An optimized selective sequential extraction(SSE)procedure was developed to assess the arsenic(As)partitioning in copper slag.The potential As species in copper slag are partitioned into the readily soluble As,dissolv...An optimized selective sequential extraction(SSE)procedure was developed to assess the arsenic(As)partitioning in copper slag.The potential As species in copper slag are partitioned into the readily soluble As,dissolvable arsenates,sparingly soluble arsenates,As residing in sulfides,arsenopyrite and metal As,as well as As incorporated into glassy silicates.The inductively coupled plasma atomic emission spectrometry(ICP-AES),scanning electronic microscopy(SEM),transmission electron microscope(TEM),X-ray diffractometry(XRD)and Fourier transform infrared spectroscopy(FTIR)were used to characterize the leachates and residues produced from the operation scheme.The selectivity and recovery of extractants were evaluated through single-phase extraction procedures.Partitioning data of As in slag samples show good agreement with the reported works and the total As recovery of each operation is over 90%.This suggests that the optimized SEE scheme can be reliably employed for As partitioning in As-bearing byproducts from copper smelting.展开更多
The heavy metal(such as Cr,Ni,Cu,Cd,Pb,and Zn)concentration,speciation,and pollution source in 43 sediment samples from the Xiangjiang River were investigated using sequential extraction combined with Pb isotope analy...The heavy metal(such as Cr,Ni,Cu,Cd,Pb,and Zn)concentration,speciation,and pollution source in 43 sediment samples from the Xiangjiang River were investigated using sequential extraction combined with Pb isotope analysis.Cu,Cd,Pb,and Zn concentrations are higher than their background values,while Cr and Ni concentrations are close to those.Sequential extraction demonstrates that heavy metals have different fractions,showing different bioavailabilities.The w(206Pb)/w(207Pb)ratio increases with decreasing bioavailability in the order of exchangeable<carbonate≈Fe-Mn oxides≈organic<residual(p<0.05).Wastewater,dust,and slag from mining and smelting areas,and the residual Pb are assumed to be the primary anthropogenic and natural sources of Pb,respectively.The percentages of anthropogenic Pb in the exchangeable,carbonate,Fe-Mn oxides,and organic fractions are(91.5±16.7)%,(61.1±13.9)%,(57.4±11.1)%,and(55.5±11.2)%,respectively,suggesting a significant input of anthropogenic Pb in these four fractions.展开更多
Since preparation and solubilization of protein samples are crucial factors in proteome research,the authors established a sequential extraction technique to prepare protein samples from the body wall of the 5th insta...Since preparation and solubilization of protein samples are crucial factors in proteome research,the authors established a sequential extraction technique to prepare protein samples from the body wall of the 5th instar larvae of silkworm.Bombyx mori.Two kinds of protein samples were obtained from the body wall using the method.Between the two types of samples only about 15% proteins were identical;the majority were different,indicating that more species of proteins could be obtained with the sequential extraction method;which will be useful for preparation of protein samples for proteome study.展开更多
A considerable amount of Hg is retained in flue gas desulfurization（FGD） gypsum from Wet Flue Gas Desulfurization（WFGD） systems. For this reason, it is important to determine the species of Hg in FGD gypsum not on...A considerable amount of Hg is retained in flue gas desulfurization（FGD） gypsum from Wet Flue Gas Desulfurization（WFGD） systems. For this reason, it is important to determine the species of Hg in FGD gypsum not only to understand the mechanism of Hg removal by WFGD systems but also to determine the final fate of Hg when FGD gypsum is disposed. In this study, Temperature Programmed Decomposition（TPD） and Sequential Chemical Extraction（SCE） were applied to FGD gypsum to identify the Hg species in it. The FGD gypsum samples were collected from seven coal-fired power plants in China, with Hg concentrations ranging from 0.19 to 3.27 μg/g. A series of pure Hg compounds were used as reference materials in TPD experiments and the results revealed that the decomposition temperatures of different Hg compounds increase in the order of Hg_2Cl_2〈 HgCl_2〈 black HgS 〈 Hg_2SO_4〈 red HgS 〈 HgO 〈 HgSO_4. The Hg compounds existing in FGD gypsums identified by TPD included HgCl_2, Hg_2Cl_2, Hg_2SO_4, black HgS and red HgS, of which mercury sulfides were the primary compounds. The results of SCE indicated that Hg was mainly distributed in the strongly complexed phase. The low Hg content in FGD gypsum increases the ambiguity of assigning extraction fractions to certain Hg species by SCE. The fact that the primary compounds in FGD gypsum are HgS phases leads the leaching of Hg in the natural environment to be quite low, but a considerable amount of Hg may be released during the industrial heating process.展开更多
Sequential extraction was performed on two oil sandstones from the Upper Carboniferous oil columns of TZ401 well. The free oils of these two oil sandstones and a crude oil from the Lower Carboniferous oil column of th...Sequential extraction was performed on two oil sandstones from the Upper Carboniferous oil columns of TZ401 well. The free oils of these two oil sandstones and a crude oil from the Lower Carboniferous oil column of this well have low ratios of C28/（C27 ＋ C28＋ C29） steranes and gammacerane/C31 hopanes, ranging of 0.11-0.16 and 0.09-0.15, respectively, similar to those from the Middle-Upper Ordovician source rock. However, these two ratios for the adsorbed and inclusion oils of these two oil sandstones are relatively high, ranging of 0.29-0.31 and 0.26-0.40, respectively, similar to those of the Cambrian-Lower Ordovician source rock. This result demonstrates that the initial oil charging the reservoirs was derived from the Cambrian-Lower Ordovician source rock, whereas the later charging oil was derived from the Middle-Upper Ordovician source rock.展开更多
The speciation of heavy metals such as thallium,cadmium and lead existing in pyrite and pyrite cinder was analyzed by ICP-MS with a sequential extraction procedure.The distribution patterns of these metals including e...The speciation of heavy metals such as thallium,cadmium and lead existing in pyrite and pyrite cinder was analyzed by ICP-MS with a sequential extraction procedure.The distribution patterns of these metals including exchangeable,reducible,oxidizable and residual fractions were obtained.Tl,Cd and Pb in pyrite and pyrite cinder samples from each extraction step were determined by inductively coupled plasma mass spectrometry(ICP-MS).Under the optimized instrumental conditions,detection limits of Tl,Cd and Pb in different matrices were within the range of 0.006-0.07 μg/L,and the relative standard deviations ranged from 0.8% to 1.2%.The accuracy of Tl,Cd and Pb determination was checked by analyzing two certified reference materials.The results demonstrate that trace Tl,Cd and Pb in the samples can be accurately determined.The sequential extraction results revealed that the percent contents of Tl,Cd and Pb in exchangeable,reducible and oxidizable fractions in pyrite cinder are different from those in pyrite and in pyrite cinder.Tl,Cd and Pb mostly are distributed in residual fraction.Therefore,the mobility of metals in pyrite is higher than that in pyrite cinder.Although distributions of Tl,Cd and Pb in the non-residual fraction are not dominant in pyrite cinder,the total concentrations of them could not be ignored.Consequently,attention must be paid to the risk of potential pollution by pyrite cinder.展开更多
Four types of undisturbed soil in Ain Oussera region around the Es-Salam reactor facility,located in the south of Algiers, Algeria, at about 200 km, were artificially contaminated for one year with stable CsCl and SrC...Four types of undisturbed soil in Ain Oussera region around the Es-Salam reactor facility,located in the south of Algiers, Algeria, at about 200 km, were artificially contaminated for one year with stable CsCl and SrCl2 in order to simulate an accidental release of these elements. This study was performed using sequential extraction procedure based on Shultz method and containing six fractions. The selectivity of the extraction protocol was confirmed by analyzing some elements（Ca, C, Fe, Mn, Si and Al） designed as indicators of the targeted phases. The obtained results showed an acceptable reproducibility, in view of the coefficients of variation that were in most cases less than 15%. The results revealed a clear proportional correlation between the extracted Cs and Sr in fractions for each soil and some of soils physicochemical properties. Organic matter appears to play an important role in the soil retention, particularly for Cs where the extracted percentage exceeds to 30% in whole soils. In contrast, strontium expresses a remarkable affinity for the fraction bound to carbonates. The obtained data also indicate that the availability of Cs in the four soils is less important compared to Sr availability. This is illustrated by the higher value of extracted Sr in the easily extractible phase, including the water-soluble and the exchangeable fraction.展开更多
A comprehensive<em> in vitro</em> study on single and sequential extraction methods for Cu exraction by different extractants of distinct chemical nature from some peat soils of Bangladesh was conducted to...A comprehensive<em> in vitro</em> study on single and sequential extraction methods for Cu exraction by different extractants of distinct chemical nature from some peat soils of Bangladesh was conducted to assess the pattern of metal-extractability in drying and wetting sequences. Samples were collected from peat basins of two different districts of Bangladesh (Gopalgonj and Bagerhat) and an incubation study was designed and conducted in which soils were incubated to three alternate drying and wetting cycles for 21 days. Single and sequentially extracted Cu ions in all three cycles and by all three selective extractants were compared. Maximum amount of Cu was extracted in drying days and 1M HCl extracted the largest proportion of Cu from all the soils in each incubation time. Conversely, 1M NH<sub>4</sub>Cl was the least effective extractant for extracting Cu by both single and sequential process in either day of incubation. Considerable amount of Cu was extracted by 0.005 M DTPA in dry periods. In general, single extraction was found to be more effective in extracting Cu in the alternate drying and wetting cycles from the peat soil samples except for 1M HCl in initial drying days.展开更多
Multistage sequential extraction with different sequences was applied to extracting natural surface coa tings（NSCs）, and the results were compared with those by single stage extraction technique. The optimal sequent...Multistage sequential extraction with different sequences was applied to extracting natural surface coa tings（NSCs）, and the results were compared with those by single stage extraction technique. The optimal sequential extraction scheme with the best performance was selected and incorporated into the method of selective extraction followed by adsorption and statistic analyses to study the adsorption parameters of Fe oxides, Mn oxides and organic matters in NSCs for Pb and Cd, to validate the applicability of the sequential extraction scheme. The Langmuir ad sorption parameters of each component of surface coating estimated according to the adsorption data of single stage extraction of NSCs were all similar to those of sequential extraction of NSCs, and the maximum difference between the metal adsorption abilities of the components estimated via the two extraction techniques was only about 20%, in dicating that either extraction techniques could be used. The optimal sequential extraction scheme obtained was first extracted with NH2OH·HCl, then with Na2S2O4, and finally with oxalic acid.展开更多
A short sequential extraction procedure（SSEP） was applied to the determination of more readily available metal fractions of Zn, Cu, and Cd in the riverbed sludge in Hejiagou, Harbin, China. From the results, a poten...A short sequential extraction procedure（SSEP） was applied to the determination of more readily available metal fractions of Zn, Cu, and Cd in the riverbed sludge in Hejiagou, Harbin, China. From the results, a potential order of metal availability in seven sludge samples was proposed： Cd 〈 Cu 〈 Zn, and samples S1 , S2, and S4 were used for the determination of total Zn content, and sample S3 used for the determination of total Cu content in the mobile and the mobilizable fractions showed the highest pollution risk. The results with regard to metal mobility in sludge samples were confirmed by the individual and global contamination factors that were calculated from the nonresidual and residual metal contents. The results obtained from metal-release experiments after exposure of sludge to environmental conditions agreed well with those obtained from both SSEP and the individual and global contamination factors, indicating that the maximum metal release could be an additional factor to evaluate the heavy metal availability in contaminated sludge. A substantial time saving was achieved by using the metal-release method in the present study.展开更多
Background: To evaluate the safety of immediate sequential bilateral cataract extraction (ISBCE) with respect to indications, visual outcomes, complications, benefits and disadvantages. Methods: This is a retrospectiv...Background: To evaluate the safety of immediate sequential bilateral cataract extraction (ISBCE) with respect to indications, visual outcomes, complications, benefits and disadvantages. Methods: This is a retrospective review of all ISBCEs performed at Kantonsspital Winterthur, Switzerland, between April 2000 and September 2013. The case notes of 500 eyes of 250 patients were reviewed. Of these 500 eyes, 472 (94.4%) had a straight forward phacoemulsification with posterior chamber intraocular lens implantation;21 (4.2%) had a planned extracapsular cataract extraction;4 (0.8%) had an intracapsular cataract extraction and 3 (0.6%) had a combined phacoemulsification with trabeculectomy. Results: Over 66% of eyes achieved improved visual acuity (at least 3 Snellen lines) following ISBCE. Median preoperative best corrected visual acuity (BCVA) was 0.5 LogMAR;the interquartile range was [0.4, 1] LogMAR. At one week control the median BCVA was 0.3 LogMAR, IQR [0.1, 0.5] LogMAR. At one month the median BCVA was 0.15 LogMAR, IQR [0.05, 0.3] (p < 0.01). There were no sight-threatening intraoperative or postoperative complications observed. Conclusions: ISBCE is an effective and safe option with high degree of patient satisfaction. The relative benefits of ISBCE should be balanced against the theoretically enhanced risks.展开更多
Sequential chemical extraction procedure has been widely used to partition particulate trace metals into various fractions and to describe the distribution and the statue of trace metals in geo environment. One sequen...Sequential chemical extraction procedure has been widely used to partition particulate trace metals into various fractions and to describe the distribution and the statue of trace metals in geo environment. One sequential chemical extraction procedure was employed here to partition various fractions of Mn in soils. The experiment was designed with quality controlling concept in order to show sampling and analytical error. Experimental results obtained on duplicate analysis of all soil samples demonstrated that the precision was less than 10%(at 95%confidence level). The accuracy was estimated by comparing the accepted total concentration of Mn in standard reference materials (SRMs) with the measured sum of the individual fractions. The recovery of Mn from SRM1 and SRM2 was 94.1%and 98.4%, respectively. The detection limit, accuracy and precision of the sequential chemical extraction procedure were discussed in detailed. All the results suggest that the trueness of the analytical method is satisfactory.展开更多
Geochemical behaviors of heavy metals are closely related to their chemical state that can be divided by sequential extraction into exchangeable(F1),bound to carbonates(F2),bound to Fe-Mn oxides(F3),bound to organic m...Geochemical behaviors of heavy metals are closely related to their chemical state that can be divided by sequential extraction into exchangeable(F1),bound to carbonates(F2),bound to Fe-Mn oxides(F3),bound to organic matter or sulfide(F4),and residual(F5).Uranium in sediment of the Huanghe(Yellow)River,China,in different chemical states was extracted using the five-step procedure of Tessier and the source and sink were analyzed.Results show that more than 70%of the total uranium was immobile residual F5 in abundance,followed in order of F4>F3>F2>F1,indicating that the main source of uranium in the sediments was from weathered rock in the drainage basin.In addition,the uranium in the sediments presents potential exogenous input in the Lanzhou,Baotou,and Tongguan reach.Fe-Mn oxides are main carriers of unstable uranium,especially those of F1 and F3.Calcite and illite are secondary adsorption minerals of unstable uranium in sediments under natural conditions.Human activities can also produce an obvious impact on uranium speciation.This study provides a reference for the application of sequential extraction in analyzing the source and sink of uranium in river sediments.展开更多
Soil is a major reservoir for heavy metals and other contamination as it possesses an ability to absorb these metals on the surface of clay minerals and bind various chemicals. These heavy metals and chemicals can exi...Soil is a major reservoir for heavy metals and other contamination as it possesses an ability to absorb these metals on the surface of clay minerals and bind various chemicals. These heavy metals and chemicals can exist in various forms in soil and different forces keep them bound to clay minerals and soil particles. The aim of the present work is to estimate the concentration levels of some heavy metals Zn, Cu, Pb and Cd in two sites of soil Kirkuk city. In this study the first sample was taken from inside the city of four areas around (Northern Oil Company) in Kirkuk city, while the second sample was taken from outside the city of four areas and both were randomly chosen. Sequential extraction procedure was applied to fractionate heavy metals which may help in the prediction of their mobility, bioavailability and fate of the metal contaminant. Results of sequential extraction showed that Cd and Pb were mainly bound to residual fraction, Cu was mainly bound to organic fraction and Zn was bound to Fe-Mn oxide fraction in the two sites of the study. The overall mean values obtained for the metals in the fractions gave the range: inside the city Cu (28.12 ppm), Zn (77.9 ppm), Pb (21.73 ppm) and Cd(4.21 ppm), and outside the city Cu (24.65 ppm), Zn (59.28 ppm), Pb (13.25 ppm) and Cd (2.38 ppm). The extracts were analyzed for heavy metal, using flameless-atomic absorption spectrophotometers (Flameless-AAS).展开更多
BACKGROUND Efficient extraction of nucleic acids and proteins(ENAP)from cells is a prerequisite for precise annotation of gene function,and has become laboratory routine for revealing the mysteries of life.However,cel...BACKGROUND Efficient extraction of nucleic acids and proteins(ENAP)from cells is a prerequisite for precise annotation of gene function,and has become laboratory routine for revealing the mysteries of life.However,cell samples are often from different culture dishes,resulting in inevitable experimental errors and sometimes poor repeatability.AIM To explore a method to improve the efficiency of ENAP,minimizing errors in ENAP processes,enhancing the reliability and repeatability of subsequent experimental results.METHODS A protocol for the sequential isolation of RNA,DNA,and proteins from the same cultured HepG2 cells using RNAzol reagent is presented here.The first step involves culturing HepG2 cells to the exponential phase,followed by the sequential isolation of RNA,DNA,and proteins from the same cultured cells in the second step.The yield of nucleic acids and proteins is detected in the third step,and their purity and integrity are verified in the last step.RESULTS The procedure takes as few as 3-4 d from the start to quality verification and is highly efficient.In contrast to the existing kits and reagents,which are primarily based on independent isolation,this RNAzol reagent-based method is characterized by the sequential isolation of RNA,DNA,and proteins from the same cells,and therefore saves time,and has low cost and high efficiency.CONCLUSION The RNA,DNA,and proteins isolated using this method can be used for reverse transcription-polymerase chain reaction,polymerase chain reaction,and western blotting,respectively.展开更多
In urban waste (the first matter of compost), elements such as copper, nickel and lead may be found in metallic state (wire, pile, accumulator, etc.), which is considered as non-dependent state. The work undertaken at...In urban waste (the first matter of compost), elements such as copper, nickel and lead may be found in metallic state (wire, pile, accumulator, etc.), which is considered as non-dependent state. The work undertaken at the laboratory of composting of the INRST in Henchir Lihoudia (Tunis) showed that the produced compost does not contain any mobile metallic element and the portion related to organic fraction (bioavailable) is tiny in size. We supposed that many reactions involving decomposition and complexation from elements related to the matrix components occurred during composting. The existence and importance of this phenomenon can be evaluated by studying the evolution of metal contents in the different fractions extracted sequentially during composting process.展开更多
为合理评价污染场地风险,以我国云南省某铜堆浸场下游农田土为例,测定土壤中Cu、Pb、Cd和As等4种重金属总量,采用改进BCR(Bureau of European Communities Reference)连续提取法测定4种重金属赋存形态,分析4种重金属间的相关性,并使用...为合理评价污染场地风险,以我国云南省某铜堆浸场下游农田土为例,测定土壤中Cu、Pb、Cd和As等4种重金属总量,采用改进BCR(Bureau of European Communities Reference)连续提取法测定4种重金属赋存形态,分析4种重金属间的相关性,并使用地累积指数法、次生相与原生相比值法(RSP)和风险评价编码法(RAC)对场地土壤重金属污染和潜在风险程度进行评价。结果发现,重金属Cu、Pb、Cd和As平均的含量分别为39.50、46.98、0.16、82.67mg⋅kg^(-1),较云南省重金属背景值,4种重金属超标率分别为0、83.33%、33.33%和100.00%,其中As污染需要特别关注;提取重金属赋存形态结果显示,土样中Cu、Pb、Cd和As均以残渣态为主,占比为83.14%~95.62%,表明4种重金属均以稳定形态存在于土体中;对比3种评价方法,评价结果存在明显差异,地累积指数Igeo结果显示土壤仅As存在污染超标现象,其余3种重金属均无污染,次生相与原生相比值法结果显示,4种重金属对环境均无污染,而风险评价编码法结果显示,Cd对土壤环境存在低风险,其余3种重金属则无风险。对比发现,仅以污染场地土壤重金属总量作为评价指标会一定程度夸大污染风险,应综合重金属总量及赋存形态含量进行分析。虽然重金属元素污染总量较高,但活跃性重金属含量非常低,向环境中扩散的风险也非常低。因此,研究区重金属污染程度较轻,潜在生态风险为低风险。展开更多
基金Projects(51874257,51374185,51801183)supported by the National Natural Science Foundation of China。
文摘An optimized selective sequential extraction(SSE)procedure was developed to assess the arsenic(As)partitioning in copper slag.The potential As species in copper slag are partitioned into the readily soluble As,dissolvable arsenates,sparingly soluble arsenates,As residing in sulfides,arsenopyrite and metal As,as well as As incorporated into glassy silicates.The inductively coupled plasma atomic emission spectrometry(ICP-AES),scanning electronic microscopy(SEM),transmission electron microscope(TEM),X-ray diffractometry(XRD)and Fourier transform infrared spectroscopy(FTIR)were used to characterize the leachates and residues produced from the operation scheme.The selectivity and recovery of extractants were evaluated through single-phase extraction procedures.Partitioning data of As in slag samples show good agreement with the reported works and the total As recovery of each operation is over 90%.This suggests that the optimized SEE scheme can be reliably employed for As partitioning in As-bearing byproducts from copper smelting.
基金Project(2009ZX07212-001)supported by the Major Science and Technology Program for Water Pollution Control and Treatment of ChinaProject(51079002)supported by the National Natural Science Foundation of China
文摘The heavy metal(such as Cr,Ni,Cu,Cd,Pb,and Zn)concentration,speciation,and pollution source in 43 sediment samples from the Xiangjiang River were investigated using sequential extraction combined with Pb isotope analysis.Cu,Cd,Pb,and Zn concentrations are higher than their background values,while Cr and Ni concentrations are close to those.Sequential extraction demonstrates that heavy metals have different fractions,showing different bioavailabilities.The w(206Pb)/w(207Pb)ratio increases with decreasing bioavailability in the order of exchangeable<carbonate≈Fe-Mn oxides≈organic<residual(p<0.05).Wastewater,dust,and slag from mining and smelting areas,and the residual Pb are assumed to be the primary anthropogenic and natural sources of Pb,respectively.The percentages of anthropogenic Pb in the exchangeable,carbonate,Fe-Mn oxides,and organic fractions are(91.5±16.7)%,(61.1±13.9)%,(57.4±11.1)%,and(55.5±11.2)%,respectively,suggesting a significant input of anthropogenic Pb in these four fractions.
文摘Since preparation and solubilization of protein samples are crucial factors in proteome research,the authors established a sequential extraction technique to prepare protein samples from the body wall of the 5th instar larvae of silkworm.Bombyx mori.Two kinds of protein samples were obtained from the body wall using the method.Between the two types of samples only about 15% proteins were identical;the majority were different,indicating that more species of proteins could be obtained with the sequential extraction method;which will be useful for preparation of protein samples for proteome study.
基金supported by the National Natural Science Foundation of China (No. 51376109)
文摘A considerable amount of Hg is retained in flue gas desulfurization（FGD） gypsum from Wet Flue Gas Desulfurization（WFGD） systems. For this reason, it is important to determine the species of Hg in FGD gypsum not only to understand the mechanism of Hg removal by WFGD systems but also to determine the final fate of Hg when FGD gypsum is disposed. In this study, Temperature Programmed Decomposition（TPD） and Sequential Chemical Extraction（SCE） were applied to FGD gypsum to identify the Hg species in it. The FGD gypsum samples were collected from seven coal-fired power plants in China, with Hg concentrations ranging from 0.19 to 3.27 μg/g. A series of pure Hg compounds were used as reference materials in TPD experiments and the results revealed that the decomposition temperatures of different Hg compounds increase in the order of Hg_2Cl_2〈 HgCl_2〈 black HgS 〈 Hg_2SO_4〈 red HgS 〈 HgO 〈 HgSO_4. The Hg compounds existing in FGD gypsums identified by TPD included HgCl_2, Hg_2Cl_2, Hg_2SO_4, black HgS and red HgS, of which mercury sulfides were the primary compounds. The results of SCE indicated that Hg was mainly distributed in the strongly complexed phase. The low Hg content in FGD gypsum increases the ambiguity of assigning extraction fractions to certain Hg species by SCE. The fact that the primary compounds in FGD gypsum are HgS phases leads the leaching of Hg in the natural environment to be quite low, but a considerable amount of Hg may be released during the industrial heating process.
基金supported by the National Basic Research Pro-gram of China (No. 2005CB422102)the National Natural Science Foundation of China (No. 40673014)
文摘Sequential extraction was performed on two oil sandstones from the Upper Carboniferous oil columns of TZ401 well. The free oils of these two oil sandstones and a crude oil from the Lower Carboniferous oil column of this well have low ratios of C28/（C27 ＋ C28＋ C29） steranes and gammacerane/C31 hopanes, ranging of 0.11-0.16 and 0.09-0.15, respectively, similar to those from the Middle-Upper Ordovician source rock. However, these two ratios for the adsorbed and inclusion oils of these two oil sandstones are relatively high, ranging of 0.29-0.31 and 0.26-0.40, respectively, similar to those of the Cambrian-Lower Ordovician source rock. This result demonstrates that the initial oil charging the reservoirs was derived from the Cambrian-Lower Ordovician source rock, whereas the later charging oil was derived from the Middle-Upper Ordovician source rock.
基金supported by the Union Foundation of NSFC-Guangdong Province (Grant No. U0633001)
文摘The speciation of heavy metals such as thallium,cadmium and lead existing in pyrite and pyrite cinder was analyzed by ICP-MS with a sequential extraction procedure.The distribution patterns of these metals including exchangeable,reducible,oxidizable and residual fractions were obtained.Tl,Cd and Pb in pyrite and pyrite cinder samples from each extraction step were determined by inductively coupled plasma mass spectrometry(ICP-MS).Under the optimized instrumental conditions,detection limits of Tl,Cd and Pb in different matrices were within the range of 0.006-0.07 μg/L,and the relative standard deviations ranged from 0.8% to 1.2%.The accuracy of Tl,Cd and Pb determination was checked by analyzing two certified reference materials.The results demonstrate that trace Tl,Cd and Pb in the samples can be accurately determined.The sequential extraction results revealed that the percent contents of Tl,Cd and Pb in exchangeable,reducible and oxidizable fractions in pyrite cinder are different from those in pyrite and in pyrite cinder.Tl,Cd and Pb mostly are distributed in residual fraction.Therefore,the mobility of metals in pyrite is higher than that in pyrite cinder.Although distributions of Tl,Cd and Pb in the non-residual fraction are not dominant in pyrite cinder,the total concentrations of them could not be ignored.Consequently,attention must be paid to the risk of potential pollution by pyrite cinder.
基金part of an internal project in Birine Nuclear Research Center(CRNB)and was supported by funding from the Algerian Atomic Energy Commission
文摘Four types of undisturbed soil in Ain Oussera region around the Es-Salam reactor facility,located in the south of Algiers, Algeria, at about 200 km, were artificially contaminated for one year with stable CsCl and SrCl2 in order to simulate an accidental release of these elements. This study was performed using sequential extraction procedure based on Shultz method and containing six fractions. The selectivity of the extraction protocol was confirmed by analyzing some elements（Ca, C, Fe, Mn, Si and Al） designed as indicators of the targeted phases. The obtained results showed an acceptable reproducibility, in view of the coefficients of variation that were in most cases less than 15%. The results revealed a clear proportional correlation between the extracted Cs and Sr in fractions for each soil and some of soils physicochemical properties. Organic matter appears to play an important role in the soil retention, particularly for Cs where the extracted percentage exceeds to 30% in whole soils. In contrast, strontium expresses a remarkable affinity for the fraction bound to carbonates. The obtained data also indicate that the availability of Cs in the four soils is less important compared to Sr availability. This is illustrated by the higher value of extracted Sr in the easily extractible phase, including the water-soluble and the exchangeable fraction.
文摘A comprehensive<em> in vitro</em> study on single and sequential extraction methods for Cu exraction by different extractants of distinct chemical nature from some peat soils of Bangladesh was conducted to assess the pattern of metal-extractability in drying and wetting sequences. Samples were collected from peat basins of two different districts of Bangladesh (Gopalgonj and Bagerhat) and an incubation study was designed and conducted in which soils were incubated to three alternate drying and wetting cycles for 21 days. Single and sequentially extracted Cu ions in all three cycles and by all three selective extractants were compared. Maximum amount of Cu was extracted in drying days and 1M HCl extracted the largest proportion of Cu from all the soils in each incubation time. Conversely, 1M NH<sub>4</sub>Cl was the least effective extractant for extracting Cu by both single and sequential process in either day of incubation. Considerable amount of Cu was extracted by 0.005 M DTPA in dry periods. In general, single extraction was found to be more effective in extracting Cu in the alternate drying and wetting cycles from the peat soil samples except for 1M HCl in initial drying days.
基金Supported by the National Natural Science Foundation of China(No.20877033)the Major Science and Technology Pro-gram for Water Pollution Control and Treatment, China(No.2009ZX07207-001-03)
文摘Multistage sequential extraction with different sequences was applied to extracting natural surface coa tings（NSCs）, and the results were compared with those by single stage extraction technique. The optimal sequential extraction scheme with the best performance was selected and incorporated into the method of selective extraction followed by adsorption and statistic analyses to study the adsorption parameters of Fe oxides, Mn oxides and organic matters in NSCs for Pb and Cd, to validate the applicability of the sequential extraction scheme. The Langmuir ad sorption parameters of each component of surface coating estimated according to the adsorption data of single stage extraction of NSCs were all similar to those of sequential extraction of NSCs, and the maximum difference between the metal adsorption abilities of the components estimated via the two extraction techniques was only about 20%, in dicating that either extraction techniques could be used. The optimal sequential extraction scheme obtained was first extracted with NH2OH·HCl, then with Na2S2O4, and finally with oxalic acid.
基金Supported by the National Key Basic Research Priorities Program of China(No. 2004CB3418501).
文摘A short sequential extraction procedure（SSEP） was applied to the determination of more readily available metal fractions of Zn, Cu, and Cd in the riverbed sludge in Hejiagou, Harbin, China. From the results, a potential order of metal availability in seven sludge samples was proposed： Cd 〈 Cu 〈 Zn, and samples S1 , S2, and S4 were used for the determination of total Zn content, and sample S3 used for the determination of total Cu content in the mobile and the mobilizable fractions showed the highest pollution risk. The results with regard to metal mobility in sludge samples were confirmed by the individual and global contamination factors that were calculated from the nonresidual and residual metal contents. The results obtained from metal-release experiments after exposure of sludge to environmental conditions agreed well with those obtained from both SSEP and the individual and global contamination factors, indicating that the maximum metal release could be an additional factor to evaluate the heavy metal availability in contaminated sludge. A substantial time saving was achieved by using the metal-release method in the present study.
文摘Background: To evaluate the safety of immediate sequential bilateral cataract extraction (ISBCE) with respect to indications, visual outcomes, complications, benefits and disadvantages. Methods: This is a retrospective review of all ISBCEs performed at Kantonsspital Winterthur, Switzerland, between April 2000 and September 2013. The case notes of 500 eyes of 250 patients were reviewed. Of these 500 eyes, 472 (94.4%) had a straight forward phacoemulsification with posterior chamber intraocular lens implantation;21 (4.2%) had a planned extracapsular cataract extraction;4 (0.8%) had an intracapsular cataract extraction and 3 (0.6%) had a combined phacoemulsification with trabeculectomy. Results: Over 66% of eyes achieved improved visual acuity (at least 3 Snellen lines) following ISBCE. Median preoperative best corrected visual acuity (BCVA) was 0.5 LogMAR;the interquartile range was [0.4, 1] LogMAR. At one week control the median BCVA was 0.3 LogMAR, IQR [0.1, 0.5] LogMAR. At one month the median BCVA was 0.15 LogMAR, IQR [0.05, 0.3] (p < 0.01). There were no sight-threatening intraoperative or postoperative complications observed. Conclusions: ISBCE is an effective and safe option with high degree of patient satisfaction. The relative benefits of ISBCE should be balanced against the theoretically enhanced risks.
文摘Sequential chemical extraction procedure has been widely used to partition particulate trace metals into various fractions and to describe the distribution and the statue of trace metals in geo environment. One sequential chemical extraction procedure was employed here to partition various fractions of Mn in soils. The experiment was designed with quality controlling concept in order to show sampling and analytical error. Experimental results obtained on duplicate analysis of all soil samples demonstrated that the precision was less than 10%(at 95%confidence level). The accuracy was estimated by comparing the accepted total concentration of Mn in standard reference materials (SRMs) with the measured sum of the individual fractions. The recovery of Mn from SRM1 and SRM2 was 94.1%and 98.4%, respectively. The detection limit, accuracy and precision of the sequential chemical extraction procedure were discussed in detailed. All the results suggest that the trueness of the analytical method is satisfactory.
基金Supported by the National Natural Science Foundation of China(Nos.41876077,41376085)。
文摘Geochemical behaviors of heavy metals are closely related to their chemical state that can be divided by sequential extraction into exchangeable(F1),bound to carbonates(F2),bound to Fe-Mn oxides(F3),bound to organic matter or sulfide(F4),and residual(F5).Uranium in sediment of the Huanghe(Yellow)River,China,in different chemical states was extracted using the five-step procedure of Tessier and the source and sink were analyzed.Results show that more than 70%of the total uranium was immobile residual F5 in abundance,followed in order of F4>F3>F2>F1,indicating that the main source of uranium in the sediments was from weathered rock in the drainage basin.In addition,the uranium in the sediments presents potential exogenous input in the Lanzhou,Baotou,and Tongguan reach.Fe-Mn oxides are main carriers of unstable uranium,especially those of F1 and F3.Calcite and illite are secondary adsorption minerals of unstable uranium in sediments under natural conditions.Human activities can also produce an obvious impact on uranium speciation.This study provides a reference for the application of sequential extraction in analyzing the source and sink of uranium in river sediments.
文摘Soil is a major reservoir for heavy metals and other contamination as it possesses an ability to absorb these metals on the surface of clay minerals and bind various chemicals. These heavy metals and chemicals can exist in various forms in soil and different forces keep them bound to clay minerals and soil particles. The aim of the present work is to estimate the concentration levels of some heavy metals Zn, Cu, Pb and Cd in two sites of soil Kirkuk city. In this study the first sample was taken from inside the city of four areas around (Northern Oil Company) in Kirkuk city, while the second sample was taken from outside the city of four areas and both were randomly chosen. Sequential extraction procedure was applied to fractionate heavy metals which may help in the prediction of their mobility, bioavailability and fate of the metal contaminant. Results of sequential extraction showed that Cd and Pb were mainly bound to residual fraction, Cu was mainly bound to organic fraction and Zn was bound to Fe-Mn oxide fraction in the two sites of the study. The overall mean values obtained for the metals in the fractions gave the range: inside the city Cu (28.12 ppm), Zn (77.9 ppm), Pb (21.73 ppm) and Cd(4.21 ppm), and outside the city Cu (24.65 ppm), Zn (59.28 ppm), Pb (13.25 ppm) and Cd (2.38 ppm). The extracts were analyzed for heavy metal, using flameless-atomic absorption spectrophotometers (Flameless-AAS).
基金Supported by the Postdoctoral Science Foundation of China,No.2005038300and the National Natural Science Foundation of China,No.30671028.
文摘BACKGROUND Efficient extraction of nucleic acids and proteins(ENAP)from cells is a prerequisite for precise annotation of gene function,and has become laboratory routine for revealing the mysteries of life.However,cell samples are often from different culture dishes,resulting in inevitable experimental errors and sometimes poor repeatability.AIM To explore a method to improve the efficiency of ENAP,minimizing errors in ENAP processes,enhancing the reliability and repeatability of subsequent experimental results.METHODS A protocol for the sequential isolation of RNA,DNA,and proteins from the same cultured HepG2 cells using RNAzol reagent is presented here.The first step involves culturing HepG2 cells to the exponential phase,followed by the sequential isolation of RNA,DNA,and proteins from the same cultured cells in the second step.The yield of nucleic acids and proteins is detected in the third step,and their purity and integrity are verified in the last step.RESULTS The procedure takes as few as 3-4 d from the start to quality verification and is highly efficient.In contrast to the existing kits and reagents,which are primarily based on independent isolation,this RNAzol reagent-based method is characterized by the sequential isolation of RNA,DNA,and proteins from the same cells,and therefore saves time,and has low cost and high efficiency.CONCLUSION The RNA,DNA,and proteins isolated using this method can be used for reverse transcription-polymerase chain reaction,polymerase chain reaction,and western blotting,respectively.
文摘In urban waste (the first matter of compost), elements such as copper, nickel and lead may be found in metallic state (wire, pile, accumulator, etc.), which is considered as non-dependent state. The work undertaken at the laboratory of composting of the INRST in Henchir Lihoudia (Tunis) showed that the produced compost does not contain any mobile metallic element and the portion related to organic fraction (bioavailable) is tiny in size. We supposed that many reactions involving decomposition and complexation from elements related to the matrix components occurred during composting. The existence and importance of this phenomenon can be evaluated by studying the evolution of metal contents in the different fractions extracted sequentially during composting process.
文摘为合理评价污染场地风险,以我国云南省某铜堆浸场下游农田土为例,测定土壤中Cu、Pb、Cd和As等4种重金属总量,采用改进BCR(Bureau of European Communities Reference)连续提取法测定4种重金属赋存形态,分析4种重金属间的相关性,并使用地累积指数法、次生相与原生相比值法(RSP)和风险评价编码法(RAC)对场地土壤重金属污染和潜在风险程度进行评价。结果发现,重金属Cu、Pb、Cd和As平均的含量分别为39.50、46.98、0.16、82.67mg⋅kg^(-1),较云南省重金属背景值,4种重金属超标率分别为0、83.33%、33.33%和100.00%,其中As污染需要特别关注;提取重金属赋存形态结果显示,土样中Cu、Pb、Cd和As均以残渣态为主,占比为83.14%~95.62%,表明4种重金属均以稳定形态存在于土体中;对比3种评价方法,评价结果存在明显差异,地累积指数Igeo结果显示土壤仅As存在污染超标现象,其余3种重金属均无污染,次生相与原生相比值法结果显示,4种重金属对环境均无污染,而风险评价编码法结果显示,Cd对土壤环境存在低风险,其余3种重金属则无风险。对比发现,仅以污染场地土壤重金属总量作为评价指标会一定程度夸大污染风险,应综合重金属总量及赋存形态含量进行分析。虽然重金属元素污染总量较高,但活跃性重金属含量非常低,向环境中扩散的风险也非常低。因此,研究区重金属污染程度较轻,潜在生态风险为低风险。
