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1.
《Applied Geochemistry》2001,16(9-10):1003-1019
Stable isotope ratios were used as a tracer for S flow and transformations in an irrigation experiment with 5 different German forest soils. Seventy-five lysimeters constructed from soil cores, 15 from each site, were irrigated over 20 months with SO4-rich artificial canopy throughfall, simulating 3 different S input levels: 35 kg S ha−1 in treatment I, 63 kg S ha−1 in treatment II, and 131 kg S ha−1 in treatment III. The δ34S value of the irrigation SO4 was more than 22‰ higher than those of total S in the untreated soils. Mass and isotope balances for different soil S compounds were used to assess the patterns and mechanisms of S retention in individual soil horizons and their dependence on S deposition levels. Independent of the S deposition level, on average 12±5 kg ha−1 of the applied S were bound organically by the microbial biomass in all soils. Immobilization of irrigation SO4 occurred predominantly in the topsoil horizons with the formation of C-bonded S being more prevalent than the synthesis of organic sulfates. Tracer retention via formation of organic soil S compounds accounted for up to 50% of the irrigation SO4 in treatment I, from 16 to 25% in treatment II, and less than 20% in treatment III. The dominant process of inorganic S retention in the soils appeared to be adsorption of SO4, but precipitation of aluminum hydroxy sulfate minerals constituted a second potential inorganic retention process in some soils. Sulfate adsorption increased with increasing sesquioxide content of the soils and with increasing S deposition rates. In soils with high sesquioxide contents, typically more than 70% of the irrigated S was retained inorganically, whereas in the soil with the lowest sesquioxide content, generally less than 50% of the labeled irrigation S was detected in inorganic form. In the latter soil, the sesquioxide content was not high enough to fully adsorb the elevated SO4 inputs in treatments II and III. Consequently, increased tracer S export with the seepage water SO4 was observed in the experimental variants with elevated SO4 deposition rates. In soils with high sesquioxide contents, the elevated SO4 inputs in treatments II and III were fully retained in the soil horizons in inorganic form during the 20 months of the experiment and thus increased seepage water export of labeled SO4 was not observed. The ability to inorganically retain tracer S in the mineral soil horizons was identified as the major factor regulating the extent of tracer S export with the seepage water at 60 cm depth. The high retention of labeled S in all soils combined with the comparatively low recovery of irrigation SO4 with the seepage water implies that the mean transit time of S in the uppermost 60 cm of the acid forest soils varies between several years and many decades, much longer than previously thought.  相似文献   

2.
Soil interstitial waters and minerals were collected and analyzed to evaluate the influence of acid deposition on Al chemistry in the soil environment of the Green Lakes Valley Front Range, Colorado. The soil solutions were subjected to a series of batch Al experiments followed by computer modeling to separate the labile from the nonlabile Al, and to estimate the activity of Al3+. The Al solubility in the interstitial waters is complex and is controlled by organic solutes, H4SiO4, and pH. The pH and concentrations of SO2−4 do not correlate with Al concentrations. The chemical equilibria of Al are controlled by amorphous aluminosilicate Al(OH)3(1−x) SiO2x. Studies of mineralogy and soil water chemistry provide a useful combination to evaluate and predict the chemical processes of a soil environment.  相似文献   

3.
An evaluation of the response of an Andosol and a Cambisol to acid deposition and weathering rates was studied by using a controlled laboratory leaching experiment. Both soils where derived from mafic parent material, a Histic Andosol from Western Iceland and a Cambisol from North East Scotland. De-ionized water and water acidified with H2SO4 (pH 3) was leached through reconstructed soil columns to simulate 34 years of precipitation.Acidic input increased cation leaching and weathering rates in both soil types and reduced pH levels. The Andosol proved generally to have higher weathering rates, leaching potential, ion exchange and acid-buffering capacity as well as maintaining a relatively steady pH despite intense acidic input. This was due to differences in parent material and mineral composition. The Andosol was developed from basaltic volcanic tephra, which had higher dissolution rates due to its amorphous mineral structures. The Cambisol was developed from gabbro with more stable mineral structures.  相似文献   

4.
Soils overlying two porphyry Cu deposits (Spence, Gaby Sur) and the Pampa del Tamarugal, Atacama Desert, Northern Chile were collected in order to investigate the extent to which saline groundwaters influence “soil” chemistry in regions with thick Miocene and younger sediment cover. Soil carbonate (calcite) was analyzed for C and O isotopes and pedogenic gypsum for S isotopes. Soil calcite is present in all soils at the Spence deposit, but increases volumetrically above two fracture zones that cut the Miocene gravels, including gravels that overlie the deposit. The C isotope composition of carbonate from the soils overlying fracture zones is indistinguishable from pedogenic carbonate elsewhere at the Spence deposit; all δ13CVPDB values fall within a narrow range (1.40–4.23‰), consistent with the carbonate having formed in equilibrium with atmospheric CO2. However, δ18OVPDB for carbonate over both fracture zones is statistically different from carbonate elsewhere (average δ18OVPDB = 0.82‰ vs. −2.23‰, respectively), suggesting involvement of groundwater in their formation. The composition of soils at the Tamarugal anomaly has been most strongly affected by earthquake-related surface flooding and evaporation of groundwater; δ13CVPDB values (−4.28‰ to −2.04‰) are interpreted to be a mixture of dissolved inorganic C (DIC) from groundwater and atmospheric CO2. At the Spence deposit, soils only rarely contain sufficient SO4 for S isotope analysis; the SO4-bearing soils occur only above the fracture zones in the gravel. Results are uniform (3.7–4.9‰ δ34SCDT), which is near the middle of the range for SO4 in groundwater (0.9–7.3‰). Sulfur in soils at the Gaby Sur deposit (3.8–6.1‰ δ34SCDT) is dominated by gypsum, which primarily occurs on the flanks and tops of hills, suggesting deposition from SO4-rich fogs. Sulfate in Gaby Sur deposit gypsum is possibly derived by condensation of airborne SO4 from volcanic SO2 from the nearby Andes. At the Gaby Sur deposit and Tamarugal anomaly, pedogenic stable isotopes cannot distinguish between S from porphyry or redeposited SO4 from interior salars.The three sites studied have had different histories of salt accumulation and display variable influence of groundwater, which is interpreted to have been forced to the surface during earthquakes. The clear accumulation of salts associated with fractures at the Spence deposit, and shifts in the isotopic composition of carbonate and sulfate in the fractures despite clear evidence of relatively recent removal of salts indicates that transfer from groundwater is an ongoing process. The interpretation that groundwaters can influence the isotopic composition of pedogenic calcrete and gypsum has important implications for previous studies that have not considered this mechanism.  相似文献   

5.
The Cu hydroxy mineral, atacamite, is commonly associated with saline environments and is generally thought to dissolve rapidly in the presence of fresh water. A Cu contaminated soil from the arid Namaqualand region, South Africa, shows atacamite as the dominant Cu containing mineral. The stability of the Cu phase in this soil was determined through equilibrium and leaching studies using both deionised water (DI) and a concentrated (0.5 M) NaCl solution. Initially a high concentration of exchangeable Cu was released from the soils leached with NaCl. Continued leaching with NaCl resulted in a substantial decrease in Cu release as atacamite equilibria started to control dissolved Cu. This suggests that an initial spike of Cu laden water will leach from the soils at the onset of a large rainfall event. Further additions of water will result in a lower but sustained release of Cu from the soil. The Cu contaminated soils are exposed to acidic sulphate leachate thus the dissolution kinetics of synthetic atacamite in the acidic range (pH 5.5–4.0) was determined in both NaCl and DI solutions. The kinetic data showed that atacamite dissolution rates are significantly higher in DI than in NaCl but the rates converge at pH 4. In comparison to common acid soluble minerals, atacamite displays a moderate dissolution rate (10−9.55–10−7.14 mol m−2 s−1) within the acid range (pH 5.5–4.0). The atacamite dissolution reaction order with respect to pH is 1.3 and 1.6 in DI and NaCl solutions, respectively, suggesting that dissolution rates of atacamite are highly pH dependent in the acid range. The type of acid used to lower the pH had no effect on the reaction kinetics, with HNO3 and H2SO4 resulting in comparable dissolution rates of atacamite at pH 4.5.  相似文献   

6.
《Applied Geochemistry》2004,19(11):1837-1853
Iron monosulfide formation and oxidation processes were studied in the extensively drained acid sulfate soil environment of the Tweed River floodplain in eastern Australia. Porewater profiles of pH, Eh, SO42−, Fe2+, Fe3+, Cl−, HCO3−, and metals (Cd, Co, Cr, Cu, Ni, Pb and Zn) were obtained using in situ dialysis membrane samplers (`peepers'). Concentrations of acid volatile S (AVS), pyrite, total S, reactive Fe, total and organic C, simultaneously extracted metals (SEMs) and total elemental composition by X-ray fluorescence, were determined on sediment samples. The oxidation of pyrite in the surrounding landscape provides a source of acidity, Fe, Al, SO4 and metals, which are exported into the drainage system where they accumulate in the sediments and porewaters. Negative porewater concentration gradients of SO42− and Fe2+, and large AVS concentrations in the sediments, indicate Fe monosulfides form rapidly under reducing conditions and consume acidity and metals. Oxidation of the sediments during previous drought episodes has resulted in the conversion of monosulfides and pyrite to oxidised Fe minerals and the release of acidity, SO42−, Fe3+, and metals to the surface waters. These formation and oxidation cycles show that Fe monosulfides play an important role in controlling water quality in the drainage system.  相似文献   

7.
The impact of 60 a of SO2 emissions from a Ni–Cu plant in the Kola Peninsula (Russia) on soil S contents was assessed in podzols under pine forests. Sulphate desorption and the possible delay of acidification reversal was investigated, because the plant will be reconstructed in 2006 with an expected emission reduction of 90%. Sites were sampled along a pollution gradient in the prevailing wind direction from 1 to 66 km. The investigated podzols stored S mostly in the organic form. The concentrations of total and organic S in soil organic horizons tended to be higher near the smelter but were only weakly correlated with S deposition. No relationship between distance to smelter and S contents was found for the mineral horizons. Sulphate content and desorption behavior were highly variable due to natural variations of texture and extractable Al and Fe contents of the soils. The lack of a clear strong trend with distance from the smelter except in the organic layer indicated that long range transport and diffuse input of SO4 played a major role rather than point source impact. It was concluded that biological turnover is most likely the regulating process in these soils and thus low to medium release of SO4 is expected under decreasing deposition scenarios because organic S was the dominant fraction of total S in all soils.  相似文献   

8.
In the area surrounding the El Teniente giant porphyry copper deposit, eight soil sites were sampled at three depth levels in the summer 2004. The sites were selected for their theoretical potential of being influenced by past SO2 emissions from the smelter and/or seepage from a now idle tailings impoundment. The soil mineralogy, grain size distribution, total organic matter contents, major element composition, cation exchange capacity, and Cu, Mo, Pb, Zn, As and SO4 2− concentrations were determined for all samples after nitric acid extraction and separate leaches by ammonium acetate (pH 7) and sodium acetate (pH 5). For water rinses, only Cu could be determined with the analytical set-up used. Cu and SO4 2− enrichment in topsoils was found at six sites either downwind from the smelter or within the combined influence of the smelter and the tailings impoundment. Both elements were released partially by ammonium and sodium acetate extractions. Due to the scarce background trace element concentrations of soil and rock outside the immediate mine area, assessment of trace element mobility for Mo, Zn, Pb and As was difficult. Arsenic was found to be concentrated in soil horizons with high smectite and/or organic matter contents. Mo appears to be linked to the presence of windblown tailings sediment in the soils. Mobilization of Mo, Zn, and As for the acetate extractions was minimal or below the detection limits for the AAS technique used. The presence of windblown tailings is considered to be an additional impact on the soils in the foothills of the El Teniente compound, together with the potential of acidity surges and Cu mobilization in topsoils after rainfalls. Two sites located at the western limit of the former SO2 saturated zone with strongly zeolitized soils and underlying rock did not show any Cu or SO4 2− enrichment in the topsoils, and remaining total trace element concentrations were below the known regional background levels.  相似文献   

9.
Salt-rich soft soils have not only general characteristics of common soft soils, but also contain high contents of Mg2+, Cl?, and SO42?, which have negative effects on deep mixing method using cement to treat soft soils. Laboratory and field tests were conducted to investigate the effects of changing cement incorporating ratio, water content, cement mixing ratio, and contents of Mg2+, Cl?, and SO42? on the unconfined compressive strength of the salt-rich soil–cement. The microstructure of soil–cement and the mechanism for the strength change of salt-rich soil–cement were investigated using X-ray diffraction, scanning electronic microscopy (SEM), and backscattered diffraction technology. It was found that an increase of cement incorporating ratio enhanced the strength of soil–cement but reduced its strength when water is added. Different amounts of Mg2+, Cl?, and SO42? not only caused the difference in the microstructures of salt-rich soil–cement but also influenced the soil–cement strength.  相似文献   

10.
With the increasing application of germanium (Ge) elements in modern industry, military and medical health industries, especially with the growing demand for Ge-rich agricultural products, the study of Ge-rich soil has become particularly important, but the enrichment pattern and control factors of Ge-rich soil are still not well understood due to the high dispersion and high migration of Ge-rich soil. In this paper, 495 surface soil (0–20 cm) and 149 deep soil (150–200 cm) samples were collected from the northern foothills of Dabie Mountain using a double-layer grid layout, and the spatial distribution and enrichment characteristics of Ge were studied by high-resolution method, and the controlling factors affecting the distribution of Ge-rich soil was analyzed by geo-statistics and spatial analogy. The results show an average Ge content of 1.34 mg/kg for the surface and 1.36 mg/kg for the deep soil. In the assessment grade classification of surface and deep soil for Ge, the abundant and sub-abundant grades account for 37.97% and 31.70%, respectively, covering 752 km2 and 634 km2. Surface Ge-rich regions are distributed in concentrated strips in the north-central part of the studied region, and there is no clear pattern in the spatial distribution of deep soils. In the areas under study, such as Fenlukou, Dingji, and Jiangjiadian, the surface soil is very rich in Ge and has a high enrichment factor, which is valuable for agricultural development. In surface soils, river deposits and shallow metamorphic rock parent materials have the highest content of Ge, while in deep soils, the highest content has been found in the parent material of moderately acidic rock. Both surface and deep soils have the highest Ge content in purple paddy soils and plain areas. The source of Ge in the soils of the study area is most influenced by the lithology of the soil-forming parent material, while the distribution of Ge in the surface soils is jointly influenced by pH, SiO2, TFe2O3, and Al2O3 in the soil. This study has implications for understanding the enrichment pattern of Ge in soil and its controlling factors as well as for the development of Ge-rich agricultural products.  相似文献   

11.
Unsafe lead (Pb) concentrations in leafy vegetables raised in urban and peri-urban agricultural production systems have been reported across cities in Northern Nigeria, even though Pb concentrations in soils are within regulatory safe levels. This study examined the soil enrichment, adsorption and chemical species of Pb in urban garden fields irrigated with untreated wastewater at three industrial locations in Kano, northern Nigeria. Total Pb in the soil profiles ranged from 9 to 91 mg kg?1 and decreased rapidly from the surface to the subsurface layer, but attaining nearly constant concentration at depth ≥1.2 m in the profiles. The potentially labile Pb maintained fairly constant concentration with depth up to 0.9 m, but decreased fairly rapidly with depth thereafter. There was a significant Pb enrichment of the soils, extending up to 30–60 cm depth in the soil profiles. The adsorption of Pb by the soils increased drastically with pH, and attained maximum adsorption at pH ≥ 7.0 in the surface layer, and at pH ≥ 6 in the subsurface layer. The surface soils adsorbed between 85 and 97 % of added Pb at pH ≤ 5. Free Pb2+ activities in soil solution accounted for between 46 and 87 % at pH 5–7 of total dissolved Pb (PbT). The quantifiable chemical species of Pb in solution consisted mainly of PbOH+, PbSO 4 · , PbCl+ and PbOH 2 · which accounted for between 0.9 and 26 % of PbT in soil solution at pH ≥ 5.0, but declining to between 0.1 and 2.1 % at pH ≥ 7.5. There was no apparent equilibrium between Pb2+ activities and known Pb-compounds in the soils. It was concluded from the data that reports of excess Pb concentrations in leafy vegetables raised in these soils are consistent with high free Pb2+ activities maintained in soil solution by these predominantly sandy-textured soils.  相似文献   

12.
《Chemical Geology》2006,225(3-4):244-255
Thermodynamic properties of the BaSO4–BaCrO4 hashemite solid solution were calculated using molecular principles. Force-field potentials and physical properties of the end member BaCrO4 were derived using the program package GULP. Subsequently, anion–anion (SO42−–CrO42−, SO42−–SO42−, CrO42−–CrO42−) interaction energies were fitted to a number of random and ordered anion distributions, which were energy-optimized using these empirical potentials. With these interaction energies, diagrams for the enthalpy and free energy of mixing could be computed for the entire range of the hashemite solid solution between the BaSO4 and BaCrO4 end members and for a number of annealing temperatures. These thermodynamic data show that the solid solution is close to ideal and ordering is not observed at low temperatures for any composition. However, according to our calculations, exsolution may occur at the nanoscale due to a slight tendency of sulfate–chromate avoidance.Growth experiments of chromate-rich hashemite on barite using atomic force experiments (AFM) in a fluid cell indicate that hashemite does not show the same degree of growth anisotropy as barite. In the case of barite, this anisotropy leads to a structural self-inhibition of spiral growth. In contrast, hashemite exhibits a spatially more extended spiral growth, which can contribute more to overall volume growth than in the case of barite. This finding is confirmed by a higher growth rate of hashemite than of barite in macroscopic batch-reactor and flow-through experiments.Molecular simulations indicate that there is a less pronounced step energy difference between bounding steps of growth islands for hashemite than for barite, which may partially explain the difference in growth anisotropy of the two minerals. Differences in adsorption energies to the corners of growth islands, which are the limiting steps of growth, do not seem to be high enough to explain differences in growth anisotropies. Therefore, kinetic effects or differences in the interfacial free energies of the two minerals may serve as an additional explanation for differences in the growth behavior.  相似文献   

13.
《Applied Geochemistry》2004,19(3):343-358
Ion-exchange batch experiments were run on Cretaceous (Magothy aquifer) clay cores from a nearshore borehole and an inland borehole on Long Island, NY, to determine the origin of high SO42− concentrations in ground water. Desorption batch tests indicate that the amounts of SO42− released from the core samples are much greater (980–4700 μg/g of sediment) than the concentrations in ground-water samples. The locally high SO42− concentrations in pore water extracted from cores are consistent with the overall increase in SO42− concentrations in ground water along Magothy flow paths. Results of the sorption batch tests indicate that SO42− sorption onto clay is small but significant (40–120 μg/g of sediment) in the low-pH (<5) pore water of clays, and a significant part of the SO42− in Magothy pore water may result from the oxidation of FeS2 by dissolved Fe(III). The acidic conditions that result from FeS2 oxidation in acidic pore water should result in greater sorption of SO42− and other anions onto protonated surfaces than in neutral-pH pore water. Comparison of the amounts of Cl− released from a clay core sample in desorption batch tests (4 μg/g of sediment) with the amounts of Cl− sorbed to the same clay in sorption tests (3.7–5 μg/g) indicates that the high concentrations of Cl− in pore water did not originate from connate seawater but were desorbed from sediment that was previously in contact with seawater. Furthermore, a hypothetical seawater transgression in the past is consistent with the observed pattern of sorbed cation complexes in the Magothy cores and could be a significant source of high SO42− concentrations in Magothy ground water.  相似文献   

14.
Deposition in the New Jersey Pinelands was very acidic (pH=4.17) and contained high levels of SO2 −2 based on bulk deposition measurementsfrom July 1984–July 1986. Streamwater over the same interval in undisturbed watersheds was less acidic (pH =4.52) and had proportionately less SO4 −2. A preliminary alkalinity budget for undisturbed watersheds suggested that SO4 −2 retention within Pinelands watersheds accounted for a large portion of the total alkalinity generated and thereby lessened the impact of acidic deposition on surface waters. The only process capable of explaining the retention of SO4 −2 was microbial sulfate reduction in the extensive wetlands surrounding Pinelands streams which occurred at high rates.  相似文献   

15.
Reoxidation of S stored in lowlands after summer droughts has been reported to be responsible for the excess SO4 export observed in many catchments in south central Ontario. Stable S isotopes can be used to identify the source of SO4 export in stream water, and are particularly well suited to evaluating zones of dissimilatory SO4 reduction (DSR) and the contribution of oxidation of reduced S species to stream SO4. The Plastic Lake-1 (PC1) stream drains an upland coniferous forest and then passes through a Sphagnum-dominated swamp before discharging to Plastic Lake. Measurements of SO4 fluxes and isotope ratios were used to determine the source of net SO4 export and the contribution of redox processes to S retention and export in the upland and wetland, respectively. Mass balance budgets for the years 1999/00 and 2000/01, which had comparatively wet summers, indicated that the upland part of the catchment consistently exported SO4 in excess of bulk deposition inputs. In contrast, mass budget calculations for the swamp indicated a net retention of 3 and 2 g S-SO4/m2 of wetland area, in 1999/00 and 2000/01 respectively. Higher δ34SO4 ratios and lower SO4 concentrations in the swamp outflow (average +8.6 ± 2.6‰; 1.5 ± 0.6 mg S-SO4/L) compared to the inflow draining the upland (+5.4 ± 0.7‰; 2.4 ± 0.3 mg S-SO4/L) indicated that DSR was at least partly responsible for net SO4 retention in the swamp. Isotope values in upland stream water (+5.7 ± 0.7‰) were only slightly higher than values in bulk deposition (average +5.1 ± 0.6‰) and soil leachate (+4.4 ± 0.4‰) over the 2-year period of study. Similar δ34SO4 values in upland stream water compared to deposition and soil leachate, despite substantial variations in water table height in the streambed (92 cm), suggest that reoxidation of reduced sulphides is not an important contributor to SO4 export from the upland. Rather, net SO4 export from the upland subcatchment is likely due to net release from upland soil, and slight differences in δ34SO4 between bulk deposition and soil leachate are consistent with SO4 release from organic S forms.  相似文献   

16.
Soil salinization is an environmental problem having significant impacts on the soil–water–plant system. This problem is more frequent in coastal areas due to seawater intrusion into the land. Assessing the soil salinization is a critical issue for the agricultural areas situated in the Mediterranean basin. This paper examines the deterioration of soil quality in the cultivated land of a Mediterranean site (Agoulinitsa district—West Greece). Soil samples were collected in both pre-irrigation and post-irrigation seasons. Electrical conductivity (EC), pH and the ions Br?, Ca2+, Cl?, F?, K+, Li+, Mg2+, Na+, NH4 +, NO2 ?, NO3 ?, PO4 3? and SO4 2? were determined by the 1:2 (soil/water ratio on weight basis) method. The salts which were present in both seasons in the soils of the area studied are KCl, MgCl2, NaCl, CaSO4 and K2SO4. The wide spatiotemporal variation of EC in the cultivated land in both seasons demonstrates that soil salinity is controlled mainly by seawater intrusion and anthropogenic factors such as the application of salt-rich water which is directly pumped from the drainage ditches. Seawater intrusion provides the affected soil with elevated contents of Ca2+, Cl?, K+, Mg2+, Na+ and SO4 2?. Classification of the soils by using criteria given by the literature is discussed. Practices to prevent, or at least ameliorate, salinization in the cultivated land of Agoulinitsa district are proposed.  相似文献   

17.
文章对西宁第四纪黄土-古土壤序列L9以来的黄土和古土壤层进行了土壤化学分析,揭示出剖面中含有大量的可溶盐。古土壤层中的可溶盐含量远高于黄土层,且二者所含可溶盐类型的相对比例存在明显差异。黄土层中Na2CO3和NaHCO3的相对比例较高,表现出更多的碱化特性,而古土壤中含有较多的NaCl和Na2SO4,表现出更多的盐化特性。从剖面所处的地貌-水文条件及土壤微形态特征来看,这些可溶盐主要来自大气降尘。研究揭示,约900ka以来,该区周边地区一直存在较多的干盐湖,是形成粉尘物质的重要源区之一,且间冰期粉尘比冰期粉尘可溶盐含量高得多。这些粉尘中含有较多的、包括对气候有影响的硫酸盐在内的可溶盐类。  相似文献   

18.
《Applied Geochemistry》2001,16(5):503-511
The use of adsorption data from single sorbate systems to model metal adsorption in SO4-rich waters, such as acid mine drainage, can lead to inaccurate predictions of metal speciation. The adsorption of Cu and Zn on ferrihydrite, for example, is enhanced at low pH values in the presence of SO4. This effect can only be accurately modeled using the diffuse layer model and surface complexation theory if ternary surface complexes, ≡FeOHCuSO4 or ≡FeOHZnSO4, are taken into consideration. Intrinsic adsorption constants for the formation of these ternary complexes on ferrihydrite have been derived from experimental data. When included in the model, Cu and Zn adsorption in the presence of SO4 is accurately predicted for a wide range of metal, ferrihydrite and SO4 concentrations. Adsorption of Cu and Zn onto the SO4-rich Fe oxyhydroxide, schwertmannite, could also be accurately predicted and is indistinguishable from adsorption onto ferrihydrite in the presence of high solution SO4 concentrations (e.g. 0.01 mol kg−1 SO4).  相似文献   

19.
Depth distributions of bacterial respiration of O2, NO3− and SO42− were compared with geochemical data for Mn, Fe and S in coastal sediments from water depths between 26 and 520 m. As water depth increased, the zone of SO42− respiration was found deeper in the sediment and was eventually separated from the surface-located activity of O2 and NO2− respiration. At the deepest station additional SO42− reduction activity was observed in small, detrital aggregates on the sediment surface. Dissolved Mn2+ and Fe2+ appeared between the O2- plus NO3−-containing surface layer and the H2S-plus FeS-containing sediment below. This was a result of Mn and Fe reductions coupled to either the oxidation of sulfide or the mineralization of organic matter. Tracer experiments showed that both FeS, FeS2 and S0 were important radiolabelled products of sulfate respiration in this intermediate zone. In the same zone, the overall degradation of organic matter seemed to be underestimated by the assay of SO2-4 respiration and additional mineralization by Mn and Fe reductions was likely.  相似文献   

20.
The study was carried out on the Sulejów dam reservoir (Central Poland). Water and sediment samples were collected between February and October 2006. Sulfur compounds in the sediment were chemically extracted and subjected to isotopic analysis.Large variability of SO42− concentration in the water column (from 10.3 to 36.2 mg/dm3) and the isotopic composition of sulfur (δ34S from 2.1 to 5.4‰) was observed. The main identified sources of SO42− were watercourses, surface runoff, and phosphorus fertilizers.Both oxidized sulfur species (SO42−) and its reduced forms were found in sediments. Particular sulfur forms were characterized by large variations in both, concentrations and the isotopic composition of sulfur. SO42− in the sediment and in the water column had different genesis. Bacterial oxidation of organic sulfur and its binding in SO42− were observed in the sediment. Under reducing conditions, oxidized and organic sulfur is converted to H2S which reacted with Fe or other metallic ions leading to metal sulfide precipitation. Monosulfides were shown to have a very low concentration, ranging up to 0.07 mg/g of sediment. The transformation of elemental sulfur from sulfides through their chemical oxidation occurred in the sediment.  相似文献   

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