| 1. |
- Arvidsson, Rickard, 1984, et al.
(författare)
-
Environmental Impact of Titanium Dioxide Nanoparticles – Applying Life Cycle Thinking and Risk Assessment for Swedish Conditions
- 2008
-
Ingår i: 3rd International Conference on the Environmental Effects of Nanoparticles and Nanomaterials, Birmingham University, Birmingham, UK, September 15-16, 2008.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The risks of nanoparticles have been issued by several different groups, e.g. The Royal Society (2004) and Friends of the Earth (2006), and the concept nanotoxicology has been introduced to underline the distinctive toxicological features of nanoparticles (Oberdörster et al. 2005). Some nanoparticles, such as carbon nanotubes, have been outlined as hazardous and great caution has been suggested before introducing carbon nanotubes into the market (Poland et al. 2008). According to a risk assessment performed by Mueller and Nowack (2007), titanium dioxide nanoparticles had higher predicted environmental concentration compared with the predicted no effect concentration than both silver nanoparticles and carbon nanotubes, and further detailed studies regarding titanium dioxide nanoparticles were suggested. However, no sensitivity analysis was performed in Mueller and Nowack (2007), and a crude model was used to model environmental faith of the titanium dioxide nanoparticles. Our study applied substance flow analysis in order to facilitate a comprehensive environmental risk assessment of titanium dioxide nanoparticles (see e.g. Tsunemi and Wada (2008) and Fuster et al. (2002)). A detailed investigation of the production of titanium dioxide nanoparticles and their application in society was performed facilitating hazard identification according to Hansen et al. (2007). Emissions were calculated based on use assumptions and a modelling of the environmental faith of the titanium dioxide nanoparticles was attempted including the particle aggregation and interaction with natural organic substances that modify bioavailability. Predicted environmental concentrations were calculated and compared with predicted no effect concentrations according to several ecotoxicological studies and in order to assess the uncertainty a sensitivity analysis was performed for input parameters.
|
|
| 2. |
- Arvidsson, Rickard, 1984, et al.
(författare)
-
Fate modeling of titanium dioxide nanoparticles in the water compartment by colloid chemistry
- 2009
-
Ingår i: 1st International Conference on the Environmental Implications and Applications of Nanotechnology, June 9-11, 2009, Amherst, U.S.A..
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Titanium dioxide is one of the most produced nanoparticles according to the Project of Emerging Nanotechnologies (www.nanotechproject.org). According to Mueller and Nowack (2008) it is also the nanoparticle that has the largest environmental concentration in the Swiss water compartment, 16 µg/l according to their high estimate. Further, Boxall et al. (2007) estimate a titanium dioxide nanoparticle environmental concentration of 24.5 µg/l in the UK water compartment for a scenario that probably overestimates the current exposure levels. However, neither of these risk models take fate processes such as aggregation and sedimentation into account. Colloid chemistry deals with particles within the size range of 1 nm to 1 µm. Nanoparticles of a size between one nanometer and a few hundred nanometers are thus well within the colloid range. Theories of colloid chemistry suggest that sedimentation of nanoparticles depends mainly on the density and the viscosity of the water and the density and size of the particles. Sedimentation is shown not to be an important factor, since the sedimentation of particles smaller than ~300 nm is negligible. Aggregation is a more complex process which depends on factors such as temperature, salinity, ion valence, pH, point of zero charge, the Hamaker constant, particle size and particle concentration (Elimelech et al. 1995). These factors were estimated for a typical Swedish lake and calculations were performed in MATLAB. The aggregation is modeled by kinetics according to Smoluchowski (1917) but adjusted according to the DLVO theory (see Elimelech et al. 1995). Preliminary results show that aggregation can reduce the predicted environmental concentration significantly in a short time. It would take less than 4 minutes for the initial environmental concentrations predicted by both Mueller and Nowack (2008) and Boxall et al. (2007) to be reduced by 50%. After 24 hours, both predicted environmental concentrations would have fallen below 0.1 µg/l.
|
|
| 3. |
- Arvidsson, Rickard, 1984, et al.
(författare)
-
MODELLING ENVIRONMENTAL FATE OF TiO2 NANOPARTICLES IN WATER – IMPLICATIONS FOR EMPIRICAL VALIDATION STUDIES
- 2009
-
Ingår i: 4th International Conference on the Environmental Effects of Nanoparticles and Nanomaterials, 6-9 September, Vienna, Austria.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The potential environmental effects of nanoparticles (NPs) require interdisciplinary research to assess the risks. One part of a risk assessment concerns exposure, which builds on knowledge of the environmental fate. In this particular case the fate of TiO2 NPs in the water compartment was modelled by applying a second order kinetic rate equation and the DLVO theory. Assumptions were made regarding water parameters such as pH, salt concentration and temperature, as well as regarding particle properties such as Hamaker constant, primary particle size and point of zero charge. The effect of sedimentation was taken into account, but as one would expect the influence of sedimentation on such small particles is very small. The model was implemented in MATLAB®. Results indicate the importance of agglomeration as an important fate mechanism, and that pH andpoint of zero charge are important parameters with regards to agglomeration. Other parameters such as the Hamaker constant, salt concentration and temperature were shown not to have a significant effect, which is in goodcorrelation with empirical studies. Also, we would like to see our model validated by empirical studies. Important implications then are to include a continuous inflowof NPs in the experimental setup and to work at environmentally relevant water properties. For example is the effect of natural organic matter (NOM) on theagglomeration not modelled, despite that its significance has been pointed out in many studies. This is due to a weak link between mathematical expressions andempirical data for this particular part of the model. It is of importance that this linkage is strengthened both by theoretical and empirical studies on NOM aimingat producing mathematical expressions, and empirical data, that can assist fate modelling of NPs.
|
|
| 4. |
- Arvidsson, Rickard, 1984, et al.
(författare)
-
The fate of titanium dioxide nanoparticles in the water compartment
- 2009
-
Ingår i: SETAC Europe 19th Annual Meeting, 31 May-4 June, 2009, Göteborg, Sweden.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Environmental risk of nanoparticles has been assessed in several studies. Titanium dioxide has been identified as one of the potentially most problematic nanoparticles. It has been shown that a large amount of the titanium dioxide nanoparticles may end up in the water compartment. These risk assessments constitute first estimates and several fate mechanisms are not taken into account. In this study, we propose a risk model that includes the two fate mechanisms sedimentation and aggregation. The sedimentation rate of titanium dioxide nanoparticles is determined using simple laws of motion. Still water is assumed, which gives optimal conditions for sedimentation. It is shown that despite the optimal conditions for sedimentation, the sedimentation rates of particles with a diameter of 100 nm and 1000 nm are about 8 years and 1 month, respectively. One month can be regarded as a long time from a risk perspective, and thus sedimentation is shown not to be an important factor for the removal of titanium dioxide nanoparticles from the water compartment. However, preliminary results show that aggregation can reduce the predicted environmental concentration significantly in a short time. Hence, equilibrium concentrations could be several orders of magnitude lower than what has been indicated in earlier studies. The aggregation of titanium dioxide nanoparticles is modeled using Smoluchowski kinetics and the DLVO theory, which are commonly used in colloid chemistry. The aggregation is shown to depend mainly on the pH of the water compartment and the zero point charge of the particles.
|
|
| 5. |
- Ekestubbe, Annika, 1953, et al.
(författare)
-
Oral radiologi
- 2005
-
Bok (övrigt vetenskapligt/konstnärligt)
|
|
| 6. |
- Hassellöv, Ida-Maja, 1974, et al.
(författare)
-
Verification of a benthic boxcosm system with potential for extrapolating experimental results to the field
- 2007
-
Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981. ; 353:2, s. 265-278
-
Tidskriftsartikel (refereegranskat)abstract
- A marine mesocosm system (boxcosm system) was developed for ecological and/or ecotoxicological studies of sediment community function and structure. The system consists of continuous flow-through incubations of intact sediment samples, each with a surface area of 0.25 m2. The experimental setup enables repeated non-destructive measurements of benthic fluxes, such as of nutrients, oxygen and dissolved inorganic carbon, over the sediment–water interface. The benthic fluxes reflect the function of the sediment community, integrating over the chemical, biological and physical activities in the sediment. The suitability of the boxcosm system for controlled, highly ecologically relevant studies of intact sediment communities was evaluated in two experiments of six weeks and five months duration respectively, where the functional and structural development over time was compared to the development of the sampling site. The function of the sediment was measured as nutrient and oxygen fluxes, and the structural component consisted of microbial functional diversity and meio- and macrofauna composition. Differences between the boxcosm and the sampling site were detected especially in nitrate fluxes and meiofauna diversity and abundance, but all differences fell within seasonal and inter-annual variability at the sampling site. The cause of the differences could be referred to differences in oxygen availability, supply of organic matter particles, and recruitment of larvae. These factors can however be compensated for within the present setup. The study shows that the boxcosms are suitable tools for ecologically relevant studies generating comparable conditions to the natural environment.
|
|
| 7. |
- Sandén, Björn, 1968, et al.
(författare)
-
Nanoteknik i våra hem
- 2008
-
Ingår i: Miljöforskning. ; 2008:3, s. 24-25
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
|
|
| 8. |
- Söderfjell, Stefan, 1970-
(författare)
-
Musculoskeletal pain, memory, and aging : Cross-sectional and longitudinal findings
- 2005
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The general aim of the thesis was to investigate potential differences in memory performance between participants across the adult life span with and without self-reported musculoskeletal pain. Chronic musculoskeletal pain is a major health related problem in our society. A common complaint related to chronic pain is about cognitive difficulties in attention, memory, and decision making. A number of studies have demonstrated that people with pain also perform wors on tasks measuring, for example episodic memory, semantic memory, and working memory. The present thesis aimed at replying these findings, by using a non-clinical population based sample. the potential differences in memory performance between people with and without pain were examined across the adult life span, in order to disentangle potential pain by age interactions. This was made by using both cross-sectional and longitudinal data. Study I aimed at studying differences in episodic memory performance, semantic memory performance, and implicit memory performance, between people with and without musculoskeletal pain. Differences were found for all three memory systems, but disappeared after controlling for years of formal education. In Study II an extension of the first study was made, in which performance on a range of cognitive tests were analysed. General differences were demonstrated , but yet again, years of education together with depression ruled out the effects. The most robust effects were found for word comprehension and construction ability. Finally, Study III used 5- and 10 year follow up studies to examine change over time in cognitive performance as a function of pain. The main finding from this study was that semantic memory for the oldest is impaired over time as a function of pain. An additional analysis showed similar patterns, regardless of age, for construction ability.
|
|
