Sondra Klitzke - Academia.edu (original) (raw)

Papers by Sondra Klitzke

Science of The Total Environment, 2014

Engineered inorganic nanoparticles (EINP) from consumers&... more Engineered inorganic nanoparticles (EINP) from consumers' products and industrial applications, especially silver and titanium dioxide nanoparticles (NP), are emitted into the aquatic and terrestrial environments in increasing amounts. However, the current knowledge on their environmental fate and biological effects is diverse and renders reliable predictions complicated. This review critically evaluates existing knowledge on colloidal aging mechanisms, biological functioning and transport of Ag NP and TiO2 NP in water and soil and it discusses challenges for concepts, experimental approaches and analytical methods in order to obtain a comprehensive understanding of the processes linking NP fate and effects. Ag NP undergo dissolution and oxidation with Ag2S as a thermodynamically determined endpoint. Nonetheless, Ag NP also undergo colloidal transformations in the nanoparticulate state and may act as carriers for other substances. Ag NP and TiO2 NP can have adverse biological effects on organisms. Whereas Ag NP reveal higher colloidal stability and mobility, the efficiency of NOM as a stabilizing agent is greater towards TiO2 NP than towards Ag NP, and multivalent cations can dominate the colloidal behavior over NOM. Many of the past analytical obstacles have been overcome just recently. Single particle ICP-MS based methods in combination with field flow fractionation techniques and hydrodynamic chromatography have the potential to fill the gaps currently hampering a comprehensive understanding of fate and effects also at a low field relevant concentrations. These analytical developments will allow for mechanistically orientated research and transfer to a larger set of EINP. This includes separating processes driven by NP specific properties and bulk chemical properties, categorization of effect-triggering pathways directing the EINP effects towards specific recipients, and identification of dominant environmental parameters triggering fate and effect of EINP in specific ecosystems (e.g. soil, lake, or riverine systems).

Environmental Chemistry, 2012

Environmental context. The size of soil colloids is -among other characteristics -crucial for the... more Environmental context. The size of soil colloids is -among other characteristics -crucial for the mobility of associated contaminants. We analysed the effect of liming on the size of colloids mobilised from strongly contaminated shooting-range soils using multi-stage tangential ultrafiltration (MTUF) for the size fractionation of dispersed soil colloids. Our results indicate the high analytical potential of MTUF and show that liming induces the aggregation of colloids, thereby decreasing the mobilisation of colloid-bound Sb and As, but increasing colloidal Pb.

Journal of contaminant hydrology, 2016

Engineered nanoparticles released into soils may be coated with humic substances, potentially mod... more Engineered nanoparticles released into soils may be coated with humic substances, potentially modifying their surface properties. Due to their amphiphilic nature, humic coating is expected to affect interaction of nanoparticle at the air-water interface. In this study, we explored the roles of the air-water interface and solid-water interface as potential sites for nanoparticle attachment and the importance of hydrophobic interactions for nanoparticle attachment at the air-water interface. By exposing Ag nanoparticles to soil solution extracted from the upper soil horizon of a floodplain soil, the mobility of the resulting "soil-aged" Ag nanoparticles was investigated and compared with the mobility of citrate-coated Ag nanoparticles as investigated in an earlier study. The mobility was determined as a function of hydrologic conditions and solution chemistry using column breakthrough curves and numerical modeling. Specifically, we compared the mobility of both types of nano...

Water Research, 2011

Cation bridging Cation exchange Ionic strength River bank filtration Cyanotoxin Subsurface passag... more Cation bridging Cation exchange Ionic strength River bank filtration Cyanotoxin Subsurface passage a b s t r a c t

International Journal of Hygiene and Environmental Health, Sep 26, 2014

To protect groundwater as a drinking water resource from microbiological contamination, protectio... more To protect groundwater as a drinking water resource from microbiological contamination, protection zones are installed. While travelling through these zones, concentrations of potential pathogens should decline to levels that pose no risks to human health. Removal of viruses during subsurface passage is influenced by physicochemical conditions, such as oxygen concentration, which also affects virus survival. The aim of our study was to evaluate the effect of redox conditions on the removal of viruses during sand filtration. Experiments in glass columns filled with medium-grained sand were conducted to investigate virus removal in the presence and absence of dissolved oxygen. Bacteriophages MS2 and PhiX174, as surrogates for human enteric viruses were spiked in pulsed or in continuous mode and pumped through the columns at a filter velocity of about 1 m/d. Virus breakthrough curves were analyzed by calculating total viral elimination and fitted using one-dimensional transport models (CXTFIT and HYDRUS-1D). While short-term experiments with pulsed virus application showed only small differences with regard to virus removal under oxic and anoxic conditions, a long-term experiment with continuous dosing revealed a clearly lower elimination of viruses under anoxic conditions. These findings suggest that less inactivation and less adsorption of viruses in anoxic environments affect their removal. Therefore, in risk assessment studies aimed to secure drinking water resources from viral contamination and optimization of protection zones, the oxic and anoxic conditions in the subsurface should also be considered.

Geochimica Et Cosmochimica Acta Supplement, Jun 1, 2009

The Science of the total environment, Jan 4, 2015

Redox conditions are known to affect the fate of viruses in porous media. Several studies report ... more Redox conditions are known to affect the fate of viruses in porous media. Several studies report the relevance of colloid-facilitated virus transport in the subsurface, but detailed studies on the effect of anoxic conditions on virus retention in natural sediments are still missing. Therefore, we investigated the fate of viruses in natural flood plain sediments with different sesquioxide contents under anoxic conditions by considering sorption to the solid phase, sorption to mobilized colloids, and inactivation in the aqueous phase. Batch experiments were conducted under oxic and anoxic conditions at pH values between 5.1 and 7.6, using bacteriophages MS2 and PhiX174 as model viruses. In addition to free and colloid-associated bacteriophages, dissolved and colloidal concentrations of Fe, Al and organic C as well as dissolved Ca were determined. Results showed that regardless of redox conditions, bacteriophages did not adsorb to mobilized colloids, even under favourable charge condit...

Science of The Total Environment, 2014

Soil solution reduces the release of ionic silver from Ag NP.

Science of The Total Environment, 2014

Engineered inorganic nanoparticles (EINP) from consumers&... more Engineered inorganic nanoparticles (EINP) from consumers' products and industrial applications, especially silver and titanium dioxide nanoparticles (NP), are emitted into the aquatic and terrestrial environments in increasing amounts. However, the current knowledge on their environmental fate and biological effects is diverse and renders reliable predictions complicated. This review critically evaluates existing knowledge on colloidal aging mechanisms, biological functioning and transport of Ag NP and TiO2 NP in water and soil and it discusses challenges for concepts, experimental approaches and analytical methods in order to obtain a comprehensive understanding of the processes linking NP fate and effects. Ag NP undergo dissolution and oxidation with Ag2S as a thermodynamically determined endpoint. Nonetheless, Ag NP also undergo colloidal transformations in the nanoparticulate state and may act as carriers for other substances. Ag NP and TiO2 NP can have adverse biological effects on organisms. Whereas Ag NP reveal higher colloidal stability and mobility, the efficiency of NOM as a stabilizing agent is greater towards TiO2 NP than towards Ag NP, and multivalent cations can dominate the colloidal behavior over NOM. Many of the past analytical obstacles have been overcome just recently. Single particle ICP-MS based methods in combination with field flow fractionation techniques and hydrodynamic chromatography have the potential to fill the gaps currently hampering a comprehensive understanding of fate and effects also at a low field relevant concentrations. These analytical developments will allow for mechanistically orientated research and transfer to a larger set of EINP. This includes separating processes driven by NP specific properties and bulk chemical properties, categorization of effect-triggering pathways directing the EINP effects towards specific recipients, and identification of dominant environmental parameters triggering fate and effect of EINP in specific ecosystems (e.g. soil, lake, or riverine systems).

Science of The Total Environment, 2014

The widespread use of engineered inorganic nanoparticles (EINP) leads to a growing risk for an un... more The widespread use of engineered inorganic nanoparticles (EINP) leads to a growing risk for an unintended release into the environment. Despite the good characterization of EINP in regard to their function scale and the application areas, there is still a gap of knowledge concerning their behaviour in the different environmental compartments. Due to their high surface to volume ratio, surface properties and existence or development of a coating are of high importance for their stability and transport behaviour. However, analytical methods to investigate organic coatings on nanoparticles in aqueous media are scarce. We used Raman microspectroscopy in combination with surface-enhanced Raman scattering (SERS) to investigate humic acid coatings on silver nanoparticles under environmentally relevant conditions and in real world samples. This setup is more challenging than previous mechanistic studies using SERS to characterize the humic acids in tailored settings where only one type of organic matter is present and the concentrations of the nanoparticles can be easily adjusted to the experimental needs. SERS offers the unique opportunity to work with little sample preparation directly with liquid samples, thus significantly reducing artefacts. SERS spectra of different natural organic matter brought into contact with silver nanoparticles indicate humic acid in close proximity to the nanoparticles. This coating was also present after several washing steps by centrifugation and resuspension in deionized water and after an increase in ionic strength.

International Journal of Hygiene and Environmental Health, 2014

To protect groundwater as a drinking water resource from microbiological contamination, protectio... more To protect groundwater as a drinking water resource from microbiological contamination, protection zones are installed. While travelling through these zones, concentrations of potential pathogens should decline to levels that pose no risks to human health. Removal of viruses during subsurface passage is influenced by physicochemical conditions, such as oxygen concentration, which also affects virus survival. The aim of our study was to evaluate the effect of redox conditions on the removal of viruses during sand filtration. Experiments in glass columns filled with medium-grained sand were conducted to investigate virus removal in the presence and absence of dissolved oxygen. Bacteriophages MS2 and PhiX174, as surrogates for human enteric viruses were spiked in pulsed or in continuous mode and pumped through the columns at a filter velocity of about 1 m/d. Virus breakthrough curves were analyzed by calculating total viral elimination and fitted using one-dimensional transport models (CXTFIT and HYDRUS-1D). While short-term experiments with pulsed virus application showed only small differences with regard to virus removal under oxic and anoxic conditions, a long-term experiment with continuous dosing revealed a clearly lower elimination of viruses under anoxic conditions. These findings suggest that less inactivation and less adsorption of viruses in anoxic environments affect their removal. Therefore, in risk assessment studies aimed to secure drinking water resources from viral contamination and optimization of protection zones, the oxic and anoxic conditions in the subsurface should also be considered.

Water, Air, and Soil Pollution, 2005

Silver (Ag) and thallium (Tl) are non-essential elements that are toxic to many biota at trace le... more Silver (Ag) and thallium (Tl) are non-essential elements that are toxic to many biota at trace levels, but are rarely studied in soil environments. Ag sorbs strongly to soils, especially those rich in organic matter whereas Tl sorption is influenced by clay content. However, the mobility and bioavailability of Tl and Ag are ultimately affected less by the soil sorptive capacity than by the ease with which these elements desorb from soils. In that context, the strength of Ag and Tl sorption to illite-rich mineral soils with differing textures and an organic peaty-muck soil, from New York State, was investigated by studying their desorption using, as a sink for the metals, a resin (Duolite G-73) containing a thiol functional group. Desorption was monitored over time (1 h, 4 weeks) from soils previously equilibrated with Tl + or Ag + for 24 h (steady-state) or for up to 1 year. Within 24 h, 60% of the sorbed Tl was recovered by the resin. Within 2 weeks, 80-100% of the Tl desorbed from all four soils equilibrated for both 24 h and 1 year periods. Ag was not effectively recovered from the resin. However, qualitative review indicates that more Ag was desorbed after the 24 h sorption period than after the 1 year period. More Ag desorbed from the sandy soil than from the peaty-muck soil or the mineral soils with higher clay contents. However, within two weeks silver was mobilized from the peaty-muck soil. The observed release of Ag and Tl from soils, coupled with their toxicity at trace levels to a broad range of soil organisms, suggests that they may pose an environmental concern when present in soils at elevated concentrations.

Water Research, 2011

Cation bridging Cation exchange Ionic strength River bank filtration Cyanotoxin Subsurface passag... more Cation bridging Cation exchange Ionic strength River bank filtration Cyanotoxin Subsurface passage a b s t r a c t

Water Research, 2012

Sand filtration Cyanobacterial toxin Sediment preconditioning a b s t r a c t One possible conseq... more Sand filtration Cyanobacterial toxin Sediment preconditioning a b s t r a c t One possible consequence of increasing water temperatures due to global warming in middle Europe is the proliferation of cylindrospermopsin-producing species from warmer regions. This may lead to more frequent and increased cylindrospermopsin (CYN) concentrations in surface waters. Hence, efficient elimination of CYN is important where contaminated surface waters are used as a resource for drinking water production via sediment passage. Sediments are often characterized by a lack of oxygen and low temperature (i.e. approx. 10 C). The presence of dissolved organic carbon (DOC) is not only known to enhance but also to retard contaminant degradation by influencing the extent of lag phases. So far CYN degradation has only been investigated under oxic conditions and at room temperature. Therefore, the aim of our experiments was to understand CYN degradation, focusing on the effects of i) anoxic conditions, ii) low temperature (i.e. 10 C) in comparison to room temperature (23 AE 4 C) and iii) DOC on lag phases. We used two natural sandy sediments (virgin and preconditioned) and surface water to conduct closed-loop column experiments. Anoxic conditions either inhibited CYN degradation completely or retarded CYN breakdown in comparison to oxic conditions (T 1/2 (oxic) ¼ 2.4 days, T 1/2 (anoxic) ¼ 23.6 days). A decrease in temperature from 20 C to 10 C slowed down degradation rates by a factor of 10. The presence of DOC shortened lag phases in virgin sediments at room temperature but induced a lag phase in preconditioned sediments at 10 C, indicating potential substrate competition. These results show that information on physico-chemical conditions in sediments is crucial to assess the risk of CYN breakthrough. ª

Toxicon, 2010

Recent results show that cylindrospermopsin is more frequent and widespread in surface waters tha... more Recent results show that cylindrospermopsin is more frequent and widespread in surface waters than previously assumed. Studies on the fate of CYN in sediments are lacking, but this is important if these resources are used for drinking-water production via sediment passage. Therefore, the aim of our study was to determine a) CYN retention in two sandy sediments as a function of flow rate, CYN concentration, the presence of DOM and the content of fines (1% and 4%, respectively) and b) the influence of sediment preconditioning and DOM composition of the water (aquatic DOM versus DOM released from lysed cells) on CYN degradation. Retention of CYN proved negligible under the investigated conditions. Degradation in virgin sediments showed the highest lag phases (20 days). Preconditioned sediments showed no lag phase. The presence of aquatic DOM yielded highest degradation rates (k 1 ¼ 0.46 and 0.49 day À1 ) without a lag phase. Readily available organic carbon sources were preferentially metabolized and hence induced a lag phase. Thus, the presence and composition of DOM in the water proved important for both CYN degradation rates in preconditioned sediments and for the lag phase. Cylindrospermopsin degradation took place solely in the sediment and not in the water body.

Journal of Environment Quality, 2007

Drying of soil may increase the hydrophobicity of soil and affect the mobilization of colloids af... more Drying of soil may increase the hydrophobicity of soil and affect the mobilization of colloids after re-wetting. Results of previous research suggest that colloid hydrophobicity is an important parameter in controlling the retention of colloids and colloid-associated substances in soils. We tested the hypothesis that air-drying of soil samples increases the hydrophobicity of water-dispersible colloids and whether air-drying affects the mobilization of colloid-associated heavy metals. We performed batch experiments with field-moist and air-dried (25°C) soils from a former sewage farm (sandy loam), a municipal park (loamy sand), and a shooting range site (loamy sand with 25% C org ). The filtered suspensions (,1.2 mm) were analyzed for concentrations of dissolved and colloidal organic C and heavy metals (Cu, Cd, Pb, Zn), average colloid size, zeta potential, and turbidity. The hydrophobicity of colloids was determined by their partitioning between a hydrophobic solid and a hydrophilic aqueous phase. Drying increased hydrophobicity of the solid phase but did not affect the hydrophobicity of the dispersed colloids. Drying decreased the amount of mobilized mineral and (organo-)mineral colloids in the sewage farm soils but increased the mobilization of organic colloids in the C-rich shooting range soil. Dried samples released less colloid-bound Cd and Zn than field-moist samples. Drying-induced mobilization of dissolved organic C caused a redistribution of Cu from the colloidal to the dissolved phase. We conclude that drying-induced colloid mobilization is not caused by a change in the physicochemical properties of the colloids. Therefore, it is likely that the mobilization of colloids in the field is caused by increasing shear forces or the disintegration of aggregates.

European Journal of Soil Science, 2008

Colloids can play an important role in the leaching of lead (Pb) in soils, and liming to increase... more Colloids can play an important role in the leaching of lead (Pb) in soils, and liming to increase pH may produce conditions conducive to colloid release. We studied the effect of pH and the role of counterion valency on the mobilization of Pb in two topsoil horizons of a former shooting range. In batch experiments, the release of both dissolved and colloidal Pb was studied at a pH range between 3 and 7. The pH was adjusted with solutions of nitric acid (pH 3) and KOH and Ca(OH) 2 (pH 4-7) and the chemical composition, size and charge of the mobilized colloids were determined. In the presence of the monovalent K þ -ion concentrations of colloidal and dissolved Pb increased markedly with increasing pH. Colloids were stabilized not only by electrostatic but also by steric repulsion. Organic colloids seem to dominate at low pH of the KOH-treatment; at pH > 4 mineral particles were also dispersed. Even though the presence of the Ca 2þ ion reduced the concentrations of colloidal Pb more than did the K þ ion, our results of the Ca(OH) 2 treatment show that the relevance of both colloidal and dissolved Pb increases at a pH of about 5.8. Risk assessment on limed sites should therefore take into account both dissolved and colloidal Pb in judging the likelihood of Pb leaching.

Science of The Total Environment, 2014

Engineered inorganic nanoparticles (EINP) from consumers&... more Engineered inorganic nanoparticles (EINP) from consumers' products and industrial applications, especially silver and titanium dioxide nanoparticles (NP), are emitted into the aquatic and terrestrial environments in increasing amounts. However, the current knowledge on their environmental fate and biological effects is diverse and renders reliable predictions complicated. This review critically evaluates existing knowledge on colloidal aging mechanisms, biological functioning and transport of Ag NP and TiO2 NP in water and soil and it discusses challenges for concepts, experimental approaches and analytical methods in order to obtain a comprehensive understanding of the processes linking NP fate and effects. Ag NP undergo dissolution and oxidation with Ag2S as a thermodynamically determined endpoint. Nonetheless, Ag NP also undergo colloidal transformations in the nanoparticulate state and may act as carriers for other substances. Ag NP and TiO2 NP can have adverse biological effects on organisms. Whereas Ag NP reveal higher colloidal stability and mobility, the efficiency of NOM as a stabilizing agent is greater towards TiO2 NP than towards Ag NP, and multivalent cations can dominate the colloidal behavior over NOM. Many of the past analytical obstacles have been overcome just recently. Single particle ICP-MS based methods in combination with field flow fractionation techniques and hydrodynamic chromatography have the potential to fill the gaps currently hampering a comprehensive understanding of fate and effects also at a low field relevant concentrations. These analytical developments will allow for mechanistically orientated research and transfer to a larger set of EINP. This includes separating processes driven by NP specific properties and bulk chemical properties, categorization of effect-triggering pathways directing the EINP effects towards specific recipients, and identification of dominant environmental parameters triggering fate and effect of EINP in specific ecosystems (e.g. soil, lake, or riverine systems).

Environmental Chemistry, 2012

Environmental context. The size of soil colloids is -among other characteristics -crucial for the... more Environmental context. The size of soil colloids is -among other characteristics -crucial for the mobility of associated contaminants. We analysed the effect of liming on the size of colloids mobilised from strongly contaminated shooting-range soils using multi-stage tangential ultrafiltration (MTUF) for the size fractionation of dispersed soil colloids. Our results indicate the high analytical potential of MTUF and show that liming induces the aggregation of colloids, thereby decreasing the mobilisation of colloid-bound Sb and As, but increasing colloidal Pb.

Journal of contaminant hydrology, 2016

Engineered nanoparticles released into soils may be coated with humic substances, potentially mod... more Engineered nanoparticles released into soils may be coated with humic substances, potentially modifying their surface properties. Due to their amphiphilic nature, humic coating is expected to affect interaction of nanoparticle at the air-water interface. In this study, we explored the roles of the air-water interface and solid-water interface as potential sites for nanoparticle attachment and the importance of hydrophobic interactions for nanoparticle attachment at the air-water interface. By exposing Ag nanoparticles to soil solution extracted from the upper soil horizon of a floodplain soil, the mobility of the resulting "soil-aged" Ag nanoparticles was investigated and compared with the mobility of citrate-coated Ag nanoparticles as investigated in an earlier study. The mobility was determined as a function of hydrologic conditions and solution chemistry using column breakthrough curves and numerical modeling. Specifically, we compared the mobility of both types of nano...

Water Research, 2011

Cation bridging Cation exchange Ionic strength River bank filtration Cyanotoxin Subsurface passag... more Cation bridging Cation exchange Ionic strength River bank filtration Cyanotoxin Subsurface passage a b s t r a c t

International Journal of Hygiene and Environmental Health, Sep 26, 2014

To protect groundwater as a drinking water resource from microbiological contamination, protectio... more To protect groundwater as a drinking water resource from microbiological contamination, protection zones are installed. While travelling through these zones, concentrations of potential pathogens should decline to levels that pose no risks to human health. Removal of viruses during subsurface passage is influenced by physicochemical conditions, such as oxygen concentration, which also affects virus survival. The aim of our study was to evaluate the effect of redox conditions on the removal of viruses during sand filtration. Experiments in glass columns filled with medium-grained sand were conducted to investigate virus removal in the presence and absence of dissolved oxygen. Bacteriophages MS2 and PhiX174, as surrogates for human enteric viruses were spiked in pulsed or in continuous mode and pumped through the columns at a filter velocity of about 1 m/d. Virus breakthrough curves were analyzed by calculating total viral elimination and fitted using one-dimensional transport models (CXTFIT and HYDRUS-1D). While short-term experiments with pulsed virus application showed only small differences with regard to virus removal under oxic and anoxic conditions, a long-term experiment with continuous dosing revealed a clearly lower elimination of viruses under anoxic conditions. These findings suggest that less inactivation and less adsorption of viruses in anoxic environments affect their removal. Therefore, in risk assessment studies aimed to secure drinking water resources from viral contamination and optimization of protection zones, the oxic and anoxic conditions in the subsurface should also be considered.

Geochimica Et Cosmochimica Acta Supplement, Jun 1, 2009

The Science of the total environment, Jan 4, 2015

Redox conditions are known to affect the fate of viruses in porous media. Several studies report ... more Redox conditions are known to affect the fate of viruses in porous media. Several studies report the relevance of colloid-facilitated virus transport in the subsurface, but detailed studies on the effect of anoxic conditions on virus retention in natural sediments are still missing. Therefore, we investigated the fate of viruses in natural flood plain sediments with different sesquioxide contents under anoxic conditions by considering sorption to the solid phase, sorption to mobilized colloids, and inactivation in the aqueous phase. Batch experiments were conducted under oxic and anoxic conditions at pH values between 5.1 and 7.6, using bacteriophages MS2 and PhiX174 as model viruses. In addition to free and colloid-associated bacteriophages, dissolved and colloidal concentrations of Fe, Al and organic C as well as dissolved Ca were determined. Results showed that regardless of redox conditions, bacteriophages did not adsorb to mobilized colloids, even under favourable charge condit...

Science of The Total Environment, 2014

Soil solution reduces the release of ionic silver from Ag NP.

Science of The Total Environment, 2014

Engineered inorganic nanoparticles (EINP) from consumers&... more Engineered inorganic nanoparticles (EINP) from consumers' products and industrial applications, especially silver and titanium dioxide nanoparticles (NP), are emitted into the aquatic and terrestrial environments in increasing amounts. However, the current knowledge on their environmental fate and biological effects is diverse and renders reliable predictions complicated. This review critically evaluates existing knowledge on colloidal aging mechanisms, biological functioning and transport of Ag NP and TiO2 NP in water and soil and it discusses challenges for concepts, experimental approaches and analytical methods in order to obtain a comprehensive understanding of the processes linking NP fate and effects. Ag NP undergo dissolution and oxidation with Ag2S as a thermodynamically determined endpoint. Nonetheless, Ag NP also undergo colloidal transformations in the nanoparticulate state and may act as carriers for other substances. Ag NP and TiO2 NP can have adverse biological effects on organisms. Whereas Ag NP reveal higher colloidal stability and mobility, the efficiency of NOM as a stabilizing agent is greater towards TiO2 NP than towards Ag NP, and multivalent cations can dominate the colloidal behavior over NOM. Many of the past analytical obstacles have been overcome just recently. Single particle ICP-MS based methods in combination with field flow fractionation techniques and hydrodynamic chromatography have the potential to fill the gaps currently hampering a comprehensive understanding of fate and effects also at a low field relevant concentrations. These analytical developments will allow for mechanistically orientated research and transfer to a larger set of EINP. This includes separating processes driven by NP specific properties and bulk chemical properties, categorization of effect-triggering pathways directing the EINP effects towards specific recipients, and identification of dominant environmental parameters triggering fate and effect of EINP in specific ecosystems (e.g. soil, lake, or riverine systems).

Science of The Total Environment, 2014

The widespread use of engineered inorganic nanoparticles (EINP) leads to a growing risk for an un... more The widespread use of engineered inorganic nanoparticles (EINP) leads to a growing risk for an unintended release into the environment. Despite the good characterization of EINP in regard to their function scale and the application areas, there is still a gap of knowledge concerning their behaviour in the different environmental compartments. Due to their high surface to volume ratio, surface properties and existence or development of a coating are of high importance for their stability and transport behaviour. However, analytical methods to investigate organic coatings on nanoparticles in aqueous media are scarce. We used Raman microspectroscopy in combination with surface-enhanced Raman scattering (SERS) to investigate humic acid coatings on silver nanoparticles under environmentally relevant conditions and in real world samples. This setup is more challenging than previous mechanistic studies using SERS to characterize the humic acids in tailored settings where only one type of organic matter is present and the concentrations of the nanoparticles can be easily adjusted to the experimental needs. SERS offers the unique opportunity to work with little sample preparation directly with liquid samples, thus significantly reducing artefacts. SERS spectra of different natural organic matter brought into contact with silver nanoparticles indicate humic acid in close proximity to the nanoparticles. This coating was also present after several washing steps by centrifugation and resuspension in deionized water and after an increase in ionic strength.

International Journal of Hygiene and Environmental Health, 2014

To protect groundwater as a drinking water resource from microbiological contamination, protectio... more To protect groundwater as a drinking water resource from microbiological contamination, protection zones are installed. While travelling through these zones, concentrations of potential pathogens should decline to levels that pose no risks to human health. Removal of viruses during subsurface passage is influenced by physicochemical conditions, such as oxygen concentration, which also affects virus survival. The aim of our study was to evaluate the effect of redox conditions on the removal of viruses during sand filtration. Experiments in glass columns filled with medium-grained sand were conducted to investigate virus removal in the presence and absence of dissolved oxygen. Bacteriophages MS2 and PhiX174, as surrogates for human enteric viruses were spiked in pulsed or in continuous mode and pumped through the columns at a filter velocity of about 1 m/d. Virus breakthrough curves were analyzed by calculating total viral elimination and fitted using one-dimensional transport models (CXTFIT and HYDRUS-1D). While short-term experiments with pulsed virus application showed only small differences with regard to virus removal under oxic and anoxic conditions, a long-term experiment with continuous dosing revealed a clearly lower elimination of viruses under anoxic conditions. These findings suggest that less inactivation and less adsorption of viruses in anoxic environments affect their removal. Therefore, in risk assessment studies aimed to secure drinking water resources from viral contamination and optimization of protection zones, the oxic and anoxic conditions in the subsurface should also be considered.

Water, Air, and Soil Pollution, 2005

Silver (Ag) and thallium (Tl) are non-essential elements that are toxic to many biota at trace le... more Silver (Ag) and thallium (Tl) are non-essential elements that are toxic to many biota at trace levels, but are rarely studied in soil environments. Ag sorbs strongly to soils, especially those rich in organic matter whereas Tl sorption is influenced by clay content. However, the mobility and bioavailability of Tl and Ag are ultimately affected less by the soil sorptive capacity than by the ease with which these elements desorb from soils. In that context, the strength of Ag and Tl sorption to illite-rich mineral soils with differing textures and an organic peaty-muck soil, from New York State, was investigated by studying their desorption using, as a sink for the metals, a resin (Duolite G-73) containing a thiol functional group. Desorption was monitored over time (1 h, 4 weeks) from soils previously equilibrated with Tl + or Ag + for 24 h (steady-state) or for up to 1 year. Within 24 h, 60% of the sorbed Tl was recovered by the resin. Within 2 weeks, 80-100% of the Tl desorbed from all four soils equilibrated for both 24 h and 1 year periods. Ag was not effectively recovered from the resin. However, qualitative review indicates that more Ag was desorbed after the 24 h sorption period than after the 1 year period. More Ag desorbed from the sandy soil than from the peaty-muck soil or the mineral soils with higher clay contents. However, within two weeks silver was mobilized from the peaty-muck soil. The observed release of Ag and Tl from soils, coupled with their toxicity at trace levels to a broad range of soil organisms, suggests that they may pose an environmental concern when present in soils at elevated concentrations.

Water Research, 2011

Cation bridging Cation exchange Ionic strength River bank filtration Cyanotoxin Subsurface passag... more Cation bridging Cation exchange Ionic strength River bank filtration Cyanotoxin Subsurface passage a b s t r a c t

Water Research, 2012

Sand filtration Cyanobacterial toxin Sediment preconditioning a b s t r a c t One possible conseq... more Sand filtration Cyanobacterial toxin Sediment preconditioning a b s t r a c t One possible consequence of increasing water temperatures due to global warming in middle Europe is the proliferation of cylindrospermopsin-producing species from warmer regions. This may lead to more frequent and increased cylindrospermopsin (CYN) concentrations in surface waters. Hence, efficient elimination of CYN is important where contaminated surface waters are used as a resource for drinking water production via sediment passage. Sediments are often characterized by a lack of oxygen and low temperature (i.e. approx. 10 C). The presence of dissolved organic carbon (DOC) is not only known to enhance but also to retard contaminant degradation by influencing the extent of lag phases. So far CYN degradation has only been investigated under oxic conditions and at room temperature. Therefore, the aim of our experiments was to understand CYN degradation, focusing on the effects of i) anoxic conditions, ii) low temperature (i.e. 10 C) in comparison to room temperature (23 AE 4 C) and iii) DOC on lag phases. We used two natural sandy sediments (virgin and preconditioned) and surface water to conduct closed-loop column experiments. Anoxic conditions either inhibited CYN degradation completely or retarded CYN breakdown in comparison to oxic conditions (T 1/2 (oxic) ¼ 2.4 days, T 1/2 (anoxic) ¼ 23.6 days). A decrease in temperature from 20 C to 10 C slowed down degradation rates by a factor of 10. The presence of DOC shortened lag phases in virgin sediments at room temperature but induced a lag phase in preconditioned sediments at 10 C, indicating potential substrate competition. These results show that information on physico-chemical conditions in sediments is crucial to assess the risk of CYN breakthrough. ª

Toxicon, 2010

Recent results show that cylindrospermopsin is more frequent and widespread in surface waters tha... more Recent results show that cylindrospermopsin is more frequent and widespread in surface waters than previously assumed. Studies on the fate of CYN in sediments are lacking, but this is important if these resources are used for drinking-water production via sediment passage. Therefore, the aim of our study was to determine a) CYN retention in two sandy sediments as a function of flow rate, CYN concentration, the presence of DOM and the content of fines (1% and 4%, respectively) and b) the influence of sediment preconditioning and DOM composition of the water (aquatic DOM versus DOM released from lysed cells) on CYN degradation. Retention of CYN proved negligible under the investigated conditions. Degradation in virgin sediments showed the highest lag phases (20 days). Preconditioned sediments showed no lag phase. The presence of aquatic DOM yielded highest degradation rates (k 1 ¼ 0.46 and 0.49 day À1 ) without a lag phase. Readily available organic carbon sources were preferentially metabolized and hence induced a lag phase. Thus, the presence and composition of DOM in the water proved important for both CYN degradation rates in preconditioned sediments and for the lag phase. Cylindrospermopsin degradation took place solely in the sediment and not in the water body.

Journal of Environment Quality, 2007

Drying of soil may increase the hydrophobicity of soil and affect the mobilization of colloids af... more Drying of soil may increase the hydrophobicity of soil and affect the mobilization of colloids after re-wetting. Results of previous research suggest that colloid hydrophobicity is an important parameter in controlling the retention of colloids and colloid-associated substances in soils. We tested the hypothesis that air-drying of soil samples increases the hydrophobicity of water-dispersible colloids and whether air-drying affects the mobilization of colloid-associated heavy metals. We performed batch experiments with field-moist and air-dried (25°C) soils from a former sewage farm (sandy loam), a municipal park (loamy sand), and a shooting range site (loamy sand with 25% C org ). The filtered suspensions (,1.2 mm) were analyzed for concentrations of dissolved and colloidal organic C and heavy metals (Cu, Cd, Pb, Zn), average colloid size, zeta potential, and turbidity. The hydrophobicity of colloids was determined by their partitioning between a hydrophobic solid and a hydrophilic aqueous phase. Drying increased hydrophobicity of the solid phase but did not affect the hydrophobicity of the dispersed colloids. Drying decreased the amount of mobilized mineral and (organo-)mineral colloids in the sewage farm soils but increased the mobilization of organic colloids in the C-rich shooting range soil. Dried samples released less colloid-bound Cd and Zn than field-moist samples. Drying-induced mobilization of dissolved organic C caused a redistribution of Cu from the colloidal to the dissolved phase. We conclude that drying-induced colloid mobilization is not caused by a change in the physicochemical properties of the colloids. Therefore, it is likely that the mobilization of colloids in the field is caused by increasing shear forces or the disintegration of aggregates.

European Journal of Soil Science, 2008

Colloids can play an important role in the leaching of lead (Pb) in soils, and liming to increase... more Colloids can play an important role in the leaching of lead (Pb) in soils, and liming to increase pH may produce conditions conducive to colloid release. We studied the effect of pH and the role of counterion valency on the mobilization of Pb in two topsoil horizons of a former shooting range. In batch experiments, the release of both dissolved and colloidal Pb was studied at a pH range between 3 and 7. The pH was adjusted with solutions of nitric acid (pH 3) and KOH and Ca(OH) 2 (pH 4-7) and the chemical composition, size and charge of the mobilized colloids were determined. In the presence of the monovalent K þ -ion concentrations of colloidal and dissolved Pb increased markedly with increasing pH. Colloids were stabilized not only by electrostatic but also by steric repulsion. Organic colloids seem to dominate at low pH of the KOH-treatment; at pH > 4 mineral particles were also dispersed. Even though the presence of the Ca 2þ ion reduced the concentrations of colloidal Pb more than did the K þ ion, our results of the Ca(OH) 2 treatment show that the relevance of both colloidal and dissolved Pb increases at a pH of about 5.8. Risk assessment on limed sites should therefore take into account both dissolved and colloidal Pb in judging the likelihood of Pb leaching.