Poultry litter and bedding materials generated from laying chicken farm often contain high levels of arsenic when roxarsone is included in feed to combat disease and improve egg production. This study was conducted to determine the fate and ecological risk of arsenic species in poultry litter which applied to agricultural field. Three poultry litter application rates (0, 10, 60 % dry weight) were used to amend soil samples under anaerobic and aerobic circumstances, respectively, incubated at 30 % moisture content for 110 days. Experiment indicated that under anaerobic circumstance, As(V) and As(III) decreased in treatments applied 60 and 10 % rates within initial 7 days, subsequently methylated arsenic displayed increasing, suggesting biotic activity transformed inorganoarsenical to methylated arsenic species. In contrast, As(V) dropped in the first 7 days but increased thereafter under aerobic circumstances, with methylated arsenic increasing, implying abiotc and biotic activities enhanced arsenic speciation. Based on different arsenic species, we evaluated their ecological risk in poultry litter respectively. It was found that ecological risks under anaerobic circumstance were higher than under aerobic circumstance of the same poultry litter rates, and higher poultry litter rates applied to soil would bring about higher ecological risk. We suggest that poultry litter should be disposed at low rate (approximately 10 %) and applied to soil surface to create aerobic circumstance for the initial 2 months time, but should be buried into a deeper depth thereafter.

This study compares the efficiency of a synthetic chelate (ethylenediaminetetraacetic acid-EDTA), a natural low-molecular-weight organic acid (citric acid), and their combination for phytoremediation of Cu-pyrene co-contaminated soils. Zea mays was grown in each soil and amended with citric acid and/or EDTA to understand the effect of chelates during phytoremediation of contaminated soils. In Cu or pyrene-contaminated soil, plant growth was negatively affected by EDTA (43 %) and citric acid (44 %), respectively, while EDTA + citric acid promoted (41 %) plant growth in co-contaminated soil. EDTA and EDTA + citric acid increased the phytoextraction of Cu in Cu-contaminated and co-contaminated soils, respectively. In pyrene-contaminated soil, all tested chelates increased the dissipation of pyrene reaching 90.4 % for citric acid, while in co-contaminated soil, only citric acid or EDTA + citric acid enhanced pyrene dissipation. These results show that Z. mays can be effective with the help of chelates in phytoextraction of Cu and dissipation of pyrene in co-contaminated soil.

Rhamnolipid is a biosurfactant produced by several Pseudomonas species, and can wet hydrophobic soils by lowering the cohesive and/or adhesive surface tension. Because of its biodegradability, rhamnolipid is believed to have minimal adverse impact on the soil and groundwater after usage. Applications of rhamnolipid to improve irrigation in agricultural soils thus have obvious advantages over other chemical wetting agents, especially under drought conditions. Due to global warming, soil amendment with biochar has been commonly practiced in agricultural soils to increase the soil water-holding capacity. As such, rhamnolipid transport in biochar-amended agricultural soils needs to be characterized. In this research, we found that rhamnolipid transport in biochar-amended agricultural soils was hindered by retardation (equilibrium adsorption) and deposition (kinetic adsorption), which was well represented by the advection-dispersion equation based on a local equilibrium assumption. A linear equilibrium adsorption was assumed in the advection-dispersion equation simulation, which was proved to be acceptable by studying the breakthrough curves. Both rhamnolipid equilibrium adsorption and kinetic adsorption increased with the increase of the biochar content in the agricultural soil.

The changes in the availability of selected elements (Ca, Mg, K, Al, As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) 16 years after amphibolite treatment were studied in the root zone of spruce (40 and 80 cm from the stem base) using the diffusive gradient in thin film (DGT) technique. The effective concentrations of some of the tested elements significantly increased (Ca (34 %), Mg (31 %), K (65 %), Al (143 %), Fe (242 %), and Pb (27 %)) in 80 cm distance from the stem, whereas the total and the water-soluble concentrations of the elements did not differ from the control. The changes in effective concentrations of the elements in soil were related to higher vitality of the trees on amended soil in contrast to the control.

Degradation and fate of sulfamethazine (SMZ) were determined under aerobic and anaerobic conditions in soil with and without swine manure amendment. For both aerobic and anaerobic conditions, SMZ disappeared rapidly during the first 7 days followed by slow disappearance which may indicate that SMZ had become more persistent and less available. For soils receiving 100 mg/kg of SMZ, the percent of SMZ remaining in the soil after 63 days were between 25 and 60 %. Depending on the initial SMZ concentration, estimated half-lives for aerobic and anaerobic incubations ranged from 1.2 to 6.6 and 2.3 days to more than 63 days, respectively. Addition of manure (0.054 g/g soil) did not significantly affect the half-lives of SMZ. Inhibitory effects of SMZ on anaerobic microbial respiration were observed in unamended soil at concentrations of 50 mg/kg or higher, but only transient inhibitory effects were found in aerobic soil. Five to 22 % of the¹⁴C[phenyl]-SMZ added were extracted at the end of the incubations while 70 to 91 % of the¹⁴C were converted to bound (non-extractable) forms in both manure amended and unamended soil. Only 0.1 to 1.5 % of¹⁴C-SMZ was mineralized to¹⁴CO₂. Disappearance of SMZ in sterilized soil was not completely halted indicating possible contribution of abiotic processes to the disappearance of SMZ in soil.

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.

Biosorption is a low-cost green technology for water pollution decontamination. Recently, new adsorbent materials (raw or modified) were synthesized and tested in a wide variety of different pollutants. Among them, researchers pay attention on an alternative use of composts. The major use of composts is as soil amendments to improve the fertility of soils. For the first time in literature, the present review article gathers information about the applicability of compost materials as biosorbents in batch modes. For this purpose, equilibrium modeling and isotherm, kinetic, and thermodynamic studies were discussed in details. Moreover, many parameters such as temperature, pH, and contact time were also analyzed. The main pollutants studied in this work are dyes and heavy metals either in single- or multi-component systems.

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.

Nitrogen- heterocyclic polycyclic aromatic hydrocarbons (N-PAHs) are ubiquitous constituents of contaminated sites in which their high water solubility and lower k ₒw values imply greater mobility and impacts. Biodegradation is a major route of loss for organic contaminants in soil. In this study, microbial degradation was investigated in soil artificially contaminated with N-PAHs and monitored for over 200 days. The results showed that all the aromatic chemicals exhibited loss with increasing incubation time; however, only 0.05 ± 0.04 mg kg day⁻¹ loss was observed for N-PAHs at 10 mg kg⁻¹ amendments over the first 30 days incubation, with the exception of 4,7-phenanthroline which recorded 0.19 ± 0.03 mg kg day⁻¹. The study showed that soil microflora have the potential to degrade N-PAHs since all of the aromatics recorded chemical losses under aerobic condition. However, degradation rates varied between chemicals and this was attributed to N-atom position and/or number of N-substituents. Further, relatively little or no biodegradation was observed in B[h]Q amended soils with increasing concentration; indicating that B[h]Q is more resistance to biodegradation in soil.

Biochar has great advantages and potentials on soil amendment and polluted soil remediation. In order to explore these applications, a pot experiment was carried out to research the effect of biochar on the heavy metal speciation in paddy soil and the heavy metal accumulation of paddy rice from Chengdu plain, Sichuan Province. The experimental results show that wine lees-derived biochar can efficiently increase soil pH, decrease the contents of soil exchangeable heavy metals, and promote heavy metal transformation to residual fraction. Moreover, application of biochar can reduce the accumulation of heavy metals in paddy plant, decrease the migration ability of heavy metals to the aboveground part of the plant, and consequently cut down contents of heavy metals in rice. When biochar dosage was 0.5 % in weight, the contents of soil exchangeable Cr, Ni, Cu, Pb, Zn, and Cd decreased 18.8, 29.6, 26.3, 23.0, 23.01, and 48.14 %, respectively, which all significantly differed from CK (P < 0.05), and the contents of heavy metals in plant roots, stems, leaves, rice husk, and rice all decreased accordingly, among which Zn, Cd, and Pb decreased 10.96, 8.89, and 8.33 % respectively. When biochar dosage increased to 1 %, heavy metal contents in roots, stems, leaves, rice husk, and rice decreased further. Therefore, wine lees-derived biochar shows a great potential in remediation of heavy-metal-polluted soil, and this work provides theoretical basis for restoring heavy-metal-polluted soil using biochar.