Influence of nitrate and chloride on the adsorption and transport of sulphate in soils

The adsorption and desorption of SO₄ was investigated as a function of KCI and KNO₃ concentration using soils with contrasting surface-charge properties. In the net negatively-charged soils, additions of C1 or NO₃ of up to about 0.05–0.10 M increased the adsorption of SO₄ but at higher concentrations adsorption decreased. In contrast, adsorption by the net positively-charged soils decreased with concentration increase over the entire range (0 to 1 M) investigated. The effects of CI and NO₃ on the adsorption of SO₄ were practically identical. The different pattern of SO₄ adsorption in the two groups of soils in response to addition of KCI or KNO₃ can at least partly be explained in terms of the effect of electrolyte on soil pH. The depression in pH of net negatively-charged soils induced by an indifferent electrolyte favours adsorption of SO₄; but, because pH changes in the opposite direction in positively-charged soils, SO₄ adsorption decreases in these soils. The distribution of a pulse of 35S-labelled SO₄ in soil columns after leaching with KCI solutions, ranging in concentration from 0 (H₂O) to 0.10 M, clearly reflected the manner in which electrolyte concentration affected the adsorption of SO₄. The distribution of ³⁵S was reasonably well simulated using the general transport equation combined with the Freundlich equation to describe the adsorption/desorption of SO₄. In contrast to other inorganic anions (H₂PO₄ and OH) applied in agricultural practice, C1 and NO₃ may have beneficial effects on the S economy of many soils by decreasing leaching losses of SO₄.     

Hydrochemistry of Waters of Volcanic Rocks: The Case of The Volcanosedimentary Rocks of Thrace, Greece

This work is referred to the characterization of the environmental hydrochemistry in the broader Sapes area – Thrace region, on the basis of physico-chemical properties of surface and groundwaters occurring in the volcanosedimentary formations of this area, where gold mining activities are planned to operate. Volcanic rocks are considerably altered where they are in contact with hydrothermal solutions. Aquifers are formed within these formations. Surface and ground waters are strongly metalliferous and their hydrochemical facies present similar but complex water types. Certain characteristic chemical types are the following: Ca-Mg-HCO₃-SO₄, Ca-Mg-SO₄-HCO₃. Ca-SO₄, Ca-Mg-SO₄. Ca-Na-Cl-HCO₃, Na-Cl. A small majority of the water samples present the following order of anion dominance HCO₃ ^? > SO₄ ^2? > Cl^?. Calcium is the dominant cation. Bicarbonates and sulfate ions are the dominant anions. The order of dominance for the heavy metals in surface and ground waters is as follows: Fe > Mn > Zn > Ni > Cu. The saturation index of waters regarding minerals is low. Computer simulation indicates that calcite and dolomite are common minerals in all water samples which are saturated in respect to quartz and argillaceous-siliceous minerals. The most pronounced property of waters is their acidic character. The high metal concentrations are related to water with low pH. Sulfide minerals control the low pH values of waters which is an important control factor for the evolution of the water chemical composition. The abundance of sulfates is attributed to the dissolution of the minerals pyrite (FeS₂) and alunite (KAl₃(SO₄)₂(OH)₆. The water–mineral interactions are responsible for the chemical composition of waters. Water quality problems can be successfully handled by the use factor analysis. 17 chemical parameters can be substituted by five factors which successfully represent the hydrochemical processes as well as their geographic distribution. Volcanic rocks in the study area have the potential to produce acid drainage.     

Studies on Adsorption Characteristics of Al-Free and Al-Substituted Goethite for Heavy Metal Ion Cr(VI)

In the present paper, α-FeOOH and α-Fe(Al)OOH were prepared, and the adsorption of Cr(VI) on the two samples was investigated. The influence of pH, initial concentration, and some anions such as SO₄ ^2?, H₂PO₄ ^?, C₂O₄ ^2?, CO₃ ^2?, and SiO₃ ^2? on the adsorption of Cr(VI) on α-FeOOH and α-Fe(Al)OOH was studied by batch techniques. The results show that the adsorption capacity of Cr(VI) on α-Fe(Al)OOH increases with the introduction of aluminum, but decreases with the increase of pH. The adsorption irreversibility of Cr(VI) on α-Fe(Al)OOH is much higher than that on pure α-FeOOH. The adsorbed Cr(VI) species mainly exists in the form of *Fe(wk)-OHCrO₄ ^2? on the surface of the samples. With the presence of SiO₃ ^2?, CO₃ ^2?, C₂O₄ ^2?, SO₄ ^2?, and H₂PO₄ ^?, the binding of Cr(VI) is inhibited by different degree. The inhibition of those anions is larger in the pure goethite than that in the Al-substituted goethite system. After Al was introduced into α-FeOOH, Cr(VI) ions are preferentially adsorbed on Al sites rather than Fe sites on α-Fe(Al)OOH.     

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.     

Aluminum speciation in soil solutions: Equilibrium calculations

A computer simulation was done to illustrate how the equilibrium solubility and speciation of Al in well-aerated soil solutions may be affected by pH (from 2.0 to 10.0), organic acids (citric, oxalic, phthalic, and salicylic acid), metal ions (K, Mg, Ca, Al, Fe), inorganic ligands (F, OH, SO₄, PO₄, CO₃, and SiO₃), and type of Al-containing solid [kaolinite, gibbsite, or amorphous Al(OH)₃] thought to be present. The simulation indicated that the type of Al-oxide/hydroxide considered has a substantial influence on the inorganic and organic equilibrium composition of the soil solution, and on the occurrence (or non-occurrence) of other Al-minerals such as KA1₃(SO₄)₂(OH)₆ (alunite) and Al(SO₄)(OH)-5H₂O (jurbanite).     

Aluminium and sulphate in acidic soils and groundwaters on the Swedish west coast

Acidic groundwaters and soils in Halland County (Hailands län), southwest Sweden, have been investigated with respect to conditions of soluble aluminium (Al) and sulphate (SO₄ ^2?. Basic Al-sulphate, Fe-oxide, Al-oxide, Al-hydroxide and clay minerals, are discussed and evaluated in their roles for governing Al and SO₄ ^2? in the groundwaters. Based on this investigation, it is suggested that Al³⁺ solubility is controlled by amorphous Al-hydroxide. The SO₄ ^2? in the groundwaters will depend primarily on the H₂SO₄ input. The H₂SO₄ load enhances soil mineral weathering which enhances the production of Fe-oxides, i.e. anion exchange surface sites, to which groundwater SO₄ ^2? attain adsorption equilibra. The factors that control solubility of Al and SO₄ ^2? are both influenced by the acidity in the soil catenas which in the area largely depend on the H₂SO₄ input. Clay minerals such as illite, smectites, halloysite, and variable composition Al-silicates do not exert strong control on Al in the groundwaters investigated.     

Inorganic sulphate extraction from SO2-impacted Andosols

Sulphate sorption on to the surface of short‐range ordered minerals and precipitation of Al‐hydroxy sulphate contribute to the acid neutralizing capacity of soils. The correct measurement of total inorganic sulphate is thus essential in soils that are accumulating SO₄^2– anions. We extracted SO₄^2– by various solutions, namely 0.005 m Ca(NO₃)₂, 0.016 m KH₂PO₄, 0.5 m NH₄F and 0.2 m acidic NH₄‐oxalate (pH 3), from Vitric and Eutric Andosols exposed to prolonged deposition of acid and SO₂ from an active volcano (Masaya, Nicaragua). We attributed sulphate extractable by KH₂PO₄ (20–3030 mg kg^?1) to anion‐exchangeable SO₄^2–, which was much smaller than NH₄F‐ and oxalate‐extractable SO₄^2– (400–9680 and 410–10 480 mg kg^?1, respectively). Our results suggest the occurrence of a sparingly soluble Al‐hydroxy‐mineral phase extractable by both NH₄F and oxalate. The formation of Al‐hydroxy minerals would result from the combination of enhanced weathering caused by strong acid loading and simultaneous occurrence of large SO₄^2– concentrations in soil solution. Oxalate extracted slightly more inorganic SO₄^2– than did NH₄F, this additional amount of SO₄^2– correlating strongly with oxalate‐extractable Si and Fe contents. Preferential occlusion of SO₄^2– by short‐range ordered minerals, especially ferrihydrite, explains this behaviour. If we exclude the contribution of occluded sulphate then oxalate and NH₄F mobilize similar amounts of SO₄^2– and are believed to mobilize all of the inorganic SO₄^2– pool.     

A quality assurance program and quality assessment of the acidic precipitation in Ontario study (APIOS) deposition monitoring networks

Kinetics of H+ consumption by mineral dissolution in a surface soil and a subsoil of an acid woodland soil were studied by means of batch type experiments and stationary pH titrations. Mineral dissolution in the subsoil could effectively be described by congruent dissolution of illite (K_0.6Mg_0.25A1_2.3S1₃0₁₀(OH)₂) followed by an incongruent dissolution stage. In the incongruent stage the concentration of Al decreased while concentrations of K and Mg continued to increase. Congruent dissolution rates of illite could be predicted with power type relationships from transition state theory. In the incongruent dissolution stage the activities of H and Al appeared to be controlled by precipitation of A1(OH)₃. Results of this kind of experiments could be helpful to understand the behavior of Al and base cations in acid soils and soils with high atmospheric loadings of acid. Comparison of the results of batch experiments for a surface soil and a subsoil showed that initially proton consumption in the surface soil is faster and more effective due to the presence of a relatively high cation exchange capacity and base saturation value. However with progressive proton consumption and increasing reaction times proton consumption in the subsoil becomes faster than in the surface soil, presumably due to higher rates of mineral dissolution in the subsoil. Lower dissolution rates in the surface soil may result from lower contents of easily weatherable minerals, due to excessive leaching in the past which is reflected in a 17% lower acid neutralizing capacity than in the subsoil.     

Modelling of Pore Water Nutrient Distribution and Benthic Fluxes in Shallow Coastal Waters (Gulf of Trieste, Northern Adriatic)

Pore waters, extracted monthly from short cores at two sedimentologically and biologically different locations (AA1 and F) in the Gulf of Trieste (Northern Adriatic), were analyzed for NH₄ ⁺, NO₃ ⁺, PO₄ ³⁺, Si(OH)₄, DIC and periodically for DOC, DON and DOP. Nutrient concentrations were used to model vertical profiles using a diffusion-reaction model which included the macrofaunal influence on sediment-water exchange rates. Winter nutrient profiles showed nearly an exponential increase, or decrease in the case of NO₃ ⁺, in nutrient concentrations with depth while the profiles from other seasons exhibited concentration maximum at 3–6 cm, a minimum around 8–10 cm, and then, except for NO₃ ⁺, a gradual increase or constant values. This vertical distribution is attributed to seasonal variations in the benthic infauna activity, mostly composed of polychaetes and bivalves and concentrated in the top 4–5 cm, being less active during the winter. The vertical profiles of DOC and DON showed the vertical distribution described above in all periods, while DOP was similar to that of PO₄ ³. The comparison of modelled fluxes of nutrients across the sediment-water interface at the location AA1 and those measured usingin situ benthic chamber showed quite good agreement for NH₄ ⁺ and PO₄ ³, fluxes but not for NO, and Si(OH)₄. Discrepancies could be caused by a topography effect and for Si(OH)₄ by an additional dissolution of the solid phase balancing the diffusive loss into burrows and lessening the effect of bioturbation.     

Recovery of Surface Waters in the Northeastern U.S. from Decreases in Atmospheric Deposition of Sulfur

A simple mass flux model was developed to simulate the response of SO₄ ^2- concentrations in surface waters to past and anticipated future changes in atmospheric deposition of SO₄ ^2-. Values of bulk (or wet) SO₄ ^2- deposition and dry deposition of S determined from measured air concentrations and a deposition velocity were insufficient to balance watershed SO₄ ^2- export at the Hubbard Brook Experimental Forest, NH and for a regional survey of watersheds in the northeastern U.S. We propose two explanations for the unmeasured S source: 1) a significant underestimation of dry S deposition, and/or 2) internal watershed S sources, such as weathering and/or mineralization of soil organic S. Model simulations based on these two mechanisms agreed closely with measured stream SO₄ ^2- concentrations at Hubbard Brook. Close agreement between measured and model predicted results precluded identification of which of the two mechanisms controlled long-term trends in stream SO₄ ^2-. Model simulations indicated that soil adsorption reactions significantly delayed the response of stream water to declines in SO₄ ^2- inputs since 1970, but could not explain the discrepancy in watershed S budgets. Extrapolation of model predictions into the future demonstrates that uncertainty in the source of the S imbalance in watersheds has important implications for assessments of the recovery of surface water acid neutralizing capacity in response to anticipated future reductions in SO2 emissions.     

阴离子对可变电荷土壤吸附铜离子的影响机理

根据NO-3、Cl-和SO24-对可变电荷土壤和恒电荷土壤吸附Cu2+的影响的比较,探讨了阴离子对可变电荷土壤吸附Cu2+的影响机理。结果表明,当3种阴离子的浓度相同时,在SO24-体系中铁质砖红壤对Cu2+的吸附率较在NO3-和Cl-体系中大得多,而在浓度相同的3种阴离子体系中,黄棕壤对Cu2+的吸附率相差不大。在离子强度相近的NaCl体系中,砖红壤对Cu2+的吸附率相近。在3种阴离子体系中,随着pH升高,砖红壤对Cu2+的吸附率均增大;但在NO-3体系和Cl-体系中Cu2+的吸附率相近;而在SO24-体系中Cu2+的吸附率最大。随着Na2SO4浓度的增大,铁质砖红壤和砖红壤对Cu2+的吸附率减小。但在0.005 mol L-1和0.05 mol L-1Na2SO4体系中,Cu2+的吸附率大于在不含Na2SO4的体系中者。而在0.5 mol L-1Na2SO4体系中,Cu2+吸附率小于在不含Na2SO4体系中者。在3种浓度的Na2SO4体系中,黄棕壤对Cu2+的吸附率均小于在不含Na2SO4体系中者。总之,阴离子可通过离子强度、专性吸附和形成离子对影响土壤对Cu2+的吸附。在可变电荷土壤中,阴离子对Cu2+吸附的影响机理较在恒电荷土壤中复杂得多。     

Geochemical Behavior of Arsenic in Kelly Lake,Ontario

The objective of this study was to investigate the geochemical behavior of As in Kelly Lake, Ontario. A total of 65 water samples were collected from August 1998 to October 1999. Concentrations of As (total, dissolved and particulate) were determined in each water sample. Thermodynamic models suggest that As interactions with Fe hydroxides could limit As concentrations in Kelly Lake water samples (by adsorption and forming arsenate minerals). It was concluded that Fe(II) arsenates (and not Fe(III) arsenate) formation/dissolution could control As concentrations in Kelly Lake. The activity of As (in terms of HAsO₄ ^2-) in the water samples was calculated from the monitoring data. The calculated activities were superimposed on the thermodynamic model of As minerals. All the calculated activity observations clustered around the Fe₃(AsO₄)₂.8H₂O(c)/Fe₄Fe₂(OH)₁₂. SO₄(c).These observation suggest that the solubility of As in Kelly Lake is controlled by the equilibrium of Fe₃(AsO₄)₂.8H₂O(c)/Fe₄Fe₂(OH)₁₂.SO₄(c), as suggested by thermodynamic solubility isotherms. The As concentration data were limited and spatial trend could not be verified in Kelly Lake water samples, although a decreasing trend in As concentrations at all depths was noticed from June to October 1999.     

Fracht an chemischen Elementen in den Niederschlägen im Solling

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

Mechanism of sulphate adsorption by two tropical SoilS

The mechanism of sulphate (SO₄) adsorption was investigated using two highly-weathered soils with contrasting surface-charge characteristics (one with a net negative charge and the other with a net positive charge). The addition of SO₄ caused a release of OH and increased the adsorption of cations, in keeping with the widely-held view that SO₄ is chemisorbed by replacing -OH and -OH₂ ligands. On the other hand, adsorbed SO₄ was completely recovered by washing with an indifferent electrolyte solution (1 M KC1), an extractant which is usually taken to be specific for ‘exchangeable’ ions. The amounts of SO, adsorbed were several times higher than those of non-specifically adsorbed Cl. It is suggested that the experimental observations can be interpreted in terms of a model in which SO₄ adsorbs in a plane closer to the surface than monovalent anions (e.g. in the Stern layer). The consequence of higher counter-ion valence and proximity to the surface is that additional positive charge is induced onto the surface by OH release. Charge reversal in the diffuse layer allows more cations to be adsorbed. This type of adsorption may involve forces other than the purely electrostatic but, in contrast to chemisorption, the adsorbed anion does not become chemically coordinated to the surface metal atoms.     

Changes in the concentrations and speciation of aluminum in response to an experimental addition of ammonium sulfate to the bear Brook Watershed,Maine, USA

An understanding of the biogeochemistry of aluminum (Al) in acid-sensitive terrestrial and aquatic ecosystems is critical to assessments of the effects of acidic deposition. Bear Brook Watershed, Maine, USA includes paired watersheds, East Bear and West Bear. Starting in November 1989, experimental additions of ammonium sulfate ((NH₄)₂SO₄; 900 mol/ha-yr) have been made to West Bear Brook Watershed. Chemical analysis of soil and stream waters were conducted to evaluate the speciation of Al prior to (1987–89) and following (1989–92) the experimental treatments. Before the treatments, soilwater Al occurred largely as inorganic monomeric Al (Ali). Concentrations of organic monomeric Al (Alo), Ali and dissolved organic C (DOC) were high in soil solutions draining the E horizon, and decreased in the lower mineral soilwater (Bs horizon) and streamwater. Streamwater concentrations of monomeric Al (Alm) were largely in the form of Alo. After the (NH₄)₂SO₄ treatments were initiated in the West Bear Brook Watershed, concentrations of Alm increased in soilwater and streamwater, largely as Ali. These increases in Al accompanied decreases in pH and increases in concentrations of SO₄ ^2? and NO₃ ^? in drainage waters. Increases in stream concentrations of Al were particularly evident during high flow events. This pattern, coupled with the increases in concentrations of Ali in upper soilwaters in response to the (NH₄)₂SO₄ addition, suggests that episodic increases in Ali were due to inputs of water entering the stream from shallow hydrologic flowpaths.     

Inorganic anion sorption and interactions with phosphate sorption by hydrous ferric oxide gel

The sorption of inorganic anions by hydrous ferric oxide gel (Fe gel) from 10 ^?1 M NaClO₄ at pH 6.5 decreased in the order: orthophosphate (H₂PO₄)>arsenate (H₂AsO₄) = selenite (HseO3) > silicate (H₄SiO₄) > molybdate (MoO²₄^?) > sulphate (SO²₄^?) > selenate(SeO²₄^?)>chloride (Cl^?) = nitrate (NO^?₃). When each anion was added to Fe gel with an equimolar quantity of H₂PO^?₄, there was no detectable effect of SO²₄^?, SeO²₄^?, Cl^?, and NO^?₃ on the amount of H₂PO^?₄ sorbed. Other anions depressed H₂PO₄ sorption in the order H₂AsO₄ >HseO₃ > H₄SiO₄ > MoO²₄. At the lowest level of anion addition (500 mmol kg ^?1), H₂PO₄ sorption was depressed by no more than 6% of the sorption level in the absence of a competing anion. In contrast, at the highest level of anion addition (1700 mmol kg-¹ of each), H₂AsO₄ decreased H₂PO₄ sorption by 44%. The sorption of SO₄^? was completely eliminated when this anion was added with equimolar amounts of H₂PO₄. The ability of anions to compete with H₂PO₄ for sorption sites could not be explained solely by the results obtained for the sorption of each anion alone. Thus, H₂AsO₄ was more competitive than H₂PO₄ when added together, even though more H₂PO₄ than H₂AsO₄ was sorbed when each anion was added alone. Although H₂PO₄ was sorbed in larger amounts, there is no evidence to suggest that H₂PO₄. H₂AsO₄, and HseO₃ were sorbed on different sites.     

Extractability and dissolution kinetics of pure and soil-added synthesized aluminium hydroxy sulphate minerals

Various extractants used in current analytical procedures for the fractionation of sulphur (S) in soils were compared with respect to their ability to dissolve Al hydroxy sulphate minerals of defined composition (basaluminite, K alunite, mixtures of basaluminite and Na alunite). The minerals were synthesized and aged in the laboratory at 20°C and 50°C. The dissolution kinetics at 20°C of these Al hydroxy sulphates in deionized water, 0.02M HCl and 0.02M NaOH were also investigated. The dissolution stability of the Al hydroxy sulphate minerals increased in the order basaluminite < K alunite < Na alunite. The dissolving power of the reagents used increased in the order H₂O ≤ 0.016M KH₂PO₄? 0.02M HCl ≈ acidic NH₄ oxalate ≈ 0.5M NaHCO₃ < Na₂ CO₃/NaHCO₃ < 0.1M NH₄F < 0.5M NH₄F < 0.05M NaOH ≤ 0.05M LiOH. In Al hydroxy sulphate-containing soils, inorganic S is probably understimated and ester sulphate S overestimated, if the inorganic S pool is assessed by extraction with KH₂PO₄, Ca(H₂PO₄)₂ or NaHCO₃ solutions. The dissolution of all studied Al hydroxy sulphates, particularly that of K and Na alunite, in H₂O and 0.02 M HCl is strongly delayed by kinetic restraints. Thus it seems unlikely that Al³⁺ or SO^2?₄ activites in soil solutions are strictly regulated by precipitation/dissolution equilibria of these minerals except for horizons with extraordinarily slow seepage water movement.     

Increase in Cation Adsorption Induced by Surface Complexation of Sulfate on Andisols and Prediction by “Four-Plane Model”

Abstract

The “Four-plane model” is one of the surface complexation models developed for analyzing the electrostatic charge of synthetic oxides. This model which was applied to the B horizon of Andisols, was equilibrated with an electrolyte solution containing KCl, KNO₃, K₂SO₄ in the concentration range of 0.0033, 0.01, 0.033, 0.1 M, and pH range of 2 to 11. The amounts of NO₃ ^-, Cl^-, SO₄ ^2-, and K⁺ adsorbed were determined from the products remaining in the liquid phase. The increase in the pH value results in the increase of K⁺ adsorption, and decrease of anion adsorption. The increase in the equilibrium concentration increased both K⁺ and anion adsorption. The parameters of the model were determined by measurements and the iterative method. The model have a good agreement between calculated and measured values of cation and anion adsorption. Among the anion species, the amount of adsorbed anions was in the order of SO₄ ^2-?Cl^->NO₃ ^-. The differences in the degree of adsorption were mainly associated with the differences in the equilibrium constants of surface complexation. The surface complexation of the anions produced a negative charge and increased cation adsorption. The degree of surface complexation was most significant in the K₂SO₄ solution, and the phenomenon was considered to be important not only for anion adsorption but also for cation adsorption on Andisols.     

Regional chemical characteristics of lakes in North America: Part I — Eastern Canada

Data defining the major ion chemistry of lakes located in eastern Canada have been compiled for the purpose of evaluating the current status of surface water quality in relation to acidic deposition. A companion paper for lakes in the eastern United States (i.e. Part II, Linthurst et al., 1986) has been prepared also. Data sources in Canada included the National Inventory Survey, the Ontario Lake Sensitivity data set, and the National Aquatic Data base which provided an overall data base of approximately 5700 lakes. Only recently collected data (largely 1980 or later) were used in the analysis. Frequency distribution statistics were obtained for pH, acid neutralizing capacity (ANC), SO₄ and organic anion (A^?) concentrations. Acidic and low ANC waters in eastern Canada occur in a pattern explained by a combination of biogeochemical factors and atmospheric deposition. Nova Scotia contained the highest proportion of acidic and ultralow ANC lakes of any region surveyed in eastern North America; since this region receives approximately 20 kg.ha^?1.yr^?1 wet SO₄ deposition, the proposed target loading may be too high to protect the highly sensitive waters of Maritime Canada. Compared to the rest of eastern Canada, lakes in Ontario have relatively high ANCs due to the influence of CaCO₃ contained in the glacial till of the area. Variation in the SO₄ concentration of lakes approximately follows expected gradients in wet SO₄ deposition. Naturally occurring organic acids do not play a dominating role in the acidification of eastern Canadian lakes.     

Evaluation of the sulphur status of some soils from Portugal

Total S, extractable SO₄, and SO₄^? retention capacity were determined in a range of soils covering the dominant soil groups in Portugal which are expected to show S deficiency. Total S was relatively low (83–435 mg S kg^?1) in all soils and KH₂PO₄^? extractable SO₄ was, in general, low for plant growth, ranging from 0.9 to 32.2 mg S kg^?1. SO₄^? retention capacity ranged from ?33.1 to 64.7 mg S kg^?1 and was negative in many (14 out of 20) of the soils. Most of the soils are expected to be S deficient and show extensive leaching of SO₄. Other selected soil properties that may affect the chemistry of SO₄ were determined. A highly significant simple correlation was obtained between SO₄ adsorbed and extractable Al by the Mehra and Jackson method (CDB-Al) (r = 0.74; P < 0.001). A multiple regression which included silt improved the correlation of SO₄ adsorbed with CDB-Al (r = 0.79; P < 0.001).