Chemical Trace Research Articles

Groundwater sources and geochemical processes in a crystalline fault aquifer

The origin of water flowing in faults and fractures at great depth is poorly known in crystalline media.This paper describes a field study designed to characterize the geochemical compartmentalization of adeep aquifer system constituted by a graben structure where a permeable fault zone was identified. Analysesof the major chemical elements, trace elements, dissolved gases and stable water isotopes reveal theorigin of dissolved components for each permeable domain and provide information on various watersources involved during different seasonal regimes. The geochemical response induced by performinga pumping test in the fault-zone is examined, in order to quantify mixing processes and contributionof different permeable domains to the flow. Reactive processes enhanced by the pumped fluxes are alsoidentified and discussed.The fault zone presents different geochemical responses related to changes in hydraulic regime. Theyare interpreted as different water sources related to various permeable structures within the aquifer.During the low water regime, results suggest mixing of recent water with a clear contribution of olderwater of inter-glacial origin (recharge temperature around 7 C), suggesting the involvement of watertrapped in a local low-permeability matrix domain or the contribution of large scale circulation loops.During the high water level period, due to inversion of the hydraulic gradient between the major permeablefault zone and its surrounding domains, modern water predominantly flows down to the deep bedrockand ensures recharge at a local scale within the graben.Pumping in a permeable fault zone induces hydraulic connections with storage-reservoirs. The overlaidregolith domain ensures part of the flow rate for long term pumping (around 20% in the present case).During late-time pumping, orthogonal fluxes coming from the fractured domains surrounding the majorfault zone are dominant. Storage in the connected fracture network within the graben structure mainlyensures the main part of the flow rate (80% in the present case). Reactive processes are induced by mixingof water from different sources and transfer conditions. A specific approach is applied to quantify thereaction rate involved along the pumping time. Autotrophic denitrification coupled with iron mineralsoxidation is highlighted and water rock interaction is clearly enhanced by the flux changes induced bypumping.

A Non-destructive Bulk Currency Detection System (BCDS) for Screening Smuggled Currency

Bulk cash smuggling is a serious issue in recent years. It is estimated that $6–36B flow illegally between the United States and Mexico each year during otherwise legitimate border crossings. A nondestructive bulk currency detection system (BCDS) for screening pedestrians, vehicles and shipping containers will significantly improve boarder security, protect domestic economics and deter criminal and terrorist activity. However, such a practical device is not yet available because neither the target detection technique nor the instrumentation has been defined. In this paper, we evaluated the currency characteristics that provide a basis for detection, relevant physical/chemical instrumental approaches, and a rationale for selection of an approach to build a practical BCDS. US currency releases volatile compounds. These emissions can be used as a chemical signature in currency detection. The literature regarding characterization of volatile compounds associated with US currency is limited. To identify the unique vapor signature of US currency, we analyzed VOC emission from currency bills using thermal desorption GC/MS. This enabled calculation of emission rates of volatile compounds. The results were consistent with prior studies of currency emissions. From our data and the literature, a tentative fingerprint that represents currency can be selected from among the complex background present in real currency. The analysis shows that a most-likely US currency vapor signature contains a specific set of volatiles at low concentrations. A successful practical BCDS based on volatiles must be able to accurately identify and quantify a speciated set of trace chemicals from a complex and highly variable matrix. Variations of GC/MS with SPME preconcentration can result in near-term methods. Future developments are needed to address optimization of methodology and meet the need for rapid sampling, detection with speciation. Sensor arrays can also provide a platform for currency detection and would improve logistics over larger instruments.

Characterization of estrogen and androgen activity of food contact materials by different in vitro bioassays (YES, YAS, ERα and AR CALUX) and chromatographic analysis (GC-MS, HPLC-MS).

Endocrine active substances (EAS) show structural similarities to natural hormones and are suspected to affect the human endocrine system by inducing hormone dependent effects. Recent studies with in vitro tests suggest that EAS can leach from packaging into food and may therefore pose a risk to human health. Sample migrates from food contact materials were tested for estrogen and androgen agonists and antagonists with different commonly used in vitro tests. Additionally, chemical trace analysis by GC-MS and HPLC-MS was used to identify potential hormone active substances in sample migrates. A GC-MS method to screen migrates for 29 known or potential endocrine active substances was established and validated. Samples were migrated according to EC 10/2011, concentrated by solid phase extraction and tested with estrogen and androgen responsive reporter gene assays based on yeast cells (YES and YAS) or human osteoblast cells (ERα and AR CALUX). A high level of agreement between the different bioassays could be observed by screening for estrogen agonists. Four out of 18 samples tested showed an estrogen activity in a similar range in both, YES and ERα CALUX. Two more samples tested positive in ERα CALUX due to the lower limits of detection in this assay. Androgen agonists could not be detected in any of the tested samples, neither with YAS nor with AR CALUX. When testing for antagonists, significant differences between yeast and human cell-based bioassays were noticed. Using YES and YAS many samples showed a strong antagonistic activity which was not observed using human cell-based CALUX assays. By GC-MS, some known or supposed EAS were identified in sample migrates that showed a biological activity in the in vitro tests. However, no firm conclusions about the sources of the observed hormone activity could be obtained from the chemical results.

The distribution of dissolved iron in the West Atlantic Ocean.

Iron (Fe) is an essential trace element for marine life. Extremely low Fe concentrations limit primary production and nitrogen fixation in large parts of the oceans and consequently influence ocean ecosystem functioning. The importance of Fe for ocean ecosystems makes Fe one of the core chemical trace elements in the international GEOTRACES program. Despite the recognized importance of Fe, our present knowledge of its supply and biogeochemical cycle has been limited by mostly fragmentary datasets. Here, we present highly accurate dissolved Fe (DFe) values measured at an unprecedented high intensity (1407 samples) along the longest full ocean depth transect (17500 kilometers) covering the entire western Atlantic Ocean. DFe measurements along this transect unveiled details about the supply and cycling of Fe. External sources of Fe identified included off-shelf and river supply, hydrothermal vents and aeolian dust. Nevertheless, vertical processes such as the recycling of Fe resulting from the remineralization of sinking organic matter and the removal of Fe by scavenging still dominated the distribution of DFe. In the northern West Atlantic Ocean, Fe recycling and lateral transport from the eastern tropical North Atlantic Oxygen Minimum Zone (OMZ) dominated the DFe-distribution. Finally, our measurements showed that the North Atlantic Deep Water (NADW), the major driver of the so-called ocean conveyor belt, contains excess DFe relative to phosphate after full biological utilization and is therefore an important source of Fe for biological production in the global ocean.

Polyacrylic acid sodium salt film entrapped Ag-nanocubes as molecule traps for SERS detection

Surface-enhanced Raman spectroscopy (SERS) is a fast analytical technique for trace chemicals; however, it requires the active SERS-substrates to adsorb analytes, thus limiting target species to those with the desired affinity for substrates. Here we present networked polyacrylic acid sodium salt (PAAS) film entrapped Ag-nanocubes (denoted as Ag-nanocubes@PAAS) as an effective SERS-substrate for analytes with and without high affinity. Once the analyte aqueous solution is cast on the dry Ag-nanocubes@PAAS substrate, the bibulous PAAS becomes swollen forcing the Ag-nanocubes loose, while the analytes diffuse in the interstices among the Ag-nanocubes. When dried, the PAAS shrinks and pulls the Ag-nanocubes back to their previous aggregated state, while the PAAS network “detains” the analytes in the small gaps between the Ag-nanocubes for SERS detection. The strategy has been proven effective for not only singleanalytes but also multi-analytes without strong affinity for Ag, showing its potential in SERS-based simultaneous multi-analyte detection of both adsorbable and non-adsorbable pollutants in the environment.

Searching for nonlocal lithologies in the Apollo 12 regolith: A geochemical and petrological study of basaltic coarse fines from the Apollo lunar soil sample 12023,155

AbstractNew data from a petrological and geochemical examination of 12 coarse basaltic fines from the Apollo 12 soil sample 12023,155 provide evidence of additional geochemical diversity at the landing site. In addition to the bulk chemical composition, major, minor, and trace element analyses of mineral phases are employed to ascertain how these samples relate to the Apollo 12 lithological basalt groups, thereby overcoming the problems of representativeness of small samples. All of the samples studied are low‐Ti basalts (0.9–5.7 wt% TiO2), and many fall into the established olivine, pigeonite, and ilmenite classification of Apollo 12 basaltic suites. There are five exceptions: sample 12023,155_1A is mineralogically and compositionally distinct from other Apollo 12 basalt types, with low pigeonite REE concentrations and low Ni (41–55 ppm) and Mn (2400–2556 ppm) concentrations in olivine. Sample 12023,155_11A is also unique, with Fe‐rich mineral compositions and low bulk Mg# (=100 × atomic Mg/[Mg+Fe]) of 21.6. Sample 12023,155_7A has different plagioclase chemistry and crystallization trends as well as a wider range of olivine Mg# (34–55) compared with other Apollo 12 basalts, and shows greater similarities to Apollo 14 high‐Al basalts. Two other samples (12023,155_4A, and _5A) are similar to the Apollo 12 feldspathic basalt 12038, providing additional evidence that feldspathic basalts represent a lava flow proximal to the Apollo 12 site rather than material introduced by impacts. We suggest that at least one parent magma, and possibly as many as four separate parent magmas, are required in addition to the previously identified olivine, pigeonite, and ilmenite basaltic suites to account for the observed chemical diversity of basalts found in this study.

Design of a High-Throughput Chemical Trace Detection Portal That Samples the Aerodynamic Wake of a Walking Person

The aerodynamic wake behind a walking person is first investigated using flow visualization and spectrophotometry in order to characterize the plume-to-wake transition and the decay of a trace body contaminant downstream of a walking human. The buoyant human thermal plume is shown to transition to an aerodynamic wake at a walking speed of 0.2 m/s. At higher walking speeds, the human wake is highly turbulent, resulting in an exponential decay of a passive scalar downstream of the walking human subject. From these results, a high-throughput chemical trace detection portal that uses the natural momentum of the wake to assist its collection is designed. This wake collection portal is shown to be capable of substantial improvement in security-checkpoint throughput over previous trace-detection-screening technology. To collect and sample the trace-bearing wake for a chemical signal, air flow rates nearly an order of magnitude larger than those of the previous collection technology must be accommodated. A high-flow-rate particle impactor was designed and tested to effectively collect the entire human aerodynamic wake. This impactor accommodates a flow rate of 750 L/s with a particle cutoff diameter of 5 μm. An iterative CFD process is described which streamlined the impactor geometry to reduce the total pressure drop across it. Experimental results are presented on the impactor collection efficiency. Preliminary experimental results show that trace chemicals can be detected at a useful level from a range of locations across the body when a human subject passes through the system wearing a chemical particle patch source.

Petrogenetic significance of ocellar camptonite dykes in the Ditrău Alkaline Massif, Romania

Abstract Camptonite dykes intrude the rift-related Mesozoic igneous body of the Ditrau Alkaline Massif, Eastern Carpathians, Romania. We present and discuss mineral chemical data, major and trace elements, and the Nd isotopic compositions of the dykes in order to define their nature and origin. The dykes are classified as the clinopyroxene-bearing (camptonite-I) and clinopyroxene-free (camptonite-II) varieties. Camptonite-I consists of aluminian–ferroan diopside phenocrysts accompanied by kaersutite, subordinate Ti-rich annite, albite to oligoclase and abundant calcite–albite ocelli. Camptonite-II comprises K-rich hastingsite to magnesiohastingsite, Ti-rich annite, albite to andesine, abundant accessory titanite and apatite, and silicate ocelli filled mainly with plagioclase (An4–34). Age-corrected 143Nd/144Nd ratios vary from 0.51258 to 0.51269. The high eNd values of + 4.0 to + 6.1 which are consistent with intra-plate composition, together with light rare earth element (LREE), large ion lithophile element (LILE) and high field strength element (HFSE) enrichment in the camptonites is ascribed to the formation of small melt batches of a metasomatised sub-lithospheric mantle source. The presence of an asthenospheric ‘high μ’ ocean island basalt (HIMU-OIB)-type mantle component in the source region has also been revealed. A 1–4% degree of partial melting of an enriched garnet lherzolite mantle source containing pargasitic amphibole followed by fractionation is inferred to have been involved in the generation of the camptonites. They are deduced to be parental melts to the Ditrau Alkaline Massif.

Culture-Driven Mortality in Caspian seal (Pusa caspica) at Southern Fringe of Caspian Sea

Caspian seal (Pusa caspica) is countered as a unique, endangered species, restricted only to the Caspian Sea. High death rate of Caspian seal has been reported owing to chemical infections, extreme concentration of chemical trace elements, organochlorine pollutants, etc. Among numerous possible reasons for mortality of Caspian seals, the role of culture in mortality has always been less-noticed.Accordingly, the present study was put forth by studying the culture of inhabitants at Southern border of Caspian Sea. For this, the behavior of local communities was interviewed. It was observed that Iranian people were not adequately familiar with real worth of different creatures in environment, and considered them as dangerous enemies, or at least annoying. Therefore, when encounter the animals, they attempt to kill, harass, or scare them away. Usually, unidimensional view of financial gain from seals, and excessive fishing of aquatics fed by seals put them in danger of extinction. Over all, In order to gain more consistent findings on this matter, furthur researches are suggested.

ON THE GEOCHEMICAL CHARACTER OF PRIMARY Fe-Mn PHOSPHATES BELONGING TO THE TRIPHYLITE-LITHIOPHILITE, GRAFTONITE-BEUSITE, AND TRIPLITE-ZWIESELITE SERIES: FIRST RESULTS AND IMPLICATIONS FOR PEGMATITE PETROGENESIS

Iron-Mn phosphate minerals are common accessory phases in pegmatites, some granites and, rarely, in some hydrothermal quartz-rich dikes. A comprehensive textural and geochemical characterization of primary phosphate minerals belonging to the triplite-zwieselite, triphylite-lithiophilite, and graftonite-beusite series has been done. Chemical data, including major and trace elements contents, have been obtained by electron microprobe (EMP) and laser-ablation inductively coupled-plasma mass-spectrometry (LA-ICP-MS) techniques. The concentration of trace elements shows important differences for the three series of primary Fe-Mn phosphate minerals. Members of the triphylite-lithiophilite series are the poorest in trace elements, with Zn as the only element that may occur in important amounts. This low concentration in trace elements could be related to structural constrains. Graftonite-beusite members are the richest in REE, most probably due to the substitution of Ca by the rare earths. Members of the triplite-zwieselite series are the richest in certain HFSE, such as Nb and Ta. There is an important difference in the shape of multi-element diagrams of triplite-zwieselite samples associated with pegmatites, all of them showing a strong negative Eu anomaly, and those of samples from a quartz-rich dike, with no Eu anomaly. This difference is interpreted as the result of the Eu fractionation in pegmatites due to the previous crystallization of plagioclase. No correlation has been found between the Fe/(Fe+Mn) ratio and the different trace element contents of the primary phosphate series. Moreover, the concentrations of trace elements are not simply related to the pegmatite type, its paragenesis or its geological setting. Further investigation of mineral association, textural relationships, partition coefficients, and geology and history of crystallization of the pegmatitic bodies appears necessary in order to determine the factors controlling the variability in the trace elements content for the different primary phosphate series.

Ultrasensitive hybrid SERS substrate for rapid detection of trace chemicals

We demonstrate here a simple and effective approach for fabricating surface-enhanced Raman spectroscopy substrates by hybridizing Au films with silver particle clusters. A trace amount of aqueous chemical is dropped on the Au film covered substrate, followed by the addition of colloidal Ag nanoparticles (Ag NPs). The combination of Ag clusters and Au film promotes the enhancement ability of the substrate, as confirmed by a finite difference time domain simulation. The electromagnetic field tends to concentrate at the junctions between the Ag NPs and the flat Au film, and yields additional ‘hot spots’. The detect limitation of the hybrid substrate is 10 pM, with an enhancement factor about 1.5 × 107 when rhodamine 6G is employed as the probe molecule. The hybrid substrate showed good homogeneity, with a relative standard deviation about 10.7%. Moreover, the hybrid substrate is utilized for melamine detection with a detection limit of 10 nM (1.2 ppb). The simple procedure, high sensitivity, and good homogeneity make the hybrid substrate a promising tool for trace chemical detection.

Long-term particle measurements in Finnish Arctic: Part I – Chemical composition and trace metal solubility

Week-long total suspended particle filter samples collected between 1964 and 2010 from Kevo, Finland were analyzed for trace metals, soluble trace metals and major ions. Ion chromatography was used to measure major ions. Inductively coupled plasma mass spectrometry was used to measure the trace metal and soluble trace metal concentrations. Species of anthropogenic origin (V, Co, Cu, Ni, As, Cd, Pb, SO42−) have significantly higher concentrations compared with other Arctic locations. A clear seasonal trend with winter/spring maxima and summer minima is observed for most species, although it is less pronounced than those found in the high Arctic due to the relative proximity to Eurasian pollution sources. High concentrations of Cu (14.1 ng/m3), Ni (0.97 ng/m3), and Co (0.04 ng/m3) indicate the influence of non-ferrous metal smelters on the Kola Peninsula, although Cu unexpectedly did not correlate with Ni or Co. Ni and Co were highly correlated. Cu, Re, Tl, As, W, and V had high solubilities (61%–87%), Co and Ni had solubility's of ∼33%, and Pb had a solubility of 22.9%. The solubility of metals can help determine if the source is natural or anthropogenic. It also dictates the bioavailability of metals once introduced to the environment.

Nitric acid trihydrate nucleation and denitrification in the Arctic stratosphere

Abstract. Nitric acid trihydrate (NAT) particles in the polar stratosphere have been shown to be responsible for vertical redistribution of reactive nitrogen (NOy). Recent observations by Cloud–Aerosol Lidar with Orthogonal Polarization (CALIOP) aboard the CALIPSO satellite have been explained in terms of heterogeneous nucleation of NAT on foreign nuclei, revealing this to be an important formation pathway for the NAT particles. In state of the art global- or regional-scale models, heterogeneous NAT nucleation is currently simulated in a very coarse manner using a constant, saturation-independent nucleation rate. Here we present first simulations for the Arctic winter 2009/2010 applying a new saturation-dependent parametrisation of heterogeneous NAT nucleation rates within the Chemical Lagrangian Model of the Stratosphere (CLaMS). The simulation shows good agreement of chemical trace species with in situ and remote sensing observations. The simulated polar stratospheric cloud (PSC) optical properties agree much better with CALIOP observations than those simulated with a constant nucleation rate model. A comparison of the simulated particle size distributions with observations made using the Forward Scattering Spectrometer Probe (FSSP) aboard the high altitude research aircraft Geophysica, shows that the model reproduces the observed size distribution, except for the very largest particles above 15 μm diameter. The vertical NOy redistribution caused by the sedimentation of the NAT particles, in particular the denitrification and nitrification signals observed by the ACE-FTS satellite instrument and the in situ SIOUX instrument aboard the Geophysica, are reproduced by the improved model, and a small improvement with respect to the constant nucleation rate model is found.

Eolian contribution to geochemical and mineralogical characteristics of some soil types in Medvednica Mountain, Croatia

Six pedological profiles were analyzed above five typical lithological units in Medvednica Mountain to determine the effect of eolian additions to the soil composition, as well as the possible influence of relief, vegetation cover, and anthropogenic input on the dynamics of pedogenesis. Bedrock composition was defined using petrographic (thin sections) and chemical analyses (major and trace element contents), whereas pedological, sedimentological and geochemical characteristics of six cross-sections were determined by chemical (major and trace element contents), mineralogical (modal analysis), and grain size analysis. Soils developed on sedimentary bedrock (Mollic Rendzic Leptosols (Calcaric) and Albic Luvisol (Sceletic)) mostly originate from weathering of siliciclastic detritus that was exposed to oxidization before diagenesis. Furthermore, soils on metasiltstone, marble and Lithothamnium limestone exhibit similar modal and geochemical composition and element distribution across the soil profile. In contrast, soils developed on igneous bedrock originate mostly from weathering of minerals of the first weathering cycle and thus abound with chemically less resistant minerals and less mobile elements. However, all profiles contain higher concentrations of lead with respect to bedrock indicating airborne contamination.

Chemometric study of trace elements in hard coals of the upper Silesian Coal Basin, Poland.

The objective of the study was the analysis of trace elements contents in coals of the Upper Silesian Coal Basin (USCB), which may pose a potential threat to the environment when emitted from coal processing systems. Productive carbon overburden in central and southern zones of the USCB is composed mostly of insulating tertiary formations of a thickness from a few m to 1,100 m, and is represented by Miocene and Pliocene formations. In the data study the geological conditions of the coal seams of particular zones of the USCB were taken into account and the hierarchical clustering analysis was applied, which enabled the exploration of the dissimilarities between coal samples of various zones of the USCB in terms of basic physical and chemical parameters and trace elements contents. Coals of the northern and eastern zones of the USCB are characterized by high average Hg and low average Ba, Cr, and Ni contents, whereas coals of southern and western zones are unique due to high average concentrations of Ba, Co, Cu, Ni, and V. Coals of the central part of the USCB are characterized by the highest average concentration of Mn and the lowest average concentrations of As, Cd, Pb, V, and Zn.

Quantifying chemical weathering intensity and trace element release from two contrasting basalt profiles, Deccan Traps, India

Weathering profiles developed on basalt substrate contain information relevant to climate, atmospheric composition and evolution, nutrient release into the hydrosphere, and understanding Martian regolith. In this study, the chemical compositions of two profiles developed on Deccan Trap basalt are examined. One is sub-Recent and has only progressed to a moderate degree of alteration (Chhindwara profile), whereas the other is ancient (Paleocene) and the degree of alteration is extreme (Bidar laterite). In an attempt to better quantify the chemical changes during incipient to intermediate weathering of mafic substrates, a new index is proposed: the mafic index of alteration (MIA). Similar to the chemical index of alteration (CIA), the MIA quantifies the net loss of the mobile major elements (Ca, Mg, Na, K±Fe) relative to the immobile major elements (Al±Fe). The redox-dependent weathering behaviour of Fe is factored into two separate arrangements of the MIA that apply to oxidative [MIA(O)] or reduced [MIA(R)] weathering. The MIA can be visualised in a variety of ternary diagrams in the Al–Fe–Mg–Ca–Na–K system. To chemically quantify the stages of advanced to extreme weathering, at which the MIA and CIA are ineffective, the SiO2 to (Al2O3+Fe2O3) mass ratio, based on the established Si–Al–Fe (SAF) ‘laterite’ ternary diagram, is used; we propose that this ratio be referred to as the ‘index of lateritisation’ (IOL).Major element chemical variations, as expressed by weathering indices, are used to relate the extent of weathering with the behaviour of trace elements (alkali, alkaline earth, rare earth, and Nb) in the profiles. During the early stages of basalt weathering, the mobile trace elements (Sr, Be, Li) are anti-correlated with the chemical weathering indices and thus released during these stages. By contrast, the monovalent elements (K, Rb, Cs, Tl), excluding Na and Li, appear to be associated with the pedogenetic clay minerals. Of these elements, those with the most similar ionic radii are closely related in their weathering behaviour. Fractionation of the REE (Sm/Nd, Eu/Eu*, Ce/Ce*) is evident during weathering of the basalt. The loss of Eu is linked with that of Sr, Ca, and Na and thus associated with plagioclase dissolution during the stages of incipient to intermediate weathering. The fractionation of Sm/Nd suggests that basaltic weathering products may not always preserve their parent rock ratio and, consequently, their Nd isotope composition over time.Finally, weathering in the sub-Recent profile is shown to have progressed across two lava flows, whose morphology initially controlled the extent of weathering. Certain compositional variations in the original flows (e.g., immobile element ratios) are preserved through the effects of chemical weathering and have the potential to influence mass balance calculations across the entire profile.

Towards zero vision. The possibilities and challenges for accident prevention in the Danish oil and gas industry

The major and minor chemicals observed in the modern atmosphere, which consists of the troposphere, stratosphere, mesosphere and above, are discussed. Trace chemicals observed in the troposphere and stratosphere are then described. Finally, greenhouse gases and toxic chemicals are discussed. Typical values are tabulated for atmospheric chemical modeling purposes.

Geochronology and trace element geochemistry of zircon, monazite and garnet from the garnetite and/or associated other high-grade rocks: Implications for Palaeoproterozoic tectonothermal evolution of the Khondalite Belt, North China Craton

It is well documented that the Khondalite Belt of the North China Craton formed by the collision of the Yinshan and Ordos Blocks during ca. 1.95Ga, but the onset of the post-collisional exhumation stage has not been well dated. The garnetite and garnet-bearing quartz-rich lens that are regarded as residue-melt phases occur occasionally in the foliated metasedimentary rocks in the Jining terrane of the Khondalite Belt. They are free of regional gneissosity, and may be generated during the post-collisional exhumation stage. Zircon U–Pb dating, monazite chemical dating and trace element analyses of zircon, monazite and garnet have been carried out on the garnetites and associated other high-grade metamorphic rocks. The geochronological results reveal a major age group of ca. 1890Ma from the zircon grains/overgrowths and inclusion-type monazites within the garnet poikiloblasts in the garnetites. The trace elements analyses show that zircon hosted in the mantle of the garnet poikiloblasts in the garnetite contains the highest HREE and Y contents, whereas zircon hosted in the garnet rims shows higher HREE and Y contents than matrix zircon grains. Inclusion-type monazite in the garnetite shows higher LaN/SmN ratio than matrix monazite grains. Large garnet poikiloblasts in the garnetite exhibit bell-shaped HREE and Y zoning profiles attributed to Rayleigh fractionation during their growth. Compared to garnet poikiloblasts, coronal garnet shows higher Gro, Cr and Li contents, but lower XMg, Sm, HREE, Zn and Zr contents and weaker Eu negative anomalies, reflecting their different formation environments. Based on evidences from microstructural analyses, REE concentrations and patterns, HREE partition coefficients and the Ti-in-zircon thermometer, it is proposed that most of the zircon grains/overgrowths in the garnetite formed coevally with garnet poikiloblasts. Consequently, ca. 1890Ma represents the timing of garnet poikiloblast growth during the partial melting of the protolith. Coronal garnet or Zn-rich spinel plus cordierite coupled with the matrix-type monazite formed after garnet poikiloblasts growth during near-isothermal decompression. Given the high metamorphic temperature and pressure revealed by the garnetite (820–850°C and up to 950°C; 8.5–9.5kbar), it is suggested that the ca. 1890Ma age group represents the beginning of extension/exhumation event in the Khondalite Belt, which is also recorded in the associated other high-grade rocks such as the garnet-bearing quartz-rich lenses, sillimanite–garnet-bearing quartzo-feldspathic gneisses, garnet-bearing quartzo-feldspathic gneisses and a pure quartz vein.

Characteristics of TSP Loads during the Middle East Springtime Dust Storm (MESDS) in Western Iran

Dust storm is one of the most important environmental problems in the west of Iran. To indicate the environmental impact of these phenomena, the characterization of dust storm loads is vital. The objective of this study is to identify the mineralogical and chemical composition, trace elements, and microorganisms of dust particles deposited during a springtime dust storm event over the west of Iran to obtain total suspended particulate. Dust samples were collected from four cities in the west of Iran during dust storms in two spring seasons of 2011 and 2012. In addition to determining the sources of dust samples on the dates of sampling, synthetic approaches including remote sensing technique of dust detection, physical–meteorological model called HYSPLIT, and analysis of weather map were used. XRD analyses of airborne dust samples indicate that the mineralogy of airborne dusts is dominated by calcite and quartz; additionally, gypsum, albeit, muscovite, clinochlore, and dolomite are other minerals in springtime dust storm. XRF analyses indicate that the most important chemical components of airborne dusts are SiO2, CaO, Al2O3, Fe2O3, and MgO. The Atomic Absorption analysis was performed to determine the concentration of heavy metals including Fe, Cr, Pb, Zn, Cd, Co, Cu, and Ni. Concentration of heavy metals was Fe > Zn > Cr > Ni > Pb > Cu > Co > Cd, respectively, and average concentration of heavy metals on Middle East springtime dust storm (MESDS) occurrences were higher than values proposed by the World Health Organization. Microorganism analysis shows that the Bacillus species (41.25 %) is dominant, then Micrococcus (10.3 %), Staphylococcus sp. (7.61 %), Klebsiella (4 %), Escherichia coli (2.7 %), and Enterobacter sp. (1.8 %); Aspergillus sp. (21.07 %), Candida albicans (5.7 %), Rhizopus (2.24 %), Penicillium sp. (1.04 %), and Mucor (0.89 %) genera were fungal species that were isolated in the (MESDS). Basic sources for scattering of dust in the west and southwest of Iran are Iraqi desert, desert lands in the north and northeast of Arabian Peninsula, east and southeast of Syria, also occasionally Sahara desert and Khuzestan province in southwestern of Iran.

The Chemistry CATT-BRAMS model (CCATT-BRAMS 4.5): a regional atmospheric model system for integrated air quality and weather forecasting and research

Abstract. Coupled Chemistry Aerosol-Tracer Transport model to the Brazilian developments on the Regional Atmospheric Modeling System (CCATT-BRAMS, version 4.5) is an on-line regional chemical transport model designed for local and regional studies of atmospheric chemistry from the surface to the lower stratosphere suitable both for operational and research purposes. It includes gaseous/aqueous chemistry, photochemistry, scavenging and dry deposition. The CCATT-BRAMS model takes advantage of BRAMS-specific development for the tropics/subtropics as well as the recent availability of preprocessing tools for chemical mechanisms and fast codes for photolysis rates. BRAMS includes state-of-the-art physical parameterizations and dynamic formulations to simulate atmospheric circulations down to the meter. This on-line coupling of meteorology and chemistry allows the system to be used for simultaneous weather and chemical composition forecasts as well as potential feedback between the two. The entire system is made of three preprocessing software tools for user-defined chemical mechanisms, aerosol and trace gas emissions fields and the interpolation of initial and boundary conditions for meteorology and chemistry. In this paper, the model description is provided along with the evaluations performed by using observational data obtained from ground-based stations, instruments aboard aircrafts and retrieval from space remote sensing. The evaluation accounts for model applications at different scales from megacities and the Amazon Basin up to the intercontinental region of the Southern Hemisphere.