Mercury speciation in contaminated soils by thermal release analysis

Thermal release analysis of mercury species in contaminated soils was performed by temperature controlled continuous heating of the samples in a furnace coupled to an Atomic Absorption Spectrophotometer (AAS). It was shown that this method allows the identification of different redox states of Hg-species through their characteristic releasing temperature ranges. The method was applied to Hg-contaminated samples from an inactive chlor-alkali production plant in former East Germany (GER), and from a gold mining area in Poconé, Mato Grosso, Brazil (BRA), as well as synthetic soil samples obtained by spiking pre-heated soil matrices (GER and BRA) with the following mercury species: Hg⁰, Hg₂Cl₂, HgCl₂, HgO and HgS. The samples GER, in general, frequently showed the presence of Hg²⁺ probably bound to humic substances, in the case of samples with higher total carbon content. Only in highly contaminated samples (>3000 ppm of mercury) was Hg⁰ the predominant species. The samples BRA more frequently showed the presence of mercury species in the lower oxidation states, i.e. Hg¹⁺ in combination with Hg⁰. The method allows observing changes in Hg-speciation in the samples with time, mainly changes among the oxidation states Hg⁰, Hg¹⁺ and Hg²⁺. The treated GER matrix showed a stronger tendency to oxidise Hf-species than the BRA treated matrix, in which only added Hg⁰ is partially oxidised to Hg²⁺ and Hg¹⁺. In contrast, the BRA matrix showed a pronounced tendency to reduce spiked Hg²⁺ to Hg¹⁺. This may be the reason for the presence of Hg¹⁺ in the majority of original BRA samples. The method appears to be very useful to study speciation of mercury and its dynamics. It can be used as a tool for monitoring mercury oxidation states and/or reactions of mercury in soils.     

Enhancing the Reliability of Laboratory Phosphorus Filter Tests: Effect of Influent Properties and Interpretation of Effluent Parameters

The distribution of selected elements in individual fractions of organic matter from anthropogenically contaminated soils was investigated. The attention was paid especially at Hg. Furthermore, contents of S, Mg, Mn, Fe, Cu, Zn and Pb were also measured. The decomposition of organic matter to particular fractions was carried out by the resin DAX-8. Ten soil samples were collected, and the Advanced Mercury Analyzer (AMA-254) was used for the determination of the total Hg content. The two highest Hg values reached up to the concentration 10.5 mg kg^?1, and in the highest one, it was almost 29 mg kg^?1. In each extract, mercury was measured by inductively coupled plasma mass spectrometry (ICP-MS), for other elements, inductively coupled plasma optical emission spectrometry (ICP-OES) was applied. Results of the analysis show that the Hg content bound to the humic acids is inversely proportional to the content of Mg, Mn, Fe and Cu. However, this dependence was not confirmed by the samples with the mercury content above 10 mg kg^?1. In the case of fulvic acids, the relationship between Hg and S was observed and has again an inverse character.     

Measuring Soil and Tissue Potassium with a Portable Ion-Specific Electrode in Cotton

Most laboratories make potassium (K) fertilizer recommendations based on field research calibrated with soil K from atomic absorption spectroscopy, flame emission spectroscopy, or inductively coupled plasma mass spectrometry. Information is needed to interpret readings from K⁺ meters on cotton. The objective was to compare soil and cotton plant sap potassium content from a Laqua Twin? K⁺ meter to results from standard tests. Aluminum sulfate solution was used with the meter to extract K from 10 soil samples from the North America Proficiency Testing program. A linear relationship (R² = 0.86) was found between K measured with a K⁺ meter and K measured with 138 labs using ammonium acetate or Mehlich-3. Using a factor of 1.4754 to adjust readings, fertilizer recommendations with the K⁺ meter were similar to results from atomic absorption spectroscopy. A linear relationship was found between petiole K measured in the lab and petiole sap measured with the K⁺ meter.     

Determination and Speciation of Aluminum in Environmental Samples by Cation Exchange High-Performance Liquid Chromatography with High Resolution ICP-MS Detection

A cation-exchange high-performance liquid chromatography with high resolution inductively coupled plasma mass spectrometric detection (CE-HPLC/ICP-MS) was developed for the determination and the speciation of aluminum in environmental samples. Three types of aluminum species (AlL_x ^<+2, AlL_x ²⁺, Al³⁺) were separated from one another, and were determined with the present system. The comparison of the present system with an established CE-HPLC with fluorimetric detection using 5-sulfo-8-quinolinol (CE-HPLC/FL) was described. The present system showed better sensitivity for aluminum than CE-HPLC/FL. Moreover, the analytical results for soil extract and lake water samples obtained with both methods were in good agreement with each other.     

Evaluation of soil sulfate extractants and methods of analysis for plant available sulfur

Abstract

A steady decline in sulfur additions to Atlantic Canadian soils has prompted the need for an accurate method of determining their plant available sulfur status. Three soils were extracted with five soil extractants ‐ 0.01M Ca(H2PO₄)₂‐H₂O in 2M HOAc, 0.1M CaCl₂, Bray‐1 and de‐ionized water. The soil extracts were analyzed for sulfur or sulfate using inductively coupled argon plasma emission spectrometry (ICAP), AutoAnalyzer (AAN), anion exchange‐high performance liquid chromatography (HPLC‐CD) or atomic absorption spectroscopy (AAS). Results were compared with plant response of sulfur treatments to red clover, ryegrass, canola and wheat in a growth room. Instrument reproducibility and crop response indicated the ideal method of determining plant available soil sulfur was HPLC‐CD using the extractant Ca(H2PO₄)₂‐H₂O.     

Comparison of In Vitro PBET and Phosphoric Acid Extraction as an Approach to Estimate Selenite and Selenate Bioaccessibility from Soil

Several approaches have been used to estimate the bioaccessibility of trace metals from soils. Here, we applied phosphoric acid extraction and the in vitro test physiologically based extraction (PBET) to soils containing selenium (Se) and compared their performance in estimating the bioaccessibility of Se. For this purpose, we used two soil samples and two Certified Reference Material soil samples with a range of Se concentrations. The total Se contents were measured in the samples and in the extracts by hydride generation–atomic fluorescence spectroscopy. Moreover, we also measured selenite and selenate in the soil extracts (from phosphoric acid and from the PBET) using the coupled techniques liquid chromatography–UV photooxidation–atomic fluorescence spectroscopy and liquid chromatography–mass spectrometry with inductively coupled plasma. From the results obtained in the present study, the PBET showed that the selenium bioaccessible fraction was mainly attributed to the gastrointestinal step. When comparing the results from PBET with those of the phosphoric acid extraction, similar values of Se (IV) and Se (VI) were obtained for both extraction systems. An estimation of the bioaccessibility percentage of Se is also reported.     

Determination of total boron in soils by inductively coupled plasma atomic emission spectrometry using microwave‐assisted digestion

Abstract

A method is described in which total soil boron (B) was determined by inductively coupled plasma atomic emission spectrometry (ICP‐AES). The method is based on microwave‐assisted digestion of soil samples with nitric acid (HNO₃), hydrofluoric acid (HF) and hydrogen peroxide (H₂O₂). Excess HF was eliminated by adding silicon (IV) oxide (SiO₂). The B 208.959 nm line was chosen as the analytical line to avoid the spectral interferences of iron (Fe). A detection limit of 0.0045 mg L^‐1 was obtained with the selected analytical line under the optimized operating conditions. Four National Institute of Standards and Technology (NIST) standard reference materials (three soils and one river sediment) and four different type of practical soils were analyzed to test the reliability of the method. The total B concentration in selected samples ranged from 19 to 76 mg kg^‐1. The excellent recoveries of the spike (98.5–101%) indicate that the proposed procedure is effective and feasible for the determination of total B in soils.     

Rapid Determination of Mercury in Contaminated Soil and Plant Samples Using Portable Mercury Direct Analyzer without Sample Preparation, a Comparative Study

The objective of this study was to determine the efficiency of a portable total mercury analyzer (OhioLumex RA-915+) in comparison with traditional analytical methods, such as inductively coupled plasma atomic emission spectrometry and cold vapor atomic absorption. The quick mercury analytical procedure with the direct mercury analyzer without sample pretreatment (such as sample digestion) was optimized for a variety of environmental samples, including contaminated soil and plant samples. The efficiency was evaluated using practical parameters, such as time required for analysis, sample amount, mercury species, accuracy, and precision/reproducibility, as well as using statistical analysis. Our results demonstrate that these three instrumental methods yielded similar mercury concentration values and statistical data, while the mercury direct analyzer had the advantages of not requiring for sample digestion and only requiring a small quantity of samples for distribution of mercury in a single root, a single root hair, and sub-regions of a single leaf of plants. These factors are used to justify use of the portable direct mercury analyzer under field conditions and validation of the results.     

Underestimation of chromium and zirconium in soils by hydrofluoric acid digestion and inductively coupled plasma-mass spectrometry

The concentrations of chromium (Cr) and zirconium (Zr) in 503 soil samples collected from 78 site in Japan were determined by using two utterly different methods. The first was the relatively widely used inductively coupled plasma-mass spectrometry (ICP-MS) combined with digestion with hydrofluoric acid (HF) and perchloric acid (HClO₄). The second was a non-destructive polarizing energy dispersive X-ray fluorescence spectrometric method (EDXRF) using pressed powder pellets. The Cr concentrations obtained by EDXRF were higher than those obtained by ICP-MS in ~75% of the samples. The EDXRF/ICP-MS ratios ranged from 0.48 to 9.65, and the geometric mean was 1.23. A typical example having big a difference in Cr content between the two methods was found in seven samples taken from a podzolic soil developed on sand dunes in northern Hokkaido. This sampling site is around 20 km from the northern edge of a serpentinite area that extends from north to south, forming the backbone mountain range of Hokkaido. The Cr concentrations obtained by ICP-MS for the seven samples were 27.9–52.2 mg kg^?1, similar to the average for all the samples, whereas those obtained by EDXRF were 101–460 mg kg^?1, falling within the range between the third quartile and the maximum for all the samples. It would be difficult to predict these results from the analytical data of other elements because the samples were high in silica (SiO₂) and low in magnesia (MgO), and did not show any characteristics typical of soils derived from serpentinite. X-ray adsorption near-edge structure (XANES) showed that Zr occurred as zircon (ZrSiO₄) in soils. The differences between the two methods were greater for Zr than for Cr. Zirconium concentrations obtained by EDXRF were higher than those by ICP-MS for all samples except three. The difference between the two methods was more pronounced in soils derived from granite that is widespread in western Japan. The EDXRF/ICP-MS ratios for seven soil samples from different horizons at a single sampling site ranged from 4.82 to 6.94 and were generally higher at the A horizon (Apg and Ag) and decreased with depth. Our results indicate that there is a high possibility of underestimation of Cr and Zr contents in soils for a considerable number of samples if determined with ICP-MS, and it could also overlook some important chemical characteristics of soils.     

Red soils derived from limestone contain higher amounts of trace elements than those derived from various other parent materials

The concentrations of 48 trace elements (Li, Be, Sc, V, Cr, Co, Ni, Cu, Zn, Ga, As, Br, Rb, Sr, Y, Zr, Nb, Mo, Ag, In, Cd, Sn, Sb, I, Cs, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, Ta, W, Tl, Pb, Bi, Th and U) in 14 soils derived from limestone, sampled at three sites, are compared with the concentrations in 500 soil samples derived from a variety of other parent materials. The 500 samples were collected from 75 sites nationwide in order to include the wide range of common soil types in Japan. Most analytical results were obtained by inductively coupled plasma mass spectrometry (ICP-MS), but Cr, As, Br, Zr, Sn, and I concentrations were determined by energy dispersive X-ray fluorescence spectrometry (EDXRF), because the acid dissolution techniques employed in this study were found to be incapable of recovering these elements completely. In order to examine the reliability of analyses, the concentrations of many elements were also determined by EDXRF, inductively coupled plasma-atomic emission spectrometry (ICP-AES), and atomic absorption spectrometry (AAS). Box and whisker diagrams (Tukey plots), constructed using log-transformed values of each element, show clearly that geometric means of nearly all the trace elements in soils derived from limestone are higher than those in soils derived from other parent materials. The only exceptions are Sr, Ag and Eu, though statistical analysis (Student’s t-test) shows that the differences for these three elements were not significant at p < 0.05. Similarly, the observed differences of geometric means for Sc, Br and Ba between limestone soils and other types of soils were also not significant at p < 0.05. It can be concluded, therefore, that the concentrations of the above-mentioned 48 trace elements in soils derived from limestone are significantly higher than those in other types of soils, with the exception of Sc, Br, Sr, Ag, and Ba, though it was necessary to exclude 81 soil samples, developed on scoriaceous (basaltic) volcanic ash from Mt. Fuji, as an exceptional group for comparisons of V and Cu, as these soils contain higher levels of these two elements. The above results can be attributed to the gradual accumulation of trace elements in the limestone soils due to the intense weathering processes.     

Mercury speciation adsorption (MESA) method for combustion flue gas: Methodology,artifacts, intercomparison,and atmospheric implications

Chemical speciation of mercury (Hg) in a wide variety of combustion flue gas matrices has been determined using the mercury speciation adsorption (MESA) method. The MESA sampling system for gas phase Hg species employs a series of heated, solid phase adsorbent traps. Flue gas oxidized Hg species (Hg(II) and MMHg) are adsorbed by a potassium chloride (KCl) impregnated soda lime sorbent. Elemental Hg (Hg⁰) is collected by an iodated carbon sorbent after passing through the KCl/soda lime sorbent. Total Hg (Hg_t) is determined by summation of species. In the laboratory, cold vapor atomic fluorescence spectroscopy (CVAFS) is used for detection of Hg collected on the solid sorbents, after appropriate sample digestion and preparation. The MESA method has been evaluated for species stability, matrix effects, breakthrough, artifacts and precision. Based on eight duplicate samples a mean precision of 6.8% 11% and 4.5% (relative percent difference) has been calculated for Hg⁰, Hg(II) and Hgt respectively. Intercomparison of the MESA method with other methods shows very good agreement for Hgt. Mass balance calculations at 5 sites range from 75 to 140%, with a mean of 97±25%. Overall mean speciation results from 19 separate determinations suggest that Hg(II) has a 1 sigma range of 40 to 94% in coal combustion flue gas at, the inlet to pollution control devices.     

Determination of Mercury Content in a Shallow Firn Core from Greenland by Isotope Dilution Inductively Coupled Plasma Mass Spectrometry

The total mercury content was determined in 6 cm sections of a shallow 7 m firn core and in surrounding surface snow from Summit, Greenland (elevation: 3238 m, 72.58^°N, 38.53^°W) collected in May 2001 by isotope dilution cold-vapor inductively coupled plasma mass spectrometry (ID-CV-ICP-MS). The focus of this research was to evaluate the capability of the ID-CV-ICP-MS technique for measuring trace levels of Hg typical of polar snow and firn. Highly enriched ²⁰¹Hg isotopic spike is added to approximately 10 mL melted core and thoroughly mixed. The Hg²⁺ in the sample is reduced on line with tin(II) chloride (SnCl₂) and the elemental Hg (Hg^°) vapor pre-concentrated onto gold gauze using a commercial amalgam system. The Hg is then thermally desorbed and introduced into a quadrupole ICP-MS. The blank-corrected Hg concentrations determined for all samples ranged from 0.25 to 1.74 ng/L (ppt) (average 0.59 ± 0.28 ng/L (1σ)) and fall within the range of those previously determined by Boutron et al. [Geophys. Res. Lett. 25, 1998, 3315–3318] (≤ 0.05–2.0 ng/L) for the Summit site. The average blank value was 0.19 ± 0.045 ng/L (n = 6, 1σ) and the method detection limit was 0.14 ng/L. The Hg values specifically for the firn core range from 0.25 to 0.87 ng/L (average 0.51 ± 0.13 ng/L (1σ)) and show both values declining with time and larger variability in concentration in the top 1.8 m.     

A comparison between X‐ray fluorescence and dissolution methods employing lithium metaborate fusion for elemental analysis of soil clays

Abstract

A method employing fusion of soil clay samples with lithium metaborate (1:5 ratio) in a furnace at 1050°C for 1 hr. subsequent dissolution of the fused sample in 4% HNO₃. and elemental analysis for Si, Al, Fe, Ca, Mg, K, and Ti by atomic absorption spectrometry was compared with the X‐ray fluorescence (XRF) fused disc technique for analysis. Duplicated analyses were performed on 15 clay samples from soils of the southern U.S and three API reference samples. The mean total percent recovery by this method was excellent (100.14 ± 2.85). Elemental oxide quantities in terms of SiO₂. Al₂O₃, Fe₂O₃, MgO, CaO and K₂O determined by atomic absorption/flame emission (AA/FE) spectroscopy were in good agreement with values measured by x‐ray fluorescence (XRF) on the same subsamples (r = 0.89^* to 0.98^**). but somewhat more variable on subsamples seperated from different pretreatments (r = 0.70^* to 0.97^** ). The method, which has also been tested on 36 additional clay samples from a variety of Kentucky soils with total percent recoveries ranging from 96.5 ‐ 103.5%. demonstrated no bias due to mineralogy with respect to mixed, montmorillonitic. and siliceous classes. This technique presents numerous advantages over other elemental analysis techniques utilizing fusion, dissolution, or XRF spectroscopy with respect to time, effort and cost. With the introduction of inductively‐coupled plasma (ICP) emission spectroscopy. efficiency can be additionally improved.     

Determination of total sulphur in soil using in‐ductively coupled plasma‐atomic emission spectrometry

Abstract

Total sulphur in soils was determined by ignition with a NaHCO₃/Ag₂O mixture, extraction with HC1 and measurement of sulphur by inductively coupled plasma‐atomic emission spectrometry. Significant spectral interference from other extracted elements (mainly iron and aluminium) was corrected using an off‐peak background reading. Recovery of sulphur added to soil as K₂SO₄ was complete and barium did not interfere when added in amounts equivalent to 2000 μg g^‐1 soil. The total sulphur values for a range of New Zealand pastoral soils determined by this method were on average 104% (SEM=1,4) of the values obtained by the NaOBr oxidation method of Tabatabai & Bremner (1). The method enables analysis of relatively large sample numbers.     

Soil Remediation – Mercury Speciation in Soil and Vapor Phase During Thermal Treatment

Spectroscopic (XRD, XPS, ICP-MS and AAS) and microscopic (ESEM) techniques have been used in order to study the chemical effects with emphasis on mercury speciation, during thermal treatment of a mercury contaminated soil. In the untreated soil, mercury was found concentrated in spherical particles, which were successively broken down upon thermal treatment. Hg⁰ and inorganic mercury compounds (presumably HgO(s) and HgSO₄(s)) could be detected. No (CH₃)₂Hg and only traces of CH₃Hg⁺ could be found. The dependence on temperature and heating time indicated that the evaporation of mercury from the soil was partly controlled by diffusion mechanisms. Mercury volatilized in two separate stages during heating; initial elemental vaporization, and subsequent volatilization of the oxide or sulfate phase at higher temperatures (>230°C). By thermal treatment at 470°C and 20 min, a removal of >99% of the mercury could be achieved.     

Short-term variation in the concentration of selected ions within individual tropical rainstorms

Rainwater was collected at the campus of the University of Brunei Darussalam in Bandar Seri Begawan, Brunei Darussalam, using a funnel-in-bottle sampler. Polypropylene bottles were changed at intervals during rainstorm events. The pH and conductivity were determined immediately after collection on aliquots of the sample. Samples were refrigerated at 5°C for subsequent chemical analysis. Analyses for Na, Mg, Ca, Zn and Fe were carried out by means of inductively coupled plasma atomic emission spectroscopy (ICP-AES); Cu and Mn were analysed by graphite furnace atomic absorption spectroscopy (GFAAS); K was analysed using flame atomic emission spectroscopy (FAES); and Cl^–, NO₃ ^– and SO₄ ^2– were analysed by ion chromatography (IC). Concentration versus time profiles are reported for three rainstorm events. All ions exhibited a decrease in concentration during the rainstorm. The first sample contained the highest concentration of ions, consistent with a first-flush effect. The contribution of the initial stages of the shower to the total quantity of ion deposited during the entire rainstorm is quite overwhelming; in many cases 20 to 30% of the mass was deposited in less than 5% of rainstorm duration. On the other hand, the pH and conductivity variation during rainstorms did not exhibit a consistent pattern.     

Pico Level Monitoring of Silver with Modified Hexagonal Mesoporous Compound (MCM-41) and Inductively Coupled Plasma Atomic Emission Spectrometry

A rapid method for the extraction and monitoring of picogram level of silver ions using uniform silanized mesopor (MCM-41) modified by a thiocompound and inductively coupled plasma atomic emission spectrometry (ICP-AES) is presented. The preconcentration factor of the method is 500, and detection limit of the technique for silver is 6.5 pg/ml. The time and the efficiency of the extraction, pH and flow rate, type and minimum amount of acid for stripping of silver from modified MCM-41 was tested. The break through volume of the method was found 2500 ml. The maximum capacity the modified MCM-41 was found to be 11.0 ± 1.2 μg of Ag⁺/mg modified MCM-41.     

Comparison of Lead Extraction and Detection Procedures for Six Canadian Soils

The effects of acid digestion procedures and instrumentation on extracted lead (Pb) concentrations from several soils, including a mildly Pb-contaminated soil, were determined using a two-factor factorial experiment. The two factors were (i) digestion procedure [seven levels: U.S. EPA, AOAC (dry ashing), nitric acid (NA), three aqua regia procedures (AR1, AR2, and AR3), and hydrofluoric acid (HF)] and (ii) instrumentation [two levels: atomic absorption spectrometry (AAS) and inductively coupled plasma (ICP) spectroscopy]. The greatest Pb recovery was obtained when soils were digested with HF and analyzed by AAS. The results suggest that the AOAC procedure (a standard procedure for recovery of soil nutrients and trace elements in Canadian laboratories) and EPA procedure (a standard procedure in American laboratories) may underestimate Pb concentrations in some Atlantic Canadian soil types. The AAS procedure is more accurate than ICP for determining Pb concentrations in soil with a history of PbHAsO₄, at least for Atlantic Canadian soils.     

Mercury Content of Illinois Soils

For a survey of Illinois soils, 101 cores had been collected and analyzed to determine the current and background elemental compositions of Illinois soils. Mercury and other elements were determined in six samples per core, including a surface sample from each core. The mean mercury content in the surface samples was 33 ± 20 g/kg soil, and the background content was 20 ± 9 g/kg. The most probable sources of mercury in these soils were the parent material, and wet and dry deposition of Hg⁰ and Hg²⁺ derived from coal-burning power plants, other industrial plants, and medical and municipal waste incinerators. Mercury-bearing sewage sludge or other fertilizers applied to agricultural fields could have been the local sources of mercury. Although the mercury content correlated with organic carbon content or clay content in individual cores, when all the data were considered, there was no strong correlation between mercury and either the organic carbon or the clay-size content.     

Use of Lithium Metaborate to Determine Total Phosphorus and Other Element Concentrations in Soil,Plant, and Related Materials

Lithium metaborate was examined as an alternative to sodium carbonate for preparing samples for measuring total elements, especially P, by fusion in soil, geological, plant, and other natural organic compounds. The examination also included the effect of two concentrations (0.8 and 3M) of nitric acid used to dissolve the metaborate fusion products as preparation for multiple element analyses by inductively coupled argon plasma atomic emission spectrophotometry (ICP-AES). The three methods compared favorably and were able to reproduce a wide range of element concentration values documented for National Institution of Standards and Technology (NIST) mineral and organic samples. Neither lithium metaborate method measured sulfur (S) acceptably, especially in organic material. The sodium carbonate method traditionally uses sulfuric acid for dissolution, and therefore S measurements cannot be included. Also, sodium (Na) could not be included for the carbonate method. There were detection limit problems for measurement of some elements that are naturally present in small quantities in mineral and organic samples due to relatively low emission intensities for ICP-AES, and the greater sensitivity of ICP-mass spectrometry would be needed. There were only small differences between the two concentrations of nitric acid dissolution after metaborate fusion, but 3 M was adopted for routine use. The metaborate fusion with 3 M nitric acid method performed well on the routine analyses of soil samples. These results show that lithium metaborate is a good alternative to sodium carbonate fusion for the measurement of total P and many other elements (except S) in soil and related materials.