Leonardo Pantoja Munoz

Consideration of the bioavailability of metal/metalloid species in freshwaters: experiences regarding the implementation of biotic ligand model-based approaches in risk assessment frameworks

After the scientific development of biotic ligand models (BLMs) in recent decades, these models are now considered suitable for implementation in regulatory risk assessment of metals in freshwater bodies. The BLM approach has been described in many peer-reviewed publications, and the original complex BLMs have been applied in prospective risk assessment reports for metals and metal compounds. BLMs are now also recommended as suitable concepts for the site-specific evaluation of monitoring data in the context of the European Water Framework Directive. However, the use is hampered by the data requirements for the original BLMs (about 10 water parameters). Recently, several user-friendly BLM-based bioavailability software tools for assessing the aquatic toxicity of relevant metals (mainly copper, nickel, and zinc) became available. These tools only need a basic set of commonly determined water parameters as input (i.e., pH, hardness, dissolved organic matter, and dissolved metal concentration). Such tools seem appropriate to foster the implementation of routine site-specific water quality assessments. This work aims to review the existing bioavailability-based regulatory approaches and the application of available BLM-based bioavailability tools for this purpose. Advantages and possible drawbacks of these tools (e.g., feasibility, boundaries of validity) are discussed, and recommendations for further implementation are given.

Enhanced determination of As–phytochelatin complexes in Chlorella vulgaris using focused sonication for extraction of water-soluble species

The most challenging areas in the analysis of As–GS/PC complexes are their extraction from small amounts of biological material and the maintenance of their stability during HPLC separation. Focused sonication was used to extract these complexes from Chlorella vulgaris and the integrity of such complexes was determined by HPLC online with simultaneous HR-ICP-MS and ES-MS/MS detection. Water soluble arsenic species were extracted with an improved 71.1% (SE 0.78) efficiency and much reduced extraction times (30 s) allowing the determination of unstable arsenic phytochelatin (PC) and glutathione (GS) species in small biomass making the method particularly well-suited for cell cultures. Here, it was found that C. vulgaris produces the following intact phytochelatins and homo-phytochelatins (with Ala and desGly instead of Gly) complexes when cells are exposed to As(III): As(III)–PC2, GS–As(III)–PC2, As(III)–(PC2)2, MMA(III)–PC2, As(III)–PC3, As(III)–PC4, As(III)–γ-(Glu–Cys)3–Ala, GS–As(III)–γ-(Glu–Cys)2–Ala, As(III)–γ-((Glu–Cys)2)2–Ala, MMA(III)–γ-(Glu–Cys)2–Ala, As(III)–γ-(Glu–Cys)2, GS–As(III)–γ-(Glu–Cys)2. When the alga was exposed to DMA, only DMASV–GS was found. In contrast, cells did not produce any complex when exposed to As(V). It is the first time that, as a result of the newly developed extraction method using sonication, such complexes have been identified in Chlorella vulgaris exposed to arsenic and their intact arsenic homo-phytochelatins have been reported in any organism.

Characterisation of “flushable” and “non-flushable” commercial wet wipes using microRaman, FTIR spectroscopy and fluorescence microscopy: to flush or not to flush

The introduction to the market of wet wipes, advertised and labelled as “flushable”, has been the subject of controversy due to their perceived potential to block sewer systems as observed with other non-woven cloths such as traditional non-flushable wipes. Non-woven cloths that enter wastewater systems can find their way into the aquatic environment via wastewater effluents and it has been suggested that the breakdown of these fabrics can release materials such as microplastics into the environment. Worldwide research has revealed the alarming number of aquatic organisms affected by the presence of plastic debris in the aquatic environment harbouring a potential risk to humans through the introduction of microplastics into the food chains. However, the actual material composition of flushable wipes, their fate and impacts in the aquatic environment have not yet been scientifically studied. This paper investigates the fibre composition of flushable and non-flushable wipes, specifically with regard to synthetic polymer material, using Fourier transform infrared (FTIR) and microRaman spectroscopy along with fluorescence microscopy. The study demonstrated the presence of polyester (polyethylene terephthalate, (PET)), high-density polyethylene (HDPE) and polyethylene/vinyl acetate (PEVA/EVA) in some flushable wipes and PET in all non-flushable. Other polymers such us polypropylene (PP), low-density polyethylene (LDPE), expanded polystyrene (EPS) and polyurethane (PU) were also identified as potential components in the flushable material. Hence, commercially available wet wipes labelled as flushable could also be considered as a possible source of microplastic fibres in the wastewater streams and, if not retained, in the environment.