Presence of metals and metalloids in crumb rubber used as infill of worldwide synthetic turf pitches: Exposure and risk assessment.

Crumb rubber derived from end-of-life tires (ELTs) is frequently used as infill of synthetic turf pitches, promoting circular economy. Although important to reduce the accumulation of waste, the use of recycled ELTs can be a problem to human health and the environment, both by direct contact during pitch use and by the release of these elements to the surroundings, mostly via volatilization and leaching. The present study aimed to evaluate the distribution of metals in ELT-derived crumb rubber collected in artificial turf worldwide and assess possible trends by country, pitch age and type (indoor vs. outdoor). The concentration ranges observed are very wide, especially in outdoor fields and for the most abundant metals, namely Zn (2989-5246 mg/kg), Fe (196-5194 mg/kg), Mg (188-1795 mg/kg) and Al (159-1882 mg/kg). For Zn, the levels were mostly above the safe limits set in European directives for relatable matrices (soils and toy materials), and the same happened for Pb, a much more toxic metal at lower concentrations. A multi-pathway human exposure study was also performed, and the risk assessment shows non-carcinogenic and carcinogenic risks from accidental crumb rubber ingestion (with Cr and Pb as major contributors) above the acceptable values for all the receptors except adult bystanders, with a higher significance to younger individuals. These results bring a different perspective regarding most of the studies reporting low risks related with exposure to metals in crumb rubber.

Rethinking water treatment targets: Bacteria regrowth under unprovable conditions.

Ozonation is among the currently used technologies to remove chemical and biological contaminants from secondary treated urban wastewater (UWW). Despite its effectiveness on the abatement of organic micropollutants (OMPs) and disinfection, previous studies have shown that regrow of bacteria may occur upon storage of the ozonated UWW. This reactivation has been attributed to the high content of assimilable organic carbon after treatment. In order to investigate if ozonation by-products are the main biological regrowth drivers in stored ozonated UWW, the ozonation surviving cells were resuspended in sterile bottled mineral water (MW), simulating a pristine oligotrophic environment. After 7 days storage, organisms such as Acinetobacter, Methylobacterium, Cupriavidus, Massilia, Acidovorax and Pseudomonas were dominant in both ozonated UWW and pristine MW, demonstrating that bacterial regrowth is not strictly related to the eventual presence of ozonation by-products, but instead with the ability of the surviving cells to cope with nutrient-poor environments. The resistome of UWW before and after ozonation was analysed by metagenomic techniques. Draft metagenome assembled genomes (dMAGs), recovered from both ozonated UWW and after cell resuspension in MW, harboured genes conferring resistance to diverse antibiotics classes. Some of these antibiotic resistance genes (ARGs) were located in the vicinity of mobile genetic elements, suggesting their potential to be mobilized. Among these, dMAGs affiliated to taxa with high relative abundance in stored water, such as P. aeruginosa and Acinetobacter spp., harboured ARGs conferring resistance to 12 and 4 families of antibiotics, respectively, including those encoding carbapenem hydrolysing oxacillinases. The results herein obtained point out that the design and development of new wastewater treatment technologies should include measures to attenuate the imbalance of the bacterial communities promoted by storage of the final treated wastewater, even when applying processes with high mineralization rates.

Comparison between UVA- and zero-valent iron-activated persulfate processes for degrading propylparaben.

Conventional wastewater treatments are not efficient in removing parabens, which may thus end up in surface waters, posing a threat to aquatic biota and human health. As an alternative treatment, persulfate (PS)-driven advanced oxidation technologies have gained growing attention for removing these pollutants. In this study, the degradation of propylparaben (PrP) by UVA- and zero-valent iron (ZVI)-activated persulfate was investigated. The effects of initial PS concentration ([PS]0) and irradiance or ZVI concentration were explored using the Doehlert experimental design. For the UVA-activated system, the specific PrP degradation rate (k) and percent removal were consistently higher for increasing [PS]0 and irradiance, varying in the ranges 0.0053-0.0192 min-1 and 37.9-77.3%, respectively. In contrast, extremely fast PrP degradation was achieved through the ZVI/PS process (0.3304 < k < 0.9212 min-1), with removal percentages above 97.5%; in this case, paraben degradation was hindered for a ZVI dosage beyond 40 mg L-1. Regarding toxicity, ECOSAR predictions suggest that the degradation products elucidated by LC-MS/MS are less toxic than PrP toward fish, daphnid, and green algae. In addition, both processes showed to be strongly dependent on the water matrix, being ZVI/PS more impacted for a MBR effluent, although its performance was much better than that exhibited by the UVA-driven process (t1/2 of 65.4 and 276.1 min, respectively).

Anoxic degradation of chlorpyrifos by zerovalent monometallic and bimetallic particles in solution.

The degradation of highly toxic and persistent chlorinated organic compounds by zerovalent metals (ZVMs) has received considerable attention for in situ groundwater remediation. Due to its abundance and low toxicity, iron has been mostly applied for such purposes, despite several limitations, such as rapid surface passivation and little efficacy towards certain contaminants. Given that, we evaluated monometallic zerovalent iron (ZVI), copper (ZVC) and zinc (ZVZ), and bimetallic copper-coated ZVI (ZVI/Cu) and ZVZ (ZVZ/Cu) for anoxic reductive degradation of chlorpyrifos (CP). Two approaches to enhance metal reactivity were investigated: the synthesis of bimetallic particles with copper and the comparison between micro and nanoparticles. All of the tested monometallic and bimetallic particles dechlorinated the target molecule, although complete chlorine removal was not achieved by any metal during the 30-d treatment period. Coating the zerovalent monometallic particles with copper enhanced reactivity. Reactivity was ZVC > ZVZ > ZVI for monometallic particles and ZVZ/Cu > ZVI/Cu for bimetallic microparticles. The analysis of the degradation products indicated the presence of dechlorinated compounds as well as 3,5,6-trichloro-2-pyridinol, a hydrolysis product.

Evaluation of amicarbazone toxicity removal through degradation processes based on hydroxyl and sulfate radicals.

The herbicide amicarbazone (AMZ), which appeared as a possible alternative to atrazine, presents moderate environmental persistence and is unlikely to be removed by conventional water treatment techniques. Advanced oxidation processes (AOPs) driven by •OH and/or SO4•- radicals are then promising alternatives to AMZ-contaminated waters remediation, even though, in some cases, they can originate more toxic degradation products than the parent-compound. Therefore, assessing treated solutions toxicity prior to disposal is of extreme importance. In this study, the toxicity of AMZ solutions, before and after treatment with different •OH-driven and SO4•--driven AOPs, was evaluated for five different microorganisms: Vibrio fischeri, Chlorella vulgaris, Tetrahymena thermophila, Escherichia coli, and Bacillus subtilis. In general, the toxic response of AMZ was greatly affected by the addition of reactants, especially when persulfate (PS) and/or Fe(III)-carboxylate complexes were added. The modifications of this response after treatment were correlated with AMZ intermediates, which were identified by mass spectrometry. Thus, low molecular weight by-products, resulting from fast degradation kinetics, were associated with increased toxicity to bacteria and trophic effects to microalgae. These observations were compared with toxicological predictions given by a Structure-Activity Relationships software, which revealed to be fairly compatible with our empirical findings.

Amicarbazone degradation promoted by ZVI-activated persulfate: study of relevant variables for practical application.

Alarming amounts of organic pollutants are being detected in waterbodies due to their ineffective removal by conventional treatment techniques, which warn of the urgent need of developing new technologies for their remediation. In this context, advanced oxidation processes (AOPs), especially those based on Fenton reactions, have proved to be suitable alternatives, due to their efficacy of removing persistent organic compounds. However, the use of ferrous iron in these processes has several operational constraints; to avoid this, an alternative iron source was here investigated: zero-valent-iron (ZVI). A Fenton-like process based on the activation of a recently explored oxidant-persulfate (PS)-with ZVI was applied to degrade an emerging contaminant: Amicarbazone (AMZ). The influence of ZVI size and source, PS/ZVI ratio, pH, UVA radiation, dissolved O2, and inorganic ions was evaluated in terms of AMZ removal efficiency. So far, this is the first time these parameters are simultaneously investigated, in the same study, to evaluate a ZVI-activated PS process. The radical mechanism was also explored and two radical scavengers were used to determine the identity of major active species taking part in the degradation of AMZ. The degradation efficiency was found to be strongly affected by the ZVI dosage, while positively affected by the PS concentration. The PS/ZVI system enabled AMZ degradation in a wide range of pH, although with a lower efficiency under slightly alkaline conditions. Dissolved O2 revealed to play an important role in reaction kinetics as well as the presence of inorganic ions. UVA radiation seems to improve the degradation kinetics only in the presence of extra O2 content. Radicals quenching experiments indicated that both sulfate (SO4•-) and hydroxyl (•OH) radicals contributed to the overall oxidation performance, but SO4•- was the dominant oxidative species.

Role of Fe(III)-carboxylates in AMZ photodegradation: A response surface study based on a Doehlert experimental design.

Photochemical redox reactions of Fe(III) complexes in surface waters are important sources of radical species, therefore contributing to the sunlight-driven elimination of waterborne recalcitrant contaminants. In this study, the effects of three Fe(III)-carboxylates (i.e., oxalate, citrate, and tartrate) on the UVA photoinduced oxidation of the herbicide amicarbazone (AMZ) were investigated. A Doehlert experimental design was applied to find the Fe(III):ligand ratios and pH that achieved the fastest AMZ degradation rate. The results indicated optimal ratios of 1:10 (Fe(III):oxalate), 1:4 (Fe(III):citrate), and 1:1 (Fe(III):tartrate), with the [Fe(III)]0 set at 0.1 mmol L-1 and the best pH found to be 3.5 for all the complexes. In addition, a statistical model that predicts the observed degradation rate constant (kobs) as a function of pH and Fe(III):carboxylate ratio was obtained for each complex, enabling AMZ-photodegradation predictions based on these two variables. To the best of our knowledge, this is the first time that such models are proposed. Not only the pH-dependent speciation of Fe(III) in solution but also the time profiles of photogenerated OH, Fe(II), and H2O2 gave appropriate support to the experimental results. Additional experiments using a sampled sewage treatment plant effluent suggest that the addition of aqua and/or Fe(III)-oxalate complexes to the matrix may also be effective for AMZ removal from natural waters in case their natural occurrence is not high enough to promote pollutant degradation. Therefore, the inclusion of Fe(III)-complexes in investigations dealing with the environmental fate of emerging pollutants in natural waterbodies is strongly recommended.