Benchmarking biochar with activated carbon for immobilizing leachable PAH and heterocyclic PAH in contaminated soils

Remediation of residually contaminated soils remains a widespread problem. Biochar can immobilize polycyclic aromatic hydrocarbons (PAH). However, studies on its ability to immobilize PAH and N, S, and O substituted PAH (hetero-PAH) in real soils, and benchmarking with commercial activated carbon are missing. Here, we compared the ability of pristine biochar (BC), steam-activated biochar (SABC), and commercial activated carbon (AC) to immobilize PAH and hetero-PAH. The three carbons were tested on soils from four different contami-nated sites in Austria. Different amendment rates (w/w) of the carbons were investigated (BC: 1.0, 2.5, and 5%; SABC: 0.5, 1.0, and 2.0%; AC: 1%) in batch experiments to cover meaningful ranges in relation to their per-formance. SABC performed better than AC, removing at least 80% PAH with the lowest application rate of 0.5%, and achieving a complete removal at an application rate of 1.0%. BC performed slightly worse but still acceptable in residually contaminated soils (40 and 100% removal at 1 and 5% amendment, respectively). The ability of BC and SABC to immobilize PAH decreased as the PAH-molar volume increased. PAH with three or more rings were preferentially removed by AC compared to SABC or BC. This can be explained by the difference in pore size distribution of the carbons which could limit the accessibility of PAH and hetero-PAH to reach sorption sites for pi-pi electron donor-acceptor interactions, which drive PAH and hetero-PAH sorption to carbons. Column percolation tests confirmed the results obtained in batch tests, indicating, that decisions for soil remediation can be derived from simpler batch experiments. In soil samples with 1% BC, a reduction of over 90% in the total concentration of PAH in the leached water was observed. Overall, BC and SABC were demonstrated to be valid substitutes for AC for stabilizing residually contaminated soils

Plastics can be used more sustainably in agriculture

Plastics have become an integral component in agricultural production as mulch films, nets, storage bins and in many other applications, but their widespread use has led to the accumulation of large quantities in soils. Rational use and reduction, collection, reuse, and innovative recycling are key measures to curb plastic pollution from agriculture. Plastics that cannot be collected after use must be biodegradable in an environmentally benign manner. Harmful plastic additives must be replaced with safer alternatives to reduce toxicity burdens and included in the ongoing negotiations surrounding the United Nations Plastics Treaty. Although full substitution of plastics is currently not possible without increasing the overall environmental footprint and jeopardizing food security, alternatives with smaller environmental impacts should be used and endorsed within a clear socio-economic framework. Better monitoring and reporting, technical innovation, education and training, and social and economic incentives are imperative to promote more sustainable use of plastics in agriculture

Training the next generation of plastics pollution researchers: tools, skills and career perspectives in an interdisciplinary and transdisciplinary field

Plastics pollution research attracts scientists from diverse disciplines. Many Early Career Researchers (ECRs) are drawn to this field to investigate and subsequently mitigate the negative impacts of plastics. Solving the multi-faceted plastic problem will always require breakthroughs across all levels of science disciplinarity, which supports interdisciplinary discoveries and underpins transdisciplinary solutions. In this context, ECRs have the opportunity to work across scientific discipline boundaries and connect with different stakeholders, including industry, policymakers and the public. To fully realize their potential, ECRs need to develop strong communication and project management skills to be able to effectively interface with academic peers and non-academic stakeholders. At the end of their formal education, many ECRs will choose to leave academia and pursue a career in private industry, government, research institutes or non-governmental organizations (NGOs). Here we give perspectives on how ECRs can develop the skills to tackle the challenges and opportunities of this transdisciplinary research field and how these skills can be transferred to different working sectors. We also explore how advisors can support an ECRs’ growth through inclusive leadership and coaching. We further consider the roles each party may play in developing ECRs into mature scientists by helping them build a strong foundation, while also critically assessing problems in an interdisciplinary and transdisciplinary context. We hope these concepts can be useful in fostering the development of the next generation of plastics pollution researchers so they can address this global challenge more effectively

Are We Speaking the Same Language? Recommendations for a Definition and Categorization Framework for Plastic Debris

Embargo until 04 Jan 2020The accumulation of plastic litter in natural environments is a global issue. Concerns over potential negative impacts on the economy, wildlife, and human health provide strong incentives for improving the sustainable use of plastics. Despite the many voices raised on the issue, we lack a consensus on how to define and categorize plastic debris. This is evident for microplastics, where inconsistent size classes are used and where the materials to be included are under debate. While this is inherent in an emerging research field, an ambiguous terminology results in confusion and miscommunication that may compromise progress in research and mitigation measures. Therefore, we need to be explicit on what exactly we consider plastic debris. Thus, we critically discuss the advantages and disadvantages of a unified terminology, propose a definition and categorization framework, and highlight areas of uncertainty. Going beyond size classes, our framework includes physicochemical properties (polymer composition, solid state, solubility) as defining criteria and size, shape, color, and origin as classifiers for categorization. Acknowledging the rapid evolution of our knowledge on plastic pollution, our framework will promote consensus building within the scientific and regulatory community based on a solid scientific foundation.acceptedVersio

Sorption nicht-ionischer organischer Verbindungen an kohlenstoff-basierten Nanomaterialien – Systematische Charakterisierung, Modellierung und Anwendung

The interaction (i.e., sorption) of hydrophobic organic compounds (HOC) and carbon-based nanomaterials (CNM) has already been studied to some extent; however, a fundamental and systematic understanding of the relevant sorption mechanisms is yet missing. As a result of their increasing application, CNM will inevitably be released to the environment. Consequently, the interaction of HOC and CNM is of major importance for example for the environmental risk assessment on how CNM may influence the fate and transport of HOC. A qualitative and quantitative understanding of the interactions between HOC and CNM is thus of crucial importance. To this end, this thesis aims at a comprehensive and systematic investigation of sorption of carefully selected sorbates as molecular probe compounds by various CNM. The influence of environmentally relevant parameters such as irradiation, redox conditions, or the presence of natural organic matter (NOM) on sorption by CNM was investigated. Both the presence of oxygen and irradiation significantly changed surface properties of aqueous dispersed fullerenes (nC60) and consequently reduced the sorption affinity and capacity of nC60 for polycyclic aromatic hydrocarbons. Furthermore, the presence of NOM was shown to result in a reduction of sorption affinity and non-linearity by multi-walled carbon nanotubes (MWCNTs). Nevertheless, the use of n- and cycloalkanes as molecular probes showed that a potential change in sorption mode from adsorption by MWCNTs to absorption into NOM-coated MWCNTs did not occur. Overall, the studied parameters indicated a decreased sorption by CNM after a release of these sorbents into the environment. Sorption isotherms of a diverse set of molecular probes covering compounds of various polarities were determined to develop a poly-parameter linear free-energy relationship (ppLFER) for sorption by MWCNTs. This approach gave useful insights into the relevant interactions and their contribution to overall sorption. The development of a ppLFER allowed a significantly improved prediction of distribution coefficients between water and MWCNTs compared to commonly used predictions based on a correlation of sorption by MWCNTs with hydrophobicity parameters of sorbates, such as the octanol-water partitioning coefficient. Finally, MWCNTs were explored for their potential application in solventless in-tube microextraction for the preconcentration of BTEX compounds from aqueous samples. For method development, a design of experiments was used for a systematic investigation of relevant extraction parameters and their interactions. The results of method validation emphasized the strong interaction of MWCNTs with BTEX and the promising potential of the sorbent in analytical chemistry compared to currently available sorbent material. In addition, the method was successfully applied to various real samples. This thesis demonstrates that systematic approaches in combination with selected probe sorbates present useful insights into the molecular interaction of CNM with non-ionic organic compounds.Die Wechselwirkung (Sorption) von hydrophoben organischen Verbindungen (HOC) und kohlenstoffbasierenden Nanomaterialien (CNM) wurde bereits in gewissem Umfang untersucht. Ein grundlegendes und systematisches Verständnis der relevanten Sorptionsmechanismen fehlt aber bisher. Zudem wird als Folge ihrer zunehmenden Anwendung ein Eintrag von CNM in die Umwelt unweigerlich wahrscheinlicher. Folglich ist die Wechselwirkung von HOC und CNM auch unter umweltrelevanten Aspekten von großer Bedeutung: zum Beispiel zur Risikoabschätzung, ob CNM in der Umwelt den Verbleib und Transport von HOC beeinflussen. Ein qualitatives und quantitatives Verständnis der Wechselwirkungen zwischen HOC und CNM ist dafür von entscheidender Bedeutung. Zu diesem Zweck war das Ziel dieser Arbeit eine umfassende und systematische Untersuchung der Sorption von ausgewählten Sorbaten als molekulare Sonden an verschiedenen CNM. Der Einfluss umweltrelevanter Parameter, wie Redox-Bedingungen, die Bestrahlung mit Licht und das Vorhandensein von natürlichem organischem Material (NOM), auf die Sorption an CNM wurde untersucht. Durch Anwesenheit von Sauerstoff und Bestrahlung änderten sich die Oberflächeneigenschaften von wässrig dispergiertem Fulleren (nC60) erheblich. Folglich reduzierte sich die Sorptionsaffinität und –kapazität polyzyklischer aromatischer Kohlenwasserstoffe an nC60. Zudem führte die Anwesenheit von NOM zu einer Reduzierung der Sorptionsaffinität und –nichtlinearität an mehrwandigen Kohlenstoffnanoröhren (MWCNTs). Hingegen zeigte die Verwendung von n- und Cycloalkanen als molekulare Sonden keine Änderung des Sorptionsmodus von Adsorption an die Oberfläche von MWCNTs zu Absorption in NOM-beschichtete MWCNTs. Insgesamt lassen die Ergebnisse der untersuchten Parameter auf eine verringerte Sorption an in die Umwelt eingetragenen CNM schließen. Sorptionsisothermen wurden für eine Vielzahl diverser Molekularsonden unterschiedlicher Polarität experimentell bestimmt, um die Sorption an MWCNTs mittels poly-parameter linearer freie-Energie Beziehungen zu beschreiben. Dieser Ansatz gab nützliche Einblicke in die relevanten Wechselwirkungen und deren Beitrag zur Gesamtsorption. Die Entwicklung einer ppLFER erlaubte eine deutlich verbesserte Vorhersage der Verteilungskoeffizienten im Vergleich zu gängigen Vorhersagemodellen mittels einer Korrelation der Sorption an MWCNTs und Hydrophobizitätsparametern, wie der Oktanol-Wasser Verteilungskonstanten. Schließlich wurden MWCNTs hinsichtlich einer möglichen Anwendung als gepackte Phasen in der lösemittelfreien In-tube Mikroextraktion zur Anreicherung von BTEX aus wässrigen Proben untersucht. Zur Methodenentwicklung wurde eine statistische Versuchsplanung verwendet, die eine systematische Untersuchung der relevanten Extraktionsparameter und deren potentieller Wechselwirkung erlaubte. Die Ergebnisse der Methodenvalidierung betonten die starke Wechselwirkung von MWCNTs und BTEX und damit das vielversprechende Potential von CNM als Sorbentmaterial in der analytischen Chemie im Vergleich zu derzeit verfügbaren Extraktionsphasen. Zudem wurde das Verfahren erfolgreich an verschiedenen Realproben angewandt. Die vorliegende Arbeit zeigt, dass systematische Verfahren in Kombination mit ausgewählten Sorbatsonden, wertvolle Einblicke in die molekularen Wechselwirkungen von CNM mit nicht-ionischen organischen Verbindungen bieten

Data on sorption of organic compounds by aged polystyrene microplastic particles

This article contains data on experimental sorption isotherms of 21 probe sorbates by aged polystyrene microplastics. The polymeric particles were subjected to an UV-induced photo-oxidation procedure using hydrogen peroxide in a custom-made aging chamber. Sorption data were obtained for aged particles. The experimental sorption data was modelled using both single- and poly-parameter linear free-energy relationships. For discussion and interpretation of the presented data, refer to the research article entitled “Sorption of organic compounds by aged polystyrene microplastic particles” (Hüffer et al., 2018) [1]

Solving Familiar Problems: Leveraging Environmental Testing Methods for Nanomaterials to Evaluate Microplastics and Nanoplastics

The potential environmental and human health risks from microplastic (1 µm to 1 mm) and nanoplastic (<1 µm) particles (MNPs) is receiving increasing attention from scientists and the public [...