| Abstract [eng] |
Sewage sludge (SS) reuse in agriculture is encouraged due to its nutrient-rich composition; however its high heavy metal content, potential environmental risks, and limited guidelines for safe application pose significant problems. Contaminants accumulating in SS-treated soils can harm soil organisms, reduce soil fertility, endanger food crop yields and enter the food chain, contaminate surrounding areas. Furthermore, excessive sludge application can result in long-term soil pollution, leading to the need to clean up amended sites. The use of energy crops in soils treated with SS is a sustainable dual-purpose method for soil remediation that combines it with bioenergy production. The aim of this study was to assess the potential of energy crop industrial hemp (Cannabis sativa L.) for soil remediation and bioenergy production in soils amended with sewage sludge (SS) and sewage sludge char (SSCh) at application rates of 25 200 Mg/ha. SS and SSCh application highly affected Cr, Cu, Ni and Zn concentrations in soil (ANOVA, FSS > 21.80, FSSCh = 35.20, p < 0.001) and led to increased metal concentrations (p < 0.05). Soil amended with 25-100 Mg/ha SS and 25 Mg/ha SSCh had moderate heavy metal contamination. Application of 200 Mg/ha SS and 50-200 Mg/ha SSCh caused significant pollution. Our findings show that the application of SSCh resulted in more polymetallic soil contamination than the soil amended with the same SS dose. Heavy metal concentrations in soil were significantly reduced after industrial hemp cultivation, with higher removal efficiencies at moderate sludge application rates (25 50 Mg/ha). The heavy metals removal efficiency could be ranked Zn > Cu > Cr > Ni. Only marginal removal was detected for Ba, Fe, Na, Ti and Al. These reductions underscore industrial hemp s effectiveness in mitigating heavy metal posed environmental risks. The optimal fertilization with SS or SSCh could be up to 25 Mg/ha, when the highest efficiency of contaminant removal from the soil and the highest plant biomass production and bioenergy production were observed. Higher application rates increased the risk of heavy metal contamination, emphasizing the importance of optimized sludge usage. The study highlights the dual benefits of industrial hemp cultivation in mitigating soil pollution and contributing to renewable energy sources, offering a sustainable strategy for managing sewage sludge and its environmental impacts. |
