Lysimeter study with a cambic arenosol exposed to artificial acid rain: II. Input-output budgets and soil chemical properties

The effects of artificial precipitation with different pH levels on soil chemical properties and element flux were studied in a lysimeter experiment. Cambic Arenosol (Typic Udipsamment) in monolith lysimeters was treated for 6 1/2 yr with 125 mm yr^?1 artificial rain in addition to natural precipitation. Artificial acid rain was produced from groundwater with H₂SO₄ added. pH levels of 6.1, 4 and 3 were used. ‘Rain’ acidity was buffered, mainly due to cation exchange with Ca²⁺ and Mg²⁺, which were increasingly leached due to the acid input. The H⁺ retention was not accompanied by a similar increase in the output of Al ions, but a slight increase in the leaching of Al ions was observed in the most acidic treatment. The net flux of SO₄ ^2? from the lysimeters increased with increasing input of H₂SO₄, but in the most acidified lysimeters significant sorption of SO₄ ^2? was observed. The sorption was, however, most likely a concentration effect. The ‘long-term’ acidification effects on soil were mainly seen in the upper O and Ah-horizons, where an impoverishment of exchangeable Ca²⁺ and Mg²⁺ was observed. An increased proportion of Al ions on exchange sites in the organic layer was observed in the pH 3-treated soil. By means of budget calculations the annual release of base cations due to weathering was estimated to be between 33 and 77 mmol_c m^?2.     

Element Budgets in a Forested Watershed in Southern China: Estimation of a Proton Budget

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.     

Describing soil SO4 2− dynamics in the solling roof project with two different modelling approaches

The release of previously stored soil SO₄ ^2? is tightly connected with the reversibility of soil and water acidification. Thus soil SO₄ ^2? dynamics have to be included when predicting the reversibility of acidification. Our aim was to compare two modelling approaches: The model MAGIC (Cosby et al., 1985) describes SO₄ ^2? dynamics with the Langmuir sorption isotherme. In the SO-MODEL (Prenzel, 1991) a precipitation/ dissolution of jurbanite is defined. Even though it was possible to calibrate both models to lysimeter data of the Solling D1 site in 1 m depth, the prognosis for SO₄ ^2? concentrations in the soil solution differed significantly. While MAGIC predicted the observed gradual decrease of SO₄ ^2? concentration with decreasing deposition, the SO-MODEL calculated stable concentrations up to the year 2026 followed by a sudden drop. Because the prognosis established with the SO-MODEL is incompatible with observed field data, we concluded that the predicted SO₄ ^2? dynamic of the SO-MODEL was unrealistic.     

Acid deposition and ion leaching from a podzolic soil under hardwood forest

The contribution of atmospheric acids to cation leaching from a podzolic soil under mature maple-birch forest in central Ontario was examined during 1983. The movement of base cations was associated largely with NO₃ ^?, SO₄ ^2? and organic acid anions in surface soil horizons, with SO₄ ^2? and NO₃ ^? below the effective rooting zone, and SO₄ ^2? and HCO₃ ^? in streamflow. Mineral soil horizons could adsorb little additional SO₄ ^2? or associated cations at current soil solution SO₄ ^2? concentrations. Therefore it is concluded that the soil in situ lacks a strong affinity for SO₄ ^2?. Current annual inputs to the forest of SO₄ ^2? and NO₃ ^? in bulk precipitation (26.4 and 18.2 kg ha^?1, equivalent to 8.8 kg S and 4.1 kg N ha^?1 , respectively) contributed significantly to cation leaching from the soil. In order to maintain exchangeable cations in soil at current levels, a rate of weathering yielding 29.6, 5.0, 4.4 and 2.2 kg ha^?1 yr^?1 of Ca²⁺, Na⁺, Mg²⁺ and K⁺, respectively, would be required.     

Precipitation Composition in the Ohio River Valley: Spatial Variability and Temporal Trends

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.     

Sulphate sorption by variable charge soils

The sorption of sulphate (SO^2?₄) by three variable charge soils from the Canary Islands (Spain) was studied. Sulphate sorption decreased with increasing pH. Only negligible amounts of SO^2?₄ were sorbed above pH 6.5. When the soils were washed with an indifferent electrolyte (0.01 M KCl), more SO^2?₄ was recovered than had been sorbed. This indicated a release of native SO^2?₄ Sulphate replaced hydroxyl ions (OH) and co-ordinated H₂O molecules, as well as very small amounts of silicate (Si). No measurable amount of phosphate (P) was released. On average hydroxyl release accounted for 50% of SO^2?₄ sorbed, the rest being accounted for by the increase in negative charge as measured by K⁺ adsorption. The results presented here are consistent with the sorption of SO^2?₄ through a ligand exchange mechanism, but in a different plane of sorption to that of phosphate.     

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.     

Chemical fractionation,water solubility and temporal distribution of sheep faecal sulphur fractions in grazed pastures receiving long‐term sulphate fertilization

Abstract

Although over 40% of excretal S is returned to intensively sheep ‐grazed pastures as faecal S, limited information is available on faecal S fractions, their water solubility and temporal distribution. This study reports results obtained from sheep faeces returned to grazed pastures which have received long‐term annual sulphate applications for 15–20 years. Five freshly‐voided sheep faecal samples (<100 g moist faeces per sample) per sampling were randomly collected at approximately one month intervals over a one‐year growing season. Faeces were fractionated into total S, inorganic SO₄ ^2‐, ester SO₄ ^2‐, Hi‐reducible S and C‐bonded S. Results obtained showed that faecal total S, ester SO₄ ^2‐ Hi‐reducible S and C‐bonded S fractions varied significantly throughout the year. Carbon‐bonded S was the dominant (>80%) faecal S fraction, regardless of faecal total S content or the time of year faecal samples were deposited. Faecal ester SO₄ ^2‐ and inorganic _SO₄ ^2‐fractions accounted for 3.3–7.1% and 0.1–14% of faecal total S respectively. Thus approximately 3.4–21.1% of faecal total S was estimated to be potentially leached or readily available to pasture plants. The Hi‐reducible faecal S fraction was significantly‐correlated (r = 0.59***; *** = P ≤ 0.001) with HCl‐extractable faecal inorganic S, which was considered to represent faecal total SO₄ ^2‐ (ester SO₄ ^2‐ and inorganic SO₄ ^2‐ fractions).

The solubility of different faecal S fractions was determined by sequential extraction of ground (< 1 mm) faeces three times (30 minutes per extraction) with water or 0.01 M Ca(H₂PO₄)₂ solution (1: 5 ratio of faecal DM: extractant). Both amounts of water‐extractable and Ca(H₂PO₄)‐extractable faecal S fractions were found to vary significantly throughout the year. Ca(H₂PO₄)₂ tended to extract more inorganic faecal S than water, attributed to the presence of phosphate and the low pH (pH=4) of Ca(H₂PO₄)₂ extractant. A significant proportion (15–25%) of faecal S was extracted by water and most (70%) of this water‐extractable faecal S was in the organic S fraction. Water‐extractable inorganic faecal S probably originated from the faecal total SO₄ ^2‐ fraction as shown by their significant correlation (r = 0.45** ‐0.63***; ** = P≤ 0.01; *** = P≤ 0.001). Some of the faecal S in water extracts may also originate from the faecal C‐bonded S fraction, as a significant correlation was obtained between C‐bonded faecal S and either water‐extractable faecal organic S (r = 0.53–0.57***; *** = P ≤ 0.001) or water‐extractable faecal inorganic S (r = 0.40–0.41*; * = P ≤ 0.05).

Significant amounts of faecal inorganic SO₄ ^2‐ and ester SO₄ ^2‐ fractions were removed by Ca(H₂PO₄)₂ extractant. The Ca(H₂PO₄)₂‐extractable faecal inorganic S was significantly correlated (r = 0.73***^; *** = P ≤ 0.001) with water‐extractable faecal inorganic S.     

Variation in the sensitivity of DOC release between different organic soils following H2SO4 and sea‐salt additions

Long‐term monitoring data from eastern North America and Europe indicate a link between increased dissolved organic carbon (DOC) concentrations in surface waters over the last two decades and decreased atmospheric pollutant and marine sulphur (S) deposition. The hypothesis is that decreased acidity and ionic strength associated with declining S deposition has increased the solubility of DOC. However, the sign and magnitude of DOC trends have varied between sites, and in some cases at sites where S deposition has declined, no significant increase in DOC has been observed, creating uncertainty about the causal mechanisms driving the observed trends. In this paper, we demonstrate chemical regulation of DOC release from organic soils in batch experiments caused by changes in acidity and conductivity (measured as a proxy for ionic strength) associated with controlled SO₄^2? additions. DOC release from the top 10 cm of the O‐horizon of organo‐mineral soils and peats decreased by 21–60% in response to additions of 0–437 µeq SO₄^2? l^?1 sulphuric acid (H₂SO₄) and neutral sea‐salt solutions (containing Na⁺, Mg²⁺, Cl^?, SO₄^2?) over a 20‐hour extraction period. A significant decrease in the proportion of the acid‐sensitive coloured aromatic humic acids (measured by specific ultra‐violet absorbance (SUVA) at 254 nm) was also found with increasing acidity (P < 0.05) in most, but not all, soils, confirming that DOC quality, as well as quantity, changed with SO₄^2? additions. DOC release appeared to be more sensitive to increased acidity than to increased conductivity. By comparing the change in DOC release with bulk soil properties, we found that DOC release from the O‐horizon of organo‐mineral soils and semi‐confined peats, which contained greater exchangeable aluminium (Al) and had lower base saturation (BS), were more sensitive to SO₄^2? additions than DOC release from blanket peats with low concentrations of exchangeable Al and greater BS. Therefore, variation in soil type and acid/base status between sites may partly explain the difference in the magnitude of DOC changes seen at different sites where declines in S deposition have been similar.     

Trends in surface water acidification at ecological monitoring sites in southeastern Canada (1981–1993)

Atmospheric deposition and surface water chemistry have been monitored intensively at 5 geologically “sensitive” sites in southeastern Canada. The sites receive differing acid inputs that span the entire range found in Canada. Surface water data collected at 9 stations from 1981 to 1993 for SO ₄ ^2? , NO ₃ ^? , Alkalinity, DOC, pH, Ca²⁺ and Mg²⁺ have been analyzed to detect monotonic trends. Similarities between the temporal patterns and trends for SO ₄ ^2? in deposition and surface water suggest that they are strongly linked at our sites. Our 13-year datasets showed significant negative SO ₄ ^2? trends at the 3 Ontario sites and a positive trend in Nova Scotia. A climatically-induced SO ₄ ^2? increase in northwestern Ontario has been reversed. Mobilization and export of adsorbed SO ₄ ^2? and/or reoxidized S from the basins of central Ontario sites is delaying their recovery. Two of our 9 stations (in Quebec and central Ontario) are continuing to acidify. The 2 Nova Scotia stations have the highest DOC levels and both exhibit a decreasing trend. Ionic compensation for declining SO ₄ ^2? varies from station to station, sometimes involving an Alk increase, sometimes a base cation decrease, and sometimes more complex combinations. Additional factors (e.g. climatic variation) also influence variable trends, and data records longer than those presently available will be needed to unequivocally verify acidification recovery.     

The contribution of sulfate to rainfall pH around Kilauea Volcano,Hawaii

Between December 1986 and June 1987, the mean pH of rainfall downwind of the Kilauea main vent was found to be 4.5 (range 4.0 to 5.6), 1.2 units higher than the year before (1985-86), although 84% of the 12 sequential samples fell below pH 5.0. The SO₄ content, however, was 34% higher, averaging 18.5 mg L^?1. Upwind, in open forest the mean pH 4.7 was little changed from that measured before. Mean SO₄, however, has fallen to a low of 2.5 mg L^?1, but, more significantly, in 9 out of 12 sequential samples S04 was not detectable at all (i.e. < 0.5 mg L^?1). The calculated pH, assuming 100% H₂SO₄ would be 5.3 yet 58% of these samples fell below pH 5.0, the lowest being 4.0. Disparities between pH measured and calculated on the basis of SO₄ content indicated that other acid species were present in the precipitation. Oxidation of rain samples with H₂O₂ greatly increased SO₄ content and lowered pH downwind, but failed in most samples to alter either parameter in the upwind collections. These observations, together with the elimination of HCl and N03 by others, suggested that SO₂ contributes significantly to acidity downwind, but that in most upwind samples a source of H⁺ other than mineral acids, presumably organic compounds, must be of major importance.     

Sulfur and oxygen isotope ratios in sulfate during an acidification reversal study at Lake Gårdsjön,Western Sweden

The reversibility of acidification is being investigated in a full scale catchment manipulation experiment at Lake Gårdsjön on the Swedish west coast using isotopes as environmental tracers. A 6300 m² roof over the catchment enables researchers to control depositional variables. Stable S isotope values were determined in bulk deposition, throughfall, runoff, groundwater and soil-extracted water during one year prior to and two years of experimental control. Data collected prior to experimental control suggest that the inorganic SO ₄ ^2? pool within the catchment has a homogeneousδ ³⁴S value of about+5.5‰. Sprinkling of water spiked with small amounts of sea-water derived SO ₄ ^2? started in April 1991. Theδ ³⁴S value of this SO ₄ ^2? is around+19.5‰. Since April 1991, the SO ₄ ^2? concentration in runoff has decreased by some 30%, however, theδ ³⁴S value have increased by only 0.5‰. This suggests mixing of sprinkling water S with a large reservoir of S in the catchment. Oxygen isotopes in SO ₄ ^2? suggest that less than one third of the SO ₄ ^2? in runoff is secondary SO ₄ ^2? formed within the soil profile. This is, however, no evidence for net mineralization of S. The SO ₄ ^2? in runoff in the roofed catchment is a mixture of SO ₄ ^2? previously adsorbed in the soil, mineralized organic S and SO ₄ ^2? from the sprinkler water. Calculations based on isotope data indicate that the turnover time of S within the catchment is on the order of decades. Since SO ₄ ^2? facilitates base cation flow, the acidification reversal will take a much longer time than concentration decreases of SO ₄ ^2? would suggest.     

Empirical models for lake acidification in the upper Great Lakes Region

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.     

Aboveground vegetation effects on the deposition and cycling of atmospheric sulfur: Chemical and stable isotope evidence

Up to 60% of the sulfate in upland forest throughfall and stemflow at Plastic Lake in central Ontario is non-precipitation by origin, but is derived from aboveground vegetation. The sources of this aboveground vegetation sulfate include dry deposited aerosols and SO₂, and mineralized plant organic S. σ³⁴S data indicate that atmospheric S dominates the upland forest ecosystems of southern and central Ontario, with little S isotope fractionation. Seasonal σ³⁴S variations in precipitation sulfate may be due to mixing of bacteriogenic and anthropogenic S. σ¹⁸O and concentration data indicate that oxidation of dry-deposited SO₂, and mineralization of organic S on vegetation surfaces may contribute one third or more of throughfall sulfate in summer and autumn, but less in late spring, perhaps due to foliar uptake of S during this season. Oxidized SO₂, or mineralized organic S contributes one third or more of stemflow sulfate during these seasons.     

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.     

Deposition of nutrients and major ions by precipitation in south-central Ontario

As part of a study of the substance budgets of lakes in south-central Ontario, a network of precipitation collectors (8 bulk, 7 wet only) was operated to measure the deposition of nutrients and major ions. Results are reported for total P, total Kjeldahl N, NO ₃ ^? ?N, NH ₄ ⁺ ?N, total N, Fe, H⁺, Ca⁺⁺, Mg⁺⁺, Na⁺, K⁺, SO ₄ ⁼ and CL^? for a two year period (August 1976–July 1978). On an equivalent basis the dominant anion in both bulk and wet precipitation was SO ₄ ⁼ , with H⁺ the dominant cation. Precipitation in the study area is more acidic than that analyzed at any other location on the Canadian Shield to date. Concentrations of ions varied by 1 to 3 orders of magnitude between individual precipitation events and annual deposition varied by as much as 2-fold in the two years of study. Annual wet deposition contributed >60% of bulk deposition for all substances except total P. Seasonal trends in deposition with summer maxima were noted for most ions. For Harp Lake, a small Precambrian Lake with a lake area of 12.6% of its total drainage area, precipitation input directly to the lake surface was an important source of nutrients and major ions. This was especially the case for P, N and H⁺ because these substances were retained by the terrestrial drainage basin.     

Acid deposition near a sour gas plant in southwestern Alberta

Atmospheric fallout in the vicinity of a sour gas plant in southwestern Alberta was collected on an event basis with bulk precipitation collectors during June, July and August of 1972, 1973 and 1982. Samples were collected at 9 sites within 20 km of the plant. Total atmospheric sulfation measurements defined a higher exposure area located downwind of the plant, but the precipitation measurements did not. Bulk deposition of H⁺ ion in the study area was an average 10.77 mmol H⁺ m^?2 3 mol^?1 in 1972 and 0.014 and 0.049 in 1973 and 1982, respectively. 1972 samples were also significantly more acidic (average pH of 4.3 vs 5.7 in 1973 and 5.3 in 1982). Deposition of SO₄ ⁼ averaged 2.1 kg S ha^?1 3 mol^?1 in 1972 and 0.96 and 0.72 in 1973 and 1982. The higher deposition of both S and H⁺ in 1972 is mainly a result of more precipitation. There was no significant correlation between H⁺ and SO₄ ⁼ species in the samples. There was no significant relationship between plant S emissions and deposition rates, or plant S emissions and average total atmospheric sulfation measurements.     

Lysimeter study with a cambic Arenosol exposed to artificial acid rain: I. Concentrations of ions in leachate

The effects of artificial acid rain on soil leachate composition were studied in a lysimeter experiment. Cambic Arenosol (Typic Udipsamment) in monolith lysimeters was treated for 6 1/2 yr with 125 mm yr^?1 artificial rain in addition to natural precipitation. Artificial acid rain was produced from groundwater with H₂SO₄ added. pH levels of 6.1, 4 and 3 were used. Increasing content of H₂SO₄ in the artificial rain increased the concentration of Ca²⁺ and Mg²⁺ in the leachate significantly. The pH of the leachate was slightly reduced only by the most acidic treatment (pH 3). The H^+? retention was not accompanied by a proportionate increase in the Al ion concentration. A slight increase in the Al ion concentration was only observed in the leachate from the pH 3-treated lysimeter. We conclud that cation exchange and/or weathering were the main buffer mechanisms in the soil. The study supports conclusions from other acidification studies, that acidic precipitation is likely to increase the leaching of Ca²⁺ and Mg²⁺ from soils.     

Salts and acids as determinants of the solution composition of acidic forest soils — anion effects

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 S0₄^2? salts and H₂SO₄ induced higher pH and lower Al concentrations than the corresponding Cl^? treatments due to the SO₄^2? 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.