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Abstract

For the evaluation of long-term environmental impacts caused by the release of contaminants from monolithic building and waste materials, the NEN 7375 test has been proposed. Over a period of 64 days, at specific points in time, the leaching solution (demineralised water) is replenished. By applying the NEN 7375 test, leaching of contaminants that is based mainly on diffusion is followed. In the Doctoral Dissertation, modified leaching protocols were applied and results evaluated against those obtained by the NEN 7375 test. In the modified protocols, synthetic sea, surface and MilliQ water were used for the leaching of selected elements and chromate, arsenate, molybdate and vanadate from compact and ground building composites (98% mixture of fly ash (80%) and cement (20%), and 2% of electric arc furnace (EAF) dust) over 6 months. The leaching solutions were not replenished, imitating both the diffusion and the dissolution of contaminants. The data revealed a larger extent of leaching when the leaching solution was not replenished. More extensive was also the leaching from ground composites, which simulated the disintegration of the material over time. The composition of the leaching solution influenced the release of the matrix constituents from the composites and, consequently, the amount of elements and their chemical species. Synthetic sea and surface water used as leaching solutions, without replenishing, were found to be suitable to simulate the conditions when the building material is immersed in stagnant environmental waters. Fly ash, cement and EAF dust are frequently mixed in building composites. The data revealed that chromate, molybdate, vanadate and arsenate may be leached in significant amounts, causing a potential environmental threat.
Next, a high performance liquid chromatography - inductively coupled plasma mass spectrometry (HPLC-ICP-MS) procedure was used for simultaneous speciation of chromate, arsenate, molybdate and vanadate. First, the behaviour of chromium (Cr), arsenic (As), molybdenum (Mo) and vanadium (V) species in different oxidation states was studied during their separation under acidic (pH 5) and alkaline (pH 12) conditions. At alkaline pHs chromate, arsenate, molybdate and vanadate were simultaneously separated and eluted at retention times from 390 to 450 s, 230 to 270 s, 340 to 430 s and 270 to 380 s, respectively, and detected on-line by ICP-MS, recording m/z 52, 75, 95 and 51, respectively. When V species were leached in significantly higher concentrations than Cr, Mo and As, simultaneous speciation analysis was particularly difficult. Therefore, the detection was possible at the low abundance (0.25%) 50V isotope, which is also the mass of the 50Cr isotope (abundance 4.345%), due to selective separation between V and Cr species. Good repeatability of the measurement (RSD better than ± 3.0%) and quantitative elution of elemental species (column recoveries 99–105%) were obtained.
Finally, sensitive and reliable analytical procedure for the determination of hazardous hexavalent Cr (Cr(VI)) in sediments of industrially exposed sites of the Sava River (stainless steel production and impact of metallurgic industry) was developed. An ultrasound-assisted extraction procedure (80 °C, using 2% NaOH + 3% Na2CO3 as the extraction solution) was found to be optimal to leach the total amount of Cr(VI) from sediments. The addition of 0.4 mol L-1 MgCl2 prevented oxidation of Cr(III) during the extraction step. To control for species interconversion during the analytical procedure and for an accurate calculation of the Cr(VI) concentration by speciated isotope dilution (ID)-ICP-MS, the alkaline extract was doubly spiked with enriched 50Cr(VI) and 53Cr(III). The accuracy of the determination of Cr(VI) was verified by analysing the certified reference material CRM 041 (Cr(VI) in soil), and by spike recovery test. Low limits of detection (LOD) and quantification (LOQ) (1.25 and 4.0 μg Cr(VI) kg-1, respectively) and good repeatability of measurement (relative standard deviation better than ± 4.8%) were obtained. The use of isotopically enriched tracers importantly contributed to the validity of the obtained results. The analytical data revealed that Cr(VI) concentrations in sediments of the Sava River did not represent any known environmental hazard.