Anders Düker

Characterization of the submicrometre phase in surface waters : a review

The need for improved knowledge about the composition and behaviour of solid matter in the colloidal size range (1 nm to 1 µm) in natural waters has been identified by several authors in the literature. The increased interest in these colloids is due to their large impact on the transport, redistribution and bioavailability of numerous chemical compounds (such as trace metals, nutrients and organic pollutants). This paper presents a review of different analytical techniques available for determination of some of the properties of interest (e.g., colloid concentration, size distribution, mineral composition and surface properties). It is obvious that most methods suffer from limitations and that the only feasible way to overcome these problems is by using a combination of different techniques. Sampling in a Swedish lake, as an example, illustrates one promising combination including light scattering and gravimetric analysis for determination of colloid concentration, photon correlation spectroscopy and scanning electron microscopy for size distribution measurements and energy dispersive microscopy, powder X-ray diffraction and infrared spectroscopy in order to obtain information about mineral constituents and general surface properties. Size fractionations were performed by filtration and centrifugation to gain information regarding the distribution of metals and organic matter between dissolved and solid phases. The study indicated, for instance, a seasonality of the size distribution of the colloidal matter, with smallest colloids (range 120–340 nm) found in spring, while the colloid samples during summer and autumn have a size distribution in the range 280–700 nm. This result also illustrates the limitations when using filters with, e.g., a pore size of 0.45 µm for the distinction between particulate and dissolved substances.

Historical pollution of seldom monitored trace elements in Sweden—Part B: Sediment analysis of silver, antimony, thallium and indium

Sediment cores from four boreal and remote lakes in a south to north transect in central Sweden were analysed for acid leachable silver, antimony, thallium and indium in the solid sediment phase and the corresponding porewater. Dating of the cores was made by their content of acid leachable lead and the (206)Pb/(207)Pb ratio, in one lake also by (210)Pb. The impact of diagenesis on element redistribution in the sediments was included and found to be minor except for thallium. The results show lowered concentrations towards the north and most intense accumulation after the Second World War, which is taken as evidence for atmospheric deposition being the primary source. Indium has declining concentrations in recent strata while silver and antimony increase. Thallium has lowered acid-leachable concentrations in recent strata. For all metals the impact of domestic industrialisation as well as the early industrialisation of central Europe is discernible. Only thallium appears to reach a geological background at depths that correspond to the late 18th century. For the other metals elevated levels are concluded.

Separation and Quantification of Tl(I) and Tl(III) in Fresh Water Samples

The two oxidation states of thallium, Tl(I) and Tl(III), were quantified by IC-ICP-MS using complexation of Tl3+ with DTPA (penta-carboxymethyl-diethylenetriamine) and separation on a cation exchange column according to a modification of the method devised by Coetzee et al. In order to avoid successively lowered separation efficiency and loss of resolution during a run, a gradient elution was made using HCl instead of HNO3. With an ultrasonic nebuliser instead of a V-groove nebuliser the limit of detection for Tl(I) and Tl(III) could be lowered from 25 ng/L and 3.0 ng/L to 9.0 ng/L and 0.7 ng/L, respectively, which is adequate for many fresh water systems. The stability of Tl(III) in acidic solutions was found to be concentration dependent, with an initially high reduction rate of Tl(III). Exposure of the sample to light further increased the reduction rate. Addition of DTPA (0.01 mM) and acid (HNO3, 1%) to a sample with 1 μg/L Tl(III) stabilised the Tl(III) content for at least 48 h. Analysis of field samples showed that only acidification is inadequate to maintain the original distribution of Tl(I) and Tl(III). Internal calibration (standard addition) and correction of the analytical signal (205Tl) with a non-ionic internal standard (11B) yielded almost quantitative recoveries of both Tl(I) and Tl(III). A scheme for field sample preparation is proposed, including sampling, storage and pre-analysis treatment.

Re-cycling of remediated soil – Evaluation of leaching tests as tools for characterization

In Sweden, leaching tests with deionized water (D.W.) are utilized in risk assessment of materials entering landfills, but implementation of these results to evaluate the risk of spreading of pollutants in the environment is difficult. One problem is that most leaching procedures only consider heavy metals release, whereas organic pollutants are left out. The aim of the present study was to assess the possible pollutant mitigation in four remediated soils, three with heavy metals and one with polycyclic aromatic hydrocarbons (PAH) contamination. The mitigation was evaluated by standardized batch and column leaching tests utilizing three different leaching solutions: D.W., a weak ionic solution (0.001 M CaCl(2)) and an artificially made soil water (ASW). In general, batch leaching tests implied larger contaminant removal than column leaching test, possibly due to the more rough treatment of the soil particles, and guidelines would at times be exceeded by the batch leaching test but not by column leaching tests. Utilization of CaCl(2) was found to release less heavy metal than D.W., whereas the metals mobilized by ASW were removed from solution by the filtration of soil leachates. Low molecular weight PAH was most efficiently mobilized by CaCl(2), while D.W. worked better for high molecular weight PAH. Despite very low initial PAH-concentrations, tap- and groundwater criteria were exceeded by all leaching solutions.

The effect of light and iron(II)/iron(III) on the distribution of Tl(I)/Tl(III) in fresh water systems.

The distribution of aqueous Tl(I)/Tl(III) as a function of light exposure and solution properties was studied by quantifying the oxidation states after separation with ion chromatography and on-line detection with ICP-MS. Ultraviolet irradiation of aqueous solutions containing 1 microg l(-1) Tl(III) and in equilibrium with the atmosphere increases the reduction rate. In systems with photoreduction of Fe(III)(aq) a quantitative oxidation of Tl(I)(aq) was observed, notably at low pH. The process is reversible, as indicated by formation of Tl(I) when the irradiated systems were kept in the dark. In systems with colloidal silica-stabilised ferrihydrite, UV irradiation also leads to oxidation of Tl(I)(aq), but not quantitatively. It is suggested that adsorption of thallium to the ferrihydrite determines the rate of oxidation. Detectable, but not quantitative, oxidation of Tl(I)(aq) took place when natural water samples with 1 microg l(-1) Tl(I)(aq) were exposed to either sunlight or UV-light. For these samples, the reduction was not quantitative when they were kept in the dark for 24 h. The results suggest that the light dependent iron cycle in fresh water systems strongly influences the redox state of thallium.

Determination of dissociation constants of low molecular weight organic acids by capillary zone electrophoresis and indirect UV detection

SummaryA capillary zone electrophoretic (CZE) method has been developed to determine dissociation constants (pKa) for anionic, non-UV absorbing species in the range 3.3–4.3. The procedure was evaluated by determining the pKa for two well-characterised low molecular weight organic acids: formic and lactic acids. The results correspond well with literature values (in parentheses): formic acid 3.71 (3.75) and lactic acid 3.84 (3.85). The pKa of two polyhydroxycarboxylic acids were also determined, namely 3.64 for gluconic acid and 3.87 for isosaccharinic acid (only poorly described in the literature).

Sediment chronologies of As, Bi, and Ga in Sweden—impact of industrialisation

The acid-leachable amount and pore water concentration of As, Bi and Ga in sediment cores from four remote lakes in a south to north transect in Sweden were used to recapitulate the pollution history of the elements. The diagenetic impact on the element distribution was elucidated from their solid/solution partition and relationships to elements indicative for diagenesis. Dating was made by their acid-leachable lead content in combination with the 206Pb/207Pb ratio. In one of the lakes this approach was validated against dating with 210Pb. The impact of diagenesis on the sediment distribution of theses elements was found to be low enough for a chronological interpretation of the sediment profiles, as evidenced by their ratios to elements indicative of the geological background. A closer examination of the diagenetic impact would however be required if a more detailed chronology is desired. This study has demonstrated that atmospheric deposition of arsenic, bismuth and gallium contributes to the sediment inventory of these elements. The major part of the deposition of arsenic and bismuth took place after the Second World War. For gallium no concentrations exceeding background were detected before circa 1930. Increased levels of arsenic are traceable to circa 1850. For bismuth increased levels are concluded to extend before 1790, i.e., background concentrations were not reached in the present cores. For all elements the atmospheric deposition has been lower towards the north.

Historical pollution of seldom monitored trace elements in Sweden—Part A: Sediment properties and chronological indicators

Sediment cores from four small oligotrophic boreal lakes, with minor acidification, in remote regions of central Sweden were used for historical interpretation of their metal content, with focus on Cu, Cd, Pb and Zn in Lake Stensjön, which has the longest sediment record (at least two centuries according to (210)Pb dating). Comparison is made with the other three lakes. Major and trace elements in lake water, porewater and the acid-leached (HNO(3)) solid sediment phase was analysed with ICP-MS. In addition, general lake water chemistry, TOC and principal anions were measured in the aqueous phases. Redistribution processes were interpreted from geochemical modelling. The solid/solution distribution of pe/pH sensitive elements, indicates a minor diagenetic redistribution and the concentration profiles are therefore suitable for chronological evaluation. The ratios of Al, Ti, Sc and V, indicated a qualitative shift of sedimenting material a century ago, which did not have any impact on the retention of trace elements. Lead had a concentration profile, supported by the (206)Pb/(207)Pb ratio, where it was possible to distinguish preindustrial conditions, early industrialisation in Europe, industrialisation in Sweden, and the use of leaded petrol after the Second World War. Cadmium showed a similar concentration pattern. The zinc profile resembled that of cadmium, but with less enrichment. Local lithogenic sources are believed to be quantitatively important. The solid/solution distribution (K(d)) was independent of depth for all four elements. The sediment concentrations of copper and zinc are not related to early industrialisation but its concentration has doubled since the Second World War.

Rapid Method for ICP-MS Analysos of Plutonium in Sediment Samples

Transuranium elements in the environment are mainly derived from nuclear weapons testing and the nuclear fuel cycle. Of growing concern are illicit nuclear trafficking and the threat of terror acts. The development of rational methods, for environmental monitoring and for tracing sources of nuclear and radioactive materials in the environment, is constantly required. Traditionally, the actinides have been determined by radiometric techniques. These analyses can be time consuming for elements at low concentrations and with long half-lives. This thesis addresses the determination of actinides, especially plutonium, in environmental samples with ICP-QMS (inductively coupled plasma quadrupole mass spectrometry). The ICP-QMS instrument was equipped with an USN (ultrasonic nebuliser), which proved to be a successful combination for the determination of plutonium at low concentrations in acidified solutions after separation with anion exchange. The detection limit for plutonium was in the range 10-30 pg/l with a RSD of 1-10%. The suitability of chemical separation was evaluated for anion exchange, liquid-liquid-extraction and extraction chromatography. The outlined procedure, including sample dissolution, chemical separation and analysis, for determination of actinides in environmental matrices proved to be accurate and reliable. Quality assurance of the procedure was performed during an intercomparison exercise and with reference materials. The detection accuracy has also been validated with α-spectrometry and ICP-SFMS. The procedure has been applied to saline sediments and fresh water sediments as well as several fresh water matrices.