Heléne Österlund

Simultaneous measurements of As, Mo, Sb, V and W using a ferrihydrite diffusive gradients in thin films (DGT) device

The ferrihydrite-backed DGT (diffusive gradients in thin films), recently developed for arsenic and phosphate measurements was, for the first time, characterized with respect to molybdate, antimonate, vanadate and tungstate determination. Arsenate was included in the characterization to allow comparison with literature data and thus provide quality control of the measurements. In addition to laboratory experiments, field measurements were carried out in a natural stream in northern Sweden affected by mine drainage. It was shown that ferrihydrite-DGT is suitable for simultaneous determination of labile arsenic, molybdate, antimonate, vanadate and tungstate over a wide pH range. Diffusion coefficients were estimated using two different methods; diffusion cell and direct uptake to DGT devices in synthetic solutions. Estimations of the coefficients using the direct uptake method were performed between pH 4 and 8. The results from the two methods agreed well irrespective of pH, except for molybdate and antimonate that showed decreased values at pH 8. Adsorption of the analytes to ferrihydrite gel-discs was rapid at all pH values. However, there was a tendency toward lower adsorption affinity for antimonate compared to the other anions. 100% recovery of accumulated analytes was achieved through complete dissolution of the ferrihydrite adsorbent using 1.4 molL(-1) HNO(3) with 0.1 molL(-1) HF. From field sampling it was concluded that the opportunities for accurate antimonate and molybdate determination decrease at pH≥8.7. DGT-labile concentrations were generally lower than dissolved concentrations. Relatively lower DGT concentrations, compared to dissolved (<0.45 μm), were observed under a period when ferric oxide precipitations were detected on the DGT protective filter.

Determination of total chlorine and bromine in solid wastes by sintering and inductively coupled plasma-sector field mass spectrometry

A sample preparation method based on sintering, followed by analysis by inductively coupled plasma-sector field mass spectrometry (ICP-SFMS) for the simultaneous determination of chloride and bromide in diverse and mixed solid wastes, has been evaluated. Samples and reference materials of known composition were mixed with a sintering agent containing Na(2)CO(3) and ZnO and placed in an oven at 560 degrees C for 1h. After cooling, the residues were leached with water prior to a cation-exchange assisted clean-up. Alternatively, a simple microwave-assisted digestion using only nitric acid was applied for comparison. Thereafter the samples were prepared for quantitative analysis by ICP-SFMS. The sintering method was evaluated by analysis of certified reference materials (CRMs) and by comparison with US EPA Method 5050 and ion chromatography with good agreement. Median RSDs for the sintering method were determined to 10% for both chlorine and bromine, and median recovery to 96% and 97%, respectively. Limits of detection (LODs) were 200mg/kg for chlorine and 20mg/kg for bromine. It was concluded that the sintering method is suitable for chlorine and bromine determination in several matrices like sewage sludge, plastics, and edible waste, as well as for waste mixtures. The sintering method was also applied for determination of other elements present in anionic forms, such as sulfur, arsenic, selenium and iodine.

Contribution of organic arsenic species to total arsenic measurements using ferrihydrite-backed diffusive gradients in thin films (DGT)

Environmental context Both the mobility and toxicity of arsenic in natural waters are related to the aqueous species distribution. Passive sampling using ferrihydrite-backed diffusive gradients in thin films (DGT) devices has in previous studies been characterised to measure labile inorganic arsenic, and the possible contribution of organic species has been disregarded. This study shows that the two most prevalent organic arsenic species might be included in DGT measurements, which should be taken into consideration when evaluating DGT data in future studies. Abstract In previous publications discussing arsenic determination using ferrihydrite-backed diffusive gradients in thin films (DGT) devices, organic arsenic forms have been disregarded, even though it is known that the two most prevalent in natural waters, dimethylarsinate (DMA) and monomethylarsonate (MMA), may adsorb to ferrihydrite and thereby be included in the measurement. In this work the accumulation of DMA and MMA, as well as inorganic arsenite and arsenate, to ferrihydrite-backed DGT devices was investigated. It could be demonstrated that MMA, and under acidic conditions also DMA, adsorbed to the binding layer and might therefore contribute to the total mass of measured arsenic. Diffusion coefficients were measured for all four species to enable quantification of DGT-labile concentrations of organic and inorganic arsenic. Elution of the analytes from the ferrihydrite binding layer was performed using 1 mL of 1 M NaOH to facilitate arsenic speciation analysis using chromatographic separation. Average recovery rates were between 87 and 108 %. This study shows that the contribution of DMA and MMA to the total accumulated mass must be taken into consideration when evaluating DGT data in future studies.

Serum/plasma methylmercury determination by isotope dilution gas chromatography : inductively coupled plasma mass spectrometry

A method for the determination of methylmercury in plasma and serum samples was developed. The method uses isotope dilution with (198)Hg-labeled methylmercury, extraction into dichloromethane, back-extraction into water, aqueous-phase ethylation, purge and trap collection, thermal desorption, separation by gas chromatography, and mercury isotope specific detection by inductively coupled plasma mass spectrometry. By spiking 2 mL sample with 1.2 ng tracer, measurements in a concentration interval of (0.007-2.9) μg L(-1) could be performed with uncertainty amplification factors <2. A limit of quantification of 0.03 μg L(-1) was estimated at 10 times the standard deviation of concentrations measured in preparation blanks. Within- and between-run relative standard deviations were <10% at added concentration levels of 0.14 μg L(-1), 0.35 μg L(-1) and 2.8 μg L(-1), with recoveries in the range 82-110%. Application of the method to 50 plasma/serum samples yielded a median (mean; range) concentration of methylmercury of 0.081 (0.091; <0.03-0.19) μg L(-1). This is the first time methylmercury has been directly measured in this kind of specimen, and is therefore the first estimate of a reference range.

Fractionation of trace metals in a contaminated freshwater stream using membrane filtration, ultrafiltration, DGT and transplanted aquatic moss

Four metal speciation and fractionation techniques – DGT (diffusive gradients in thin films), 1-kDa ultrafiltration, 0.22-µm membrane filtration and aquatic moss – were simultaneously applied to a small, contaminated freshwater stream in northern Sweden to investigate differences and similarities between the methods regarding trace metal speciation and their dependence on geochemical water properties. The investigated metals comprise Al, Cd, Co, Cu, Fe, Mn, Ni, and Zn. The normal DGT devices with Chelex cation exchanger were used. Shoots from the aquatic moss Fontinalis antipyretica L ex Hedw. were collected in a non-polluted brook and transplanted to the sampling site for exposure. It was evident that 0.22-µm membrane filtration, 1-kDa ultrafiltration and DGT generally measured different metal fractions where <1-kDa ultrafiltered concentrations were lower than DGT labile concentrations which in turn were lower than <0.22-µm concentrations. The differences between DGT and <1-kDa concentrations indicate the occurrence of labile colloids discriminated by ultrafiltration. Strong correlations between DGT and <1 kDa concentrations were found for Al, Cu, Cd, Co and Zn. Despite a rigorous sample cleaning, retention of particulate matter on the moss samples was revealed by a significant correlation between metal concentrations in moss and particulate Fe. Generally, elevated trace metal concentrations were found in moss exposed at the sampling site compared to reference moss from the non-polluted brook. No significant correlations were found between DGT-labile concentrations and moss concentrations. Supplementary material: DGT – labile concentrations of Al, Cd, Co, Cu, Fe, Mn, Ni and Zn from deployments in Gråbergsbäcken Stream is available online at http://www.geolsoc.org.uk/SUP18566. A hard copy can be obtained from the Society Library.

Contribution of coarse particles from road surfaces to dissolved and particle-bound heavy metal loads in runoff: A laboratory leaching study with synthetic stormwater.

Laboratory leaching experiments were performed to study the potential of coarse street sediments (i.e. >250μm) to release dissolved and particulate-bound heavy metals (i.e. Cd, Cr, Cu, Ni, Pb and Zn) during rainfall/runoff. Towards this end, street sediments were sampled by vacuuming at seven sites in five Swedish cities and the collected sediments were characterized with respect to their physical and chemical properties. In the laboratory, the sediments were combined with synthetic rainwater and subject to agitation by a shaker mimicking particle motion during transport by runoff from street surfaces. As a result of such action, coarse street sediments were found to release significant amounts of heavy metals, which were predominantly (up to 99%) in the particulate bound phase. Thus, in dry weather, coarse street sediments functioned as collectors of fine particles with attached heavy metals, but in wet weather, metal burdens were released by rainfall/runoff processes. The magnitude of such releases depended on the site characteristics (i.e. street cleaning and traffic intensity), particle properties (i.e. organic matter content), and runoff characteristics (pH, and the duration of, and energy input into, sediment/water agitation). The study findings suggest that street cleaning, which preferentially removes coarser sediments, may produce additional environmental benefits by also removing fine contaminated particles attached to coarser materials.

Normalization of Wastewater Quality to Estimate Infiltration/Inflow and Mass Flows of Metals

AbstractThe quality of wastewater varies between catchments due to variation in urbanisation, sewer system properties, and pollution levels. This study was conducted to identify wastewater quality parameters that could be normalized to estimate levels of infiltration/inflow (I/I) in selected catchments and to investigate the geographic origins of metals entering sewer systems. Two sampling campaigns were conducted in the five catchments of the Gothenburg area focusing on 14 water quality parameters. Data from a reference study on domestic wastewater quality to normalize the mass flows associated with pure domestic wastewater was applied. The level of dilution due to I/I in wastewater entering Rya Wastewater Treatment Plant, estimated using Tot-N and Tot-P as indicators, provided the closest fit among the water quality parameters with results obtained by established methods for the two campaigns. The results from the study also indicated which catchments generated nondomestic wastewater with higher mass fl...

Emerging Contaminants: Occurrence, Treatment Efficiency and Accumulation Under Varying Flows

Emerging contaminants became a major topic in water treatment when laboratory detection methods for concentrations at a nanogram-scale improved approximately two decades ago. Research on using ecotechnologies to remove emerging contaminants in variable stormwater and wastewater flows has been conducted for more than a decade, but so far, not all removal mechanisms are well understood and only few setups have been investigated. This chapter summarises the current knowledge, focussing on pesticides and emerging contaminants listed on the watch list of the European Union. However, large-scale investigations are still rare and further research will have to be conducted in this field to enable practitioners to provide recommendations for design and maintenance of treatment facilities in the field of ecotechnologies.

Measurement and Planning–Level Modelling of Retention of Trace Metals (Cu, Pb, Zn) in Soils of Three Urban Drainage Grass Swales

Grass swales are important elements of urban green infrastructure that convey, attenuate and improve the quality of urban runoff mostly through stormwater infiltration into and retention of conveyed pollutants by swale soils. Such processes were addressed in this study, investigating the enrichment of swale soils by ubiquitous urban trace metals, Cu, Pb and Zn. Three swales were selected for study in the City of Lulea (Northern Sweden) and their soils were sampled by coring. Sample cores covered soil depths up to 30 cm, but only the results from the top 5 cm layer characterized by 9–15 samples in each swale are discussed here. After estimating metal mass in this layer in individual swales, such burdens were compared to those modelled by the proprietary StormTac Web model, which estimates annual loads of specific constituents for given land uses and is supported by an extensive database referenced to Swedish environmental conditions. The annual loads modelled for individual swales were multiplied by the swale age to obtain long–term inputs of the trace metals. A good agreement between the measured and modelled loads in soils was obtained and characterized by the ratio Lmod/Lmeas, with an average value of 0.96 and standard deviation of 0.55. Such results suggest the feasibility of assessing the long–term performance of grass swales by modelling trace metal (Cu, Pb, Zn) inputs into swales, estimating the metal loads retained in soils by sampling and analyses, and taking the difference (Lin − Lret) as the exported load.

Estimation of Faecal Indicator Bacteria in Stormwater by Multiple Regression Modelling and Microbial Partitioning to Solids

Concerns about the contamination of sources of drinking water by stormwater motivated a sanitary survey of several urban catchments in the City of Ostersund (Northern Sweden). A data subset from these surveys, comprising of faecal indicator bacteria (FIB) concentrations (E. coli and enterococci), measured for six storm events in three catchments, was used for investigating the feasibility of developing a FIB estimation procedure for the studied catchments by two approaches: (a) Multiple regression models, and (b) microbial partitioning to solids. In regressions, five explanatory variables (associated constituents) were derived from the literature and measured data: stormwater temperature and flow rate, and measurements of total suspended solids (TSS), total phosphorus (TP) and electric conductivity (EC). The obtained regression models were satisfactory for enterococci (regression of modelled FIBs on measured FIB was described by R2 = 0.7), but less acceptable for E. coli (R2 = 0.2). Microbial partitioning to stormwater solids from gully pots was found infeasible; the sediment sampled contained very low FIB counts. Hence, the former method is recommended for further refinement and applications.