Dredged sediment contaminated with heavy metals can be remediated through phytoremediation. The main challenge in phytoremediation is the limited availability of heavy metals for plant uptake, particularly in multi-contaminated soil or sediment. This study aimed to assess the effect of the nitrogen fertilizers (ammonium nitrate (AN), ammonium sulfate (AS), and urea (UR)), organic acids (oxalic (OA) and malic (MA) acids), and their combined addition to sediment on enhancing the bioavailability and phytoremediation efficiency of heavy metals. The sediment dredged from Begej Canal (Serbia) had high levels of Cr, Cd, Cu, and Pb and was used in pot experiments to cultivate energy crop rapeseed (Brassica napus), which is known for its tolerance to heavy metals. The highest accumulation and translocation of Cu, Cd, and Pb were observed in the treatment with AN at a dose of 150 mg N/kg (AN₁₅₀), in which shoot biomass was also the highest. The application of OA and MA increased heavy metal uptake but resulted in the lowest biomass production. A combination of MA with N fertilizers showed high uptake and accumulation of Cr and Cu.

In this work, two extraction techniques, conventional and ultrasound-assisted extraction (UAE) techniques, were employed for the extraction of natural bioactive compounds (NBCs) from the areal parts of industrial hemp (Cannabis sativa L. cv. Helena) at two harvesting stages: (i) the beginning of flowering and (ii) the full flowering of the hemp plants. In the conventional extraction, the effect of different extraction solvents on the extraction yield and the content of NBCs was examined. The extraction temperature, extraction time, and ultrasonic power were chosen for the process parameters in UAE. The highest value of the investigated responses in UAE-obtained extracts was higher compared to extract obtained with conventional extraction techniques when the same solvent was used (50% ethanol): extraction yield (17.54 compared to 15.28%), content of total phenols and total flavonoids (1.7795 compared to 1.0476 mg GAE/mL and 0.6749 compared to 0.3564 mg CE/mL, respectively) and cannabidiol (0.8752 compared to 0.4310 mg/mL). Comparing the plant material in different developmental stages, it can be concluded that hemp aerial parts at the beginning of the flowering stage represent a good source of the phenolic compound with sinapic acid and apigenin being dominant, while hemp aerial parts in the full flowering stage represent a good source of cannabinoids.

The sustainable management of dredged sediments contaminated with heavy metals represents a major environmental challenge. This study evaluated the phytoremediation potential of hemp (Cannabis sativa L.) and sorghum (Sorghum bicolor L.) cultivated in metal-enriched sediment from the Bega Canal (Cu = 204 mg kg⁻¹, Pb = 171 mg kg⁻¹, Cr = 281 mg kg⁻¹, Ni = 56 mg kg⁻¹, Cd = 6.8 mg kg⁻¹) and examined the effects of glutamic (GA) and tartaric (TA) acids (20 mmol kg⁻¹) on sediment properties and metal uptake. Pot experiments under natural conditions (n = 3, 6–8 weeks) showed that GA treatment resulted in cation exchange capacity (CEC) values ranging from 31.0 to 58.5 cmolc kg⁻¹, which were lower than in the initial sediment (60.7 cmolc kg⁻¹) but still higher than in the corresponding controls and TA treatments. GA also increased electrical conductivity from 435 to 1189 µS cm⁻¹, which may indicate enhanced ion mobility and be consistent with redox-related processes, whereas TA maintained near-neutral pH (8.0–8.2) and caused only minor changes in CEC and EC, preserving overall structural stability. Hemp produced up to 40% more biomass than sorghum and allocated a relatively larger share of Cu, Pb and Cd to shoots, whereas sorghum retained up to 80% of total Cr and Ni in roots. Bioaccumulation factors ranged from 4.3 for Cu in hemp (GA) to 20.8 for Cu in sorghum (GA), while translocation factors remained <1.0 in both species, indicating that root-based phytostabilization was the dominant mechanism. The results demonstrate that combining low-molecular-weight organic acids with energy crops can effectively enhance metal mobility and plant uptake, offering a viable route for sediment remediation and biomass valorization within circular economy strategies.

Biochar is promising material used to enhance organic matter content in soil and to mitigate climate change through carbon sequestration. In addition to that, biochar increases crop yield by means of improving soil capacity for water- and nutrient-holding capacity, and due to its adsorption capacity, it decreases mobility and bioavailability of organic pollutants and heavy metals. Biochar (BC) is a carbon-rich and porous material produced by pyrolysis of biomass under oxygen-limited conditions. The unwanted spread of pesticides to the environment and their leaching into the groundwater is of great concern. The aim of this work is to investigate the potential of BC to improve the adsorption capacity for two triazine herbicides in three different soil types with various organic matter (OC) content. Triazine herbicides (terbuthylazine and atrazine) were chosen as the most widely used pesticides in recent decades. The main difference among between three different soils types used in the study is in their OM content, which was 0.48%, 2.34% and 4.12%, respectively for Soil1, Soil2, and Soil3. The BC used in this work is commercially available compost-activated biochar produced by pyrolysis of beechwood chips at 700 oC. A batch adsorption experiments were conducted to investigate herbicide adsorption in soil without BC and with the amendment of BC (0, 1, 5, and 10%). The concentration of herbicides in the aqueous phase at equilibrium (which is achieved after 72 h) was determined by GC-MS. The adsorption isotherms were well described with the Freundlich model (R2 values range from 0.714 to 0.998). Values of Freundlich exponent n were less than 1 (from 0.314 to 0.897), which indicates that the isotherms are of L-type. This shows that with the increase of compound concentration relative adsorption decreases because of the saturation of adsorption sites. Single-point distribution coefficients (Kd) were calculated at selected equilibrium concentration (ce= 100 µg dm–3). Kd values increased with an increase of BC content, especially for 5% and 10% of BC amendment. Kd values of atrazine in Soil1 were in the range 1.91–14.55, in Soil2 from 4.76–15.65, and in Soil3 from 4.79–20.11, while Kd values of terbuthylazine ranged from 1.14–30.92 in Soil1, from 14.13–50.74 in Soil2, and from 12.65–47.03 in Soil3. In unamended Soil1 the adsorption of both herbicides was lower in comparison to unamended Soil2 and Soil3, which is in accordance with the well-known fact that the OC content of soil primarily affects the adsorption of pesticides. The adsorption capacity of Soil 2 and Soil 3 was not significantly different. It is observed that the adsorption of terbuthylazine is higher in all soil types, which is in accordance with its lower solubility and higher affinity for OM in comparison to atrazine. It is shown that sorption capacity of soil for pesticides could be improved by adding biochar into the soil, thus reducing herbicide mobility into the environment. Further studies will be conducted by column experiments to investigate more realistic environmental scenarios.