Dew and frost chemistry at a midcontinent site, United States
- Univ. of Arkansas, Fayetteville (United States)
- Illinois State Water Survey, Champaign (United States)
Little national effort is being devoted to appraising the importance of dew in the research on acid rain and atmospheric pollutants. Because dew lingers directly on plants and is perhaps more concentrated than rain, especially during its evaporation, it may overshadow certain rain effects which work mainly through the soil. 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[sup +] (0.06), Ca[sup 2+] (25), Mg[sup 2+] (11), K[sup +] (21), Na[sup +] (4), NH[sub 4][sup +] (10), Cl[sup [minus]] (4), NO[sub 3] (5), and SO[sub 4][sup 2[minus]] (5). In contrast, the concentration of the variations in dew, except H[sup +], is generally several times that in rain. Dew is primarily a Ca(HCO[sub 3])[sub 2] and (NH[sub 4])[sub 2]SO[sub 4] solution, whereas rain is primarily a NH[sub 4]HSO[sub 4] 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 NH[sub 3], acetic, and formic acids into the dew solution. 17 refs., 5 tabs.
- OSTI ID:
- 7025041
- Journal Information:
- Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 97:D18; ISSN 0148-0227; ISSN JGREA2
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
540220* -- Environment
Terrestrial-- Chemicals Monitoring & Transport-- (1990-)
540320 -- Environment
Aquatic-- Chemicals Monitoring & Transport-- (1990-)
ACID RAIN
ATMOSPHERIC PRECIPITATIONS
CHARGED PARTICLES
CHEMICAL COMPOSITION
DISSOLUTION
HYDROGEN COMPOUNDS
INORGANIC ACIDS
IONS
OXYGEN COMPOUNDS
PH VALUE
RAIN
SORPTION
WATER