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Treated wood is frequently used for construction. However, there is a need to ensure that biocides used for the treatment are not a threat for people or environment. The paper focused on Pinus sylvestris treated with copper–boron–azole (CBA), containing tebuconazole as organic biocide and monoethanolamine (Mea).
This study investigates chemical mechanisms of fixation and mobilisation involved in the leaching process of the used inorganic and organic biocides in CBA.
A pH dependent leaching test was performed, followed by a set of complementary analysis methods in order to identify and quantify the species released from wood. The main findings of this study are:
-Organic compounds are released from untreated and treated wood; the quantity of released total organic carbon, carboxylic and phenolic functions increasing with the pH.
-Nitrogen containing compounds, i.e. mainly Mea and its reaction products with extractives, are released in important quantities from CBA treated wood, especially at low pH.
-The release of copper is the result of competitive reactions: fixation via complexation reactions and complexation with extractives in the liquid phase. The specific pH dependency of Cu leaching is explained by the competition of ligands for protonation and complexation.
-Tebuconazole is released to a lesser extent relative to its initial content. Its fixation on solid wood structure seems to be influenced by pH, suggesting interactions with –OH groups on wood. Boron release appears to be pH independent and very high. This confirms its weak fixation on wood and also no or weak interaction with the extractives.
Façade coatings are exposed to weathering. Driving rain events can cause façade runoff bearing the potential to release substances from the coating. In order to derive reliable and reproducible information about this so-called leaching (emission into water), a laboratory test method has been developed, that has been published as European Standard EN 16105:2011. An interlaboratory comparison has been performed with 8 participants in order to validate the test method. This article describes the test results that reveal statistics on the quality of the test method and allows further insights to the leaching mechanism in coatings.
Leaching of biocides from construction products is currently a research topic receiving attention from the European regulation authorities (CEN/TC 351).
In this paper we have focused on the leaching behaviour of CBA (copper-borateazoles) treated Pinus sylvestris.
To better define the chemistry of the leaching phenomena, two leaching tests (a static equilibrium test and a dynamic surface leaching test) have been carried out on untreated and treated wood, which offered more information about how the leaching of biocides interferes with other substances released from the wood structure.
Eluates, in liquid and lyophilised form, were further analyzed by analytical methods.
Organic (tebuconazole) and inorganic (Cu, B) biocides were quantified and several organic compounds have been identified (e.g.
carboxylic acids, phenols, amines, etc.).
Also, the total amount of phenols and of carboxylic groups was determined.
Results on inorganic compounds are in accordance with previous studies made on treated wood.
Furthermore, organic carbon, tebuconazole and other organic compounds' behaviour was extensively investigated.
This study aims to complete existing leaching data and to help developing a chemical model for several biocides in wood, including Cu, B and tebuconazole.
The content of chromium in different oxidation states in chromium-treated wood was studied with XANES (X-ray absorption near-edge structure) measurements at the Cr K absorption edge. It could be shown that wood samples treated with Cr(VI) (pine and beech) did still contain a measurable content of Cr(VI) after four weeks conditioning. If such wood samples were heat exposed for 2 h with 135 °C prior conditioning, Cr(VI) was no longer detected by XANES, indicating a complete reduction to chromium (III).
Facades are attacked by algae and fungi during weathering, impairing the surfaces visually and leading to long-term damage. To prevent this, appropriate biocides are used in facade coatings.
These can be washed out during weathering, especially when it rains. A standardized laboratory procedure to determine the amount of biocides released under practical conditions has been developed and is accessible as European Standard FprEN 16105.
Anwendungen von Bioziden in Materialien für Außenanwendungen sind mögliche Quellen für Biozide in Umweltkompartimenten infolge von witterungsbedingten Auswaschprozessen. Im Bericht werden Leachingprozesse und -parameter als auch Methoden zu deren Untersuchung unter Labor- und Freilandversuchsbedingungen beschrieben. Vorteile und Grenzen der verschiedenen Herangehensweisen zur Untersuchung von Leachingprozessen werden diskutiert. Standardisierte Auswaschtests sowie in der Fachliteratur publizierte Auswaschexperimente werden zusammenfassend dargestellt. Es wird beschrieben, wie Leachingdaten gemäß Technischem Leitfaden zur Biozidprodukten-Richtlinie 98/8/EG für eine Risikobewertung genutzt werden. Ein alternativer Ansatz zur mathematischen Modellierung von Leachingtest-Daten wurde erprobt und wird im Bericht erläutert. Potentiell lassen sich mit dem vorgeschlagenen Ansatz bestimmte gegenwärtig auftretende Schwierigkeiten bei der Risikobewertung umgehen.
Applications of biocides in outdoor materials are potential sources of biocides in environmental compartments due to leaching processes under weathering conditions. Leaching processes and parameters as well as methods to investigate leaching processes under laboratory and semi-field conditons are described in the report. Benefits and limitations of different test approaches are discussed. Standardised leaching tests as well as leaching experiments reported in scientific literature are listed. The application of leaching data for risk assessments according to the Technical Guidance Documents for the Biocidal Products Directive (98/8/EC) is described. An alternative approach for mathematical modelling of leaching data was tested and is Explained in the report. Certain difficulties that currently appear during risk assessments may be circumvented by the proposed approach.
The current European legislation requires that combined effects of the active substances and any substance of concern contained in biocidal products are taken into account in environmental risk assessment. The hypothesis whether the consideration of active substances together with all formulation additives that are labeled as presenting an environmental hazard is sufficient for a reliable environmental risk assessment was tested in the present study by investigating 3 wood preservative products. Relevant single substances in the products, some of their generic mixtures, the biocidal products themselves, and aqueous eluates prepared from the products (representing potential environmental mixtures) were tested for effects on algal growth and Daphnia acute immobilization as well as reproduction. Predictions for the products and the eluates were based on the concept of concentration addition and were mostly found to provide reliable or at least protective estimates for the observed acute and chronic toxicity of the mixtures. The mixture toxicity considerations also indicated that the toxicity of each product was dominated by just 1 of the components, and that assessments based only on the dominating substance would be similarly protective as a full-mixture risk assessment. Yet, there remained uncertainty in some cases that could be related to the toxicity of transformation products, the impact of unidentified formulation additives, or synergistic interaction between active substances and formulation additives.