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While curricular assessments can give insight as to the extent sustainability is integrated into higher education study programs, issues remain regarding how assessments are conducted. Previous research has identified and compared various sustainability assessment tools for higher education, but there is a gap in literature studying issues arising from measurement. This paper highlights the need for discussions on this topic by exploring validity issues arising from a case study and discusses the potential of utilizing a supplementary course file during curricular assessments. To achieve this objective, a KU Leuven Faculty of Economics and Business program has been assessed using two different approaches, namely 1) a scan of a European Credit Transfer and Accumulation System (ECTS) file and 2) an instructor self-assessment via a supplementary course file. Based on this research, these two approaches to curricular assessment yield substantially different results, which gives rise to the need to further consider the validity of such assessments. While utilizing an instructor self-assessment (e.g., a supplementary course file) during assessments can help overcome some potential shortcomings and biases of ECTS file scans, both approaches are flawed in assessing true sustainability integration into a program. The varying conceptualizations of sustainability and the lack of uniformly adopted assessment approaches has the potential to create validity issues with the assessment of sustainability in higher education. Acknowledging sustainable development as a contested concept, and developing a faculty-specific conceptualization, can help in approaching assessments in a meaningful way.

pH is one of the key parameters that determines heavy metal mobility in soils, sediments and waste materials. In many respects leaching behaviour as reflected by the pH(stat) leaching tests provide a better means of assessing environmental impact than analysis of total elemental composition. This paper discusses the use of pH(stat) leaching tests as a tool to assess the potential mobilisation of trace metals from soils, sediments and waste materials. The possibilities of pH(stat) leaching tests are illustrated by means of different examples. The mathematical fitting of metal leaching behaviour from soils and sediments enabled a distinction between 5 groups of elements with a different leaching behaviour, which could be related to 'pools' with different reactivity. Contrary to single and sequential extractions, where pH is difficult to control, the reactivity and mobility of metals at a user-defined pH can be investigated. Moreover, the potential buffering capacity of the sample and its sensitivity to pH changes as a result of external stresses (e.g. soil acidification, liming) can be estimated. A multidisciplinary approach combining mineralogical analysis (X-ray diffraction) with chemical analysis, pH(stat) leaching tests and geochemical modelling (MINTEQA2) can provide information on the solid-phase speciation and reactivity of heavy metals in soils, sediments and waste materials. Besides the influence of pH on heavy metal leaching behaviour, additional information on heavy metal leachability and retention by the solid matrix was obtained from the kinetics of metal release during a pH(stat) test.

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Inherently formed iron-based water treatment residuals (WTRs) were tested as alternative sorbents for multi-heavy metal removal from synthetic solutions, contaminated sediments, and surface waters. The WTRs were mainly composed of iron (hydr)oxides and had a high BET surface area (170.7 m 2 /g), due to the presence of micro-and mesopores. The sorption capacity of 2 WTRs for As(V), Cd 2+ , Pb 2+ and Zn 2+ from synthetic solutions surpassed that of a commercially available goethite by 100-400% for single contaminant tests, and by 240% for total sorption in multi contaminant tests. The maximum sorption capacity of WTRs towards As(V), Pb 2+ and Zn 2+ was estimated by Langmuir equation fitting to range between 0.5 to 0.6 mmol/g, and their maximum sorption capacity for Cd was 0.19 mmol/g. WTRs performed significantly better than goethite for adsorption of cationic contaminants (Cd, Co, Ni, Pb, Zn) in the sediment tests, independent of the dosage or sediment sample. At the highest WTRs dosage (250 mg/g), concentrations of the cationic contaminants decreased by at least 80%, while approximately 40% removal was obtained with 50 mg/g dosage. Sorbent mixtures composed of WTRs with goethite, and with a clinoptilolite natural zeolite were used to reduce As leaching. The sorbent mixtures delivered the desired performance, with the natural zeolite performing better than the goethite as an amendment to WTRs. In addition, up to 90% removal of surface water contaminants was achieved with both fresh WTRs and the WTRs regenerated using 0.01 M EDTA.

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In the present study, different leaching tests were applied on well-characterised samples in order to obtain information on the potential mobility of heavy metals and arsenic. The information deduced from the different methods was compared and evaluated. Besides the comparison of heavy metal release in cascade-, column-and pH stat leaching tests, attention was also paid to the assessment of release kinetics during leaching tests and to the mathematical modelling of leaching behaviour. The aim of this study was to understand the origin of possible discrepancies between the results of different leaching tests. The compatibility of the results of different leaching tests is, besides the inherent differences between methods (single batch tests versus dynamic leaching tests, the duration of the tests, liquid/solid (L/S) ratio,…) to a major extent determined by keyfactors such as pH and redox potential. Depending on soil and sediment properties (e.g. acid neutralizing capacity (ANC)) these 'key-factors' varied during and at the end of extractions and leaching tests, even when the initial test conditions (e.g. the pH of the reagent) were equal for all test cases. During cascade-and column leaching tests, pH (which is initially 4) will mostly increase, but the extent of this pH-increase mainly depends on the acid neutralizing capacity of the sample. Therefore, measuring the pH of all leachates that are collected during these tests is mandatory for the interpretation of the results. Moreover, the monitoring of other variables such as DOC, anions and major elements can give indications on the reactions that are responsible for the release of elements (e.g. the dissolution of organic matter) and greatly improve the interpretation of the results.