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1.
Sulfur dioxide (SO 2), prevalent in the modern urban environment of industrial countries, attacks calcite (CaCO 3)in marble. As a result, a gypsum (CaSO 4·2H 2O) crust is produced at rain-sheltered surfaces while areas exposed to rain experience accelerated erosion. We have investigated theeffect of certain surfactants as protective agents against SO 2 attack. We report that the anions oxalate (C 2O 4 -2) and oleate (C 17H 33COO -) from solutions of their highly soluble alkali salt species areable to replace carbonate (CO 3 -2) in calcite producingless reactive substrate of oxalate and oleate of calcium. Experiments to measure the protection obtained by these treatments were carried out in the laboratory and field conditions at nearly 1ppm and 10 ppb SO 2 concentrations, respectively. We found that these treatments provided significantprotection to marble exposed in sheltered areas, up to 30% reduction of reaction rate by treatment with 2 × 10 -4M sodium oleate and up to 14% by a 2 × 10 -3 M with potassium oxalate solutions, but become ineffective over long term exposure when applied to surfaces exposed to rain.Carrara marble was used in the reported study. Ion chromatographywas the analytical tool, which allowed precise measurements of ionic concentrations of these salts, the amount of their uptakeby marble, and the thickness of the gypsum crust. X-ray diffraction allowed determination of the new minerals formed at the marble surface by the treatment with surfactants. 相似文献
2.
Cr 3+ sorption on strong acid exchanger Amberlyst-15(H +) is studied as a function of time and temperature using CrCl 3.6H 2O and [Cr 4(SO 4) 5(OH) 2] solutions. The rate is found to be governed by a mixed diffusion for both the solutions and faster for Cl 1? solution than SO 4 2?. The exchange capacities are found to be higher for Cl 1? system than SO 4 2?. From the rate constant values, the energies of activation are calculated using the well-known Arrhenius equation. Equilibrium data is explained with the help of the Langmuir equation. The Langmuir parameters are also found to be higher for exchange from the chloride solutions. Various thermodynamic parameters (??H o, ??S o, and ??G o) for Cr 3+ exchange on the resin are calculated. The ??G o values are found to be negative while ??H o and ??S o are positive for both the Cr 3+/Cl 1? and Cr 3+/SO 4 2? systems. It is suggested that in case of Cl 1? solutions, the metal is exchanged as Cr 3+, while in case of SO 4 2? solutions, the metal exchanging specie is CrSO 4 +. 相似文献
4.
The major part of Venezuela oil production is located in and around the Lake Maracaibo Basin. The samples were collected over a 1-year period at Catatumbo and La Esperanza sites. The rainwater was acidic, with a VWA-pH of 4.6 for Catatumbo and 4.2 for La Esperanza. This acidity is made up in 93% by inorganic acids (mainly H 2SO 4), and NH 4
+ is the major cation which buffer the acidity of precipitation. An excess of sulfate (SO 2
*) > 96% was obtained in both sites. Correlation analysis shows that H + is strongly correlated with SO 4
x. Anthropogenic air pollution from oil fields (H 2S) and the burning of sulphur-bearing fuels (SO 2) are probably the dominant sources; however, the lack of correlation between the H + and NO 3
– levels would appear to indicate that the SO 4
* is also of biogenic origin (H 2S-DMS from Sinamaica Lagoon-Lake Maracaibo- and the Caribbean). Statistical analysis of the pooled data indicated that the concentration differences between Catatumbo and La Esperanza sites are not significant at 99% confidence level. 相似文献
5.
In order to investigate the acid rain formation under the coexistence of SO2(g), H2O2(g), and HNO3(g) in the air, a mathematical model has been built and some numerical simulations have been carried out with use of the model. The simulation reveals that SO2(g) absorbed into a raindrop is released and then re-absorbed as the fall distance increases. The desorption and re-absorption processes of SO2(g) are caused by: (1) the fact that the equilibrium concentration of H2O2(aq) and HNO3(aq) in raindrops are much higher than that of SO2(aq), and (2) the fact that the oxidation reaction rate of HSO3
? with H2O2(aq) increases with H+ concentration in raindrops. The degree of acidification of the rainwater has been estimated by introducing a raindrop size distribution. The acidification is mainly caused by the adsorption of SO2(g) in the usual case where the atmospheric concentration of SO2(g) is much higher than that of HNO3(g). With the increase in the atmospheric concentration of HNO3(g), the concentration of H+ generated from SO2(g) decreases and the contribution of HNO3(g) to the generation of H+ becomes dominant. 相似文献
6.
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 SO 2, NO 2, and O 3 in the ambient atmosphere; and high, strongly correlated, SO 4 = and NO 3 ? 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. 相似文献
7.
Rain water at two forested sites in Guangzhou (south China) show high concentrations of SO 4 2?, NO 3 ? and Ca 2+ 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 Al 3+ concentrations in soil solutions. The variation in elemental concentration in soil solution was related to nitrification (H +, NH 4 + and NO 3 ?) and cation exchange reaction (H +, Al 3+) in soil. The negative effect of soil acidification is partly dampened by substantial deposition of base cations (Ca 2+, Mg 2+ and K +) in this area. 相似文献
8.
One-year field measurements were conducted in a Japanese cedar ( Cryptomeria japonica) forest, located in Gunma Prefecture, Japan. On the basis of the meteorological and atmospheric concentration data, the dry deposition of SO 2, HNO 3, NO 2 and HCl was estimated using the inferential method. The annual dry deposition of H + was estimated at 721 eq ha ?1yr ?1, which was 40% larger than the measured annual wet deposition of H + (514 eq ha ?1yr ?1). Therefore, dry deposition is an important pathway for the atmospheric input of H + to the forest in the study site. The contribution of each gas to the dry deposition of H + was as follows: SO 2, 25%; HNO 3, 32%; NO 2, 10%; and HCl, 33%. The extremely high contribution of HCl appeared to be caused by the high emission intensity of HCl due to waste incineration in the site region. The differences between estimated deposition and throughfall and stemflow measurements indicated that about 80% of the total deposition of H + was taken up by the canopy. 相似文献
9.
We evaluated the element budgets in a forested watershed in Jiulianshan, southern China. The element input in bulk precipitation was characterized by high depositions of H +, NH 4 +, Ca 2+, and SO 4 2?, i.e., 400, 351, 299, and 876 eq/ha/yr, respectively. The outputs of H +, NH 4 +, and SO 4 2? from the watershed were very low, while those of Ca 2+ and Mg 2+ were high, 712 and 960 eq/ha/yr, respectively. The element budgets suggested that i) the net retentions of H +, NH 4 +, and SO 4 2? in this watershed were high, and ii) the net release of Mg 2+ from this watershed was high mainly due to weathering. The net release of Ca 2+ was not so high because of the high atmospheric deposition, while atmospheric deposition of Mg 2+ was not so high (130 eq/ha/yr). Decrease of acid neutralizing capacity in the soil, i.e., net soil acidification, was caused mainly by the net release of Mg 2+. Moreover, the net retention of SO 4 2? also contributed to soil acidification. 相似文献
10.
Ion mass and H + budgets were calculated for three pristine forested catchments using bulk deposition, throughfall and runoff data. The catchments have different soil and forest type characteristics. A forest canopy filtering factor for each catchment was estimated for base cations, H +, Cl ? and SO 4 2? by taking into account the specific filtering abilities of different stands based on the throughfall quality and the distribution of forest types. Output fluxes from the catchments were calculated from the quality and quantity of the runoff water. Deposition, weathering, ion exchange, retention and biological accumulation processes were taken into account to calculate catchment H + budgets, and the ratio between external (anthropogenic) and internal H + sources. In general, output exceeded input for Na +, K +, Ca 2+, Mg 2+, HCO 3 ? (if present) and A ? (organic anions), whereas retention was observed in the case of H +, NH 4 + , NO 3 ? and SO 4 2? . The range in the annual input of H + was 22.8–26.3 meq m ?2 yr ?1, and in the annual output, 0.3–3.9 meq m ?2 yr ?1. Compared with some forested sites located in high acid deposition areas in southern Scandinavia, Scotland and Canada, the catchments receive rather moderate loads of acidic deposition. The consumption of H + was dominated by base cation exchange plus weathering reactions (41–79 %), and by the retention of SO 4 2? (17–49 %). The maximum net retention of SO 4 2? was 87% in the HietajÄrvi 2 catchment, having the highest proportion of peatlands. Nitrogen transformations played a rather minor role in the H + budgets. The ratio between external and internal H + sources (excluding net base cation uptake by forests) varied between 0.74 and 2.62, depending on catchment characteristics and acidic deposition loads. The impact of the acidic deposition was most evident for the southern Valkeakotinen catchment, where the anthropogenic acidification has been documented also by palaeolimnological methods. 相似文献
11.
The rates of nucleation of liquid aerosols from the gaseous mixtures H 2SO 4 + H 2O and HNO 3 + H 2O at 25°C for various relative humidities (10 to 100%) and various activities of acid vapor are calculated using the Flood-Neumann-Döring-Reiss-Doyle theory of binary homogeneous nucleation. The activities of acid vapor needed for nucleation are 25 to 300 times smaller for H 2SO 4 + H 2O than for HNO 3 + H 2O. This is due to the much larger free energy of mixing in the liquid phase for H 2SO 4 + H 2O. Conversion from activities to actual pressures leads to concentrations of HNO 3 which are much too high to be found under normal atmospheric conditions. On the other hand, the concentrations of H 2SO 4 vapor needed to nucleate droplets in the H 2SO 4 + H 2O system are in the range 4(10 ?5) to 1.3 (10 ?2) ppm, a concentration which can result from photo-oxidation of SO 2 in the atmosphere. Calculations are made of the growth curves for H 2SO 4 + H 2O droplets (radius vs composition) at various relative humidities from the critical size radius up to a 1000 Å radius, corresponding to nuclei large enough to serve as condensation centers for heterogeneous nucleation. The limitations of binary homogeneous nucleation theory at extremely low concentrations of one of the components are discussed and it is shown that this theory becomes inapplicable if the actual vapor pressure of one component is below 10 ?6 torr. 相似文献
12.
Elution of Cl ?, SO 4 2?, NO 3 ?, and H + often occurred in that order at a site in the central Sierra Nevada, California, that receives an annual average of 1000 cm of snowfall which is low in acidic components. During eight winter periods of above-base level snowpack outflow, and one spring melt period, on the average 25% of the ions were discharged at the following percentages of outflow volumes: Cl ? at 11%, NO 3 ? at 13%, SO 4 2? at 18%, and H + at 20%. Seven of eight winter outflows were associated with low ionic strength rainfall onto the snowpack. Mean solute concentrations during the first 25% and first 50% of the total outflow were significantly greater than during the last 75% and last 50% of the total outflow for Cl ?, NO 3 ?, and SO 4 2?, but not for H +. Maximum solute concentrations were up to 2.9 times the overall event volume-weighted mean concentrations for Cl ?, 3.7 times for NO 3 ?, 3.0 times for SO 4 2?, and 2.9 times for H +. 相似文献
13.
The potential for sulfate retention is an important soil feature for buffering of atmospheric acid deposition. We studied the effects of increasing additions of different neutral salts and acids on mobilization and retention of SO 4 2- in acid forest soils. Soils containing up to 11 mmol SO 4 2- kg -1 were equilibrated with H 2O, NaCl, MgCl 2, and HCl. Release of SO 4 2- was highest with H 2O and NaCl additions and lowest when HCl was used. Increasing the ionic strength of the added solutions caused decreasing SO 4 2- concentrations in equilibrium solution. Decreasing pH in equilibrium solution was found to be the reason for the decrease in release. Even when the pH was < 4, the SO 4 2- release decreased. We assume that this finding resulted from the fact that in the soils studied the SO 4 2- sorption was controlled by the high contents of Fe oxides/hydroxides. Experiments with Na 2SO 4, MgSO 4, and H 2SO 4 demonstrated that the B horizons already containing high amounts of SO 4 2- were still able to retain SO 4 2-. Sulfate retention increased in the order Na 2SO 4 < MgSO 4 < H 2SO 4, which corresponds to increasing H + availability. The higher SO 4 2- retention along with MgSO 4 compared to Na 2SO 4 may be caused by higher potential of Mg to mobilize soil acidity compared to Na. 相似文献
14.
A freshwater wetland at the Experimental Lakes Area in northwestern Ontario stored most of the SO 4 2? received annually from precipitation, runoff and experimental additions. The S budget was determined for a small fen spray irrigated with H 2SO 4 and HNO 3. Annual S retention was greatest during the first year of experimental addition of H 2SO 4 (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, SO 4 2? was produced from the reoxidation of reduced S compounds in the peat and released to surface waters. The autumn SO 4 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
15.
The acidity of the podzolic soils in coniferous forests on the northern tree line (Kola Peninsula) subjected to severe sulphur pollution is considered. The pH values of precipitation were positively correlated with the distance from the pollution point source. There was also a correlation between base saturation of the organic horizon and distance. The long-term SO 2-emissions have resulted in the higher leachability of base cations and dissolution of fulvic acids in the humus horizon. In polluted areas the flux of H + from the organic layer could be stronger owing to higher proportion of hydrolysable humus compounds. Inputs of H + from the atmosphere and humus horizon have resulted in the higher concentrations of the exchangeable aluminium in the illuvial horizon. 相似文献
16.
Humus chemistry and respiration rate, ATP, ergosterol, and muramic acid concentration as measures of chemical properties, microbial activity, biomass, and indicators of fungal and bacterial biomass were studied in a long-term acid rain experiment in the far north of Finnish Lapland. The treatments used in this study were dry control, irrigated control (spring water, pH 6), and two levels of simulated acid rain (pH 4 and pH 3). Originally (1985–1988), simulated acid rain was prepared by adding both H 2SO 4 and HNO 3 (1.9:1 by weight). In 1989 the treatments were modified as follows. In subarea 1 the treatments continued unchanged (H 2SO 4+HNO 3 in rain to pH 4 and pH 3), but in subarea 2 only H 2SO 4 was applied. The plots were sampled in 1992. The acid application affected humus chemistry by lowering the pH, cation exchange capacity, and base saturation (due to a decrease in Ca and Mg) in the treatment with H 2SO 4+HNO 3 to pH 4 (total proton load over 8 years 2.92 kmol ha -1), whereas the microbial variables were not affected at this proton load, and only the respiration rate decreased by 20% in the strongest simulated acid rain treatment (total proton load 14.9 kmol ha -1). The different ratios of H 2SO 4+HNO 3 in subareas 1 and 2 did not affect the results. 相似文献
17.
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 +, Mg 2+, NH 4 +, Ca 2+, Cl ?, NO 3 ? and SO 4 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 ?, SO 4 2? and NO 3 ? in anion were shown to be 54%, 32%, and 14%, respectively and those of Na + and NH 4 + in cation were 32% and 25%. The ratios of Cl ? and Mg 2+ to Na + in precipitation were similar to those of seawater, which imply that great amount of Cl ? and Mg 2+ in precipitation could be originated from seawater. The concentration of H + is little related with SO 4 2?, NO 3 ? and Cl ? ions, whereas nss ?SO 4 2? and NO 3 ? are highly correlated with NH 4 +, which could suggest that great amount of SO 4 2? and NO 3 ? exist in the form of ammonium associated salt. The annual wet deposition amounts (g m ?2year ?1) of SO 4 2?, NO 3 ?, Cl ?, H +, NH 4 +, Na +, K +, Ca 2+ and Mg 2+ 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. 相似文献
18.
Inputs of wet and dry deposition were monitored at the Huntington Forest in the Adirondack Mountains of New York for two years in the open and beneath the canopy of a northern hardwood forest. In the open, ion flux estimates were similar using wet-only weekly (NADP protocol) and event collections, but bulk collections were higher for all ions except H +, which was much lower. These differences were due to the contribution of dry deposition and possible biotic alterations in bulk collectors. Dry deposition was estimated using air concentrations and ion-specific depositional velocities modeled with meteorological data, and contributed substantially to the input of all ions [H + (45%), Na + (24%), K + (22%), NH 4 + (12%), Ca 2+ (58%), Mg 2+(43%), NO 3 ? (55%), Cl ? (27%) and SO 4 ?2 (26%)]. Dry input of base cations was dominated by coarse particles, whereas gaseous inputs were more important for S and NO 3 ?. Atmospheric concentrations of SO 2 and inputs of SO 4 2? and H + were lower at this site than sites closer to point sources of S gas emission. The importance of estimating atmospheric inputs was examined using examples of elemental budgets. For example, different estimates of the contribution of dry deposition of SO 4 2? (9–21 meq m ?2 y ?1) resulted in conclusions ranging from no net retention to a net loss of this element. Such differences have important implications in assessing the current and future role of atmospheric inputs in affecting elemental cycling. 相似文献
19.
The study aimed at evaluating whether salt-induced mobilization of acidity may be modified by the type of anion. For this purpose, the effects of different neutral salts on the solution composition of acid soils were investigated. The results were compared with those of the addition of acids. Two topsoil (E and A) and two subsoil horizons (Bs and Bw) were treated with NaCl, Na 2SO 4, MgCl 2, MgSO 4, HCl, and H 2SO 4 at concentrations ranging from 0 to 10 mmol dm ?3. With increasing inputs of Cl ? the pH of the equilibrium soil solution dropped, the concentrations of Al and Ca increased, and the molar Ca/(Al 3+ + AlOH 2+ + Al(OH) 2+) ratios decreased. These effects were the least pronounced when NaCl was added and the most at the HCl treatments. According to the release of acidity, the topsoils were more sensitive for salt-induced soil solution acidification whereas on base of the molar Ca/(Al 3+ + AlOH 2+ + Al(OH) 2+) ratios, the salt effect seems to be more important for the subsoils. Addition of S0 42? salts and H 2SO 4 induced higher pH and lower Al concentrations than the corresponding Cl ? treatments due to the SO 42? sorption, especially in the subsoils. The Ca/(Al 3+ + AlOH 2+ + Al(OH) 2+) ratios were higher than those of the corresponding Cl ? treatments. In subsoils even after H 2SO 4 additions these ratios were not higher than those of the NaCl treatments. The results indicate (I) that speculation about the effects of episodic salt concentrations enhancement on soil solution acidification not only need to consider the ionic strength and the cation type but also the anion type, (II) that salt-induced soil solution composition may be more crucial in subsoils than in topsoils, and (III) that in acid soils ongoing input of HNO 3 due to the precipitation load may induce an even more acidic soil solution than the inputs of H 2SO 4 of the last decade. 相似文献
20.
The leaching of Ca, Mg, and K from canopies is a major pathway of these cations into forest soils. Our aim was to quantify rates of canopy leaching and to identify driving factors at the regional scale using annual fluxes of bulk precipitation and throughfall from 37 coniferous and deciduous forests of North and Central Europe. Total deposition of Ca, Mg, K, and H + was estimated with Na as an index cation. The median canopy leaching increased in the order: Mg (0.11 kmol c ha –1 a –1) < Ca (0.31 kmol c ha –1 a –1) < K (0.39 kmol c ha –1 a –1). Canopy leaching of Ca and K was positively correlated with the calculated total H + deposition and H + buffered in the canopy, whereas canopy leaching of Mg was not. With contrasting effects, fluxes of SO 4‐S and NH 4‐N in throughfall explained to 64 % ( P<0.001) of the Ca canopy leaching. Fluxes of NH 4‐N and Ca were negatively correlated, suggesting that buffering of H + by NH 3 deposition reduced canopy leaching of Ca. Amount of bulk precipitation and SO 4‐S in throughfall were identified as much weaker driving factors for canopy leaching of K (r 2=0.28, P<0.01). Our results show that Ca is the dominant cation in buffering the H + input in the canopy. At the regional and annual scale, canopy leaching of Mg appears to be unaffected by H + deposition and H + buffering in the canopy. 相似文献
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