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1.
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 SO2, HNO3, NO2 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: SO2, 25%; HNO3, 32%; NO2, 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   

2.
Atmospheric gases and particulates were collected using four-stage filter-pack in Chunchon from January through December in 1999. Particulate SO4 2? and NO3 ?, and gaseous HNO3, SO2 and NH3 were analyzed. Annual average concentration of SO4 2?(S), NO3 ?(S), HNO3 (g), SO2(g) and NH3(g) were 5.75µg/m3, 4.98µg/m3, 0.33ppb, 1.52ppb and 7.25ppb, respectively. Annual dry deposition fluxes were estimated using the measured concentration and dry deposition velocity published by other research group. Annual dry deposition of S was 287kg · (km)?2·y?1, which accounted for about 30% of total S deposition. For N deposition, dry deposition is predominant; about 70% of total N deposition was through dry process mostly as forms of NH3 and HNO3.  相似文献   

3.
Xu  R. K.  Ji  G. L. 《Water, air, and soil pollution》2001,129(1-4):33-43
The difference in effect on acidification and species of aluminum speciation between HNO3 and H2SO4for two contrasting types of soils in surface charge was investigated. The results show that the effect of H2SO4 on acidification of variable charge soils (Ferric Acrisol and Haplic Acrisol) of subtropical regions wasweaker than that of HNO3, due to the specific adsorption of SO4 2- and the accompanied release of OH-. For two constant charge soils, Haplic Luvisol andEutric Cambisol, the difference in effect between the two acids is small. The concentrations of total inorganic monomeric aluminum, Al3+, Al-F complexes and Al-SO4complexes in the extract from variable charge soils are alsolower in H2SO4 systems than those in HNO3 systems, whereas the reverse is true for constant charge soils, except the concentration of Al3+. For variable charge soils, Al-F complexes are the major species of inorganic monomeric aluminum at high pH butAl3+ might contribute to a largepart at low pH, while for constant charge soils Al-F complexes contribute almost exclusively to the inorganic monomeric aluminum. The presence of a large amount of SO4 2- in the extract from the constant charge soilsleads to a higher proportion of Al-SO4 complexes in totalinorganic monomeric aluminum than that from variable charge soil, although the numerical value of proportion is small.  相似文献   

4.
《Soil biology & biochemistry》2001,33(12-13):1695-1702
Sieved soil and soil core experiments were performed to determine the potential sensitivity of forest soil CH4 oxidation to oxidised N, reduced N and oxidised S atmospheric deposition. Ammonium sulphate was used to simulate reduced N deposition, HNO3 oxidised N deposition and H2SO4 oxidised S deposition. The effects of NH4+, NO3−, SO42− and H+ on soil CH4 flux were shown to be governed by the associated counter-anion or cation of the investigated ions. Ammonium sulphate, at concentrations greater than those that would be experienced in polluted throughfall, showed a low potential to cause inhibition of CH4 oxidation. In contrast, HNO3 strongly inhibited net CH4 oxidation in sieved soils and also in soil cores. In addition, soil CO2 production was inhibited and the organic and mineral soil horizons acidified in HNO3 treated soil cores. This suggested that the HNO3 effect on CH4 flux might be indirectly mediated through aluminium toxicity. Sulphuric acid only inhibited CH4 oxidation when added at pH 1. At concentrations more representative of heavily polluted throughfall, H2SO4 had no effect on soil CH4 flux or CO2 production from soil cores, even after 210 days of repeated addition. In contrast to HNO3 additions, acidification of the soil was not marked and was only significant for the mineral soil. The findings suggest that the response of forest soil CH4 oxidation to atmospheric acid deposition is strongly dependent on the form of acid deposition.  相似文献   

5.
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 H2SO4 and HNO3 (1.9:1 by weight). In 1989 the treatments were modified as follows. In subarea 1 the treatments continued unchanged (H2SO4+HNO3 in rain to pH 4 and pH 3), but in subarea 2 only H2SO4 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 H2SO4+HNO3 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 H2SO4+HNO3 in subareas 1 and 2 did not affect the results.  相似文献   

6.
A physico-chemical sub-cloud rain acidification model is used to simulate the acidification processes of rainwater in ten cities of China, based on the observation data of the chemical components of cloud- and rainwater and the concentrations of gaseous and aerosol species. The results show that there are in-cloud process and below-cloud process in the formation of acid rain, but the relative importance of these two processes is different in various cities. The acidification of rainwater under cloud is very important in Guiyang, Shanghai, Jilin, Beijing, Changsha and Chongqing, and the in-cloud and below-cloud process contribute equally to the acidification in Guilin, however, the acidification of rainwater in cloud is more important in Nanchang and Guangzhou. Overall, the aerosol has an alkalization effect on the rain, about 11%–25% of H+ concentration in the rainwater is neutralized over Southern China and 60%–70% is neutralied over Northern China by aerosol species. The effect of atmospheric SO2 on acidification of rainwater is nonlinear and is different in various regions. The effects of the variation of atmospheric NH3, H2O2 and aerosol species on pH of rainwater are also discussed in detail.  相似文献   

7.
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   

8.
Growing cloud droplets absorb such atmospheric gaseous pollutant as SO2(g), condensing atmospheric water vapor into themselves. Then, the cloud droplets are acidified by absorption of SO2(g) during condensational growth on cloud condensation nuclei (CCN). Characteristics of this process, which is a part of rainout, have not been made clear yet. In order to estimate the contribution of rainout to acid rain formation, the acidification of growing cloud droplets is investigated numerically, using a mathematical model. The numerical simulations show that: (1) the time to attain the equilibrium state for mass transfer (acidity and growth) and heat transfer (temperature) is much longer than the time for disappearance of CCN; (2) time variation of acidity and temperature of cloud droplets are greatly dependent on the existence of undissolved CCN; and (3) there seems to be a close correlation between the time variation of the acidity and that of the temperature.  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+, NH4 +, Ca2+, and SO4 2?, i.e., 400, 351, 299, and 876 eq/ha/yr, respectively. The outputs of H+, NH4 +, and SO4 2? from the watershed were very low, while those of Ca2+ and Mg2+ were high, 712 and 960 eq/ha/yr, respectively. The element budgets suggested that i) the net retentions of H+, NH4 +, and SO4 2? in this watershed were high, and ii) the net release of Mg2+ from this watershed was high mainly due to weathering. The net release of Ca2+ was not so high because of the high atmospheric deposition, while atmospheric deposition of Mg2+ 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 Mg2+. Moreover, the net retention of SO4 2? also contributed to soil acidification.  相似文献   

10.
The rates of nucleation of liquid aerosols from the gaseous mixtures H2SO4 + H2O and HNO3 + H2O 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 H2SO4 + H2O than for HNO3 + H2O. This is due to the much larger free energy of mixing in the liquid phase for H2SO4 + H2O. Conversion from activities to actual pressures leads to concentrations of HNO3 which are much too high to be found under normal atmospheric conditions. On the other hand, the concentrations of H2SO4 vapor needed to nucleate droplets in the H2SO4 + H2O system are in the range 4(10?5) to 1.3 (10?2) ppm, a concentration which can result from photo-oxidation of SO2 in the atmosphere. Calculations are made of the growth curves for H2SO4 + H2O 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   

11.
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%), NH4 + (12%), Ca2+ (58%), Mg2+(43%), NO3 ? (55%), Cl? (27%) and SO4 ?2 (26%)]. Dry input of base cations was dominated by coarse particles, whereas gaseous inputs were more important for S and NO3 ?. Atmospheric concentrations of SO2 and inputs of SO4 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 SO4 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   

12.
酸和氧化还原剂对二氧化锰溶解度的影响   总被引：1，自引：1，他引：1       下载免费PDF全文
涂仕华 《土壤学报》2004,41(4):530-535
由于土壤中锰的有效性随pH和Eh的变化而变化,利用土壤测试方法得到的锰素营养丰缺指标,通常难以代表田间锰素营养的实际状况.然而,在应用土壤pH和氧化锰溶解度的关系时,某些文献的不确切解释,引起一些误解.本实验研究了在浓HCl、HNO3和H2SO4及其稀溶液的不同浓度情况下对二氧化锰-水钠锰矿(MnO2)的溶解能力和机理,以及三种卤素还原剂(KCl、KBr和KI)在两种pH值条件下对MnO2的还原能力,从实验上和理论上进一步阐明了pH和Eh对MnO2溶解度的影响.实验结果表明,在浓HCl中,MnO2能被Cl-迅速还原而溶解.而在浓HNO3和H2SO4溶液中,MnO2不能被酸所直接溶解,只能被酸中的H2O缓慢还原,放置两年后反应仍未到达终点.在稀酸溶液中,当H+强度小于0.5 mol L-1(pH＞1.0)时,三种强酸对MnO2都无明显的溶解能力;当H+强度＞1.0 mol L-1时,HCl对MnO2的溶解能力显著地高于HNO3和H2SO4.三种卤盐溶液对MnO2的还原能力为KI＞KBr＞KCl,并随pH的降低和浓度的升高而增强.当pH＞3时,KCl对MnO2的还原能力极弱;而无论pH高低(pH3或pH5),KI在很低浓度(0.001 mol L-1)时都能有效地还原MnO2.上述结果说明,如果二氧化锰不被还原,仅改变pH则很难被溶解.然而,在较高pH条件下,如有强还原剂存在,也有相当量的MnO2被还原.低Eh和pH条件下最有利于MnO2的还原.  相似文献   

13.
Gas and aerosol measurements were performed at 3 ground based measuring sites at Mt. Rigi in central Switzerland during 2 winter seasons. Both NH3 and NH4 + show a strong vertical concentration gradient between the top station (1620 masl) and the bottom station (430 masl). High concentrations of NH3 with values up to 29 ppbv, were found at the bottom station. HNO3 concentrations were usually below 1 ppbv, with lower values at the bottom station than at the top station that presumably reflect particulate NH4NO3 formation due to high NH3 concentrations at the lower site. No vertical concentration gradient was found for SO2. Simple models have been used to estimate below-cloud scavenging of gaseous NH3 and particulate NH4 + by rain between two sites with a vertical separation of 600 m. The calculations used measurements from three case studies. Below-cloud scavenging of NH3 by rain was found to be more important than below-cloud NH4 + scavenging. From 58 to 88 % of the increase of [NH4 +] in precipitation between the two sampling sites was calculated to result from gas scavenging. Both observations and scavenging calculations were in relatively good agreement for three events. Observations from the present study and tests using different aerosol and raindrop diameters in the calculations point to the importance of using real data in below-cloud scavenging studies considering the relative importance of aerosol and gas scavenging.  相似文献   

14.
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, Na2SO4, MgCl2, MgSO4, HCl, and H2SO4 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/(Al3+ + AlOH2+ + 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/(Al3+ + AlOH2+ + Al(OH)2+) ratios, the salt effect seems to be more important for the subsoils. Addition of S042? salts and H2SO4 induced higher pH and lower Al concentrations than the corresponding Cl? treatments due to the SO42? sorption, especially in the subsoils. The Ca/(Al3+ + AlOH2+ + Al(OH)2+) ratios were higher than those of the corresponding Cl? treatments. In subsoils even after H2SO4 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 HNO3 due to the precipitation load may induce an even more acidic soil solution than the inputs of H2SO4 of the last decade.  相似文献   

15.
It is known from the literature that the reaction 2 NO2(aq) + Cl-(aq) → NO3-(aq) + ClNO(g) takes place in the presence of NO2 and sea salt aerosol. This work indicates that the reaction is first order in Cl- and second order in NO2(aq) and the rate coefficient was determined to be 8.9 ± 2.1) × 1010 M-2 s-1 at 293 K. The study shows that the formation rate of nitrate in liquid sea salt aerosol is not influenced by pH in the range between 5.1 and 7.5. The uptake of ammonia in liquid sea salt particles in the present experimental system is governed by the rate of the reaction CO2(aq) + H2O → H2CO3. The addition of NH3 to NO2 and dry sea salt particles does not change the extent of nitrate formation in the particles. The dry aerosol shows an unexpected content of ammonium which increases with decreasing relative humidity. The nitrate formation in frozen sea salt particles at 266 K exposed to only NO2, is about 5 times lower than for the corresponding droplets at 293 K.  相似文献   

16.
A method for the collection of soil solution and the determination of pH, H2CO3* (= CO2(aq) plus H2CO3°), HCO3? and CO32?, was developed which excluded atmospheric gases during the entire procedure. The soil solution was collected by tension lysimeters without exposure to the atmosphere. Using a closed system, the sample was transferred to a titration beaker for the analysis of pH, H2CO3* and HCO3?. The analysis of CO2-acidity was done by titration with 0.0454 N Na2CO3 to the end point pH of 8.3. It was immediately followed by an acidimetric titration for the determination of alkalinity using 0.005 N H2SO4 under gentle N2 flow; the equivalence point was determined graphically from the titration curve. In standard solutions, this method gave nearly 100% recovery of H2CO3* and HCO3?. In soil solutions, the pH markedly increased and H2CO3* decreased upon exposure to the atmosphere. The values of the sum of CO2-acidity and alkalinity in soil solutions at a depth > 5 cm agreed well with the values of total inorganic carbon obtained by CO2 infrared detection following CO2 degassing. For solutions obtained from 100 cm and 300 cm depth (limestone) the measured distribution of H2CO3* and HCO3? was in agreement with the calculated values based on pH-measurement and total inorganic carbon. This comparison was unsatisfactory for the concentration of H2CO3* in solutions of the surface (0–15 cm) soil, possibly because the mathematical model as well as the interpretation of the titration curves did not consider any organic compounds in the solution.  相似文献   

17.
The Laflamme Lake Watershed Area is located in a sensitive region on the Canadian Shield and is subjected to wet atmospheric loading between 17 and 25 kg ha?1 yr?1. From 1981 to 1988, the level and fluctuations of the atmospheric deposition of acidifying substances has led to various responses in the water chemistry of headwater lakes in the area. The general trend in atmospheric inputs is a gradual increase of acidifying substances from 1981 to 1985 followed by a 2 yr decrease then a return to previous values. In the two lakes with almost no alkalinity acidification has occured throughout the 1983 to 1988 period. In the four lakes with slightly higher alkalinity values, a reversal in acidification is seen when atmospheric loading decreased in 1986. Along with the interannual trends, seasonal variability to acidification occurs with sensitivity of surface waters being highest during spring melt. Sensitivity to acidification can also be altered by watershed processes and in the Laflamme Lake Watershed, soil processes are effective in altering the acidity of precipitation before it reached the lake. In this watershed, wet atmospheric inputs of H+ and NO3 ? are larger than surface water outputs while the reverse occurs for Ca2+, Mg2+, Na+, K+, Cl? and SO4 2?.  相似文献   

18.
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.  相似文献   

19.
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.  相似文献   

20.
The oxidation of di-(2-ethylhexyl) phthalate (DEHP) in solution using UV/H2O2 and direct UV photolysis are analyzed in this study. It was found that DEHP was 100% removal in the solution by 180-min UV/H2O2 treatment and 73.5% removal by 180-min direct UV photolysis. The effect of different factors, such as DEHP concentration, H2O2 concentration, and UV light intensity, on photochemical degradation was investigated. The degradation mechanism of DEHP and the acute toxicity of intermediates were also studied. The photochemical degradation process was found to follow pseudo-first-order kinetics. The results of our study suggested that the concentration with 40 mg/L H2O2 and 5 μg/mL DEHP in the solution at pH 7 with 10.0?×?10?6 Einstein l?1?s?1 UV was the optimal condition for the photochemical degradation of DEHP. The photochemical degradation with UV/H2O2 can be an efficient method to remove DEHP in wastewater.  相似文献   

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