation. Dry gas flowed at 240 000 cubic m3 (8.5 MMscfd) through a (0.5") choke and at 660 000 m3 (23MMscfd) through a 14.3mm (9/16") choke respectively.The gas field sited 1.6 km from the Dongara to Pinjarra WANG pipeline coupled with the market demand from large industrial consumers (Alcoa) provided the necessary components of a low cost fast track development of a relatively small gas deposit.Following production testing trials, process screening studies commenced in May 1991.Front end design activities commenced in August 1991 and by May 1992, some nine months later production of 15 terajoules per day (TJ/d) of pipeline specification gas flowed from the gas field to Alcoa in Pinjarra.The $10 million gas processing and pipeline facilities include:Low temperature dehydration facilities utilising gas expansion cooling (Joule Thompson effect) and heat exchange to reduce gas temperature to -15°cat eight MPa. (Wellhead pressure initially 26 MPa) to ensure the gas meets water and hydrocarbon dew point specification.Semi-permeable membranes, made from thin films of polymer, to reduce the corrosive gases carbon dioxide and hydrogen sulphide form six per cent to 2.5 per cent and 10 ppm to 3.2 ppm respectively to meet pipeline specification. The membranes operate at 7.5 MPa.The use of skid mounted process modules and technology utilising the pressure inherent in the gas field to avoid the use of large rotating equipment and process chemicals were the other essential components utilised in quickly developing the Beharra Springs gas discovery into an efficient gas production facility.

Dew and frost chemistry at a midcontinent site, United States

From July 1989 to July 1990 a total of 98 dew and 9 frost samples were collected at the University of Arkansas Agricultural Experiment Station, Fayetteville. The total water flux from dews and frosts per year was less than 2% of that from rains. Acid and nutrient fluxes were also much lower in dew. In the following series of ions the number in parentheses gives the percent of the yearly flux of the ion in dew compared to rain for the same time period: H+ (0.06), Ca2+(25), Mg2 + (11), K+ (21), Na+ (4), NH4+ (10), Cl− (4), NO3− (5), and SO2−4 (5). In contrast, the concentration of the various ions in dew, except H+, is generally several times that in rain. Dew is primarily a Ca(HCO3)2 and (NH4)2SO4 solution; whereas rain is primarily a NH4HSO4 solution. The mean pH of dew is 6.37 compared to 4.99 for rain. The average acetate‐formate concentration of dew in equivalents was (1) equal to about 53% of the nitrate‐sulfate concentration in rain for April‐June and (2) 10 times more concentrated than in rain for the year. The steps governing dew composition are indicated to be (1) formation on dry deposition solids (2) dissolution of the soluble portion of the dry deposition by dew water, and (3) sorption of gaseous NH3, acetic, and formic acids into the dew solution.

The influence of manganese leached from plants on dew chemistry

Abstract High concentrations of manganese, which are believed to be catalytically active for the oxidation of sulfite, are found in dew water on grass. In order to describe this oxidation the reaction was studied in a fog chamber. In the concentration and pH range normally found in dew on grass, the formation of sulfate is linearly dependent on the concentration of manganese and on the square root of the concentration of sulfite. The results indicate that the manganese‐catalyzed sulfite oxidation is an important reaction in dew on grass.