Selenate and selenite uptake, accumulation and toxicity in Lemna minuta.

The kinetics of Se uptake and toxicity to Lemna were studied over a period of 14 days of exposure to Se(IV) or Se(VI). The growth of Lemna stopped immediately after exposure to 5.0 mg/L of Se(IV) or Se(VI). The content of chlorophyll and phaeopigments of Lemna exposed to 5.0 mg/L of Se(IV) was two to three times less than in the control after 3 d exposure. Lemna took up Se rapidly within the first 3 d. The Se content in Lemna along with the exposure time fitted well the two-compartment and the hyperbolic model, which demonstrates that the mechanism of Se(IV) and Se(VI) uptake in Lemna is not only through passive diffusion, but also through other processes such as ion channel proteins or transporters. The kinetic bioconcentration factors (BCFs) were 231 and 42 for 0.5 mg/L Se(IV) and Se(VI) exposure, respectively. The uptake rate of Lemna reached 263 mg/kg/d and 28 mg/kg/d in the Se(IV) and Se(VI) treatments, respectively. This study showed that Se(IV) has a faster accumulation rate than Se(VI), but a higher toxicity, indicating Lemna could be a good candidate to remove Se(IV) from water, producing Se-enriched biomass which may eventually also be considered for use as Se-enriched feed supplement or fertilizer.

Chironomidae bloodworms larvae as aquatic amphibian food.

Different species of chironomids larvae (Diptera: Chironomidae) so-called bloodworms are widely distributed in the sediments of all types of freshwater habitats and considered as an important food source for amphibians. In our study, three species of Chironomidae (Baeotendipes noctivagus, Benthalia dissidens, and Chironomus riparius) were identified in 23 samples of larvae from Belgium, Poland, Russia, and Ukraine provided by a distributor in Belgium. We evaluated the suitability of these samples as amphibian food based on four different aspects: the likelihood of amphibian pathogens spreading, risk of heavy metal accumulation in amphibians, nutritive value, and risk of spreading of zoonotic bacteria (Salmonella, Campylobacter, and ESBL producing Enterobacteriaceae). We found neither zoonotic bacteria nor the amphibian pathogens Ranavirus and Batrachochytrium dendrobatidis in these samples. Our data showed that among the five heavy metals tested (Hg, Cu, Cd, Pb, and Zn), the excess level of Pb in two samples and low content of Zn in four samples implicated potential risk of Pb accumulation and Zn inadequacy. Proximate nutritional analysis revealed that, chironomidae larvae are consistently high in protein but more variable in lipid content. Accordingly, variations in the lipid: protein ratio can affect the amount and pathway of energy supply to the amphibians. Our study indicated although environmentally-collected chironomids larvae may not be vectors of specific pathogens, they can be associated with nutritional imbalances and may also result in Pb bioaccumulation and Zn inadequacy in amphibians. Chironomidae larvae may thus not be recommended as single diet item for amphibians.

Foliar Selenate and Zinc Oxide Separately Applied to Two Pea Varieties: Effects on Growth Parameters and Accumulation of Minerals and Macronutrients in Seeds under Field Conditions.

Though selenium (Se) and zinc (Zn) constitute essential nutrients for human health, their deficiencies affect up to 15% and 17% of the global population, respectively. Agronomic biofortification of staple crops with Se/Zn may alleviate these challenges. Pea (Pisum sativum L.) is a nutritious legume crop that has great potential for Se/Zn biofortification. Herein, two varieties of pea (Ambassador, Premium) were biofortified via foliar application of sodium selenate (0/50/100 g of Se/ha) or zinc oxide (0/375/750 g of Zn/ha) during the flowering stage under field conditions. While no significant differences were found in Se accumulation between seed varieties upon Se treatments, selenate enhanced the accumulation of Se in the two seed varieties in a dose dependent manner. Selenium concentration was most elevated in seeds of Ambassador exposed to 100 g of Se/ha (3.93 mg/kg DW compared to the control (0.08 mg/kg DW), p < 0.001). 375 g of Zn/ha (35.7 mg/kg DW) and 750 g of Zn/ha (35.5 mg/kg DW) significantly and similarly enhanced Zn concentrations compared to the control (31.3 mg/kg DW) in Premium seeds, p < 0.001. Zinc oxide also improved accumulations of Fe, Cu, Mn, and Mg in Premium seeds. Se/Zn treatments did not significantly affect growth parameters and accumulations of soluble solids and protein in seeds. Positive and significant (p < 0.01) correlations were observed between Zn and Fe, Cu, Mn and Mg levels in Premium seeds, among others. Consuming 33 g/day of pea biofortified with Se at 50 g/ha and 266 g/day of pea biofortified with 375 g of Zn/ha could provide 100% of the RDA (55 µg) for Se and RDA (9.5 mg) for Zn in adults, respectively. These results are relevant for enhancing Se/Zn status in peas by foliar biofortification.

Selenium in selected samples of infant formulas and milk commercialized in Belgium and Brazil: Total content, speciation and estimated intake.

Total selenium (Se) and Se species concentrations were determined in 50 infant formulas and milk samples commercialized in Brazil and Belgium. Infant formula categories were starter, follow-up, specialized and plant-based (soy and rice), while milk samples included whole, skimmed, semi-skimmed and plant-based products. Total Se content was determined by Inductively Coupled Plasma Mass Spectrometry (ICP-MS), after microwave digestion. An enzymatic extraction method was applied to evaluate the Se species, mostly selenomethionine (SeMet), Se(IV) and Se(VI), through High Performance Liquid Chromatography coupled to ICP-MS (LC-ICP-MS). Starters and follow-up samples presented the highest total Se concentrations and values up to 30 µg/kg were observed in the reconstituted product. The lowest level (below the LOQ = 10 µg/kg) was verified in an anti-regurgitation specialized formula. The relative agreement between the measured total Se and the Se content declared on the label varied from 55 % to 317 %. Concentrations in infant formulas were not markedly different from concentrations in milk except for rice and oat milk samples that showed values below the LOQ. SeMet was the main species found in milks, while in infant formulas the species concentrations varied according to the product. The daily intake (DI) of Se via infant formula consumption was calculated and compared with the Adequate Intake (AI) value and the Dietary Reference Intake (DRI) established by the EFSA NDA Panel and ANVISA, respectively. Estimated maximum intakes of total Se obtained for reconstituted infant formula were 40.6 mg/day, corresponding to 400 % and 202 % of the DRI and AI, respectively.

HPLC-ICP-MS method development to monitor arsenic speciation changes by human gut microbiota.

Inorganic arsenic (iAs) has been classified as a type 1 carcinogen and has also been linked to several noncancerous health effects. Prior to 1995, the As(V) methylation pathway was generally considered to be a detoxification pathway, but cellular and animal studies involving MMA(III) (mono metyl arsonous acid) and DMA(III) (dimethyl arsinous acid) have indicated that their toxicities meet or exceed that of iAs, suggesting an activation process. In addition, thiolated arsenic metabolites were observed in urine after oral exposure of inorganic arsenic in some studies, for which the toxicological profile was not yet fully characterized in human cells. Studies have revealed that microorganisms from the gut environment are important contributors to arsenic speciation changes. This presystemic metabolism necessitates the development of protocols that enable the detection of not only inorganic arsenic species, but also pentavalent and trivalent methylated, thiolated arsenicals in a gastrointestinal environment. We aim to study the biotransformation of arsenic (As) using a Simulator of the Human Intestinal Microbial Ecosystem (SHIME). To be able to analyze the arsenicals resulting from biotransformation reactions occurring in this system, a method using liquid chromatography hyphenated to an inductively coupled plasma mass spectrometer (HPLC-ICP-MS) was developed. A Hamilton PRP-X100 anion exchange column was used. The method allowed separation, identification and quantification of As(III) (arsenite), As(V) (arsenate), DMA(V) (dimethylarsinicacid), MMA(V) (monomethylarsonicacid) and MMMTA (monomethylmonothioarsenate). Attempts to optimize the same method for also separating MMA(III) and DMA(III) did not succeed. These compounds could be successfully separated using a method based on the use of a Zorbax C18 column. The properties of the column, buffer strength, pH and polar nature of mobile phase were monitored and changed to optimize the developed methods. Linearity, sensitivity, precision, accuracy and resolution of both methods were checked. The combination of the two methods allowed successful quantification of arsenic species in suspensions sampled in vitro from the SHIME reactor or in vivo from the human colon and feces.

Selective leaching of copper and zinc from primary ores and secondary mineral residues using biogenic ammonia.

With the number of easily accessible ores depleting, alternate primary and secondary sources are required to meet the increasing demand of economically important metals. Whilst highly abundant, these materials are of lower grade with respect to traditional ores, thus highly selective and sustainable metal extraction technologies are needed to reduce processing costs. Here, we investigated the metal leaching potential of biogenic ammonia produced by a ureolytic strain of Lysinibacillus sphaericus on eight primary and secondary materials, comprised of mining and metallurgical residues, sludges and automotive shredder residues (ASR). For the majority of materials, moderate to high yields (30-70%) and very high selectivity (>97% against iron) of copper and zinc were obtained with 1 mol L-1 total ammonia. Optimal leaching was achieved and further refined for the ASR in a two-step indirect leaching system with biogenic ammonia. Copper leaching was the result of local corrosion and differences in leaching against the synthetic (NH4)2CO3 control could be accounted for by pH shifts from microbial metabolism, subsequently altering free NH3 required for coordination. These results provide important findings for future sustainable metal recovery technologies from secondary materials.

Arsenic release: Insights into appropriate disposal of arsenic-loaded algae precipitated from arsenic contaminated water.

Limited information is available on arsenic (As) release from As-loaded algae precipitated from As contaminated water and its subsequently appropriate disposal. In this study, selected M. aeruginosa as algal model, changes of As concentrations and its speciation were thus investigated in the in-situ treated algae water by optimal coagulation. Meanwhile, after ex-situ disposal, As release kinetics were also examined from its precipitated algae with living and heat-treated conditions. Results showed that in the in-situ treated water, total dissolved As slowly decreased for 6 days, but arsenite increased largely after 3 days partly caused by its reduction status. While being disposed ex-situ, As release from precipitated algae depended not only on intracellular As content but also on the living or heat-treated status of algae. Additionally, potential risks arised from As release in short-term duration (24 h) from both the precipitated algae at 1.0 µM As(V) pre-exposure with the living and heat-treated conditions due to their higher release. Furthermore, As release in long-term (6 d) duration from heat-treated algae at 10.0 µM As(V) pre-exposure also resulted in potential risks. Accordingly, this study offers insights into the appropriate methods at a proper time of disposing precipitated algae with As-contamination.

Gap analysis of nickel bioaccessibility and bioavailability in different food matrices and its impact on the nickel exposure assessment.

The metal nickel is well known to cause nickel allergy in sensitive humans by prolonged dermal contact to materials releasing (high) amounts of nickel. Oral nickel exposure via water and food intake is of potential concern. Nickel is essential to plants and animals and can be naturally found in food products or contamination may occur across the agro-food chain. This gap analysis is an evaluation of nickel as a potential food safety hazard causing a risk for human health. In the first step, the available data regarding the occurrence of nickel and its contamination in food and drinks have been collected through literature review. Subsequently, a discussion is held on the potential risks associated with this contamination. Elevated nickel concentrations were mostly found in plant-based foods, e.g. legumes and nuts in which nickel of natural origin is expected. However, it was observed that dedicated and systematic screening of foodstuffs for the presence of nickel is currently still lacking. In a next step, published studies on exposure of humans to nickel via foods and drinks were critically evaluated. Not including bioaccessibility and/or bioavailability of the metal may lead to an overestimation of the exposure of the body to nickel via food and drinks. This overestimation may be problematic when the measured nickel level in foods is high and bioaccessibility and/or bioavailability of nickel in these products is low. Therefore, this paper analyzes the outcomes of the existing dietary intake and bioaccessibility/bioavailability studies conducted for nickel. Besides, the available gaps in nickel bioaccessibility and/or bioavailability studies have been clarified in this paper. The reported bioaccessibility and bioavailability percentages for different food and drinks were found to vary between

Differences in Cd and Zn bioaccumulation for the flood-tolerant Salix cinerea rooting in seasonally flooded contaminated sediments.

Several authors suggest that a hydrological regime aiming at wetland creation is a potential management option that favours reducing bioavailability for metal-contaminated sites. The hydrological conditions on a site constitute one of the many factors that may affect the availability of potentially toxic trace metals for uptake by plants. Bioavailability of Cd, Mn and Zn on a contaminated dredged sediment landfill (DSL) with variable duration of submersion was evaluated by measuring metal concentrations in the wetland plant species Salix cinerea in field conditions. Longer submersion periods in the field caused lower Cd and Zn concentrations in the leaves in the first weeks of the growing season. Foliar Cd and Zn concentrations at the end of the growing season were highest on the initially flooded plot that emerged early in the growing season. Foliar Zn concentrations were also high at a sandy-textured oxic plot with low soil metal concentrations. Zn uptake in the leaves was markedly slower than Cd uptake for trees growing on soils with prolonged waterlogging during the growing season, pointing at a different availability. Zn availability was lowest when soil was submerged, but metal transfer from stems and twigs to leaves may mask the lower availability of Cd in submerged soils. Especially for Cd, a transfer effect from one growing season to the next season was observed: oxic conditions at the end of the previous growing season seem to determine at least partly the foliar concentrations for S. cinerea through this metal transfer mechanism. Duration of the submersion period is a key factor for bioavailability inasmuch as initially submerged soils emerging only in the second half of the growing season resulted in elevated Cd and Zn foliar concentrations at that time.

Gold and silver nanoparticle effects on ammonia-oxidizing bacteria cultures under ammoxidation.

Owing to their wide application in industry and manufacturing, understanding the environmental safety of gold (Au) and silver (Ag) nanoparticles entering aquatic environment is a global issue of concern. For this study, ammonia-oxidizing bacteria (AOB) enrichment cultures reproduced from surface sediments taken from the Jiulong River estuary wetlands (Fujian Province, China) were spiked with nano-Ag and nano-Au to determine their impact on ammoxidation and the mechanisms involved in the process. Results showed that nano-Ag significantly inhibited bacterial ammoxidation in aquatic environment, with the average ammoxidation rate decreasing with increasing nano-Ag concentration. The average ammoxidation rate was significantly correlated to the Shannon index, the Simpson index, and AOB abundance. This suggested that ammoxidation inhibition resulted primarily from AOB biodiversity and abundance reduction, caused by the antibacterial property of nano-Ag. However, AOB biodiversity and abundance as well as bacterial ammoxidation were not inhibited by nano-Au (with a maximum experimental concentration of 2 mg L(-1)). Moreover, an insignificant correlation was found between AOB biodiversity and abundance and the average ammoxidation rate under the nano-Au treatment. Given that ammoxidation is regarded as a rate-limiting procedure in nitrogen (N) circulation, nano-Ag would affect N cycling but nano-Au would not after entering aquatic environments. Identified nano-Ag and nano-Au impacts on ammonium nitrogen transformation could be generalized in aquatic environment according to their extensive representation in the phylogenetic tree.

Arsenic undergoes significant speciation changes upon incubation of contaminated rice with human colon micro biota.

Cellular and animal studies involving MMA(III) (monomethyl arsonous acid) and DMA(III) (dimethyl arsinous acid) have indicated that their toxicities meet or exceed that of iAs. Thiolated arsenic metabolites were observed in urine after oral exposure of inorganic arsenic in some studies. For these species, the toxicological profile was not yet fully characterized in human cells. Some studies revealed that trivalent organoarsenic species are well absorbed in the intestine compared to iAs. However, other studies also indicated that a significant amount of rice-bound As reaches the colon, which may be attributed to the fibre-rich nature of the rice. Studies have revealed that microorganisms from the gut environment are important contributors to arsenic speciation changes. We aimed to study how the gut microbial metabolism affects As in different rice matrices. This was done in vitro using colon suspension from the Simulator of the Human Intestinal Microbial Ecosystem (SHIME system). Significant amounts of MMA(III), DMA(III) and MMMTA(V) were formed due to microbial metabolic processes like methylation and thiolation. These results suggested that presystemic metabolism by human gut micro biota should not be neglected in risk assessment studies. In this context, also toxicity and absorption of thiolated species by mammalian cells should be further investigated.