The hydrogen isotope fractionation between kaolinite and water

Hydrogen isotope fractionation factors between kaolinite and water were determined at temperatures between 200° and 352°C. Five-gram samples of kaolinite were heated in contact with 8-mg samples of water in sealed glass reaction tubes. Under these conditions the approach to equilibrium with time will be reflected primarily in the change of the δ D in the water. Also the δ D of the hydrogen in the kaolinite will be relatively constant, subject to minor corrections. About seventy sealed vessels were heated for various times at various temperatures. During four months of heating, ～ 25% of kaolinite hydrogen exchanged with the water at 200°C, whereas 100% exchanged at 352°C. The α-values were estimated assuming equilibrium between exchanged kaolinite and water. The 10³lnα-values are estimated to be ?20, ?15, ?6 and +7 for 352°, 300°, 250° and 200°C, respectively, which are in approximate agreement with reported values previously determined at 400°C using conventional methods as well as those estimated from kaolinite in hydrothermally active systems. The curve representing the relationship between the hydrogen isotope fractionation factor for the kaolinite-water system and temperatures between 400° and 25°C is not monotonic but rather has a maximum at 200°C.     

A study on the adsorption characteristics of cadmium and zinc onto acidic and alkaline soils

The adsorption of cadmium (Cd) and zinc (Zn) with similar chemical properties is examined onto three soil samples: one is alkaline and the others are acidic. The distribution coefficient (K _d) and the Freundlich constant (K _F) for Zn are slightly higher than those for Cd, implying that the adsorption affinity of Zn is a little greater and less mobile. However, Cd and Zn usually show comparable results in the kinetic, isotherm, and envelope experiments. The adsorption of the heavy metals is relatively rapid and the reaction is almost completed within 15 min. The kinetics for both Cd and Zn are very well explained by the parabolic diffusion model. The maximum adsorption of the heavy metals is obtained at high pH, high temperature, and low ionic strength. The adsorption capacity on the alkaline soil is more significantly affected by the temperature as compared to the acidic soil. It is found that the adsorption affinity of the two heavy metals is mainly affected by the soil properties, such as pH, pH_PZC, organic matter, and total carbon. It is also confirmed that the chemical properties of the heavy metals are important factors in their adsorption onto soil. The adsorption isotherms of Cd and Zn are well described in both Freundlich and Langmuir models at the usual pH (soil pH). Under acidic and alkaline pHs, however, only the Freundlich model describes the adsorption of both heavy metals satisfactorily.     

Formation of solid bituminous matter in pegmatites: Constraints from experimentally formed organic matter on microporous silicate minerals

The formation of solid bituminous matter (SBM) on surfaces of microporous silicates was experimentally studied at pressure and temperature conditions typical of late-stage magmatic and hydrothermal processes. Aliquots of microporous silicate minerals (zorite and kuzmenkoite-Mn, Lovozero Alkaline Massif, Kola Peninsula, Russia) were exposed to solid or liquid organic carbon sources (natural brown coal and liquid 1-hexene for synthesis purposes) in a 0.1 M NaCl-solution for 7 days, at constant pressure (50 MPa), and at three individual temperatures (200, 275, and 300 °C). No thermal decomposition of the solid organic sources happened at 200 °C and only a thin film of brown coal derivatives on the silicates’ surfaces and no formation of SBM were observed at 275 °C and 300 °C. But solid bituminous matter on the surfaces of both microporous silicates were detected in experiments with liquid 1-hexene as organic carbon source and at temperatures of 275 °C and 300 °C with a more pronounced formation of SBM at 300 °C compared to 275 °C. The aromatic and aliphatic hydrocarbons, as well as alcoholic compounds of the experimentally produced SBM are similar, if not even partly identical, with natural SBM occurrences of the Khibiny and Lovozero Massifs, Kola Peninsula, Russia, and from the Viitaniemi granitic pegmatite, Finland, as shown by FT-IR and ¹H NMR spectroscopy. This strengthens the hypothesis of formation of natural solid bituminous matter by catalytic reactions between microporous Ti-, Nb- and Zr-silicates and hydrocarbons at postmagmatic hydrothermal conditions.     

Effects of thermal energy storage on shallow aerobic aquifer systems: temporary increase in abundance and activity of sulfate-reducing and sulfur-oxidizing bacteria

Aquifer thermal energy storage may result in increases in the groundwater temperature up to 70 °C and more. This may lead to geochemical and microbiological alterations in the aquifer. To study the temperature effects on the indigenous microbial community composition, sediment column experiments at four different temperatures were carried out and the effluents were characterized geochemically and microbiologically. After an equilibrium phase at groundwater temperature of 10 °C for 136 days, one column was kept at 10 °C as a reference and the others were heated to 25, 40 and 70 °C. Genetic fingerprinting and quantitative PCR revealed a change in the bacterial community composition and abundance due to the temperature increase. While at 25 °C only slight changes in geochemical composition and gene copy numbers for bacteria were observed, increasing concentrations of total organic carbon in the 40 °C column were followed by a strong increase in bacterial abundance. Thermophilic bacteria became dominant at 70 °C. Temporary sulfate reduction took place at 40 and 70 °C and this correlated with an increased abundance of sulfate-reducing bacteria (SRB). Furthermore, a coexistence of SRB and sulfur-oxidizing bacteria (SOB) at all temperatures indicated an interaction of these physiological groups in the sediments. The results show that increased temperatures led to significant shifts in the microbial community composition due to the altered availability of electron donors and acceptors. The interplay of SRB and SOB in sedimentary biofilms facilitated closed sulfur cycling and diminished harmful sulfur species.     

Short-term greenhouse emission lowering effect of biochars from solid organic municipal wastes

Qatar economy has been growing rapidly during the last two decades during which waste generation and greenhouse gas emissions increased exponentially making them among the main environmental challenges facing the country. Production of biochar from municipal solid organic wastes (SOWs) for soil application may offer a sustainable waste management strategy while improving crop productivity and sequestering carbon. This study was conducted to (1) investigate the physicochemical parameters of biochars for SOW, (2) select the best-performing biochars for soil fertility, and (3) evaluate the potential benefits of these biochars in lowering greenhouse gases (GHGs) during soil incubation. Biochars were produced from SOW at pyrolysis temperatures of 300–750 °C and residence times of 2–6 h. Biochars were characterized before use in soil incubation to select the best-performing treatment and evaluation of potential GHG-lowering effect using CO₂ emission as proxy. Here, soil–biochar mixtures (0–2%w/w) were incubated in greenhouse settings for 120 days at 10% soil moisture. Soil properties, such as pH, EC, TC, and WHC, were significantly improved after soil amendment with biochar. Two biochars produced from mixed materials at 300–500 °C for 2 h and used at 0.5–1% application rate performed the best in enhancing soil fertility parameters. A significant decrease in CO₂ emission was observed in vials with soil–biochar mixtures, especially for biochars produced at 500 °C compared the corresponding raw materials which exhibited an exponential increase in the CO₂ emission. Hence, application of biochar to agricultural soils could be beneficial for simultaneously improving soil fertility/crop productivity while sequestering carbon, thereby reducing anthropogenic emissions of GHGs.     

Release of lead from Pb-clinoptilolite: managing the fate of an exhausted exchanger

The selectivity of clinoptilolite toward Pb²⁺ has stimulated many studies aimed to evaluate the metal uptake. Conversely, the management of a Pb-bearing clinoptilolite has not received the same attention, although it can release a harmful metal. This work aims to evaluate the possibility to control, through thermal treatments, the release of lead from a Pb-clinoptilolite, prepared to simulate the condition of highest dangerousness of an exhausted exchanger. A zeolite-rich rock from Sardinia (Italy) has been processed, obtaining a powder with almost 90 % (wt.) of clinoptilolite. This material has been initially Na- and then Pb-exchanged, reaching a Pb²⁺ content of 2.28 meq/g. The lead release has been tested before and after 2-h heating at eight different temperatures from 200 to 900 °C. The unheated material releases 64 % of the lead. Heating weakly affects lead release up to 400 °C (54 %), but higher temperatures determine an abrupt reduction from 44 % at 500 °C to 1 % at 700 °C, when the zeolite breakdown occurs. At 800 °C the nucleation of Pb-feldspar and silica polymorphs begins. Basically, the material heated at 900 °C does not release lead (0.03 %), because the metal is trapped in the lead feldspar, whose content attains 42 % (wt.). This solid-state transformation does not involve the emission of lead vapors, another significant environmental aspect.     

A 40 ka record of temperature and permafrost conditions in northwestern Europe from noble gases in the Ledo‐Paniselian Aquifer (Belgium)

The Ledo‐Paniselian Aquifer in Belgium offers unique opportunities to study periglacial groundwater recharge during the Last Glacial Maximum (LGM), as it was located close to the southern boundary of the ice sheets at that time. Groundwater residence times determined by ¹⁴C and ⁴He reveal a sequence of Holocene and Pleistocene groundwaters and a gap between about 14 and 21 ka, indicating permafrost conditions which inhibited groundwater recharge. In this paper, a dataset of noble gas measurements is used to study the climatic evolution of the region. The derived recharge temperatures indicate that soil temperatures in the periods just before and after the recharge gap were only slightly above freezing, supporting the hypothesis that permafrost caused the recharge gap. The inferred glacial cooling of 9.5°C is the largest found so far by the noble gas method. Yet, compared to other palaeoclimate reconstructions for the region, recharge temperatures deduced from noble gases for the cold periods tend to be rather high. Most likely, this is due to soil temperatures being several degrees higher than air temperatures during periods with extended snow cover. Thus the noble‐gas‐derived glacial cooling of 9.5°C is only a lower limit of the maximum cooling during the LGM. Some samples younger than the recharge gap are affected by degassing, possibly related to gas production during recharge in part of the recharge area, especially during times of melting permafrost. The findings of this study, such as the occurrence of a recharge gap and degassing related to permafrost and its melting, are significant for groundwater dynamics and geochemistry in periglacial areas. Copyright © 2010 John Wiley & Sons, Ltd.     

Chemical exchange during hydrothermal alteration of basalt by seawater—II. Experimental results for Fe,Mn, and sulfur species

Fresh mid-ocean ridge basalts of varying crystallinity and an andesite were reacted with seawater and with a Na-K-Ca-Cl solution at 200–500°C and 500–1000 bar in sealed gold capsules. $\text{Water}\text{rock}$ mass ratios of one to three were used and durations ranged from two to twenty months. The concentrations of Fe, Mn, and reduced and oxidized sulfur species in solution reached steady state in most of the experiments at 400–500°C, but not in those at 200–300°. The concentrations of Fe and Mn were a few ppm at 200–300° and increased greatly with temperature between 300 and 500°. The low values at 200–300° are probably related to the uptake of Fe and Mn by smectite at the in situ pH, which was slightly acid at 200° and slightly alkaline at 300°. The quench pH values decreased with increasing temperature above 300°. The only reliable data for the concentration of Zn in solution were obtained at 400°, where values 1–2 ppm were found. Copper was extensively leached from basalt and andesite and was deposited as part of a Cu-Au alloy in the capsule walls or, in some experiments, as chalcopyrite.Reduced sulfur was readily leached from basalt into solution, and was also produced by the reduction of seawater sulfate by ferrous iron derived from the basalts. The proportion of seawater sulfate which was reduced in the experiments with a $\text{water}\text{rock}$ ratio of one varied from 5–10% at 300°C to > 95% at 500°. The rate of sulfate reduction depended on the run temperature, on the crystallinity and initial sulfur content of the rocks used as starting materials, and on the $\text{water}\text{rock}$ ratio. The final concentration of reduced sulfur in solution increased greatly with temperature, and generally exceeded that of Fe on a molal basis.The oxide-sulfide assemblages produced in the experiments resemble those in the basalt-seawater geothermal system at Reykjanes, Iceland, and in hydrothermally altered basalts and gabbros from the oceanic crust; they include pyrite, pyrrhotite. chalcopyrite, hematite, and probably magnetite. The particular assemblage varied systematically with the temperature, rock type, and crystallinity of each run. Anhydrite precipitated in all experiments with seawater, at all temperatures from 200–500°C. However, its persistence to the end of the runs was apparently metastable, as it should have reacted with the final solutions to produce pyrite or pyrrhotite.     

Soil temperatures in four metropolitan cities of Korea from 1960 to 2010: implications for climate change and urban heat

This study was conducted to reveal the trends of the air temperature and soil temperature for 51 years (1960–2010) and their relationship in four of Korea’s largest metropolitan cities (Seoul, Incheon, Busan and Daejeon). Also, the trends of the air and soil temperatures between the studied metropolitan cities and a rural area (Chupungryong) were compared to examine the effect of urban heat. Among the metropolitan cities, the long-term mean soil temperatures (depth 0.0, 0.5, 1.0, 1.5, 3.0, 5.0 m) were lowest (13.34–14.80 °C) in Seoul and highest (16.24–16.54 °C) in Busan, which is mainly the effect of the latitude. The soil temperature exponentially increased with depth in the three cities except for Busan and was closely related to the air temperature. The soil temperatures responded well to the air temperature change (maximum correlation coefficients 0.88–0.98) but this response was slightly delayed with depth. The air and soil temperatures increased at the rates of 0.24–0.40 and 0.11–0.73 °C/decade, respectively, for the period. The increasing rate of the soil temperature was the largest in Daejeon as 0.39–0.73 °C/decade, which was almost 2–4 times greater than those of the other cities (0.11–0.40 °C/decade), and it rose with depth. The increase of the soil temperature was coincident with the increase of the air temperature, which indicates that the soil temperature was largely affected by the increasing of the air temperature. In contrast, the increase in air temperature in Chupungryong (0.06 °C/decade) was significantly lower than in the metropolitan cities. In addition, the increase of the soil temperature in the rural area (0.13 °C/decade) was also much lower than that in the inland cities (0.20–0.27 °C/decade) while it showed no substantial difference from that in the coastal cities (0.11–0.15 °C/decade). Therefore, it is inferred that the soil temperature of the metropolitan cities increased with the increase of the air temperature due to global warming as well as the anthropogenic urban heat.     

Effect of hydrocarbon volatility and adsorption on source-rock pyrolysis

Petroleum source-rock evaluations by pyrolysis are based on the concept that free hydrocarbons in rock samples are volatilized below 300°C while hydrocarbons cracked from kerogen come off at higher temperatures. The pyrolysis of pure hydrocarbons with different mineral matrices shows that free hydrocarbons containing 16 or more carbon atoms may not be evolved eblow 300°C, but at varying higher temperatures. The extent to which this occurs depends on the hydrocarbon volatility, the mineral matrix and the pyrolysis instrument design. Source-rock parameters which use the P₁ (S₁) peak may be not be reproducible between instruments if the rock contains appreciable amounts of high molecular weight hydrocarbons.     

High temperature supercritical carbon dioxide extractions of geological samples: effects and contributions from the sample matrix

Stepwise high temperature supercritical fluid extraction (HT–SFE) has been suggested as a tool to study the speciation of hydrocarbons in geological samples. Hydrocarbons extracted at the lower temperatures (e.g., 50°C) are presumed to be part of the freely extractable fraction, while those recovered at the high temperatures (e.g., 300 and 350°C) are those `trapped' within the macromolecular organic matrix and are therefore, resistant to desorption. The latter are released from the matrix after this undergoes thermally induced structural rearrangements. However, the question still remains if and to what extend, pyrolysis of the organic matrix can contribute to this fraction. This study shows, based on the characteristics of the sample matrix of two different shale samples subject to HT–SFE, that pyrolytic contributions at elevated extraction temperatures are only minor under the experimental conditions used, and that thermally induced structural changes in the macromolecular organic matrix are only partially irreversible.     

Oxygen isotope study of a Precambrian banded iron-formation,Hamersley Range,Western Australia

Oxygen isotope ratios were determined for quartz, magnetite, ankerite, siderite, riebeckite, hematite and talc in samples of banded iron-formation from the Dales Gorge Member of the Brockman Iron Formation and for quartz, dolomite and calcite in samples of the Wittenoom Dolomite and Duck Creek Dolomite Formations, all from the Hamersley Range area of Western Australia. Additionally, in order to interpret the measured isotope ratios, isotopic fractionations for oxygen between quartz, siderite and magnetite and between these minerals and water as a function of temperature were calculated, using a combination of spectroscopic and thermodynamic data and constraints set by experimental determinations of the fractionations.The Dales Gorge Member was found to have undergone isotopic exchange between minerals at a temperature estimated on the basis of the isotopic fractionations to be above 270°C and probably less than 310°C, during burial metamorphism. At these temperatures quartz and the carbonates were almost completely equilibrated with one another, while hematite apparently underwent negligible exchange. Magnetite may have undergone exchange in some samples but not others, as a result of permeability variations, or it may have been as resistant to exchange as hematite. Riebeckite, and probably talc as well, were also subject to exchange, but to a lesser degree or on a smaller scale than quartz and the carbonates. Hematite formed at temperatures of 140°C or below. Magnetite appears to have formed at temperatures above 140°C, and possibly over a range of temperatures between about 180 and 300°C.The Wittenoom Dolomite and Duck Creek Dolomite samples show apparent lack of equilibrium, due to incomplete exchange or to retrograde effects. A chert from the Wittenoom Dolomite, along with two samples from the Marra Mamba Iron Formation, with δ¹⁸O values of + 24%. can be considered to set a lower limit of about ?11%. on the δ¹⁸O value of the ocean 2.2 × 10⁹ yr ago. Internal fractionations in the Wittenoom Dolomite chert sample may be interpreted as yielding an upper limit on this oceanic δ¹⁸O value of ? 3.5%.     

Effects of freezing–thawing cycle on peatland active organic carbon fractions and enzyme activities in the Da Xing’anling Mountains,Northeast China

Freezing–thawing cycle (FTC) is an important environmental factor affecting soil physicochemical properties and microbial activities. The effects of FTC at mid-high latitudes, especially in the permafrost regions impacted by global warming, have become a hot topic for research. However, the responses of active organic carbon fractions and soil enzyme activities to FTC in the active layers of permafrost regions remain far from certain. In this study, soil samples from three soil layers of (0–15, 15–30 and 30–45 cm) an undisturbed peatlands in Da Xing’anling Mountains, Northeast China, were collected, and then subjected to various FTCs with a large (10 to ?10 °C) and a small (5 to ?5 °C) amplitudes, respectively. Results showed that the soil active organic carbon fractions and enzyme activities were sensitive to FTCs. The FTCs significantly increased water-extracted organic carbon (WEOC) concentration in the three soil layers by approximately 5–28 % for the large amplitude and 22–36 % for the small amplitude. In contrast, FTCs significantly decreased microbial biomass carbon (MBC) concentration, cellulase, amylase and invertase activities. Overall, the damage of FTCs to soil enzymes was severe at the deeper soil depths and for the large amplitude. Interestingly, the soil WEOC concentration was lower at the large amplitude of FTC compared with the small amplitude. When the numbers of FTCs increased, WEOC concentration began to decrease and MBC concentration and enzyme activities began to increase. In addition, the significant correlations between active organic carbon fractions and enzyme activities indicate that the increased WEOC by FTCs plays an important role in soil microbes and enzyme activities.     

Influence of Marble’s Texture on its Mechanical Behavior

This research work studied the influence of texture on the mechanical properties of crystalline rocks at the scale of the laboratory sample. The experiments were performed on a marble varying in texture, so that the study was conducted on homogeneous (entirely xenoblastic or totally granoblastic) and heterogeneous (mix of the two textures) specimens. The mechanical behavior of the homogeneous and heterogeneous samples was investigated with static and dynamic, destructive and nondestructive tests, in natural conditions, at the laboratory temperature, and at higher temperatures. The specimens were heated to 100, 200, and 300 °C, in order to examine the effect of heating temperature on the elastic modulus and P-waves velocity. As a result, the pure granoblastic marble exhibits values of the elastic modulus, P-waves velocity, and strengths, both in natural conditions and on heated specimens, lower than xenoblastic samples. Such different behavior can be explained by a higher grain boundaries porosity of the granoblastic marble. On heterogeneous samples, only the Rock Impact Hardness Number (RIHN) appears able to highlight the dependence of the mechanical properties on the rock texture. In particular, the impact strength improves with increasing the percentage of xenoblastic texture inside the specimen.     

Generation of aliphatic acid anions and carbon dioxide by hydrous pyrolysis of crude oils

Two crude oils with relatively high (0.60 wt%) and low (0.18 wt%) oxygen contents were heated in the presence of water in gold-plated reactors at 300°C for 2348 h. The high-oxygen oil was also heated at 200°C for 5711 h. The compositions of aqueous organic acid anions of the oils and of the headspace gases were monitored inn order to investigate the distribution of organic acids that can be generated from liquid petroleum.The oil with higher oxygen content generated about five times as much organic anions as the other oil. The dominant organic anions produced were acetate, propionate and butyrate. Small amounts of formate, succinate, methyl succinate and oxalate were also produced. The dominant oxygen-containing product was CO₂, as has been observed in similar studies on the hydrous pyrolysis of kerogen. These results indicate that a significant portion (10–30%) of organic acid anions reported i be generated by thermal alteration of oils in reservoir rocks. The bulk of organic acid anions present in formation waters, however, is most likely generated by thermal alteration of kerogen in source rocks. Kerogen is more abundant than oil in sedimentary basins and the relative yields of organic acid anions reported from the hydrous pyrolysis of kerogen are much higher than the yields obtained for the two oils.     

Impacts of subsurface heat storage on aquifer hydrogeochemistry

The use of shallow aquifers for subsurface heat storage in terms of energy management and building climatisation can lead to a temperature rise in the aquifer to 70 °C and above. The influence of temperature changes on individual mineral and sorption equilibria, reaction kinetics and microbial activity is largely known. However, the impact of heating to temperatures as high as 70 °C on the aquifer overall system has not been quantified yet. Temperature-related changes in sediment ion exchange behaviour, dimension and rates of mineral dissolution and precipitation as well as microbially enhanced redox processes were studied in column experiments using aquifer sediment and tap water at 10, 25, 40, and 70 °C. At 70 °C, a change in sediment sorption behaviour for cations and organic acids was postulated based on temporal changes in pH, magnesium, and potassium concentration in the experimental solution. No clear changes of pH, TIC and major cations were found at 10–40 °C. Redox zoning shifted from oxic conditions towards nitrate and iron(III) reducing conditions at 25 and 40 °C and sulphate reducing conditions at 70 °C. This was attributed to (a) a temperature-related increase in microbial reduction activity, and (b) three times higher release of organic carbon from the sediment at 70 °C compared to the lower temperatures. The findings of this study predict that a temperature increase in the subsurface up to 25 °C and above can impair the usability of ground water as drinking and process water, by reducing metal oxides and thus possibly releasing heavy metals from the sediment. Generally, at 70 °C, where clear cation and organic carbon desorption processes were observed and sulphate reducing conditions could be achieved, a site-specific assessment of temperature effects is required, especially for long-term operations of subsurface heat storage facilities.     

Characterization and adsorption of disperse dyes from wastewater onto cenospheres activated carbon composites

In the present research, coal fly ash, a waste by-product of thermal power plant, has been segregated to obtain hollow and spherical cenospheres which combined with activated carbon in different ratio for effectual remediation of wastewater. Fabricated cenospheres activated carbon (CNAC) composites were characterized by ATR-FTIR, SEM, XRD, BET and CILAS for functionality, surface modification, crystallinity, surface area, pore volume, pore size and particle size analysis, respectively. Batch adsorption has been applied to appraised maximum removal of Disperse Orange 25 (DO) and Disperse Blue 79:1 (DB) dyes at varying solution pH 2 to 12, adsorbent dose 0.1 g cenospheres + 0.1 g AC to 1.0 g cenospheres + 1.0 g AC, dye concentration 10 to 100 mg/L, agitation speed 80 to 240 rpm and contact time 5 to 300 min at three different temperatures (25, 35 and 45 °C). The maximum percentage removal was found to be 79 and 76% for DO and DB dyes, respectively, at optimized condition. Langmuir isotherm showed good interaction with adsorption data, and the obtained maximum equilibrium adsorption capacity was found to be 90.91 mg/g for DO and 83.33 mg/g for DB at 45 °C. Eventually, the negative ?G° (? 7.513 for DO and ? 7.767 for DB) has suggested the feasibility of dyes adsorption on CNAC composites.     

Experimental studies of organic-Zn complexes and their stability

Thermal decomposition, temperatures of four organic Zn complexes were evaluated experimentally by determining the change in sphalerite solubility with temperature in aqueous solutions containing organic compounds. The results show that decomposition takes place at 180°±5°C for lactic acid-Zn complex, 200°±5°C for EDTA-Zn, 240°±5°C for quinone-Zn and 190°±5°C for fulvic acid-Zn. It is also shown that at 190°–200°C sphalerite solubility is 4 to 7 times higher in NaCl solution containing organic compounds than that in NaCl solution without organic compounds. Studies were also conducted on the contents of Pb and Zn complexed by fulvic acid and humic acid in aqueous solutions the infrared spectra of fulvic acid-Zn and humic acid-Zn complexes, the differential thermal analysis of fulvic acid, humic acid and quinone and EDTA, and the variation in fulvic acid solubility in the seawater with temperature.     

Adsorption kinetics of herbicide paraquat in aqueous solution onto a low-cost adsorbent, swine-manure-derived biochar

Biochars have received increasing attention in recent years because of their significant properties such as carbon sequestration, soil fertility, and contaminant immobilization. In this work, the adsorptive removal of paraquat (1,1′-dimethyl-4,4′-dipyridinium chloride, one of the most widely used herbicides) from aqueous solution onto the swine-manure-derived biochar has been studied at 25 °C in a batch adsorption system. The adsorption rate has been investigated under the controlled process parameters including initial pH (i.e., 4.5, 6.0, 7.5, and 9.0), paraquat concentration (i.e., 0.5, 1.0, 2.0, 4.0, and 6.0 mg/L), and biochar dosage (i.e., 0.10, 0.15, 0.20, 0.25, and 0.30 g/L). Based on the adsorption affinity between cationic paraquat and carbon-like adsorbent, a pseudo-second order model has been developed using experimental data to predict the adsorption kinetic constant and equilibrium adsorption capacity. The results showed that the adsorption process could be satisfactorily described with the reaction model and were reasonably explained by assuming an adsorption mechanism in the ion exchange process. Overall, the results from this study demonstrated that the biomass-derived char can be used as a low-cost adsorbent for the removal of environmental cationic organic pollutants from the water environment.     

Distribution of branched tetraether lipids in geothermally heated soils: Implications for the MBT/CBT temperature proxy

Branched glycerol dialkyl glycerol tetraether (GDGT) membrane lipids occur in soils and peat bogs and are assumed to be produced by anaerobic bacteria. Two indices based on the distribution of these lipids in soils, the Cyclisation of Branched Tetraethers (CBT) and the Methylation of Branched Tetraethers (MBT) index have been shown to linearly relate to pH, and to mean annual air temperature (MAT) and pH, respectively. To directly evaluate the impact of changes in soil temperature on the MBT/CBT proxy, we determined these indices in soils sampled from a transect away from two hot springs in California, which provided a set of soils similar in composition but with different temperatures (12–41 °C). The CBT values of these geothermally heated soils show a good relation with pH (R² 0.76), similar to that of a global MBT/CBT calibration set. Also, the relationship between MBT, soil pH and temperature for the geothermally heated soils is similar to that of a global soil calibration set, although the intercept for the geothermally heated soils is significantly lower, likely because our data set is based on in situ soil temperatures rather than MAT. The results confirm the dependence of the MBT index on soil temperature and pH and support the applicability of the MBT/CBT indices as a proxy for continental palaeotemperatures and past soil pH.