Metal transfer to sediments, invertebrates and fish following waterborne exposure to silver nitrate or silver sulfide nanoparticles in an indoor stream mesocosm

Engineered nanomaterials; Silver uptake; TroutNanomaterials dissenyats; Captació de plata; TruitaNanomateriales de ingeniería; Absorción de plata; TruchaThe fate of engineered nanomaterials in ecosystems is unclear. An aquatic stream mesocosm explored the fate and bioaccumulation of silver sulfide nanoparticles (Ag2S NPs) compared to silver nitrate (AgNO3). The aims were to determine the total Ag in water, sediment and biota, and to evaluate the bioavailable fractions of silver in the sediment using a serial extraction method. The total Ag in the water column from a nominal daily dose of 10 μg L−1 of Ag for the AgNO3 or Ag2S NP treatments reached a plateau of around 13 and 12 μg L−1, respectively, by the end of the study. Similarly, the sediment of both Ag-treatments reached ~380 μg Ag kg−1, and with most of it being acid-extractable/labile. The biota accumulated 4–59 μg Ag g−1 dw, depending on the type of Ag-treatment and organism. The oligochaete worm, Lumbriculus variegatus, accumulated Ag from the Ag2S exposure over time, which was similar to the AgNO3 treatment by the end of the experiment. The planarian, Girardia tigrina, and the chironomid larva, Chironomus riparius, showed much higher Ag concentrations than the oligochaete worms; and with a clearer time-dependent statistically significant Ag accumulation relative to the untreated controls. For the pulmonate snail, Physa acuta, bioaccumulation of Ag from AgNO3 and Ag2S NP exposures was observed, but was lower from the nano treatment. The AgNO3 exposure caused appreciable Ag accumulation in the water flea, Daphnia magna, but accumulation was higher in the Ag2S NP treatment (reaching 59 μg g−1 dw). In the rainbow trout, Oncorhynchus mykiss, AgNO3, but not Ag2S NPs, caused total Ag concentrations to increase in the tissues. Overall, the study showed transfer of total Ag from the water column to the sediment, and Ag bioaccumulation in the biota, with Ag from Ag2S NP exposure generally being less bioavailable than that from AgNO3.This work was supported by the project NanoFASE (Nanomaterial Fate and Speciation in the Environment), financed by the European Union's Horizon 2020 research and innovation programme under grant agreement no 646002. RDH was partly supported by NanoHarmony under grant agreement 885931 in Horizon 2020 while redrafting the main text. PVS was awarded with a PhD grant (SFRH/BD/51571/2014) by FCT – Fundação para a Ciência e a Tecnologia. SL and PVS received additional financial support from FCT/MCTES, through national funds, to CESAM (UIDP/50017/2020+UIDB/50017/2020+ LA/P/0094/2020)

Metal transfer to sediments, invertebrates and fish following waterborne exposure to silver nitrate or silver sulfide nanoparticles in an indoor stream mesocosm

The fate of engineered nanomaterials in ecosystems is unclear. An aquatic stream mesocosm explored the fate and bioaccumulation of silver sulfide nanoparticles (AgS NPs) compared to silver nitrate (AgNO). The aims were to determine the total Ag in water, sediment and biota, and to evaluate the bioavailable fractions of silver in the sediment using a serial extraction method. The total Ag in the water column from a nominal daily dose of 10 μg L of Ag for the AgNO or AgS NP treatments reached a plateau of around 13 and 12 μg L, respectively, by the end of the study. Similarly, the sediment of both Ag-treatments reached ~380 μg Ag kg, and with most of it being acid-extractable/labile. The biota accumulated 4–59 μg Ag g dw, depending on the type of Ag-treatment and organism. The oligochaete worm, Lumbriculus variegatus, accumulated Ag from the AgS exposure over time, which was similar to the AgNO treatment by the end of the experiment. The planarian, Girardia tigrina, and the chironomid larva, Chironomus riparius, showed much higher Ag concentrations than the oligochaete worms; and with a clearer time-dependent statistically significant Ag accumulation relative to the untreated controls. For the pulmonate snail, Physa acuta, bioaccumulation of Ag from AgNO and AgS NP exposures was observed, but was lower from the nano treatment. The AgNO exposure caused appreciable Ag accumulation in the water flea, Daphnia magna, but accumulation was higher in the AgS NP treatment (reaching 59 μg g dw). In the rainbow trout, Oncorhynchus mykiss, AgNO, but not AgS NPs, caused total Ag concentrations to increase in the tissues. Overall, the study showed transfer of total Ag from the water column to the sediment, and Ag bioaccumulation in the biota, with Ag from AgS NP exposure generally being less bioavailable than that from AgNO.This work was supported by the project NanoFASE (Nanomaterial Fate and Speciation in the Environment), financed by the European Union's Horizon 2020 research and innovation programme under grant agreement no 646002. RDH was partly supported by NanoHarmony under grant agreement 885931 in Horizon 2020 while redrafting the main text. PVS was awarded with a PhD grant (SFRH/BD/51571/2014) by FCT – Fundação para a Ciência e a Tecnologia. SL and PVS received additional financial support from FCT/MCTES, through national funds, to CESAM (UIDP/50017/2020+UIDB/50017/2020+ LA/P/0094/2020)

Transformation of nanoparticles inside the gut lumen of terrestrial isopod in vitro

V dosedanjih prehranjevalnih poskusih z enakonožcem Porcellio scaber so na podlagi primerjave kopičenja kovin v prebavni žlezi in količino prvotno dosegljivih kovinskih ionov sklepali, da se nanodelci (ND) v prebavnem traktu dodatno raztapljajo. V magistrski nalogi smo zato želeli ugotoviti, kako se spremeni raztapljanje nanodelcev zlata (Au), bakrovega oksida (CuO) in srebra (Ag) v simuliranem prebavnem soku enakonožca. Predvidevali smo, da organske komponente simuliranega prebavnega soka, proteini BSA (goveji serumski albumin), surfaktanti SDS (natrijev dodecilsulfat) in iztrebki (vir mikroorganizmov in organske snovi) vplivajo na raztapljanje ND. Rezultate in vitro poskusov smo primerjali z rezultati prehranjevalnih poskusov, kjer smo spremljali kopičenje kovin v prebavni žlezi. Au ND se v prebavnem soku niso raztapljali, kar je v skladu s predpostavko o njihovi inertnosti. V nasprotju z našimi pričakovanji prisotnost BSA in SDS ni povečala raztapljanja CuO- in Ag ND. Iztrebki niso dodatno vplivali na raztapljanje Ag ND, kar smo dokazali z uporabo metode sp-ICP-MS. Rezultati in vivo in in vitro poskusov so bili primerljivi le v primeru Au ND. S tehniko sp-ICP-MS smo dokazali, da se Au ND ne kopičijo v žlezi. V in vivo poskusu z Ag ND smo dobili lažno pozitivne rezultate o kopičenju Ag ND v žlezi. Predlagamo nadaljnje raziskave z Ag- in CuO ND, uporabo drugih komercialnih proteinov in surfaktantov, uporabo bolj napredne metode sp-ICP-MS in optimizacijo protokola za razklop vzorcev.Recent in vivo studies using isopod Porcellio scaber have proposed that metal nanoparticles (NPs) dissolve in the gut lumen which results in increased bioassimilation of metals in hepatopancreas in comparison to actually bioavailable free metal ions offered in food. In this thesis we wanted to examine the dissolution of gold (Au), copper oxide (CuO) and silver (Ag) NPs in simulated isopod gastric juice. We hypothesized, that organic compounds in simulated gastric juice, BSA protein (bovine serum albumin), SDS surfactant (sodium dodecly sulfate) and feces (source of microorganisms and organic matter), contribute to increased dissolution of NPs. We also compared the results of in vitro studies to results of in vivo studies where we assesed the assimilation of metals inside the gland. Gold NPs did not dissolve in the gastric juice which is in line with expectations. Contrary to our expectations, BSA and SDS did not influence the dissolution of CuO- and Ag NPs. Also feces did not affect the dissoluiton of Ag NPs. The latter was proved with use of sp-ICP-MS method. The results of in vivo studies were comparable to those of in vitro with Au NPs only. With sp-ICP-MS, we proved that Au NPs do not accumulate in hepatopancreas. The results of in vivo experiment with Ag NPs showed false positive results of Ag NPs accumulating in the gland. We suggest further research on Ag- and CuO NPs and use of other commercial proteins and surfactants. Also use of advanced methods, such as sp-ICP-MS and optimisation of the protocol of digestion of the samples is suggested

Toxicokinetics of Ag from Ag2S NP exposure in Tenebrio molitor and Porcellio scaber : Comparing single-species tests to indoor mesocosm experiments

Determining the potential for accumulation of Ag from Ag2S NPs as an environmentally relevant form of AgNPs in different terrestrial organisms is an essential component of a realistic risk assessment of AgNP emissions to soils. The objectives of this study were first to determine the uptake kinetics of Ag in mealworms (Tenebrio molitor) and woodlice (Porcellio scaber) exposed to Ag2S NPs in a mesocosm test, and second, to check if the obtained toxicokinetics could be predicted by single-species bioaccumulation tests. In the mesocosms, mealworms and woodlice were exposed together with plants and earthworms in soil columns spiked with 10 μg Ag g−1 dry soil as Ag2S NPs or AgNO3. The total Ag concentrations in the biota were measured after 7, 14, and 28 days of exposure. A one-compartment model was used to calculate the Ag uptake and elimination rate constants. Ag from Ag2S NPs appeared to be taken up by the mealworms with significantly different uptake rate constants in the mesocosm compared to single-species tests (K1 = 0.056 and 1.66 g dry soil g−1 dry body weight day−1, respectively), and a significant difference was found for the Ag bioaccumulation factor (BAFk = 0.79 and 0.15 g dry soil g−1 dry body weight, respectively). Woodlice did not accumulate Ag from Ag2S NPs in both tests, but uptake from AgNO3 was significantly slower in mesocosm than in single-species tests (K1 = 0.037 and 0.26 g dry soil g−1 dry body weight day−1, respectively). Our results are of high significance because they show that single-species tests may not be a good predictor for the Ag uptake in mealworms and woodlice in exposure systems having greater levels of biological complexity. Nevertheless, single-species tests could be used as a fast screening approach to assess the potential of a substance to accumulate in biota before more complex tests are conducted

Toxicokinetics of Ag from Ag2S NP exposure in Tenebrio molitor and Porcellio scaber: Comparing single-species tests to indoor mesocosm experiments

Determining the potential for accumulation of Ag from Ag2S NPs as an environmentally relevant form of AgNPs in different terrestrial organisms is an essential component of a realistic risk assessment of AgNP emissions to soils. The objectives of this study were first to determine the uptake kinetics of Ag in mealworms (Tenebrio molitor) and woodlice (Porcellio scaber) exposed to Ag2S NPs in a mesocosm test, and second, to check if the obtained toxicokinetics could be predicted by single-species bioaccumulation tests. In the mesocosms, mealworms and woodlice were exposed together with plants and earthworms in soil columns spiked with 10 μg Ag g−1 dry soil as Ag2S NPs or AgNO3. The total Ag concentrations in the biota were measured after 7, 14, and 28 days of exposure. A one-compartment model was used to calculate the Ag uptake and elimination rate constants. Ag from Ag2S NPs appeared to be taken up by the mealworms with significantly different uptake rate constants in the mesocosm compared to single-species tests (K1 = 0.056 and 1.66 g dry soil g−1 dry body weight day−1, respectively), and a significant difference was found for the Ag bioaccumulation factor (BAFk = 0.79 and 0.15 g dry soil g−1 dry body weight, respectively). Woodlice did not accumulate Ag from Ag2S NPs in both tests, but uptake from AgNO3 was significantly slower in mesocosm than in single-species tests (K1 = 0.037 and 0.26 g dry soil g−1 dry body weight day−1, respectively). Our results are of high significance because they show that single-species tests may not be a good predictor for the Ag uptake in mealworms and woodlice in exposure systems having greater levels of biological complexity. Nevertheless, single-species tests could be used as a fast screening approach to assess the potential of a substance to accumulate in biota before more complex tests are conducted

Toxicokinetics and bioaccumulation of silver sulfide nanoparticles in benthic invertebrates in an indoor stream mesocosm

Mesocosms allow the simulation of environmentally relevant conditions and can be used to establish more realistic scenarios of organism exposure to nanoparticles. An indoor mesocosm experiment simulating an aquatic stream ecosystem was conducted to assess the toxicokinetics and bioaccumulation of silver sulfide nanoparticles (Ag2S NPs) and AgNO3 in the freshwater invertebrates Girardia tigrina, Physa acuta and Chironomus riparius, and determine if previous single-species tests can predict bioaccumulation in the mesocosm. Water was daily spiked at 10 μg Ag L−1. Ag concentrations in water and sediment reached values of 13.4 μg Ag L−1 and 0.30 μg Ag g−1 in the Ag2S NP exposure, and 12.8 μg Ag L−1 and 0.20 μg Ag g−1 in the AgNO3. Silver was bioaccumulated by the species from both treatments, but with approximately 1.5, 3 and 11 times higher body Ag concentrations in AgNO3 compared to Ag2S NP exposures in snails, chironomids and planarians, respectively. In the Ag2S NP exposures, the observed uptake was probably of the particulate form. This demonstrates that this more environmentally relevant Ag nanoform may be bioavailable for uptake by benthic organisms. Interspecies interactions likely occurred, namely predation (planarians fed on chironomids and snails), which somehow influenced Ag uptake/bioaccumulation, possibly by altering organisms´ foraging behaviour. Higher Ag uptake rate constants were determined for AgNO3 (0.64, 80.4 and 1.12 Lwater g−1organism day−1) than for Ag2S NPs (0.05, 2.65 and 0.32 Lwater g−1organism day−1) for planarians, snails and chironomids, respectively. Biomagnification under environmentally realistic exposure seemed to be low, although it was likely to occur in the food chain P. acuta to G. tigrina exposed to AgNO3. Single-species tests generally could not reliably predict Ag bioaccumulation in the more complex mesocosm scenario. This study provides methodologies/data to better understand exposure, toxicokinetics and bioaccumulation of Ag in complex systems, reinforcing the need to use mesocosm studies to improve the risk assessment of environmental contaminants, specifically NPs, in aquatic environments