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

Impact of propiconazole fungicide on soil microbiome (bacterial and fungal) diversity, functional profile, and associated dehydrogenase activity

Pesticides, protect crops but can harm the environment and human health when used without caution. This study evaluated the impact of propiconazole, a fungicide that acts on fungal cell membranes, on soil microbiome abundance, diversity, and functional profile, as well as soil dehydrogenase activity (DHA). The study conducted microcosm experiments using soil samples treated with propiconazole and employed next-generation sequencing (MiSeq) and chromatographic approaches (GC-MS/MS) to analyze the shift in microbial communities and propiconazole level, respectively. The results showed that propiconazole significantly altered the distribution of microbial communities, with notable changes in the abundance of various bacterial and fungal taxa. Among soil bacterial communities, the relative abundance of Proteobacteria and Planctomycetota increased, while that of Acidobacteria decreased after propiconazole treatment. In the fungal communities, propiconazole increased the abundance of Ascomycota and Basidiomycota in the treated soil, while that of Mortierellomycota was reduced. Fungicide application further triggered a significant decrease in DHA over time. Analysis of the functional profile of bacterial communities showed that propiconazole significantly affected bacterial cellular and metabolic pathways. The carbon degradation pathway was upregulated, indicating the microbial detoxification of the contaminant in the treated soil. Our findings suggest that propiconazole application has a discernible impact on soil microbial communities, which could have long-term consequences for soil health, quality, and function.

Fertilization can modify the enantioselective persistence of penthiopyrad in relation to the co-influence on soil ecological health

Penthiopyrad is a widely used chiral fungicide for controlling rust and Rhizoctonia diseases. Development of optically pure monomers is an important strategy to realize amount reduction and increment effects of penthiopyrad, wherein, fertilizers as the co-exiting nutrient supplement may alter the enantioselective residues of penthiopyrad in soil. In our study, influences of urea, phosphate, potash, NPK compound, organic granular, vermicompost and soya bean cake fertilizers on enantioselective persistence of penthiopyrad were fully evaluated. This study demonstrated that R-(-)-penthiopyrad dissipated faster than S-(+)-penthiopyrad during 120 days. High pH, available nitrogen, invertase activities and reduced available phosphorus, dehydrogenase, urease, catalase activities were situated to benefit removing the concentrations of penthiopyrad and weakening enantioselectivity in soil. With respect to the impact of different fertilizers on soil ecological indicators, vermicompost contributed to enhanced pH. Urea and compound fertilizer played an absolute advantage in promoting available nitrogen. All fertilizers didn't go against available phosphorus. Dehydrogenase responded negatively to phosphate, potash and organic fertilizers. Urea increased invertase, besides, it and compound fertilizer both diminished urease activity. The catalase activity was not activated by organic fertilizer. Based on all the findings, soil application of urea and phosphate fertilizers was recommended and considered as a better option to exhibit high efficiency for the dissipation of penthiopyrad. The combined environmental safety estimation can effectively guide the treatment of fertilization soils in line with the nutrition requirements and pollution regulation from penthiopyrad.

Effects of wetland plant biochars on heavy metal immobilization and enzyme activity in soils from the Yellow River estuary

The purpose of this study was to assess the effects of wetland plant biochars on the enzyme activity in heavy metal contaminated soil. The biochars were produced from Phragmites australis (PB), Suaeda salsa (SB), and Tamarix chinensis (TB) under different pyrolysis temperatures and times. The detected pyrolysis products showed that the ash, pH, electrical conductivity, and carbon content of the biochars increased significantly, while the production rate of the biochars decreased with increasing pyrolysis temperature and time. The results of the adsorption experiments indicated that biochar addition could effectively reduce the concentration of Pb and/or Cd in the Pb²⁺/Cd²⁺ single or mixed solutions, but the Pb²⁺ and Cd²⁺ in the mixed solution indicated a competitive adsorption. A 30-day incubation experiment was conducted using salt marsh soil amended with different biochar application rates to investigate the short-term effects of biochar addition on Pb and Cd immobilization. The PB and SB significantly immobilized Pb within the first 15 days, but Pb remobilized within the next 15-day period. In contrast, TB addition did not significantly fix Pb. Moreover, biochar addition promoted the conversion of Cd from the residue to the less immobile fractions. The addition of three types of plant biochar had no significant effect on the urease activity in wetland soil but significantly increased soil sucrase activity. PB and SB significantly promoted catalase activity, while TB significantly inhibited soil catalase activity. According to the adsorption effect, the fixation effect, and the promotion of enzyme activities, the Suaeda salsa biochars are suitable for the remediation of heavy metal pollution in wetland soils.

Effects of increasing concentrations of fungicide QuadrisR on bacterial functional profiling in loamy sand soil

A mesocosm experiment was conducted to assess the side effects of the fungicide Quadris^R on soil bacterial functioning. Quadris^R was applied to a loamy sand soil at increasing concentrations (0.0-35.0 mg kg^-1 dry soil) calculated according to its active ingredient azoxystrobin (Az). Soil sampling was carried out from the 1st to the 120th day of soil incubation to determine the changes occurred in bacterial catabolism using the technique of community-level physiological profiling (CLPP) via Biolog EcoPlates™. It was found that the field recommended fungicide concentration (2.90 mg kg^-1 dry soil) altered mostly the low-available Biolog carbon sources (< 0.50 optical density (OD)), whereas the fungicide higher concentrations (14.65 and 35.00 mg kg^-1 dry soil) were effective also on medium (0.50-1.00 OD) and highly (> 1.00 OD) utilizable ones. Pearson correlation analysis revealed that the main environmental factors correlated with the utilization rates of Biolog carbon sources (CSs) were soil nutrients and pH. No linear relationships were found between Az soil residues and the use of CSs. We concluded that Quadris^R affects bacterial catabolic profiles in loamy sand soils through soil acidification and altering soil nutrient pool. The study also revealed that CLPP and EcoPlate™ are useful practical tools for testing the fungicide ecotoxicity.

Ecotoxicology of strobilurin fungicides

Strobilurin fungicides (SFs), a class of new fungicides, use strobilurin A as a lead compound. However, with excessive production and usage, the SF residues in soil and aquatic ecosystems may lead to environmental pollution. The mechanism of action (MOA) of SFs is respiratory inhibition of fungal mitochondria. Specifically, azoxystrobin (AZO), pyraclostrobin (PYR), trifloxystrobin (TRI), fluoxastrobin (FLUO), picoxystrobin (PICO), and kresoxim-methyl (KRE) are considered the most widely used SFs. The toxicities of those six fungicides in the environment are still unclear. The present review summarized the toxicities of the six SFs to terrestrial and aquatic biota, including mice, amphibians, aquatic organisms (fish, daphnia, algae, etc.), apoidea, soil animals (earthworms and Folsomia fimetaria), and soil microorganisms. We also review the residue, fate, and transportation of SFs. The results indicate that SFs are highly toxic to aquatic and soil organisms and pose potential risks to ecosystems. Current toxicology studies are more focused on acute or chronic toxicity, but the underlying mechanisms are still unclear and require further analysis. In addition, a simple and scientific analysis method is needed to compare the toxicity differences of different SFs to the same test organisms or differences in the same SFs to different test organisms.

Effect of Natural Aging of Biochar on Soil Enzymatic Activity and Physicochemical Properties in Long-Term Field Experiment

The effect of different rates of biochar on selected soil properties and enzymatic activity 48, 60, and 72 months after biochar application to soil was investigated. Soil enzymatic activity (dehydrogenase—ADh; phosphatase—Aph; urease—AU), the organic carbon content (TOC), the total nitrogen content (Nt), the mineral nitrogen content (NH4+, NO3−), and soil pH were determined. The study was conducted on Haplic Podzol originating from glaciofluvial fine-grained loamy sand. Biochar was applied to soil under winter rye (Secale cereale L.) at rates of 10 (BC10), 20 (BC20), and 30 t ha−1 (BC30). Plots with biochar-unamended soil were the control treatment (BC0). The pH, TOC, and Nt content in the biochar-amended soil were higher compared to the control soil. A broader C:N ratio was found in the BC0 soil compared to BC10, BC20, and BC30. With increasing biochar rate, the content of the ammonium nitrogen form (NH4+) decreased and was statistically lower than in the control soil (BC0). The soil in the BC20 and BC30 treatments was characterized by the highest content of NO3-, whereas the lowest nitrate nitrogen content was found in the control soil (BC0). Biochar application increased soil enzymatic activity. Dehydrogenase activity increased with increasing biochar rate. As far as phosphatase and urease activity is concerned, a similar relationship was not observed. In this case, the soil amended with biochar at a rate of 20 t ha−1 (BC20) was characterized by the highest phosphatase and urease activity.

Effects of rice straw biochar on sorption and desorption of di-n-butyl phthalate in different soil particle-size fractions

Sorption of organic contaminants by biochar greatly affects their bioavailability and fate in soils. Nevertheless, very little information is available regarding the effects of biochar on sorption and desorption of organic contaminants in different soil particle-size fractions. In this study, di-n-butyl phthalate (DBP), a prevalent organic contaminant in agricultural soils, was taken as a model contaminant. The effects of biochar on DBP sorption and desorption in six particle-size fractions (i.e., coarse sand, fine sand, coarse silt, fine silt, clay, and humic acid fractions) of paddy soil were investigated using batch sorption-desorption experiments. A straw-derived biochar with high specific surface area (116 m²/g) and high content of organic matter (OM) rich in aromatic carbon (67%) was prepared. Addition of this biochar (1% and 5%) significantly promoted the sorption and retention of DBP in all the paddy soil particle-size fractions at environmentally relevant DBP concentrations (2-12 mg/L) with 1.2-132-fold increase of the K_d values. With increasing addition rates of biochar, DBP retention by the biochar enhanced. The biochar's effectiveness was remarkably influenced by the physicochemical properties of the soil particle-size fractions, especially, the OM contents and pore size showed the most striking effects. A parameter (r_kd) reflecting the biochar's effectiveness showed negative and positive correlations with OM contents and pore size of the soil particle-size fractions, respectively. Accordingly, strong effect of the biochar was found in the soil fractions with low OM contents and high pore size. The findings of this study gave insight into the effects and influencing factors of biochar on sorption and desorption of organic contaminants in soils at scale of various particle-size factions.

The biochemical activity of soil contaminated with fungicides

Excess fungicides can pose a serious threat to the soil environment. Fungicides can lower the microbiological and biochemical activity of soil and lead to yield declines. Soils contaminated with fungicides have to be remediated to maintain the optimal function of soil ecosystems. This study evaluates the effect of neutralizing substances on soil enzymatic activity and the yield of Triticum aestivum L. in soil contaminated with fungicides. Sandy loam (Eutric Cambisols) with pH_KCl 7.0 was contaminated with an aqueous solution of Amistar 250 SC and Falcon 460 EC in the following doses: 0 (soil without fungicide - treated as a control), RD (dose recommended by the manufacturer) and 300 × RD (dose 300-fold higher than the recommended dose). Soil was supplemented with bentonite and basalt meal at a dose of 10 g kg^-1 DM of soil (dry mass of soil). The fungicide dose recommended by the manufacturer did not induce changes in soil enzymatic activity or the yield of T. aestivum L. Our findings indicate that the tested fungicides can be safely applied to protect crops against fungal pathogens. However, when applied at the dose of 300 × RD, the tested fungicides strongly inhibited soil enzymatic activity and disrupted the growth and development of spring wheat. Soil supplementation with bentonite and basalt meal improved the yield of T. aestivum L., and bentonite was more effective in reducing fungicide stress. The analyzed substances were not highly effective in restoring biochemical homeostasis in soil.

Effects of biochar amendment on sorption, dissipation, and uptake of fenamiphos and cadusafos nematicides in sandy soil

BACKGROUND

The application of biochar to soil is supposed to alter its adsorption/desorption potential toward pesticides, thereby affecting their bioavailability and efficacy. This is particularly relevant in the case of nematicides because these pesticides are directly applied to soil.

RESULTS

Biochar was produced from date palm (PB) and eucalyptus (EB) waste at 450 °C and added at a rate of 1% to a sandy soil. The half-life (t_½ ) of fenamiphos was increased from 2.7 to 18.3 and 18.6 days in PB- and EB-amended soils, respectively. By contrast, the half-life of cadusafos was unaffected. Freundlich K_f values increased from 1.22 and 0.39 (μg^1-Nf g^-1 mL^Nf ) to 4.49 and 6.84 in 1% PB-amended soil, and to 3.49 and 4.62 in 1% EB-amended soil for cadusafos and fenamiphos, respectively. Plant uptake of both nematicides in tomato seedlings was reduced by approximately 97% (cadusafos) and 85% (fenamiphos). Although nematicide efficacy against Meloidogyne incognita was not altered at the recommended dosage, it was negatively affected at a half-dose rate. Under these conditions, it decreased from 43.1% in unamended sandy soil to only 18.3% in 1% PB-amended soil.

CONCLUSIONS

Biochar addition increased the sorption capacity of soil. This resulted in a decrease of nematicide bioavailability, together with a reduction of both the dissipation rate and uptake by tomato plants. © 2018 Society of Chemical Industry.

The influence of chlorothalonil on the activity of soil microorganisms and enzymes

As one of the most widely used pesticides in agriculture, chlorothalonil can pose threat to soil ecosystems. Therefore, the impact of this substance on the development of microbiological and biochemical properties of the soil as well as on the growth of spring wheat was evaluated. The study was conducted with two soils (loamy sand with pH_KCl 5.6 and sandy loam with pH_KCl 7.00), to which fungicide was used in the following doses: 0.00, 0.166 (recommended dose), 1.660, and 16.60 mg kg^-1 dry matter of soil (DM of soil). In addition, we determined the effectiveness of fertilizing substances (Lignohumat Super and Bioilsa N 12.5) in the restoration of soil homeostasis and chlorothalonil degradation in the soil. Chlorothalonil caused modifications in the count and biological diversity of soil microorganisms. It stimulated the growth of heterotrophic bacteria and actinobacteria, and inhibited the growth of fungi. This pesticide was a potent inhibitor of dehydrogenase, catalase and acid phosphatase activities. It showed variable effects on urease and alkaline phosphatase. The fungicide also a reduction the yield of dry matter of the aboveground parts of spring wheat. It should, however, be noted that these changes in the soil environment occurred after the introduction of higher doses of chlorothalonil. The fertilizing substances used contributed to enhanced microbial and biochemical activities of soils, while they did not significantly affect plant yields. The Bioilsa N 12.5 preparation was effective in chlorothalonil degradation, while Lignohumat Super reduced the degradation rate of the tested fungicide. Based on the conducted experiment, an ecological risk assessment of chlorothalonil was made by estimating the changes occurring in the soil environment evaluated through the microbiological and biochemical analyses of the soil.

Evaluating the effects of phytoremediation with biochar additions on soil nitrogen mineralization enzymes and fungi

Phytoremediation with biochar addition might alleviate pollutant toxicity to soil microorganism. It is uncertain to what extent biochar addition rate could affect activities of enzymes related to soil nitrogen (N) mineralization and alter fungal community under the phytoremediation. This study aimed to reveal the effects of Medicago sativa L. (alfalfa) phytoremediation, alone or with biochar additions, on soil protease and chitinase and fungal community and link the responses of microbial parameters with biochar addition rates. The alfalfa phytoremediation enhanced soil protease activities, and relative to the phytoremediation alone, biochar additions had inconsistent impacts on the corresponding functional gene abundances. Compared with the blank control, alfalfa phytoremediation, alone or with biochar additions, increased fungal biomass and community richness estimators. Moreover, relative to the phytoremediation alone, the relative abundances of phylum Zygomycota were also increased by biochar additions. The whole soil fungal community was not significantly changed by the alfalfa phytoremediation alone, but was indeed changed by alfalfa phytoremediation with 3.0% (w/w) or 6.0% biochar addition. This study suggested that alfalfa phytoremediation could enhance N mineralization enzyme activities and that biochar addition rates affected the responses of fungal community to the alfalfa phytoremediation.

The depleted mineralization of the fungicide chlorothalonil derived from loss in soil microbial diversity

There are lack of studies regarding the effects of microbial diversity on specific soil functions, such as pesticides degradation. This study evaluated the role of bacterial community diversity and biochar on chlorothalonil (CTN) degradation, using 'dilution to extinction' approach, PCR-DGGE/16S rRNA gene technique, and radiorespirometry (14C-CTN). Biochar and microbial community dilution affected structure of the microbial community. In spite of that, CTN mineralization was slow, but dissipation was very fast (D50 < 1.0 d) due to immediate chemical degradation and formation of non-extractable (bound) residues. However, any depletion on soil microbial diversity strongly affected CTN mineralization, suggesting that this function is related to less abundant but specific microbial groups (CTN degraders) or to soil microbial diversity. The extent of these effects will strongly depend on the compound nature (recalcitrance) and soil matrix/substrate (bioavailability). It can be corroborated by the fact that biochar affected CTN sorption, its bioavailability, and subsequently its mineralization rate in the NS. These data indicate a strong relationship between soil microbial diversity and pesticide degradation, which is an acting form to mitigate xenobiotics accumulation in the environment.

Biochar Soil Additions Affect Herbicide Fate: Importance of Application Timing and Feedstock Species

Biochar (BC), solid biomass subjected to pyrolysis, can alter the fate of pesticides in soil. We investigated the effect of soil amendment with several biochars on the efficacy of two herbicides, clomazone (CMZ) and bispyribac sodium (BYP). To this aim, we evaluated CMZ and BYP sorption, persistence, and leaching in biochar-amended soil. Sorption of CMZ and BYP was greater in soil amended with BC produced at high temperature (700 °C). Significant sorption of the neutral CMZ herbicide also occurred in amended soil with BC prepared at low temperature (350 and 500 °C). For both herbicides, desorption possessed higher hysteretic behavior in soil amended with BC made at 700 °C (pyrolysis temperature). Dissipation of CMZ was enhanced after addition of BCs to soil, but no correlation between persistence and sorption was observed. Persistence of BYP was up to 3 times greater when BC made at 700 °C was added to soil. All BCs suppressed the leaching of CMZ and BYP as compared to the unamended soil. Amendment with 700 °C BC inhibited the action of CMZ against weeds, but 350 and 500 °C BCs had no such effect when added to soil. BYP activity was similar to that exhibited by unamended soil after the addition of 700 °C BC. From these results, biochar amendments can be a successful strategy to reduce the environmental impact of CMZ and BYP in soil. However, the phytotoxicity of soil-applied herbicides will depend on BC sorption characteristics and the pesticide's chemical properties, as well as the pesticide application timing (e.g., pre- or postemergence). According to our results, proper biochar screening with intended pesticides in light of the application mode (pre- or postemergence) is required prior to use to ensure adequate efficacy.

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.

Two new fatty acids esters were detected in ginseng stems by the application of azoxystrobin and the increasing of antioxidant enzyme activity and ginsenosides content

Panax ginseng C.A. Meyer is a valuable herb in China that has also gained popularity in the West because of its pharmacological properties. The constituents isolated and characterized in ginseng stems include ginsenosides, fatty acids, amino acids, volatile oils, and polysaccharides. In this study, the effects of fungicide azoxystrobin applied on antioxidant enzyme activity and ginsenosides content in ginseng stems was studied by using Panax ginseng C. A. Mey. cv. (the cultivar of Ermaya) under natural environmental conditions. The azoxystrobin formulation (25% SC) was sprayed three times on ginseng plants at different doses (150ga.i./ha and 225ga.i./ha), respectively. Two new fatty acids esters (ethyl linoleate and methyl linolenate) were firstly detected in ginseng stems by the application of azoxystrobin as foliar spray. The results indicated that activities of enzymatic antioxidants, the content of ginsenosides and two new fatty acids esters in ginseng stems in azoxystrobin-treated plants were increased. Azoxystrobin treatments to ginseng plants at all growth stages suggest that the azoxystrobin-induced delay of senescence is due to an enhanced antioxidant enzyme activity protecting the plants from harmful active oxygen species (AOS). The activity of superoxide dismutase (SOD) in azoxystrobin-treated plants was about 1-3 times higher than that in untreated plants. And the effects was more significant (P=0.05) when azoxystrobin was applied at dose of 225ga.i./ha. This work suggests that azoxystrobin plays an important role in delaying of senescence by changing physiological and biochemical indicators and increasing ginsenosides content in ginseng stems.

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.

Effect of different rates of spent mushroom substrate on the dissipation and bioavailability of cymoxanil and tebuconazole in an agricultural soil

Physicochemical methods to immobilize pesticides in vulnerable soils are currently being developed to prevent water contamination. Some of these methods include the use of different organic residues to modify soils because they could limit the transport of pesticides and/or facilitate their dissipation. Spent mushroom substrate (SMS) may be used for these purposes. Accordingly a study was conducted under laboratory conditions to know the dissipation and bioavailability of the fungicides cymoxanil and tebuconazole over time in a vineyard soil amended with two rates of spent mushroom substrate (SMS) (5% and 50% (w/w)), selected to prevent the diffuse or point pollution of soil. The dissipation of cymoxanil was more rapid than that of tebuconazole in the different soils studied. The dissipation rate was higher in the amended soil than in the unamended one for both compounds, while no significant differences were observed between the amended soils in either case. An apparent dissipation occurred in the amended soil due to the formation of non-extractable residues. Bound residues increased with incubation time for tebuconazole, although a proportion of this fungicide was bioavailable after 303days. The major proportion of cymoxanil was tightly bound to the amended soil from the start, although an increasing fraction of bound fungicide was bioavailable for mineralization. Soil dehydrogenase activity was significantly affected by SMS application and incubation time; however, it was not significantly modified by fungicide application. The significance of this research suggests that SMS applied at a low or high rate to agricultural soil can be used to prevent both the diffuse or point pollution of soil through the formation of non-extractable residues, although more research is needed to discover the time that fungicides remain adsorbed into the soil decreasing either bioavailability (tebuconazole) or mineralization (cymoxanil) in SMS-amended soils.

Agronomic and remedial benefits and risks of applying biochar to soil: Current knowledge and future research directions

'Biochar' represents an emerging technology that is increasingly being recognized for its potential role in carbon sequestration, reducing greenhouse gas emissions, waste management, renewable energy, soil improvement, crop productivity enhancement and environmental remediation. Published reviews have so far focused mainly on the above listed agronomic and environmental benefits of applying biochar, yet paid little or no attention to its harmful effects on the ecological system. This review highlights a balanced overview of the advantages and disadvantages of the pyrolysis process of biochar production, end-product quality and the benefits versus drawbacks of biochar on: (a) soil geochemistry and albedo, (b) microflora and fauna, (c) agrochemicals, (d) greenhouse gas efflux, (e) nutrients, (f) crop yield, and (g) contaminants (organic and inorganic). Future research should focus more on the unintended long-term consequences of biochar on biological organisms and their processes in the soil.

Application of mesotrione at different doses in an amended soil: Dissipation and effect on the soil microbial biomass and activity

The aim of this work was to estimate the dissipation of mesotrione applied at three doses (2, 10 and 50 mg kg(-1) dw) in an unamended agricultural soil, and this same soil amended with two organic residues (green compost (C) and sewage sludge (SS)). The effects of herbicide and organic residue on the abundance and activity of soil microbial communities were also assessed by determining soil microbial parameters such as biomass, dehydrogenase activity (DHA), and respiration. Lower dissipation rates were observed for a higher herbicide dose. The highest half-life (DT50) values were observed in the SS-amended soil for the three herbicide doses applied. Biomass values increased in the amended soils compared to the unamended one in all the cases studied, and increased over the incubation period in the SS-amended soil. DHA mean values significantly decreased in the SS-amended soil, and increased in the C-amended soil compared to the unamended ones, under all conditions. At time 0 days, respiration values were significantly higher in SS-amended soils (untreated and treated with mesotrione) than in the unamended and C-amended soils. The effect of mesotrione on soil biomass, DHA and respiration was different depending on incubation time and soil amendment and herbicide dose applied. The results support the need to consider the possible non-target effects of pesticides and organic amendments simultaneously applied on soil microbial communities to prevent negative impacts on soil quality.

Field versus laboratory experiments to evaluate the fate of azoxystrobin in an amended vineyard soil

This study reports the effect that adding spent mushroom substrate (SMS) to a representative vineyard soil from La Rioja region (Spain) has on the behaviour of azoxystrobin in two different environmental scenarios. Field dissipation experiments were conducted on experimental plots amended at rates of 50 and 150 t ha(-1), and similar dissipation experiments were simultaneously conducted in the laboratory to identify differences under controlled conditions. Azoxystrobin dissipation followed biphasic kinetics in both scenarios, although the initial dissipation phase was much faster in the field than in the laboratory experiments, and the half-life (DT50) values obtained in the two experiments were 0.34-46.3 days and 89.2-148 days, respectively. Fungicide residues in the soil profile increased in the SMS amended soil and they were much higher in the top two layers (0-20 cm) than in deeper layers. The persistence of fungicide in the soil profile is consistent with changes in azoxystrobin adsorption by unamended and amended soils over time. Changes in the dehydrogenase activity (DHA) of soils under different treatments assayed in the field and in the laboratory indicated that SMS and the fungicide had a stimulatory effect on soil DHA. The results reveal that the laboratory studies usually reported in the literature to explain the fate of pesticides in amended soils are insufficient to explain azoxystrobin behaviour under real conditions. Field studies are necessary to set up efficient applications of SMS and fungicide, with a view to preventing the possible risk of water contamination.

Endogenous minerals have influences on surface electrochemistry and ion exchange properties of biochar

The feedstocks for biochar production are diverse and many of them contain various minerals in addition to being rich in carbon. Twelve types of biomass classified into 2 categories: plant-based and municipal waste, were employed to produce biochars under 350 °C and 500 °C. Their pH, point of zero net charge (PZNC), zeta potential, cation and anion exchange capacity (CEC and AEC) were analyzed. The municipal waste-based biochars (MW-BC) had higher mineral levels than the plant-based biochars (PB-BC). However, the water soluble mineral levels were lower in the MW-BCs due to the dominant presence of less soluble minerals, such as CaCO3 and (Ca,Mg)3(PO4)2. The higher total minerals in MW-BCs accounted for the higher PZNC (5.47-9.95) than in PB-BCs (1.91-8.18), though the PZNCs of the PB-BCs increased more than that of the MW-BCs as the production temperature rose. The minerals had influence on the zeta potentials via affecting the negative charges of biochars and the ionic strength of solution. The organic functional groups in PB-BCs such as -COOH and -OH had a greater effect on the CEC and AEC, while the minerals had a greater effect on that of MW-BCs. The measured CEC and AEC values had a strong positive correlation with the total amount of soluble cations and anions, respectively. Results indicated that biochar surface charges depend not only on the organic functional groups, but also on the minerals present and to some extent, minerals have more influences on the surface electrochemistry and ion exchange properties of biochar.

Application of Rice-Straw Biochar and Microorganisms in Nonylphenol Remediation: Adsorption-Biodegradation Coupling Relationship and Mechanism

Biochar adsorption presents a potential remediation method for the control of hydrophobic organic compounds (HOCs) pollution in the environment. It has been found that HOCs bound on biochar become less bioavailable, so speculations have been proposed that HOCs will persist for longer half-life periods in biochar-amended soil/sediment. To investigate how biochar application affects coupled adsorption-biodegradation, nonylphenol was selected as the target contaminant, and biochar derived from rice straw was applied as the adsorbent. The results showed that there was an optimal dosage of biochar in the presence of both adsorption and biodegradation for a given nonylphenol concentration, thus allowing the transformation of nonylphenol to be optimized. Approximately 47.6% of the nonylphenol was biodegraded in two days when 0.005 g biochar was added to 50 mg/L of nonylphenol, which was 125% higher than the relative quantity biodegraded without biochar, though the resistant desorption component of nonylphenol reached 87.1%. All adsorptive forms of nonylphenol (f_rap, f_slow, f_r) decreased gradually during the biodegradation experiment, and the resistant desorption fraction of nonylphenol (f_r) on biochar could also be biodegraded. It was concluded that an appropriate amount of biochar could stimulate biodegradation, not only illustrating that the dosage of biochar had an enormous influence on the half-life periods of HOCs but also alleviating concerns that enhanced HOCs binding by biochar may cause secondary pollution in biochar-modified environment.

Biochar efficiency in pesticides sorption as a function of production variables--a review

Biochar is a stabilized, carbon-rich by-product derived from pyrolysis of biomass. Recently, biochar has received extensive attentions because of its multi-functionality for agricultural and environmental applications. Biochar can contribute to sequestration of atmosphere carbon, improvement of soils quality, and mitigation of environmental contaminations. The capability of biochar for specific application is determined by its properties which are predominantly controlled by source material and pyrolysis route variables. The biochar sorption potential is a function of its surface area, pores volume, ash contents, and functional groups. The impacts of each production factors on these characteristics of biochar need to be well-understood to design efficient biochars for pesticides removal. The effects of biomass type on biochar sorptive properties are determined by relative amounts of its lingo-cellulosic compounds, minerals content, particles size, and structure. The highest treatment temperature is the most effective pyrolysis factor in the determination of biochar sorption behavior. The expansion of micro-porosity and surface area and also increase of biochar organic carbon content and hydrophobicity mostly happen by pyrolysis peak temperature rise. These changes make biochar suitable for immobilization of organic contaminants. Heating rate, gas pressure, and reaction retention time after the pyrolysis temperatures are sequentially important pyrolysis variables effective on biochar sorptive properties. This review compiles the available knowledge about the impacts of production variables on biochars sorptive properties and discusses the aging process as the main factor in post-pyrolysis alterations of biochars sorption capacity. The drawbacks of biochar application in the environment are summarized as well in the last section.