Polycyclic aromatic hydrocarbons (PAHs) in particle-size fractions of urban topsoils

Polycyclic aromatic hydrocarbons’ (PAHs) concentrations in bulk samples are commonly used to assess contamination but PAHs are unevenly distributed among particle-size fractions. Seventeen urban surface soil samples from the city of Xuzhou, China, were collected and then fractionated into five size fractions (2,000–300, 300–150, 150–75, 75–28, and <28 μm). The concentrations of 12 US EPA PAHs were measured using gas chromatograph/mass spectrometry in various fractions, and the bulk soil samples and distribution patterns of PAHs in different particle-size fractions were investigated. The mean concentration of total PAHs in bulk soil samples was 1,879 ng/g. The median concentrations for all individual PAH were higher for the 75–2,000 μm fraction than for the <75 μm fraction. The distribution factors for various PAHs in <28 μm soil fraction were closely correlated (r = ?0.661, p < 0.019) to bulk soil fugacity capacity. The values of PAH isomer indicated that traffic emissions might be the major origin of PAHs in Xuzhou surface soils. Spearman correlation analysis was performed and the result suggested that soil organic carbon might be a factor controlling the concentrations of PAHs in soils.     

Aliphatic components of Victorian brown coal lithotypes

Victorian brown coal occurs in five major lithotypes distinguishable by colour index, petrography and bulk chemical analyses. The distributions of solvent extractable (free) and base hydrolysable (bound) n-alkanes, n-monocar?ylic acids, n-?,ω-dicar?ylic acids, n-ω-hydroxycar?ylic acids and n-alcohols were determined for samples of each of the five lithotypes (lithotype profile) and for seven samples of identical lithotype classification spanning a 100 m interval (depth profile) taken from a continuous bore core. The distributions of free molecular components in all classes are indicative of the predominant higher plant origin of this immature coal and provide strong support for the view that different lithotypes have derived from different, yet fairly specific paleobotanical communities. Despite an overall similarity in the distributions of aliphatic components from samples of identical lithotype classification, changes in the absolute concentrations and carbon preference indices (CPIs) of specific functional classes are observed in response to catagenetic influences even across the very small rank interval of the depth profile samples. Molecular distributions of bound components are similar to those of their free counterparts except that CPIs are generally lower and the relative contributions of lower molecular weight homologues (i.e. <C₂₂) are higher. Thedistributions of bound dicar?ylic acids and hydroxycar?ylic acids appear to reflect variations in the oxic/anoxic nature of the depositional paleoenvironments.     

Sagged phosphatic Nantgarw porcelain (ca. 1813–1820): Casualty of overfiring or a fertile paste?

Nantgarw phosphatic (bone-ash) porcelain (ca. 1813–1820) is renowned for its translucency and the high quality of its enamel decoration. However, only a small proportion of its wares (perhaps 10%) were successfully fired due to sagging (body distortion) and other problems. This indicates that: (1) In terms of its potential for generating a minimum melt, the Nantgarw paste had an unusually fertile composition, or (2) Nantgarw's staff had difficulties in controlling kiln temperatures, so that its wares tended to be overfired. This issue has been addressed using analytical data for sherds excavated from the factory site. Detailed modal, petrographic, and geochemical data demonstrate that extensively sagged wasters contain a high proportion (∼43–63 vol %) of a former melt phase but are surprisingly porous (7–25 vol % pores). In terms of minimum melt generation, the sagged samples have a more fertile bulk composition than their successfully fired counterparts. Most of the wasters contain subsolidus anorthite (∼An₉₅) enclosed by a melt phase with (once corrected for entrained silica polymorph crystallites) a eutectic (minimum melt) composition. The anorthite, however, was completely resorbed by the melt in some of the sagged samples, which subsequently crystallized liquidus anorthite that displays a quenched morphology. These samples were therefore fired above (T_max <1430°C, as estimated from melt compositions) the eutectic (T∼1290°C) in the anorthite–tricalcium phosphate–silica system. The fact that other wasters contain subsolidus anorthite and a minimum melt shows that firing at the eutectic did not guarantee a successful firing, regardless of the melt fertility of the paste. It is likely that the duration of firing near T_max and character of the object (i.e., flatware vs. hollow-ware) were also important variables in this regard. In addition to producing their well-known phosphatic wares, Nantgarw's proprietors apparently also experimented with silicious pastes with compositions akin to true porcelain. Some of silicious sherds found at the site have a lead-bearing (∼15 wt % PbO) glaze, indicating that they survived an early, high temperature biscuit firing, after which they were fired at lower temperature in the glost kiln (i.e., a “soft-paste type” firing sequence). Evidence that the Nantgarw kiln could achieve temperatures in the order of 1400°C further suggests that these silicious sherds are b.f. wasters. © 1999 John Wiley & Sons, Inc.     

The salt decay of medieval bricks at a vault in Brarup Church,Denmark

This paper presents an investigation of the decay of bricks in the chancel vault of Brarup Church located close to the Baltic Sea at the island of Falster in Denmark. The aim of the work was to study a peculiar phenomenon in order to prescribe appropriate treatment. Although protected by a lime plaster, some bricks were pulverized up to 50 mm deep from the topside. The decay occurred in a random pattern over the structure, with undamaged bricks positioned next to deteriorated bricks. The brick structure was investigated by Mercury Intrusion Porosiometry. All bricks had a majority of pores in the range 1–10 μm, but the decayed bricks also had a fraction of pores with a diameter less than 100 nm. The difference may be due to a lower firing temperature, or it may be a consequence of the salt decay. Salt analysis proved that the deteriorated bricks were contaminated with sodium chloride, which could have degraded the brick structure. However, the powdering of the bricks may be caused by the precipitation of gypsum, which was found in the brick powder but not in the deteriorated brick itself. According to calculations with the computer program RUNSALT, the precipitation of gypsum is much influenced by the presence of sodium chloride. The gypsum precipitates due to changes in temperature between 0 and 30°C and variations in relative humidity between 75 and 95%. Seasonal climatic changes in the attic were measured to cover this interval. Perhaps sodium chloride acted as a catalyst that facilitated the accumulation and precipitation of gypsum at the topside of the bricks. A sacrificial plaster, which is the traditional treatment for salt contaminated structures, would not prevent such decay.     

Visibility in airborne volcanic ash: considerations for surface transportation using a laboratory-based method

All modes of surface transportation can be disrupted by visibility degradation caused by airborne volcanic ash. Despite much qualitative evidence of low visibility on roads following historical eruptions worldwide, there have been few detailed studies that have attempted to quantify relationships between visibility conditions and observed impacts on network functionality and safety. In the absence of detailed field observations, such gaps in knowledge can be filled by developing empirical datasets through laboratory investigations. Here, we use historical eruption data to estimate a plausible range of ash-settling rates and ash particle characteristics for Auckland city, New Zealand. We propose and implement a new experimental set-up in controlled laboratory conditions, which incorporates a dual-pass transmissometer and solid aerosol generator, to reproduce these ash-settling rates and calculate visual ranges through the associated airborne volcanic ash. Our findings demonstrate that visibility is most impaired for high ash-settling rates (i.e. > 500 g m^?2 h^?1) and particle size is deemed the most influential ash characteristic for visual range. For the samples tested (all < 320 μm particle diameter), visibility was restricted to ~ 1–2 m when ash settling was replicated for very high rates (i.e. ~ 4000 g m^?2 h^?1) and was especially low when ash particles were fine-grained, more irregular in shape and lighter in colour. Finally, we consider potential implications for disruption to surface transportation in Auckland through comparisons with existing research which investigates the consequences of visual range reduction for other atmospheric hazards such as fog. This includes discussing how our approach might be utilised in emergency and transport management planning. Finally, we summarise strategies available for the mitigation of visibility degradation in environments contaminated with volcanic ash.     

Characterization of mean transit time at large springs in the Upper Colorado River Basin,USA: a tool for assessing groundwater discharge vulnerability

Environmental tracers (noble gases, tritium, industrial gases, stable isotopes, and radio-carbon) and hydrogeology were interpreted to determine groundwater transit-time distribution and calculate mean transit time (MTT) with lumped parameter modeling at 19 large springs distributed throughout the Upper Colorado River Basin (UCRB), USA. The predictive value of the MTT to evaluate the pattern and timing of groundwater response to hydraulic stress (i.e., vulnerability) is examined by a statistical analysis of MTT, historical spring discharge records, and the Palmer Hydrological Drought Index. MTTs of the springs range from 10 to 15,000 years and 90 % of the cumulative discharge-weighted travel-time distribution falls within the range of 2?10,000 years. Historical variability in discharge was assessed as the ratio of 10–90 % flow-exceedance (R _10/90%) and ranged from 2.8 to 1.1 for select springs with available discharge data. The lag-time (i.e., delay in discharge response to drought conditions) was determined by cross-correlation analysis and ranged from 0.5 to 6 years for the same select springs. Springs with shorter MTTs (<80 years) statistically correlate with larger discharge variations and faster responses to drought, indicating MTT can be used for estimating the relative magnitude and timing of groundwater response. Results indicate that groundwater discharge to streams in the UCRB will likely respond on the order of years to climate variation and increasing groundwater withdrawals.     

Copper desorption kinetics in wheat (Triticum aestivum L.) rhizosphere in some sewage sludge amended soils

Rhizosphere has different chemical and biological properties from bulk soils. Information about copper (Cu) desorption characteristics in the rhizosphere soils is limited. The objectives of this study were to determine Cu desorption characteristics and the correlation of its parameters with Cu extracted by DTPA-TEA, AB-DTPA and Mehlich 3 in bulk and rhizosphere amended soils with sewage sludge (10 g of sewage sludge was added to 1 kg soil) under greenhouse conditions in a rhizobox. The kinetics of Cu desorption in the rhizosphere and bulk was determined by successive extraction with DTPA-TEA in a period of 1 to 504 h at 25 ± 1 °C. The results showed that Cu extracted using several chemical extractants in the rhizosphere were significantly (P < 0.05) lower than in the bulk amended soils. In addition, Cu extracted using successive extraction in the rhizosphere were significantly (P < 0.01) lower than in the bulk soils. The best model for describing extraction data for the bulk and rhizosphere soils was the parabolic diffusion equation. Desorption kinetics of Cu conformed fairly well to first order and power function models. The results indicated that Cu diffusion rate in the wheat rhizosphere soils lower than in the bulk soils. Cu desorption rate in parabolic diffusion ranged from 0.326 to 0.580 mg kg^?1 h^?1/2 in the bulk soils, while it ranged from 0.282 to 0.490 mg kg^?1 h^?1/2 in the rhizosphere soils. Significant correlation (P < 0.05) between determine R values of parabolic diffusion and Cu desorption during 504 h with extracted Cu using DTPA-TEA, AB-DTPA and Mehlich 3 were found in the bulk and the rhizosphere soils. The results of this research revealed that Cu desorption characteristics in the wheat rhizosphere soils are quite different from bulk soils amended with sewage sludge.     

Determination of perchlorate and iodide concentrations in edible seaweeds

Perchlorate and iodide concentrations were determined in brown (Undaria pinnatifida and Laminaria japonica) and red (Porphyra sp.) edible seaweeds, which are commonly consumed by Korean people, with the use of ion chromatography, coupled with a tandem mass spectrometer. Seaweeds (i.e., good sources of iodine) are among the most important plant life in the ocean and commonly consumed as food and nutritional supplement in South Korea. All seaweed samples were purchased from different regions in South Korea. The detected concentrations of perchlorate were as follows: 19.7–620.7 μg kg^?1 dry weight (n = 11, mean concentration = 149.2 μg kg^?1 dry weight) for L. japonica and 7.3–21.7 μg kg^?1 dry weight (mean concentration = 10.6 μg kg^?1 dry weight) for U. pinnatifida. Of the 11 samples of Porphyra sp., only 1 sample showed 6.7 μg kg^?1 dry weight perchlorate. The concentrations of iodide in all seaweed samples varied from 0.44 to 6,800 mg kg^?1 dry weight. L. japonica samples (n = 11) had significantly higher iodide concentrations, with a mean of 5,261 mg kg^?1 dry weight. The bioconcentration factor values for perchlorate and iodide in the three different seaweeds varied widely and showed similar variation trends. The trend for perchlorate and iodide was Porphyra sp. < U. pinnatifida < L. japonica. The results have provided growing evidence that perchlorate frequently occurs in food products.     

Importance of Biogeomorphic and Spatial Properties in Assessing a Tidal Salt Marsh Vulnerability to Sea-level Rise

We evaluated the biogeomorphic processes of a large (309 ha) tidal salt marsh and examined factors that influence its ability to keep pace with relative sea-level rise (SLR). Detailed elevation data from 1995 and 2008 were compared with digital elevation models (DEMs) to assess marsh surface elevation change during this time. Overall, 37 % (113 ha) of the marsh increased in elevation at a rate that exceeded SLR, whereas 63 % (196 ha) of the area did not keep pace with SLR. Of the total area, 55 % (169 ha) subsided during the study period, but subsidence varied spatially across the marsh surface. To determine which biogeomorphic and spatial factors contributed to measured elevation change, we collected soil cores and determined percent and origin of organic matter (OM), particle size, bulk density (BD), and distance to nearest bay edge, levee, and channel. We then used Akaike Information Criterion (AICc) model selection to assess those variables most important to determine measured elevation change. Soil stable isotope compositions were evaluated to assess the source of the OM. The samples had limited percent OM by weight (<5.5 %), with mean bulk densities of 0.58 g cm^-3, indicating that the soils had high mineral content with a relatively low proportion of pore space. The most parsimonious model with the highest AICc weight (0.53) included distance from bay's edge (i.e., lower intertidal) and distance from levee (i.e., upper intertidal). Close proximity to sediment source was the greatest factor in determining whether an area increased in elevation, whereas areas near landward levees experienced subsidence. Our study indicated that the ability of a marsh to keep pace with SLR varied across the surface, and assessing changes in elevation over time provides an alternative method to long-term accretion monitoring. SLR models that do not consider spatial variability of biogeomorphic and accretion processes may not correctly forecast marsh drowning rates, which may be especially true in modified and urbanized estuaries. In light of SLR, improving our understanding of elevation change in these dynamic marsh systems will play a crucial role in forecasting potential impacts to their sustainability and the survival of these ecosystems.     

From London to Liverpool: Evidence for a Limehouse–Reid porcelain connection based on the analysis of sherds from the Brownlow Hill (ca. 1755–1767) factory site

The diversity of Brownlow Hill porcelains of the W^m Reid & Co. era is due to the remarkably wide range in the composition of their pastes and glazes and inferred firing conditions relative to the initial vitrification temperature. Sixteen of 21 analyzed sherds from the factory site are bone‐ash wares that display large variations in their bulk chemical composition. The remaining samples have silicious‐aluminous (akin to “stone china” sensu Richard Pococke in 1750) and silicious‐aluminous‐calcic (“S‐A‐C”) compositions that resemble Limehouse (London) and Pomona (Staffordshire) porcelains produced during the 1740s. The mineralogy of the Brownlow Hill S‐A‐C sherds suggests firing at a relatively high temperature (T_max approaching 1400°C, based on relations on the SiO₂‐Al₂O₃‐CaO phase diagram), thereby obscuring the identity of some of the ingredients (e.g., the source of CaO) used in their manufacture. Limehouse and Brownlow Hill may have been linked through the activities of William Ball, who is mentioned in connection with both factories, or indirectly via former Limehouse staff later employed at the Pomona factory, located not far from a W^m Reid & Co. branch factory in Shelton, Stoke‐on‐Trent. In terms of a time line, knowledge of these pastes appears to have spread first from London to Staffordshire, and then to Liverpool. © 2003 Wiley Periodicals, Inc.     

Cumulates of arc magmas incorporated into the Sulu UHP metamorphic belt,eastern China

ABSTRACT

The Hujialin ultramafic complex in the central region of the Sulu ultra-high pressure (UHP) metamorphic belt consists of discontinuous lenses of garnet-bearing clinopyroxenite and dunite surrounded by marginal serpentinite. The clinopyroxenite shows relatively low concentrations of compatible elements, such as Cr (≤1670 ppm) and Ni (≤514 ppm) and Ir-group platinum group elements (IPGE; Ir, Os, and Ru; ≤4.8 ppb in total). They show varying ratios (0.02–2.50) of IPGE to Pd-group PGE (PPGE). Their chondrite-normalized rare earth elements (REE) patterns are convex and the total REE concentrations range from 18 to 63 times that of Cl chondrite. The bulk rocks show a ‘subduction-related’ geochemical signature, with high concentrations of fluid-mobile elements (i.e. Sr, Ba) relative to high-field strength elements (i.e. Nb, Y, Zr). Clinopyroxene is diopside and contains low Al₂O₃ (<2.76 wt.%) and high SiO₂ (54.6–56.9 wt.%). Olivine grains enclosed by clinopyroxene and in the matrix show relatively low Fo (76.6–80.7) and NiO contents (0.18–0.29 wt.%). The bulk rock compositions and mineral chemistry of olivine and clinopyroxene suggest that the unit was a cumulate of a subduction-related melt. On the other hand, dunite and its hydration product, serpentinite, have a different origin. The bulk rock and mineral chemistry suggest that dunite represents a mantle wedge peridotite in a spinel-stable field. Both clinopyroxenite and spinel-bearing dunite were once located in the mantle wedge below the southern margin of the North China craton (NCC), and were dragged by a mantle flow into the continental subduction channel along the interface between the subducting Yangtze craton (YZC) and the overlying NCC. Although clinopyroxenite and dunite are dense (2.8–3.2 g/cm³), the buoyancy-driven exhumation of voluminous granitic rocks of the YZC likely brought clinopyroxenite and dunite to shallow crustal depths. The lack of the evidence for high pressure to ultra-high pressure (HP-UHP) metamorphism in spinel-bearing dunite may be explained by overall low Al and Ca in the bulk rocks. Alternatively, dunite was not subducted to deep levels, but exhumed together with the deeply subducted clinopyroxenites and granite during their exhumation.     

Ca-Eskola incorporation in clinopyroxene: limitations and petrological implications for eclogites and related rocks

Clinopyroxene is an essential mineral in eclogitic rocks. It commonly contains minor amounts of the defect-bearing Ca-Eskola (CaEs, Ca_0.5□_0.5AlSi₂O₆) component, with higher concentrations generally considered to indicate a high-pressure origin at least within the coesite stability field. Changes in pressure and temperature conditions can lead to exsolution of this component as a free SiO₂ phase, which may have a number of petrological implications. This makes it important to understand the factors that maximize CaEs incorporation in clinopyroxene. We have undertaken a series of experiments at high pressures and temperatures (4–10 GPa and 1000–1350 °C) to further investigate the systematics of CaEs incorporation in eclogite-like clinopyroxene and the factors responsible for maximizing CaEs contents. Two simple chemical systems were chosen that allow unambiguous interpretation of the results: (1) CMAS + H₂O and (2) two compositions in the NCMAS system. All experimental products contained clinopyroxene and garnet along with either a free SiO₂ phase or a silicate melt. Coexisting garnet is grossular-rich, generally with X _gr ≥ 0.67. Compositional variations are attributable to the presence or absence of melt and changes in modal amounts of garnet at different pressure–temperature conditions. Even small amounts of H₂O lower the solidus temperature and the presence of a melt reduces the SiO₂ activity, which destabilizes the CaEs component in clinopyroxene. The CaEs and the Ca-Tschermaks (CaTs, CaAl₂SiO₆) components in clinopyroxene decrease with increasing jadeite mole fraction, which is also a function of pressure and bulk Al content. Modeling X-ray powder diffraction data yields a molar volume for the CaEs endmember of V _CaEs = 60.87(63) cm³, which reasonably agrees with a literature value that was estimated from natural samples. In the presence of coexisting coesite, the CaEs and CaTs do not vary independently of each other, being controlled by the internal equilibrium 2CaEs = CaTs + 3SiO₂ (coesite). This relation, observed in simple systems (i.e., CMAS ± Na), is also obeyed by clinopyroxene in more complex, natural analog bulk compositions. An assessment of available experimental data reveals a maximum of 15–18 mol% CaEs in eclogitic clinopyroxene at conditions corresponding to 130–180 km depth. CaEs contents are maximized at high temperatures; i.e., at or near the solidus in the presence of coesite. Thus, this study supports the role of CaEs exsolution in contributing to melt generation during upwelling of eclogite bodies in the mantle, albeit with some caveats. Somewhat higher maximum CaEs contents (~20 mol%) are found in Ca and Al-rich bulk compositions, such as grospydite xenoliths. Such bulk compositions also seem to require the coexistence of kyanite. Other Ca and Al-rich rock types, like rodingites, should have the potential of containing CaEs-rich clinopyroxenes, except that they are SiO₂-undersaturated. This emphasizes the further role of bulk composition, in addition to high temperatures, in achieving maximum CaEs contents in high-pressure clinopyroxene.     

Zinc desorption kinetics in bean (Phaseolus vulgaris L.) rhizosphere in sewage sludge-amended calcareous soils

Desorption of Zinc (Zn) in the rhizosphere soil is the primary factor that affects bioavailability of Zn. To improve predictions of Zn availability in amended soil, it is important that time-dependent desorption behavior of Zn in the rhizosphere soil should be understood. The greenhouse experiment was performed to determine Zn desorption characteristics in the bulk and the bean rhizosphere soils amended with municipal sewage sludge (1 % w/w) using rhizobox. The kinetics of Zn desorption was determined by successive extraction with 10-mM citric acid in a period of 1–504 h at 25 ± 1 °C in the bulk and the rhizosphere soils. Moreover, Zn was extracted using three extractants (DTPA-TEA, AB-DTPA, and Mehlich 3) in the bulk and the rhizosphere soils. The results showed that Zn extracted and Zn desorption rate in the bean rhizosphere soils were significantly (P < 0.01) lower than in the bulk soils. The mean of Zn desorption in the bulk and the rhizosphere soils were 16.47 and 15.50 mg kg^?1, respectively. Desorption kinetics of Zn conformed fairly well to first-order, parabolic diffusion, and power function equations. The results of kinetics study indicated that desorption rate coefficients decreased in the rhizosphere soils compared to the bulk soils. The correlation studies showed that the rate constants in the power function equation were significantly correlated (P < 0.05) with Zn extracted using DTPA-TEA, AB-DTPA and Mehlich 3 in the bean rhizosphere and the bulk soils. The results of this research showed that Zn desorption in citric acid in the bean rhizosphere of amended soils were lower than the bulk of amended soils.     

Role of rhizosphere and soil properties for the phytomanagement of a salt marsh polluted by mining wastes

The goal of this study was to evaluate the soil properties and their modifications within the rhizosphere of spontaneous vegetation as key factors to assess the phytomanagement of a salt marsh polluted by mining wastes. A field survey was performed based on a plot sampling design. The results provided by the analyses of rhizospheric soil (pH, electrical conductivity (EC), organic carbon, total nitrogen, etc.) and metal(loid)s’ phytoavailability (assessed by EDTA) were discussed and related to plant metal uptake. The averages of pH and EC values of the bulk soil and rhizospheric samples were in the range of neutral to slightly alkaline (pH 7–8) to saline (>2 dS m^?1), respectively. Heavy metal and As concentrations (e.g. ~600 mg kg^?1 As, ~50 mg kg^?1 Cd, ~11,000 mg kg^?1 Pb) were higher in the rhizosphere for both total and EDTA-extractable fraction. Phragmites australis uptaked the highest concentrations in roots (e.g. ~66 mg kg^?1 As, ~1,770 mg kg^?1 Zn) but not in shoots, for which most of plant species showed low values for Zn (<300 mg kg^?1) but not for Cd (>0.5 mg kg^?1) or Pb (~20–40 mg kg^?1). Vegetation distribution in the studied salt marsh looked to be more affected by salinity than by metal pollution. The free availability of water for plants and the incoming nutrient-enriched effluents which flow through the salt marsh may have hindered the metal(loid)s’ phytotoxicity. The phytomanagement of these polluted areas employing the spontaneous vegetation is a good option in order to improve the ecological indicators and to prevent the transport of pollutants to nearby areas.     

Geochemical characteristics and environmental significance of Talede loess–paleosol sequences of Ili Basin in Central Asia

The loess–paleosol deposit in Central Asia is a sensitive indicator of the evolution of the quaternary paleoclimate in the Westerlies, providing insight into the quaternary climate history and its relationship with global climatic changes. Based on the geochemical analysis of elemental composition of densely sampled strata from Talede loess–paleosol sequence in the Ili Basin, the results showed that SiO₂ had the highest major elements content, followed by Al₂O₃. The order of compositional abundance of major elements was generally as follows: SiO₂ > Al₂O₃ > CaO > Fe₂O₃ > MgO > Na₂O > K₂O. Trace elements (i.e. Rb, Sr, Sc, Ni, Cu, Ga, Mo, Y, Pb, Th) in the paleosol layers (i.e. S ₀, S _m, S ₁) and the loess layer of L ₁ were enriched relative to underlain loess (L ₂) horizons, except for the contents of Zr, Cs, Nd, and La in paleosol layers. All of geochemical proxies, such as enrichment factor, Rb/Sr ratio, eluvial coefficient (K _i ) and chemical weathering index, display no obvious differentiation in the Talede loess–paleosol deposit. The results indicate that the weak chemical weathering, greater evaporation and low effective moisture in Ili Basin, are to a degree weaker than those in the China Loess Plateau and the climate was warm–dry during the interglacial period. In addition, the loess of Ili area is rich in schistose minerals and implies that the loess may come from the deserts of Central Asia and it may be closely related to the widespread aridification of Central Asia.     

Cation exchange capacity of loess and overlying soil in the non-carbonate loess sections, North-Western Croatia

The adsorption properties in terms of cation exchange capacity and their relation to the soil and sediment constituents (clay minerals, Fe-, Mn-, and Al-oxyhydroxides, organic matter) were investigated in loess, soil-loess transition zone, and soil at four loess-soil sections in North-Western Croatia. Cation exchange capacity of the bulk samples, the samples after oxalate extraction of Fe, Mn and Al, and after removal of organic matter, as well as of the separated clay fraction, was determined using copper ethylenediamine. Cation exchange capacity (pH～7) of the bulk samples ranges from 5 to 12 cmol _c /kg in soil, from 7 to 15 cmol _c /kg in the soil-loess transition zone, and from 12 to 20 cmol _c /kg in loess. Generally, CEC values increase with depth. Oxalate extraction of Fe, Mn, and Al, and removal of organic matter cause a CEC decrease of 3–38% and 8–55%, respectively, proving a considerable influence of these constituents to the bulk CEC values. In the separated clay fraction (<2 μm) CEC values are up to several times higher relative to those in the bulk samples. The measured CEC values of the bulk samples generally correspond to the clay mineral content identified. Also, a slight increase in muscovite/illite content with depth and the vermiculite occurrence in the loess horizon are concomitant with the CEC increase in deeper horizons, irrespective of the sample pretreatment.     

Petrogenesis of 3.15 Ga old Banasandra komatiites from the Dharwar craton,India: Implications for early mantle heterogeneity

Spinifex-textured.magnesian(MgO 25 wt.%) komatiites from Mesoarchean Banasandra greenstone belt of the Sargur Group in the Dharwar craton,India were analysed for major and trace elements and~(147,146)Sm-~(143,142)Nd systematics to constrain age,petrogenesis and to understand the evolution of Archean mantle.Major and trace element ratios such as CaO/Al_2O_3.Al_2O_3/TiO_2,Gd/Yb,La/Nb and Nb/Y suggest aluminium undepleted to enriched compositional range for these komatiites.The depth of melting is estimated to be varying from 120 to 240 km and trace-element modelling indicates that the mantle source would have undergone multiple episodes of melting prior to the generation of magmas parental to these komatiites.Ten samples of these komatiites together with the published results of four samples from the same belt yield ~(147)Sm-~(143)Nd isochron age of ca.3.14 Ga with an initial ε_(Nd)(f) value of+3.5.High precision measurements of ~(142)Nd/~(144)Nd ratios were carried out for six komatiite samples along with standards AMES and La Jolla.All results are within uncertainties of the terrestrial samples.The absence of~(142)Nd/~(144)Nd anomaly indicates that the source of these komatiites formed after the extinction of ~(146)Sm,i.e.4.3 Ga ago.In order to evolve to the high ε_(Nd)(t) value of +3.5 by 3.14 Ga the time-integrated ratio of~(147)Sm/~(144)Nd should be 0.2178 at the minimum.This is higher than the ratios estimated,so far,for mantle during that time.These results indicate at least two events of mantle differentiation starting with the chondritic composition of the mantle.The first event occurred very early at ~4.53 Ga to create a global early depleted reservoir with superchondritic Sm/Nd ratio.The source of Isua greenstone rocks with positive ~(142)Nd anomaly was depleted during a second differentiation within the life time of ~(146)Sm,i.e.prior to 4.46 Ga.The source mantle of the Banasandra komatiite was a result of a differentiation event that occurred after the extinction of the ~(146)Sm,i.e.at 4.3 Ga and prior to 3.14 Ga.Banasandra komatiites therefore provide evidence for preservation of heterogeneities generated during mantle differentiation at4.3 Ga.     

Metal geochemical and mineral magnetic characterization of the <2.5 μm fraction of urban soils in Xuzhou (China)

The concentrations of metals (Pb, Cu, Zn, Co, Ni, Fe and Mn) in the <2.5 μm fraction of surface soils (0–5 cm) from highly industrialized areas in Xuzhou (China) were determined. All analyzed metals with the exception of Mn and Co in the present study showed elevated concentrations in the <2.5 μm fraction of soils compared to background concentrations, particularly for Zn. Metal enrichment was positively correlated with carbonate complexation constants (but not bulk solubility products) as well as the first stability constants of metal-citrate, likely suggesting that both metal–organic complexation and/or precipitation of carbonate surfaces that subsequently adsorb metals are likely responsible for these metal enrichment on these samples. Sequential extraction analysis shows the metals Pb, Cu, Zn, Co and Mn were largely associated with the reducible fraction, whereas Ni was largely associated with the oxidisable fraction. Manganese is the only metal showing significant association with the exchangeable fraction (up to 33 %), suggesting that it may be the most susceptible metal to mobilization. Mineral magnetic analysis indicates that ferrimagnetic SSD + SP (stable single domain + superparamagnetic) minerals dominated the <2.5 μm fraction of Xuzhou surface soils. Lead, Cu and Zn were found to show significant correlations with χlf (p < 0.01), suggesting that magnetic technique might be beneficially used as a rapid and inexpensive method to estimate these metal contaminations in the <2.5 μm fraction of surface soils.