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Influence of weathering on the leaching behaviour of zinc and PAH from synthetic sports surfaces
(2017)
Synthetic materials used for outdoor sports grounds consist of a mix of inorganic, organic and polymeric compounds that show ageing due to weathering and a complex leaching behaviour by percolation of rainwater, which can limit its lifetime. Additionally, weathering exposure induces degradation processes in the polymers, which leads to the formation of new surfaces allowing water to access additional reservoirs of leachable compounds. A laboratory test comprising artificial weathering, ozonisation and subsequent leaching was developed to investigate this behaviour in a reproducible and controllable way. The experiments showed a general decline of Zn, polycyclic aromatic hydrocarbons (PAH) and total organic carbon (TOC) concentrations after an initial increase. Within this general trend, the course of concentration over exposure duration is very specific for individual sample materials and the analyte under investigation. The results indicate that weathering and degradation behaviour cannot be predicted from initial material conditions. Thus, weathering experiments are recommended to fill this gap of knowledge.
Auslaugversuche wurden mit verschiedenen Bauprodukten durchgeführt, die unter Anwendungsbe-dingungen mit Niederschlägen in Kontakt kommen können. In das Testprogramm wurden Lacke für Außenanwendungen, Wärmedämmverbundsysteme, Dachziegel und polymere Dachfolien einbezogen.
Mit diesen Produkten wurden der von CEN TC 351 entwickelte dynamische Oberflächenauslaugtest (DSLT) und Immersionstests nach EN 16105 durchgeführt. Emissionsverläufe wurden sowohl für an-organische Komponenten als auch für organische Substanzen in den Eluaten ermittelt. Auslaugbare organische Substanzen wurden zuvor in Screeningtests identifiziert.
Um die mögliche Freisetzung von Stoffen aus Bauprodukten beurteilen zu können, ist es erforderlich, Emissionsverläufe zu beschreiben. Dazu sind die verwendeten Testverfahren geeignet. Um Baupro-dukte mit einem Blauen Engel als „Produkte mit geringer Auslaugung“ auszuloben, müssen die aus-laugbaren Substanzen komplett bekannt sein. Für organische Verbindungen ist das noch eine Heraus-forderung. Außerdem erfordert die Bewertung der Testergebnisse sowohl Übertragungsmodelle, die Vorhersagen über freisetzbare Stoffmengen unter Anwendungsbedingungen ermöglichen, als auch Vorgaben zu tolerierbaren Umweltkonzentrationen. Hier besteht noch Handlungsbedarf.
Column leaching tests are frequently used and accepted for investigation of release of hazardous substances from solid materials. Independent of differences due to the field of application or national regulations, column tests assume that local equilibrium is established in the experiment which facilitates transfer of results to field conditions. In the process of harmonization and standardization within Europe the question on the influence of flow rate and grain size distribution on the local equilibrium was raised. Thus, a set of experiments using two different masonry materials with varying grain size distribution and flow rate were conducted including stop/flow experiments. Results are compared to a numerical model which takes intraparticle pore diffusion-controlled release of Mo and V into the percolating water into account. Due to the relatively high intraparticle porosity of the materials (24–29%) data and model indicate that initially equilibrium-state conditions prevail followed by rapidly decreasing concentrations. The model fits data for Mo and V reasonably well; however, after the initial decline of concentrations (at L/S > 2) extended tailing is observed especially of elements occurring as oxides, which is not captured by the model.
Brominated flame retardants have widely been used for more than 50 years and have been frequently detected in environmental samples as surface water and fish. Leaching from construction products was identified as one possible source. The use of substances as e.g. hexabromocyclododecane (HBCCD) was restricted recently due to increasing concern about negative impacts on the environment and human health caused by the persistent, bio accumulative and toxic properties. New polymeric brominated flame retardants have been developed to replace HBCCD in expanded polystyrene (XPS), which is used for insulation of buildings. It is assumed that the release from the polymer is much smaller in comparison to release of small molecules as HBCCD. The release from the polymer may include monomers or small fragments of different size. Thus, a sum parameter is needed. According to Schlummer et al. it is possible to detect brominated molecules using X-ray fluorescence spectroscopy by determination of brome content in XPS extracts. As only small brominated compounds can be extracted it also allows for the differentiation between the two classes of compounds. This method was applied to verify the presence of different kinds of flame retardants in XPS samples and to evaluate the leaching behavior.
Leachiing tests - a useful tool for the environmental impact assessment of construction products?
(2018)
Construction products and waste materials used for construction can be in contact with the environment and may release potential harmful compounds. Information on the total content of these substances in the product is not sufficient to assess its envrionmental impact since it does not consider realistic exposure conditions.The impact of these compounds is often assessed by using the total content in the product. This estimation lacks realistic exposure conditions.
Concerning the pathway to soil and groundwater by contact with rain or seepage water leaching tests, which were developed and standardized by the European Committee for Standardization, are available. While for secondary construction products and waste this investigation of the leaching behaviour is standard procedure and is already part of regulation in Germany (draft ordinance on reuse of mineral waste) and within Europe (landfill directive) the release from primary construction products got in the focus more recently. Several monitoring studies found unexpected high concentrations of substances used as herbicides and fungicides in surface water and stormwater originating from urban areas. As some of these compounds are even banned for the use in agricultural applications in Europe alternative sources as roof materials and façade coatings exposed to rain were suggested. Further field and laboratory tests confirmed construction products as sources of these substances in water.
The aim of this presentation is to show exemplary results of existing leaching methods and underline the strength and weaknesses of the test system with selected examples from our work. We especially draw the attention to the research which is still needed to close the gap between the results of leaching experiments and the subsequent risk assessment of the products.
Construction products are complex materials and contain a large number of different chemicals, which might be released to the environment during usage. Depending on the compound and on the matrix only a small portion is transferred to environment and therefore a risk assessment should be based on the available portion. Concerning the pathway to soil and groundwater by contact with rain or seepage water leaching tests were developed and standardized by CEN to determine the release potential of construction products. Chemical analysis in the eluates can be combined with eco-toxicological testing. In this presentation an overview about existing leaching methods is given using selected examples of our work. We especially draw the attention to research which is still needed to close the gap between the results of leaching experiments and the subsequent risk assessment of the products.
The eluates of 15 paints for outdoor use were used for a screening of organic compounds and the concentration of cations and anions were determined. Concerning the inorganic constituents only a small number of elements were present with concentrations higher than the limit of detection. Thus, leaching of potential hazardous chemicals is probably of higher concern. Several glycol ethers, polyalkylene glycols and some surfactants and coalescing agents have been identified. Among these only the latter are classified as hazardous to aquatic organisms. The identification of the organic compounds is a time consuming and labor-intensive step due to the high number of chemicals produced and used. Using eco-toxicity tests provides information on the environmental risk without the need for of chemical identification of all compounds. The screening of a set of construction products shows that only a part of eluates causes adverse effects in the test and that such screening can be used as a first step in the assessment of construction products. If this kind of testing is included in the evaluation concept an in depth chemical analysis is only needed for products showing adverse effects.
Determination of the eluate concentration after leaching enables to determine the potential release to the environment and to focus on the available fraction. However, limit values or other concepts to use this information in risk assessment are still missing.
Cadmiumhaltige Pigmente werden in Künstlerfarben (z.B. Cadmiumgelb PY35) verwendet und können beim Reinigen gebrauchter Pinsel mit Wasser über das Abwasser in die Kläranlagen eingetragen werden, wo sie auf Grund ihrer geringen Wasserlöslichkeit im Klärschlamm verbleiben. Bei landwirtschaftlicher Nutzung des Klärschlamms, kann das Cadmium nach Aufnahme in Pflanzen in die menschliche Nahrungskette gelangen. Aufnahme von Cadmium erhöht die Wahrscheinlichkeit an Brustkrebs zu erkranken und führt durch eine Verringerung der Knochendichte zu einer erhöhten Anzahl an Knochenbrüchen. Daher wurde bei der europäischen Chemikalienbehörde ECHA ein Verbotsantrag nach Annex XV von einem Mitgliedsland gestellt.
Mengenmäßig ist der Betrag an Cadmium, der über diesen Expositionsweg auf Agrarflächen eingetragen werden klein: 120 kg im Vergleich zu 120 Tonnen aus anderen Quellen. Zur Abschätzung des Risikos ist allerdings nicht nur die Gesamtmenge entscheidend, sondern auch die Mobilität der Schadstoffe. Um diese zu untersuchen wurden mit Cadmiumpigmenten dotierte Klärschlämme mit Boden gemischt und das Auswaschverhalten mit Hilfe von Säulenperkolationstests untersucht. Das Cadmium liegt in den Pigmenten als Cadmiumsulfid vor, dessen Löslichkeit stark vom Redoxpotential abhängt und dem pH-Wert abhängt. Daher wurden die Versuche unter verschiedenen Redoxbedingungen und mit einem sauren Eluenten durchgeführt.
Eluate wurden über einen Zeitraum von 68 h gesammelt und der pH-Wert, die Leitfähigkeit, die Trübung, Konzentration an organischen Kohlenstoff (TOC) und Cd bestimmt. Das Redoxpotential sinkt nach Start der Elution schnell und hängt von dem Gehalt an Kohlenstoff im Boden ab: Je höher der Gehalt ist, um so langsamer sinkt das Redoxpotential. Einen eindeutigen Zusammenhang zwischen Cadmiumfreisetzung und Redoxpotential konnte aber nicht gefunden werden. Insgesamt wurden maximal 2 % des vorhandenen Cadmiums freigesetzt. Im Vergleich zu Versuchen mit nicht dotierten Böden, der selbst auch geringe Mengen an Cadmium enthielt, konnte keine erhöhte Freisetzung beobachtet werden. Daraus kann geschlossen werden, dass die Cadmiumpigmente im Boden nur in sehr geringen Maß verfügbar sind