Does exposure to weathered coal ash with an enhanced content of uranium-series radionuclides affect flora? Changes in the physiological indicators of five referent plant species.

Coal ash deposited in open landfills is a potential source of environmental pollutants due to the contained toxic element content. The weathered coal ash used in this study additionally contains enhanced activity concentrations of 238U series radionuclides. This study aimed to determine the physiological effects of enhanced ionizing radiation and toxic elements on five plant species (smilo grass, sticky fleabane, blackberry, mastic and pine tree) inhabiting the coal ash disposal site. Among the potentially toxic measured elements, contents of Sb, As and especially V significantly exceeded their respective levels at the control site, as well as the content of 238U and its progenies. Significant changes in photosynthetic pigments were recorded following chronic exposure to the plants growing on the coal ash site. Different responses were also observed in the plant species regarding the activity of catalase and glutathione-S-transferase (GST). The level of lipid peroxidation markedly increased in plants from the disposal site, except in blackberry, wherein GST activity was the strongest, indicating an important role of that enzyme in the adaptation to coal ash pollutants. The results of this study suggest that the modulation of the studied biochemical parameters in plants growing on coal ash is primarily species-dependent.

The effect of stabilization on the utilization of municipal sewage sludge as a soil amendment.

This study assesses the potential use of different types of stabilized sewage sludge as a soil amendment by considering their physicochemical characteristics, nutritional status, and their trace metal and radionuclide content. The concentrations of trace metals and radionuclides were determined using ICP-OES and gamma-ray spectrometry, respectively. For determining nutritional status and chemical characterization, this study followed standard ISO-recommended procedures. Data analysis revealed that anaerobic sludge contains higher concentrations of Cr, Hg, and Ni compared to aerobic and non-biologically stabilized sludge. A similar observation was observed in the case of 226Ra, 210Pb, 228Ra, and 228Th. Furthermore, the high levels of P and N in aerobic sludge suggest that biologically stabilized sludge has the potential to be a good fertilizer. In addition, the study finds strong evidence that nutrients are involved in the adsorption of metals and radionuclides onto sludge biomass. Overall, eight of the nine studied sludge samples are safe for agricultural use since the concentrations of trace metals fall well below the limits set by Croatian legislation (NN 38/08). In addition, the levels of radionuclides do not pose a radiological risk. This means that soil conditioning with sewage sludge remains a viable strategy for nutrient recovery from municipal waste, although long-term impact assessments of repeated applications are necessary.