Distribution of heavy metals in Lakes Doirani and Kerkini, Northern Greece

The distribution of heavy metals in two lakes of high ecological significance, Doirani and Kerkini, located in Northern Greece was studied. Eight metals (Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn) were determined in water, total suspended solids, fine and coarse sediments. Moreover, the modified BCR fractionation scheme was employed in sediments and suspended solids to determine soluble, oxidisable, reducible and residual fractions of metals. The Lake Doirani presents higher metal concentrations in aqueous phase than Lake Kerkini; Cd, Cu, Ni, Pb and Zn are above the chronic freshwater quality criteria for aquatic life. In both lakes, Fe and Mn are the most abundant elements in total suspended solids whereas Cd the less abundant. The Lake Kerkini exhibits higher concentrations of all the examined metals in sediments comparing to the Lake Doirani, however the concentrations are lower than the sediment quality guidelines. Cd in sediments is mainly in soluble fraction, Pb and Cu exhibit significant oxidisable fractions whereas, Cr and Fe associated mainly with residual fraction.     

Impact assessment of chromite mining on groundwater through simulation modeling study in Sukinda chromite mining area, Orissa, India

The pre-Cambrian chromites ore deposits in Sukinda valley, Jajpur District, Orissa, India, are well known for chromite ore deposits. The exploitation of the ore is carried out through open cast mining method since the last few decades. In the process, the overburden and ore dumps are stored on ground surface, where leaching of chromite and other toxic element takes place particularly during monsoon seasons. This leachate may cause threat to groundwater in the vicinity. An integrated approach has been adopted to evaluate possibility of pollution due to mine seepage and leachate migration on groundwater regime. The approach involves geophysical, hydrogeological, hydro-chemical and aquifer modeling studies. The investigation has the significance as many habitats surround the mining area facing groundwater problems.     

Assessing and managing the health risk due to ingestion of inorganic arsenic from fish and shellfish farmed in blackfoot disease areas for general Taiwanese

This paper assesses health risks due to the ingestion of inorganic arsenic from fish and shellfish farmed in blackfoot disease areas by general public in Taiwan. The provisional tolerable weekly intake of arsenic set by FAO/WHO and the target cancer risk assessment model proposed by USEPA were integrated to evaluate the acceptable consumption rate. Five aquacultural species, tilapia (Oreochromis mossambicus), milkfish (Chanos chanos), mullet (Mugil cephalus), clam (Meretrix lusoria) and oyster (Crassostrea gigas) were included. Monte Carlo analysis was used to propagate the parameter uncertainty and to probabilistically assess the health risk associated with the daily intake of inorganic As from farmed fish and shellfish. The integrated risk-based analysis indicates that the associated 50th and 95th percentile health risk are 2.06×10(-5) and 8.77×10(-5), respectively. Moreover, the acceptable intakes of inorganic As are defined and illustrated by a two dimensional graphical model. According to the relationship between C(inorg) and IR(f) derived from this study, two risk-based curves are constructed. An acceptable risk zone is determined (risk ranging from 1×10(-5) to 6.07×10(-5)) which is recommended for acceptable consumption rates of fish and shellfish. To manage the health risk due to the ingestion of inorganic As from fish and shellfish in BFD areas, a risk-based management scheme is derived which provide a convenient way for general public to self-determine the acceptable seafood consumption rate.     

Natural attenuation processes for remediation of arsenic contaminated soils and groundwater

Arsenic (As) contamination presents a hazard in many countries. Natural attenuation (NA) of As-contaminated soils and groundwater may be a cost-effective in situ remedial option. It relies on the site intrinsic assimilative capacity and allows in-place cleanup. Sorption to solid phases is the principal mechanism immobilizing As in soils and removing it from groundwater. Hydroxides of iron, aluminum and manganese, clay and sulfide minerals, and natural organic matter are commonly associated with soils and aquifer sediments, and have been shown to be significant As adsorbents. The extent of sorption is influenced by As speciation and the site geochemical conditions such as pH, redox potential, and the co-occurring ions. Microbial activity may catalyze the transformation of As species, or mediate redox reactions thus influencing As mobility. Plants that are capable of hyperaccumulating As may translocate As from contaminated soils and groundwater to their tissues, providing the basis for phytoremediation. However, NA is subject to hydrological changes and may take substantial periods of time, thus requiring long-term monitoring. The current understanding of As NA processes remains limited. Sufficient site characterization is critical to the success of NA. Further research is required to develop conceptual and mathematical models to predict the fate and transport of As and to evaluate the site NA capacity. Engineering enhanced NA using environmentally benign products may be an effective alternative.     

Assessing the characteristics of groundwater quality of arsenic contaminated aquifers in the blackfoot disease endemic area

Redox couples approach and multivariate statistical techniques, including factor analysis, cluster analysis and discriminant analysis, were applied to evaluate and to interpret the complex groundwater quality in the blackfoot disease endemic area, Taiwan. Most groundwater samples were characterized as Na-Ca-HCO(3) with HCO(3)(-) as the dominant anion. Total arsenic (As) concentration, predominantly as As(3+), ranged from <1.0 to 562.7 μg/L. The patterns of measured reducing potential were consistent with those values calculated from As couple, revealing the in situ environment enhanced the accumulation of As concentration in the groundwater. Factor analysis proposed a four-factor model, comprising salination, reductive dissolution of Fe/Mn oxyhydroxides, As reduction and chemical potential factor, and explained 89.94% of total variance in groundwater. Furthermore, two factors, reductive dissolution of Fe/Mn oxyhydroxides and As reduction, suggested that the decoupled reductive processes accounted for high As concentration in this area. Cluster analysis was adopted to spatially categorize the sampled wells into three main clusters and characterized by the factor scores of the four-factor model. Two-parameter (pH and Eh) model derived from discriminant analysis can be used for preliminary assessment to determine whether the As concentration exceeds 10 μg/L with simple field measurements in this area.     

Treatment of nondetects in multivariate analysis of groundwater geochemistry data

Principal components analysis (PCA) is used to evaluate similarities in the trace element chemistry of groundwaters. Many of the trace elements, however, occur at concentrations below the detection limits (DL), which presents problems for statistical analyses. Since the optimal methods for dealing with the ‘

In this study, a new approach was developed to determine the best substitution methods when dealing with the ‘DL’ values for a given data set. Monte Carlo simulation experiments, using a mixture multivariate model, were performed to test the effects of substitution of the ‘

When ‘相似文献   

Hydrogeochemistry and arsenic contamination of groundwater in the Ganges Delta Plain, Bangladesh

Geochemical composition and the level of Arsenic (As) contamination of groundwater in the Ganges Delta Plain, southwestern Bangladesh were elucidated. Hydrogeochemical data of tube well samples suggested that the groundwater is mostly Ca-Mg-HCO(3) type with bicarbonate (HCO(3)(-)) as the dominant anion, though other type waters are also observed. In contrast, the elevated EC, Cl(-) and high content of Na(+) relative to Ca(2+), Mg(2+) and K(+) in six groundwater samples suggest their saline origin. Low concentrations of NO(3)(-) and SO(4)(2-), and high concentrations of dissolved organic carbon (DOC), HCO(3)(-) and PO(4)(3-) indicate the reducing conditions of subsurface aquifer where sediments are deposited with abundant organic matter. The total As concentration in the analyzed samples is very high (0.0431-1.352 mg/L) along with high Fe (2.791-17.058 mg/L) and relatively low Mn (0.134-1.972 mg/L) at different depths. Distinct relationship of As with Fe and Mn, and strong correlation with DOC suggests that the biodegradation of organic matter and reductive dissolution of Fe-oxyhydroxide is considered to be the dominant processes to release As in aquifers. Moreover, negative correlation between As and SO(4)(2-) demonstrates the As may not be directly mobilized from sulfide minerals like arsenopyrite.     

不同还原剂对测定食品中砷影响的探讨

本文采用原子荧光光谱法,研究经不同还原剂处理过的食品中的砷。结果:半胱氨酸-硫脲-碘化钾混合还原剂对砷的还原效果比单一的还原剂效果好;硫酸浓度在0.6%~1.6%范围内,酸度对检测结果影响可以忽略。     

原子荧光法烟叶土壤砷的测定

本文应用原子荧光法测定了福建省不同地区烟叶土壤中的砷,对仪器条件和试剂使用进行研究,得到检出限为0.079μg/L,相对标准偏差1.45%,加标回收率为92%-105%,结果表明该法操作简便,准确度高,精密度好。     

Effects of adsorbent dose, its particle size and initial arsenic concentration on the removal of arsenic, iron and manganese from simulated ground water by Fe3+ impregnated activated carbon

This paper presents the observations of the study on arsenic removal from a contaminated ground water (simulated) by adsorption onto Fe³⁺ impregnated granular activated carbon (GAC-Fe). Fe²⁺, Fe³⁺ and Mn²⁺ have also been considered along with arsenic species in the water sample. Similar study has also been done with untreated granular activated carbon (GAC) for comparison. The effects of adsorbent dose, particle size of adsorbent and initial arsenic concentration on the removal of As(T), As(III), As(V), Fe²⁺, Fe³⁺ and Mn²⁺ have been discussed. Under the experimental conditions, the optimum adsorbent doses for GAC-Fe and GAC have been found to be 8 g/l and 24 g/l, respectively with an agitation time of 15 h. Particle size of the adsorbents (both GAC and GAC-Fe) has shown negligible effect on the removal of arsenic and Fe species. However, for Mn removal the effect of adsorbent particle size is comparatively more. Percentage removal of As(T), As(V) and As(III) increase with the decrease in initial arsenic concentration (As₀). However, the increase in percentage removal of all the arsenic species with decrease in As₀ are less for higher value of As₀ (3000–500 ppb) than those of the lower value of As₀ (500–10 ppb). The % removal of As(T), As(III), As(V), Fe, and Mn were 95%, 92.4%, 97.6%, 99% and 41.2%, respectively when 8 g/l GAC-Fe was used at the As₀ value of 200 ppb. However, for GAC these values were 55.5%, 44%, 71%, 98% and 97%. The pH and temperature of the study were 7 ± 0.1 and 30 ± 1 °C, respectively.     

Application of surfactant enhanced permanganate oxidation and bidegradation of trichloroethylene in groundwater

The industrial solvent trichloroethylene (TCE) is among the most ubiquitous chlorinated solvents found in groundwater contamination. The main objectives of this study were to evaluate the feasibility of using non-ionic surfactant Simple Green™ (SG) to enhance the oxidative dechlorination of TCE by potassium permanganate (KMnO₄) employing a continuous stir batch reactor system (CSBR) and column experiments. The effect of using surfactant SG to enhance the biodegradation of TCE via aerobic cometabolism was also examined. Results from CSBR experiments revealed that combination of KMnO₄ with surfactant SG significantly enhanced contaminant removal, particularly when the surfactant SG concentrated at its CMC. TCE degradation rates ranged from 74.1% to 85.7% without addition of surfactant SG while TCE degradation rates increased to ranging from 83.8% to 96.3% with presence of 0.1 wt% SG. Furthermore, results from column experiments showed that TCE was degraded from 38.1 μM to 6.2 μM in equivalent to 83.7% of TCE oxidation during first 560 min reaction. This study has also demonstrated that the addition of surfactant SG is a feasible method to enhance bioremediation efficiency for TCE contaminated groundwater. The complete TCE degradation was detected after 75 days of incubation with both 0.01 and 0.1 wt% of surfactant SG addition. Results revealed that surfactant enhanced chemical oxidation and bioremediation technology is one of feasible approaches to clean up TCE contaminated groundwater.     

Effect mechanism of arsenic on the growth of ultrafine tungsten carbide powder

Arsenic element refines W powders significantly during the hydrogen reduction process of tungsten oxide in our previous studies. In this paper, the nanocrystalline WC-As composite powders were prepared by carbonization of nano W-As composite powders and the effects of arsenic on the growth of WC powder were discussed in detail. The prepared samples were characterized by X-ray diffraction, differential scanning calorimetric analysis, scanning electron microscope, transmission electron microscope, X-ray photoelectron spectroscopy and Inductively Coupled Plasma. The results showed that arsenic appropriately raised the initial temperature of carbonization, significantly accelerated carbonization reaction process and shorten the reaction time. Moreover, WC-As composite powders merged and grew up directly without particle expansion and cracking. And the nano WAs₂ particles attached to WC grain boundaries and hindered the growth of WC grain through grain boundary migration. The above two effects resulted in the WC-As composite powders prepared at 1300?°C for 2?h with the average size of about 121?nm in diameter.     

Kinetics of laser-induced photodarkening in arsenic based chalcogenide glasses

Photoinduced changes in the optical properties of chalcogenide glass thin films have been studied extensively but usually only permanent changes were recorded through measurements before and after exposure to pump light. To understand the progression of such effects, in this paper we report in situ measurement of transient changes in the optical transmission of amorphous As₂Se₃, As₅Se₅ and As₄Se₃ thin films during their exposure to a He-Ne laser which has photon energy close to the bandgap of the studied compositions. Mathematical expressions are established, which describe accurately both the light intensity and time dependences of photodarkening. The structural origin of the observed changes is discussed briefly.     

Determination of groundwater flownets, fluxes, velocities, and travel times using the complex variable boundary element method

The complex variable boundary element method, CVBEM, employs the Cauchy integral with any complex variable (e.g., complex potential, complex flux, or complex velocity) to solve boundary value problems. The CVBEM formulation is consistent with the primal and dual solutions of the boundary integral equation, as well as the analytic element method. The resulting problem is overdetermined because two boundary conditions can be specified at each node. Ordinary least squares provides a unique solution that minimizes boundary specification errors. Flownets are obtained by noting that the position of fluid–stream potential intersections can be found by exchanging potential and position in the Cauchy integral, which enhances the determination of travel times along streamlines. Three regional groundwater flow problems are used to illustrate the CVBEM approach, the original problem as defined by Tóth, plus two related problems as described by Domenico and Paliauskas, and by Nawalany.     

Effect of contact order on the adsorption of inorganic arsenic species onto hematite in the presence of humic acid

The speciation of aqueous and adsorbed As forms of arsenic (As) is a major environmental concern in the presence of humic acid (HA). The speciation during As adsorption process by the effect of contact order were evaluated in various equilibrated ternary systems consisting of As, HA and hematite. One ternary system was composed of the preequilibrated As(III)- or As(V)-HA complex, with the subsequent addition of hematite ((As-HA)-hematite system), and the other consisted of the preequilibrated HA-hematite, with the addition of As(III) or As(V) (As-(HA-hematite) system). The presence of HA led to a decrease in the As adsorption, opposite to cationic adsorption. The order of the amounts of As adsorption were found to follow as: As(V)-hematite>hematite-(As(V)-HA)>As(V)-(HA-hematite)>As(III)-hematite>hematite-(As(III)-HA)>As(III)-(HA-hematite). Free As(V) and As-HA complex were preferentially adsorbed onto the hematite surface. The immobilization of As can come from adsorbed HA on mineral surfaces, and formation of As-HA complex, following their slow kinetics.     

地下水中Fe的ICP-MS检测和修正方法

提出了使用电感耦合等离子体质谱法检测地下水中Fe的过程中,标准系列溶液与样品溶液由于基体不同,随雾化气流量变化时所受到的影响程度不一致,对样品中Fe的分析结果的准确性和可靠性产生不利影响。同时提出在线内标溶液含有一定浓度的Fe,并把相应的检测值带入分析结果,对低含量样品中Fe的分析结果的准确性和可靠性产生不利影响。通过实验研究,说明了使用监控样技术对这两个问题进行修正能够获得良好效果,并且相应说明了监控样的制备方法、保存条件和使用期限及对在线内标溶液的处理方法。在这个基础上,建立了新的电感耦合等离子体质谱法检测地下水中Fe的方法,重新确定了方法参数。方法的检出限(DL)达到18.9ng/mL。方法精密度(RSD)为6.11%～8.56%(n=12)。加标回收率为97.55%。     

Studies on the removal of arsenic (III) from water by a novel hybrid material

The present work provides a method for removal of the arsenic (III) from water. An ion-exchanger hybrid material zirconium (IV) oxide-ethanolamine (ZrO-EA) is synthesized and characterized which is subsequently used for the removal of selective arsenic (III) from water containing 10,50,100 mg/L of arsenic (III) solution. The probable practical application for arsenic removal from water by this material has also been studied. The various parameters affecting the removal process like initial concentration of As (III), adsorbent dose, contact time, temperature, ionic strength, and pH are investigated. From the data of results, it is indicated that, the adsorbent dose of 0.7 mg/L, contact time 50 min after which the adsorption process comes to equilibrium, temperature (25 ± 2), solution pH (5-7), which are the optimum conditions for adsorption. The typical adsorption isotherms are calculated to know the suitability of the process. The column studies showed 98% recovery of arsenic from water especially at low concentration of arsenic in water samples.     

Electrokinetic remediation of wood preservative contaminated soil containing copper, chromium, and arsenic

As a result of wood treatment, and the recent banning of the copper, chromium, and arsenic (CCA) treated wood for residential use many CCA treatment facilities have been abandoned or being closed. Soil contamination resulting from CCA is common at these sites. In this study, the feasibility of electrokinetic technique to remove CCA from contaminated soil was investigated. To better understand the ionic mobility within the soil and to detect the generation and advancement of acid front, sampling ports were provided along the longitudinal axis of a test cell. To determine the effect of varying current, three tests were performed at different current densities of 5.9, 2.9, and 1.5mA/cm(2) for a period of 15 days. The initial concentrations of copper, chromium, and arsenic in the soil were 4800, 3100, and 5200mg/kg, respectively. Dilute nitric acid was used as an amendment to neutralize the hydroxyl ions produced at the cathode. Experiments resulted in removal efficiencies as high as 65% for copper, 72% for chromium, and 77% for arsenic. The results also indicated that the advancement of acid front favored desorption of metals from the soil and the metals were mobilized either as free cations or metal complexes. Chromium that was in its +6 valence state was transported as anion prior to its reduction. However, once the chromium was reduced to chromium(III) its transport direction reversed with transport being favored towards the cathode.     

Perspectives of low cost arsenic remediation of drinking water in Pakistan and other countries

Arsenic concentrations above acceptable standards for drinking water have been detected in many countries and this should therefore is a global issue. The presence of arsenic in subsurface aquifers and drinking water systems is a potentially serious human health hazard. The current population growth in Pakistan and other developing countries will have direct bearing on the water sector for meeting the domestic, industrial and agricultural needs. Pakistan is about to exhaust its available water resources and is on the verge of becoming a water deficit country. Water pollution is a serious menace in Pakistan, as almost 70% of its surface waters as well as its groundwater reserves have contaminated by biological, organic and inorganic pollutants. In some areas of Pakistan, a number of shallow aquifers and tube wells are contaminated with arsenic at levels which are above the recommended USEPA arsenic level of 10 ppb (10 μg L⁻¹). Adverse health effects including human mortality from drinking water are well documented and can be attributed to arsenic contamination. The present paper reviews appropriate and low cost methods for the elimination of arsenic from drinking waters. It is recommended that a combination of low cost chemical treatment like ion exchange, filtration and adsorption along with bioremediation may be useful option for arsenic removal from drinking water.     

微波消解-氢化物发生原子荧光光谱法同时测定蔬菜中汞、砷

本文建立了一种梯度升压微波消解样品,氢化物发生双道原子荧光光谱法同时测定蔬菜样品中汞、砷的方法。在优化实验条件下,蔬菜样品中Hg、As回收率分别为98.9%-109.3%和91.1%-96.1%;检出限分别为0.0094μg/L、0.0331μg/L。并对其相讨标准偏差(RSD)、精密度和准确度进行了评估,结果表明该方法用于蔬菜中Hg、As的同时测定是可行的。