Julia Farkas

Characterization of the effluent from a nanosilver producing washing machine

The increasing number of nanomaterial based consumer products raises concerns about their possible impact on the environment. This study provides an assessment of the effluent from a commercially available silver nanowashing machine. The washing machine released silver in its effluent at an average concentration of 11μgL(-1), as determined by inductive coupled mass spectrometry (ICP-MS). The presence of silver nanoparticles (AgNPs) was confirmed by single particle ICP-MS as well as ion selective electrode measurements and filtration techniques. Size measurements showed particles to be in the defined nanosize range, with an average size of 10nm measured with transmission electron microscopy (TEM) and 60-100nm determined with nanoparticle tracking analysis (NTA). The effluent was shown to have negative effects on a natural bacterial community as its abundance was clearly reduced when exposed to the nanowash water. If washing machines capable of producing AgNPs become a common feature of households in the future, wastewater will contain significant loadings of AgNPs which might be released into the environment.

Effects of silver and gold nanoparticles on rainbow trout (Oncorhynchus mykiss) hepatocytes.

The use of nanomaterials is rapidly increasing, while little is known about their possible ecotoxicological effects. This work investigates the toxic effects of silver (Ag) and gold (Au) nanoparticles on rainbow trout hepatocytes. In addition to toxicity assessment the particles were characterized by transmission electron microscopy (TEM) and nanoparticle tracking analysis (NTA). Hepatocyte primary cultures were exposed to Au and Ag nanoparticles, with and without dissolved organic carbon (DOC), as well as HAuCl(4) and AgNO(3) as ionic solutions at concentrations up to 17.4mg/L and 19mg/L, respectively. Ag and Au particles were within the small nanometer size range when dispersed in pure water. In media with higher ionic strength and DOC, particles tended to agglomerate. Cytotoxicity assessments showed that Ag nanoparticles caused a significant reduction in membrane integrity and cellular metabolic activity in a concentration-dependent manner. Au nanoparticles caused a threefold elevation of ROS levels, but no cytotoxicity occurred at concentrations tested. The addition of DOC did not alter the particles potency of cytotoxicity or ROS induction capacity. The current study shows that Ag and Au nanoparticles have adverse effects on rainbow trout hepatocytes at low mg/L concentrations.

Uptake and effects of manufactured silver nanoparticles in rainbow trout (Oncorhynchus mykiss) gill cells.

Nanoparticles are already widely used in technology, medicine and consumer products, but there are limited data on their effects on the aquatic environment. In this study the uptake and effect of citrate (AgNP(CIT)) and polyvinylpyrrolidone (AgNP(PVP)) coated manufactured silver nanoparticles, as well as AgNO(3) (Ag(+)) were tested using primary gill cells of rainbow trout (Oncorhynchus mykiss). Prior to use, the nanoparticles were characterized for size, surface charge and aggregation behavior. Gill cells were cultured either as monolayers on solid support, or as multilayers on a permeable support cell culturing system, enabling transport studies. The uptake of silver nanoparticles and Ag(+) after exposure to 10 mg L(-1) was determined with microscopical methods and inductively coupled plasma mass spectrometry (ICP-MS). Cytotoxicity, in terms of membrane integrity, as well as oxidative stress (depletion of reduced glutathione) was tested at silver concentrations ranging from 0.1 mg L(-1) to 10 mg L(-1). Results show that AgNP(CIT) nanoparticles are readily taken up into gill cell monolayers while uptake was less for AgNP(PVP). In contrast, it appears that the slightly smaller AgNP(PVP) were transported through cultured multilayers to a higher extent, with transport rates generally being in the ng cm(-2) range for 48 h exposures. Transport rates for all exposures were dependent on the epithelial tightness. Moderate cytotoxic effects were seen for all silver treatments. Levels of reduced glutathione were elevated in contrast to control groups, pointing on a possible overcompensation reaction. Taken together silver nanoparticles were taken up into cells and did cause silver transport over cultured epithelial layers with uptake and transport rates being different for the two nanoparticle species. All silver treatments had measurable effects on cell viability.

The impact of TiO2 nanoparticles on uptake and toxicity of benzo(a)pyrene in the blue mussel (Mytilus edulis).

Nanoparticles are emerging contaminants of concern. Knowledge on their environmental impacts is scarce, especially on their interactive effects with other contaminants. In this study we investigated effects of titanium dioxide nanoparticles (TiO2NP) on the blue mussel (Mytilus edulis) and determined their influence on the bioavailability and toxicity of benzo(a)pyrene (B(a)P), a carcinogenic polyaromatic hydrocarbon (PAH). Blue mussels were exposed to either TiO2NP (0.2 and 2.0 mg L(-1)) or B(a)P (20 μg L(-1)) and to the respective combinations of these two compounds. Aqueous contaminant concentrations, the uptake of Ti and B(a)P into mussel soft tissue, effects on oxidative stress and chromosomal damage were analyzed. The uncoated TiO2NP agglomerated rapidly in the seawater. The presence of TiO2NP significantly reduced the bioavailability of B(a)P, shown by lowered B(a)P concentrations in exposure tanks and in mussel tissue. The activities of antioxidant enzyme superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) were impacted by the various exposure regimes, indicating oxidative stress in the contaminant exposure groups. While SOD activity was increased only in the 0.2TiO2NP exposure group, CAT activity was enhanced in both combined exposure groups. The GPx activity was increased only in the groups exposed to the two single compounds. In hemocytes, increased chromosomal damage was detected in mussels exposed to the single compounds, which was further increased after exposure to the combination of compounds. In this study we show that the presence of TiO2NP in the exposure system reduced B(a)P uptake in blue mussels. However, since most biomarker responses did not decrease despite of the lower B(a)P uptake in combined exposures, the results suggest that TiO2NP can act as additional stressor, or potentially alters B(a)P toxicity by activation.

Impact of TiO2 nanoparticles on freshwater bacteria from three Swedish lakes

Due to the rapidly rising production and usage of nano-enabled products, aquatic environments are increasingly exposed to engineered nanoparticles (ENPs), causing concerns about their potential negative effects. In this study we assessed the effects of uncoated titanium dioxide nanoparticles (TiO2NPs) on the growth and activity of bacterial communities of three Swedish lakes featuring different chemical characteristics such as dissolved organic carbon (DOC) concentration, pH and elemental composition. TiO2NP exposure concentrations were 15, 100, and 1000 μg L(-1), and experiments were performed in situ under three light regimes: darkness, photosynthetically active radiation (PAR), and ambient sunlight including UV radiation (UVR). The nanoparticles were most stable in lake water with high DOC and low chemical element concentrations. At the highest exposure concentration (1000 μg L(-1) TiO2NP) the bacterial abundance was significantly reduced in all lake waters. In the medium and high DOC lake waters, exposure concentrations of 100 μg L(-1) TiO2NP caused significant reductions in bacterial abundance. The cell-specific bacterial activity was significantly enhanced at high TiO2NP exposure concentrations, indicating the loss of nanoparticle-sensitive bacteria and a subsequent increased activity by tolerant ones. No UV-induced phototoxic effect of TiO2NP was found in this study. We conclude that in freshwater lakes with high DOC and low chemical element concentrations, uncoated TiO2NPs show an enhanced stability and can significantly reduce bacterial abundance at relatively low exposure concentrations.

Effects of Dispersed Aggregates of Carbon and Titanium Dioxide Engineered Nanoparticles on Rainbow Trout Hepatocytes

The purpose of this study was to investigate the cytotoxicity and oxidative stress responses of selected engineered carbon and titanium dioxide (TiO2) nanomaterials to rainbow trout (Oncorhynchus mykiss) primary hepatocytes. The engineered nanomaterials tested were C60 fullerenes, multiwall nanotubes (MWNT), single-wall nanotubes (SWNT) (functionalized and nonfunctionalized), and TiO2 of 5 and 200 nm in size. Characterization of these materials showed that they were typically present in solution as agglomerates. The engineered nanoparticle agglomerates were cytotoxic at nominal concentrations of >3 mg/L, and certain MWNT and SWNT produced significant intracellular reactive oxygen species (ROS) production as well as cytotoxicity. Analyses of the MWNT responsible for ROS production and cytotoxicity for selected transition metals demonstrated the presence of residual cobalt (Co), which was not present in the nonreactive/non-bioactive MWNT. Cobalt alone was not able to induce the observed effects in hepatocyte cells; however, coexposure with MWNT resulted in an increase in cytotoxicity. Data suggest that trace metals often associated with commercial nanotubes are responsible for the observed biological effects. In addition, other mechanisms, such as the proposed facilitated transport (e.g., Trojan horse) type mechanism of uptake, may provoke an increased response compared to aqueous exposures of trace metals in the absence of carbon nanoparticles.

The binding of phenanthrene to engineered silver and gold nanoparticles.

The steadily rising production and use of engineered nanoparticles (ENP) leads to their entry into the aquatic environment. In addition to the various adverse effects that have been seen for different organisms, ENP are suspected to influence the transport, bioavailability and toxic properties of a range of environmental contaminants that may adsorb to their surface. In this study, the binding properties of the polycyclic aromatic hydrocarbon phenanthrene to stabilized silver and gold ENP were investigated using a novel mass balance based single-equilibrium approach. Only citrate coated gold ENP (AuNP(CIT)) were found to bind phenanthrene. No binding was observed for polyvinylpyrolidone coated silver ENP (AgNP(PVP)) nor citrate coated silver ENP (AgNP(CIT)) suggesting that the properties of the core material have a major influence on binding reactions. A binding coefficient K(b) was defined as the ratio between the concentration of phenanthrene associated to the AuNP(CIT) and that freely dissolved in the exposure medium. Temperature was not seen to significantly influence K(b) within an environmentally relevant range (4-25 °C). The presence of methanol significantly reduced or prevented the formation of the AuNP(CIT)-phenathrene complex. Results suggest that the binding is a low energy physio-sorption, likely associated to a partial displacement or specific arrangement of the citrate capping on the gold core.

Are fluorescence-based chlorophyll quantification methods suitable for algae toxicity assessment of carbon nanomaterials?

Abstract Using a multiwalled carbon nanotube (MWCNT) and graphene oxide (GO) as representative test materials, we evaluated the applicability of in vivo and in vitro chlorophyll-a (Chl-a) fluorescence quantification methods, which are used in standard algae ecotoxicity tests such as OECD 201 and ISO 8692. In vivo quantification of Chl-a from Raphidocelis subcapitata indicated a significant reduction in Chl-a fluorescence in the presence of MWCNTs due to shading, but a significant autofluorescence from GO caused an overestimation of Chl-a concentration. In vitro Chl-a quantification methods employing a modified acetone and an ethanol extraction protocol reduced the influence of shading and autofluorescence, but both resulted in a significant loss of fluorescence signal in the presence of 100 mgL−1 MWCNTs (99–100%) and GO (21–52%). Chl-a reduction was dose dependent for both tested carbon-based MNMs (CNMs), but effects were more pronounced for MWCNT, which caused a significant fluorescence reduction (16 ± 0.3%) already at 1 mgL−1. Further study of the CNM–algae–Chl-a interaction processes revealed that CNM can not only interact with live algae, but also efficiently adsorb extracted Chl-a. Our results showed that within 10 min, 95–100% of Chl-a extracted from two algae concentrations were adsorbed to MWCNT, while 35–60% of Chl-a was adsorbed to the GO. This study shows that Chl-a quantification by fluorescence determination is not a suitable method for ecotoxicity testing of CNM. However, a quick screening test for individual MNMs is recommended to determine whether Chl-a adsorption is a significant process prior to selection of a quantification method.

Differential bioaccumulation of potentially toxic elements in benthic and pelagic food chains in Lake Baikal.

Lake Baikal is located in eastern Siberia in the center of a vast mountain region. Even though the lake is regarded as a unique and pristine ecosystem, there are existing sources of anthropogenic pollution to the lake. In this study, the concentrations of the potentially toxic trace elements As, Cd, Pb, Hg, and Se were analyzed in water, plankton, invertebrates, and fish from riverine and pelagic influenced sites in Lake Baikal. Concentrations of Cd, Hg, Pb and Se in Lake Baikal water and biota were low, while concentrations of As were similar or slightly higher compared to in other freshwater ecosystems. The bioaccumulation potential of the trace elements in both the pelagic and the benthic ecosystems differed between the Selenga Shallows (riverine influence) and the Listvenichnyĭ Bay (pelagic influence). Despite the one order of magnitude higher water concentrations of Pb in the Selenga Shallows, Pb concentrations were significantly higher in both pelagic and benthic fish from the Listvenichnyĭ Bay. A similar trend was observed for Cd, Hg, and Se. The identified enhanced bioavailability of contaminants in the pelagic influenced Listvenichnyĭ Bay may be attributed to a lower abundance of natural ligands for contaminant complexation. Hg was found to biomagnify in both benthic and pelagic Baikal food chains, while As, Cd, and Pb were biodiluted. At both locations, Hg concentrations were around seven times higher in benthic than in pelagic fish, while pelagic fish had two times higher As concentrations compared to benthic fish. The calculated Se/Hg molar ratios revealed that, even though Lake Baikal is located in a Se-deficient region, Se is still present in excess over Hg and therefore the probability of Hg induced toxicity in the endemic fish species of Lake Baikal is assumed to be low.

Does Microbial Biodegradation of Water-Soluble Components of Oil Reduce the Toxicity to Early Life Stages of Fish?

Microbial degradation following oil spills results in metabolites from the original oil. Metabolites are expected to display lower bioaccumulation potential and acute toxicity to marine organisms due to microbial-facilitated incorporation of chemical functional groups and a general decrease in lipophilicity. The toxicity and characterization of metabolites are poorly studied. The purpose of the present work was to evaluate the toxicity of degraded (0-21 days) water-soluble oil components. Low-energy water accommodated fraction (LE-WAF) of a weathered crude oil was prepared with nutrient amended seawater at 5 °C, kept in the dark, and sampled at 0, 10, 14, and 21 days. Samples were extracted with dichloromethane and toxicity experiments were conducted with reconstituted extracts. Toxicity experiments were conducted for 4 days on developing cod ( Gadus morhua) embryos during a critical period of their heart development. After exposure, embryos were kept in clean seawater and observed until 5 days post hatch. Survival, hatching, morphometric aberrations, and cardiac function was studied. The expected decrease in sublethal toxicity during the biodegradation period was not found, indicating that metabolites formed during biodegradation likely contributed to larvae toxicity.