Use of pollution indices and ecological risk in the assessment of contamination from chemical elements in soils and sediments – Practical aspects

This paper presents a discussion involving practical aspects of applying contamination indices and ecological risk factors derived from chemical elements in the environmental assessment of soils and sediments. The single and integrated indices: Geoaccumulation index (I_geo), Enrichment factor (EF), Contamination factor (CF), Pollution Index (PI), Ecological risk factor (E_ir), Pollution Load Index (PLI), Degree of contamination (C_deg), Modified Contamination Factor (mC_deg), and potential ecological risk index (PERI) were discussed, and some applications were presented didactically. The analytical care needed to obtain reliable indices with the studied ecosystem is also evidenced. In addition, the advantages and limitations of the use of these indices are presented.     

57Fe Mössbauer spectroscopy of banded iron formations from eastern India

Samples of the mosses Hylocomium splendens and Pleurozium schreberi, collected in the summer of 1998, were used to study the atmospheric deposition of heavy metals and other toxic elements in the Chelyabinsk Region situated in the South Urals, one of the most heavily polluted industrial areas of the Russian Federation. Samples of natural soils were collected simultaneously with moss at the same 30 sites in order to investigate surface accumulation of heavy metals and to examine the correlation of elements in moss and soil samples in order to separate contributions from atmospheric deposition and from soil minerals. A total of 38 elements (Na, Mg, Al, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, As, Se, Rb, Sr, Zr, Mo, Sb, Cs, Ba, La, Ce, Nd, Sm, Eu, Gd, Tb, Dy, Yb, Hf, Ta, W, Au, Th, U) in soil and 33 elements Na, Mg, Al, Cl, K, Ca, Sc, V, Cr, Mn, Fe, Co, Ni, Zn, As, Se, Br, Rb, Ag, Sb, Cs, Ba, La, Ce, Sm, Tb, Yb, Hf, Ta, W, Au, Th, U) were determined by epithermal neutron activation analysis. The elements Cu, Cd and Pb (in moss samples only) were obtained by atomic absorption spectrometry. VARIMAX rotated principal component analysis was used to identify and characterize different pollution sources and to point out the most polluted areas.     

Microwave digestion-ICP-MS for elemental analysis in ambient airborne fine particulate matter: rare earth elements and validation using a filter borne fine particle certified reference material

NIST standard reference material SRM 2783 was employed to validate a high temperature, high pressure, two-stage microwave assisted acid digestion procedure using HNO₃, HF and H₃BO₃ developed for the analysis of trace elements (including rare earths) in atmospheric fine particulate matter (PM_2.5) prior to inductively coupled plasma mass spectrometry (ICP-MS). This method quantitatively solubilized Na, Mg, Al, K, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Rb, Sb, Cd, Cs, Ba, Pb, Th, U and several rare earth elements (REEs) (La, Ce, Pr, Nd, Gd, Dy, Er, Sm and Eu) from SRM 1648 and SRM 2783. A small amount of HF in the first stage was required to dissolve silicates necessitating the corresponding addition of H₃BO₃ in second stage to dissolve fluoride precipitates of Mg, La, Ce and Th. The optimized microwave dissolution—ICP-MS method detected Na, Mg, Al, K, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Rb, Sr, Cd, Mo, Sb, Cs, Ba, La, Ce, Pr, Nd, Sm, Gd, Pb, Th and U at trace to ultra-trace levels in ambient airborne fine particles from three sites in North Carolina. La to light lanthanide signature ratios suggested that soil and motor vehicles are the dominant REE sources in SRM 2783 and PM_2.5 samples collected during this study.     

应用地质累积指数评价南昌市城市污泥重金属污染

应用地质累积指数对南昌市城市污泥(包括污水处理厂污泥和纸厂废水处理污泥)的重金属污染进行了分析评价。结果表明,城市污泥重金属中Pb、Cr按地质累积指数分级均为0,属无污染;As地质累积指数为0～1之间,表现为无污染～中度污染;青山湖污水处理厂污泥主要的重金属污染元素为Cd、Hg、Cu、Zn,其平均的地质累积指数为2～4,表现为中度污染～强污染。     

Determination of phytoextraction potential of plant species for toxic elements in soils of abandoned sulphide-mining areas

This study has determined contamination levels in soils and plants from the São Domingos mining area, Portugal, by k ₀-INAA. Total concentrations of As, Sb, Cr, Hg, Cu, Zn and Fe in soils were very high, exceeding the maximum limits in Portuguese legislation. Concentrations of toxic elements like As, Sb and Zn were highest in roots of Erica andevalensis, Juncus acutus, Agrostis castellana and Nicotiana glauca. Additionally, As, Br, Cr, Fe, Sb and Zn in all organs of most plants were above toxicity levels. Those species that accumulated relatively high concentrations of toxic elements in roots (and tops) may be cultivated for phytostabilisation of similar areas.     

Influence of s-, p-, d- and f- block elements doping on the optical and thermal properties of potassium dihydrogen phosphate crystals

The effect of the s-, p-, d-, and f- block elements [Mg(II), Sb(III), Pd(II), and La(III)] doping on the optical and thermal properties of potassium dihydrogen phosphate (KDP) crystals has been described. Energy dispersive X-ray spectra reveal the incorporation of metal ion [Mg(II), Sb(III), Pd(II), and La(III)] into the crystalline matrix of KDP. UV–Visible study shows that the transparency is not affected much by doping, and the diffuse reflectance data were employed to estimate the band gap energy. The differential scanning calorimetry curves reveal the purity of the sample, and no decomposition is observed up to the melting point.     

Trace element levels of aerosols at an urban area of Korea by instrumental neutron activation analysis

Instrumental neutron activation analysis was used to measure the concentrations of about 27 elements associated with airborne PM 10 samples that were collected from a roadside sampling station at a moderately polluted urban area of Taejon city, Korea. The magnitude of their concentrations was clearly distinguished and spanned over four orders. If compared in terms of enrichment factors, it was found that certain elements (e.g., As, Br, Cl, Sb, Se, and Zn) are enriched in PM 10 samples of the study site. The factor analysis indicated three factors with statistical significance, which may exert dominant controls on regulating the metal concentration levels in the study area.     

The Influence of Non-Engineered Municipal Landfills on Groundwater Chemistry and Quality in Bloemfontein,South Africa

This study assessed the groundwater quality around two municipal solid waste landfill sites, in the city of Bloemfontein, Free State Province, South Africa. The two landfill sites are located in two contrasting geological terrains, with both lacking some basic facilities found in a well-designed landfill. A total of eight groundwater samples were collected from pollution monitoring boreholes near the two landfill sites, with five samples representing the northern landfill site and three samples representing the southern landfill site. The samples were collected in the autumn and winter seasons to assess any possible seasonal variations. They were analysed for physicochemical (pH, electrical conductivity (EC), total dissolve solids (TDS), chemical oxygen demand (COD) and total organic carbon (TOC)) and microbiological parameters (Escherichia coli, total coliform). The results of the analysis showed that the waters from both landfills were generally dominated by Ca, Mg, SO4, and HCO3 ions. Some of the major anions and cations in the water samples were above the South African National Standard (SANS241:2015) and World Health Organisation (WHO) permissible limits for drinking water. Majority of the boreholes had total dissolved solids and electrical conductivity values exceeding the SANS 241:2015 and WHO permissible limits. Piper trilinear plots for the two landfill sites showed that Ca(Mg)HCO3 water type predominates, but Ca(Mg)SO4 and Ca(Mg)Cl were also found. These water types were further confirmed with expanded Durov diagrams, indicating that that the boreholes represented a water type that is seldom found which is undergoing ion exchange, typical of sulphate contamination. From the SAR diagrams, boreholes in the northern landfill site had a high salinity hazard with only one borehole in the southern landfill site having a high salinity hazard. The geology was found to play a significant role in the distribution of contaminants into the groundwater systems in the study area. The study concluded that the northern landfill site had a poorer water quality in comparison to the southern landfill site based on the analysed physicochemical parameters. However, the southern landfill site showed significant microbial contamination, due to the elevated amount of E. coli and total coliform concentrations. The high permeability of the weathered dolerites in the northern landfill site might have enabled the percolation of contaminants into the groundwater resulting in the poorer water quality.     

Leaching of uranium,radium and thorium from vertisol soil by ground water

Shallow land burial is routinely used for the disposal of low-level radioactive waste. Natural processes causing leaching of radionuclides can lead to contamination of surrounding ground water and soil by the radionuclides. The comparative leachability of radionuclides U_(nat), ²²⁶Ra, ²²⁸Ra and Th_(nat) from the soil of a radioactive waste disposal site, by ground water was evaluated. The probability of leaching was obtained in the following order Ra (≈77%) > U (≈40%) > Th (≈20%). Observed ratios (OR) were calculated to correlate leachability of radionuclides to that of major cations Ca²⁺ and Mg²⁺. The leaching of the radionuclides was seen to be dependent on Ca²⁺ and SO₄²⁻ leached from the soil. This study provides sitespecific leachability of radionuclides, that can be used as indicator of the tendency for migration or retention in soil. It can play an important role during an unforeseen accident like breach of containment at the waste disposal site leading to contamination of soil and ground water and causing hazard to public via drinking water route.     

The role of different soil sample digestion methods on trace elements analysis: a comparison of ICP-MS and INAA measurement results

The measurement of trace-element concentration in soil, sediment and waste, is generally a combination of a digestion procedure for dissolution of elements and a subsequent measurement of the dissolved elements. “Partial” and “total” digestion methods can be used in environmental monitoring activities. To compare measurement results obtained by different methods, it is crucial to determine and to maintain control of the bias of the results obtained by these methods. In this paper, ICP-MS results obtained after matrix digestion with modified aqua regia (HCl+HNO₃+H₂O₂) method and two “total” digestion methods (microwave aqua regia+HF and HNO₃+HF) are compared with those obtained by instrumental neutron activation analysis, a non-destructive analytical method for the determination of the total mass concentrations of inorganic components in environmental matrices. The comparison was carried out on eight agricultural soil samples collected in one test area and measured by k₀-INAA and ICP-MS to determine As, Co, Cr, Sb and Zn mass concentration. The bias of results for As, Cd, Co, Cr, Cu, Ni, Pb, Sb and Zn of the three digestion methods were assessed using selected measurement standards. This paper highlights that the digestion procedure is an integral part of the measurement and can affect the measurement result in environmental analysis.     

Analysis of Tradescantia pallida plant exposed in different sites for biomonitoring purposes

Comparisons were made between the results obtained for elements accumulated by Tradescantia pallidaplant exposed in sites with different pollution levels: Cerqueira César and Congonhas districts, considered polluted areas of São Paulo city, and Caucaia do Alto county, considered a non polluted site. Statistical test applied to the results indicated that plant samples from polluted areas presented higher concentrations of Ba, Ce, Cr, Co, Fe, La, Sb and Sc than those found for ones from a non-polluted site. Discriminant analysis applied to the results obtained revealed three groups of results corresponding to sites with different levels of pollution.     

Comparative PGAA and NAA results of geological samples and standards

Concentrations of major and trace elements in volcanic rock and soil samples, including geological standard reference materials, were determined by neutron activation analysis (NAA) and prompt gamma activation analysis (PGAA), both using the k ₀-standardization method. The paper highlights the different experimental procedures, such as sample preparation, data collection and spectrum evaluation. In geological samples, PGAA gives precise results for major elements (Si, Ti, Al, Fe, Mn, Mg, Ca, Na, K and—as a unique method—for H), for some of the light trace elements as B and Cl, as well as for Sc, S, Cr, Co, Ni, Cd, Nd, Sm and Gd. NAA is sensitive for the rare earth elements, and for many major (Ti, Al, Fe, Mn, Mg, Ca, Na, K) and trace elements (e.g.: Sc, V, Cr, Co, Ni, Cu, Zn, As, Se, Rb, Sr, Zr, As, Sb, Ce, Ba, Hf, Ta, W). For most major elements the results obtained by the two methods show good agreement. The comparison of the results obtained for trace elements is not always possible, since PGAA is less sensitive and concentrations are often below its detection limits. Nevertheless, the complementarity of NAA and PGAA allows nearly panoramic analysis of geological materials.     

ICP-AES analysis of metal content in shell of mussel Mytilus galloprovincialis from Croatian coastal waters

Metal content in samples of shell of mussel Mytilus galoprovincialis was determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). The efficiency of conversion of crude samples into solution by acid digestion in an open plate and in a microwave oven was examined by use of certified reference material of marine sediment and laboratory made standards of calcite and aragonite. Influence of high Ca content matrix on emission intensities of Al, Ba, Cd, Cu, Fe, Mg, Mn, Na, Ni, Pb, Sr and Zn was observed as depression of emission signal for most of the measuring elements, ranging from 0.8% to 8%. Greater values were noted at Ba and Ni emission lines. Enhancement of signals was observed for Na and Mg lines. The determination of As, Sb, Se and Sn was performed by HG/ICP-AES. The greater abundance of Sn was found in samples collected near the Al-processing industry centre. No detectable concentrations of As, Sb, and Se were found in shell samples. Results of ICP-AES metal analysis showed that samples collected near harbours, city waste or sewage outlets, and chemical industry centres indicate the certain level of contamination. It is shown that shell analysis provides useful data in determination of marine environment status.     

Characterization of the aeolian aerosol from Cape Verde by k 0-INAA and PIXE

Due to its location on West Coast of Africa, Cape Verde is highly influenced by Sahara Desert dust events being an optimum place to observe and study the African aeolian aerosol. During 2011, particulate matter with an aerodynamic diameter lower than 10 μm (PM₁₀) was sampled in Santiago Island and its chemical composition was evaluated by k ₀-instrumental neutron activation analysis (k ₀-INAA) and particle induced X-ray emission (PIXE). This study showed the existence of a seasonal intrusion of dust from Africa (that occurred from October to March) characterized by significant increases of PM₁₀, mineral elements and anthropogenic particles concentrations. In 2011, the PM₁₀ health-based air quality guidelines defined by WHO, EU and USEPA were exceeded. Cape Verde PM₁₀ composition was characterized essentially by high concentrations of elements originating from the soil (Ca, Ce, Co, Fe, K, Mg, Mn, Rb, S, Sc, Si, Sm, and Ti) and sea (Br, Cl, and Na); and low concentrations of anthropogenic elements (As, Cr, Cu, Ni, Pb, Sb, V, and Zn). k ₀-INAA and PIXE were fundamental tools for the determination of airborne chemical elements in Cape Verde. Their multi-elemental capabilities in association with low detection limits made it possible to determine the majority of the element concentrations of environmental interest.     

Reference materials for large-scale metal deposition surveys

 In order to ensure quality assurance in large-scale environmental contamination studies involving many different analytical laboratories, the use of calibrated reference materials is essential. Prior to a survey of atmospheric metal deposition in 1995 comprising 20 countries and covering large parts of Europe, the lack of suitable reference materials of moss and organic-rich soil was apparent. In order to improve the quality of analytical data to be produced in this international survey, candidate analytical laboratories were invited to participate in an intercomparison exercise. Three moss and three soil humus reference samples specifically prepared for this purpose were distributed anonymously among the laboratories, which were asked to report data for ten priority elements (V, Cr, Fe, Ni, Cu, Zn, As, Cd, Hg, Pb) and as many additional elements as they determined normally. In this paper the analytical data from the intercomparison are evaluated, and recommended values for the ten priority elements and 17 additional elements (B, Na, Mg, Al, S, K, Ca, Mn, Co, Se, Rb, Sr, Sb, Cs, Ba, La, Th) in each of the six reference samples are established. These samples should be useful for similar future studies including areas where the contamination levels are very low. Received: 17 October 1996 Accepted: 2 January 1997     

Fractionation of Sb and As in soil and sludge samples using different continuous-flow extraction techniques

The fractionation of Sb and As in soil and sludge samples had been comparably studied using two continuous-flow systems: a microcolumn (MC) and a rotating coiled column (RCC). The leachants were applied in correspondence with a five-step sequential extraction scheme addressing water-soluble, non-specifically sorbed, specifically sorbed, and bound to amorphous and crystalline Fe/Al oxide fractions of Sb and As. Inductively coupled plasma atomic emission spectroscopy was applied to determine antimony, arsenic, and major elements in the effluent and in the residual fractions after their digestion. Resemblances and discrepancies of the two methods were evaluated by the fractionation of Sb and As in forest soil, river sludge, and dumped waste (soil) samples. For the forest soil sample, which is very poor in organic matter, RCC and MC extractions yielded similar quantitative values of As and Sb contents in individual leachable fractions. However, for the river sludge sample with a moderate concentration of C _org (3.3 %), the results obtained by both continuous-flow methods are in satisfactory agreement. RCC extraction enabled water-soluble and non-specifically sorbed As fractions to be recovered, whereas after MC leaching, these environmentally relevant forms of As were not detected. For the soil rich in organic matter (C _org = 11.5 %), the discrepancy between the data of RCC and MC fractionations is significant. RCC extraction provides about six times higher recoveries of As and Sb bound to amorphous Fe/Al oxides. More efficient leaching of As and Sb in RCC may be attributed to the migration of organic-rich particles with low density inside the column that might enhance the mixing of the solid and liquid phases.     

Superstructure of hollandite KxMg(8+x)/3Sb(16−x)/3O16 (x≈1.76)

Single crystals of K_xMg_(8+x)/3Sb_(16−x)/3O₁₆ (x≈1.76) with a hollandite superstructure were grown. Ordering schemes for guest ions (K) and the host structure were confirmed by the structure refinement using X-ray diffraction intensities. The space group is I4/m and cell parameters are a=10.3256(6), c=9.2526(17)Å with Z=3. Superlattice formation is primarily attributed to the Mg/Sb occupational modulation in the host structure. Mg/Sb ratios at two nonequivalent metal sites are 0.8977/0.1023 and 0.1612/0.8388. Two types of the cavity are seen in the tunnel, where parts of K ions deviate from the cavity center along the tunnel direction. Probability densities for K ions in the two cavities are different from each other, which seems to have arisen from the Mg/Sb modulation.     

Source apportionment of trace elements in the Eastern Mediterranean atmosphere

Concentrations of elements and ions, measured in aerosol samples collected during 1993 were investigated to identify sources and source composition of aerosols in the Eastern Mediterranean atmosphere. The factor analysis have shown that Eastern Mediterranean aerosol is a four-component system, including a crustal component, long-range transported pollution component, a marine component and a local pollution component. Main anthropogenic component, which reaches to the region by long-range transport accounts for 70%-90% of the concentrations of Zn, Se, NO_3-, nss-SO₄ ^2-, NH₄ ⁺ and smaller fractions of V, Sb, Cr and Mn concentrations. According to the quantitative analysis of local and Saharan dust components, the most promising marker elements to distinguish Saharan dust from local soil were found to be Cr, Nd, Mg and Cs as they have significantly different compositions in the local soil and Saharan dust.     

Sn/Sb atom ordering in the ternary stannide-antimonide TiSnSb

TiSnSb was prepared by reacting the elements Ti and Sb in an Sn flux at 500°C. Alternatively, TiSnSb can be synthesized from the elements in the stoichiometric 1:1:1 ratio at 850°C. According to our single crystal data, TiSnSb forms the Mg₂Cu type, orthorhombic space group Fddd, with a=5.4892(7), b=9.845(1), and c=19.151(3) Å (Z=16). As evident from both our structure refinements and our electronic structure calculations, the two crystallographically independent positions of the Mg atoms in the Mg₂Cu type are not statistically occupied by the Sn and Sb atoms in the TiSnSb structure. Structural and electronic similarities to and differences from TiSb₂ and NbSnSb (both CuAl₂ type) are discussed. Supporting the electronic structure calculations, physical property measurements revealed the metallic character of TiSnSb, with holes being the dominant charge carriers.     

Simultaneous determination of hydride forming (As, Bi, Ge, Sb, Se, Sn) and Hg and non-hydride forming (Ca, Fe, Mg, Mn, Zn) elements in sonicate slurries of analytical samples by microwave induced plasma optical emission spectrometry with dual-mode sample introduction system

A slurry sampling method for the simultaneous determination of hydride forming (As, Bi, Ge, Sb, Se, Sn) and Hg and non-hydride forming (Ca, Fe, Mg, Mn, Zn) elements, without total sample digestion has been developed using the commercial dual-mode sample introduction system (MSIS) coupled with microwave induced plasma optical emission spectrometry (MIP-OES) from biological and environmental reference materials and real samples. The main advantage of this system is its simultaneous determination of elements that form volatile vapor species and elements that do not, without any instrumental changes. Optimization of reaction, nebulization and instrumental conditions was performed to characterize the new system. Slurry concentration up to 4% m/v (particles < 100 μm) prepared in 10% HNO₃ containing 100 μL of decanol, by application of ultrasonic agitation, was used with calibration by the standard addition technique. An ultrasonic probe was used to homogenize the slurry in the quartz cup just before its introduction into the reaction/nebulization system; the multimode sample introduction system (MSIS) combines the benefits of nebulization and vapor generation in a single device. Detection limits (LOD, 3σ_blank, peak area) of 0.07, 0.29, 0.25, 0.10, 0.12, 0.14, 0.11, 0.28, 0.42, 0.02, 0.21 and 0.34 μg g^− 1 were obtained for As, Bi, Ge, Sb, Se, Sn, Hg, Ca, Fe, Mg, Mn and Zn, respectively. The relative standard deviations were ca. 10%, adequate for slurry analysis. To test the accuracy, six certified reference materials were analyzed with the analyte concentrations mostly in the μg g^− 1 level. Measured concentrations are in satisfactory agreement with certified values for the biological reference materials (LUTS-1, DOLT-2) and environmental reference materials (PACS-1, GWB 07302, NIST 2710, NBS 1633b), all adequate for slurry sampling. The method was successfully applied to the determination of the elements in real samples (coal fly ash, lake sediment, sewage). The method requires small amounts of reagents and reduces contamination and losses.