Although recent studies show that the iron oxides do not enter or accumulate in plants, they may preclude the transport of water and nutrients in the plants through/as a consequence of their aggregation on the surface of the roots. The feasibility of using iron oxide nanoparticles to modify the availability of trace elements (TEs) to Helianthus annuus in the soil as well as their interference with the plant response during an imposed water deficiency stress were studied in a pot experiment. Plants were grown in a compost pre-amended contaminated soil with and without nano-maghemite (NM) and later exposed to drought. The nano-amendment promoted the growth of H. annuus (higher (25 %) dry weight than in the same soil without NM), mainly due to the insolubilisation of pore water Zn in the soil and the consequent reduction of its availability to the plants. During the water stress, NM did not cause an increase in the accumulation of proline or total amino acids in the plants, which are normally used as drought stress indicators, compared to the control plants without NM. In conclusion, NM could be useful soil amendments during phytoremediation procedures, since it can immobilise TEs in the soil without disrupting the plant water balance.

Nanoparticles have been used widely in industry and consumer products in recent years. Most of the engineered nanoparticles (NPs) eventually enter municipal wastewater treatment systems (WWTP) through sewers. In this experimental study, the impact of nano-TiO₂, nano-ZnO, and nano-Ag on methanogenesis was investigated during mesophilic batch anaerobic digestion of primary sludge. The experimental sets consisted of 1, 10 mg NP/g TS, and a control group for TiO₂NP, ZnO NP, and Ag NP, separately. The results showed that neither of the NPs used remarkably changed methane production. Methane yields in the units of m³CH₄/kg VS in were between 0.08 and 0.13 and showed no significant difference between the control groups and experimental sets for tested NPs. Soluble Ti concentrations were below 0.07 mg/L after the end of anaerobic digestion. Soluble Zn and soluble Ag concentrations were below 0.78 and 2.02 mg/L, respectively. Most of the NPs remained in the sludge rather than in aqueous supernatant. The authors suggest that the effects of the NPs, just above the sludge, or the NPs that adsorbed to sludge, on methanogenic activity at long-term exposure should be examined in the future studies.

The efficiency of phytoextraction is limited because of the low growth exhibited by plants under the stress of heavy metals. Impatiens (Impatiens walleriana) cuttings were grown in soils artificially contaminated with cadmium (Cd) and modified with chemical fertilizer to study the relationship among the leaf area, transpiration rate, and Cd accumulation. The subcellular distribution of Cd in various impatiens organs was also measured. Experimental results showed that there were positive, linear relationships between the leaf area and the transpiration rate. A similar relationship was found between the transpiration rate and the Cd accumulation in the shoots. Suitable management practices can be conducted to increase the transpiration rate and thus the plant’s phytoextraction efficiency. In the roots and leaves, Cd was mainly compartmentalized in the soluble fraction and the cell wall fraction, respectively. The varied subcellular distribution of Cd in the different organs was responsible for the high accumulation capacity.

The carbon rich material obtained from pyrolysis process, i.e. biochar, has been widely discussed during the last decade due to its utilisation as a soil amendment. Furthermore, there is an unsolved question of biomass disposal from phytoremediation technologies. The idea of contaminated biomass pyrolysis has appeared, but there is lack of information about possible biochar utilisation obtained by this process. The aim of our study was to observe sorption properties of biochar prepared from contaminated biomass and release of contaminants from biochar back into the environment. The biomass of fast growing trees and maize was harvested on a site significantly damaged by risk element contamination (Cd, Pb and Zn). Plant biomass was pyrolysed and then the batch (de)sorption experiments were settled. The results confirmed no significant differences in metal sorption ability between biochars prepared from contaminated and uncontaminated biomass under the same conditions. The trend of maximum sorption capacity of observed matrices followed the order: wood biochar + soil (WB + soil) > wood uncontaminated biochar + soil (WUB + soil) > maize biochar + soil (MB + soil) > soil for cadmium, WB + soil > WUB + soil > soil for lead and MB + soil > WUB + soil > WB + soil > soil for zinc. Despite of increase of Zn desorption from wood biochars, maximum sorption capacity of the final WB + soil system was comparable to the WUB+soil sample. Our laboratory experiments showed high potential of biochar from contaminated plants as a soil amendment with sorption abilities and minimal risk of metal release.

This study investigates the use of sericite beads and microalgae for the removal of heavy metals from acid mine drainage (AMD) and the simultaneous enhancement of biomass productivity. The experiment was conducted over a period of 6 days in a hybrid system containing sericite beads and microalgae Chlorella sp. The results show that the biomass production increased to ~8.04 times its initial concentration of 0.367 g/L as measured by an optical panel photobioreactor (OPPBR) and had a light transmittance of 95 % at a 305-mm depth. Simultaneous percent removal of Fe, Cu, Zn, Mn, As, and Cd from the AMD effluent was found to be 97.78 to 99.26 %. Biomass production was significantly enhanced by removal of heavy metal ions. We thus found that our hybrid system of sericite beads and microalgae was highly effective in removing heavy metal and in enhancing biomass production and could be a useful alternative treatment of AMD.

Urban soil amendment with organic matter can increase the steady state concentration of trace metals in urban soil. Different types of organic matter have different abilities to sorb and retain trace metals. The potential of urban soil amended with compost derived from mixed green and table waste and with maple-wood-derived biochar to retain trace metals (Cu, Zn, Cd, Pb) in the presence of de-icing salt (Na) was studied in a leaching test. Soil amended with compost retained significantly higher concentrations of Zn and Pb, as compared to soil amended with biochar, possibly due to the high cation exchange capacity of compost and its positive effect on soil pH. Indicating high ability for retaining trace metals, compost can bind contaminants originating from urban runoff water percolating through urban soil and provide a healthier medium for street tree growth.

Residual antibiotics in land-applied manure and biosolids present a potential threat to public and ecological health. It remains important to determine antibiotic degradation efficiencies for manure and biosolids waste management practices and to identify conditions that enhance antibiotic degradation. The fates of the antibiotics florfenicol, sulfadimethoxine, sulfamethazine, and tylosin were studied during pilot-scale static pile thermophilic composting, and the effects of temperature and feedstock particles on antibiotic degradation rates were tested. The antibiotics were spiked into dairy manure solids and wastewater biosolids, and treatments included aerated and non-aerated manure and biosolids/wood-product (1:3 v/v) composting. Results showed no significant differences between aerated and non-aerated treatments; on average, ≥85, ≥93, and ≥95 % antibiotic degradation was observed after 7, 14, and 21 days of composting. Greater antibiotic degradation was observed in manure compost compared to biosolids compost for florfenicol (7, 14, 21, 28 days) and tylosin (14, 28 days); however, there was no significant difference for sulfadimethoxine and sulfamethazine. Peak temperatures were 66–73, and ≥55 °C was maintained for 6–7 days in the biosolids compost and 17–20 days in the manure compost. Bench-scale experiments conducted at 25, 55, and 60 °C showed that lower temperature decreased degradation of the sulfonamides and tylosin in both feedstocks and florfenicol in the biosolids. The presence of compost particles increased antibiotic degradation, with time to 50 % degradation ≤2 days in the presence of solids (60 °C) compared to no degradation in their absence. These results indicate that thermophilic composting effectively degrades parent antibiotic compounds in manure and biosolids.

The potential of granular activated carbon (GAC) to remove iopromide and its intermediates from ozone-treated river water was evaluated. Mass spectrum analysis showed that ozone treatment lead to partial removal of iopromide (m/z 791.8) with generation of various intermediates. GAC demonstrated a lower iopromide adsorption (1.60 μg/g) in the presence of natural organic matter (NOM) compared to NOM-free water (12.54 μg/g), indicating the inhibitory effect of NOM on iopromide adsorption. Ozone treatment of the influent reduced the inhibitory effect of NOM by altering its composition and inducing polarity shift. GAC post-treatment resulted in improved removal of residual iopromide and its intermediates from the ozone-treated influent. Application of such combined treatment of ozonation followed by GAC adsorption can be an effective strategy for the removal of iopromide and its intermediates from contaminated water streams.

A series of column experiments was conducted to evaluate the effect of organic carbon fraction on long-term atrazine elution tailing for calcareous soil (foc = 0.97 %) and calcareous soil with 10 % by weight terra rossa amendment (foc = 1.20 %). Effluent atrazine concentrations were monitored for approximately 400 pore volume to understand the influence of controlling sorption–desorption kinetics on long-term tailing behavior. Laboratory studies showed that the sorption of atrazine was described by rate-limited, nonlinear reversible processes for both soils. Atrazine transport exhibited extensive elution tailing for all experiments due to the presence of hard carbon components such as black carbon and kerogen in both soils. This nonlinear sorption and extensive atrazine tailing behavior were more pronounced and extensive for soil with terra rossa amendment due to the addition of approximately 20 % organic carbon including 10 % hard carbon components from terra rossa soil. A mathematical model incorporating nonlinear, rate-limited sorption/desorption described by a continuous distribution function was used to successfully simulate atrazine transport early-time breakthrough and long-term concentration tailing for both porous media.

Microporous–mesoporous activated carbons from five different types of agro-industrial wastes were produced using chemical activation with ZnCl₂ and carbonization at mild conditions of 600 °C, comprehensively characterized and investigated for removal of methylene blue (MB) in aqueous solution, a model large-molecular-size organic pollutant. The external part of the mango pit (mango seed husk) was used for the production of activated carbon (AC) for the first time. Despite that the raw agro-materials exhibited significantly different porosity, all activated carbons produced possessed well-developed microporous–mesoporous structures showing high surface areas and micropore volumes. Further, it was revealed that the pore size distribution of raw agro-material is a more important property in development of microporous–mesoporous structure of produced ACs than their overall porosity. All activated carbons produced adsorbed MB, reaching in most cases 100 % removal from the aqueous phase. Adsorption data were fitted well to a pseudo-second-order kinetic model. For MB adsorption, the mesoporosity and the ratio of micropores accessible for MB were the key factors since there exists the size-selectivity effect on MB adsorption due to MB molecular dimensions. The molecular dimensions of MB were estimated via DFT calculations to 1.66 × 0.82 × 0.54 nm, and this parameter was correlated with determined micropore size distributions of activated carbons.