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1.
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.  相似文献   

2.
Sulfate (SO4 2?), nitrate (NO3 ?) and ammonium (NH4 +) concentrations in precipitation as measured at NADP sites within the Ohio River Valley of the Midwestern USA between 1985 and 2002 are quantified and temporal trends attributed to changes/ variations in (i) the precipitation regime, (ii) emission patterns and (iii) air mass trajectories. The results indicate that mean SO4 2? concentrations in precipitation declined by 37–43% between 1985 and 2002, while NO3 ? concentrations decreased by 1–32%, and NH4 + concentrations exhibited declining concentrations at some sites and increasing concentrations at others. The change in SO4 2? concentrations is in broad agreement with estimated reductions in sulfur dioxide emissions. Changes in NO3 ? concentrations appear to be less closely related to variations in emissions of oxides of nitrogen and exhibit a stronger dependence on weekly precipitation volume. Up to one quarter of the variability in log-transformed weekly NO3 ? concentrations in precipitation is explicable by variations in precipitation volume. Trends in annual average log-transformed SO4 2? concentrations exhibit only a relatively small influence of variability in weekly precipitation amount but at each of the sites considered the variance explanation of annual average log-transformed SO4 2? by sampling year was increased by removing the influence of precipitation volume. Annual mean log-transformed ion concentrations detrended for precipitation volume (by week) and emission changes (by year) exhibit positive correlations at all sites, indicating that the residual variability of SO4 2?, NO3 ? and NH4 + may have a common source which is postulated to be linked to synoptic scale variability and air mass trajectories.  相似文献   

3.
Nutrient content and pH of precipitation samples collected at six sites during 1971–1973 were studied to determine the fraction of rainfall and snowmelt and the amounts of N, S, and P added by precipitation over Iowa The amount of NH4-N ha?1 added by precipitation annually at each site was about equal to that added as N03-N. The amounts of inorganic N ha?1 yr?1 added ranged from 10 kg in north-central to 14 kg in west-central Iowa, and the annual amounts of S04-S ha?1 added ranged from 13 kg in northeastern to 17 kg in north-central Iowa. It is estimated that, on average, precipitation adds about 0.6 kg of NH4-N, 0.6 kg of N03-N, and 1.5 kg of S04 -S ha?1 monthly in Iowa. However, the data indicated that, on an annual basis, the contribution of precipitation to P in soil is very small; at the most, about 0.1 kg of water-soluble P04-P ha?1 was added annually in Iowa. No N02-N could be detected in any of the precipitation samples analyzed. Average pH value of the rainfall and snowmelt samples collected at each site during each year was about 6, individual samples seldom reached as low as pH 4. The data indicate that the concentration of S04-S in precipitation in this region is seasonal, high during fall and winter and low during spring and summer.  相似文献   

4.
R. Kickuth  K. Tubail 《Geoderma》1976,16(5):433-442
The precipitation of Fe(II)-phosphates and -hydroxides by interactions of Fe(II)-sulphate and Na3PO4 in aqueous solutions of pH 2–13 at room temperature has been investigated. The results of potentiometric titration were similar to those reported in literature. On the other hand, no stoichiometric compound has been found among the precipitation products in the whole pH-range, as for example, FeHPO4, Fe3(PO4)2 and Fe(OH)2. All precipitation products contain PO4-groups and OH-groups in various proportions depending on the pH during their formation. FeHPO4 may be regarded as a hypothetical initial compound, when precipitation begins at about pH 2 and Fe(OH)2 as the end-product at very high pH-values, respectively. Fe3(PO4)2 does not occur except in the form of partially hydrolyzed species in a neutral milieu. All these compounds form a continuous system of non-stoichiometric phosphates and hydroxydes, respectively. The situation is even more complicated with sodium present in solutions, and this is not due to surface adsorption.The composition of the precipitates plotted against the pH-values do show some peculiarities, which clearly divide the “field of precipitation” into two regions: that of non-stoichiometric phosphates and that of non-stoichiometric hydroxides. The transition point has been defined as a pH-value at which PO4- and OH-groups in the precipitates are interchangable most easily. This occurs at a pH of 8,8. The composition of this “transition product” may be written as FeOH(PO4)0,33.  相似文献   

5.
A statistical analysis of the precipitation data base from the Integrated Lake-Watershed Acidification Study (ILWAS) is presented. Included in this analysis are: equivalence of distributional form of the concentrations, ion pair concentration analysis, regression by site and season, precipitation type, and multiple regressions. The analysis emphasizes the ions: H, NH4, SO4, and NO3. Variability in H is explained largely through SO4 and NO3; spatial variability for the species pairs SO4-H, NO3-H, SO4-NH4; and NO3-NH4 does not suggest significant differences between sites on a seasonal basis.  相似文献   

6.
R Kickuth  K Tubail 《Geoderma》1976,16(3):219-234
The products obtained by precipitation of iron(III)-phosphates in the pH-range from 2 to 13.35 differ in their composition from the ones reported in the literature, e.g. FePO42H2O or FeH2(OH)2PO4, except at low pH values.The molar ratio of 1 : 1 for P and Fe is disturbed to a significant extent and foreign ions are also incorporated as integral parts of the precipitation products.The change of the P/Fe ratio within the pH-range from 2 to 11 is the result of continuous substitution of OH? for PO4? ions. This exchange may be explained as a transition between phosphate- and hydroxide-“Defektserie” (reference is to sets of compounds which form partial rather than complete isomorphous series), whereby the critical composition and the critical precipitation product are defined by the inflection point of the exchange curve.During the hydrothermal recrystallization of amorphous precipitation products, crystalline iron phosphate (strengite) is formed at low pH values, and crystalline iron hydroxide is formed at high pH values. The precipitation products formed at intermediate pH values have a heterogeneous composition and fail to crystallize under these conditions.  相似文献   

7.
The paper presents results of a stoichiometric calculation of a nitrogen (N) compounds in precipitation of World Meteorological Organization's Global Atmosphere Watch (WMO GAW) stations. Long-term trends of ammonium sulphate ((NH4)2SO4) and ammonium nitrate (NH4NO3) contents i the North-West of Russia as well as in Byelorussia, Scandinavia, Western and Eastern Europe during the periods of 1958–1990 and 1972–1985 were investigated. A relatively, steady annual trend for the mean NH4NO3 concentrations was found typical of pure regions (5–15μeq* 1?1). The concentrations in industrial regions are from 4 to 5 times higher than the background close to natural. The analysis of the trend for (NH4)2SO4 content in precipitation shows a wide range of a variations of mean annual concentrations with an explicit tendency to their significant decrease in some European regions in the mid-eighties. Nitric acid (HNO3) has not been discovered in precipitation from the European WMO GAW stations while calculations based on the US data revealed its remarkable content and tendency to its increase. Nitric acid and ammonium sulphate are not contained in precipitation over ocean, ammonium nitrate is present in insignificant amounts.  相似文献   

8.

Purpose

Climate models predict that amplification of the hydrological cycle results in more extreme (more intensive but less frequent) precipitation events (EPEs) that have larger effects on ecosystem functioning than mean precipitation conditions. Semiarid grassland ecosystems are considered important CH4 sinks whose functioning is greatly affected by variations in precipitation patterns. An experiment was performed to assess the effects of extreme precipitation events on the functioning of a fenced semiarid steppe grassland on the Inner Mongolian Plateau of China.

Materials and methods

Extreme precipitation events (282 mm over 20 consecutive days) during the middle (Pm) and late (Ps) growing periods of 2014 were simulated to assess the effects of extreme precipitation events on the CH4 uptake of the ecosystem.

Results and discussion

The extreme precipitation events had no significant effect on the CH4 uptake rate during the growing season but did result in 62 and 45% reductions in the CH4 uptake rate during the Pm and Ps events, respectively. There were legacy effects on suppression of the CH4 uptake rate for approximately 40 and 35 days after the events in the Pm and Ps plots, respectively, but the suppression disappeared rapidly during the late season as a result of faster water loss. No significant differences in cumulative CH4 uptake were detected between the treatment and the control plots over the growing season as a whole, which demonstrates that the ecosystem functions as a CH4 sink. The average CH4 uptake rates were found to be strongly regulated by changes in the soil water content.

Conclusions

The results suggest that the CH4 uptake budget of this fenced steppe grassland can be maintained even in the face of consecutive extreme precipitation events, regardless of the timing of the events. Nevertheless, long-term experiments are needed to detect the thresholds for CH4 uptake budget changes, in case of an increasing occurrence of EPEs in the future.
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9.
The acidity of precipitation in rural, forested areas of the northeastern United States is dominated by the strong mineral acids: H2SO4 and HN03. Weak acids have a negligible effect on the measured acidity (pH) of precipitation. These conclusions are based on total acidity titrations and detailed analysis of organic and inorganic components in precipitation.  相似文献   

10.
Theory and experimental results have shown that neutral salts in the precipitation or supplied to the ground by other means reduce the acidification of soils by acid precipitation. This salt effect is caused by the cation exchange occurring after the entry of the rain water into the soil.The acid components of precipitation consist of H2SO4, HNO3 and HCl and of NH4+ after nitrification in the soil. The magnitude of the salt effect depends on the relative bonding energy of H3O+ and of Ca2+, Mg2+, Na+, K+, NH4+ in the soil as well as on the concentrations of H3O+ and the above cations in the precipitation. The salt effect may be considerable in very acid soils. It decreases with rising pH to become very small or negligible in neutral soils, chiefly due to the increasing bonding energy of H3O+ in this direction.The adverse effect of acid precipitation, therefore, is likely to be less in very acid soils, such as podsols, than in slightly acid and neutral soils with low buffering capacity against pH change. Soil texture and calcite content are very important factors in this respect as fine material and calcite increase the buffering.  相似文献   

11.
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.  相似文献   

12.
Data of the Multistate Atmospheric Power Production Pollution Study (MAP3S) and the National Atmospheric Deposition Program (NADP) were utilized to develop wet deposition spatial distribution patterns for the eastern United States for 1979. The ions of SO4 ?, NO3 ?, H+, and NH4 + were selected for study since they are the most prominent ones found in precipitation. Total wet deposition for 1979 was normalized to one centimeter of precipitation and objectively analyzed using the Synagraphic Mapping System (SYMAP) technique. Gradients of SO4 ? and NO3 ? were found to be essentially uniform, both to the east and west of the major pollution regions. An increased gradient in normalized deposition for SO4 ?, NO3 ?, and H+ was found in the Appalachian Mountain region. Estimates of total wet deposition were obtained by using the normalized deposition values in conjunction with precipitation as reported by the National Climatic Center. SYMAP analyses of the estimated total wet deposition were localized in nature due to precipitation variations between sites.  相似文献   

13.
A large data base on inland lakes in the Upper Great Lakes Region (UGLR) was used to evaluate assumptions and relationships of empirical acidification models. Improved methods to calculate background alkalinity and background SO4 2? are reported; SO4 2? enrichment factors indicate that terrestrial SO4 2? sources and watershed or lake sinks must be considered for site-specific background SO4 2? estimates. Significant relationships were found between lake acidification estimated as change in SO4 2? and precipitation acidity but not between changes in lake alkalinity and precipitation acidity in this lightly impacted region.  相似文献   

14.
Bayesian regularized back-propagation neural network (BRBPNN) was developed for trend analysis, acidity and chemical composition of precipitation in North Carolina using precipitation chemistry data in NADP. This study included two BRBPNN application problems: (i) the relationship between precipitation acidity (pH) and other ions (NH4 +, NO3 ?, SO4 2?, Ca2+, Mg2+, K+, Cl? and Na+) was performed by BRBPNN and the achieved optimal network structure was 8-15-1. Then the relative importance index, obtained through the sum of square weights between each input neuron and the hidden layer of BRBPNN(8-15-1), indicated that the ions' contribution to the acidity declined in the order of NH4 + > SO4 2? > NO3 ?; and (ii) investigations were also carried out using BRBPNN with respect to temporal variation of monthly mean NH4 +, SO4 2? and NO3 ? concentrations and their optimal architectures for the 1990–2003 data were 4-6-1, 4-6-1 and 4-4-1, respectively. All the estimated results of the optimal BRBPNNs showed that the relationship between the acidity and other ions or that between NH4 +, SO4 2?, NO3 ? concentrations with regard to precipitation amount and time variable was obviously nonlinear, since in contrast to multiple linear regression (MLR), BRBPNN was clearly better with less error in prediction and of higher correlation coefficients. Meanwhile, results also exhibited that BRBPNN was of automated regularization parameter selection capability and may ensure the excellent fitting and robustness. Thus, this study laid the foundation for the application of BRBPNN in the analysis of acid precipitation.  相似文献   

15.
Precipitation is currently collected by several methods, including several different designs of collection apparatus. We are investigating these differing methods and designs to determine which gives the most representative sample of precipitation for the analysis of some 25 chemical parameters. The experimental site, located in Ithaca, New York, has 22 collectors of 10 different designs. The designs include bulk (wet and dry deposition collected together), wet only (only rain and snow) and wet/dry (collects wet and dry deposition separately). In every sampling period, which varies from 1 day to 1 mo, depending on the time variable being tested, the following chemical parameters are determined: conductivity, pH, Ca, Mg, Na, K, NH4, N03, Ntotal Si04, PO4, Ptotal, Cl, SO4, DOC, Zn, Cu, Mn, Fe, Al, Ni, Cd, Pb, Ag, DDT, DDE, Dieldrin and PCB's. The results of the investigation lead us to conclude that:
  1. Precipitation samples must exclude dry deposition if accurate information on the chemical content of precipitation is required.
  2. Substantial contamination results when glass and plastic collectors are used to sample precipitation for inorganic and organic components, respectively.
  3. The inorganic components of precipitation samples of low pH (3.5 to 4.5), with the exception of P04 and Cl, exhibited no significant change in concentration when stored at 4\dgC for a period of 8 mo. We believe this is due to the stabilizing influence of a large concentration of H ions.
  4. If quantitative information on the chemical composition is required, precipitation samples should be collected at no longer than weekly intervals if immediate collection is not possible.
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16.
A freshwater wetland at the Experimental Lakes Area in northwestern Ontario stored most of the SO4 2? received annually from precipitation, runoff and experimental additions. The S budget was determined for a small fen spray irrigated with H2SO4 and HNO3. Annual S retention was greatest during the first year of experimental addition of H2SO4 (73% of input in 1983). Retention was lowest (22%) in 1984, a year of lower than average precipitation with a long hot summer. During years with hot, dry summers, SO4 2? was produced from the reoxidation of reduced S compounds in the peat and released to surface waters. The autumn SO4 2? pulse was accompanied by the release of Ca and Mg but was not accompanied by a H+ release as has been detected in eastern Ontario and southern Norway, areas which receive more acidic precipitation.  相似文献   

17.
It is proposed that the value of ([SO4 ??] - [Ca++ + Mg++]) in precipitation is a suitable way to describe the acidifying potential (AP) of the wet desposition. In eastern North America, the AP of precipitation varies from 20 to 85% of the total sulphate, the remainder of the sulphate being neutralized H2SO4, sulphate from salts in dust or from sea salt. The AP ranges from 20 to 80% of the H+ in the wet deposition. The rest of the H+ is contributed by the net effect of N compounds. Ammonium and nitrate ions from ammonia and NOXemissions do not represent a net acidic loading to the terrestrial ecosystem if they are taken up by vegetation. However, when N leaches from watersheds in the form nitrate, it constitutes an acidifying demand on the ecosystem. Therefore, the overall net acidifying potential (NAP) applied to the terrestrial ecosystem is defined by the value of ([SO4 ??] - [Ca++ + Mg++]) in precipitation plus [NO3 ??] in runoff from the watershed.  相似文献   

18.
The total deposition of sulphur (S) and nitrogen (N) components in Norway during the period 1988–1992 has been estimated on the basis of measurement data of air- and precipitation chemistry from the national monitoring network. There are large regional variations in depositions with highest values in the southwestern part of Norway. Time series analysis of annual mean concentrations of sulphur dioxide (SO2) and sulphate (SO4 ––) in air, non marine SO4 ––, nitrate (NO3 –) and ammonium (NH4 +) in precipitation, shows a significant reduction in the S concentrations both in air and precipitation. In precipitation the concentrations are reduced by 30–45 percent in Southern Norway and 45–55 percent in Central and Northern Norway. Even larger reductions are observed in air concentrations with 50–65 percent reduction in Southern Norway and 65–88 percent reduction further north. For N components there are generally no significant trends in concentration levels nor in precipitation or air. The observed trends are comparable with reported trends in emission.  相似文献   

19.
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.  相似文献   

20.
Regulatory measures in the United States, such as Title IV of the Clean Air Act Amendments of 1990, have primarily restricted sulfur dioxide emissions as a way to control acidic deposition. These restrictions, coupled with increasing concentrations of NH4 + in wet deposition in some regions of the U.S. and continued high emissions of nitrogen oxides have generated a significant shift in the chemistry of precipitation as measured at National Atmospheric Deposition Program/National Trends Network sites. Trends in precipitation chemistry at NADP/NTN sites were evaluated for statistical significance for the period 1981–1998 using a Seasonal Mann-Kendall Test, a robust non-parametric test for detection of monotonic trends. SO4 2? declines were detected at 100 of the 147 sites examined while no sites exhibited increasing SO4 2? trends. On average, SO4 2? declined 35% over the period 1981–1998 with downward SO4 2? trends being most pronounced in the north-eastern United States. In contrast, no consistent trends in NO3 ? concentrations were observed in precipitation in any major region of the United States. Although the majority of sites did not exhibit significant trends in NH4 + concentration, 30 sites exhibited upward trends. For Ca2+ concentration in precipitation, 64 sites exhibited a significant decreasing trend and no sites exhibited an upward trend.  相似文献   

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