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Graphene-related materials (GRMs) are used in many innovative applications thanks to their unique physicochemical properties. The increasing development of GRMs-containing products and the resulting future widespread availability could lead to the unintended release of GRMs with unknown consequences for the environment.According to REACH, all new substances manufactured or imported in the EU must undergo a battery of ecotoxicological bioassays [OECD Test Guidelines (TG)] to assess their potential risk to aquatic organisms. However, these tests were developed to assess the toxicity of water-soluble substances, whereas GRMs are not. GRMs dispersed in aqueous media tend to aggregate and settle, changing their bioavailability over time. Therefore, this work aims to assess the applicability of TG201 to GRMs by studying the GRMs Dispersions Stability (GDS) in the TG201 medium. GDS was evaluated by examining the sedimentation and aggregation of GRMs by Turbiscan and flowcytometry (FCM) analyses, respectively, over the 72 hours test period. The following factors affecting GDS were tested: (i) particle composition and (ii) concentration, (iii) turbulence, and (iv) medium composition. The effects of (i)–(iii) were tested using dispersions of few-layer graphene (FLG), graphene oxide (GO), and reduced GO (rGO) at 4–20 mg L−1, that were or were not subjected to various methods to maintain turbulence (bubbling, shaking, and stirring). The effect of (iv) was tested by comparing GDS in distilled water, 5 commercial mineral waters with different ionic contents, and TG201 medium eventually added with dispersants [Suwannee River Natural Organic Matter (SRNOM), carboxymethylcellulose (CMC), and sodium deoxycholate (SDC)]. In addition, GRMs dispersions were used to evaluate the algal growth inhibition, i.e. the TG201 endpoint. Turbiscan analyses revealed that FLG had the fastest sedimentation rate in the first 3 hours, while GO was the most stable, independent of (ii). Visual inspections and FCM revealed that magnetic stirring increased GDS the most. However, turbulence always increased the formation of loose, stable, and more complex aggregates. Similarly, GRMs dispersions in high ionic content media had a greater increase in GRMs particles with high complexity over the 72 hours than in those with low content, e.g. the TG201 medium. In contrast, the addition of SRNOM to the TG201 medium increased the GDS of all dispersions. Our results show that GRMs dispersions are not stable under the standard TG201 conditions and therefore do not meet the TG requirement of a stable and homogeneous dispersion throughout the test. Therefore, modifications of the test protocols to improve the applicability of TG201 to GRMs, such as the use of SRNOM, will be presented. Finally, these data on GDS will help predict the GRMs behaviour during ecotoxicological testing, an important factor for the correct interpretation of TG201 results, and the fate of GRMs in freshwater environments.

Although small bags containing living or dead moss or lichens are widely used to monitor persistent atmospheric pollutants in urban and industrial environments, uptake mechanisms and the reliability of this approach have been scarcely investigated. Shoots of the moss Hypnum cupressiforme Hedw. and lobes of the lichen Pseudevernia furfuracea (L.) Zopf from unpolluted areas were pre-treated by: 1) water washing (WL, WM); 2), oven drying at 120 °C for 24 h (OL, OM); 3) HNO3 washing (AL, AM); 4) NH4-oxalate extraction at 85 °C for 15 h (OLoxa, OMoxa, ALoxa, AMoxa). Four bags with 500 mg of each material were exposed for six weeks in Trieste and Naples (Italy) on the roof of automatic devices for continuous recording of NOx, SO2, CO, PM10, and climatic data. Two synthetic materials (A: quartz fibre filter Whatman QMA 1851047; B: cation-exchange filter Pall ICE 450) were exposed in the same conditions to compare uptake processes and accumulation capacity with bio-materials. 15 elements were analysed before and after exposure. CO2 gaseous exchange, chlorophyll fluorescence, chlorophyll content, and K, Ca and Mg intra- and extra-cellular distribution assessed in WL and WM. Results demonstrate that WM vitality was drastically reduced after the exposure in both sites, whereas WL vitality was mostly unmodified as shown by increased C and N content at levels reflecting CO and NOx pollution. Average concentrations (µg g-1 dry wt) of trace metals increased significantly in all materials and were scarcely influenced by the vitality or type of pre-treatment, although concentrations were always higher in moss shoots than in lichen lobes. For a reliable comparison between synthetic and biological materials, the specific surface area was estimated and concentrations expressed as ng cm-2. This resulted in similar concentrations in moss shoots and lichen lobes but significantly lower concentrations in synthetic materials. Passive capture of airborne particulate matter accounted for most of the metal uptake.

Biomonitoring of air pollutants by moss and lichen transplants has been widely used over the past years, especially to monitor trace elements, since it gives useful information on their deposition, particularly in those urban and industrial areas lacking of indigenous moss and lichen species. Moreover, this technique provides information on contaminants associated to airborne particles which in European urban areas are not routinely checked, hindering the identification of pollutant sources crucial to undertake effective policies to knock down air pollutants. Nevertheless, the current lack of standardization at international level, and the scarce knowledge on the factors influencing element uptake make this technique still open to criticism. In this experiment moss and lichen were exposed for 17 weeks at four urban air quality monitoring stations of Naples city. Trace element uptake was evaluated in moss material before and after different devitalisation treatments (acid washing, oven drying and the novel water boiling) and in lichen exposed with and without the nylon bag. A major uptake was overall recorded in moss materials. Uptake differences among moss materials were not significant (P = 0.378), as well as the difference between lichen exposed with and without nylon bag (P=0.532). The ordination of sites/materials in relation to element uptake indicates a contamination gradient of the investigated sites, but element profiles did not differentiate substantially in the different areas of the city suggesting that atmospheric deposition in Naples urban area is qualitatively homogeneous only differing quantitatively in diverse monitoring sites. The overall high and significant correlations observed among and between geogenic and antropogenic elements suggest that polluted urban soil could represent a massive source for most elements. The implementation of devitalized moss bag could represent a ready-to-use robust tool for routine monitoring of air pollutants.