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1.
Pyrite and siderite oxidation in swamp sediments   总被引：3，自引：0，他引：3  
Differences in the processes of pyrite and siderite oxidation, in reclaimed swamp sediments of the Skjernå delta (Denmark), are described from sediment chemistry, mineralogy and pore water chemistry. Pyrite oxidation leads to extreme soil acidification, with pH dropping to about 2, the release of large amounts of weathering products to the pore water, and the precipitation ofiron oxides, jarosite and gypsum. Siderite oxidation results only in moderate soil acidification where the pH does not drop below 3.5, while part of the acidification is due to the oxidation of small amounts of sulphur compounds together with siderite. The release of weathering products to the pore water is limited and only iron oxide is precipitated. Calculations indicate that equilibrium with amorphous FeOOH, gypsum and amorphous Al(OH)3 sets an upper limit to the Fe3+, SO4 and Al concentrations in the pore water.  相似文献   

2.
Changes in mineral composition occurring in pyrite‐containing sediments under aerobic conditions are complex and not fully understood. The objective was to study the mineral formation and dissolution of silicates using ion activity product (IAP) calculations and x‐ray diffraction (XRD) on samples of different degrees of pyrite oxidation. Three sediment samples were obtained from the open‐cut brown coal mine of Zwenkau (Saxony, Germany) with low (ZL: 28 g kg—1), medium (ZM: 67 g kg—1) and high (ZH: 95 g kg—1) pyrite contents. These samples were oxidized in the laboratory for 3, 20, 67, and 130 days to obtain four different degrees of pyrite oxidation for each sediment. Sequential batch experiments were carried out for each sediment and oxidation status. Additionally, cation exchange capacities were determined. XRD showed the formation of gypsum (all sediments), jarosite (ZM, ZH), and rozenite (ZH) with increasing pyrite oxidation. IAP calculations suggested an occurrence of gypsum in all samples, of schwertmannite in slightly (ZH) and moderately oxidized (ZM, ZL) samples, and of alunite in a moderately oxidized sample (ZL). The contents of feldspar (ZL), mica/illite (ZL, ZH), and kaolinite (ZH) decreased with increasing pyrite oxidation. The cation exchange capacities of the sediments decreased by 20 (ZH) to 70 mmolc kg—1 (ZM). The change in mineral phases with increasing oxidation status of the sediments also changed the activities of Al, Fe, and SO4 in solution phases. The results obtained in this study suggested the usefulness of predictive models to estimate sediment and water acidification due to pyrite oxidation.  相似文献   

3.
Elementary pedogenetic processes forming gypsic pedofeatures in gypsiferous soils are discussed. Several groups of such processes are distinguished: (1) weathering of gypsum-bearing rocks; (2) gypsum formation associated with weathering of sulfuric (pyritic) rocks; (3) precipitation of gypsum owing to the inflow of soil solutions saturated with Ca and SO4 and their evaporative concentration; (4) gypsum formation owing to exchange reactions in soils between calcium in the exchange complex and sodium sulfate solutions; (5) gypsum formation upon interaction of calcium carbonates with sodium sulfate water resulting in the loss of CaCO3 and gypsum accumulation (decalcification process); (6) colluvial and alluvial redeposition of gypsum in the landscape with its accumulation in the subordinate positions, where gypsiferous soils are formed; and (7) eolian deposition of gypsum on the soil surface with the formation of gypsum-bearing horizons. The micromorphological specificity of the gypsic pedofeatures reflects the processes of their destruction and/or accumulation in the soil profiles. It is shown that gypsum accumulation in soils is a pedogeochemical process that manifests itself in different natural zones upon the presence of gypsum sources.  相似文献   

4.
Abstract

A refined scheme for the semi micro chemical analysis of sulfur fractions in soils is presented. Pyrite is analyzed, as iron, after extraction in HNO3. Non‐pyrite iron is excluded by a pretreatment with HF/H2SO4. Water‐soluble sulfate and jarosite [KFe3(SO4)2(OH)6], the other dominant sulfur fractions in acid sulfate soils, are analyzed turbidimetrically, as sulfate, after successive extractions by EDTA.3Na (water soluble plus exchangeable SO4) and by hot 4 M HCl (jarosite). These methods are simpler, less bulky and more specific than most existing procedures.

Introduction of elemental sulfur analysis permits estimation of organic sulfur fraction as well. Sums of individual sulfur fractions agree well with separate total sulfur determinations.

The proposed analysis of pyrite permits also distinction of the components Fe2O3, FeO and FeS2 in soils and rocks2.  相似文献   

5.
Crop and native plants can be characterized as high and low nutrient‐adapted based on their expected response to native and applied nutrients. Our objective was to compare the plasticity of biomass allocation and tissue nutrient concentrations to added sulfur (S) and nitrogen (N) across a continuum of high and low nutrient‐adapted grasses, represented by barley (Hordeum vulgare), smooth brome (Bromus inermis), bluebunch wheatgrass (Pseudoroegneria spicata), and Idaho fescue (Festuca idahoensis). In our greenhouse study, treatments included two S sources (pyrite and gypsum), at 150 and 300 kg S ha‐1, N at 50 kg ha‐1, and a check. Shoot biomass of barley, smooth brome, and bluebunch wheatgrass was enhanced by S plus N. Shoot biomass of barley and smooth brome was greater with pyrite than with gypsum. Root biomass of smooth brome and bluebunch wheatgrass was greater with pyrite than with gypsum. Plant S concentrations of barley and Idaho fescue were enhanced by added S. Plant S concentrations in barley and smooth brome were greater with gypsum than with pyrite. Except for barley, plant S pools (shoot biomass x shoot S concentration) were enhanced with S plus N compared with no added nutrients. Nitrogen pools of barley, smooth brome, and bluebunch wheatgrass were higher with pyrite than with gypsum. Soil sulfate (SO4) was greater when S or S plus N was added than without any added nutrients. For barley and smooth brome, soil sulfate tended to be lower with pyrite than with gypsum. For all soils, pH was lower with added S or added S plus N compared with unamended soils. While pyrite lowered soil pH, gypsum tended to increase soil pH. Overall, barley and smooth brome were highly plastic in responding to enhanced nutrient levels, bluebunch wheatgrass was relatively responsive, and Idaho fescue was least responsive.  相似文献   

6.
There is a declining gradient of wet SO4 deposition from south to north in Nova Scotia with the highest values being in the south, along with a localized increase around the Halifax metropolitan area, due to local SO4 emission. Edaphic conditions such as drainage from soils containing gypsum or drainage on disturbed rocks containing pyrite, provide additional SO4 to surface waters.Acidity is usually absent in the former (pH > 7.0) and very high in the latter (as low as pH 3.6). By contrast peaty, organic drainages release water low in SO4 during the growing season but they release high amounts of organic anions (A?), consequently, these waters maintain decreased pH values, usually < 4.5. A study of over 80 wetlands and lakes during the ice free period in Nova Scotia showed that sea salt corrected SO4 concentrations range from 45 ueq L?1 in the south end of the province, ～30 ueq L?1 in the Kejimkujik area and < 17 ueq L?1 in the northern areas with values > 85 ueq L?1 in the Halifax area, reflecting the atmospheric deposition pattern of SO4 The SO4 concentrations may be > 2000 ueq L?1 in drainages containing gypsum, > 700 ueq L?1 in drainages over pyrite bearing socks but < 20 ueq/L?1 in streams draining bogs. The SO4 concentrations change considerably during the non-growing season when the ground is saturated with water or frozen, and the runoff is high (snow and rain often alternate in winter). Under such conditions SO4 concentration drops in the two former cases and increases in bog drainages, accompanied with a considerable drop in (A?) concentrations. Care should be taken when interpreting SO4 concentrations in surface waters in Nova Scotia with respect to atmospheric SO4 deposition.  相似文献   

7.
Secondary reactions occurring in pyrite‒containing sediments under aerobic conditions are complex and are not fully understood. Objectives were to (i) study the formation of secondary minerals using x‒ray diffraction (XRD) and ion activity product (IAP) calculations; (ii) to obtain a budget of acidity producing and consuming processes; and (iii) to study the performance of a chemical equilibrium model (including kinetic reactions) using sequential batch experiments with varying input solutions on samples of different pyrite oxidation states. A sediment sample from the open pit coal mine Garzweiler, Germany, was oxidised in the laboratory to obtain four different pyrite oxidation states. Sequential batch experiments were carried out using H2O, 100 mM CaCl2 and 10 mM NaOH as input solutions. A coupled equilibria model was used to describe the experiments. The model (PHREEQC) included inorganic complexation, redox reactions, precipitation/dissolution of sparingly soluble salts, multiple cation exchange and pyrite oxidation using a simple input function. IAP calculations and XRD showed the formation of large amounts of gypsum with increasing pyrite oxidation and for the highly oxidised sample also the formation of hydroniumjarosite. The budget of acidity consuming processes followed the order (i) release of Fe(III) into the solution phase (51% of produced acidity); (ii) Al release into solution and exchangeable phases (probably mainly due to silicate weathering, 22% of produced acidity); and (iii) CEC reducing processes (11% of produced acidity). Modeling of the sequential equilibration experiments with water and CaCl2 gave satisfactory agreements between modeled and measured pH and sorption values, indicating that the main processes governing pH and ion sorption were quite well understood. However, model results of the alkaline additions at larger pyrite oxidation states differed considerably from the experimental results.  相似文献   

8.
To evaluate the effectiveness of soil covers, column experiments were conducted on tailings protected by a three-layer soil cover and tailings directly exposed in the open laboratory for a period of 760 days. Periodic rain application was performed to simulate field conditions, and at four times during the experiments the pore water was completely flushed out of each column for analysis. Profiles of oxygen, temperature, and volumetric water content were measured throughout the experiment, and the post-testing pore water quality was also characterized. A one-dimensional semi-analytic diffusion model was used to simulate oxygen profiles in the uncovered tailings. Modelling performed using the geochemical code MINTEQ showed that in the laboratory, aluminium concentrations in the tailings pore water were controlled by Al(OH)SO4, sulphate by gypsum and Al(OH)SO4and iron by lepidocrocite in the upper half and by ferrihydrite in the lower half. In the field, however, the iron oxyhydroxide minerals formed in the oxidized zone appear to be dissolving. It was found that the cover was effective in preventing significant desaturation of the clay, even over a 150-day drying period. The covered tailings did not oxidize much during the experiments. In the uncovered tailings, oxygen modelling and examination of the geochemistry show that the rate of gross oxidation and the advancement of the oxidation front decreases with time. However, pore water quality is controlled by geochemical processes other than oxidation, as reported in the field.  相似文献   

9.
Abstract

The beneficial action of gypsum in suppressing aluminum (Al) toxicity in Bt horizons of Ultisols is related to the self‐liming effect of the adsorption of sulphate (SO4 2‐) ion. The relationship between SO4 2‐ adsorption by gypsum‐amended soils and some components and properties of 38 surface and subsurface horizons from seven Palexerults in western and central Spain was analyzed. The highest correlations of maximal SO4 2‐ adsorption as determined from langmuir isotherms were with clay, free iron oxyhydroxides (Fedcb), and exchangeable Al contents, and pH. Liming reduces SO4 2’ ion adsorption; consequently, the joint application of limestone and gypsum to the surface of these soils results in increased availability of gypsum for the subsurface horizons.  相似文献   

10.
The study of mineral components in respirable particles (particulate matter with diameter less than 10 μm, PM10) in ambient air is important in understanding and improving air quality. In this study, PM10 samples were collected in various areas around Beijing during 2002～2003, including an urban setting, a satellite city and a rural area. The mineralogical composition of these PM10 samples was studied by X-ray diffraction (XRD), environmental scanning electron microscopy / and energy-dispersive X-ray analyzer (ESEM/EDX). The results indicated that mineral composition of PM10 in different seasons and in different region varied significantly. Mineral mass concentration in Beijing PM10 reached the highest percentage in the spring and fell to the lowest level in the autumn. The minerals in the spring PM10 were dominated by clay minerals and quartz, followed by plagioclase, K-feldspar, calcite, dolomite, hematite, pyrite, magnesite, gypsum and laumontite as well as some unidentified materials. Fewer mineral types were collected in summer, however some new components, including K(NH4)Ca(SO4)2·H2O, NH4Cl and As2O3·SO3 were noted to be present, suggesting that atmospheric chemical reaction in Beijing air were more active in summer than in other seasons. Mineral components in Beijing urban air were at a higher percentage with fewer phases than that in satellite city air. In conclusion, there was considerable variation in mineral components in PM10 samples collected in different seasons and areas, which reflects the related air quality of sampling areas.  相似文献   

11.
An old lead mine tailings pile in Southeast Missouri is being used as a sanitary landfill. The tailings were found to consist of 60–70% dolomite, 20–30% mascovite/illite and trace amounts of quartz, galena, and calcite. The pH was 8.1 and the lead concentrations were 810-3200 mg/kg. Several samples at the site were found hazardous using the EPA toxicity characteristic leaching procedure (TCLP). Since little was known about the mobility of the lead under these conditions, laboratory scale column experiments were conducted to determine if the lead in the tailings might be mobilized with a landfill leachate. Total lead was determined and lead availability was determined using sequential extraction. The lead associated with Fractions 1 (MgC12), 2 (NH4OAc), and 3 (Na4P2O7) of the sequential extraction leached rapidly and immediately produced a leachate after 1 hr of 440 mg/L before decreasing to 40 mg/L after 12 hr. Fraction 4 (EDTA) and Fraction 5 (HNO3), were unaffected by the leachate.  相似文献   

12.
A great deal of research effort has been undertaken to find an effective solution to the problem of acid mine drainage. Indeed, Canadian legislation requires mining companies to respect environmental regulations by providing a rehabilitation plan with a financial guarantee. In order that the Canadian mining industry remains competitive, the proposed solutions have to be not only efficient but also economic, that is why the use of another waste material is attractive. The main objective of this study was to investigate the technical and environmental feasibility of stabilizing acid mine residues using alkaline paper mill waste produced by the pulp and paper industry as a basic source. The mineralogical characterization of the alkaline paper mill shows that calcite is the dominant mineral with hydrated lime (portlandite) present at a low content. The mineralogical characterization of the mining residues shows a polyphasic system where silica dominates the oxidized zone. On the other hand, a high pyrite content is present in the non-oxidized zone. The essential observations that emerge from the leaching tests undertaken in the laboratory can be summarized by the efficiency of the incorporation of the alkaline paper mill waste (1/3 waste and 2/3 mining residue) on the production of acid mine drainage. In fact, it can be observed that there is a reduction of the high toxicity elements like heavy metals. The increase in pH permits the reduction of catalytic bacterial activity and reduces the rate of oxidation in the mining residue.  相似文献   

13.
In a study of the effect of montmorillonite on the dissolution of BaSO4 (barite), SrSO4 (celestite), and226Ra from U mill tailings, it was found that: (1) More of these substances dissolve in an aqueous system that contains montmorillonite than dissolve in a similar system without clay, due to the ion exchange properties of the clay; (2) Na-montmorillonite is more effective in aiding dissolution than is Ca-montmorillonite; (3) the amount of Ra that moves from mill tailings to an exchanger increases as solution sulfate activity decreases. Leaching experiments suggest that226Ra from H2SO4-Circuit U mill tailings from Edgemont, South Dakota, is not present as pure Ra sulfate or as an impurity in anhydrite or gypsum; it is less soluble, and probably occurs as a trace constituent in barite.  相似文献   

14.
The application of the synchrotron technique of the third generation in soil science has permitted researchers to perform a quantitative mineralogical microanalysis in undisturbed samples and to reveal the relationship between the microelements and the solid phase of soils. Three principal methods are used in this technique: microfluorescence (μXRF), microdiffraction (μXRD), and the expanded analysis of the fine structure of the adsorption spectra. By the data of EXAFS spectroscopy, secondary arsenic was found to occur in three forms in soils, i.e., As adsorbed on iron hydroxides, scorodite (FeAsO4 · 2H2O, and As5+ containing jarosite. Despite the high share of carboxyl groups in the organic substance of soils, lead is more readily chelated by the functional groups of aromatic rings to form bidentant complexes. Lead phosphates are the most stable form of Pb in soils. One of the phosphates, i.e., pyromorphite Pb5(PO4)3Cl has been found in ore tailings, lawn soils, soils near some chemical plants, and in soils within geochemical anomalies. The secondary Zn compounds are represented by Zn-containing silicate (kerolith) Si4Zn3O10(OH)2 and, to a lesser extent, by zinc fixed by manganese oxides (birnessite) and iron hydroxides (feroxyhyte).  相似文献   

15.
Mine waste rock can produce acid rock drainage (ARD) when constituent sulphide minerals (for example, pyrite) oxidize upon exposure to the atmosphere. Outdoor experiments were performed to test techniques for preventing and controlling ARD in a pyritic mine waste rock. The experiments involved lysimeter (plastic drum) experiments in which the crushed (25–50 mm particle sizes), amended and unamended waste rock was exposed to natural weather conditions (rain, drying, freezing and thawing) for 125 weeks. The amendments consisted of separately covering the waste rock with compacted soil, wood bark and water and mixing with limestone and phosphate rock at 1 and 3%. Waters draining the various rocks were collected and analyzed for acidity, pH, sulphate and metals. In general, concentrations of SO4 2-, Fe, As, Cu, Al and Mg in the drainage from the control rock increased gradually in the first year, peaked in the second year and increased further in the third year, reflecting increasing acid generation with time. SO4 2- displayed strong positive correlation (0.91 to 0.98) with Al, As, Cu, Fe and Mg.Concentrations of Zn, Mn and Cd reached their maximumin the second year. Geochemical analysis of thecomplete water quality data using the equilibriumspeciation model WATEQ4F suggested waste rockoxidation was most likely controlled by Fe3+. Al, SO4 2- and Fe concentrations in thecontrol rock appeared to be controlled by alunite(KAl3(SO4)2(OH)6), jarosite(KFe3(SO4)2(OH)6) and amorphousferric hydroxide [(am)Fe(OH)3] during the firstyear. Ion activity product data (log IAP) forFe3+ and OH- generally ranged between –37and –34 in the first two years but decreased to –39and –40 in the third year, suggesting that amorphousferric hydroxides were beginning to crystallize intomore stable forms such as ferrihydrite (Fe[OH]3)and goethite (FeOOH) in the third year. The addedlimestone lost its effectiveness after a while,probably because of precipitation of secondaryminerals on the limestone particles. The phosphaterock could not sustain the drainage pH above 6 andlost its effectiveness before the limestone did. Underthe conditions of the experiments, the soil cover didnot work as expected, probably because of sidewallpassage of oxygen and water. The water cover was themost effective control method, reducing the acidproduction rate data from 41 to only 0.08 mgCaCO3 week-1 kg-1 waste rock. The wood bark was theworst performer and accelerated acid production by 170%.  相似文献   

16.
In recent years, elevated arsenic concentrations in groundwater used for drinking water supplies have been recognised in the Madrid Tertiary detrital aquifer. Although only natural causes have been suggested as the source of arsenic, this study aims to highlight that the anthropogenic contribution cannot be disregarded. During the sub-catchment??s areas sampling, we found many geographical sites where natural arsenopyrite [FeAsS] originally encapsulated in pegmatite bodies and quartz veins, was artificially outcropped and dumped out, since mining wastes were scattered and exposed to weathering. Several mineral and ground specimens were collected to analyse its mineralogical and chemical composition by X-Ray Diffraction (XRD) and X-Ray Fluorescence (XRF) spectrometry and by Environmental Scanning Electron Microscope (ESEM). Both, the abundant existence of secondary phases, such as scorodite [FeAsO4?2H2O] and jarosite [KFe3(SO4)2(OH)6], much more soluble than arsenopyrite, and the lixiviation experiments of arsenopyrite in acidic media to simulate acid mine drainage (AMD) conditions, usually found in old mining districts, point to a potential risk of arsenic contamination of surface water bodies, which operate as recharged waters of the aquifer in the studied area. The elemental determination of heavy metals present in ground samples by XRF analyses, reaching up to 1,173 mg kg?C1 of copper, 347 mg kg?C1 of lead and 113,702 mg kg?C1 of arsenic; and the physicochemical and arsenic fractionation studies of soil samples, led us to classify the soil as Spolic Technosol (Toxic). The contamination of the area due to old mining activities could release arsenic to Madrid water supplies; accordingly, additional decontamination studies should be performed.  相似文献   

17.
Abstract

An adequate supply of available Ca in the soil solution of the pegging zone during fruit development is required for production of high yields of high quality peanuts (Arachis hypogaea L.). On low Ca soils, application of gypsum during early bloom is recommended in order to ascertain adequate availability of Ca. Reaction of gypsum in soils under leaching conditions vary considerably and play an important role in fruit development and yield of peanuts. A laboratory study was conducted in leaching soil columns to investigate the effects of one gypsum amendment on leaching of Ca, K, Mg, and SO4 to a depth of 8 cm (fruiting zone of peanut). Six soils of varying physical and chemical properties representative of major peanut growing soils in Georgia were utilized. Following leaching with 15 cm water through gypsum‐amended soil columns, 50% to 56% and 74% to 77% of applied Ca and SO4, respectively, were leached below 8 cm in the sandy‐Carnegie, Dothan, Fuquay and Tifton soils. The respective values for the sandy clay loam‐Greenville and Faceville soils were 28% to 36% and 58% to 69%. Lower initial Ca status and greater leaching of Ca from the applied gypsum in the sandy soils as compared to sandy clay loam soils suggest greater beneficial effects of supplemental gypsum application for peanut production in the former soils than in the latter soils. Leaching of K or Mg (as percentage of Mehlich 1 extractable K or Mg) in gypsum‐amended treatment was considerably greater in sandy soils than that in the sandy clay loam soils. In view of the reported adverse effects of high concentrations of soil K and Mg in the fruiting zone on the yield and quality of peanuts, greater leaching of K and Mg from the fruiting zone in gypsum amended sandy soils enable them to maintain a favorable cation balance for the production of high yields of quality peanuts.  相似文献   

18.
Purpose

Soils have the ability to retain potentially toxic elements (PTEs) through different chemical processes that promote low mobility of these elements, such as the precipitation of secondary phases of Fe, which facilitate the adsorption/co-precipitation of PTEs. The main objective of this study was to evaluate the mobility of PTEs present in an acid solution in two soils with different concentrations of calcite, understanding the role of secondary iron phases in the retention of these elements.

Materials and methods

To evaluate this phenomenon, intact soil columns of two different types of soils from the Sonora River in Northwest Mexico were exposed to an acid solution with high concentration of dissolved PTEs (mainly Fe, Al, and Cu).

Results and discussion

The Tinajas soil was free of carbonates while the Bacanuchi soil had more carbonate content than the Tinajas soil. Secondary precipitates corresponding to secondary phases of iron (mainly ferrihydrite and jarosite) were identified by X-ray diffraction. Using scanning electron microscopy, the PTEs retained in the soils were identified. The presence of calcite favored the neutral pH values in the collected leachates in the Bacanuchi soil; consequently, the mobility of the PTEs present in the acid solution was nullified. Furthermore, this process facilitated the retention of the toxic elements in the Bacanuchi soil.

Conclusions

The retention of PTEs was 100% in the Bacanuchi soil where the natural acid-neutralizing capacity in this soil was associated with calcite. The formation of secondary phases of Fe, among them ferrihydrite, jarosite, and schwertmannite, mainly in Bacanuchi soil, promoted the retention of Al, As, Cd, Cu, Fe, Mn, and Pb (elements analyzed in this work). Results of this work can provide key insights to improve cleanup and conservation strategies in mining sites.

  相似文献   

19.
广东咸酸田土壤硫化学研究   总被引：13，自引：0，他引：13       下载免费PDF全文
黄宇年  陆发熹 《土壤学报》1988,25(2):101-109
本文主要研究广东咸酸田土壤硫的基本化学性质和影响咸酸田发生演化的硫的主要化学过程,探讨土壤硫的化学状况与咸酸田诊断分类和利用改良的关系等。研究结果表明:广东咸酸田土壤含硫量极高,主要是黄铁矿(FeS2)。在咸酸田发生过程中形成一种淡黄色新生体——黄钾铁矾[KFe3(SO4)2(OH)6]。黄铁矿等硫化物的氧化是咸酸田土壤呈强酸性的主要原因。土壤硫的化学状况特别是黄铁矿和黄钾铁矾在剖面上的分布、数量和形态等与咸酸田的发育程度和改良熟化有密切关系。土壤硫的主要来源是红树林对海水中SO42-的吸收利用和富集。土壤硫化学性质对咸酸田的诊断和分类有重要意义。  相似文献   

20.
Sulfur dioxide (SO2), prevalent in the modern urban environment of industrial countries, attacks calcite (CaCO3)in marble. As a result, a gypsum (CaSO4·2H2O) 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 SO2 attack. We report that the anions oxalate (C2O4 -2) and oleate (C17H33COO-) from solutions of their highly soluble alkali salt species areable to replace carbonate (CO3 -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 SO2 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   

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