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Aegilops tauschii Coss. (2n = 2x = 14, DD) is a weed of wheat, competes for resources, performs better against different abiotic stresses, and is a rich genetic material source for wheat crop improvement programs. The effects of different drought stress levels on physiological and biochemical parameters and the expression profile of the drought resistance gene DRB were examined through greenhouse experiments. The physiological parameters (plant height, dry weight biomass, plant height, and leaf area-related parameters) fluctuated under different drought stress levels. Photosynthetic parameters (maximum (Fo’) and minimum (F’m) fluorescence, photochemical ((ΦPSII)), and non-photochemical quenching (qN)) were also affected by different drought stress levels, and their efficiency fluctuated with water availability. In the biochemical analysis, shallow significant changes occurred in peroxidase (POD), catalase (CAT), and proline content, while malondialdehyde (MDA) showed variation under different drought stress conditions. In the DREB gene expression analysis, eight populations showed high expression profiles compared to the control conditions in Ae. tauschii. The expression profiles in Ae. tauschii showed a high fold increase compared to the control condition, and DREB gene expression correlated with the changes in physiological and biochemical parameters.

Co-transport of biochar (BC) colloids with coexisting organic contaminants (OCs) in soil involves complex interactions among BC colloids, OCs, and soil particles, which is significant for the environmental application and risk assessment of BC and yet has not been well addressed. This study explored co-transports of three typical OCs (i.e., phenanthrene (PHN), atrazine (ATZ), and oxytetracycline (OTC)) and BC colloids obtained from bulk BCs with different charring temperatures (200–700 °C) and particle sizes (250 nm, 500 nm, and 1 μm) in a soil column of 9 cm in height. Considerable transport of BC colloids alone was observed and the maximum breakthrough concentration (C/Co) increased from 0.08 to 0.77 as the charring temperature decreased from 700 to 200 °C. The mobilities of PHN, OTC, and ATZ alone were very low but were greatly increased by co-transports with BC colloids, and their maximum C/Co values were within 0.05–0.33, 0.03–0.44, and 0.05–0.62, respectively, in the absence and presence of various BC colloids. The enhancement effect of BC colloids on the OC transport decreased with increasing charring temperature or particle size of BC colloids. BC colloids mainly acted as a vehicle to facilitate the transport of OCs, and dissolved organic carbon from BC colloids also contributed to the increased mobility of OCs in dissolved form. These findings provide new insights into co-transport of BC colloids and contaminants in soil.

With increased urbanization and industrialization, the global burden of anthropogenic emissions through biomass and fossil fuel combustion has increased significantly, threatening the global climate system, air quality and human health. Half of the aerosol particles emitted as a result of combustion are in the form of black carbon (BC), co-emitted with polycyclic aromatic hydrocarbons (PAHs). Due to strong sorption efficiency, BC act as a carrier for highly toxic and carcinogenic PAHs in air, water and soil, causing serious health issues. Scientific literature shows that the global burden of diseases has increased due to the high pollution levels of these pollutants in the environment. BC in association with PAHs can pose acute and chronic health problems such as respiratory problems, acute bronchitis, heart problems, lung cancer, aggravation of preexisting heart and lung disease, and asthma. In addition, most of the PAHs released into the environment, due to combustion activities, are categorized as type 2A or 2B human carcinogens by US EPA. In light of environmental significance of BC associated PAHs, this article stipulated a critical overview regarding the properties, pollution sources and worldwide pollution status of BC and associated PAHs along with the health risk these pollutants can pose.

Biochar (BC) colloids attract increasing interest due to their unique environmental behavior and potential risks. However, the interaction between BC colloids and organic contaminants that may affect their fates in the environment has not been substantially studied. Herein, adsorption and desorption of phenanthrene (PHN), atrazine (ATZ), and oxytetracycline (OTC) by a series of BC colloids derived from bulk rice straw BC samples with 6 pyrolysis temperatures (200–700 °C), and 3 particle sizes (250 nm, 500 nm, and 1 μm) were investigated. Regardless of pyrolysis temperature, BC colloids from a given sized bulk BC had a comparable size, being 30 ± 6, 70 ± 18, and 140 ± 15 nm corresponding to the three sized bulk BCs, respectively. The adsorption kinetics curves were well explained by the pseudo-second-order model, and pore diffusion was the primary rate-determining step. Both Freundlich and Langmuir models well fitted the adsorption isotherms. With increasing pyrolysis temperature or decreasing particle size of bulk BC, the specific surface area and pore volumes of the derived BC colloids increased, the kinetics model fitted adsorption rates (k2) of the three organics by the BC colloids all largely decreased, and the Langmuir model fitted adsorption capacities (Qmax) increased. The highest Qmax was obtained by BC colloids from the smallest (250 nm) bulk BC with the highest pyrolysis temperature (700 °C), being 212 μmol g−1 for PHN, 815 μmol g−1 for ATZ, and 72.4 μmol g−1 for OTC. The adsorption was reversible for PHN and ATZ, while significant desorption hysteresis was observed for OTC on BC colloids with middle pyrolysis temperatures (300–500 °C). The underlying mechanisms including hydrophobic interaction, π–π electron donor-acceptor interaction, molecular size effect, and irreversible reactions were discussed to explain the difference in the adsorption and desorption behaviors. The findings increased our understanding of the environmental fate and risk of BC.

Cadmium (Cd+2) is a highly toxic metal, which significantly alters different biochemical and metabolic processes in plants. Massive amounts of Cd+2 is being released into the environment by different anthropogenic activities. In the present study, plant growth promoting activities of bacterial strain Bacillus cereus was evaluated under Cd+2 stress in two rice cultivars Basmati-385 and Shaheen Basmati. Cd+2 stress significantly decreased plant growth and biomass production in both cultivars. However, with the inoculation of B. cereus under Cd+2 treatments, reduced Cd+2 uptake and increased antioxidant enzymes activities in rice cultivars lead to enhanced plant growth, biomass production, photosynthetic pigments, micronutrients, and lowered electrolytes leakage. This study suggests that B. cereus has the ability to alleviating Cd toxicity and increased phytoremediation efficiency of rice seedling under Cd stress.

Few studies have used biochar mixtures to remove potentially toxic elements from industrial wastewater. The present batch studies compare the adsorption of Cu 2 + , Cd 2 + , and Pb 2 + by single and mixed sorbents using rice husk feedstock (RH), rice husk biochar (RHB), ethylene-diamine-tetra-acetic acid-modified biochar (EDTA-RHB), and a mixture (MB) of these biosorbents. Metal sorption studies were carried out by varying the adsorbents, metal ion concentrations, contact time, and solution pH in a synthetic industrial wastewater. In all experiments, RHB, EDTA-RHB, and MB removed up to 98% of the metal ions within 60 min at pH 4. Kinetic studies showed that first- and second-order models gave the best fit for MB; whereas, the Freundlich model gave the best fit for the isotherm data. Results indicate that MB and EDTA-RHB treatments were more effective for adsorbing the studied heavy metals than RH or RHB. Such biosorbents could be useful in the treatment of co-existing potentially toxic elements from wastewater.

Pathways for the physical disintegration of biochar (BC) and the release of water dispersible BC colloids (WDBC) have received much attention due to their unique impacts on carbon loss and contaminant. However, the current understanding of the mechanisms involved in WDBC formation and associated influencing factors is rather limited. This study systematically explored the effects of pyrolysis temperature, initial particle size, and solution chemistry on WDBC formation in aqueous solutions and examined the formation and colloidal stability of WDBC in natural solutions. Results showed that pyrolysis temperature determined the abrasion resistance of pyrolyzed BC, and the submicron fragment rate decreased in the order 400 °C (BC400) > 700 °C (BC700) > 200 °C (BC200). The WDBC yield decreased in the order BC400 (77.5–331 mg g−1) > BC700 (33.5–173 mg g−1) > BC200 (16.8–125 mg g−1) depending on BC size at a solution ionic strength (IS) ≤ 1 mM, which was positively correlated with the submicron fragment rate of bulk BC. With the exception of BC200, increasing IS (0.1–20 mM) and decreasing pH (3.0–10.0) significantly inhibited WDBC yield. Release and sedimentation dominated the WDBC formation processes with the former being more susceptible to solution chemistry. Derjaguin-Landau-Verwey-Overbeek interactions properly explained the effect of IS on WDBC from BC400 and BC700, while the steric resistance of abundant dissolved organic carbon on BC200 was mainly responsible for the high formation of WDBC at high IS (20–50 mM). WDBC had high colloidal stability and could form and stabilize well in natural surface waters and soil solutions, suggesting the relevant risk of long-distance migration of WDBC in environments. These findings represent new knowledge regarding the physical decomposition and the fate of BC in the environment. Refereed/Peer-reviewed

Metals are released from biochar (BC) in either the free or dissolved organic carbon (DOC)-combined form. The complexation of metals with DOC influences their toxicity and bioavailability in the environment. The endogenous release of metal species with heterogeneous DOC from BC is very complex; this process has been neglected and remains unaddressed in the literature to date. In this study, the yield and chemical properties of labile DOC from BC were characterized, and the release of endogenous metal/metalloid elements (K, Mg, Mn, Fe, Al, Cu, and Si) and their species from BC with various pyrolysis temperatures and particle sizes were systematically investigated under various solution chemistries. The results showed that pyrolysis temperature of BC significantly influenced the yield and composition of DOC and DOC-metal/metalloid complexes, while particle size had lower impact. The yield of BC-derived DOC significantly decreased and the components gradually changed from low-molecular weight and low-aromaticity hydrophilic humic acid-like substances to complex high-molecular weight and high-aromaticity hydrophobic substances as pyrolysis temperature increased from 200 to 700 °C. The release of total dissolved metals decreased with increasing pyrolysis temperature, while the highest total dissolved Si was released from BC with the moderate pyrolysis temperature (500 °C). The metal elements were mainly released in the DOC-combined form, while the released Si was mainly in the free form in the neutral water environment. The release of DOC increased while that of dissolved metals decreased with increasing solution pH. The release of total dissolved metals/metalloids increased but the ratio of the DOC-combined metals/metalloids decreased with increasing solution ionic strength. These results provide new insight into the understanding of endogenous metal/metalloid release from BC in the natural environment.