Chemistry of Rainwater and Cloud Water at Remote Sites in Alaska and Oregon

Abstract

Cloud water and rainwater were examined at remote sites in southeastern Alaska and coastal Oregon using standardized collection and analytical techniques. Cloud water and rainwater were characterized by extremely low concentrations of most ions except SO2−4, Na+, and Cl−. Acidity was greater than expected because of organic acids from unknown sources. Concentrations of NO−3 and NH+4 were extremely low, especially compared to samples collected similarly in the eastern USA. Rainwater did not differ between Alaska and Oregon except in concentrations of Ca2+, Mg2+, K+, Na+, and Cl−. Cloud water generally had higher concentrations of ions than rainwater, especially in NO−3, NH+4, and SO2−4. Ion concentrations were highly variable and non‐normally distributed. Sample sizes in future studies should be large (>40). Cloud water deposition may be very important in terms of potential pollution effects and nutrient cycling in ecosystems with frequent cloud cover.

Nitrogen Excess in North American Ecosystems: Predisposing Factors, Ecosystem Responses, and Management Strategies

“…However, cloudwater deposition can double N inputs in some fog-dominated coastal and mountain forests (Harr 1982, Bormann et al 1989 and elevated N concentrations in bulk precipitation and cloudwater have been measured downwind of urban centers. Low atmospheric N inputs, a long growing season, cationrich soils, and N deficiency suggest that problems with N saturation should be minimal in the Pacific Northwest.…”

“…However, over large areas of North America and Europe, N deposition is significantly higher than levels measured in pristine areas (Weathers et al 1988, Bormann et al 1989, Zö ttl 1990. Nitrogen deposition is believed to increase plant growth in these areas (Kauppi et al 1992, Eriksson andJohansson 1993).…”

Fogwater Chemistry in a Wood-Burning Community, Western Oregon

“…Published reports have focused largely on relatively remote areas. 13 ' 14 Fogwater chemistry in towns and cities in the Pacific Northwest is likely to differ from chemistry in many other areas, partially because of the extensive Use of wood for heating homes in the Pacific Northwest. Air quality in many communities in the Pacific Northwest is affected by residential wood burning for many months of the year.…”

“…14 Sulfate and NC>3w ere much enriched in the Corvallis fogwater samples compared to those from Marys Peak (Marys Peak median values = 12.5 and 1.61 juequivLr 1 , respectively), 14 but the Corvallis samples were even more enriched in NH 4 + (Marys Peak median =1.11 juequiv Lr 1 ). The relatively high concentrations of NH 4 + in the Corvallis samples (median = 361 jtequiv Lr 1 ) probably reflect scavenging of NH 3 emitted from agricultural sources in the valley, which then neutralized fogwater acidity.…”

“…30 For example, concentrations of SO 4 2~ and NO 3~ in Corvallis fogwater were generally much lower than those found in southern California fogwater, 1 ' 2 but were often higher than concentrations found at more remote sites, such as Alaska, 14 and two sites in north coastal California. 13 Ion balances computed using only inorganic ions were often poor (Table I) and cation concentrations always exceeded anion concentrations.…”