Biochar-based materials as remediation strategy in petroleum hydrocarbon-contaminated soil and water: Performances, mechanisms, and environmental impact.

Petroleum contamination is considered as a major risk to the health of humans and environment. Biochars as low-cost and eco-friendly carbon materials, have been widely used for the removal of petroleum hydrocarbon in the environment. The purpose of this paper is to review the performance, mechanisms, and potential environmental toxicity of biochar, modified biochar and its integration use with other materials in petroleum contaminated soil and water. Specifically, the use of biochar in oil-contaminated water and soil as well as the factors that could influence the removal ability of biochar were systematically evaluated. In addition, the modification and integrated use of biochar for improving the removal efficiency were summarized from the aspects of sorption, biodegradation, chemical degradation, and reusability. Moreover, the functional impacts and associated ecotoxicity of pristine and modified biochars in various environments were demonstrated. Finally, some shortcoming of current approaches, and future research needs were provided for the future direction and challenges of modified biochar research. Overall, this paper gain insight into biochar application in petroleum remediation from the perspectives of performance enhancement and environmental sustainability.

Effects of biochar and N-stabilizers on greenhouse gas emissions from a subtropical pasture field applied with organic and inorganic nitrogen fertilizers.

Pasturelands contribute significantly to the global CO2, CH4 and N2O emissions. These gas emissions are influenced by the amount and type of N-fertilizers applied and local climate. Recent studies showed potential of biochar and N-stabilizer compounds in minimizing CO2, CH4 and N2O emissions by regulating N-release from N-fertilizers. The present study was aimed at determining and comparing the effects of biochar and N-(n-butyl) thiophosphoric triamide + dicyandiamide (N-stabilizer) on CO2, N2O and CH4 emissions from a pasture fertilized with cattle manure or urea. The study was conducted during 2015 and 2016 in an established bermudagrass (Cynodon dactylon L. Pers.). Treatments consisted of combination of N-sources (manure, and urea) and two mitigation technologies [pine hardwood biochar (BC) and N-stabilizer] along with control. Emissions of GHGs were measured from each plot using static chamber systems. Both BC and N-stabilizer applications with manure applied to the hay field significantly decreased N2O emissions by 42% and 45%, respectively, in the year-2, and emission factors compared to manure only treatment. Addition of N-stabilizer to urea had significantly decreased N2O emissions compared to urea alone, while BC had statistically insignificant effect although numerically lowered N2O emissions in both the years. Application of manure to the soil resulted in significantly higher CO2 emissions in both years and CH4 emissions in 2016 compared to unfertilized soil. Urea application had significant effect on CO2 emissions in 2016, while no effect on CH4 emissions compared to control. Application of either biochar or N-stabilizer did not significantly affect CO2 and CH4 emissions.

Removal of potentially toxic metal by biochar derived from rendered solid residue with high content of protein and bone tissue.

The purpose of this study was to produce rendering animal carcass residue char (RACR-C) by pyrolyzing the solid residues of low-recyclable rendered pig carcasses and to evaluate their cadmium (Cd) adsorption characteristics and mechanisms. As the pyrolysis temperature increased, the inorganic content of RACR-C increased, while the carbon content decreased. In particular, the surface structure and chemistry of RACR-Cs prepared at different pyrolysis temperatures were well described by SEM-EDS, XRD, XRF, TGA, and FTIR. The Cd adsorption characteristics of RACR-C were in good agreement with the Langmuir isotherm and pseudo-second-order models, and the Cd adsorption capacities of RACR-Cs prepared at various pyrolysis temperatures were in the order of RACR-C500 (73.5 mg/g)> RACR-C600 (53.8 mg/g)> RACR-C400 (41.5 mg/g) " RACR-C250 (15.9 mg/g). The intraparticle diffusion model suggested that the adsorption of Cd by RACR-C is greatly influenced by internal diffusion as well as external boundary. Since the Cd adsorption capacity of RACR-C is greatly influenced by the initial dosage, pH, and co-existing metals, it is necessary to manage these influencing factors when treating wastewater containing heavy metals. Our results suggest that Cd adsorption by RACR-C is a complex adsorption phenomenon by various mechanisms such as adsorption by functional group (CË­C and C-O), precipitation of Cd-P and ion exchange reaction by exchangeable cation occurring rather than by a single specific mechanism.

Lead sorption characteristics of various chicken bone part-derived chars.

Recycling food waste for beneficial use is becoming increasingly important in resource-limited economy. In this study, waste chicken bones of different parts from restaurant industry were pyrolyzed at 600 °C and evaluated for char physicochemical properties and Pb sorption characteristics. Lead adsorption isotherms by different chicken bone chars were carried out with initial Pb concentration range of 1-1000 mg L-1 at pH 5. The Pb adsorption data were better described by the Langmuir model (R2 = 0.9289-0.9937; ARE = 22.7-29.3%) than the Freundlich model (R2 = 0.8684-0.9544; ARE = 35.4-72.0%). Among the chars derived from different chicken bone parts, the tibia bone char exhibited the highest maximum Pb adsorption capacity of 263 mg g-1 followed by the pelvis (222 mg g-1), ribs (208 mg g-1), clavicle (179 mg g-1), vertebrae (159 mg g-1), and humerus (135 mg g-1). The Pb adsorption capacities were significantly and positively correlated with the surface area, phosphate release amount, and total phosphorus content of chicken bone chars (r ≥ 0.9711). On the other hand, approximately 75-88% of the adsorbed Pb on the chicken bone chars was desorbable with 0.1 M HCl, indicating their recyclability for reuse. Results demonstrated that chicken bone char could be used as an effective adsorbent for Pb removal in wastewater.

Facilitative capture of As(V), Pb(II) and methylene blue from aqueous solutions with MgO hybrid sponge-like carbonaceous composite derived from sugarcane leafy trash.

Enhancing the contaminant adsorption capacity is a key factor affecting utilization of carbon-based adsorbents in wastewater treatment and encouraging development of biomass thermo-disposal. In this study, a novel MgO hybrid sponge-like carbonaceous composite (HSC) derived from sugarcane leafy trash was prepared through an integrated adsorption-pyrolysis method. The resulted HSC composite was characterized and employed as adsorbent for the removal of negatively charged arsenate (As(V)), positively charged Pb(II), and the organic pollutant methylene blue (MB) from aqueous solutions in batch experiments. The effects of solution pH, contact time, initial concentration, temperature, and ionic strength on As(V), Pb(II) and MB adsorption were investigated. HSC was composed of nano-size MgO flakes and nanotube-like carbon sponge. Hybridization significantly improved As(V), Pb(II) and methylene blue (MB) adsorption when compared with the material without hybridization. The maximum As(V), Pb(II) and MB adsorption capacities obtained from Langmuir model were 157 mg/g, 103 mg/g and 297 mg/g, respectively. As(V) adsorption onto HSC was best fit by the pseudo-second-order model, and Pb(II) and MB with the intraparticle diffusion model. Increased temperature and ionic strength decreased Pb(II) and MB adsorption onto HSC more than As(V). Further FT-IR, XRD and XPS analysis demonstrated that the removal of As(V) by HSC was mainly dominated by surface deposition of MgHAsO4 and Mg(H2AsO4)2 crystals on the HSC composite, while carbon π-π* transition and carbon π-electron played key roles in Pb(II) and MB adsorption. The interaction of Pb(II) with carbon matrix carboxylate was also evident. Overall, MgO hybridization improves the preparation of the nanotube-like carbon sponge composite and provides a potential agricultual residue-based adsorbent for As(V), Pb(II) and MB removal.

Soil heavy metal contamination and health risks associated with artisanal gold mining in Tongguan, Shaanxi, China.

Soil contamination with heavy metals due to mining activities poses risks to ecological safety and human well-being. Limited studies have investigated heavy metal pollution due to artisanal mining. The present study focused on soil contamination and the health risk in villages in China with historical artisanal mining activities. Heavy metal levels in soils, tailings, cereal and vegetable crops were analyzed and health risk assessed. Additionally, a botany investigation was conducted to identify potential plants for further phytoremediation. The results showed that soils were highly contaminated by residual tailings and previous mining activities. Hg and Cd were the main pollutants in soils. The Hg and Pb concentrations in grains and some vegetables exceeded tolerance limits. Moreover, heavy metal contents in wheat grains were higher than those in maize grains, and leafy vegetables had high concentrations of metals. Ingestion of local grain-based food was the main sources of Hg, Cd, and Pb intake. Local residents had high chronic risks due to the intake of Hg and Pb, while their carcinogenic risk associated with Cd through inhalation was low. Three plants (Erigeron canadensis L., Digitaria ciliaris (Retz.) Koel., and Solanum nigrum L.) were identified as suitable species for phytoremediation.

Ammonia and greenhouse gas emissions from a subtropical wheat field under different nitrogen fertilization strategies.

Minimizing soil ammonia (NH3) and nitrous oxide (N2O) emission factors (EFs) has significant implications in regional air quality and greenhouse gas (GHG) emissions besides nitrogen (N) nutrient loss. The aim of this study was to investigate the impacts of different N fertilizer treatments of conventional urea, polymer-coated urea, ammonia sulfate, urease inhibitor (NBPT, N-(n-butyl) thiophosphoric triamide)-treated urea, and nitrification inhibitor (DCD, dicyandiamide)-treated urea on emissions of NH3 and GHGs from subtropical wheat cultivation. A field study was established in a Cancienne silt loam soil. During growth season, NH3 emission following N fertilization was characterized using active chamber method whereas GHG emissions of N2O, carbon dioxide (CO2), and methane (CH4) were by passive chamber method. The results showed that coated urea exhibited the largest reduction (49%) in the EF of NH3-N followed by NBPT-treated urea (39%) and DCD-treated urea (24%) over conventional urea, whereas DCD-treated urea had the greatest suppression on N2O-N (87%) followed by coated urea (76%) and NBPT-treated urea (69%). Split fertilization of ammonium sulfate-urea significantly lowered both NH3-N and N2O-N EF values but split urea treatment had no impact over one-time application of urea. Both NBPT and DCD-treated urea treatments lowered CO2-C flux but had no effect on CH4-C flux. Overall, application of coated urea or urea with NPBT or DCD could be used as a mitigation strategy for reducing NH3 and N2O emissions in subtropical wheat production in Southern USA.

Heavy metal distribution and water quality characterization of water bodies in Louisiana's Lake Pontchartrain Basin, USA.

The seasonal variation in physico-chemical properties, anions, and the heavy metal (Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn) concentration was evaluated in water from nine different rivers in Lake Pontchartrain Basin, Louisiana, USA. The water quality parameters were compared with toxicity reference values (TRV), US Environmental Protection Agency (USEPA) drinking/aquatic life protection, and WHO standards. Among physico-chemical properties, pH, DO, and turbidity were high during spring, while, EC, temperature, and DOC were high during summer and vice versa. The anion study revealed that the concentrations of F-, Cl-, and NO3- were higher during summer and Br- and SO4- were higher during spring. Our research findings showed anion concentration decreased in the order of Cl- > SO4- > NO3- > Br- > F-, in accordance with the global mean anion concentration. The dissolved heavy metals (Cd, Co, Cr, Cu, Mn, Ni, Pb) except Zn were higher during spring than summer. None of the rivers showed any Cd pollution for both seasons. Co showed higher concentrations in Amite River, Mississippi River, Industrial Canal, and Lacombe Bayou during summer. The Cr concentration was higher than WHO drinking water standards, implicating water unsuitability for drinking purposes in all the rivers associated with the Lake Pontchartrain Basin. Cu showed no pollution risk for the study area. Mn and Co were similar to concentration in Lacombe Bayou, Liberty Bayou, Blind River, and Industrial Canal. Mn levels were greater than WHO standards for the Tickfaw River, Tangipahoa River, and Blind River in both seasons. Blind River, Tangipahoa River, Tickfaw River, and Amite River will require more monitoring for determining possible Mn pollution. Ni content in river water during both seasons showed low pollution risk. Liberty Bayou and Industrial Canal concentrations were closer to the WHO regulatory standards, indicating possible risk of Pb pollution in these water bodies. The Zn content was near the USEPA aquatic life standards in summer for all water bodies. None of the rivers showed any risk associated with Cd, Co, Cu, and Ni levels but medium to higher risk to aquatic life from Cr and Zn for both seasons for most of the rivers. Metal fractionation revealed the decreasing order of inert > labile > organic. The high inert fraction in the rivers under study reflects the major contribution of natural sources in Lake Pontchartrain Basin. The labile and organic forms of Cd, Cu, Ni, and Zn pose potential higher risk to the aquatic life in the Lake Pontchartrain Basin.

Zinc and cadmium adsorption to aluminum oxide nanoparticles affected by naturally occurring ligands.

Nanoparticles of aluminum oxide (AlO) are efficient in removing Cd, Zn, and other heavy metals from wastewaters and soil solutions due to their high specific surface area and surface area to volume ratio. Naturally occurring ligands, such as phosphate (PO), citrate, and humic acid (HA), may affect the efficiency of AlO nanoparticles in adsorption of Cd and Zn. The objective of this study was to investigate Zn and Cd adsorption to AlO nanoparticles as influenced by PO, citrate, and HA. Adsorption of Zn and Cd was performed in mono-metal and binary-metal systems at pH 6.5 with initial metal concentration of 1.0 mmol L and varying ligand concentration at a solid:solution ratio of 1:1000. Adsorption isotherms showed that Zn had higher affinity to the AlO nanoparticle surface than Cd and that adsorption of Zn and Cd in the binary-metal system was lower than in the respective mono-metal systems. Phosphate and HA enhanced Zn and Cd adsorption in all systems, whereas citrate reduced Zn adsorption in the mono-metal system by 25% and increased adsorption in the other metal systems. Removal of Zn or Cd from the systems was generally accompanied by enhanced removal of PO and HA, which may indicate enhanced adsorption due to ternary complex formation or metal-ligand precipitation. Phosphate was the most effective among the three ligands in enhancing Zn and Cd adsorption. Overall, AlO nanoparticles are suitably used for Zn and Cd adsorption, which can be significantly enhanced by the presence of PO or HA and to a lesser degree by citrate at low concentrations.

The role of extracellular polymeric substances (EPS) in chemical-degradation of persistent organic pollutants in soil: A review.

Persistent organic pollutants (POPs) in soil show high environmental risk due to their high toxicity and low biodegradability. Studies have demonstrated the degradation function of microbial extracellular polymeric substances (EPS) on POPs in various matrices. However, the degradation mechanisms and the factors that influence the process in soil have not been clearly illustrated. In this review, the characteristics of EPS were introduced and the possible mechanisms of EPS on degradation of organic pollutants (e.g., external electron transfer, photodegradation, and enzyme catalysis) were comprehensively discussed. In addition, the environmental conditions (e.g., UV, nutrients, and redox potential) that could influence the production and degradation-related active components of EPS were addressed. Moreover, the current approaches on the application of EPS in biotechnology were summarized. Further, the future perspectives of enhancement on degradation of POPs by regulating EPS were discussed. Overall, this review could provide a new thought on remediation of POPs by widely-existing EPS in soil with low-cost and minimized eco-disturbance.

Tea-based biochar-mediated changes in cation diffusion homeostasis in rice grown in heavy metal (loid) contaminated mining soil.

Foreseeable future scenarios highlight the urgency of applying eco-safe avoidance methods or tolerance to heavy metal(loid) (HM) stress in agricultural production areas of contamination. The analyses show that the Ni, Mn, As, and Cr concentrations detected in the soils of the paddy fields in the Black Sea region vary between 123.60 and 263.30; 687-1271; 8.90-14.50; 162.00-340.00 mg kg-1 proving high accumulation of Ni, Mn, As, Cr in rice. Overconsumption of rice farmed extensively on these soils might also lead to human HM-related health problems. Therefore, in the current study, the approach of using tea-based biochar (BC) proven to have one of the most significant potentials as a soil amendment to reduce HM transmission to in-vitro-grown rice plants was investigated in the soil medium naturally contaminated with HMs. The tea-BC was produced from readily available local black tea waste of a conventional fermentation process and applied in the in-vitro experiments. Among the tested doses examined, 1% tea-BC showed a more positive effect on rice plant growth and development characterized by a better relative growth rate (59.7 and 84 mg g-1 d-1 for root and shoot tissues), photosynthetic pigment intactness (62.48 µg mL-1), cellular membrane integrity (93%), and relative water (96%) than the other rates (0% BC, 3%BC, 5%BC). The mRNA expression data highlights the probability of a cation diffusion facilitator (CDF) (OsMTP11) in concert with catalase isozyme (CATa) and dehydration-responsive element binding protein (DREB1a) linking the HM detoxification, oxidative defense, and dehydration pathways with the help of tea-BC. At the optimum concentration (1%BC), this approach might reduce HM accumulation levels of crops planted in HM-contaminated farmlands.

Effect of biochar amendment on tylosin adsorption-desorption and transport in two different soils.

The role of biochar as a soil amendment on the adsorption-desorption and transport of tylosin, a macrolide class of veterinary antibiotic, is little known. In this study, batch and column experiments were conducted to investigate the adsorption kinetics and transport of tylosin in forest and agricultural corn field soils amended with hardwood and softwood biochars. Tylosin adsorption was rapid at initial stages, followed by slow and continued adsorption. Amounts of adsorption increased as the biochar amendment rate increased from 1 to 10%. For soils with the hardwood biochar, tylosin adsorption was 10 to 18% higher than that when using the softwood biochar. Adsorption kinetics was well described by Elovich equation ( ≥ 0.921). As the percent of biochar was increased, the rates of initial reactions were generally increased, as indicated by increasing α value at low initial tylosin concentration, whereas the rates during extended reaction times were generally increased, as indicated by decreasing ß value at high initial tylosin concentration. A considerably higher amount of tylosin remained after desorption in the corn field soil than in the forest soil regardless of the rate of biochar amendment, which was attributed to the high pH and silt content of the former. The breakthrough curves of tylosin showed that the two soils with biochar amendment had much greater retardation than those of soils without biochar. The CXTFIT model for the miscible displacement column study described well the peak arrival time as well as the maximum concentration of tylosin breakthrough curves but showed some underestimation at advanced stages of tylosin leaching, especially in the corn field soil. Overall, the results indicate that biochar amendments enhance the retention and reduce the transport of tylosin in soils.

Transcriptional insights into Cu related tolerance strategies in maize linked to a novel tea-biochar.

One-third of maize cultivation in Turkey has been performed in nutrient-rich soils of the coastal agricultural lands of the Black Sea Region, which is among the country's granaries. However, the yield of this chief crop is affected by Cu toxicity due to a decades-long abandoned opencast Cu-mine. As part of the modern agenda, against this problem, we valorized one of the region's signature plant waste by synthesizing a tea-derived biochar (BC) and evaluated for remediation effect on maize Cu tolerance. Among other rates (0%, 0.4%, 0.8%, 1.6%), maximum Cu absorption (168.27 mg kg-1) was found in the 5%BC in in-vitro spiking experiments where natural Cu contamination levels were mimicked. Obvious increasing trends in both root and shoot tissues of maize plantlets growing in Cu-spiked soil (260.26 ± 5.19 mg Cu kg-1) were recorded with proportionally increasing BC application rates. The black tea waste-BC (5%) amendment remarkably reduced the Cu uptake from Cu spiked-soil and showed no phenotypic retardation in maize. Accordingly, it boosted the metabolic and transcriptomic profile owing to up-regulation in the aquaporin and defense genes (PIP1;5 and POD1) by 1.31 and 1.6 fold. The tea-BC application also improved the soil-plant water relations by minimizing cytosolic volume changes between 85 and 90%, increasing chlorophyll intactness (65%) and membrane stability up to 41%. The tea-BC could be a strong agent with potential agronomic benefits in the remediation of the cationic Cu toxicity that occurred in the mining-contaminated agricultural soils.

Solid digestate biochar amendment on pig manure composting: Nitrogen cycle and balance.

Effect of solid digestate biochar (DB) on nitrogen cycle and balance was evaluated during composting by adding DB into mixtures of pig manure and Lycium chinensis branch filings. Results indicated that DB addition improved composting microenvironment and increased the total N content of the final product. Furthermore, N balance calculation indicated that the NH3 and N2O emissions accounted for 72.14%-81.39% and 0.49%-2.37% of the total N loss without DB addition, respectively. After using DB, the N reductions in the form of NH3 and N2O reduced from 10.78% to < 5.73% and from 0.34% to < 0.041% of total N, respectively. Addition of DB affected N fixation with 92.32%-93.67% of total N fixed in the compost than that of the T1 treatment (85.63%). DB amendment enhanced the aerobic bacterial communities and hindered anaerobic bacterial growth, thus benefiting the NH3 and N2O emission mitigation and N conservation.

Effect of organic matter oxidation on the fractionation of copper, zinc, lead, and arsenic in sewage sludge and amended soils.

Long-term land application of sewage sludge (SS) has caused concern over the potential release of trace metals into the environment following the degradation of organic matter (OM). This study was performed to assess the impact of OM degradation on the relative distribution of Cu, Zn, Pb, and As in SS and SS-amended soils. Three SSs of different ages and two soils treated with SS were subjected to incubation and direct chemical oxidation using diluted HO, followed by a sequential extraction. The majority of Cu, Pb, and As were bound to OM, whereas the majority of Zn was bound with Fe/Mn oxides for all three SSs. Incubation of SS for 6 mo did not result in a substantial decrease in OM content or a change in the relative distribution of Cu, Zn, Pb, and As. Direct OM oxidation to 30 and 70% by diluted HO resulted in a significant decrease in organically bound Cu but increased its exchangeable, carbonate-bound, and Fe/Mn-bound fractions. Oxidation of OM slightly decreased organically bound Zn but significantly increased exchangeable Zn in all SSs. Oxide- and carbonate-bound Zn also decreased following OM oxidation. Exchangeable fractions of As and Pb were minute before and after OM degradation, indicating that release into the environment would be unlikely. The relative distribution of Cu, Zn, Pb, and As in SS-treated soils was similar to that of SS, suggesting a dominant role of SS properties in controlling metal distribution following OM oxidation. Overall, OM oxidation increased the mobility and bioavailability of Zn and Cu, whereas it had less impact on Pb and As.

Integrated application effects of biochar and plant residue on ammonia loss, heavy metal immobilization, and estrogen dissipation during the composting of poultry manure.

Inadequate handling of poultry manure can cause significant releases of NH3, heavy metals, and estrogen, thereby impairing environmental quality. This study was a composting experiment involving the combination of poultry manure with plant residues (corn stalks, mushroom residues, and vegetable straw), as well as with either wheat stalk biochar (WB) or rice husk biochar (RB). The integrated effects of plant residues and biochar on NH3 loss, heavy metal (Cu, Zn, As, and Cd) stabilization, and 17ß-estradiol (E2) dissipation were investigated during composting. The poultry manure co-composted with corn straw and mushroom residue showed the highest potential for E2 degradation. Biochar enhanced E2 dissipation and decreased estrogenic activity in all treatments, with RB showing a stronger effect than WB. Both biochars decreased microbial diversity and increased bacterial groups related to E2 and organic matter degradation·NH3 emission was reduced by 50-82% with 15% WB and 86-97% with 15% RB. The extractable fraction of As was reduced by 0-53% with WB and 50-84% with RB, while that of Cd was reduced by 5-28% for WB and 25-41% for RB in poultry manure compost. However, biochar showed little effect on Cu and Zn. Biochar appears to have a promotional effect and enhances the microbial degradation of E2. Specifically, the integration of corn stalks, mushroom residues, and RB in poultry manure compost had a positive effect by preventing nitrogen loss while reducing the bioavailability of heavy metals and hormones.

Application of biochar in estrogen hormone-contaminated and manure-affected soils: Impact on soil respiration, microbial community and enzyme activity.

Biochar as a soil amendment has been proposed for enhancing carbon sequestration and manure-borne hormone contaminant remediation. However, little is known about the ecological risk of biochar application in the soil with hormone contamination. This study investigated the influence of biochar in three manure-impacted soils contaminated with estrogen hormones, natural estrogen 17ß-estradiol and synthesized estrogen 17α-ethinylestradiol in a microcosm experiment. Specifically, microbial respiration was periodically determined during microcosm incubation while microbial community phospholipid fatty acids and activities of nutrient (C, N, P, S) cycling related enzymes (ß-glucosidase, urease, phosphodiesterase, arylsulfatase) were characterized after the incubation. Results showed that the manure-impacted soils with high SOC generally had greater total microbial biomass, ratios of fungi/bacteria and Gram-positive bacteria/Gram-negative bacteria, and phosphodiesterase activity, but lower urease activity. Additionally, hormones stimulated microbial respiration and biomass, while had little impact on activity of the enzymes. On the other hand, biochar showed negative priming effect by significantly decreasing total microbial biomass by 8.7%-26.4%, CO2 production by 16.6%-33.5%, and glucosidase activity by 27.1%-41.0% in the three soils. Biochar significantly increased the activity of phosphodiesterase, showed no impact on arylsulfatase, while decreased the activity of urease. Overall, the study suggests that when used in hormone remediation in manure-impact soils, biochar could improve phosphodiesterase activity, but may decrease soil microbial activity and the activity of soil glucosidase and urease.

Remediation of crude oil-contaminated coastal marsh soil: Integrated effect of biochar, rhamnolipid biosurfactant and nitrogen application.

Decontamination of oil spills from coastal wetland soils requires a delicate approach. A microcosm study was carried out to investigate the impact of integrated application of biochar, rhamnolipid (RL) biosurfactant and nitrogen (N) on petroleum hydrocarbon remediation in a Louisiana coastal saline marsh and their impact on soil microbial community. The soil was artificially contaminated with crude oil and subjected to treatments of different combinations of sugarcane residue biochar, RL, and coated urea. Total petroleum hydrocarbons (TPH) in the contaminated soil were analyzed periodically using gas chromatograph and associated soil bacterial community was studied using 16 s rRNA sequencing technologies. Results showed that integrated application of biochar + RL, biochar + N, and biochar + N+RL reduced 32.3%, 73.2%, 80.9% of TPH, respectively, and exhibited synergic interaction with higher efficiency than application individually. Combined treatments showed distinct functions that biochar increased the sorption of aromatic compounds, while RL and N enhanced the degradation of heavy and light aliphatic compounds. All remediation treatments caused reduction of soil bacterial diversity while RL and N shifted the microbial community to higher abundances of Proteobacteria and Bacteroidetes, respectively. Overall, the findings of this study demonstrate the positivity of applying integrated biochar, biosurfactant, and N treatment in oil remediation in wetland soils.

Potential use of biochar and rhamnolipid biosurfactant for remediation of crude oil-contaminated coastal wetland soil: Ecotoxicity assessment.

Remediation of wetland soils contaminated with petroleum hydrocarbons is a challenging task. Biosurfactant and biochar have been used in oil remediation. However, little is known about the ecotoxicity of these materials when applied in wetland ecosystems. In this study, the ecotoxicity of biochar and rhamnolipid (RL) biosurfactant as crude oil remediation strategies in a Louisiana wetland soil was investigated. A pot experiment was set up with wetland soil treated with/without crude oil followed by subjecting to application of 1% biochar and various levels of RL ranging from 0.1% to 1.4%. The ecotoxicity was evaluated regarding to high plant (S. Alterniflora), algae, and soil microbes. Specifically, after a 30-day growth in a controlled chamber, plant biomass change as well as shoot/root ratio was measured. Algae growth was estimated by quantifying chlorophyll by spectrometry following separation, and soil microbial community was characterized by phospholipid fatty acids analysis. Results showed that plant can tolerate RL level up to 0.8%, while algae growth was strongly inhibited at RL > 0.1%. Algal biomass was significantly increased by biochar, which offset the negative impact of oil and RL. Additionally, soil microbial community shift caused by crude oil and RL was alleviated by biochar with promoting Gram-positive bacteria, actinomycetes, and arbuscular mycorrhizal fungi. Overall, this study shows that integrated treatment of biochar and RL has the lowest ecotoxicity to plant and algae when used in oil remediation of contaminated wetland soils.

Exploring anaerobic CO2 production response to elevated nitrate levels in Gulf of Mexico coastal wetlands: Phenomena and relationships.

Recent studies have shown the effect of nitrate (NO3-) on carbon gas emissions from wetland soils that contradict thermodynamic predictions. In this study, CO2 production in three Mississippi River deltaic plain wetland soils (forest swamp, freshwater and saline marshes) with the presence of different NO3- levels (0.2, 2.0, and 3.2 mM) was evaluated in an anaerobic microcosm. Molecular composition of dissolved organic matter (DOM) of these soils was investigated using pyrolysis-GC/MS, and soil microbial community was characterized based on phosphorus lipid fatty acid (PLFA) method to elucidate the underlying mechanisms. Addition of NO3- promoted CO2 production in swamp forest soil, but inhibited CO2 emission from marsh soils. Pyrolysis-GC/MS analysis showed that swamp soil contained more polysaccharides, whereas both marsh soils had high abundance of phenolic compounds. Total PLFAs of forest swamp soil were 34% and 66% higher than freshwater and saline marsh soils, respectively. The PLFA profiles indicated different microbial distribution along a salinity gradient with the forest swamp having a higher proportion of fungi and NO3- reducers but lower sulfate (SO42-) reducers than marsh soils. Overall, the study indicated that the inherent differences in soil DOM and microbial community led to the contrasting response in soil CO2 respiration between forest swamp and marsh ecosystems to NO3- loading. These differences should be considered in determining the fate of nitrate entering Louisiana coastal wetlands from river diversions and other sources and their management.