In the European Union, it is commonly accepted that requirements for construction works include proof that they will not have adverse effects on human health and the environment. Constructions impact local environments during service time mainly due to emissions of substances into environmental compartments, such as the release of dangerous substances into groundwater, marine waters, surface waters, or soil. Expected emissions need to be estimated for construction products that can be in contact with water during their service life.
These horizontal leaching tests, as they are called, are intended to be generally applied for construction products with only a few exceptions. Where no additional information on the eluent is given, all standardized leaching tests presented here use demineralized water. This test is known as the dynamic surface leaching test DSLT and intends to describe diffusion-controlled leaching processes. Test specimens are exposed to water at a defined ratio of water volume to exposed surface area under controlled laboratory conditions. The water is exchanged on a defined time schedule and analyzed for the target substances.
Emissions per surface area are calculated from the obtained substance concentrations in the eluates and can be related to the duration of exposure. Based on the resulting emission curves, the test results make it possible to determine whether leaching is controlled by diffusion or other processes such as washout effects at the beginning.
Diffusion-controlled processes are proportional to the square root of contact time and are indicated by the pattern of the eluate concentrations after the defined periods of water contact. The test results cannot be used directly to derive expected environmental concentrations. Concepts for transferring results obtained under laboratory exposure conditions to service-life conditions still need to be developed or refined [ 21 , 22 ].
This restriction applies especially to organic substances that can be transformed during service life or in water. However, the test indicates whether target substances can be leached from investigated construction products. It is also possible to compare the leachability of the target substances from different construction products. They included common use scenarios to calculate MRLs that meet concentrations of environmental standards for specified times without water exchange.
Columns are filled with granular construction materials and exposed to up-flow percolation. The eluted water is collected stepwise until certain liquid-to-solid ratios are reached and can be analyzed for the target substances. The test results are presented as a function of liquid-to-solid ratios and make it possible to distinguish between different leaching mechanisms.
It is important to notice that the release in the column percolation test is mass-related, while it is area-related in the DSLT. Until now, only a few studies using these two tests have been published: Construction products exposed to weathering conditions with wet and dry phases can also be tested in a tank test with intermittent contact with water immersion cycles in accordance with DIN EN , which was developed for paints and varnishes.
This approach has been applied, e. Laboratory leaching tests for biocidal products that are based either on constant or intermittent water contact, as well as semi-field tests, are listed in a guidance document of the European Chemicals Agency, ECHA. These tests also apply to biocidal products that are included in construction products [ 33 ]. However, it is helpful to limit the number of tests run to facilitate comparability between tested products on the market. It will be the task of CEN Technical Committees that are responsible for the different harmonized construction product standards to select the applicable leaching test and define substances that are to be investigated.
These results will be the basis for declaring the properties of construction products as part of CE marking for marketing within Europe. In addition, the leaching test conditions, especially water quality and the duration of water contact, do not necessarily reproduce service-life conditions.
For instance, Hartwich and Vollpracht [ 26 ] observed that the leaching of heavy metals from concrete can be considerably reduced by the presence of calcium in leaching water that originates from natural sources, as compared with deionized water. This is explained by a precipitated layer of calcium carbonate on concrete surfaces that was also observed under service-life conditions. In general, the use of deionized water often leads to an alteration of the concentration gradient between the sample and the eluent in comparison with the field situation and, subsequently, with a change in leaching behavior.
Deionized water has no buffering capacity and is prone to changes in pH value if products with high alkaline or acidic potential are investigated. The pH value is, therefore, an important parameter for the interpretation of leaching test results. The standardized test conditions of the harmonized leaching tests are, therefore, not to be considered a simulation of reality, but as a helpful convention that allows further modeling of the data. Another challenge is the interpretation of test results from leaching tests under constant water contact for construction products on structures above the ground.
These include roofs and facades, which are only occasionally exposed to water contact.
In the case of facades, it is also important to consider that these vertically oriented surfaces are exposed only to driving rain. It can be useful to apply a test procedure that is based on intermittent water contact such as EN [ 34 ], which was developed for paints and varnishes, depending on the properties and exposure conditions of the construction materials. Analyses of eluates from construction products offer an excellent chance to avoid undesirable impacts on the environment. However, their benefit is directly linked to the selection of the investigated target substances.
Substances that need to be controlled can be selected from this list based on knowledge of the general composition of construction products. Nevertheless, due to the large variety of materials used in construction, this list can cover only some of the substances that can have environmental impacts. This makes it possible not only to assess the release of selected compounds, but also to identify compounds of interest by non-targeted analysis and to assess the effects that leachates have on organisms.
Both approaches will be discussed in the following paragraphs. The published reports on studies dealing with the release of compounds from construction products and the monitoring of compounds in storm water usually analyze a limited number of analytes.
The release of biocides e. The robustness study performed for the leaching standards for construction products included inorganic analytes for a broad range of products and also considered the release of PAH, biocides, and alkylphenols from different products [ 48 ]. Monitoring studies often focus on the list of priority substances as defined in the EU water framework directive [ 7 , 9 , 10 ]. Construction products are usually complex mixtures containing many more chemicals than included on the list of priority substances: In addition, the transformation of substances during the service life can result in as yet unknown substances and will be an important task for non-targeted analysis and fundamental research.
Identifying relevant substances leaching from the materials is, therefore, quite a challenge. Usually, the process is a stepwise approach and depends on the information available. The formulation of the product, if it is available, is a good starting point for substance identification. This compound list can be checked for substances that are classified as environmental hazards in accordance with the globally harmonized system of classifying and labeling chemicals [ 49 ] or those included in the indicative list [ 50 ].
Especially substances with a high acute toxicity hazard statement H and with long-lasting effects H, H are of concern. Knowledge of the presence of potential dangerous substances alone is not sufficient information, as total content is a poor indicator of the leaching potential and the resulting concentrations in the eluates. Furthermore, dangerous substances in the bulk material do not have to be reported if the concentrations are below reporting thresholds.
The screening of eluates is another way to identify relevant substances. While for inorganic analytes, the number of possible analytes is limited if the analysis of different species of a single element is not considered , the number of organic compounds including degradation products is very high. Either gas chromatography coupled with mass-selective detection GC—MS or liquid chromatography coupled with mass-selective detection LC—MS might be used for screening. The availability of commercial mass spectra libraries facilitates identification. The structural elucidation of compounds not included in the libraries is hampered by hard ionization techniques, which often do not allow the identification of the molecular ion [ 51 ], and by the sometimes high number of molecular formulas that can be attributed to low-resolution mass spectra [ 52 ].
Even with more sophisticated methods, such as the use of MS classifiers [ 52 ] and fragmentation patterns [ 53 ], structural elucidation is challenging. Furthermore, GC—MS is limited to volatile compounds, and the sample preparation steps necessary to transfer analytes from aqueous eluates to an organic solvent compatible with GC—MS may bias identification of certain analytes.
In addition, sample preparation procedures do not necessarily select between analytes and other substances. Therefore, a concentration of additional substances in the eluates can increase disturbing matrix effects on quantification methods. Sample preparation with the aforementioned drawbacks may also be used for LC to enrich the analytes by e. The results of a collaborative trial for non-targeted screenings organized by the NORMAN Association network of reference laboratories, research centers, and related organizations for monitoring of emerging environmental substances reveal that generic HPLC methods using C 18 -columns are suited; but especially for very polar compounds with early retention times, special methods may have to be used [ 55 ].
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The absence of comprehensive spectra libraries necessitates an elaborated strategy for data handling. This automated data processing includes subtracting signals present in blank samples, filtering instrumental noise, mass filtering, peak detection, and the search for homologue series. High mass accuracies together with isotopic structures are essential for assigning a molecular formula, which can be used to search databases such as Pubchem and Scifinder for possible chemical structures.
These structures are used to predict fragmentation and retention times in silico and to rank the candidates by the match factors of prediction and measured data [ 51 , 56 ]. This approach is limited to compounds present in databases. Structure elucidation from the experimental data alone is very challenging; Holcapek et al. Not all compounds tentatively identified by the exact mass of adducts of the molecular ion or the fragmentation pattern can be further considered, and plausibility should be evaluated using all available data.
The ECHA chemical database might be helpful to identify chemicals with high production and use volume. Furthermore, information on typical usage is given. Environmental monitoring data can also help to identify relevant substances. However, it should be noted that lack of environmental data does not necessarily mean that these compounds are not present, if they were not included in monitoring programs.
Selected identified compounds have to be fully confirmed by means of analytical standards as reference. Chemical monitoring alone can never be complete, as the sampling and sample preparation strategy already miss certain analytes. This is also true of the detection method. Furthermore, in non-targeted screening approaches, only some of the compounds present are usually identified. Identification of every small signal near the limit of detection seems impossible. Chemical concentrations alone can be linked to the ecological relevance of these compounds only if information on possible negative effects is available.
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Assessing the effects caused by the leachate might, therefore, be a tool supplementary to chemical analysis. Ecotoxicity tests can be a valuable tool to indicate whether environmental impact has to be expected from a certain construction product. If no efforts are made for harmonizing these procedures a multiplicity of tests will result. It is clear that this variety of schemes will not allow the data to be compared worldwide and will hence, create problems for the interpretation of data by the different regulatory bodies.
Different groups of analysts i. Closer relationships between these groups would certainly encourage joint efforts for harmonizing these procedures which could, in some cases, be adapted for different matrices for a given purpose e. At this stage, it was deemed necessary to discuss critically possible strategies to harmonize leaching and extraction schemes for environmental risk assessment and a workshop was held on 4 June, , with participants covering different fields of expertise. Jelas sekali, pengurusan sisa yang sesuai perlu digunakan dalam senario ini. Abu terbang arang batu; ujian larut resap tangki; unsur major; logam toksik.
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