Study on nitrile-degrading microorganisms

Two strains of bacteria were isolated from nitrile polluted soils, and identified as Corynebacterium boffmanii and Arthrobacter flavescens. Acetonitrile, propionitrile, butyronitrile and acrylonitrile were degraded by these bacteria to yield corresponding amides, carboxylic acids and ammonia. The nitrile-degrading abilities of these strains were investigated. The removal rates for the nitrile were nearly 100%, after these bacteria were grown in medium containing 10000 ppm of aceto-, propio-, or butyronitrile at 28 ℃ for 24h. When the reaction mkture consisting of 5000 ppm of above mentioned nitriles or acrylonitrile and 20g (dry cell) /L resting cells of the two strains in 0.06mol/L phosphate buffer (pH7.5) was incubated separately at 25 ℃ with moderate shaking for 15 or 45 min, the nitrile could be degraded completely. The optimum growth conditions for C.hoffmanii and A.flavescens were studied as well.

Study on Prediction of Pesticide Residues Based on Fuzzy System

This study was aimed to do the prediction of pesticide residues based on fuzzy system. Taking chlorpyrifos as an example, the Mathematic Fuzzy System was established by using the MRL values （maximum residue limits of all kinds of pesticides in food） of the Matlab Fuzzy Toolbox to analyze and predict the degra- dation degree of pesticide residues of the same crop at different time periods of bagging treatment, with the aim to provide some theoretical guidances for solving practical problems in real life.

Organochlorine pesticides in soils under different land usage in the Taihu Lake region, China

A field study was conducted in the Taihu Lake region, China in 2004 to reveal the organochlorine pesticide concentrations in soils after the ban of these substances in the year 1983. Thirteen organochlorine pesticides （OCPs） were analyzed in soils from paddy field, tree land and fallow land. Total organochlorine pesticide residues were higher in agricultural soils than in uncultivated fallow land soils. Among all the pesticides, ΣDDX （DDD, DDE and DDT） had the highest concentration for all the soil samples, ranging from 3.10 ng/g to 166.55 ng/g with a mean value of 57.04 ng/g and followed by ΣHCH, ranging from 0.73 ng/g to 60.97 ng/g with a mean value of 24.06 ng/g. Dieldrin, endrin, HCB and α-endosulfan were also found in soils with less than 15 ng/g. Ratios of p,p＇-（DDD＋DDE）/DDT in soils under three land usages were： paddy field 〉 tree land 〉 fallow land, indicating that land usage inlfuenced the degradation of DDT in soils. Ratios of p,p＇-（DDD＋DDE）/DDT 〉1, showing aged residues of DDTs in soils of the Taihu Lake region. The results were discussed with data from a former study that showed very low actual concentrations of HCH and DDT in soils in the Taihu Lake region, but according to the chemical half-lives and their concentrations in soils in 1980s, the concentration of DDT in soils seemed to be underestimated. In any case our data show that the ban on the use of HCH and DDT resulted in a tremendous reduction of these pesticide residues in soils, but there are still high amounts of pesticide residues in soils, which need more remediation processes.

Sonochemical degradation of organophosphorus pesticide in dilute aqueous solutions

Ultrasonic irradiation was found to accelerate the rate of hydrolysis of omethoate in aqueous solution over the pH range of 2—12 Process parameters studied include pH, steady state temperature, concentration, and the type of gases. Greater than 96% hydrolysis was observed in 30 minutes through this process and the rate of destruction increased with the help of more soluble and low thermal inert gas. So with Krypton, omethoate was found to undergo rapid destruction as compared with Argon. In the presence of ultrasound, the observed first order rate of hydrolysis of omethoate is found to be independent of pH. The formation of transient supercritical water(SCW) appears to be an important factor in the acceleration of chemical reactions in the presence of ultrasound. A detailed chemical reaction mechanism for omethoate destruction in water was formulated. Experimental results and theoretical kinetic mechanism demonstrated that the most of the omethoate undergo destruction inside the cavitating holes. A very less effect of temperature on the degradation of omethoate within a temperature range of 20—70℃ proves that a small quantity of omethoate undergoes secondary destruction in the bulk liquid.

Degradation of Extraction from Seaweed and Its Complex with Rare Earths for Organophosphorous Pesticides

On the basis of several experiments carried out in China, it was proved that both seaweed liquid fertilizer and rare earth （RE） could promote the growth of crops and increase their yield. The effects of extraction from seaweed and its complex with RE on the degradation of organophosphorous pesticides and the yield of vegetables were investigated. The resuits showed that the extract and its complex with RE could degrade organophosphorous pesticides in neutral solvent. The residues of the pesticides treated by the extract decreased by 96.88 %, 52.30%, 49.52%, and 22.88 %, respectively, for chlorpyrifos, dichlorvos, omethoate, and dimethoate, and those by the complex decreased by 95.99%, 54.23%, 48.79%, and 25.66%, respectively, when compared with the control. The residues of chlorpyrifos and dimethoate in spinach sprayed with the complex were decreased by 90.64% and 76.56%, respectively, compared with those in spinach from control plots when the interval between spraying and sampling was 8 d. The fresh weight of brassica chinensis and cabbage increased by 28.62% and 18.72%, and their dry weight increased by 44.49% and 14.74%, respectively, compared with those of the controls. The chlorpyrifos and dimethoate residues in brasscia chinese were decreased by 36.36% and 50.00%, respectively, and their rate of decrease in cabbage was 40.00% and 75.00%, respectively, on 5th day after spraying with the complex, when compared with those in the vegetable from control. These results suggest that this complex can increase the agricultural productivity and reduce the use of pesticide residues in the production of vegetables.

Photocatalytic Degradation of Isoproturon Pesticide on C, N and S Doped TiO2

TiO2 doped with C, N and S (TCNS photocatalyst) was prepared by hydrolysis process using titanium iso-propoxide and thiourea. The prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photo electron spectroscopy (XPS), BET surface area, FTIR and diffuse reflectance spectra (DRS). The results showed that the prepared catalysts are anatase type and nanosized par-ticles. The catalysts exhibited stronger absorption in the visible light region with a red shift in the adsorption edge. The photocatalytic activity of TCNS photocatalysts was evaluated by the photocatalytic degradation of isoproturon pesticide in aqueous solution. In the present study the maximum activity was achieved for TCNS5 catalyst at neutral pH with 1 g L-1 catalyst amount and at 1.14 x 10-4 M concentration of the pesticide solution. The TCNS photocatalysts showed higher phtocatalytic activity under solar light irradiation. This is attributed to the synergetic effects of red shift in the absorption edge, higher surface area and the inhibition of charge carrier recombination process.

Hydrolytic dynamics of pesticide N＇－（2，4－dimethylphenyl）－N－methylformamidine in aquatic solution

The hydrolytic dynamics of pesticide N' -(2,4-dimethylphenyl)-N-methylformamidine (DMA) in aquatic solution and its degradation in simulated aquatic ecosystem were investigated. The results showed that the compound was not very stable in aqueous solution and easily decomposed in alkaline solution. It was stable below pH5 and there was obvious tendency that the compound was easily decomposed when PH was greater than 6. The reaction rate constant of DMA increased with increasing of either pH value Or temperature of reaction medium. The half-life values of hydrolysis for DMA at 25℃ were 15. 92 days at pH 6, and 1. 40 days at pH 9 , respectively. The temperature coefficient and activation energy of hydrolysis for DMA was 2. 9 and 78. 74kJ. mol-1 , respectively. The degradation of DMA in simulated aquatic ecosystem was similar to that in buffer solution in the laboratory. The half-life values of degradation for DMA at 26℃ in simulated aquatic ecosystem were 3. 23 days at pH 9. 13 and 1. 41 days at pH 8. 28 , respectively.

A Unified Model for the Degradation Kinetics of Pesticides Applied Continually to Soils

This paper deduces a kinetic model for microbial degradation of pesticides in soils:where x is the concentration of pesticide at time t, so the initial concentration of the pesticide, me the initial number of pesticide-degrading microorganisms, M the carrying capacity for the microorganisms, μ the specific growth rate of the microorganisms, and k the rate constant for the pesticide degradation.In periodic applications of pesticides, this model can be used to continuously describe every degradation curve. Whether a lag phase occurs or not, we can obtain the minimum residue of the pesticide (xe):xe=xdexp(-kMr)/[1-exp(-ker) ]where r is the regular time internals between applications, and xd the dosage of the pesticide.

The degradation of organophosphorus pesticides by means of sodium percarbonate

The factors and mechanisms of oxidative degradation of three organophosphorus pesticides （dichlorvos, methamidophos and phoxim） were studied with sodium percarbonate （SPC） as a solid oxidant. The result showed that SPC has highly activity in degrading these organophosphous pesticides. The most efficient degradation of pesticides occurred under basic conditions and the degradation rates increased with time extension and high temperature. The degradation of organophosphorus pesticides was expected to get even better results at lower initial concentration. Furthermore, we analyzed the intermediate products by NMP, spectrometry. On the basis of the analytical result, the oxidative degradation mechanism was proposed for each organophosphous pesticide. It is significant to understand the environment chemistry of organophosphorus pesticides in environmental system.

Pressure Hydrolysis for Degradation of Omethoate Pesticide in Water

The effect of pressure on the hydrolysis rates and the degradation kinetics of environmentally persistent omethoate pesticide was studied. The results showed that the values of k obs increased and the values of activation volume (AV) decreased with increasing pressure. Among pH conditions (3.58, 6.01 and 8.5), pH 8. 5 was found to be the unstable condition and its half-life was reduced from 263 min at 1 atm to 19.37 min at 10 atm. These results describe that high-pressure hydrolysis is a useful technique for the conversion of toxic organic phosphorus into inorganic phosphorus. Key words pressure hydrolysis - organophosphorus pesticide - degradation

Sequential Remediation Processes for a Low Level Pesticide Wastewater

The aim of this study was to develop a remediation system for the treatment of a low-level pesticide wastewater that uses available onfarm organic matter as an absorption media, is capable of reducing the concentration of the pesticide to a safe level and is economically viable for implementation by farmers. The absorption capacity of chopped hay and soybean to the fungicide captan was evaluated under batch conditions and the effectiveness of the composting process in depredating captan in contaminated organic materials was evaluated. The results showed that both hay and soybean plant residues were very effective in absorbing 99.2% and 98.5% of captan form the wastewater after 4 hours, respectively. Because of its availability, hay can be used in an onfarm pesticide immobilization system that consists of shallow reinforced concrete pit (filled with hay) with steel bars across the top for machinery to roll onto and be washed. The wastewater can be retained for 24 hours which is a sufficient time for hay to absorb the captan. The contaminated hay can then be composted. The addition of used cooking oil raised the temperature of the composting mixture to 63?C. Small reductions in moisture content (from 60% to 58.9 %) and C:N ratio (from 30:1 to 28:1) were observed while reductions of 18.92%, 15.56% and 4.8% in the volatile solids, total carbon total Kjeldahl nitrogen were achieved after 10 d of composting, respectively. About 92.4% of the captan was degraded in the first 4 days of composting. Most of captan (92.4%) was degraded during the mesophilic stage (first 3 days). The degradation rate constant for the mesophilic stage (0.724 d-1) was 2.74 times the degradation rate constant for the thermophilic stage (0.264 d-1). An onfarm windrow composting process would be very effective in degrading captan contaminated hay. The captan contaminated hay could be mixed with equal amount poultry manure or dairy manure to provide the required bioavailable carbon and nutrients for the composting process. Some used cooking oil could also be added to maintain higher temperature within the compost matrix. The windrows should be mixed on a daily basis to provide sufficient oxygen for the composting microorganisms.

Recent Advances in Degradation of Organophosphorus Pesticides

With the growing demand for environmental protection and physical health,food safety is now receiving more and more attention all over the world.However,pesticides are indispensable in agricultural production.Therefore,how to efficiently degrade pesticides and remove their residues in foods has always been a hot research topic in recent decades.This paper not only summarizes the types,degradation mechanism and artificial degradation of organophosphorus pesticides,but also highlights the latest advances in chemical degradation,photocatalytic degradation and biodegradation.

Research on Pesticide Residues of Cypermethrin in Lettuce

In order to find the effective method to reduce pesticide residues in vegetables, and promote the healthy development of vegetable industry. The paper used chlorothalonil, fenvalerate, dimethoate widely used pesticides as experimental material, using GC method to measure residual dynamics of vegetable pesticide. The results show that： fenvalerate, dimethoate, chlorothalonil pesticide residues in lettuce was higher than that tomato in the application day, respectively reach at 42.9%, 44.9%, 57.8%, pesticide degradation rate in open land were significantly higher than those in greenhouse within 5-20 days. The test showed that： the degradation of pesticide amount is in 8.77%r-19.64% within 1 days. The initial concentration of pesticides on vegetables are relevant with surface area of vegetable edible parts; the degradation speed of pesticide degradation rate in greenhouse vegetable is obviously slower than the open field vegetable; pesticide deposition phenomenon is an important factor affecting the pesticide residues in greenhouse.

Investigation on Microorganisms and their Degradation Efficiency in Paper and Pulp Mill Effluent

Paper and pulp mill is a source of major pollution generating industry leaving huge amount of intensely colored effluent to the receiving end. Rapid increase of population and the increased demand for industrial establishments to meet human needs have created problems such as over exploitation of available resources, increased pollution taking place on land, air and water environment. The intention of this research paper is to identify predominant bacteria and fungi in paper and pulp mill effluent in addition to evaluate the degradation efficiency of individual isolates and combination of isolates. Treatment efficiency of individual isolates and combination of isolates are evaluated by shake flask method. Combination of Pseudomonas Alkaligenes, Bacillus subtilis along with Trichoderma reesei shows higher BOD, COD reduction of 99% and 85% respectively. As individual isolates Pseudomonas Alkaligenes show 92% BOD reduction and 77% COD reduction over other bacterial isolates and Trichoderma reesei removed 99% BOD and 80% COD respectively.

Remediation of amide pesticide-polluted soils by combined solarization and ozonation treatment

Agriculture has a close relationship with nature,but it can also be the source of negative and permanent environmental effects.The use of pesticides in modern agriculture is a common practice,but their side effects on the environment cannot be disregarded.In this study,we evaluated a combination of solarization and ozonation techniques for the elimination of six amide pesticides(boscalid,chlorantraniliprole,cyflufenamid,fluopyram,napropamide,and propyzamide)in soil.Initial experiments were performed with four different soils to assess the efficiency of this methodology at different soil temperatures and ozone dosages under laboratory conditions,and then a greenhouse pot experiment was conducted under controlled conditions during summer.Fifty days after the onset of the experiments,higher degradation percentages of amide pesticides were observed in ozonized soils than in other treated soils,particularly when ozone was applied at 10 cm soil depth.The results show that the utilization of ozonation,along with solarization,represents a valid method for degrading residues of the studied pesticides and suggest that this combined technology may be a promising tool for remediating pesticide-polluted soils.

Widespread and active piezotolerant microorganisms mediate phenolic compound degradation under high hydrostatic pressure in hadal trenches

Phenolic compounds,as well as other aromatic compounds,have been reported to be abundant in hadal trenches.Although high-throughput sequencing studies have hinted at the potential of hadal microbes to degrade these compounds,direct microbiological,genetic and biochemical evidence under in situ pressures remain absent.Here,a microbial consortium and a pure culture of Pseudomonas,newly isolated from Mariana Trench sediments,efficiently degraded phenol under pressures up to 70 and 60 MPa,respectively,with concomitant increase in biomass.By analyzing a high-pressure(70 MPa)culture metatranscriptome,not only was the entire range of metabolic processes under high pressure generated,but also genes encod-ing complete phenol degradation via ortho-and meta-cleavage pathways were revealed.The isolate of Pseudomonas also contained genes encoding the complete degradation pathway.Six transcribed genes(dmpKLMNOP_(sed))were functionally identified to encode a multicomponent hydroxylase catalyzing the hydroxylation of phenol and its methylated derivatives by heterogeneous expression.In addition,key catabolic genes identified in the metatranscriptome of the high-pressure cultures and genomes of bacterial isolates were found to be all widely distributed in 22 published hadal microbial metagenomes.At microbiological,genetic,bioinformatics,and biochemical levels,this study found that microorganisms widely found in hadal trenches were able to effectively drive phenolic compound degradation under high hydrostatic pressures.This information will bridge a knowledge gap concerning the microbial aromatics degradation within hadal trenches.

A Degradable Quaternary Ammonium-Based Pesticide Safe for Humans

Reducing the emission of agrochemicals hazardous to the environment and human health is one of the key targets of the UN’s Sustainable Development Goal 12.Herein,we report a kind of quaternary ammonium pesticides with an acid-cleavable silaketal linkage on their backbones that enables control of hydrolysis.These pesticides possess outstanding bactericidal and insecticidal properties but become harmless to humans and other organisms after hydrolysis.Depending on the conditions of use,the hydrolytic process can be controlled over the time range of 10 min to 3 months.Both laboratory simulations and agricultural field demonstrations confirm that these pesticides can effectively protect crops from bacterial diseases and pests.At the sametime,single-dose intragastric administration using diisopropylsilyloxy bisquaternary ammonium salt 9(ISBQAS-9)in mice demonstrates its safety for multiple organs.Owing to the advantages of controllable degradability,environmental friendliness,and the low financial cost of these pesticides,this welldesigned strategy holds great promise for the generation of environmentally harmless pesticides and the development of green agriculture.

Degradation strategies of pesticide residue:From chemicals tosynthetic biology

The past 50 years have witnessed a massive expansion in the demand and application of pesticides.However,pesticides are difficult to be completely degraded without intervention hence the pesticide residue could pose a persistent threat to non-target organisms in many aspects.To aim at the problem of the abuse of pesticide products and excessive pesticide residues in the environment,chemical and biological degradation methods are widely developed but are scaled and insufficient to solve such a pollution.In recent years,bio-degradative tools instructed by synthetic biological principles have been further studied and have paved a way for pesticide degradation.Combining the customized design strategy and standardized assembly mode,the engineering bacteria for multi-dimensional degradation has become an effective tool for pesticide residue degradation.This review introduces the mechanisms and hazards of different pesticides,summarizes the methods applied in the degradation of pesticide residues,and discusses the advantages,applications,and prospects of synthetic biology in degrading pesticide residues.

Toxic effects of pesticides on the marine microalga Skeletonema costatum and their biological degradation

Pesticides are considered to be toxic pollutants that are harmful to the health of humans and animals or dangerous to the environment.The pesticides chlorpyrifos,acetochlor,and dicofol,representatives of organophosphorus,acyl amide,and organochlorine pesticides,are widely used in agriculture and have been frequently detected in aquatic environments.However,the toxicity of these pesticides to marine microbes is unclear.In this study,the toxic effects of the three pesticides on a representative marine microalga,the diatom Skeletonema costatum(S.costatum),were investigated.Microalgal cell density and chlorophyll-a(Chl-a)content were analyzed to investigate the toxic effects after S.costatum was exposed to the three pesticides both individually and in combination.The N/P ratio in the culture medium and the degradation of the pesticides were also analyzed during exposure.Individual acute toxicity analysis indicated that the growth of S.costatum was significantly inhibited by acetochlor,followed by the effect of dicofol and chlorpyrifos.The cell membrane of the microalgae was impaired by acetochlor.Combined toxicity analysis indicated that the presence of acetochlor increased the toxicity of dicofol and chlorpyrifos.In contrast,the presence of dicofol reduced the toxicity of acetochlor and chlorpyrifos.The N/P ratio in the culture medium was largely increased at late growth stages;however,it was significantly lowered when the microalgae were exposed to chlorpyrifos compared to acetochlor and dicofol.The degradation of the pesticides was promoted by microalgae,suggesting that microalgae might contribute to the removal of these pesticides from the marine environment.The toxic mechanism of the pesticides on the marine microalgae and the fates of pesticides in the ocean need to be further studied.

A comprehensive review on semiconductor-based photocatalysts toward the degradation of persistent pesticides

Pesticides refer to the chemicals to regulate plant growth and control pests used in agriculture.However,the extensive use of pesticides causes serious pollution that threatens the ecological environment and human health.Photocatalytic degradation of pesticides has become a promising way to deal with pesticide pollution.In this review,pesticides are classified according to the different targets and chemical structures.The recent developments on semiconductor-based photocatalysts including metal oxides,metal oxyhalides,carbon nitrides,metal sulfides were reviewed for degradation of pesticides.Importantly,several modification strategies to improve the photocatalytic performance are described such as doping,heterojunction construction,defect engineering,with special emphasis on anchoring single atom catalyst.Moreover,extensive efforts should be made to indepth understand the photodegradation mechanism by monitoring key intermediates.Our perspectives on the key challenges and future directions of developing high-performance semiconductor-based photocatalysts for pesticide degradation are elaborated.