Pesticide adsorptivity of aged particulate matter arising from crop residue burns

Unveiling the Aftermath: Exploring Residue Profiles of Insecticides, Herbicides, and Fungicides in Rice Straw, Soils, and Air Post-Mixed Pesticide-Contaminated Biomass Burning

This study delved into the impact of open biomass burning on the distribution of pesticide and polycyclic aromatic hydrocarbon (PAH) residues across soil, rice straw, total suspended particulates (TSP), particulate matter with aerodynamic diameter ≤ 10 µm (PM10), and aerosols. A combination of herbicides atrazine (ATZ) and diuron (DIU), fungicide carbendazim (CBD), and insecticide chlorpyriphos (CPF) was applied to biomass before burning. Post-burning, the primary soil pesticide shifted from propyzamide (67.6%) to chlorpyriphos (94.8%). Raw straw biomass retained residues from all pesticide groups, with chlorpyriphos notably dominating (79.7%). Ash residue analysis unveiled significant alterations, with elevated concentrations of chlorpyriphos and terbuthylazine, alongside the emergence of atrazine-desethyl and triadimenol. Pre-burning TSP analysis identified 15 pesticides, with linuron as the primary compound (51.8%). Post-burning, all 21 pesticides were detected, showing significant increases in metobromuron, atrazine-desethyl, and cyanazine concentrations. PM10 composition mirrored TSP but exhibited additional compounds and heightened concentrations, particularly for atrazine, linuron, and cyanazine. Aerosol analysis post-burning indicated a substantial 39.2-fold increase in atrazine concentration, accompanied by the presence of sebuthylazine, formothion, and propyzamide. Carcinogenic PAHs exhibited noteworthy post-burning increases, contributing around 90.1 and 86.9% of all detected PAHs in TSP and PM10, respectively. These insights advance understanding of pesticide dynamics in burning processes, crucial for implementing sustainable agricultural practices and safeguarding environmental and human health.

Physicochemical Changes in Biomass Chars by Thermal Oxidation or Ambient Weathering and Their Impacts on Sorption of a Hydrophobic and a Cationic Compound

This study examined conditions that mimic oxidative processes of biomass chars during formation and weathering in the environment. A maple char prepared at the single heat treatment temperature of 500 °C for 2 h was exposed to different thermal oxidation conditions or accelerated oxidative aging conditions prior to sorption of naphthalene or the dication paraquat. Strong chemical oxidation (SCO) was included for comparison. Thermal oxidation caused micropore reaming, with ambient oxidation and SCO much less so. All oxidative treatments incorporated O, acidity, and cation exchange capacity (CEC). Thermal incorporation of O was a function of headspace O₂ concentration and reached a maximum at 350 °C due to the opposing process of burn-off. The CEC was linearly correlated with O/C, but the positive intercept together with nuclear magnetic resonance data signifies that, compared to O groups derived by anoxic pyrolysis, O acquired through oxidation by thermal or ambient routes contributes more to the CEC. Thermal oxidation increased the naphthalene sorption coefficient, the characteristic energy of sorption, and the uptake rate due to pore reaming. By contrast, ambient oxidation (and SCO) suppressed naphthalene sorption by creating a more hydrophilic surface. Paraquat sorption capacity was predicted by an equation that includes a CEC² term due to bidentate interaction with pairs of charges, predominating over monodentate interaction, plus a term for the capacity of naphthalene as a reference representing nonspecific driving forces.

The Role of Biochar in Regulating the Carbon, Phosphorus, and Nitrogen Cycles Exemplified by Soil Systems

Biochar is a carbon-rich material prepared from the pyrolysis of biomass under various conditions. Recently, biochar drew great attention due to its promising potential in climate change mitigation, soil amendment, and environmental control. Obviously, biochar can be a beneficial soil amendment in several ways including preventing nutrients loss due to leaching, increasing N and P mineralization, and enabling the microbial mediation of N2O and CO2 emissions. However, there are also conflicting reports on biochar effects, such as water logging and weathering induced change of surface properties that ultimately affects microbial growth and soil fertility. Despite the voluminous reports on soil and biochar properties, few studies have systematically addressed the effects of biochar on the sequestration of carbon, nitrogen, and phosphorus in soils. Information on microbially-mediated transformation of carbon (C), nitrogen (N), and phosphorus (P) species in the soil environment remains relatively uncertain. A systematic documentation of how biochar influences the fate and transport of carbon, phosphorus, and nitrogen in soil is crucial to promoting biochar applications toward environmental sustainability. This report first provides an overview on the adsorption of carbon, phosphorus, and nitrogen species on biochar, particularly in soil systems. Then, the biochar-mediated transformation of organic species, and the transport of carbon, nitrogen, and phosphorus in soil systems are discussed. This review also reports on the weathering process of biochar and implications in the soil environment. Lastly, the current knowledge gaps and priority research directions for the biochar-amended systems in the future are assessed. This review focuses on literatures published in the past decade (2009–2021) on the adsorption, degradation, transport, weathering, and transformation of C, N, and P species in soil systems with respect to biochar applications.

Degradation of sulfamethazine by biochar-supported bimetallic oxide/persulfate system in natural water: Performance and reaction mechanism

The rapid development of aquaculture results in the increased concentrations and kinds of antibiotics in water environment, and the sharply growing antibiotic contamination has caused increasing concerns. Herein, an innovative sulfamethazine (SMT) removal approach was developed by activation of persulfate (PS) using biochar-based materials prepared by co-precipitation and pyrolysis: Fe-Mg oxide/biochar (FeMgO/BC). Experiments on the activation of PS by FeMgO/BC under different factors were carried out. The involved mechanism and degradation pathway were also studied. Notably, the SMT removal rate reached 99 % under the optimum reaction condition, while the TOC removal efficiency reached 77.9 %. PS was activated by FeMgO/BC and the dominated active radical was SO_4•^-. Fe²⁺ from FeMgO and the hydroxyl and carboxyl groups on the surface of biochar contributed to the production of SO_4•^-. The dehydrogenation, bond cracking and unsaturated bond addition process occurred in the degradation of SMT. Furthermore, FeMgO/BC exhibits excellent reusability and stability. Considering the outstanding actual water application performances and the weak biotoxicity, FeMgO/BC shows a promising potential in the removal of antibiotics under actual water conditions.

Effect of ageing process on bisphenol A sorption and retention in agricultural soils amended with biochar

The ageing of biochar and organic pollutant itself in soils can both influence the retention of organic pollutant in field soils. In this study, column experiments were adopted to determine the effect of ageing process on bisphenol A (BPA) sorption and retention in two typical Chinese agricultural soils with lychee branch biochar added. The effect of biochar ageing on soil organic matter (SOM) was specially investigated. Experimental results showed that the addition of biochar significantly increased the condensation and rigid of SOM, which could further increase with biochar ageing in soils. As a result, the addition of biochar significantly increased BPA sorption capacity (5.86 times and 3.30 times) and retention rate (13.60 times and 4.47 times) in fluvo-aquic soil and phaeozem respectively, while BPA sorption capacity and retention rate decreased obviously after biochar ageing in the two soils for 2 months as compared with the freshly incorporated biochar treatments, which may be attributed to the surface coverage and/or pore blockage of some sorption sites owning to DOC. With biochar incorporated, 2 months of BPA ageing increased BPA retention rate by about 4.50 times in both soils as compared with BPA newly spiked treatments. The results of this study could provide important parameters for prediction and control of organic pollutants such as BPA in soils.

Organic waste from sugar mills as a potential soil ameliorant to minimise herbicide runoff to the Great Barrier Reef

We studied sorption potential for a range of herbicides using eleven waste materials (mill muds) containing organic matter (47.6 to 65.1%) produced by sugar mills and applied as soil conditioners by farmers. Sorption/desorption behaviour of five herbicides commonly used in sugarcane production (imazapic, atrazine, hexazinone, diuron and metribuzin) was studied on these mill muds, as is and after adding these to three soils at different rates (5-25%, dry weight basis). All mill muds had significant sorption capacity, especially for diuron, atrazine and metribuzin which was 6 to 26 times higher than the soil with 3.5% organic carbon (OC). Generally, sorption of the five herbicides assessed in all mill muds followed the order diuron > atrazine = metribuzin > hexazinone = imazapic. Eight out of 11 mill muds had similar sorption capacity for any given herbicides. Amending soils with selected mill muds significantly enhanced their sorption efficiency, depending on the rate of application especially in soil with low OC. Generally, application of mill muds at 5% w/w or 40 tons/ha increased sorption of studied herbicides by 2 to 10 folds. Soil amendment with mill muds also reduced the rate and extent of desorption of herbicides- especially mobile herbicides like metribuzin. Nearly 79% release of metribuzin was observed after three desorption steps in amended soil (at 5% w/w), whereas in unamended soil, 100% of metribuzin was released during first desorption step. The study demonstrates that wastes produced by sugar mills may have recycling use in enhancing the retention of mobile herbicides in soils with low OC content.

Effect of Biochar on Microbial Growth: A Metabolomics and Bacteriological Investigation in E. coli

Biochar has been proposed as a soil amendment in agricultural applications due to its advantageous adsorptive properties, high porosity, and low cost. These properties allow biochar to retain soil nutrients, yet the effects of biochar on bacterial growth remain poorly understood. To examine how biochar influences microbial metabolism, Escherichia coli was grown in a complex, well-defined media and treated with either biochar or activated carbon. The concentration of metabolites in the media were then quantified at several time points using NMR spectroscopy. Several metabolites were immediately adsorbed by the char, including l-asparagine, l-glutamine, and l-arginine. However, we find that biochar quantitatively adsorbs less of these metabolic precursors when compared to activated carbon. Electron microscopy reveals differences in surface morphology after cell culture, suggesting that Escherichia coli can form biofilms on the surfaces of the biochar. An examination of significant compounds in the tricarboxylic acid cycle and glycolysis reveals that treatment with biochar is less disruptive than activated carbon throughout metabolism. While both biochar and activated carbon slowed growth compared to untreated media, Escherichia coli in biochar-treated media grew more efficiently, as indicated by a longer logarithmic growth phase and a higher final cell density. This work suggests that biochar can serve as a beneficial soil amendment while minimizing the impact on bacterial viability. In addition, the experiments identify a mechanism for biochar's effectiveness in soil conditioning and reveal how biochar can alter specific bacterial metabolic pathways.

Sorption, bioavailability and ecotoxic effects of hydrophobic organic compounds in biochar amended soils

This work addresses the effect of biochar amendment to soil on contaminant sorption, bioavailability, and ecotoxicity. A distinction between positive primary amendment effects caused by reduced toxicity resulting from contaminant sorption, and negative secondary amendment effects of the biochars themselves was seen. Two biochars (one from high technology and one from low technology production processes) representing real world biochars were tested for the adsorption of pyrene, polychlorinated biphenyl (PCB) 52), and dichlorodiphenyldichloroethylene (p,p'-DDE). Sorption by both biochars was similar, both for compounds in single and mixed isotherms, in the presence and absence of soil. p,p'-DDE natively contaminated and spiked soils were amended with biochar (0, 1, 5, and 10%) and bioavailability, operationally defined bioaccessibility and ecotoxicity were assessed using polyethylene (PE), polymeric resin (XAD) and Folsomia candida, respectively. At the highest biochar dose (10%), bioavailability and bioaccessibility decreased by >37% and >41%, respectively, compared to unamended soils. Mortality of F. candida was not observed at any biochar dose, while reproductive effects were dose dependent. F. candida benefited from the reduction of p,p'-DDE bioavailability upon 1% and 5% biochar addition to contaminated soils while at 10% dose, these positive effects were nullified by biochar-induced toxicity. p,p'-DDE toxicity corrected for such secondary effects was predicted well by both PE uptake and XAD extraction.

Evaluation of biochars in reducing the bioavailability of flubendiamide in water/sediment using passive sampling with polyoxymethylene

An equilibrium passive sampler based on POM was first used to determine the C_free of flubendiamide in water/sediment systems. The adsorption of flubendiamide by POM followed a first-order one-compartment uptake model and the POM-water partition coefficient was 1.90. The method was used to compare the efficiency of three biochars which were produced from crofton weed (BC-1, ∼500°C), macadamia (BC-2, 550-660°C) and wheat straw (BC-3, 550°C). The Freundlich fit the sorption isotherm data well and the adsorption capacity was BC-1>BC-3>BC-2. The percent removal of the BC-1 was higher in acidic solutions. When different doses of BC-1 were added to two sediments, the C_free of the flubendiamide was higher in the sediment with a low organic matter content (S-1). With an increase of BC-1, the C_free was significantly reduced in S-1. A 30-day period of biochar-sediment contact time was sufficient for a reduction of freely dissolved flubendiamide in the case of the two sediments tested. In the combination of biochar addition (5%) and aging time (30days), the maximum reductions were 87% and 60% in S-1 and S-2. Therefore, the reduction of bioavailability of the flubendiamide and pollution repair can be achieved by this process.

Effects of chemical oxidation on phenanthrene sorption by grass- and manure-derived biochars

The oxidation of biochar in the natural environment has been widely observed. However, its influence on the sorption of hydrophobic organic compounds (HOCs) by biochars, especially biochars with high contents of minerals, remains poorly understood. In this study, sorption of phenanthrene (PHE) by grass straw-based biochars (GRABs) and animal waste-based biochars (ANIBs) produced at 450°C before and after oxidation with HNO₃ was investigated. The biochar samples were characterized using elemental analysis, X-ray photoelectron spectroscopy, ¹³C nuclear magnetic resonance, and CO₂ adsorption. Characterization results demonstrate that HNO₃ treatment of biochars caused O enrichment, loss of alkyl C, and rise of aromaticity. The organic C-normalized surface area (CO₂-SA/OC) of both GRABs and ANIBs generally increased after oxidation. The sorption nonlinearity of PHE by the biochars was weakened after HNO₃ treatment. The sorption capacity of PHE by oxidized GRABs was consistently elevated compared with the untreated samples, indicating that the high sorption capacity of PHE by GRABs may be maintained for a long time after being added into soils. By contrast, PHE sorption by ANIBs was unchanged or attenuated after oxidation. Polar groups facilitated the sorption of PHE by GRABs, while inhibited that by ANIBs. Pore-filling and π-π electron donor-acceptor interactions regulated PHE sorption by GRABs. Our results imply that GRABs are promising sorbents for environmental applications in view of their long-lasting sorption capacity.

Effect of rice-straw biochar on selective biodegradation of nonylphenols in isomer specificity

In a previous study, we found that rice-straw biochar degraded and removed hydrophobic organic contaminants (HOCs) through coupled adsorption-biodegradation. However, few studies have determined whether biochar affects HOC isomer degradation and isomer-selective biodegradation or whether biochar can alter HOC isomer features, resulting in changes to HOC isomer residues in water environments. In this study, the effects of biochar at two dosages (0.001 and 0.01 g) on the biodegradation of ten isomers of a typical xenoestrogen of nonylphenol (NP) were evaluated. The results revealed that there were no effects of biochar on the adsorption of NP isomers. However, biochar addition affected the biodegradation of a specific isomer without altering the features of the NP isomers. The treatment of NP isomers with Pseudoxanthomonas sp. yielded degradation ratios ranging from 60.7 to 100%. At 0.001 g biochar treatment, the degradation of eight NP isomers was enhanced (except for NP₁₉₄ and NP_193a+b) due to their bulky structures. The degradation of the ten NP isomers was inhibited when 0.01 g biochar was added. These findings characterized the effects of biochar on NP isomer contaminants and provided basic information for the application of biochar for the remediation of NP isomer contaminants.

Effects of aging process on adsorption-desorption and bioavailability of fomesafen in an agricultural soil amended with rice hull biochar

Biochar has been introduced as an acceptable soil amendment due to its environmental benefits such as sequestering soil contaminants. However, the aging process in biochar amended soil probably decreases the adsorption capacity of biochar through changing its physico-chemical properties. Adsorption, leaching and bioavailability of fomesafen to corn in a Chinese soil amended by rice hull biochar after 0, 30, 90 and 180days were investigated. Results showed that the addition of 0.5%-2% fresh biochar significantly increases the adsorption of fomesafen 4-26 times compare to unamended soil due to higher SSA of biochar. Biochar amendment also decreases fomesafen concentration in soil pore water by 5%-23% resulting lower risk of the herbicide for cultivated plants. However, the aging process decreased the adsorption capacity of biochar since the adsorption coefficient values which was 1.9-12.4 in 0.5%-2% fresh biochar amended soil, declined to 1.36-4.16, 1.13-2.78 and 0.95-2.31 in 1, 3 and 6-month aged treatments, respectively. Consequently, higher desorption, leaching and bioavailable fraction of fomesafen belonged to 6-month aged treatment. Nevertheless, rice hull biochar was effective for sequestering fomesafen as the adsorption capacity of biochar amended soil after 6months of aging was still 2.5-5 times higher compared to that of unamended soil.

Characterization and Phenanthrene Sorption of Natural and Pyrogenic Organic Matter Fractions

Pyrogenic humic acid (HA) is released into the environment during the large-scale application of biochar. However, the biogeochemistry of pyrogenic organic matter (PyOM) fractions and their sorption of hydrophobic organic compounds (HOCs) are poorly understood in comparison with natural organic matter (NOM) fractions. HA and humin (HM) fractions isolated from soils and the oxidized biochars were characterized. Sorption of phenanthrene (PHE) by these fractions was also examined. The characterization results demonstrate that pyrogenic HAs are different from natural HAs, with the former having lower atomic H/C ratios, more abundant aromatic C, and higher concentrations of surface carboxylic groups. Compared with the fresh biochars, the K_oc of PHE on their oxidized biochars, pyrogenic HA, and HM fractions were undiminished, which is encouraging for the use of biochar in soil remediation. The PyOM fractions exhibited stronger nonlinear sorption than the NOM fractions. In addition, the PyOM fractions had higher sorption capacity than the NOM fractions due to their low polar C content and high aryl C content. The results obtained from this work will shed new light on the impact of the addition of biochar on the biogeochemistry of soil organic matter and on the fate of HOCs in biochar-amended soil.

Bioavailability assessment of thiacloprid in soil as affected by biochar

Biochars can significantly sorb pesticides, and reduce their bioavailability in agricultural soils. In this study, the effects of a type of biochar (BC500) on the sorption, degradation, bioaccumulation and bioavailability of thiacloprid, which is a commonly used insecticide, were investigated. The thiacloprid sorption constant (K_f values) increased by 14 times after 2% BC500 application, and the degradation of the insecticide decreased with increasing amounts of the biochars in the soil. Coupled with the exhaustive extraction and single-point Tenax method, the bioavailability of thiacloprid was predicted in the presence of the biochar. In soils amended with BC500, the thiacloprid concentrations accumulated in Tenax correlated well with those observed in earthworms (R² = 0.887), whereas the concentrations extracted by exhaustive method followed a less significant relationship with those in earthworms (R² = 0.624). The results of Tenax extractions and earthworm bioassays indicate that biochar reduces the bioavailability of thiacloprid in soil, but the delayed degradation and increased earthworm accumulation in aged biochar-amended soil imply that the environmental risks of biochar application to earthworms remain.

Effect of Biochar Amendment and Ageing on Adsorption and Degradation of Two Herbicides

Biochar amendment can alter soil properties, for instance, the ability to adsorb and degrade different chemicals. However, ageing of the biochar, due to processes occurring in the soil over time, can influence such biochar-mediated effects. This study examined how biochar affected adsorption and degradation of two herbicides, glyphosate (N-(phosphonomethyl)-glycine) and diuron (3-(3,4-dichlorophenyl)-1,1-dimethylurea) in soil and how these effects were modulated by ageing of the biochar. One sandy and one clayey soil that had been freshly amended with a wood-based biochar (0, 1, 10, 20 and 30% w/w) were studied. An ageing experiment, in which the soil-biochar mixtures were aged for 3.5 months in the laboratory, was also performed. Adsorption and degradation were studied in these soil and soil-biochar mixtures, and compared to results from a soil historically enriched with charcoal. Biochar amendment increased the pH in both soils and increased the water-holding capacity of the sandy soil. Adsorption of diuron was enhanced by biochar amendment in both soils, while glyphosate adsorption was decreased in the sandy soil. Ageing of soil-biochar mixtures decreased adsorption of both herbicides in comparison with freshly biochar-amended soil. Herbicide degradation rates were not consistently affected by biochar amendment or ageing in any of the soils. However, glyphosate half-lives correlated with the Freundlich Kf values in the clayey soil, indicating that degradation was limited by availability there.

Variability of glyphosate and diuron sorption capacities of ditch beds determined using new indicator-based methods

Pesticide sorption to ditch-bed materials can efficiently decrease pesticide concentrations in the flowing water. Pesticide sorption depends on flood characteristics and the nature and abundance of ditch-bed materials, such as soils, living and decaying vegetation and ash. However, the affinities of pesticides for various ditch-bed materials have rarely been investigated, and variations in the global sorption capacity of ditch beds resulting from their heterogeneous compositions and variable flood characteristics have not been determined. Thus, we studied the variability of sorption capacities of ditch-bed materials for glyphosate and diuron in three catchments in France and propose a method for calculating global sorption processes in heterogeneous ditch beds. The methodology consists in estimating a global sorption coefficient for the composite ditch-bed materials (Kdditch) and an indicator of the amount of pesticide potentially retained by sorption during a flood event (SPRI). Furthermore, we computed the Kdditch and SPRI of glyphosate and diuron for 8 ditches subjected to 3h flood events with water levels varying from 0.5 to 15cm. Our results show that increasing the water level from 0.5 to 15cm resulted in a 90% decrease in the sorption capacities of the ditch beds for both pesticides. At a medium water depth of 5cm, SPRI varied from 25 to 51% and from 7 to 35% among the ditches for glyphosate and diuron, respectively. The variabilities of the glyphosate and diuron sorption capacities among the ditches were mainly driven by the nature and abundance of soil and ash. As the management of farm ditches, performed to maintain their hydraulic performance, modifies the abundances of various ditch-bed materials, it constitutes a potential lever of action for water quality improvement. Thus, Kdditch and SPRI could serve as rapid and cost-effective tools for optimizing ditch network management strategies to improve water quality in cropped catchments.

Bioavailability and bioaccessibility of polycyclic aromatic hydrocarbons (PAHs) in historically contaminated soils after lab incubation with sewage sludge-derived biochars

The objective of this study was to estimate the effectiveness of application of sewage sludge-derived biochars for the immobilisation of freely dissolved (Cfree) and bioaccessible (Cbioacc) polycyclic aromatic hydrocarbons (PAHs) in contaminated soils. Soil SL-COK collected from the area of a coking plant and soil SL-BIT collected from the area of a plant producing bituminous materials were chosen for the study. The biochars were produced from sewage sludge at temperatures of 500 °C (BC500) or 700 °C (BC700). The biochars were mixed with the soil at the dose of 5% and incubated for a period of 60 d. The content of PAHs was determined with the use of polyoxymethylene (POM) (Cfree) or a solution of cyclodextrins and silicon rod elastomer (Cbioacc). Biochars reduced the content of Cfree and Cbioacc PAHs in soils. A higher level of reduction was noted for Cfree PAHs than for Cbioacc PAHs. Biochar produced at 700 °C was more effective in the reduction of Cfree and Cbioacc PAHs than biochar produced at 500 °C. It was found that in the soil in which the source of contamination were processes related with the production of bituminous materials (SL-BIT), the effect of reduction of Cfree and Cbioacc was greater than in soil SL-COK where the source of PAHs were coking processes. It also needs to be emphasised that soil SL-BIT, for which better reduction of PAHs was noted, was also characterised by a lower affinity towards those compounds than soil SL-COK.

Attenuation of phenanthrene and pyrene adsorption by sewage sludge-derived biochar in biochar-amended soils

The aim of this study was to evaluate the effect of soils on the sorption of phenanthrene (PHE) and pyrene (PYR) by sewage sludge-derived biochars (SS-derived biochars). The SS-derived biochars were added to soils with varying properties as well as with a different degree and source of polycyclic aromatic hydrocarbons (PAHs) contamination. The biochars (BCs) were produced from sewage sludge during pyrolysis at temperatures of 500 °C (BC500) and 700 °C (BC700). The addition of biochars to the soils (5 %, w/w) increased the sorption of PHE from 8.3 to 20.3 % and PYR from 14.5 to 31.7 % by amended soil. BC700 biochar was characterized by better sorption capacity than BC500 biochar. Nevertheless, the presence of soil reduces the effectiveness of biochars in binding the compounds studied. The sorption capacity of the biochars decreased several times after they had been mixed with the soil compared to pure biochars. The study found dissolved organic carbon (DOC) and clay minerals present in the soils to have a significant effect on reducing the efficiency of PHE and PYR sorption by biochar. A greater impact of fouling was observed in the case of BC500 biochar characterized by lower porosity than BC700 biochar.

Efficacy of carbonaceous nanocomposites for sorbing ionizable antibiotic sulfamethazine from aqueous solution

This paper investigated the key factors and mechanisms of sulfamethazine (SMT) sorption on a novel carbonaceous nanocomposite, and the effects of harsh aging on SMT sorption in the presence and absence of soil and before as well as after aging. The carbonaceous nanocomposites were synthesized by dip-coating straw biomass in carboxyl functionalized multi-walled carbon nanotubes solution and then pyrolyzed at 300 °C and 600 °C in the absence of air. The sorption performance of high temperature carbonaceous nanocomposite on SMT was excellent, as measured sorption distribution coefficient in the order of 10(3)-10(5.5) L kg(-1). Carbonaceous nanocomposites were aged either alone or mixed with soil via exposure to nutrients and soil extract (biological aging) or 80 °C for 100 d (chemical aging). No obvious effects of harsh aging on SMT sorption were observed in the presence of soil and/or biological and chemical aging. The primary mechanisms for SMT sorption included partition caused by Van der Waals forces and adsorption caused by hydrogen bonding and π-π electron-donor-acceptor interaction. Comprehensively considering the cost, renewability, and the application to real water samples, the carbonaceous nanocomposites have potential in removal of SMT and possibly other persistent organic pollutants from wastewater.

Metolachlor Sorption and Degradation in Soil Amended with Fresh and Aged Biochars

Addition of organic amendments such as biochar to soils can influence pesticide sorption-desorption processes and, in turn, the amount of pesticide readily availability for transport and biodegradation. Sorption-desorption processes are affected by both the physical and chemical properties of soils and pesticides, as well as soil-pesticide contact time, or aging. Changes in sorption-desorption of metolachlor with aging in soil amended with three macadamia nut shell biochars aged 0 (BCmac-fr), 1 year (BCmac-1yr), and 2 years (BCmac-2yr) and two wood biochars aged 0 (BCwood-fr) and 5 years (BCwood-5yr) were determined. Apparent sorption coefficient (Kd-app) values increased with incubation time to a greater extent in amended soil as compared to unamended soils; Kd-app increased by 1.2-fold for the unamended soil, 2.0-fold for BCwood-fr, 1.4-fold for BCwood-5yr, 2.4-fold for BCmac-fr, 2.5-fold for BCmac-1yr, and 1.9-fold for BCmac-4yr. The increase in calculated Kd-app value was the result of a 15% decrease in the metolachlor solution concentration extractable with CaCl2 solution with incubation time in soil as compared to a 50% decrease in amended soil with very little change in the sorbed concentration. Differences could possibly be due to diffusion to less accessible or stronger binding sites with time, a faster rate of degradation (in solution and on labile sites) than desorption, or a combination of the two in the amended soils. These data show that transport models would overpredict the depth of movement of metolachlor in soil if effects of aging or biochar amendments are not considered.

Suppression of Chlorantraniliprole Sorption on Biochar in Soil-Biochar Systems

The sorption behavior of chlorantraniliprole (CAP) by biochar and effect of soil extracts on sorptivity in soil-biochar systems were examined. The results showed that biochar amendment could enhance the sorption of CAP in soils. The values of K F increased significantly when the soils were amended with 0.5 % BC850, which were from 1.54 to 196.5. The indigenous sorptivity of biochar was suppressed after it was applied to the soils. The degree of biochar sorptivity attenuation in different soil-biochar systems varied with the properties of soil water soluble matters. Sorption of CAP by biochar from the five soil extracts was found to be lower than that from a CaCl2 solution. The calculated K d values at C w of 0.01 mg kg(-1) for biochar sorption of CAP from CaCl2 solution were 21.4-26.6 times of that from soil extracts. Aging of biochar in soil extract reduced CAP sorption by up to 85 %.

Effect of pyrochar and hydrochar amendments on the mineralization of the herbicide isoproturon in an agricultural soil

Carbon (C)-rich, solid products from pyrolysis (pyrochars) and hydrothermal carbonization (HTC, hydrochars) are expected to reduce the bioavailability and bioaccessibility of pesticides as side effect of soil addition. To compare effects of different feedstocks (digestate, miscanthus, woodchips) and production processes (pyrolysis at 750°C, HTC at 200°C and 250°C), (14)C-labeled isoproturon (IPU) was applied at 0.75 kg ha(-)(1) to loamy sand amended either with 0.5% or 5% pyrochars or hydrochars, which was then incubated for 50d. Mineralization of IPU was measured as (14)C-CO2 released from soil-char composites. Pore-water and methanol extractable (14)C-IPU was quantified as well as non-extractable (14)C-residues (NER). Furthermore, C mineralization of pyrochars, hydrochars and feedstocks was studied to assess the relationship between IPU bioaccessibility and char decomposability. In pure soil, 8.1% of applied IPU was mineralized after 50d. This was reduced more strongly in pyrochar treatments (81 ± 6% reduction) than in hydrochar treatments (56 ± 25% reduction). Different feedstocks had no significantly different effect when 5% char was added, but their effect was significant and dependent on the production process in 0.5% amendments. Pesticide binding can occur by surface sorption as well as by diffusion and subsequent occlusion in micropores. The latter can be expected to result in high amounts of NER, as it was observed in the pyrochar treatments. Hydrochars were less stable than pyrochars and contained lower amounts of NER. Thus, in hydrochar amended soils, better accessibility of IPU to microbial degradation may be a result of full char decomposition within decades ensuring controlled pesticide degradation.

Physico-chemical characterization and source tracking of black carbon at a suburban site in Beijing

Particles from ambient air and combustion sources including vehicle emission, coal combustion and biomass burning were collected and chemically pretreated with the purpose of obtaining isolated BC (black carbon) samples. TEM (transmission electron microscopy) results indicate that BC from combustion sources shows various patterns, and airborne BC appears spherical and about 50 nm in diameter with a homogeneous surface and turbostratic structure. The BET (Barrett-Emmett-Teller) results suggest that the surface areas of these BC particles fall in the range of 3-23 m2/g, with a total pore volume of 0.03-0.05 cm3/g and a mean pore diameter of 7-53 nm. The nitrogen adsorption-desorption isotherms are indicative of the accumulation mode and uniform pore size. O2-TPO (temperature programmed oxidation) profiles suggest that the airborne BC oxidation could be classified as the oxidation of amorphous carbon, which falls in the range of 406-490°C with peaks at 418, 423 and 475°C, respectively. Generally, the BC characteristics and source analysis suggest that airborne BC most likely comes from diesel vehicle emission at this site.

Role of Alumina and Montmorillonite in Changing the Sorption of Herbicides to Biochars

The influence of biochars on the fate of herbicides in soil depends mostly on environmental factors among which the role of soil minerals is not clear. Two wood-derived biochars produced at 400 °C (BC400) and 600 °C (BC600) were treated with alumina and montmorillonite to investigate their interaction with biochars and the influence of herbicide sorption. Both minerals exhibited a pore-expanding effect that was likely relative to the removal of authigenic organic matter away from the biochars' surface. Alumina brought more remarkable pore expansion by doubling the surface area of the BC400 biochar and the mesopore area of the BC600 biochar. Consequently, more adsorption sites were accessible for herbicide molecules, which resulted in higher sorption of herbicides (acetochlor and metribuzin) to the mineral-treated biochars than to the untreated biochars. The results are useful for understanding the change of surface and sorption properties of biochars with soil applications.

Biochar and activated carbon for enhanced trace organic contaminant retention in stormwater infiltration systems

To assess the effectiveness of biochar and activated carbon (AC) for enhanced trace organic contaminant (TOrC) retention in stormwater infiltration systems, an approach combining forward-prediction modeling and laboratory verification experiments was employed. Batch and column tests were conducted using representative TOrCs and synthetic stormwater. Based on batch screening tests, two commercially available biochars (BN-biochar and MCG-biochar) and an AC were investigated. The AC exhibited the strongest sorption, followed by MCG-biochar and BN-biochar. Langmuir isotherms provided better fits to equilibrium data than Freundlich isotherms. Due to superior sorption kinetics, 0.2 wt % MCG-biochar in saturated sand columns retained TOrCs more effectively than 1.0 wt % BN-biochar. A forward-prediction intraparticle diffusion model based on the Langmuir isotherm adequately predicted column results when calibrated using only batch parameters, as indicated by a Monte Carlo uncertainty analysis. Case study simulations estimated that an infiltration basin amended with F300-AC or MCG-biochar could obtain sorption-retarded breakthrough times for atrazine of 54 or 5.8 years, respectively, at a 1 in./h infiltration rate. These results indicate that biochars or ACs with superior sorption capacity and kinetics can enhance TOrC retention in infiltration systems, and performance under various conditions can be predicted using results from batch tests.

Natural oxidation of a temperature series of biochars: opposite effect on the sorption of aromatic cationic herbicides

The natural oxidation of biochar in the environment has been widely observed. However, its influence on the sorption of organic contaminants remains poorly understood. In the present study, a series of wood-based biochars prepared between 300 and 600°C (referred to as BC300-BC600) was abiotically incubated for one year to examine the aging effect of the temperature series of biochars on their sorption of aromatic cationic herbicides (ACHs, paraquat and diquat) as well as a nonpolar reference adsorbate (naphthalene). One year of oxidation showed no obvious effect on the surface area, but distinct increases in the O/C elemental ratio, density of the surface groups and cation exchange capacity (CEC) were observed. Therefore, these properties were significantly affected by the charring temperature. After incubation, high-temperature biochars (BC500 and BC600) displayed a 14.1-36.3% decrease in the sorption (qm) of ACHs. The alteration of their sorption tendency was similar to the reduced sorption of naphthalene on oxidized biochars, in which the increased surface groups lowered the surface area accessible to adsorbates because of blockage by adsorbed water molecule clusters. Conversely, a pronounced increase of ACHs sorption by 121.7-201.1% on the low-temperature biochar (BC300) was observed, presumably due to the increase of CEC values after oxidation. This result was further demonstrated by a significant linear relationship between the paraquat sorption (qm) and CEC values (R(2)=0.9895) of oxidized biochars. Interestingly, one year of oxidation simultaneously resulted in an enhanced sorption of paraquat and a reduced sorption of diquat on BC400, which indicated that the oxidation-induced sorption change of ACHs is a complex function of changes in the surface properties of the biochars as well as the molecular structure of the solute.

Influence of soil biochar aging on sorption of the herbicides MCPA, nicosulfuron, terbuthylazine, indaziflam, and fluoroethyldiaminotriazine

Sorption of four herbicides and a metabolite of indaziflam on a fresh macadamia nut biochar and biochars aged one or two years in soil was characterized. On fresh biochar, the sorption was terbuthylazine (Kd = 595) > indaziflam (Kd = 162) > MCPA (Kd = 7.5) > fluoroethyldiaminotriazine (Kd = 0.26) and nicosulfuron (Kd = 0). Biochar surface area increased with aging attributed to the loss of a surface film. This was also manifested in a decline in water extractable organic carbon with aging. Correspondingly, an increase in the aromaticity was observed. The higher surface area and porosity in aged biochar increased sorption of indaziflam (KdBC-2yr = 237) and fluoroethyldiaminotriazine (KdBC-1yr = 1.2 and KdBC-2yr = 3.0), but interestingly decreased sorption of terbuthylazine (KdBC-1yr = 312 and KdBC-2yr = 221) and MCPA (KdBC-1yr = 2 and KdBC-2yr = 2). These results will facilitate development of biochars for specific remediation purposes.

Biochar: an effective amendment for remediating contaminated soil

Biochar is a carbon-rich material derived from incomplete combustion of biomass.Applying biochar as an amendment to treat contaminated soils is receiving increasing attention, and is a promising way to improve soil quality. Heavy metals are persistent and are not environmentally biodegradable. However, they can be stabilized in soil by adding biochar. Moreover, biochar is considered to be a predominant sorptive agent for organic pollutants, having a removal efficiency of about 1 order of magnitude higher than does soil/sediment organic matter or their precursor substances alone.When trying to stabilize organic and inorganic pollutants in soil, several features of biochar' s sorption capacity should be considered, viz., the nature of the pollutants to be remediated, how the biochar is prepared, and the complexity of the soil systemin which biochar may be used. In addition, a significant portion of the biochar or some of its components that are used to remediate soils do change over time through abiotic oxidation and microbial decomposition. This change process is commonly referred to as "aging:" Biochar "aging" in nature is inevitable, and aged biochar exhibits an effect that is totally different than non-aged biochar on stabilizing heavy metals and organic contaminants in soils.Studies that have been performed to date on the use of biochar to remediate contaminated soil are insufficient to allow its use for wide-scale field application.Therefore, considerable new data are necessary to expand both our understanding of how biochar performs in the field, and where it can be best used in the future for soil remediation. For example, how biochar and soil biota (microbial and faunal communities)interact in soils is still poorly understood. Moreover, studies are needed on how to best remove new species of heavy metals, and on how biochar aging affects sorption capacity are also needed.

Enhanced irreversible sorption of carbaryl to soils amended with crop-residue-derived biochar

The irreversible sorption-desorption of carbaryl in five soil types with crop-residue-derived biochar (CBC) amendment was determined. CBC has lower surface area and micropores volume than wood-based biochar and charcoal. However, CBC amendment (0.5%) still significantly enhanced the hysteresis effect on soils, with a 1.7- to 2.8-fold increase in the hysteresis index (HI) values. The HI values increased exponentially with the increased amount of CBC but decreased exponentially with the increased amount of soil organic matter (SOM%). Furthermore, the irreversible carbaryl sorption (qirr) and the irreversibility index (Iirr) values were proportional to the amount of CBC (0-1.0%) in soils. Likewise, the SOM-rich soil (S3) was washed ten times to reduce its SOM% to evaluate the influence of the dissolved organic matter (DOM) in the soils on the irreversible sorption. The Iirr values of the unamended S3 increased as the number of sorption-desorption cycles increased, whereas those of the 1.0% CBC-amended S3 decreased. In addition, the Iirr values of the unwashed S3 were lower than those of the washed S3. By contrast, the Iirr values of the 1.0% CBC-amended S3 soil were higher in the unwashed samples than in the washed samples. These results suggested that DOM had opposite effects on the irreversible carbaryl sorption by unamended and CBC-amended soils. The DOM release may expose more irreversible adsorption sites in the soils and may cover the surface of the CBC to form a desorption-resistant fraction in its mesopore or macropore regions, thereby preventing the desorption of adsorbed carbaryl molecules.

Predicting contaminant adsorption in black carbon (biochar)-amended soil for the veterinary antimicrobial sulfamethazine

Commercial hardwood biochars ranging in N2 specific surface area of 0.1-427 m(2) · g(-1) were added to an agricultural soil at 0, 1, or 2% levels to determine whether they would predictably reduce the pore water concentration of sulfamethazine (SMT). The soil and biochar-soil mixtures were preweathered under mild (2 d, 20 °C) or more severe (28 d, 40 °C) conditions before spiking. The carbon-normalized biochar-water distribution coefficient (KBC) of the biochars varied by a factor of up to 10(4), depending on biochar properties and SMT concentration. Except for the fast-pyrolysis biochar, KBC greatly exceeded the soil organic carbon-water distribution coefficient KOC. Sorption in the mixtures increased as expected with biochar and dose. However, sorption was dramatically overpredicted (by up to 10(2.5)) by the sum of sorption to the individual components, indicating a strong weathering effect even under the mild conditions. The soil-subtracted weathered biochar-water isotherms were more linear, and the KBC values approached or lay within the range of KOC values reported for SMT in 19 soils. Biochars both in intimate contact with soil and placed in a membrane bag suspended in the solution showed reduced N2-B.E.T. surface area after weathering, implicating fouling of the biochar surface by humic substances transferred through water. The results indicate that only highly surfaceous, carbonaceous biochars would be useful for stabilizing soil contaminated with compounds such as SMT. They also suggest that weathering may attenuate the contribution of native (environmental) black carbon to sorption of such compounds in soils and sediments.

Impacts of biochar on bioavailability of the fungicide azoxystrobin: a comparison of the effect on biodegradation rate and toxicity to the fungal community

There is great interest in using biochar (BC) as a soil amendment to provide a long-term repository of carbon to mitigate climate change. BC can have major impacts on soil biogeochemical cycling processes, largely by the sorption and protection of organic matter from microbial turnover. Application of BC to agricultural soil could also affect the efficacy, fate and environmental impact of pesticides. In the current study we investigated the effect of BC on bioavailability of the fungicide azoxystrobin in soil. We found that application of BC had no effect on sorption or degradation of azoxystrobin, even at a rate of 2% w/w. While azoxystrobin reduced dehydrogenase activity, BC addition greatly increased dehydrogenase, although the inhibitory effect of azoxystrobin was still evident in BC amended soil. Using Terminal Restriction Fragment Length Polymorphism of fungal SSU rRNA gene ITS regions it was found that azoxystrobin altered the structure of the soil fungal community, although this effect was dampened by BC addition. BC application had minor effects on fungal community structure. We conclude that measurement of the effect of BC on pesticide bioavailability by analysis of biodegradation rate and non-target effects on fungal community structure gave contrasting conclusions.

Desorption of 1,3,5-Trichlorobenzene from Multi-Walled Carbon Nanotubes: Impact of Solution Chemistry and Surface Chemistry

The strong affinity of carbon nanotubes (CNTs) to environmental contaminants has raised serious concern that CNTs may function as a carrier of environmental pollutants and lead to contamination in places where the environmental pollutants are not expected. However, this concern will not be realized until the contaminants are desorbed from CNTs. It is well recognized that the desorption of environmental pollutants from pre-laden CNTs varies with the environmental conditions, such as the solution pH and ionic strength. However, comprehensive investigation on the influence of solution chemistry on the desorption process has not been carried out, even though numerous investigations have been conducted to investigate the impact of solution chemistry on the adsorption of environmental pollutants on CNTs. The main objective of this study was to determine the influence of solution chemistry (e.g., pH, ionic strength) and surface functionalization on the desorption of preloaded 1,3,5-trichlorobenzene (1,3,5-TCB) from multi-walled carbon nanotubes (MWNTs). The results suggested that higher pH, ionic strength and natural organic matter in solution generally led to higher desorption of 1,3,5-TCB from MWNTs. However, the extent of change varied at different values of the tested parameters (e.g., pH < 7 vs. pH > 7). In addition, the impact of these parameters varied with MWNTs possessing different surface functional groups, suggesting that surface functionalization could considerably alter the environmental behaviors and impact of MWNTs.

Immobilization of chlorobenzenes in soil using wheat straw biochar

Biochar has shown great potential for immobilizing organic contaminants in soil. In this study, pentachlorobenzene (PeCB), 1,2,4,5-tetrachlorobenzene (1,2,4,5-TeCB), and 1,2,4-trichlorobenzene (1,2,4-TCB) artificially spiked soil was amended with wheat straw biochar at 0.1%, 0.5%, 1%, and 2% application rates, respectively. The sorption, dissipation, and bioavailability of chlorobenzenes (CBs) in soil were investigated. The sorption of PeCB by biochar was significantly higher than that of its sorption by both biochar-amended and unamended soil (p < 0.05). The dissipation and volatilization of CBs from biochar-amended soil significantly decreased relative to unamended soil (p < 0.05). Bioavailability of CBs, expressed as butanol extraction efficiency and earthworm (Eisenia fetida) bioaccumulation factor, significantly decreased with increasing aging time and biochar application rate. The effect of biochar content in soil on the bioavailability of CBs was more pronounced for 1,2,4-TCB relative to other CBs. This study suggested that wheat straw biochar, even at low application rates, could effectively immobilize the semivolatile CBs in soil and thus reduce their volatilization and bioavailability.

Biochar-mediated [14C]atrazine mineralization in atrazine-adapted soils from Belgium and Brazil

Biochar addition to soil has been reported to reduce the microbial degradation of pesticides due to sorption of the active compound. This study investigated whether the addition of hardwood biochar alters the mineralization of (14)C-labeled atrazine in two atrazine-adapted soils from Belgium and Brazil at different moisture regimens. Biochar addition resulted in an equally high or even in a significantly higher atrazine mineralization compared to the soils without biochar. Statistical analysis revealed that the extent of atrazine mineralization was more influenced by the specific soil than by the addition of biochar. It was concluded that biochar amendment up to 5% by weight does not negatively affect the mineralization of atrazine by an atrazine-adapted soil microflora.

Marked changes in herbicide sorption-desorption upon ageing of biochars in soil

We studied the sorption-desorption behaviour of two herbicides (diuron and artrazine) in a soil rich in Fe and Al oxides (Ferrosol), either amended freshly with two different types of biochars or that contained biochars aged under field conditions. Standard batch sorption-desorption experiments were conducted on soil samples freshly amended with two biochars, (namely, poultry litter - PL and paper mill - PM sludge) as well on those collected from field 32 months after biochar application. Soils that were freshly amended with biochars @ 10 t ha(-1) showed a two (PM) to five (PL) fold increase in sorption of herbicides as compared with that in the unamended soil. For example, the fresh amendments with PL biochar at 10 t ha(-1) led to a highly significant (P<0.001) increase in the Freundlich sorption coefficient (K(f)) of atrazine; i.e. 20.71 (n=0.40) as compared with 4.02 (n=0.70) for the control soil. Sorption was reversible in the unamended soil but sorption-desorption hysteresis was prominent in the soil amended with fresh biochars. In contrast, the soil containing aged biochars (at 10 t ha(-1)) exhibited sorption-desorption properties that were statistically similar to that of the control soil, especially for atrazine. Ageing of biochars in the soil over a 32 months period reduced the sorption capacity by 47% (PM) to 68% (PL) for diuron. These findings may have implications for herbicide efficacy in biochar amended soils.

Use of rice straw biochar simultaneously as the sustained release carrier of herbicides and soil amendment for their reduced leaching

The sustained release and reduced leaching of herbicides is expected for enhancing their efficacy and minimizing their pollution. For this purpose, the rice straw biochar made at a relatively low temperature (350 °C) (RS350) was used simultaneously as the carrier for incorporating herbicides besides as the soil amendment. In this way, the sustained release of herbicides acetochlor and 2,4-D was obtained in the release experiments, due to the high and reversible sorption by RS350 biochar. Besides, the RS350 biochar significantly reduced the leached amount of herbicides by 25.4%-40.7% for acetochlor, and by 30.2%-45.5% for 2,4-D, depending on the depth (50 or 100 mm) of biochar-amended soil horizon. The high retention of both herbicides in the biochar-amended topsoil makes it possible to extend their efficacy. The results suggest a potential way of using low temperature biochars to reduce the leaching of herbicides without impacting their efficacy.

Reduced adsorption of propanil to black carbon: effect of dissolved organic matter loading mode and molecule size

In the present study, the reduced adsorption of propanil on black carbon (BC) influenced by dissolved organic matter (DOM) was verified to be closely related to DOM molecule size and loading mode. Two congenetic carbons, a rice-residue-derived BC and the reduced product (RC), were characterized by similar specific surface area and different surface properties. Reduced product exhibits higher adsorption of propanil and DOM than BC. A series of model DOMs, including tannic acid (TA), pentagalloylglucose (PA), 3-O-galloylmucic acid (OA), and gallic acid (GA), characterized by different molecule sizes and molecular weights, were used to evaluate the different inhibitory effects. The DOM adsorption (mmol/g) on BC and RC follows the order of GA > PA > OA > TA, whereas the reduction of propanil adsorption influenced by the model DOM follows the order of PA ≈ TA > OA ≈ GA. The suppressive degree is connected to their molecule sizes rather than to molecular weights. Tannic acid and PA weakened propanil adsorption more effectively than OA and GA because the large DOM molecules may hinder propanil molecules into the micropore regions. Because of the similar molecule size, TA and PA present a similar suppressive effect on propanil adsorption. The influence of the DOMs was greater when preloaded than when in competition with propanil. The preloading of macromolecules (TA and PA) and OA on the carbons may lead to secondary and primary micropore blocks, respectively. The preloading of GA may cause partial GA molecule sequestration in the primary micropore, thus leading to strong attenuation of propanil adsorption on the carbons.

Bioavailability assessment of hexachlorobenzene in soil as affected by wheat straw biochar

Biochar incorporation with soil could increase sorption of organic contaminants, thereby reducing their bioavailability. In this study, the effects of wheat straw biochar on the sorption, dissipation and bioavailability of hexachlorobenzene (HCB), a typical persistent organic pollutant (POP), were investigated in laboratory experiments. We observed that HCB sorption by biochar was 42 times higher than that by soil and the sorption isotherm was linear for the concentration range studied. Biochar amendments reduced HCB dissipation, volatilization and earthworm (Eisenia foetida) uptake of HCB from soil. Hydroxypropyl-β-cyclodextrin extraction correlated better with the earthworm bioassay than butanol extraction of HCB in biochar-amended soil. The results of both chemical extraction and earthworm bioassay indicate that biochar amendment of soil resulted in a rapid reduction in the bioavailability of HCB, even for the 0.1% biochar application rate. This suggested that wheat straw biochar could potentially be used in immobilizing POPs in contaminated sites.

The sorption of pentachlorophenol by aged sediment supplemented with black carbon produced from rice straw and fly ash

Black carbon (BC) is a potential material for controlling hydrophobic organic contaminants in sediment because it has a high sorption capacity. In the present study, the sorption of pentachlorophenol (PCP) onto sediments supplemented with rice straw biochar (RC) and fly ash (FC) aged for different times and at temperatures were investigated. The sorption of PCP increased with increasing amounts of BC and decreased with aging time and storage temperature of the BC-supplemented sediments. The sorption of PCP onto RC-supplemented sediments was higher than those supplemented with FC regardless of whether or not BCs were aged in sediments. For aged sediments containing 2% BCs, the sorption capacity was 9.15- and 2.87-fold higher than that of FC when supplemented with RC aged at 25 and 45°C, respectively. Therefore, biochar is better than fly ash for controlling organic pollutants even when the RC was present in sediment for a long time.

Effects of chemical, biological, and physical aging as well as soil addition on the sorption of pyrene to activated carbon and biochar

In this study, the suitability of biochar and activated carbon (AC) for contaminated soil remediation is investigated by determining the sorption of pyrene to both materials in the presence and absence of soil and before as well as after aging. Biochar and AC were aged either alone or mixed with soil via exposure to (a) nutrients and microorganisms (biological), (b) 60 and 110 °C (chemical), and (c) freeze-thaw cycles (physical). Before and after aging, the pH, elemental composition, cation exchange capacity (CEC), microporous SA, and sorption isotherms of pyrene were quantified. Aging at 110 °C altered the physicochemical properties of all materials to the greatest extent (for example, pH increased by up to three units and CEC by up to 50% for biochar). Logarithmic K(Fr) values ranged from 7.80 to 8.21 (ng kg(-1))(ng L(-1))(-nF) for AC and 5.22 to 6.21 (ng kg(-1))(ng L(-1))(-nF) for biochar after the various aging regimes. Grinding biochar to a smaller particle size did not significantly affect the sorption of d(10) pyrene, implying that sorption processes operate on the subparticle scale. Chemical aging decreased the sorption of pyrene to the greatest extent (up to 1.8 log unit for the biochar+soil). The sorption to AC was affected more by the presence of soil than the sorption to biochar was. Our results suggest that AC and biochar have a high sorption capacity for pyrene that is maintained both in the presence of soil and during harsh aging. Both materials could therefore be considered in contaminated land remediation.

A review of biochars' potential role in the remediation, revegetation and restoration of contaminated soils

Biochars are biological residues combusted under low oxygen conditions, resulting in a porous, low density carbon rich material. Their large surface areas and cation exchange capacities, determined to a large extent by source materials and pyrolysis temperatures, enables enhanced sorption of both organic and inorganic contaminants to their surfaces, reducing pollutant mobility when amending contaminated soils. Liming effects or release of carbon into soil solution may increase arsenic mobility, whilst low capital but enhanced retention of plant nutrients can restrict revegetation on degraded soils amended only with biochars; the combination of composts, manures and other amendments with biochars could be their most effective deployment to soils requiring stabilisation by revegetation. Specific mechanisms of contaminant-biochar retention and release over time and the environmental impact of biochar amendments on soil organisms remain somewhat unclear but must be investigated to ensure that the management of environmental pollution coincides with ecological sustainability.

Adsorption of methyl violet from aqueous solutions by the biochars derived from crop residues

The adsorption of methyl violet by the biochars from crop residues was investigated with batch and leaching experiments--adsorption capacity varied with their feedstock in the following order: canola straw char>peanut straw char>soybean straw char>rice hull char. This order was generally consistent with the amount of negative charge of the biochars. Zeta potentials and Fourier transform infrared photoacoustic spectroscopy, combined with adsorption isotherms and effect of ionic strength, indicated that adsorption of methyl violet on biochars involved electrostatic attraction, specific interaction between the dye and carboxylate and phenolic hydroxyl groups on the biochars, and surface precipitation. Leaching experiments showed that 156 g of rice hull char almost completely removed methyl violet from 18.2 L of water containing 1.0 mmol/L of methyl violet. The biochars had high removal efficiency for methyl violet and could be effective adsorbents for removal of methyl violet from wastewater.

Poor efficacy of herbicides in biochar-amended soils as affected by their chemistry and mode of action

We evaluated wheat straw biochar produced at 450°C for its ability to influence bioavailability and persistence of two commonly used herbicides (atrazine and trifluralin) with different modes of action (photosynthesis versus root tip mitosis inhibitors) in two contrasting soils. The biochar was added to soils at 0%, 0.5% and 1.0% (w/w) and the herbicides were applied to those soil-biochar mixes at nil, half, full, two times, and four times, the recommended dosage (H(4)). Annual ryegrass (Lolium rigidum) was grown in biochar amended soils for 1 month. Biochar had a positive impact on ryegrass survival rate and above-ground biomass at most of the application rates, and particularly at H(4). Within any given biochar treatment, increasing herbicide application decreased the survival rate and fresh weight of above-ground biomass. Biomass production across the biochar treatment gradient significantly differed (p<0.01) and was more pronounced in the case of atrazine than trifluralin. For example, the dose-response analysis showed that in the presence of 1% biochar in soil, the value of GR(50) (i.e. the dose required to reduce weed biomass by 50%) for atrazine increased by 3.5 times, whereas it increased only by a factor of 1.6 in the case of trifluralin. The combination of the chemical properties and the mode of action governed the extent of biochar-induced reduction in bioavailability of herbicides. The greater biomass of ryegrass in the soil containing the highest biochar (despite having the highest herbicide residues) demonstrates decreased bioavailability of the chemicals caused by the wheat straw biochar. This work clearly demonstrates decreased efficacy of herbicides in biochar amended soils. The role played by herbicide chemistry and mode of action will have major implications in choosing the appropriate application rates for biochar amended soils.

Adsorption of tetracycline and sulfamethoxazole on crop residue-derived ashes: implication for the relative importance of black carbon to soil sorption

The main objective of this study was to investigate the key factors and mechanisms of antibiotic adsorption on crop residue-derived black carbon, as well as the relative importance of black carbon to the overall sorption to soil. Batch sorption experiments were performed for two reference antibiotics (sulfamethoxazole and tetracycline) on wheat- and maize-residue-derived black carbon. After removal of the mineral fraction from the raw black carbon by acidification, tetracycline exhibited less enhanced adsorption than sulfamethoxazole, implying stronger complexation of tetracycline on the mineral components. The antibiotic adsorption on the demineralized black carbon was very strong (The measured K(d) was in the order of 10(3)-10(5) L/kg). The adsorbent surface area-normalized adsorption of sulfamethoxazole was higher on the demineralized black carbon than on nonporous graphite due to the micropore-filling effect. The opposite trend observed for bulky tetracycline was attributed to the size-exclusion effect. Owing to the strong surface complexation and/or cation exchange reaction, sorption of tetracycline to Na(+)-exchanged montmorillonite, soil humic acids, and bulk soil was remarkably stronger than sulfamethoxazole. It was estimated that the contribution of black carbon to the overall sorption to bulk soil was important for sulfamethoxazole, but negligible for tetracycline.

Biochar derived from anaerobically digested sugar beet tailings: characterization and phosphate removal potential

Two biochars were produced from anaerobically digested and undigested sugar beet tailings through slow-pyrolysis at 600°C. The digested sugar beet tailing biochar (DSTC) and raw sugar beet tailing biochar (STC) yields were around 45.5% and 36.3% of initial dry weight, respectively. Compared to STC, DSTC had similar pH and surface functional groups, but higher surface area, and its surface was less negatively charged. SEM-EDS and XRD analyses showed that colloidal and nano-sized periclase (MgO) was presented on the surface of DSTC. Laboratory adsorption experiments were conducted to assess the phosphate removal ability of the two biochars, an activated carbon (AC), and three Fe-modified biochar/AC adsorbents. The DSTC showed the highest phosphate removal ability with a removal rate around 73%. Our results suggest that anaerobically digested sugar beet tailings can be used as feedstock materials to produce high quality biochars, which could be used as adsorbents to reclaim phosphate.

Sorption of bisphenol A, 17α-ethinyl estradiol and phenanthrene on thermally and hydrothermally produced biochars

Thermal and hydrothermal biochars were characterized, and adsorption of bisphenol A (BPA), 17α-ethinyl estradiol (EE2) and phenanthrene (Phen) was determined to investigate the sorption characteristic difference between the two types of biochars. Thermal biochars were composed mostly of aromatic moieties, with low H/C and O/C ratios as compared to hydrothermal ones having diverse functional groups. Single-point organic carbon-normalized distribution coefficients (logK(OC)) of EE2 and BPA of hydrothermal biochars were higher than thermal biochars, while Phen logK(OC) values were comparable among them. X-ray diffraction and solid state nuclear magnetic resonance results suggested that hydrothermal biochars consisted of more amorphous aliphatic-C, possibly being responsible for their high sorption capacity of Phen. This study demonstrated that hydrothermal biochars could adsorb a wider spectrum of both polar and nonpolar organic contaminants than thermally produced biochars, suggesting that hydrothermal biochar derived from poultry and animal waste is a potential sorbent for agricultural and environmental applications.

Effects of rice straw ash amendment on Cu solubility and distribution in flooded rice paddy soils

Rice straw burning is a common post-harvest practice on rice paddy land, and it leads to the accumulation of rice straw ash (RSA) in paddy soil. To understand the role of RSA in determining the mobility and bioavailability of metal contaminants, this study investigated the effects of RSA amendment on the solubility and distribution of Cu in contaminated rice paddy soils with flooding incubation. The addition of RSA to the soils suppressed the release of Cu into the soil solutions, which was primarily attributed to the metal-binding capacity of the RSA. Additionally, after the soils were flooded, the increase in soil pH and decrease in redox potential resulted in the transformation of Cu into less soluble forms. The RSA amendment appeared to enhance the changes in pH and redox potential of the flooded soils and, consequently, the immobilization of Cu in the soils. The results suggest that the RSA can retard the bioavailability and movement of the metal in contaminated soils and, thus, lower the potential environmental risk of Cu toxicity.

Sorption of deisopropylatrazine on broiler litter biochars

Biochars have received increasing attention in recent years because of a large-scale soil amendment to improve soil fertility, immobilize contaminants, and to serve as a recalcitrant carbon stock. Information is currently lacking in factors controlling the sorption capacity of manure-derived biochars. In this study, sorption isotherms for deisopropylatrazine, a stable metabolite of the widely applied herbicide atrazine, were obtained in acidic aqueous media (pH 5.5) for broiler litter-derived biochars formed by pyrolysis at 350 and 700 °C with and without steam activation at 800 °C. An increase in the Freundlich distribution coefficient (KF) and isotherm nonlinearity (nF) was observed with pyrolysis temperature and steam-activation, suggesting that the surface area and aromaticity (degree of carbonization) are the factors controlling the sorption capacity of chars at low surface coverage. At high surface coverage, the isotherms became increasingly linear, suggesting sorption on noncarbonized fraction of biochars. In binary-solute experiments, the sorption of deisopropylatrazine was significantly diminished by Cu(II), further suggesting the predominance of the surface adsorption mechanism at low surface coverage of biochars.

Sorption properties of greenwaste biochar for two triazine pesticides

Biochar is a carbon-rich product generated from biomass through pyrolysis. This study evaluated the ability of an unmodified biochar to sorb two triazine pesticides - atrazine and simazine, and thereby explored potential environmental values of biochar on mitigating pesticide pollution in agricultural production and removing contaminants from wastewater. A greenwaste biochar was produced by heating waste biomass under the oxygen-limited condition at 450 degrees C. The effects of several experimental parameters, including biochar particle size, contact time, solid/solution ratio, and solution pH on the sorption of atrazine and simazine were comprehensively investigated. The biochar with small particle size needed less time to reach sorption equilibrium. The sorption affinity of the biochar for the two pesticides increased with decreasing solid/solution ratio. The sorbed amounts (C(s)) of atrazine and simazine increased from 451 to 1158 mg/kg and 243 to 1066 mg/kg, respectively, when the solid/solution ratio decreased from 1:50 to 1:1000 (g/mL). The sorption of the biochar for both pesticides was favored by low pH. The sorption isotherms of atrazine and simazine on the biochar are nonlinear and follow a Freundlich model. When atrazine and simazine co-existed, a competitive sorption occurred between these two pesticides on the biochar, reflecting a decrease in sorption capacity (K(f)) from 435 to 286 for atrazine and from 514 to 212 for simazine. Combined adsorption and partition mechanisms well depicted sorption of atrazine and simazine on carbonized and noncarbonized fractions of the biochar in the single-solute and co-solute systems.

Influence of biochars on plant uptake and dissipation of two pesticides in an agricultural soil

This study investigated the influence of two types of biochars on the bioavailability of two soil-applied insecticides (chlorpyrifos and fipronil) to Chinese chives ( Allium tuberosum ) and dissipation of the pesticides in the biochar-amended soils. The biochars (BC450 and BC850) prepared from the burning of cotton ( Gossypium spp.) straw chips at two different temperatures (450 and 850 degrees C) were thoroughly mixed into a soil to achieve 0, 0.1, 0.5, and 1% by soil dry weight. Chinese chives were grown for 5 weeks in the biochar-amended soils spiked with 50 mg kg(-1) of each pesticide. The loss of both pesticides in soils decreased significantly with increasing amounts of the biochars in the soil. After 35 days of incubation, 58-68% of the pesticides was lost from the control soil, whereas in the soil amended with 1.0% BC850 only 34% of chlorpyrifos and 32% of fipronil were dissipated. More losses of the pesticides were found in the soils with plants due to plant uptake and enhanced microbial degradation. Despite greater persistence of the two pesticide residues in the biochar-amended soils, plant uptake of the two pesticides from the amended soils decreased markedly with increasing biochar content in the soil. With the amendment of 1% of BC850 in the soil, the total chlorpyrifos and fipronil residues in plant biomass decreased to 19 and 48% of those in the control treatment, respectively. Thus, biochar BC850 was found to be effective in reducing the bioavailability of both pesticides from the soil. Biochar could be applied to sequester pesticide residues in contaminated soils and to reduce plant uptake.