# Ecotoxicological Assessment of Soils Reclaimed with Waste
## 4 Discussion
The validity of using an integrated approach in the remediation of degraded areas, which combines pH correction, restoration of organic matter, and improvement of soil structure, is confirmed in studies by other authors [29]. The Microbial Assay for Risk Assessment (MARA) test is a valuable tool for assessing the ecotoxicity of soils, including those enriched with compost, mineral wool, or sewage sludge. This test uses 11 different microorganisms to assess the toxic effects of contaminants in the soil environment. The MARA test has been used, among other applications, to assess the ecotoxicity of soils contaminated with polycyclic aromatic hydrocarbons (PAHs) [34] and pesticides [35]. Additionally, the MARA test is used to assess the degree of biotoxicity in reclaimed soil. The addition of compost to soil can affect its quality, including its ecotoxicity. A study using ecotoxicological tests, including the MARA test, showed that the addition of compost increased soil toxicity at higher concentrations [36]. It suggests that, although compost can improve soil properties, its dose must be appropriately selected to avoid adverse effects. Mineral wool in combination with sewage sludge has also been shown to have a positive effect on the chemical and biological properties of degraded soils, although the specific use of MARA in this context has not been described in detail [37]. Sewage sludge, depending on the treatment method and origin, can exhibit various ecotoxicological effects. According to [PERSON] et al. (2010), compost sewage sludge is more stable and less toxic than thermally dried sludge, which exhibits higher toxicity due to its instability [38]. The use of sewage sludge in soil can have both beneficial and harmful environmental effects. This work also demonstrated that the addition of mineral wool, as well as its combination with sewage sludge, reduces soil toxicity. However, when only sewage sludge was used, the soil was still highly toxic. As reported by other authors, the application of sewage sludge to soil can provide significant agronomic benefits by improving soil fertility and structure. However, it also poses potential environmental hazards due to the presence of heavy metals, pathogens, toxic organic compounds, and new contaminants. Effective treatment and continuous monitoring are crucial for mitigating these hazards and ensuring the safe use of sewage sludge in agriculture. The impact of sewage sludge on soil toxicity varies depending on the soil type. For example, sandy soils may exhibit different levels of toxicity compared to clayey or loamy soils [38; 39]. In addition, sewage sludge often contains potentially toxic heavy metals such as Zn, Cu, Pb, Cd, and Ni. Furthermore, the combination of contaminants, such as non-steroidal anti-inflammatory drugs and other pharmaceuticals, in sewage sludge may interact with heavy metals and antibiotic resistance genes, thereby complicating their environmental impact [40]. Long-term use may lead to the accumulation of these metals in the soil, which may be toxic to plants, soil microorganisms, and soil invertebrates [41; 42; 43; 44; 45; 46]. Heavy metals in sewage sludge may adversely affect soil microbial communities, reducing their diversity and function [28; 41; 47]. Furthermore, the presence of heavy metals may inhibit plant growth and lead to the accumulation of these metals in plant tissues, which poses a risk to the food chain [39; 44; 48]. Various tests have shown that sewage sludge may have ecotoxicological effects on various soil organisms, including earthworms (_Eisenia fetida_), plants (_Lepidium sativum_), and some microorganisms, disturbing the ecological balance. This effect is often due to the presence of heavy metals and other contaminants in the sludge [49; 50; 51]. The results of this study showed that the most sensitive bacterium in the sample, with only sewage sludge added, was _Kurthia gibsoni_.