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The risk assessment of total petrol hydrocarbons (TPH) and polycyclic aromatic hydrocarbons (PAH), two of the most frequent soil and water contaminants, has to include their exposure pathways, especially the soil groundwater pathway. Threshold values have to be aquired for the amendment to the German Federal Soil Protection Contaminated Sites Ordinance. For this purpose, a batch experiment with a liquid to solid ratio (L/S) of 2 L/kg was developed. Aim of this work was to verify the robustness of this leaching procedure for TPH and PAH in different soil types against varying test conditions. Also, stir bar sorptive extraction (SBSE) was tested as alternative sample preparation of eluates for PAH analysis.
Phosphorus-fertilizers from secondary resources such as sewage sludge ash (SSA) will become more important in the future as they could substitute conventional fertilizers based on the nonrenewable resource phosphate rock. Thermochemical approaches were developed which remove heavy metals from SSA prior to its fertilizer application on farmlands. We analyzed the chemical state of mercury and selenium in SSA before and after thermochemical treatment under different conditions for P-fertilizer production by X-ray absorption near edge structure (XANES) spectroscopy. In some incineration plants the mercury loaded carbon adsorber from off-gas cleaning was collected together with the SSA for waste disposal. SSAs from those plants contained mercury mainly bound to carbon/organic material. The other SSAs contained inorganic mercury compounds which are most probably stabilized in the SSA matrix and were thus not evaporated during incineration. During thermochemical treatment, carbon-bound mercury was removed quantitatively. In contrast, a certain immobile fraction of inorganic mercury compounds remained in thermochemically treated SSA, which were not clearly identified. HgSe might be one of the inorganic compounds, which is supported by results of Se K-edge XANES spectroscopy. Furthermore, the chemical state of selenium in the SSAs was very sensitive to the conditions of the thermochemical treatment.
Sulfonamides (SAs) and their metabolites present severe hazards to human health and the environment, mainly because of antibiotic resistance. Knowledge of their bioavailability, including their sorption to soils and their impact on the soil-groundwater pathway, is crucial to their risk assessment. Laboratory batch and column leaching tests are important tools for determining the release potential of contaminants from soil or waste materials. Batch and column tests were carried out with soils differing in particle size distribution, organic matter content and pH, each spiked with sulfonamides (sulfadimethoxine (SDM), sulfaguanidine (SGD), sulfisoxazole (SX)). In order to test the applicability of leaching tests to polar contaminants batch and column tests were also compared. In the column tests, release was found to depend on the properties of both soil and sulfonamides. The fastest release was observed for coarse-grained soil with the smallest organic matter content (MS soil; 100% decrease in concentration until liquid-to-solid ratio (L/S) of 0.9 L kg-1 for all SAs). The slowest release was established for sulfadimethoxine (24.5% decrease in concentration until L/S 1.22 L kg-1). The results of the batch and column tests were comparable to a large extent, with slightly higher concentrations being obtained in the column test experiments of fine-grained soils with a high organic matter content.
Synthetic athletic tracks and turf areas for outdoor sporting grounds may release contaminants due to the chemical composition of some components. A primary example is that of zinc from reused scrap tires (main constituent, styrene butadiene rubber, SBR), which might be harmful to the environment. Thus, methods for the risk assessment of those materials are required. Laboratory leaching methods like batch and column tests are widely used to examine the soil–groundwater pathway. We tested several components for artificial sporting grounds with batch tests at a liquid to solid (LS) ratio of 2 L/kg and column tests with an LS up to 26.5 L/kg. We found a higher zinc release in the batch test eluates for all granules, ranging from 15% higher to 687% higher versus data from column tests for SBR granules. Accompanying parameters, especially the very high turbidity of one ethylene propylene diene monomer rubber (EPDM) or thermoplastic elastomer (TPE) eluates, reflect the stronger mechanical stress of batch testing. This indicates that batch test procedures might not be suitable for the risk assessment of synthetic sporting ground components. Column tests, on the other hand, represent field conditions more closely and allow for determination of time-dependent contaminants release.
Stir bar sorptive extraction (SBSE) is an equilibrium extraction method used amongst others for the analysis of polycyclic aromatic hydrocarbons (PAH) in aqueous samples. We compared SBSE to liquid–liquid extraction (LLE) for aqueous eluates obtained from batch and column tests of PAH contaminated soils to check whether SBSE might be considered as an alternative sample preparation method. We used soils with different particle size distribution, organic matter content, and resulting eluate turbidity to test the sample preparation methods on eluates with matrices of varying complexity. Furthermore, we studied the influence of diluted organic matter (DOM) on the PAH sorption process to the polymer coating of the stir bar during SBSE. In the majority of cases, we found higher PAH concentrations (up to 288%) with SBSE than with LLE. The turbidity correlates with the difference in PAH results, i.e. the greater the turbidity in the eluate, the more PAH we found with SBSE compared to LLE. We observed no similar trend regarding the amount of total organic carbon (TOC). The presence of DOM in the eluate seems to hamper the SBSE slightly, the PAH recovery varied between 82 and 104%.
Stir bar sorptive extraction (SBSE) and solid phase microextraction (SPME) are well-established sample preparation methods for the analysis of polycyclic aromatic hydrocarbons in aqueous samples. However, complex matrices especially characterized by slurry particles and dissolved organic matter (DOM) can hamper the extraction of PAH with both SBSE and SPME and lead to different results. Thus, we produced aqueous eluates from PAH-contaminated soils differing in particle size distribution and organic matter content and determined the PAH concentration in the eluates with both SBSE and SPME. Furthermore, we tested the influence of filtration on the PAH analysis. The excess finding of PAH with SBSE compared to SPME ranged from −16.6 to 24.5 %. The differences increased after filtration. We found a strong positive correlation of the excess finding to the total organic carbon content (TOC) and a negative one to the pH value. The results indicate that SBSE is less affected by complex matrices than SPME.