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The potential release of hazardous substances from polymer-based products is currently in the focus of environmental policy. Environmental simulations are applied to expose such products to selected aging conditions and to investigate release processes. Commonly applied aging exposure types such as solar and UV radiation in combination with water contact, corrosive gases, and soil contact as well as expected general effects on polymers and additional ingredients of polymer-based products are described. The release of substances is based on mass-transfer processes to the material surfaces. Experimental approaches to investigate transport processes that are caused by water contact are presented. For tailoring the tests, relevant aging exposure types and release quantification methods must be combined appropriately. Several studies on the release of hazardous substances such as metals, polyaromatic hydrocarbons, flame retardants, antioxidants, and carbon nanotubes from polymers are summarized exemplarily. Differences between natural and artificial exposure tests are discussed and demonstrated for the release of flame retardants from several polymers and for biocides from paints. Requirements and limitations to apply results from short-term artificial environmental exposure tests to predict long-term environmental behavior of polymers are presented.
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.
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.
The environmental compatibility of reactive fire-retardant coatings (intumescent paints) was investigated by a combination of leaching and ecotoxicological tests. Three representative fire-retardant coating systems were tested using two leaching procedures: “Horizontal Dynamic Surface Leaching Test” (DSLT) and the “Intermittent Immersion Test” (IIT). All eluate fractions (8 for DSLT and 9 for IIT) were analyzed for pH, conductivity, concentration of total organic carbon and selected anions und cations. Additionally, a GC-MS screening of selected fractions was conducted for identification of organic compounds. Eluate fractions 1 + 2 and fraction 7 of the DSLT were analyzed in four ecotoxicological tests (algae, daphnia, fish egg, luminescent bacteria) and in one genotoxicity test (umu). Concentration of most analytes was rather low or below limit of detection for many eluates. Analytes detected in eluates of all three products are Zn, Ba, SO4(2−) and PO4(3−). Release patterns do not indicate a general trend: some compounds show maximum release in the first fractions while for others the maximum was observed in later test stages. Ecotoxic effects in eluates were found, which were higher in the eluate fraction 7 (maximum lowest ineffective dilution for luminescent bacteria (LIDL) 256) than in the eluate fraction 1 + 2 (maximum LIDL = 24). The sensitivity of the test systems was very different with highest effects for luminescent bacteria, followed by algae and daphnia and without effects in the fish egg test and umu test. A biotest battery for the comprehensive assessment is therefore advisable.
The release of hazardous compounds from construction products can harm human health and the environment. To improve the sustainability of construction materials, the leaching of substances from construction products and their potential environmental impact should be assessed. Twenty-seven construction products from different product groups were examined with a combination of standardized leaching tests (dynamic surface leaching test and percolation test) and biotests (algae, daphnia, fish egg, luminescent bacteria, umu and Ames fluctuation tests). To identify the released substances, extensive qualitative and quantitative chemical analyses were performed, including gas chromatographic and liquid chromatographic screening techniques.
Results: Many of the tested eluates caused signifcant ecotoxic efects. Particularly high ecotoxicities were observed for grouts (lowest ineffective dilution (LID) up to 16384) and cork granules (LID up to 24578). The results of ecotoxicity tests allow the prioritization of the eluates that should be subjected to detailed chemical analyses. Organic screening by different methods and ranking the identifed substances based on recorded hazard classification is a suitable approach to identify the relevant toxic substances.
Conclusions: Determining the ecotoxicity of eluates from construction products records the summary effect of all leachable substances. This instrument is especially useful for construction products of complex and largely unknown composition. The ecotoxicological and the chemical–analytical approach complement each other in an ideal way to characterize the potential hazard of eluates from construction products and to identify the environmentally hazardous components in these eluates. Our results confirm that the proposed harmonized methods for testing eluate toxicity are an adequate and applicable procedure to move toward a more sustainable way of building and to reduce toxic effects of construction products in their use phase in the environment.
Tools for the characterization of secondary raw materials - status of leaching test application
(2018)
Leaching tests are used as tools for the assessment of environmental compatibility of granular waste materials with potential for reuse. The presentation gives an overview on available leaching tests, their field of application and relation to legislation. Furthermore robustness testing to elaborate optimized test conditions as well as performance characteristics from validation studies by BAM are addressed.
Tools for the characterization of secondary raw materials - status of leaching test application
(2018)
Leaching tests are used as tools for the assessment of environmental compatibility of granular waste materials with potential for reuse. The presentation gives an overview on available leaching tests, their field of application and relation to legislation. Furthermore robustness testing to elaborate optimized test conditions as well as performance characteristics from validation studies by BAM are addressed.
Potential use of incineration bottom ash in construction – Evaluation of the environmental impact
(2020)
Knowledge of the long-term leaching behavior of potentially harmful substances is crucial for the assessment of the environmental compatibility of reusing municipal solid-waste incineration bottom ash (MSWI BA) in construction, i.e., as a road base layer.
BA fractions obtained from wet-processing aiming at the improvement of environmental quality were used to investigate the mobility of relevant substances. Eluates from laboratory-scaled leaching procedures (column percolation and lysimeters) were analyzed to learn about the long-term release of substances. Unsaturated conditions and artificial rainwater (AR) were used in the lysimeter tests to simulate field conditions. In addition, batch test eluates were generated at usual liquid-to-solid ratios (L/S) for compliance testing purposes. A variety of cations and anions was measured in the eluates.
The wet treatment reduces the leaching of chloride and particularly sulfate by more than 60%. The release of typical contaminants for the treated MSWI BA such as the heavy metals Cu and Cr was well below 1% in the conducted leaching tests.
An increase in the Sb concentration observed in the lysimeter experiments starting at L/S 0.75 L/kg and in the column experiment at L/S 4 L/kg is assumed to be related to decreasing concentrations of Ca and thus to the dissolution of sparingly soluble calcium antimonate. The same leaching mechanism applies with V, but the concentration levels observed are less critical regarding relevant limit values. However, on the long term the behavior of Sb could be problematic for the application of MSWI BA in construction.
In Denmark, increasing amounts of woody biomass are being used for the production of renewable energy, resulting in more wood ashes being generated. While these materials have been mainly landfilled, wood ashes may also be utilised for fertilizing and liming purposes on top of soils. Pre-treatments involving hardening or granulation may be carried out prior to soil application. In this study, two Danish wood ash samples were hardened and/or granulated. Lab-hardening induced rapid changes in the shape of the acid neutralisation capacity curve of the ashes. Up-flow column tests, assuming local equilibrium conditions, were employed to investigate the leaching from pre-treated ashes. Granules and loose ashes demonstrated similar leaching behaviours, indicating that similar geochemical processes were governing their leaching. In comparison with untreated fresh ashes, the hardened ashes demonstrated reduced leaching of Ca, Ba, Pb and Zn with concentration levels generally below or close to the analytical limits of quantification; to the contrary, the leaching of As, P, Sb, Si, V and Mg was enhanced in the hardened ashes. The release of alkalinity was reduced by hardening. In general, all granules were barely breakable by finger-pinching and they could withstand one month of continuous leaching, preserving their overall shape. The solubility of phosphorous in neutral ammonium citrate indicated that about 30–51% of the total P content in the ash samples was released, suggesting that the ashes could be potentially valuable as P-fertiliser if applied onto soil.