Fog and Precipitation Chemistry at Mt. Rokko in Kobe, April 1997-March 1998

Fog water and precipitation were collected and analyzed to study fog and precipitation chemistry. The research was carried out through one year from April 1997 to March 1998 at Mt. Rokko in Kobe. Higher fog occurrence and larger volume of fog water were observed in summer, corresponding to the trend of seasonal variation in precipitation amount. The annual mean pH value of fog water (3.80) was lower by ca. one pH unit than that of precipitation (4.74). The concentration of chemical species in fog water was ca. 7 times that in precipitation. The highest anion and cation concentrations were SO₄ ^2? and NH₄ ⁺ in fog water and Cl^? and Na⁺ in precipitation, although the Cl^?/Na⁺ equivalent ratio in both fog water and precipitation was almost the same value as that in sea water. It is considered that in the longest fog event, NH₄ ⁺ and nss-SO₄ ^2? in fog water mainly scavenged as (NH₄)₂SO₄, mainly derived from (NH₄)₂SO₄ (aerosol) in the atmosphere, NH₃ was scavenged at the growing stage, and SO₂ was also scavenged after the mature stage. NO₃ ^? in this fog event was mainly absorbed as HNO₃.     

Nutrient Input Through Occult and Wet Deposition into a Subtropical Montane Cloud Forest

Chemical composition of fog and rain water was studied during a 47-day experimental period. The differences between the fog and rain water were found to be significantly for most analyzed ions. H⁺, NH₄ ⁺, NO₃ ^?, and SO₄ ^2? made up 85% of the total median ion concentration in fog and 84% in rain water. The total mean equivalent concentration was 15 times higher in the fog than in the rain water. The fog water samples were classified according to their air mass history. The analysis of the 120 h backward trajectory led to the identification of three advection regimes. Significant differences of ion concentrations between the respective classes were found. Air masses of class I travelled exclusively over the Pacific Ocean, class II were carried over the Philippines, and class III were advected from mainland China. The turbulent fog water deposition was determined by the means of the eddy covariance method. The total (turbulent plus gravitational) fog water fluxes ranged between +31.7 mg m^?2 s^?1 and ?56.6 mg m^?2 s^?1. Fog water droplets with mean diameters between 15 μm and 25 μm contributed most to the liquid water flux. The sample based nutrient input was calculated on the basis of the occult and wet deposition, and the concentrations of the simultaneously collected fog and rainwater samples, respectively. The nutrient input through wet deposition was about 13 times higher than through occult deposition.     

Cloud Water Deposition to Forest Canopies of Cryptomeria Japonica at Mt.Rokko, Kobe, Japan

Cloud water deposition to canopies of Cryptomeria japonica at Mt.Rokko, Kobe, Japan, was estimated from throughfall measurements and fog water collections carried out during a full year. Annual cloud frequency was 11.5–15.5% and liquid water content (LWC) was 0.059 g/m³. Since cloud water deposition on to forest canopies was significantly correlated with the amount of fog water collected, the former parameter could be quantitatively derived from throughfall measurements. Annual cloud water deposition on to Cryptomeria canopies was 1420–2860 mm (Av. 2140 mm), corresponding to 90–180% (Av. 122%) of annual rainfall. The rate of deposition was higher at the mountain ridge and the forest edge than at the mountain side and the forest interior. Annual deposition of SO₄ ^2?, NO₃ ^?, H⁺ and NH₄ ⁺ from cloud water was estimated as 204, 153, 2.5 and 58 kg/ha, respectively, equivalent to 5.8–11.7 times the corresponding deposition via rain. The values are equal to, or exceed, the maximum deposition reported for Appalachian forests in the eastern United States. Multiple regression analyses indicate that cloud water deposition on to Cryptomeria canopies was significantly correlated with the following three parameters: cloud frequency, LWC, and wind speed. Thus, these three factors apparently control cloud water deposition on to forest canopies.     

Long Term Trend of Chemical Constituents in Tokyo Metropolitan Area in Japan

In recent years, acid rain has been a social problem all over the world. In Japan, it is also a big problem especially in the metropolitan area. Then, we have measured major ions such as H⁺, Na⁺, NH₄ ⁺, K⁺, Mg²⁺, Ca²⁺, Cl^?, NO₃ ^?, and SO₄ ^2? in precipitation and dry deposition samples which had been collected at 9 sampling sites at Hiyoshi, Mita, Kashiwa, Shiki, Fujisawa, Yokosuka, Mitaka, Hachiouji, and Ashikaga in Tokyo Metropolitan area for 10 years since 1990. The average pH of precipitation in their sites was 4.56 (n=1906). As the results of multiple regression analysis showed that pH of precipitation was determined by 5 ions such as NH₄ ⁺, nssCa²⁺(non sea salt calcium), nssCl^?(non sea salt chloride), NO₃ ^?, nssSO₄ ^2?(non sea salt sulfate) in the most of the sampling sites. Therefore, it is very important to investigate the behavior of these ions to understand the acidification of rain in Tokyo Metropolitan area. In this study, a long term trend of each ion concentration in precipitation and wet deposition was also investigated the base on the data we had observed at 7 sites for 10 years by the statistical method.     

Fog- and Rainwater Chemistry in the Tropical Seasonal Rain Forest of Xishuangbanna, Southwest China

Fogwater, fog drip and rainwater chemistry were examined at a tropical seasonal rain forest in Xishuangbanna, southwest China between November 2001 and October 2002. During the period of observation, 204 days with the occurrence of radiation fog were observed and the total duration of fog was 1949 h, of which 1618 h occurred in the dry season (November to April), accounting for 37.0% of the time during the season. The mean pH of fogwater, fog drip and rainwater were 6.78, 7.30, and 6.13, respectively. The ion with the highest concentration for fog- and rainwater was HCO₃ ^?, which amounted to 85.2 and 37.3 μeq l^?1, followed by Ca²⁺, Mg²⁺ and NH₄ ⁺. Concentrations of NO₃ ^?, HCO₃ ^?, NH₄ ⁺, Ca²⁺, and K⁺ in fogwater samples collected in the dry season were significantly greater when compared to those collected in the rainy season. It was found that the ionic concentrations in fog drip were higher than those in fogwater, except for NH₄ ⁺ and H⁺, which was attributed to the washout of the soil- and ash-oriented ions deposited on the leaves and the alkaline ionic emissions by the leaves, since biomass burns are very common in the region and nearby road was widening.     

Chemical Composition of Precipitation, Throughfall and Soil Solutions at Two Forested Sites in Guangzhou, South China

Rain water at two forested sites in Guangzhou (south China) show high concentrations of SO₄ ^2?, NO₃ ^? and Ca²⁺ and display a remarkable seasonal variation, with acid rain being more important during the spring and summer than during the autumn and winter. The amount of acid rain represents about 95% of total precipitation. The sources of pollutants from which acid rain developed includes both locally derived and long-middle distance transferred atmosphere pollutants. The seasonal variation in precipitation chemistry was largely related to the increasing neutralizing capacity of base cations in rainwater in winter. Soil acidification is highlighted by high H⁺ and Al³⁺ concentrations in soil solutions. The variation in elemental concentration in soil solution was related to nitrification (H⁺, NH₄ ⁺ and NO₃ ^?) and cation exchange reaction (H⁺, Al³⁺) in soil. The negative effect of soil acidification is partly dampened by substantial deposition of base cations (Ca²⁺, Mg²⁺ and K⁺) in this area.     

Stability of Ionic Components in Precipitation Samples — A Case Study in Taipei

The changes in ionic contents were studied in acidic precipitation samples collected for precipitation events in Taipei, which is near the sea. The storage cases under investigation include filtration, refrigeration, and light. Thus the experimental design leads all precipitation samples collected in the same rain event stored under different conditions. They were then analyzed six times successively within two months to provide the information containing potential ionic composition change. The measured constituents are H⁺, K⁺, Na⁺, Ca²⁺, Mg²⁺, NH₄ ⁺, NO₃ ^?, SO₄ ^2?, and Cl^?. The comparison of measured ionic concentrations corresponding to different storage methods yield no significant difference. The increases of NO₃ ^? and decreases of NH₄ ⁺ with time were observed to be of similar magnitude, while the variation of pH values is significant. The presented study indicated the important role played by sample storage in determining the ionic composition of precipitation samples.     

Evalution of Acid Deposition in Korea

This study was carried out to evaluate acid depositions and to understand their effect. Wet precipitation has been collected at twenty-four sites in Korea for one year of 1999. The ion concentrations such as H⁺, Na⁺, K⁺, Mg²⁺, NH₄ ⁺, Ca²⁺, Cl^?, NO₃ ^? and SO₄ ^2? were chemically analyzed and determined. Precipitation had wide range of pH(3.5～8.5), and volume-weighted average was 5.2. The contribution amounts of Cl^?, SO₄ ^2? and NO₃ ^? in anion were shown to be 54%, 32%, and 14%, respectively and those of Na⁺ and NH₄ ⁺ in cation were 32% and 25%. The ratios of Cl^? and Mg²⁺ to Na⁺ in precipitation were similar to those of seawater, which imply that great amount of Cl^? and Mg²⁺ in precipitation could be originated from seawater. The concentration of H⁺ is little related with SO₄ ^2?, NO₃ ^? and Cl^? ions, whereas nss^?SO₄ ^2? and NO₃ ^? are highly correlated with NH₄ ⁺, which could suggest that great amount of SO₄ ^2? and NO₃ ^? exist in the form of ammonium associated salt. The annual wet deposition amounts (g m^?2year^?1) of SO₄ ^2?, NO₃ ^?, Cl^?, H⁺, NH₄ ⁺, Na⁺, K⁺, Ca²⁺ and Mg²⁺ were estimated as 0.88～4.89, 0.49～4.37, 0.30～9.80, 0.001～0.031, 0.06～2.15, 0.27～4.27, 0.10～3.81, 0.23～1.59 and 0.03～0.63.     

Analysis of summertime cloud water measurements made in a Southern Appalachian spruce forest

This paper presents an analysis of cloud water measurements made during the summers of 1986 and 1987 at Whitetop Mountain, Virginia (36.639° N, 81.605° W). Analysis of cloud water chemistry, cloud type, and air mass origin are made for each cloud event occurring during one 3 to 4 week measurement ‘intensive’ per year. Regional source/receptor relationships are also investigated. Cloud water concentrations of major ions (i.e., H⁺, SO₄ ^2?, NO₃ ?, and NH₄ ⁺) are consistently higher during orographically formed ‘cap’ cloud events. Differences in cloud liquid water content between cap and frontal cloud events explains most, but not all, of the cloud water ion concentration differences. The remaining difference can be explained by greater rainfall associated with frontal cloud events. Most of the cloud water sulfate measured at Whitetop Mountain is apparently due to nucleation of aerosol sulfate within cloud droplets and not to local in-cloud aqueous phase SO, oxidation. No strong source/ receptor relationships were evident from this analysis. Most 72 hr air trajectories arriving at Whitetop Mountain during the cloud events described in this paper originated in the southeastern United States. Few came from the Ohio River Valley or the northeastern United States.     

Forest decline in the boreal montane ecosystems of the southern Appalachian Mountains

Research was initiated in 1984 in an attempt to quantify and test possible hypotheses for the systematic decline and mortality of red spruce (Picea rubens Sarg.) observed in the southern Appalachian Mountains. Field surveys have documented increases in decline symptoms. By 1986, 7% of all tagged red spruce trees in permanent plots were dead. This number, partially due to the effects of severe weather, increased to 41% in 1987. An insect and disease survey initiated in 1985 on 100 permanent plots has yielded little significant pathology or insect infestation. With the exception of the balsam wooly adelgid (Adelges picea (Ratz)), few signs or symptoms of disease or insect attack were noted on either Fraser fir (Abies fraseri) (Pursh Poir) or red spruce populations. Cultures from destructively-sampled root systems yielded few significant pathogens that could contribute to decline symptoms. Measurements of throughfall in 1986 yielded estimates of total wet deposition for NO₃ ^? and SO₄ ^2? of 25 and 75 kg ha^?1 yr^?1 respectively. Using net throughfall quantities, we estimate that between 40 and 60% of this input was due to cloud impact. Mean-volume-weighted pH per cloud event was 3.5. Over 75% of the cloud events sampled had a pH < 4.0. Cloud and rain water was dominated by H⁺, NH₄ ⁺, NO₃ ^?,, and SO₄ ^2? ions. Interaction with the forest canopy resulted in an enrichment of throughfall with base cations (K⁺, Ca²⁺, and Mg²⁺) and a loss of H⁺ and NH₄ ⁺. Mean-volume-weighted pH for throughfall was 3.9. The effects of simulated acidic cloud water on the epicuticular waxes of red spruce needles were studied during the summer of 1987. The cuticle proper of both 1986 and 1987 needles did not appear to be damaged by the treatments. The wax crystals which constitute the stomatal wax plugs, however, exhibited substantial degradation by simulated treatments at or below pH 3.5.     

Chemistry of Fog Water Collected in the Mt. Rokko Area (Kobe City, Japan) between April 1997 and March 2001

Fog chemistry was studied for four years (April 1997–March 2001) at Mt. Rokko (altitude 931 m) in Kobe, Japan. A collection of samples was obtained at a mountainous site close to a highly industrialized area. The samples were collected by an active string-fog collector. The summer fog was dense and frequent. The geography of Mt. Rokko is linked to the seasonality of the occurrence and the thickness of the fog. Among the meteorological parameters, the relative humidity was important for the occurrence of fog. The correlation of the concentrations of the components in fog water indicated that (NH₄)₂SO₄ and/or NH₄HSO₄ were involved in the process of the formation of fog drops in the atmosphere. The concentration of the components decreased with an increase in the liquid water content (LWC) of the fog, and the seasonal variation of the concentration of some components depended on the seasonal variation of the LWC. The equivalent ratio of NO₃ ^? to non-sea salt (nss?) SO₄ ^2? was considerably larger than that in precipitation. Ammonium ion accounted for the largest percentage of cations, which indicates that NH₄ ⁺ was an important counter cation for NO₃ ^? and nss-SO₄ ^2?. A unique fog event in which the air pollutants seemed to be scavenged stoichiometrically was sometimes observed. The methodology used for collecting fog water at 60 mL intervals provided detailed information.     

Throughfall Chemistry in a Sitka Spruce Plantation in Response to Six Different Simulated Polluted Mist Treatments

A mixed provenance Sitka spruce plantation, planted in 1986 on a drained deep peat, has been exposed to 6 different simulated mist treatments in 4 replicated blocks since 1996. Treatments provided N and/or S at a concentration of 1.6 mol m^?3, supplying ca. 50 kg S and/or N ha^?1 yr^?1 as N (NH₄NO₃), S (Na₂SO₄), NS Acid (NH₄NO₃ + H₂SO₄ at pH 2.5), 2NS Acid (double dose by application at twice frequency), a control treatment supplied with additional rainwater only and a 'no treatment' set of plots. Throughfall, preserved with thymol in the field, was collected using gutters with a surface area of 1 m² in all the replicate plots, and was analysed for all major ions. Prior to treatment in 1999, S deposition in throughfall exceeded that in rain because of dry deposition of SO₂ and SO₄ ^2? to the canopy; NH₄ ⁺ and NO₃ ^? ions were both retained in the canopy. During treatment, only 20–40% of the applied N in the high-N treatments was retained in the canopy. Acidity in the applied mist was partly neutralised by the canopy, but not primarily through exchange of base cations, leading to the conclusion that weak organic acids, in solution or in situ in the canopy, contributed to the buffering of the H⁺ ion deposition in the acid treatments.     

Fine and Coarse Ionic Aerosol Components in Relation to Wet and Dry Deposition

The distribution of acidic andalkaline constituents (SO₄ ^2-,NO₃ ^-, Cl^-, NH₄ ⁺, Na⁺,K⁺, Ca²⁺) between the fine and coarseparticle range has been examined in an urban locationin Thessaloniki, N. Greece over an 8-month period. The chemistry of wet and dry deposition collected overthe same period was also examined. Statisticalassociations between species within each environmentalphase were investigated using correlation analysis.Use of principal component analysis was made toinvestigate compositional similarities betweenaerosol, deposited dust and rain. It was found thatSO₄ followed by NO₃, NH₄ and Caprevailed in fine aerosol. Sulphates and Ca were alsothe prevailing ions in the coarse particle fraction.Wet deposition was found to be the dominant depositionmechanism for all species. The high dry depositionrates observed for Ca and SO₄ suggest that mostof the dry deposited sulphate is in the form ofCaSO₄. Scavenging ratios of ionic speciesassociated with coarse aerosol were higher than thecorresponding ratios for fine particles. Principalcomponent analysis suggested that variations in ioniccomposition of fine aerosol could be interpretedprimarily by gas-to-particle neutralization reactionsinvolving atmospheric ammonia. In contrast, theinteraction between SO₂ and HNO₃ with Cacompounds seems to be the most likely factor that canexplain variations in wet and dry deposition ioniccontents.     

The geographical distribution and temporal variations of acidic deposition in Eastern North America

Data from two national precipitation chemistry monitoring networks, and several regional air and precipitation chemistry networks are used to describe some broad-scale features of acidic deposition in eastern North America. In northeastern North America, the coefficient of variation is shown to increase from 10–16% for annual averages to nearly 100% for daily values. There is a strong annual cycle in H⁺, SO _inf4 ^sup= and NH _inf4 ^sup+ deposition and some of the other ions although these cycles are not all in phase. The wet NO _inf3 ^sup? deposition contributes relatively more than SO _inf4 ^sup= to the acidity of snow as compared to rain. Wet deposition is highly “episodic” with about 50% to 70% of the total annual deposition of SO _inf4 ^sup= and NO _inf3 ^sup? accumulating in the highest 20% of the days. Estimates made in various ways indicate that, over eastern North America as a whole, dry deposition is approximately equal to wet for both SO _inf4 ^sup= and NO _inf3 ^sup? . Dry may exceed wet in the high emissions zone but drops to about 20% of the total deposition in more remote areas. Deposition via fog or low cloud impaction is an important input to high elevation forests, but more data are required to quantify the magnitude and regional extent of this.     

Sequential sampling and variability of acid precipitation in Hampton,Virginia

Rain samples were collected sequentially by amount (≈2.7 mm each) from individual events at a single, relatively isolated, suburban site from August 1977 to July 1980. Rain pH's for ≤ 3 mm samples closely fit a monomodal Gaussian distribution with a median of 4.50 and a standard deviation of 0.39. The variability in pH was primarily interevent as opposed to intraevent. The 3-yr volume-weighted pH was 4.35 ± 0.02 for 3.16 m collected; annual pH's were 4.31, 4.37, and 4.38, and cumulative H⁺ deposition was 141 mg H⁺ m^?2. Event-averaged rain pH and meteorological and air quality data were correlated. Low pH was associated with low rainfall volume and rate; rain after several dry days; rains with northeast surface winds; high SO₂, NO₂, and O₃ in the ambient atmosphere; and high, strongly correlated, SO₄ ⁼ and NO₃ ^? rainwater concentrations. The lowest 3-yr seasonal average pH (4.31) occurred during summer; values for other seasons were ≈4.37. Average intraevent H⁺ molarity (volume-weighted) was accurately characterized by 6.89 E^{?5 *}(mm ram)^?0.215. The relative merits of composite (e.g., whole event) and sequential sampling are examined.     

Throughfall and canopy buffering in three sitka spruce stands in Denmark

Throughfall was studied in three even-aged sitka spruce stands in Denmark during the years 1989 to 1994. Deposition of sea salts dominated the fluxes of substances in varying degrees between years and sites. During the study period, non-marine S deposition did not change substantially. At the site most affected by animal husbandry, fluxes of NH₄ ⁺ and NO₃ ^? increased over the years. Elevated fluxes of TOC, K⁺, and PO₄ ^3? occurred in the growing season due to canopy leaching caused by attacks by the green spruce aphid. Fluxes of Cl^?, SO₄ ^2?, Na⁺, Ca²⁺, and Mg²⁺ were highest in the dormant season. Buffering of. pH was affected by the nitrogen dynamics in the canopy, and also, at least during the summer, by elevated levels of organic compounds.     

Fracht an chemischen Elementen in den Niederschlägen im Solling

Loading of chemical elements in precipitation at the Solling For the period 1969–1976 (NH₄, NO₃: 1971–1976) monthly values of concentrations and flows of the ions NH₄, H, Na, K, Ca, Mg, Fe, Mn, Al, Cl, NO₃, SO₄, P and organic bound N in precipitation are passed on. From the correlations between elements the following main ion sources are concluded: sea water (Na, Cl), combustion processes (SO₄, NO₃, NH₄), lime dust after dissolution by H₂SO₄ and HNO₃ (Ca, Mg), soil dust after dissolution by H₂SO₄ and HNO₃ (Al, Fe), leaching from plants (K, NO₃, SO₄, Mg, Ca), biogenic contaminations (P, organic N, K, NH₄, NO₃). Seasonal variations in the concentrations are most evident for Na and Cl, less for NH₄, SO₄ and NO₃. During the measuring period the flux of NH₄ is significantly increased; for H and SO₄, less for NH₄, Mg, Ca and Fe, the increasing trend was interrupted in winter 1973/74 (oil crisis). Consequences for sampling are discussed.     

Ten years of precipitation chemistry in Haifa,Israel

Rain event samples have been collected in Haifa, Israel, for nine hydrological years 1981 to 1990. Precipitation amount, pH, SO₄ ⁼, NO₃ ^?, Cl^?, NH₄ ⁺, Na⁺, K⁺, Ca⁺⁺, Mg⁺⁺ and alkalinity of rainwater samples were recorded. The sampling and analysis program was based on WMO recommendations for background networks. The sampling was performed manually, and the analysis was based on wet chemistry for ions and atomic absorptions for metals. Data of 187 rain samples showed that the average pH was 5.3±1.1∶ 26% of the rain events were below pH of 5.6 and 23% above pH of 7.0. Some simple chemical mass-balance considerations indicate that natural sources, sea salt and soil carbonates are the main contributors to rain chemistry. However, the presence of low pH events observed over the years suggests that the impact of anthropogenic emissions may overwhelm the buffering capacity of the alkaline aerosol.     

Storage and release of major ionic contaminants from the snowpack in the Turkey Lakes Watershed

The chemistry of the snowpack and snowmelt was investigated at the Turkey Lakes Watershed during the spring melt period in 1985. Ions in the snowmelt were 2 to 10 times more concentrated than those in the pre-melt snowpack and approximately 50% of the H⁺, SO₄ and NO₃ were lost from the snowpack with the first 30% of the melt. Rainfall flowed directly through the snow cover even during the early stages of the melt. Four rain events, which accounted for only 18% of the flowthrough collected, were responsible for about 50% of the H⁺ and SO₄ and 37% of the NO₃ ions exported from the snowpack. Sulphate to nitrate equivalent ratios in the pre-melt snowpack were generally about 0.6 but an enrichment of S04 relative to N03 in atmospheric deposition during the spring (SO₄:NO₃ > 1) resulted in snowmelt with an increasing SO₄ content relative to NO₃.     

Geographical and Temporal Variations of Chemical Constituents in Winter Precipitation Collected in the Areas along the Coast of the Sea of Japan

The geographical and temporal variations of chemical constituents in winter precipitation collected in the areas along the coast of the Sea of Japan (AASJ) were discussed by analyzing the data obtained in the 1st and 2nd National Acid Deposition Survey by Japan Environmental Laboratories Association. In western Tohoku (WT) and Hokuriku (HR) areas in AASJ, in spite of large amounts of precipitation in winter, concentrations of non sea salt (nss-)SO₄ ^2? are not as low as the other areas, and nss-Ca²⁺ in these areas is lower than the other areas. As a result, H⁺ concentrations of precipitation in these areas are somewhat higher than other areas. From the temporal analysis of daily sampled data and back trajectory analysis of air mass, it was found that the concentrations of nss-SO₄ ^2?, NO₃ ^?, NH₄ ⁺ and nss-Ca²⁺ are correlatively varied when air mass come from the Asian Continent, showing higher concentrations at the western sites in AASJ and depending on the meteorological conditions such as the direction of in flow air mass.