Step Sequential Extraction Research Articles

Arsenic speciation in marine sediments: A comparison between two sequential extraction procedures

ABSTRACTArsenic distribution and mobility in marine sediments was investigated by means of total extraction and two sequential extraction procedures i.e. a modified sequential extraction procedure proposed by the European Standard, Measurementand Testing (SM&T) program, formerly the Community Bureau of Reference (BCR) procedure and a five steps sequential extraction based on the Wenzel extraction procedure, called modified Wenzel extraction. Sediments were collected from Cagliari’s harbour and Cagliari’s gulf, in Western Mediterranean Sea, Italy. The modified Wenzel extraction provided a more detailed As binding pattern and turned out to be much more appropriate than the modified SM&T procedure for gaining information regarding the mobilization of As within marine sediments. In the harbour, the largest part of As is contained in the residual fraction. At the contrary, As concentration, which is higher in the Cagliari’s gulf, is primarily associated with amorphous and crystalline hydrous Fe(Mn, Al) oxide. Moreover, this study suggests the possibility to segregate different types of marine sediments depending of human or industrial activities and to trace As contaminated marine sediments to determine the origin of contamination following the percentile of As contained in each extraction steps.

Trace metals distribution in different geochemical phases of soils around automobile junk markets in southern Nigeria

Chemical forms of some trace metals in soils around some selected automobile junk markets were studied using five step sequential extraction procedure. The results revealed that nickel, chromium and iron were of lithogenic origin while copper, lead, manganese and cadmium were from anthropogenic sources. The residual fraction was the most important phase for nickel, chromium and iron with the average amounts of 20.38%, 29.93% and 31.09% respectively. Copper and lead were mainly associated with the organic fraction having the average amounts of 24.06% and 22.89% respectively. Manganese predominated in Iron-Manganese oxide phase with an average amount of 23.76% while cadmium existed mainly in the exchangeable phase with an average amount of 30.36%. These results suggest that nickel, chromium and iron cannot be mobilized while cadmium is the most mobile and is easily available for plant uptake. Lead, manganese and copper are relatively stable but may become mobile if there are changes in soil pH or redox potential. The amounts of the metals in the non exchangeable phases were generally high but with relative high mobility factor values obtained for all the metals, changes in the soils physicochemical conditions may lead to remobilization of the metals and they may become bioavailable to plants and may enter food chain which implies a contamination risk for the metals.Keywords: Automobile junks, geochemical phases, sequential extraction, soil pollution, trace metals

Improvement of the sequential extraction procedure based on supercritical CO2 and subcritical H2O solvents for the estimation of the environmentally mobile potentially toxic element fractions of sediments and soils

The estimation of environmental risk caused by pollution with potentially toxic elements (PTE) is usually carried out using the (3+1) step sequential extraction procedure suggested in 1993 by the Community Bureau of Reference (BCR). In the 1st step the water-soluble, exchangeable and carbonate-bound element content is extracted with acetic acid. In 2002 a fractionation procedure based on the application of supercritical CO2, subcritical H2O and of a mixture of subcritical H2O/CO2 was proposed, which allowed the water-soluble and carbonatebound element contents to be extracted separately from sediment or soil samples weighed into the preparative column of a supercritical fluid extractor and diluted with quartz sand in a mass ratio of 1:20. The aim of the present study was to develop a new reduced-size column construction with which this dilution rate could be decreased to 1:2. A kinetic study was performed to determine the extraction time necessary for samples with different carbonate contents and the extracted element contents were compared to the results of the BCR sequential procedure on the same samples. It was established that fractionation using the reduced-size column may be a rapid way to obtain more reliable information on the easily mobilizable (watersoluble and carbonate-bound) PTE content of soils and sediments than was previously available to supplement BCR fractionation.

Changes and Distribution of Modes of Occurrence of Seventeen Potentially-Hazardous Trace Elements during Entrained Flow Gasification of Coals from Ningdong, China

In order to reveal the migration of trace elements from coal to gasification residues, the modes of occurrence of potentially-hazardous trace elements (Be, V, Cr, Co, Ni, Cu, Zn, As, Se, Mo, Cd, Sb, Ba, Hg, Tl, Pb, and U) were determined by a five steps sequential chemical extraction procedure. Samples were collected from a coal-to-methanol plant (GE water-slurry coal gasification, formerly Texaco) and a coal-to-olefins plant (Gaskombimat Schwarze Pumpe pulverized coal gasification, GSP) in the Ningdong Energy and Chemical Industry Base, China. Concentrations of As and Se were determined using atomic fluorescence spectrometry (AFS). The content of Hg was determined using a DMA-80 mercury analyzer. Other trace elements (Be, Cr, Co, Ni, Cu, Zn, Mo, Cd, Sb, Ba, Tl, Pb, and U) were analyzed using inductively-coupled plasma mass spectrometry (ICP-MS). XRD and SEM-EDX were employed to determine the minerals or other inorganic phases in samples. The modes of occurrence of trace elements in feed coals can influence their behavior, including their volatility during coal gasification and, ultimately, the element’s mode of occurrence in the gasification residues. Knowing an element’s mode of occurrence in the feed coal may aid in anticipating which components the elements are likely to combine with during liquid slag cooling. Based on the relative enrichment of trace elements in the residues, elements Be, V, Cu, Mo, Ba, and Hg showed volatility during the GE and GSP gasification processes; As and Se showed volatilization-condensation behavior during the GE and GSP gasification processes; Cr, Ni, Zn, Cd, Sb, Tl, Pb, and U showed volatility during the GE gasification process; Zn, Cd, Sb, Pb, and Tl in the GSP samples, as well as Co in the GE samples, showed volatilization-condensation behavior; and Cr, Co, Ni, and U showed less volatility during the GSP gasification process. In the gasification residues, quartz, calcite, and Al–Si glass were the main inorganic phases, carbonates and iron and manganese oxides (likely recrystallized calcite) were the main hosts of most trace elements in the residues, including Be, V, Cr, Co, Ni, Zn, As, Cd, Ba, Hg, Tl, Pb, and U. Copper, Zn, Se, Cd, and Sb tended to stay in the Al–Si glass. Molybdenum is likely precipitated with the sulfides in the residues.

Environmentally friendly microwave-assisted sequential extraction method followed by ICP-OES and ion-chromatographic analysis for rapid determination of sulphur forms in coal samples

A rapid three-step sequential extraction method was developed under microwave radiation followed by inductively coupled plasma-optical emission spectroscopic (ICP-OES) and ion-chromatographic (IC) analysis for the determination of sulphur forms in coal samples. The experimental conditions of the proposed microwave-assisted sequential extraction (MW-ASE) procedure were optimized by using multivariate mathematical tools. Pareto charts generated from 23 full factorial design showed that, extraction time has insignificant effect on the extraction of sulphur species, therefore, all the sequential extraction steps were performed for 5 min. The optimum values according to the central composite designs and counter plots of the response surface methodology were 200 °C (microwave temperature) and 0.1 g (coal amount) for all the investigated extracting reagents (H2O, HCl and HNO3). When the optimum conditions of the proposed MW-ASE procedure were applied in coal CRMs, SARM 18 showed more organic sulphur (72%) and the other two coal CRMs (SARMs 19 and 20) were dominated by sulphide sulphur species (52–58%). The sum of the sulphur forms from the sequential extraction steps have shown consistent agreement (95–96%) with certified total sulphur values on the coal CRM certificates. This correlation, in addition to the good precision (1.7%) achieved by the proposed procedure, suggests that the sequential extraction method is reliable, accurate and reproducible. To safe-guard the destruction of pyritic and organic sulphur forms in extraction step 1, water was used instead of HCl. Additionally, the notorious acidic mixture (HCl/HNO3/HF) was replaced by greener reagent (H2O2) in the last extraction step. Therefore, the proposed MW-ASE method can be applied in routine laboratories for the determination of sulphur forms in coal and coal related matrices.

Chemical Fractionation of Aluminium in the Sediments of El-Burullus Lagoon of Nile Delta, Egypt

A five step sequential extraction technique, following Tessier’s protocol has been applied to determine the chemical association of aluminium with major sedimentary phases (exchangeable, carbonate, manganese and iron oxides, organic and residual fraction) in four short sediment cores collected from El-Burullus lagoon of the Nile delta, Egypt. This study is a first approach of chemical fractionation of aluminium in one of the protective areas of the Mediterranean Sea of Egypt. The total metal content was also determined. The results of the fractionation study indicated that aluminium was mainly associated with the residual fraction (>95%). The organic and Fe–Mn oxide fractions were the next important phases. The exchangeable and carbonate fractions were less than 1%, limiting its potential toxicity as a pollutant. The geochemical analysis of aluminium forms reflected the lithogenic origin of this metal in the study area.

Ranking and similarity of conventional, microwave and ultrasound element sequential extraction methods

This study aims to compare three extraction techniques of four sequential element extraction steps from soil and sediment samples that were taken from the location of the Pančevo petrochemical industry (Serbia). Elements were extracted using three different techniques: conventional, microwave and ultrasound extraction. A novel procedure – sum of the ranking differences (SRD) – was able to rank the techniques and elements, to see whether this method is a suitable tool to reveal the similarities and dissimilarities in element extraction techniques, provided that a proper ranking reference is available. The concentrations of the following elements Al, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Si, Sn, Sr, V and Zn were determined through ICP OES. The different efficiencies and recovery values of element concentrations using each of the three extraction techniques were examined by the CRM BCR-701. By using SRD, we obtained a better separation between the different extraction techniques and steps when we rank their differences among the samples while lower separation was obtained according to analysed elements. Appling this method for ordering the elements could be useful for three purposes: (i) to find possible associations among the elements; (ii) to find possible elements that have outlier concentrations or (iii) detect differences in geochemical origin or behaviour of elements. Cross-validation of the SRD values in combination with cluster and principal component analysis revealed the same groups of extraction steps and techniques.

Geochemical and environmental risk assessment of hazardous elements in river sediment

The peninsular river Damodar is the life line of eastern India, facing critical pollution problems due to sewage, industrial waste disposal as well as coal mining along the river valley. Sediment samples were collected and analyzed for various geochemical phases of hazardous elements, and associated environmental risks were evaluated. This paper provides chemical fractionation of nine (Cd, Mn, Zn, Ni, Cu, Pb, Co, Cr, Fe) elements from river sediment by using Tessier five step sequential extraction method. The study was aimed (1) to understand dynamics and mobility of elements in different geochemical fractions; (2) to evaluate bioavailability and ecological risk of these elements by RAC; and (3) to identify contaminated and uncontaminated sites by using cluster analysis. The result of the study revealed maximum bioavailable fraction was that of Cd. Bioavailable elements in studied sediment followed the order Cd (23.76%) > Mn (14.19%) > Zn (13.54%) > Ni (12.82%) > Cu (7.12%) > Pb (7.05%) > Co (6.09%) > Fe (4.98%) > Cr (2.03%). Maximum % of the reducible fraction was found for Fe (14.38%) while in organic fraction Cu (11.25%) was maximum. Residual fraction dominates in all elements with a maximum percentage of 83.85% for Co. Risk assessment by RAC reveals that the river was under medium risk due to Cd, Mn, Zn and Ni while at low risk for rest of the elements. Cluster analysis shows that three sampling sites were highly contaminated, three were moderately contaminated and six were contaminated while only one site was uncontaminated.

Molybdenum-phosphate retention and transport in soils

Transport and retention experiments were carried out to quantify the mobility and sorption of molybdenum (Mo) and phosphate (P) in two different soils. Batch experiment was used to determine sorption isotherms over a wide range of concentrations for Mo and P. For both soils, sorption isotherms were nonlinear with higher affinity of P than Mo. Sorption of Mo was significantly reduced as the amount added P in solution increased. This was observed for both soils and is indicative of competitive sorption for available site. Miscible-displacement experiments were carried out using soil column where a pulse of Mo solution was introduced in each soil. Breakthrough curves (BTCs) indicated extensive sorption of Mo where as much as 50% of that applied was retained by a predominant kaolinatic soil. Subsequently, a pulse of mixed solution (of Mo and P) was introduced in each column. Results of BTCs for Mo indicated enhanced mobility of Mo in the presence of P for both soils. A five step sequential extraction procedure provided evidence that majority of applied Mo was strongly and/or irreversibly retained. A competitive transport model (CMRTM) based on the Sheindorf-Rebhun-Sheintuch (SRS) equation was capable of describing BTCs of Mo and to a lesser extent for P. Future research should focus on improvement of models that accounts for chemical mechanisms of competitive sorption.

Profil Fraksi Geokimia Logam Cd, Pb dan Zn pada Sedimen Wilayah Reklamasi Lumpur Sidoarjo di Muara Sungai Porong Sidoarjo

Sediments of Porong River estuary suspected of containing a high concentration of heavy metals. the Sediment sample was collected from Porong Estuary river at two different location. The purposes of this study to determine the distribution concentration of metals geochemical fraction (Cd, Pb and Zn) at sediment Porong River estuary and correlation Against Physico-chemical properties of sediments. Analysis of sediment includes determining the concentration of Cd, Pb and Zn and determining of physicochemical properties of sediments such as pH, salinity, redox potential, cation exchange capacity, organic materials and sediment particles size. Extraction Method performed by BCR (Community Bureau of Reference) three steps sequential extraction, where a geochemical fraction of metals divided to 4 fractions, such acid soluble, reducible, oxidized and residual fractions. Research showed Zn has the highest concentration of each fraction and followed by Pb and Cd. Concentration of Zn in Fraction 1-4 ranged from 31,909 – 84,966 mg/Kg, Pb concentrations range 3,354 – 18,956 mg/Kg, whereas Cd concentrations range between 0,221 – 0,611 mg/Kg. The order of metals geochemical fraction concentration at Fraction 1, 2, 3 and 4 is Zn>Pb>Cd. There is some correlation between metals concentration against physicochemical properties of sediment. Where the physicochemical properties of sediment influence heavy metal content and concentration in the sediment of Porong River Sidoarjo.

沉积物磷形态分析的固体浓度效应

以渤海埕岛油田区沉积物样品为例，探讨沉积物无机P形态分析过程中的固体浓度效应。4步顺序提取不同固体浓度(0.1 g/50 mL和0.2 g/50 mL)沉积物中的无机P，结果表明：沉积物中HCl-P含量最高，其次为BD-P和OH-P，含量最少的是loosely-P；沉积物磷形态分析过程中存在显著的固体浓度效应，表现为随着沉积物固体浓度增大，测得各形态P含量减少；沉积物中不同形态P受固体浓度的影响程度不同，强碱或强酸作为提取剂能有效抑制固体浓度效应，但不能完全消除。 We performed inorganic phosphorus (P) fractionation experiments of the sediments sampled from Chengdao oil field of Bohai, to explore the solid concentration effect on the process of sediments inorganic P fractionation. Four steps sequential extraction of inorganic P from sediments with different solid concentrations (0.1 g/50 mL and 0.2 g/50 mL) were done. The results showed that: the highest content in sediment is HCl-P, followed by BD-P and OH-P, and the least is loosely-P; the P components content decreased by the increased solid concentration, which confirmed solid concentration effect have influences on the processes of sediments inorganic P fractionation; the degree of impact of solid concentration effect on different P components is not equivalent. Strong acids or alkali can effectively inhibit this impact, but cannot counteract it thoroughly.

Mobility, Ecological risk and change in surface morphology during sequential chemical extraction of heavy metals in fly ash: A case study

Abstract Patratu coal based thermal power plant of Jharkhand, India uses Gondwana coal and generates ≈ 0.259 metric tonnes of fly ash. Only 3% of fly ash produced is utilized and rest is dumped as slurry, in the slurry pond and in the low-lying areas of the nearby villages. This study was aimed to find the mobility of metals in the fly ash samples by sequential extraction as well as to evaluate the ecological risk of the fly ash. The transformation of surface morphology after each step of sequential extraction was also studied by SEM-EDX. The results revealed that 13% of Cd and 1% of Ni was water soluble 48% of Ni, 23% of Mn, and 7% of Cd were in exchangeable fraction. The proportion in carbonate bound fraction was Cd (32%), Cu (15%), Zn (12%), Mn (6%), and Ni (3%) of the total metal content. Whereas, the proportion in Fe–Mn oxide bound fraction was Fe (46%), Mn (14%), Zn (13%) and Ni (3%); in organic bound fraction was Pb (38%), Cu (33%), Zn (16%), Cr (15%), Ni (13%), Mn (7%), Fe (6%), and Cd (2%) and in residual fraction was Cr (85%), Pb (62%), Mn (50%), Zn (59%), Cu (44%), Fe (47%), and Cd (25%). Pollution load index of metals in fly ash was more than one. Ecological risk index was also above 600. These values signify high ecological and pollution risk of the fly ash due to presence of heavy metals. So, implementation of proper remediation techniques is necessary to reduce the ecological risk of the fly ash.

Chemical fraction, leachability, and bioaccessibility of heavy metals in contaminated soils, Northeast China.

Heavy metals in urban soils may pose risks to both urban environment and human health. However, only a fraction of heavy metals in soil is mobile and/or bioavailable for plant uptake and human ingestion. This study evaluates the chemical fraction and potential mobility and bioaccessibility of heavy metals (Cd, Cr, Cu, Pb, and Zn) in the contaminated urban topsoils from steel-industrial city (Anshan), Northeastern China. Chemical forms of heavy metals in soils are determined using Tessier sequential extraction technique. The toxicity characteristic leaching procedure (TCLP), ethylenediaminetetraacetic acid (EDTA), and US Pharmacopeia methodology (USPM) are used to determine the operationally defined potentially mobile and bioaccessible metal fractions, respectively. Sequential extraction results show that Cd has the highest percentage of exchangeable form, whereas Cr primarily exists in residual form. The non-residual fraction of heavy metals increases in the order of Cr < Cu < Pb < Zn < Cd. The leachability of heavy metals evaluated by TCLP test indicates that Cd, Zn, Cu, and Pb have much higher mobile than Cr. The bioavailability of heavy metals determined by EDTA extraction decreases in the order of Pb > Cu ≅ Zn > Cd > Cr. The order of bioaccessibility determined by USPM extraction is Pb = Cu > Zn > Cd > Cr. The Cr exhibits the lowest leachability and bioaccessibility among the investigated metals. The Pb has the highest bioaccessibility, indicating higher potential hazard for the human health. There are significant relationships between the EDTA- and USPM-extractable metals (Cd, Cu, Pb, and Zn) and the sum of first three steps of sequential extraction. Highly significant correlation is found between amounts of EDTA-extractable Cd, Cu, Pb, and Zn and USPM-extractable metals. The result suggests that EDTA extraction can be helpful to estimate the bioaccessibility of heavy metals for human ingestion. Introduction of mobile and human bioaccessible concentrations into risk assessments can give more realistic implications for urban environmental management.

Heavy metals Fractionation in Bagmati River Sediments, Nepal

The aim of this work was speciation of heavy metals on the level of the geochemical background; in bottom sediments of the Bagmati River in Kathmandu valley. The distribution and accumulation of heavy metals in the sediments of the Bagmati River were investigated. Sediment samples from six locations were collected and characterized for metals content (cadmium, lead, copper and zinc). The determination of extractable heavy metals such as, Cd, Pb, Cu and Zn, in the sediment samples was carried out by atomic absorption spectrometry. The study has been conducted using five steps sequential extraction procedure described by tessier. Apart from total concentration, the distribution of the above metals into five fractions: exchangeable, bound to carbonates, bound to Fe-Mn oxides, bound to organic matter, and residual, was studied by means of an analytical procedure involving sequential chemical extraction. The result obtained showed total metal concentration to be in the range of Cd 0.89-2.29 mg/kg; Pb 57.58-221mg/kg; Cu 52.2 -198.17 mg/kg and 78.23-362.90 mg/kg in all the areas studied. The fractionated toxic metals like Cd, and Pb were observed to be in the range of 15-36%, and 11- 29%, respectively, in mobile or bio-available fractions of sediments. This potentially mobile fraction could pose a serious threat, with respect to contamination of waterways and aquatic environment.Journal of Hydrology and Meteorology, Vol. 9(1) 2015, p.119-128

Determination of mercury and its fractionation products in samples from legacy use of mercury amalgam in gold processing in Randfontein, South Africa

Abstract This study aimed at determining the levels of total mercury (THg) in tailings dams, soil, sediments and water samples collected in the vicinity of legacy mercury amalgam gold mines. Acid digestion was employed in sample digestion followed by analysis using CVAAS. Tailings dams, community and garden soil, and stream sediments were further investigated for mercury fractions using a five step sequential extraction procedure. The concentrations of THg in tailings dams, community and gardens soil were 0.890–6.755 μg/g, 0.431–0.968 μg/g and 0.471–1.019 μg/g, respectively and the concentrations of THg in the sediments obtained from tailings dams, streams and wetlands were 0.649–1.998 μg/g, 0.604–1.356 μg/g and 0.681–1.356 μg/g, respectively. The concentrations of THg, in aqueous samples obtained from tailings, streams and wetlands were 0.032–0.070 μg/l, 0.004–0.068 μg/l and 0.007–0.012 μg/l, respectively. The sequential extraction procedure showed that most Hg in the tailings dams was largely elemental Hg and Hg bound to sulphur. Soil and sediments were largely dominated by organic bound Hg. Moderate seasonal correlation was observed in tailings dams soil, but weak seasonal correlation in soils collected in the vicinity of tailings. However, a strong seasonal correlation was observed in sediments and water samples. The concentrations of Hg obtained largely existed in organic and sulphate bound Hg and there is elevated potential to methylate Hg.

Sequential extraction procedure as a tool to investigate PTHE geochemistry and potential geoavailability of dam sediments (Almadén mining district, Spain)

Sediments from Castilseras reservoir (Almadén) were collected to assess the potential environmental hazards associated with the availability of Potentially Toxic or Harmful Elements (PTHE) in this freshwater environment. PTHE concentrations in sediments were investigated using a four step (F1–F4) Sequential Extraction Procedure (SEP) and the results were evaluated using Principal Component Analysis (PCA) and different risk indexes and criteria. Considering the fractions results and the PCA treatment, two groups of elements can be differentiated in the easily leached by weak acids fraction F1 and these indicate the presence of sulfate and secondary precipitates of carbonates as the main sink for easily accessible metallic elements. In reducible fraction F2, chemical analysis revealed a significant relationship between the majority of the analyzed elements and the Fe oxy-hydroxides, with the exception of Co, Hg and Ni, which are preferentially associated with Mn oxy-hydroxides. In the oxidizable fraction (F3), a significant relationship between Cu, Fe, Hg and Zn (representative metals of the existing ore deposits) and sulfides/organic matter was observed. The environmental assessment based on the aforementioned criteria provides risk levels varying from moderate to high. The risk appears to be higher near the dam, where the higher PTHE levels in sediment are due to a selective accumulation of fine-grained particles.

Exploiting biogeochemical and spectroscopic techniques to assess the geochemical distribution and release dynamics of chromium and lead in a contaminated floodplain soil

Scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX) combined with a seven steps sequential extraction technique were used to assess the geochemical distribution of chromium (Cr) and lead (Pb) in a contaminated floodplain soil. Total contents of Cr and Pb were 490.3 and 402.1 mg kg−1, respectively. The residual fraction was 59.5 and 56.3% of total Cr and Pb. The crystalline iron (Fe) oxide was the dominant non-residual fraction of Cr (35.9% of total Cr). Considerable amounts of Pb were found in the organic fraction (35.4%). Using 13C nuclear magnetic resonance spectroscopy, the soil organic matter was identified as 48.9% aromatic carbon, which indicated that a certain portion of Pb and Cr might be associated with aromatic compounds. The SEM–EDX images demonstrate a concomitant occurrence of Pb, manganese (Mn), Fe, and aluminum (Al) as well as a coexistence of Cr and Fe.The release dynamics of dissolved Cr and Pb as affected by redox potential (EH), pH, Fe, Mn, dissolved organic carbon, and sulfate was quantified using an automated biogeochemical microcosm apparatus. Soil pH decreased under oxic conditions. The release of Cr, Pb, Fe, and Mn increased under acidic oxic (pH = 3.7, EH = 521 mV) conditions due to the associated decrease of pH (7.1–3.7). The mobilization of Cr and Pb was affected by the Fe and Mn. In conclusion, our multi-technique approach identified the geochemical distribution of Cr and Pb and verified major factors that explain mobilization of Cr and Pb in floodplain soils.

Fractional Distribution of Heavy Metals in the Tailings of Itagunmodi Goldmine Site Osun State, Nigeria

The distribution of heavy metals (Cu, Ni, Cd, Cr, Zn and Fe) in goldmine tailing was determined using multi- step sequential extraction. Chemical properties such as pH, conductivity, cation exchange capacity, organic matter, residual humidity and particle size were also analyzed. Similar characteristics distribution patterns were observed for Cd, Cr, Fe and Zn except Cu. The percentage recovery of Ni ranged from 95.25-99.24%. The high Mobility factor and bioaccumulation factor values of soil Ni may be interpreted as symptoms of relatively high liability and biological availability of the metals in soil. Keywords: Tailings, Heavy Metals, Goldmine, Sequential Extraction, Distribution

Characterization of products of the early stages of pedogenesis in ornithogenic soil from Maritime Antarctica

SummaryLimited pedogenesis on the Antarctic continent results in unusual, but important, short‐range order inorganic phases and organo‐mineral complexes (both with broad peaks from X‐ray diffraction) in the clay fraction, which can be studied by sequential chemical extractions. We aimed to develop a better sequential extraction procedure to obtain more detailed discrimination of the short‐range order phases (SROP) of the clay fraction of soil from Maritime Antarctica. Selected chemical properties of the soil and clay fraction were related to different phases of these products. The total amount of SROP and organo‐mineral complexes in the clay fraction ranged from 15.1 to 43.9%, with greater occurrence in ornithogenic soil. The continuous incorporation of guano from penguins into the soil profile has contributed to increasing amounts of organo‐mineral complexes. Short‐range order phases have an important effect on soil chemical properties, such as an increase in non‐exchangeable acidity, quantity of hydroxyl groups on the surface of the colloidal fraction, the buffering capacity of Al3+ from non‐exchangeable and structural forms of the element, and a decrease in soil CEC. The greater number of sequential extraction steps enabled the separation of SROP and organo‐mineral complexes into two phases of stability, with a clear predominance of the more soluble forms.

Sequential Extraction of Petroleum Asphaltenes with Magnesium Oxide: A Method To Reduce Complexity and Improve Heteroatom Identity

Sequential extraction of an asphaltene sample with magnesium oxide nanoparticles provides an approach to remove selectively molecules from a complex fraction. This method of extraction relies, in part, on adsorption preferences for differing heteroatoms to leave weakly adsorbing sample constituents in a toluene solution. The extracted sample exhibits reduced complexity enabling more reliable identification of the remaining molecules in solution. Mass spectrometry (MS) data indicate a general bias for preferential removal of higher molecular weight species. This is supported by a shift in the average m/z ratio of the asphaltene distribution to lower m/z, as well as a decrease in the intensity observed for higher m/z ion signals, for higher extraction numbers. UV–vis absorption data corroborate MS data to provide an appreciable visual means to quantify sample uptake after several sequential extraction steps with MgO. Furthermore, both UV and MS data indicate a point of diminishing returns, after which subse...