Immobilization of microbes on biochar for water and soil remediation: A review.

Biochar has caught great attention over the last decade with the loose and porous structure, and carbon stability provides suitable living conditions for the growth and activity of microorganisms. This review provided a comprehensive summary of biochar immobilization microbe (BIM) in water and soil decontamination. Firstly, the bacterial immobilization techniques including adsorption, entrapping, and covalence methods were exhibited. Secondly, the applications of BIM in water and soil environmental remediation were introduced, mainly including the treatment of organic pollutants, heavy metals, and N/P, among which the most frequently immobilized microorganism was Bacillus. Then, the mechanisms of adsorption, redox, and degradation were analyzed. Finally, pertinent questions for future research of BIM technology were proposed. The purpose of this paper is to provide useful background information for the selection of better biochar fixation microorganisms for water and soil remediation.

Soil organic carbon and soil aggregate stability associated with aggregate fractions in a chronosequence of citrus orchards plantations.

Soil aggregates and their associated C may serve as accurate diagnostic markers for changes in soil characteristics in response to different agricultural management practices. However, there is limited knowledge regarding the effects of various chronosequences on soil organic C (SOC) pool in aggregates of different particle sizes in citrus plantations. Surface soil (0-20 cm) samples were collected from 120 citrus orchards (Yongxing County, Hunan Province, China) of different plantation ages (0-10y, 11-20y, and 21-30y). Plantation age dramatically affected the composition of soil aggregates of different particle sizes and their associated SOC, with the strongest macroaggregate fraction observed in the 0-10y orchards. Soil mean weight diameter (MWD) and geometric mean diameter (GMD) gradually decreased with plantation age (by 12.58% and 20.30% in 21-30y orchards, respectively). However, soil fractal dimension (D) and erodibility (K) gradually increased with plantation age (by 3.95% and 2.15% in 21-30y orchards, respectively). Furthermore, the SOC content and pool of aggregates and contribution of aggregates to SOC decreased with decreasing particle size. Multivariate analysis identified the aggregate fraction with a particle size over 2 mm as the main factor affecting the stability of soil aggregates in citrus plantations. The SOC content of aggregates was positively correlated with soil MWD and GMD but negatively correlated with soil D and K. The distribution of organic matter in soil aggregates can help us better understand the stability of soil structure and reduce the risk of soil erosion in successive citrus planting (<30y).

Electrochemical treatments of coking wastewater and coal gasification wastewater with Ti/Ti4O7 and Ti/RuO2-IrO2 anodes.

Electrochemical treatments of coking wastewater (CW) and coal gasification wastewater (CGW) were conducted with Ti/Ti4O7 and Ti/RuO2-IrO2 anodes. The performances of Ti/Ti4O7 and Ti/RuO2-IrO2 anodes were investigated by analyzing the effects of five key influencing factors including anodes material, current density, anode-cathode distance, initial pH value, and electrolyte type. The removal efficiencies of total organic carbon (TOC) were analyzed during the processes of CW and CGW electro-oxidation. The removal efficiencies of sixteen polynuclear aromatic hydrocarbons (PAHs) in CW and CGW by electro-oxidation were also explored to further assess the electrochemical activities of Ti/Ti4O7 and Ti/RuO2-IrO2 anodes. The Ti/Ti4O7 anode achieved 78.7% COD removal efficiency of CW, 85.8% COD removal efficiency of CGW, 50.3% TOC removal efficiency of CW, and 54.8% TOC removal efficiency of CGW, higher than the Ti/RuO2-IrO2 anode (76.7%, 78.1%, 44.8% and 46.8%). The COD removal efficiencies increased with the applied current density, decreased with the increase of the anode-cathode distance, and slightly decreased with the increase of the initial pH value. Meanwhile, the removal efficiencies of sixteen PAHs by the Ti/Ti4O7 anode were mostly higher than those by the Ti/RuO2-IrO2 anode. By comprehensively analyzing the performances of Ti/Ti4O7 and Ti/RuO2-IrO2 anodes on electrochemical treatments of CW and CGW, this study may supply insights into the application potentials of these anodes to the electrochemical treatments of real wastewater.

Residual behavior and risk assessment of butralin in peanut fields.

Butralin is widely used to control single-leaf weeds and some dicotyledons. The application of butralin in the environment may cause residue beyond regulation criteria and residual toxicity. Therefore, it is important to detect and supervise the dissipation behavior of butralin in edible raw food and in the environment. The aim of this study was to monitor butralin in peanuts and soil under farmland conditions and examine the likely dietary risk assessment of butralin for Chinese people on the basis of residual concentrations. A method for the analysis of butralin residue and its dissipation in peanut plants and soil under field conditions was investigated. The results show that an analytical method for the quantization of butralin in peanuts and soil utilizing gas chromatography with electron capture detection (GC-ECD) was developed. Standard recovery experiments using three different butralin spiking levels of 0.01, 0.1, and 1.0 mg kg-1 in different samples (i.e., peanut kernels, shell, seedling, stalk, and soil) were conducted. The recoveries of butralin from all matrices ranged from 86 to 108% with relative standard deviations from 3 to 6% (n = 5). The limit of quantification (LOQ) of the method was 0.01 mg kg-1. After storage at - 20 °C for 365 days, the degradation rate of residues of butralin in peanut kernels was less than 30%, which met the storage stability test criteria for pesticide residues in stored commodities of plant origin. The dissipation half-lives of butralin ranged from 4.2 to 6.6 days and 4.6 to 6.6 days in peanut seedlings and soil, respectively, in farmland ecosystems. At the normal harvest time, the final residue concentrations of butralin in peanuts and soil were all below the LOQ. The final total risk quotient (RQ) values were much lower than RQ = 100%, which indicated that the long-run fitness risk associated with butralin residue in different groups of registered crops is correspondingly low for people in China. The current research results could offer guidance for the rational use of butralin and provide data support for the building of maximum residue limits (MRLs) in China.

Factors controlling accumulation and bioavailability of selenium in paddy soils: A case study in Luxi County, China.

Selenium (Se) accumulation in rice (Oryza sativa L.) has become a major global concern. Se offers multiple health benefits in humans; however, its inadequate or excessive intake can be harmful. Therefore, determining the factors driving Se abundance and bioavailability in paddy soils is essential to ensure the safety of human Se intake. This study investigated the accumulation, bioavailability, and distribution of Se in 820 paddy soil and rice grain samples from Luxi County, China to assess how soil properties (soil organic matter [SOM], cation exchange capacity [CEC], and pH), geographical factors (parent materials, elevation, and mean annual precipitation [MAP] and temperature [MAT]), and essential micronutrients (copper [Cu], zinc [Zn], and manganese [Mn]) govern Se accumulation and bioavailability in paddy soils. Results showed that the average soil Se content was 0.36 mg kg-1, which was higher than that in China (0.29 mg kg-1). Alternatively, the average rice grain Se content was 0.032 mg kg-1, which was lower than the minimum allowable content in Se-rich rice grains (0.04 mg kg-1). Five studied parent materials all had a significant effect on soil Se content but had little effect on Se bioavailability (p < 0.05). CEC, elevation, and SOM, as well as the soil contents of Cu, Zn, and Mn were positively correlated with soil Se content, but pH, MAP, and MAT were negatively correlated. Correspondingly, Se bioavailability was negatively correlated with SOM and soil Zn content, but positively correlated with MAP and grain contents of Cu, Zn, and Mn. Furthermore, partial least squares path analysis revealed the interactive impacts of the influencing factors on Se accumulation and bioavailability in soils. On this basis, prediction models were established to predict Se accumulation and bioavailability in paddy soils, thereby providing theoretical support for developing efficient control measures to meet Se challenges in agriculture.

Spatial distribution and enrichment characteristics of selenium in paddy soil and rice around the Dongting Lake.

Selenium (Se) deficiency is a major global health issue. Given that the Dongting Lake region is a significant agricultural production area in China, its soil and geographical properties have a marked influence on Se accumulation in rice. Investigating these factors and their importance can provide technical guidance for the production of Se-rich rice locally and in other similar regions worldwide. Such studies can foster Se-enriched agricultural practices on a global scale, contributing to improved human health and environmental quality. Therefore, in this study, we investigated 15,403 paddy soil samples and their corresponding rice grains from the Dongting Lake area, by analyzing their Se content, spatial distribution, and bioaccumulation factor (BCF). The effects of parent materials, soil characteristics (physicochemical), and geographical factors on Se content in soil, rice grains, and BCF were also assessed. We found that the average Se content in the paddy soil of the Dongting Lake area was 0.43 mg/kg, which was 1.48 folds higher than the background Se content (0.29 mg/kg) in Chinese soil. The average Se content in rice grains was 0.059 mg/kg, surpassing the Chinese standard for Se-rich rice (0.04 mg/kg). Se distribution in the paddy soil and rice were the highest in the western and central regions and lowest in the eastern region. Se-enriched rice and Se-enriched rice fields are widely distributed in Dongting Lake area. Seven parent materials significantly influenced soil Se and BCF. Correlation analysis revealed positive correlations between soil Se and soil organic matter (SOM), zinc, altitude, and mean annual precipitation. BCF was positively correlated with pH and mean annual temperature. The Random Forest model highlighted that SOM played a pivotal role in soil Se enrichment, being the most influential factor for both soil and rice enrichment (RR type), whereas pH exerted the most significant influence on soil enrichment without rice enrichment (RN type).

Enhancement of Fenton processes at initial circumneutral pH for the degradation of norfloxacin with Fe@FeS core-shell nanowires.

The disadvantages of narrow working pH range (2.5-4.0), accumulation of iron sludge and incomplete degradation have hindered the practical application of the traditional homogeneous Fenton technique. In this research, Fe@FeS core-shell nanowires were synthesised and the innovative Fe@FeS/Fe2+/H2O2 system was adopted for norfloxacin (NOR) degradation at an initial circumneutral pH. More than 95% NOR has been removed in the Fe@FeS/Fe2+/H2O2 system within 30 min at pH 7. After investigating the concentration change of total iron, Fe2+ and H2O2 during the degradation process, NOR degradation in the Fe@FeS/Fe2+/H2O2 system might be attributed to the combined effect of homogeneous Fenton reaction and heterogeneous Fenton process. Besides that, the added Fe@FeS has accelerated Fe3+/Fe2+ redox cycle with extremely high degree. The generated reactive ●OH has been identified by electron paramagnetic resonance spectrometer results, possible degradation intermediates have also been proposed according to Gas chromatography-mass spectrometry analysis results. Moreover, Fe@FeS core-shell nanowires showed excellent reusability, it is a promising heterogeneous Fenton catalyst that is applicable for practical application.

Vinasse-based biochar magnetic composites: adsorptive removal of tetracycline in aqueous solutions.

Highly efficient and cost-effective adsorbents for antibiotic removal are the key to mitigate pollution by industrial wastewaters. Pyrolyzing low-cost winemaking waste into biochar is a promising means for waste biomass utilization. This study assembled vinasse-derived biochar with manganese ferrite into vinasse-manganese ferrite biochar-magnetic composites (V-MFB-MCs) through simultaneous pyrolysis of waste biomass and metal (Mn and Fe) hydroxide precipitates. Batch experiments were conducted to evaluate the kinetics and isotherms of tetracycline (TC) adsorption as well as the influence of pH value, humic acid, and ionic strength. Morphological characterization showed that crystalline MnFe2O4 nanoparticles were impregnated within the framework of fabricated V-MFB-MCs. Superior TC adsorption capacity and fast pseudo-second-order kinetics could be achieved by the V-MFB-MCs-800 at pH 3.0. The TC adsorption onto V-MFB-MCs-800 was highly pH-dependent and controlled by the positive influence of ionic strength and humic acid. V-MFB-MCs-800 showed excellent adsorption performance in different natural water. Multiple interaction mechanisms including pore filling effect, π-π stacking interaction, and hydrogen bonding contribute to TC removal by V-MFB-MCs-800, which can be an innovative biowaste-derived material for industrial wastewater treatment.

Co-application of biochar and organic fertilizer promotes the yield and quality of red pitaya (Hylocereus polyrhizus) by improving soil properties.

This study evaluated the combined impact of biochar and organic fertilizer on the soil properties, yield and quality of red pitaya (Hylocereus polyrhizus). A two-year (2019 and 2020) field experiment was conducted to study the effects of 3 rates of biochar (with carbon fertilizer ratios of 0%, 3%, and 6% w/w) combined with 3 levels of organic fertilizer (22.5, 45, and 90 t ha-1) on soil properties, along with red pitaya yield and quality. The results showed that soil pH, total organic carbon, available nutrients (N, P, and K), the yield and qualities (reduced sugar, soluble protein, and soluble solid) of red pitaya increased with the application of organic fertilizer compared with no application of biochar and organic fertilizer (CK treatment), but the combined application of biochar and organic fertilizer was more effective than their sole application. Furthermore, a medium dose of organic fertilizer combined with 3% biochar (C3F2 treatment) and a high dose of organic fertilizer combined with 3% biochar (C3F3 treatment) had the highest yields of red pitaya in 2019 and 2020. However, an application of 6% biochar with a low dose of organic fertilizer treatment (C6F1) had the highest profit in 2020, not the C3F3 treatment. The highest profits were observed in the C3F2 (71.0 × 103 RMB·t-1) and C6F1 (51.2 × 103 RMB·t-1) treatments. From the point of view of red pitaya yield and economic benefits, 3% biochar +45 t ha-1 organic fertilizer was the recommended combination that showed the best synergistic effect.