缺氧沉积物中重金属形态连续萃取方法的稳定性研究

考察了海水养殖区域缺氧沉积物中重金属形态连续萃取法萃取过程中溶液pH值、温度变化和胶体形成对形态分离结果的影响。结果表明,连续萃取法Step1萃取酸溶态时,萃取液pH值的轻微升高使Pb和Zn的萃取结果明显降低;Step2萃取还原态时,萃取液pH值明显升高对重金属的萃取结果影响很小;Step3萃取有机质结合态时,萃取液pH值的降低对重金属萃取结果影响较小(除Pb外)。由于连续萃取法中各步萃取反应的热力学过程不同,Step1和Step2萃取后溶液温度轻微升高而在Step3中溶液温度稍微降低,溶液温度变化(<2.5℃)对重金属形态的影响很小。在Step1、Step2和Step4萃取过程中胶体的形成和存在,对萃取液Cd、Zn和Cu有明显的吸附影响;而在Step3萃取中萃取剂的分散作用有效控制了溶液中胶体的形成。因此采用连续萃取方法评价沉积物中的重金属形态时,控制萃取液pH值和胶体形成有利于提高萃取结果的稳定性和准确性。     

Simultaneous Removal of Heavy Metals (Cu,Cd, Cr,Ni, Zn and Pb) from Aqueous Solutions Using Thermally Treated Romanian Zeolitic Volcanic Tuff

Increased concentrations of heavy metals in the environment are of public health concern, their removal from waters receiving considerable interest. The aim of this paper was to study the simultaneous adsorption of heavy metals (Cu, Cd, Cr, Ni, Zn and Pb) from aqueous solutions using the zeolitic volcanic tuffs as adsorbents. The effect of thermal treatment temperature, particle size and initial metal concentrations on the metal ions sorption was investigated. The selectivity of used zeolite for the adsorption of studied heavy metals followed the order: Pb > Cr > Cu > Zn > Cd > Ni. The removal efficiency of the heavy metals was strongly influenced by the particle sizes, the samples with smaller particle size (0–0.05 mm) being more efficient in heavy metals removal than those with larger particle size (1–3 mm). Generally, no relevant changes were observed in heavy metals removal efficiency for the treatment temperatures of 200 °C and 350 °C. Moreover, at a higher temperature (550 °C), a decrease in the removal efficiencies was observed. The Cd, Zn, Cu, Cr, Zn and Ni sorption was best described by Langmuir model according to the high values of correlation coefficient. The pseudo-first-order kinetic model presented the best correlation of the experimental data.     

Use of the diffusive gradients in thin films technique (DGT) with various diffusive gels for characterization of sewage sludge-contaminated soils

The diffusive gradients in thin film technique (DGT) was used for characterization of South Moravian arable soils (sampling sites Zlín, Tuřany, and Chrlice) amended by sewage sludge in the 1980s. Two types of polyacrylamide diffusive gel with different pore size (APA gels—cross-linked with agarose and RG gels—cross-linked with bis-acrylamide) were employed. The (bio)available parts of Cd, Cu, and Ni and the proportions of inorganically and organically complexed species of these metals were assessed. The degree of metal resupply from the soil solid phase to the soil solution was also determined. Metal concentrations obtained by the DGT technique were lower by almost 4 to 5 orders of magnitude in comparison with those obtained by extraction with aqua regia. DGT concentrations of metals were also lower by approximately 1 to 2 orders of magnitude in comparison with those obtained by extraction with sodium nitrate (commonly used for assessment of the (bio)available part of metals). Results obtained by DGT measurement were expected to be closer to the actual content of available metal species than results obtained by extraction with sodium nitrate. Using RG gels together with APA gels provided resolution of inorganically and organically complexed metal species and their proportional representation. Inorganic metal species (particles smaller than 1 nm) formed a predominant part of assessed metal content in all studied soil samples and horizons. However, there was the exception of the cadmium content in the middle profile of Chrlice sandy soil sample. Ratio R values indicated that resupply of Cd, Cu, and Ni from the solid phase to the soil solution varied for individual soil samples and individual depth profiles. Mobile and labile species of Cd, Cu, and Ni were much more closely related to upper rather than deeper horizons. This observation correlates very well with the mechanical treatment and amendment of the studied soils.     

Heavy Metals in Acrylic Color Paints Intended for the School Children Use: A Potential Threat to the Children of Early Age

Heavy metals are the harmful elements, regarded as carcinogens. Nevertheless, owing to their physical and chemical properties, they are still used in the production of several commercial products. Utilization of such products increases the chance for the exposure of heavy metals, some of them are categorized as probable human carcinogens (Group 1) by the International Agency for Research on Cancer. Exposure of heavy metals to school children at early age can result severe life time health issues and high chance of emerging cancer. Thus, we have performed study relating to the presence of heavy metals in acrylic color paints commonly used by the school children. Acrylic paints of different colors were assayed for seven potential heavy metals manganese (Mn), cobalt (Co), nickel (Ni), zinc (Zn), arsenic (As), cadmium (Cd) and lead (Pb) using microwave digestion and iCAPQ inductively coupled plasma mass spectrometry (ICP-MS) system. The optimized method including paints digestion reagents nitric acid (HNO₃, 65%, 5 mL) and hydrofluoric acid (HF, 40%, 2 mL) have offered excellent method performance with recovery values ranged between 99.33% and 105.67%. The elements were identified in all of the analyzed samples with concentrations ranged from 0.05 to 372.59 µg/g. Cd constitutes the lower percentage (0.05%), whereas Zn constitutes high ratio contribution which was tremendously high (68.33%). Besides, the paints contamination was also color specific, with considerably total heavy metal concentrations found in brunt umber (526.57 µg/g) while scarlet color (12.62 µg/g) contained lower amounts. The outcomes of our investigation highlight the necessity for guidelines addressing the heavy metals in acrylic color paints intended for the school children usage.     

Utilization of optimized BCR three-step sequential and dilute HCl single extraction procedures for soil-plant metal transfer predictions in contaminated lands

The prediction of soil metal phytoavailability using the chemical extractions is a conventional approach routinely used in soil testing. The adequacy of such soil tests for this purpose is commonly assessed through a comparison of extraction results with metal contents in relevant plants. In this work, the fractions of selected risk metals (Al, As, Cd, Cu, Fe, Mn, Ni, Pb, Zn) that can be taken up by various plants were obtained by optimized BCR (Community Bureau of Reference) three-step sequential extraction procedure (SEP) and by single 0.5 mol L(-1) HCl extraction. These procedures were validated using five soil and sediment reference materials (SRM 2710, SRM 2711, CRM 483, CRM 701, SRM RTH 912) and applied to significantly different acidified soils for the fractionation of studied metals. The new indicative values of Al, Cd, Cu, Fe, Mn, P, Pb and Zn fractional concentrations for these reference materials were obtained by the dilute HCl single extraction. The influence of various soil genesis, content of essential elements (Ca, Mg, K, P) and different anthropogenic sources of acidification on extraction yields of individual risk metal fractions was investigated. The concentrations of studied elements were determined by atomic spectrometry methods (flame, graphite furnace and hydride generation atomic absorption spectrometry and inductively coupled plasma optical emission spectrometry). It can be concluded that the data of extraction yields from first BCR SEP acid extractable step and soil-plant transfer coefficients can be applied to the prediction of qualitative mobility of selected risk metals in different soil systems.     

Determination of Cadmium,Copper, Lead,and Zinc in Pilchard Sardines from the Bay of Boumerdés by Atomic Absorption Spectrometry

Fish are an important human food with increasing consumption in recent decades. Diet is the main route of exposure to heavy metals for human health. For this reason, many studies have been performed on the pollution by heavy metals in different species of fish. Our main objective was to evaluate the pollution by trace metals (Zn, Cu, Pb, and Cd) in sardine muscles collected from the bay of Boumerdés (Algeria). Flame atomic absorption spectroscopy (AAS) was used for the quantification of Cu and Zn. The quantification of Cd and Pb was achieved by graphite furnace (GF) AAS. The analysis revealed the presence of metal trace elements in the muscles of species at concentrations below the thresholds established by national and international regulations.     

Determination of cadmium and lead in mussels by electrothermal atomic absorption spectrometry using an ultrasound-assisted extraction method optimized by factorial design

A simple and rapid method is described for the quantitative extraction and determination of Cd and Pb in mussel tissue (Mytilus edulis). The method is based on the quantitative ultrasound-assisted extraction (i.e. sample mass at mg level) of the two metals using diluted nitric acid as extractant. The extraction procedure is carried out in autosampler cups of the graphite furnace (typically, less than 20 mg). A two-level full factorial design (2⁴) was applied to optimize the variables influencing the ultrasound extraction process. These variables were: extraction time, ultrasound amplitude, nitric acid concentration and particle size. Optimization results showed that acid concentration and particle size were the more significant variables. Determination of Cd and Pb in extracts obtained after ultrasound treatment was carried out by Electrothermal Atomic Absorption Spectrometry. The method was validated by statistically comparing the metal contents found with the certified ones corresponding to the BCR 278 mussel tissue. No significant differences were observed for P = 0.05. LODs for Cd and Pb in mussel tissue were 0.019 and 0.37 μg g^–1. RSDs values (corresponding to between-batch precision for n = 5) were 2.2 and 6.7% for Cd and Pb, respectively. The method was applied to measure the contents of Cd and Pb in mussels used as pollution bioindicators from the Galician coast (Ria de Vigo, Spain).     

Concentrations of108mAg,137Cs,and210Pb in oyster (Crassostrea gigas) on the Japanese coast in relation to the distribution and behavior of radionuclides in sea water

Concentrations of^108mAg,¹³⁷Cs, and²¹⁰Pb in oysters (Crassostrea gigas) were measured for about 10 years on the northeast coast of Japan. Silver-108m was detected in oyster samples collected from an open bay, and its concentrations decreased from the initial value of about 30 mBq/kg fresh in the early 1980s to the value of about 10 mBq/kg fresh in the early 1990s. This decrease could be mainly explained by effects of the ocean current in the early 1980s, and the coastal sea water thereafter, as well as by the advection and diffusion in the ocean. In the nearly-closed bays, concentrations of^108mAg and²¹⁰Pb in oysters were remarkably lower than in the open bays. It suggests that scavenging of silver and lead from the sea water effectively occurred in the nearly-closed bays. In contrast, concentrations of¹³⁷Cs in oysters were similar in the open bays and in the nearly-closed bays.     

Assessing spatial distribution,sources, and potential ecological risk of heavy metals in surface sediments of the Nansi Lake,Eastern China

The study is conducted to investigate the spatial distribution, sources and ecological risk of seven heavy metals in surface sediments of Nansi Lake, Eastern China. A total of 29 samples were collected in surface sediments of Nansi Lake, and were analyzed for three nutrients (TN, TOC and TP), two major metals (Al and Fe), as well as seven trace metals (As, Cd, Cr, Cu, Hg, Pb and Zn). The mean concentrations of As, Cd, Cr, Cu, Hg, Pb, Zn, Fe and Al were 14.41, 0.22, 71.10, 30.1, 0.048, 29.14, 90.2, 30,816 and 70,653 mg kg^?1, respectively, and the mean contents of these metals were higher than the background values with the exception of Cu and Fe. The spatial distribution indicated that the contents of all seven heavy metals were characterized by relatively higher contents in the upper lake than the lower lake. The hotspots with high values of As, Cd and Hg were associated with the river mouths, and the hotspots of Pb were mainly located around the dam in the central part, while no significant associations were displayed between spatial distribution of Cr, Cu, Zn and the river mouths. The mean enrichment factor (EF) values of As, Cd, Hg and Pb were 2.03, 2.93, 3.21 and 2.18, respectively, showing their moderate enrichment, while Cr, Cu and Zn with mean EF values of 1.19, 0.89 and 1.01 were deficiency to minimal enrichment. Multivariate and geostatistical analyses suggested that PC1 controlled by Cr, Cu and Zn was a lithogenic component, and come from parent rocks leaching. PC2 including Cd and partially Hg represented the factor from industrial wastewater discharge. PC3 showed elevated loadings of As and partially Cd, and could be attributed to the agricultural practices. While PC4 including Pb and partially Hg, was dominated by coal combustion. The results of potential ecological risk suggested that sediment environment of Nansi Lake suffered from high ecological risk.     

Evaluation of serum metal profile in relation to biri smoking using ICP-MS

The metals intake through tobacco smoking is associated with adverse effects for human health. The present study was aimed to understand the effects of biri smoking on smoker’s serum metal profile. Seven metals, cadmium (Cd), nickel (Ni), lead (Pb), chromium (Cr), copper (Cu), iron (Fe) and zinc (Zn), were analysed in serum samples of 20 biri smokers and 20 non-smokers from North India. The Cd, Ni, Pb, Cr and Cu concentrations were higher while Fe and Zn concentrations were lower in smokers compared to non-smokers. The Fe concentrations, the highest among all metals, seemed to be unassociated with the smoking activity. This study indicated that biri smoking is a contributor to the body burden of Cd, Ni, Cu and Cr in the smoker’s body. The Cd, Ni, Cu and Fe concentrations are non-significantly associated with the age of smokers at p < 0.01 significance level, whereas Pb and Cr concentrations increase and Zn concentrations decrease with the increase in the age of smokers. Serum metal concentrations in the smoker subjects of North India are higher compared to the results of other similar studies. This could be linked to the poor quality of tobacco used in biri. We recommend conducting more detailed and controlled studies in this regard as a smoker is also subjected to other sources of exposure to metals.     

Solid phase extraction and diffusive gradients in thin films techniques for determination of total and labile concentrations of Cd(II), Cu(II), Ni(II) and Pb(II) in Black Sea water

Total dissolved and labile concentrations of Cd(II), Cu(II), Ni(II) and Pb(II) were determined at six locations of the Bourgas Gulf of the Bulgarian Black Sea coast. Solid phase extraction procedure based on monodisperse, submicrometer silica spheres modified with 3-aminopropyltrimethoxysilane followed by the electrothermal atomic absorption spectrometry (ETAAS) was developed and applied to quantify the total dissolved metal concentrations in sea water. Quantitative sorption of Cd, Cu, Ni and Pb was achieved in the pH range 7.5–8, for 30?min, adsorbed elements were easily eluted with 2?mL 2?mol?L^?1 HNO₃. Since the optimal pH for quantitative sorption coincides with typical pH of Black Sea water (7.9–8.2), on-site pre-concentration of the analytes without any additional treatment was possible. Detection limits achieved for total dissolved metal quantification were: Cd 0.002?µg?L^?1, Cu 0.005?µg?L^?1, Ni 0.03?µg?L^?1, Pb 0.02?µg?L^?1 and relative standard deviations varied from 5–13% for all studied elements (for typical Cd, Cu, Ni and Pb concentrations in Black Sea water). Open pore diffusive gradients in thin films (DGT) technique was employed for in-situ sampling and pre-concentration of the sea water and in combination with ETAAS was used to determine the proportion of dynamic (mobile and kinetically labile) species of Cd(II), Cu(II), Ni(II) and Pb(II) in the sea water. Obtained results showed strong complexation for Cu and Pb with sea water dissolved organic matter. The ratios between DGT-labile and total dissolved concentrations found for Cu(II) and Pb(II) were in the range 0.2–0.4. For Cd and Ni, these ratios varied from 0.6 to 0.8, suggesting higher degree of free and kinetically labile species of these metals in sea water.     

Environmental Implications of Heavy Metals in Soil from Huainan,China

Soil metal contamination is of great concern due to these elements’ bioavailability, toxicity, and persistence. A total of forty soil samples were collected from mining, industrial, agricultural, and residential areas. Inductively coupled plasma–mass spectrometry (ICP–MS) was employed to determine the concentrations of the heavy metals (As, Cd, Cr, Cu, Pb, and Zn). Geoaccumulation indices and health risk assessment models were employed to evaluate the potential ecological and health implications. The concentrations of As, Cr, and Zn in the industrial zone were higher than the values from the other areas, whereas the concentrations of Cd, Cu, and Pb were highest in the residential area. The distribution of metals may be attributed to different anthropogenic sources. The soils in the industrial area were moderately contaminated by As. The noncarcinogenic risk due to metals was determined to be negligible in these areas, while a high carcinogenic risk was obtained in the industrial area. The priority controls should be As, Cd, and Cr in the industrial area. However, the ecological, environmental, and health implications in the mining and residential areas should also be monitored. This study provides a comprehensive investigation of soil metals in industrial, mining, residential, and agricultural areas in China that may be employed for future environmental management and regularization.     

Trace metal accumulation in tissues of sole (Solea senegalensis) and the relationships with the abiotic environment

The distribution patterns and the organ-specific accumulation trends of 10 trace metals (iron, manganese, zinc, copper, chromium, nickel, cobalt, lead, cadmium and silver) and 4 major elements (sodium, potassium, calcium and magnesium) in 10 different tissues (heart, muscle, kidney, stomach, intestine, liver, gill, gonads, white skin and dark skin) of a benthic fish species (Solea senegalensis) from a densely populated coastal area affected by anthropogenic activities, the Bay of Cadiz (SW Spain), have been investigated. High variability of metal concentrations among tissues were found for Ca, Fe, Zn, Cu, Pb and Ag. Factor analysis was applied to study this variability. Five principal components were found explaining the 92.95% of the total variance and similarities in behavioural patterns of bioaccumulation were described. They associated Mg, Cr, Ni and Mn to intestine and stomach tissues (PC1), Ag, Cu and Cd to liver (PC2), Zn, K and Co to gonads (PC3), Na, Fe and Pb to gill, heart and kidney tissues (PC4) and Ca, Pb and Mn to gill and dark skin (PC5). The metallic concentration in the sediment and water was also studied. The pollution in this area was found moderate with outstanding values of Zn, Cu and Pb (average values of 139, 50.4 and 75.6?mg?kg^?1, respectively) in sediment and dissolved Cu (average value of 2.5?µg?L^?1). Metal bioconcentration trends followed the order Zn?>?Cu?>?Cd?>?Pb for dissolved metals in seawater, Cu?>?Zn?>?Cd?>?Pb?≈?Mn?>?Fe?≈?Ni?≈?Co for metals associated to particulate matter and Zn?≈?Cu?>?Cd?>?Mn?>?Co?≈?Fe?>?Ni?≈?Pb?>?Cr for metals in the sediment. Higher values were found for copper in liver, zinc in gonads and lead in gill, showing the relationship between biotic and abiotic environment. In addition, Cd bioconcentration factors were found high in liver and gill showing the sensitivity of sole to this metal even at low concentrations.     

Determination of cadmium and lead in mussels by electrothermal atomic absorption spectrometry using an ultrasound-assisted extraction method optimized by factorial design

A simple and rapid method is described for the quantitative extraction and determination of Cd and Pb in mussel tissue (Mytilus edulis). The method is based on the quantitative ultrasound-assisted extraction (i.e. sample mass at mg level) of the two metals using diluted nitric acid as extractant. The extraction procedure is carried out in autosampler cups of the graphite furnace (typically, less than 20 mg). A two-level full factorial design (2⁴) was applied to optimize the variables influencing the ultrasound extraction process. These variables were: extraction time, ultrasound amplitude, nitric acid concentration and particle size. Optimization results showed that acid concentration and particle size were the more significant variables. Determination of Cd and Pb in extracts obtained after ultrasound treatment was carried out by Electrothermal Atomic Absorption Spectrometry. The method was validated by statistically comparing the metal contents found with the certified ones corresponding to the BCR 278 mussel tissue. No significant differences were observed for P = 0.05. LODs for Cd and Pb in mussel tissue were 0.019 and 0.37 μg g^–1. RSDs values (corresponding to between-batch precision for n = 5) were 2.2 and 6.7% for Cd and Pb, respectively. The method was applied to measure the contents of Cd and Pb in mussels used as pollution bioindicators from the Galician coast (Ria de Vigo, Spain). Received: 30 June 1998 / Revised: 17 September 1998 / Accepted: 22 September 1998     

Nafion‐Coated Bismuth Film Electrodes for the Determination of Trace Lead and Cadmium in Herbal Medicines by Anodic Stripping Voltammetry

A novel analytical procedure for the determination of Pb(II) and Cd(II) in herbal medicines by differential pulse anodic stripping voltammetry (DPASV) on Nafion‐coated bismuth film electrode (NCBFE) was proposed and experimentally validated. Various experimental parameters, which influenced the response of the NCBFE to these metals in real samples, were optimized. The results showed that there were well‐defined peaks of Pb and Cd in herb samples at deposition potential of ?1.2 V and deposition time of 300 s. The analytical performance of the NCBFE was evaluated in the presence of dissolved oxygen, with the determination limits of 0.35 µg·L^?1 for Pb and 0.72 µg·L^?1 for Cd and recoveries of 87.8% –105.4% for Pb and 89.5% –108.5% for Cd obtained from different samples. The Pb and Cd concentrations in the studied samples have been also determined by graphite furnace atomic absorption spectrometry (GFAAS), suggesting that there was a satisfactory agreement between the two techniques, with relative errors lower than 6.5% in all cases. The great advantages of the proposed method over the spectroscopic method were characterized by its simplicity, selectivity and short analysis time, simultaneous analysis of different metals and cost‐efficiency.     

Thermal decomposition of metal-doped carbons

The effects of different concentrations of metals (Ni, Cu, Cd, Zn) on the reactivity of carbon towards air were studied by means of TG and DTA. It was observed that these metals are capable of decreasing the ignition temperature and increasing the mass loss. Activation energies calculated by Horowitz's method revealed that these metals promote the combustion of active carbon.     

Electrochemical study of heavy metals and metallothionein in yeast Yarrowia lipolytica

The bioaccumulation of heavy metals (cadmium, nickel, cobalt and zinc) and the effect of these metals on the production of metallothionein and metallothionein-like proteins (MT) in Yarrowia lipolytica was studied by electrochemical methods. The concentrations of heavy metals were determined by differential pulse voltammetry (DPV). A combination of the constant current chronopotentiometric stripping analysis (CPSA) and adsorptive transfer stripping technique (AdTS) was used to determine the content of MT in cells. Both the bioaccumulation of heavy metals and the production of MT in different cell compartments of Y. lipolytica exposed to heavy metals were monitored. The LD(50) of each metal was determined from the number of viable cells in yeast cultures: LD(50)Cd (37.5 microM), LD(50)Ni (570 microM), LD(50)Co (700 microM), and LD(50)Zn (1800 microM). The highest concentrations of heavy metals were found in the cell wall and membrane debris while the lowest concentrations were detected in the cytoplasm. Cadmium and nickel showed the most significant effect on the production of MT. This study provides new insights into the ecophysiology of microorganisms and demonstrates the potential use of these electrochemical methods in biotechnology.     

Assessment of heavy metals emission from traffic on road surfaces

This study aims to analyse RDS heavy metal concentrations on road deposited sediment (RDS) using Riccarton Campus of Heriot-Watt University, Edinburgh, Scotland as a study site. RDS samples were collected at two transverse positions from different sites over a 4 month period in order to describe the influence of traffic on heavy metal emissions. The heavy metal concentrations of the RDS were determined by strong nitric acid digestion and atomic absorption spectrometry. The mean concentrations for Zn, Cu, Cd, Cr, Ni, Pb and Fe were found to be 213, 57, 1, 16, 15, 118, and 13497 mg kg-1 from samples near to the curb and 211, 79, 2, 15, 9, 35, and 14276 mg kg⁻¹ from samples 1 m from the curb respectively. Furthermore for both positions the highest concentrations for all metals were associated with the finer fraction (<63 μm) and stronger correlations between the metals were found further from the curb than near the curb, indicating that metals accumulating on the road surface further from the curb may likely be from the same source (traffic), while the sources of metals near the curb are more diverse.     

Assessment of trace metals contamination in estuarine sediments using a sequential extraction technique and principal component analysis

Fractionation of the metals Cd, Cr, Cu, Ni, Pb and Zn in sediments was performed for samples collected from eight locations in the Poxim river estuary of Sergipe State, northeast Brazil, using the 3-stage sequential extraction procedure proposed by the European Community Bureau of Reference (BCR). The extraction method was found to be satisfactory for analysis of certified reference material BCR-701, with recovery values ranging from 85% (Cu) to 117% (Cr). The detection limits obtained were 0.001 to 0.305 µg g^− 1. Zn exhibited greatest mobility and bioavailability, indicative of anthropogenic sources, while Cr was mainly found in the residual fraction and could be used as an indicator for the contribution from natural sources. Cd, Cu, Ni and Pb were associated with the oxidizable fraction, and Pb, Cr and Ni with the reducible fraction. Principal component analysis (PCA) clearly separated the metals into three groups: I (Zn); II (Pb); III (Cd, Cu, Cr and Ni). These groupings were mainly due to different distributions of the metals in the various fractions, in sediments from the different locations. Risk assessment code (RAC) analysis indicated that although the metals presented a moderate overall risk to the aquatic environment, nickel showed a low risk (RAC < 10%) at three sites, while zinc presented a high risk (RAC > 30%) at four other sites.     

Development of reference materials for the analysis of acid-extractable metals in sludge

The development of reference materials to verify the determination of metals in sludge is described. Effluents from domestic and industrial treatment facilities were dried, size-reduced and homogenized. Multiple aliquots of each material were analyzed in two different government laboratories to determine reference values for the acid-extractable concentrations of more than 15 metals. These acid-extractable concentrations are distinct from total metal values. Different sample preparation and instrumental methods, along with internal quality assurance protocols, were used to confirm the results. The data show good agreement for most metals in the domestic material. Reference values for the leachable concentrations of several toxic metals and major constituents will become part of the Certificate of Analysis for Standard Reference Material (SRM) 2781 issued by the National Institute of Standards and Technology (NIST). Data for the candidate industrial sludge reference material are also presented and discussed.